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Sample records for two-photon absorption characterization

  1. Conjugated polymers with pyrrole as the conjugated bridge: synthesis, characterization, and two-photon absorption properties.

    Science.gov (United States)

    Li, Qianqian; Zhong, Cheng; Huang, Jing; Huang, Zhenli; Pei, Zhiguo; Liu, Jun; Qin, Jingui; Li, Zhen

    2011-07-14

    The synthesis, one- and two-photon absorption (2PA) and emission properties of two novel pyrrole-based conjugated polymers (P1 and P2) are reported. They emitted strong yellow-green and orange fluorescence with fluorescent quantum yields (Φ) of 46 and 33%, respectively. Their maximal 2PA cross sections (δ) measured by the two-photon-induced fluorescence method using femtosecond laser pulses in THF were 2392 and 1938 GM per repeating unit, respectively, indicating that the 2PA chromophores consisting of the triphenylamine with nonplanar structure as the donor and electron-rich pyrrole as the conjugated bridge could be the effective repeating units to enhance the δ values.

  2. Characterization of Photon-Counting Detector Responsivity for Non-Linear Two-Photon Absorption Process

    Science.gov (United States)

    Sburlan, S. E.; Farr, W. H.

    2011-01-01

    Sub-band absorption at 1550 nm has been demonstrated and characterized on silicon Geiger mode detectors which normally would be expected to have no response at this wavelength. We compare responsivity measurements to singlephoton absorption for wavelengths slightly above the bandgap wavelength of silicon (approx. 1100 microns). One application for this low efficiency sub-band absorption is in deep space optical communication systems where it is desirable to track a 1030 nm uplink beacon on the same flight terminal detector array that monitors a 1550 nm downlink signal for pointingcontrol. The currently observed absorption at 1550 nm provides 60-70 dB of isolation compared to the response at 1064 nm, which is desirable to avoid saturation of the detector by scattered light from the downlink laser.

  3. Characterization of Photon-Counting Detector Responsivity for Non-Linear Two-Photon Absorption Process

    Science.gov (United States)

    Sburlan, S. E.; Farr, W. H.

    2011-01-01

    Sub-band absorption at 1550 nm has been demonstrated and characterized on silicon Geiger mode detectors which normally would be expected to have no response at this wavelength. We compare responsivity measurements to singlephoton absorption for wavelengths slightly above the bandgap wavelength of silicon (approx. 1100 microns). One application for this low efficiency sub-band absorption is in deep space optical communication systems where it is desirable to track a 1030 nm uplink beacon on the same flight terminal detector array that monitors a 1550 nm downlink signal for pointingcontrol. The currently observed absorption at 1550 nm provides 60-70 dB of isolation compared to the response at 1064 nm, which is desirable to avoid saturation of the detector by scattered light from the downlink laser.

  4. Two-photon absorption in arsenic sulfide glasses

    Science.gov (United States)

    Chunaev, D. S.; Snopatin, G. E.; Plotnichenko, V. G.; Karasik, A. Ya.

    2016-10-01

    The two-photon absorption coefficient of 1047-{\\text{nm}} light in {\\text{As}}35{\\text{S}}65 chalcogenide glass has been measured. CW probe radiation has been used to observe the linear absorption in glass induced by two-photon excitation. The induced absorption lifetime was found to be ∼ 2 {\\text{ms}}.

  5. Two-Photon Absorption of Metal-Assisted Chromophores.

    Science.gov (United States)

    Li, Xin; Rinkevicius, Zilvinas; Ågren, Hans

    2014-12-09

    Aiming to understand the effect of a metal surface on nonlinear optical properties and the combined effects of surface and solvent environments on such properties, we present a multiscale response theory study, integrated with dynamics of the two-photon absorption of 4-nitro-4'-amino-trans-stilbene physisorbed on noble metal surfaces, considering two such surfaces, Ag(111) and Au(111), and two solvents, cyclohexane and water, as cases for demonstration. A few conclusions of general character could be drawn: While the geometrical change of the chromophore induced by the environment was found to notably alter (diminish) the two-photon absorption cross section in the polar medium, the effects of the metal surface and solvent on the electronic structure of the chromophore surpasses the geometrical effects and leads to a considerably enhanced two-photon absorption cross section in the polar solvent. This enhancement of two-photon absorption arises essentially from the metal charge image induced enlargement of the difference between the dipole moment of the excited state and the ground state. The orientation-dependence of the two-photon absorption is found to connect with the lateral rotation of the chromophore, where the two-photon absorption reaches its maximum when the polarization of the incident light coincides with the long-axis of the chromophore. Our results demonstrate a distinct enhancement of the two-photon absorption by a metal surface and a polar medium and envisage the employment of metal-chromophore composite materials for future development of nonlinear optical materials with desirable properties.

  6. 3D knife-edge characterization of two-photon absorption volume in silicon for integrated circuit testing.

    Science.gov (United States)

    Shao, K; Morisset, A; Pouget, V; Faraud, E; Larue, C; Lewis, D; McMorrow, D

    2011-11-01

    We have performed three-dimensional characterization of the TPA effective laser spot size in silicon using an integrated knife-edge sensor. The TPA-induced response of a CMOS integrated circuit is analyzed based on these results and compared to simulation; we have found that the charge injection capacity in IC's active layer could be influenced by irradiance energy and focus depth.

  7. A fluorescent benzothiazole probe with efficient two-photon absorption

    Science.gov (United States)

    Echevarria, Lorenzo; Moreno, Iván; Camacho, José; Salazar, Mary Carmen; Hernández, Antonio

    2012-11-01

    In this work, we report the two-photon absorption of 2-[4-(dimethylamino)phenyl]-1,3-benzothiazole-6-carbonitrile (DBC) in DMSO solution pumping at 779 nm with a 10 ns pulse laser-Nd:YAG system. The obtained two-photon absorption cross-section in DBC (407 ± 18 GM) is considerably high. Because DBC is a novel compound and have high values of fluorescence quantum yield, this result is expected to have an impact in biomolecules detection, diagnosis and treatment of cancer. Similar structures have previously been reported to show remarkable antitumour effects.

  8. Nonlinear quantitative photoacoustic tomography with two-photon absorption

    CERN Document Server

    Ren, Kui

    2016-01-01

    Two-photon photoacoustic tomography (TP-PAT) is a non-invasive optical molecular imaging modality that aims at inferring two-photon absorption property of heterogeneous media from photoacoustic measurements. In this work, we analyze an inverse problem in quantitative TP-PAT where we intend to reconstruct optical coefficients in a semilinear elliptic PDE, the mathematical model for the propagation of near infra-red photons in tissue-like optical media with two-photon absorption, from the internal absorbed energy data. We derive uniqueness and stability results on the reconstructions of single and multiple optical coefficients, and present some numerical reconstruction results based on synthetic data to complement the theoretical analysis.

  9. Enhanced two-photon absorption using true thermal light

    CERN Document Server

    Jechow, Andreas; Kurzke, Henning; Heuer, Axel; Menzel, Ralf

    2013-01-01

    Two-photon excited fluorescence (TPEF) is a standard technique in modern microscopy but still affected by photo-damage of the probe. It was proposed that TPEF can be enhanced by using entangled photons, but has proven to be challenging. Recently it was shown that some features of entangled photons can be mimicked with thermal light, which finds application in ghost imaging, sub-wavelength lithography and metrology. Here, we utilize true thermal light from a super-luminescence diode to demonstrate enhanced TPEF compared to coherent light using two common fluorophores and luminescent quantum dots. We find that the two-photon absorption rate is directly proportional to the measured degree of second-order coherence, as predicted by theory. Our results show that photon bunching can be exploited in two-photon microscopy with the photon statistic providing a new degree of freedom.

  10. Two-Photon-Absorption Scheme for Optical Beam Tracking

    Science.gov (United States)

    Ortiz, Gerardo G.; Farr, William H.

    2011-01-01

    A new optical beam tracking approach for free-space optical communication links using two-photon absorption (TPA) in a high-bandgap detector material was demonstrated. This tracking scheme is part of the canonical architecture described in the preceding article. TPA is used to track a long-wavelength transmit laser while direct absorption on the same sensor simultaneously tracks a shorter-wavelength beacon. The TPA responsivity was measured for silicon using a PIN photodiode at a laser beacon wavelength of 1,550 nm. As expected, the responsivity shows a linear dependence with incident power level. The responsivity slope is 4.5 x 10(exp -7) A/W2. Also, optical beam spots from the 1,550-nm laser beacon were characterized on commercial charge coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) imagers with as little as 13.7 microWatts of optical power (see figure). This new tracker technology offers an innovative solution to reduce system complexity, improve transmit/receive isolation, improve optical efficiency, improve signal-to-noise ratio (SNR), and reduce cost for free-space optical communications transceivers.

  11. Two-Photon Absorption in Organometallic Bromide Perovskites

    KAUST Repository

    Walters, Grant

    2015-07-21

    Organometallic trihalide perovskites are solution processed semiconductors that have made great strides in third generation thin film light harvesting and light emitting optoelectronic devices. Recently it has been demonstrated that large, high purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order, have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW-1 at 800 nm, comparable to epitaxial single crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  12. Two-Photon Absorption in Organometallic Bromide Perovskites.

    Science.gov (United States)

    Walters, Grant; Sutherland, Brandon R; Hoogland, Sjoerd; Shi, Dong; Comin, Riccardo; Sellan, Daniel P; Bakr, Osman M; Sargent, Edward H

    2015-09-22

    Organometallic trihalide perovskites are solution-processed semiconductors that have made great strides in third-generation thin film light-harvesting and light-emitting optoelectronic devices. Recently, it has been demonstrated that large, high-purity single crystals of these perovskites can be synthesized from the solution phase. These crystals' large dimensions, clean bandgap, and solid-state order have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW(-1) at 800 nm, comparable to epitaxial single-crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.

  13. Two-photon absorption and spectroscopy of the lowest two-photon transition in small donor-acceptor-substituted organic molecules

    Science.gov (United States)

    Beels, Marten T.; Biaggio, Ivan; Reekie, Tristan; Chiu, Melanie; Diederich, François

    2015-04-01

    We determine the dispersion of the third-order polarizability of small donor-acceptor substituted organic molecules using wavelength-dependent degenerate four-wave mixing experiments in solutions with varying concentrations. We find that donor-acceptor-substituted molecules that are characterized by extremely efficient off-resonant nonlinearities also have a correspondingly high two-photon absorption cross section. The width and shape of the first two-photon resonance for these noncentrosymmetric molecules follows what is expected from their longest wavelength absorption peak, and the observed two-photon absorption cross sections are record high when compared to the available literature data, the size of the molecule, and the fundamental limit for two-photon absorption to the lowest excited state, which is essentially determined by the number of conjugated electrons and the excited-state energies. The two-photon absorption of the smallest molecule, which only has 16 electrons in its conjugated system, is one order of magnitude larger than for the molecule called AF-50, a reference molecule for two-photon absorption [O.-K. Kim et al., Chem. Mater. 12, 284 (2000), 10.1021/cm990662r].

  14. Chromophore design for large two-photon absorption

    Science.gov (United States)

    Dudley, Christopher

    2014-11-01

    Conjugated oligothiophene chromophores are compared and studied for designing large linear and nonlinear absorption cross-sections. Optical properties of chromophores synthesized by the Naval Research Laboratory are modeled to construct a design factor of merit to predict and understand two-photon absorption (TPA) designs. Computer modeling to optimize parameters to produce photo active chromophores is conducted. Geometry, π-center (electron relay) and the electron donor or acceptor groups attached to the π-centers are considered for importance in TPA. This work could serve equally well as guide for quick back of the envelop research or industrial design verifications as well as an outline for introducing computation methods to students.

  15. Two-photon absorption of Zn(II) octupolar molecules.

    Science.gov (United States)

    Mazzucato, Simone; Fortunati, Ilaria; Scolaro, Sara; Zerbetto, Michele; Ferrante, Camilla; Signorini, Raffaella; Pedron, Danilo; Bozio, Renato; Locatelli, Danika; Righetto, Stefania; Roberto, Dominique; Ugo, Renato; Abbotto, Alessandro; Archetti, Graziano; Beverina, Luca; Ghezzi, Sergio

    2007-06-21

    In this work we present an investigation of the non-linear optical (NLO) properties of two octupolar chromophores: [Zn(4,4'-bis(dibutylaminostyryl)-[2,2']-bipyridine)(3)](2+) and [Zn(4,4'-bis((E)-2-(N-(TEG)pyrrol-2-yl)vinyl)-[2,2']-bipyridine)(3)](2+) with Zn(ii) as the coordination center, using two-photon emission technique (TPE) in fs-pulse temporal regime. Compared to the free ligands, our results do not show a net increase in the two-photon absorption (TPA) cross-section for the octupolar complexes, once normalized to the ligand unit. This is in partial disagreement with a previous theoretical study investigating the first molecule where a significant increase of the TPA cross-section was predicted (X. J. Liu, et al., J. Chem. Phys., 2004, 120, 11 493).

  16. Synthesis of a Series of Novel Organic Compounds with Two-photon Absorption and Two-photon pumped Lasing

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A series of novel organic compounds named as CSPI, DPASPI, PSPI DEASPI and HEASPI respectively, with large two-photon absorption has been synthesized and their structures have been determined by 1HNMR and elemental analysis. The highest two-photon pumped (TPP) output /input efficiency is as high as 13.4% for PSPI in DMF with d0 = 0.03 mol/L and the effective two-photon absorption cross section is 8.8′10-48 cm4×s/photon for DPASPI in DMF with d0= 0.05mol/L.

  17. Synthesis,structure and nonlinear optical properties of two novel two-photon absorption chromophores

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Two triphenylamine-based derivatives that can be used as two-photon absorption chromophore,tris{4-[4-(3-trifluoromethyl-3-oxopanoyl)]phenyl}amine (1) and tris{4-[4-(3-phenyl-3-oxopanoyl)] phenyl} amine (2) were successfully synthesized and fully characterized by elemental analysis,IR,1H NMR and MS. The single crystal X-ray diffraction analysis showed that the molecules possess D-(π-A)3 structures. One-and two-photon absorption and fluorescence in various solvents were experimentally investigated. A data recording experiment proved the potential application of these chromophores.

  18. Theory of Two-Photon Absorptions in Graphene Fragments

    Science.gov (United States)

    Aryanpour, K.; Shukla, A.; Mazumdar, S.; Sandhu, A.; Roberts, A.

    2012-02-01

    Electron-electron correlations in graphene is currently an active field of research [1-3]. The carbon atoms in graphene have the same sp^2 hybridization as in strongly correlated π-conjugated polymer systems. The low energy behavior in graphene however appears to be reasonably described within the one-electron Dirac massless fermions model. Historically, the occurrence of the lowest two-photon state below the optical one-photon state provided the strongest proof for strong electron correlations in linear polyenes [4]. We systematically study the Coulomb interaction effects on the ground state and nonlinear absorptions in graphene fragments as a function of system size, beginning from the smallest stable fragment coronene. We report high order calculations of one- vs two-photon spin singlet and triplet states, in coronene, hexabenzocoronene and other molecular fragments that clearly indicate the strong role of electron-electron interactions. We will discuss the implications of our work on molecular systems for the thermodynamic limit of graphene. [4pt] [1] Siegel David A.; et al., PNAS, v108, 28, 11365-11369 (2011)[0pt] [2] Gr"onqvist J. H.; et al., arXiv: 1107.5653v1[0pt] [3] Uchoa B.; et al., arXiv: 1109.1577v1[0pt] [4] Ramasesha S.; et al., J. Chem. Phys. 80, 3278 (1984)

  19. Theoretical analysis on two-photon absorption spectroscopy in a confined four-level atomic system

    Institute of Scientific and Technical Information of China (English)

    Yuanyuan Li; Jintao Bai; Li Li; Yanpeng Zhang; Xun Hou

    2009-01-01

    We investigate theoretically two-photon absorption spectroscopy modified by a control field in a confined Y-type four-level system. Dicke-narrowing effect occurs both in two-photon absorption lines and the dips of transparency against two-photon absorption due to enhanced contribution of slow atoms. We also find that the suppression and the enhancement of two-photon absorption can be modified by changing the strength of the control field and the detuning of three laser fields. This control of two-photon absorption may have some applications in information processing and optical devices.

  20. Synergistic Two-Photon Absorption Enhancement in Photosynthetic Light Harvesting

    Science.gov (United States)

    Chen, Kuo-Mei; Chen, Yu-Wei; Gao, Ting-Fong

    2012-06-01

    The grand scale fixation of solar energies into chemical substances by photosynthetic reactions of light-harvesting organisms provides Earth's other life forms a thriving environment. Scientific explorations in the past decades have unraveled the fundamental photophysical and photochemical processes in photosynthesis. Higher plants, green algae, and light-harvesting bacteria utilize organized pigment-protein complexes to harvest solar power efficiently and the resultant electronic excitations are funneled into a reaction center, where the first charge separation process takes place. Here we show experimental evidences that green algae (Chlorella vulgaris) in vivo display a synergistic two-photon absorption enhancement in their photosynthetic light harvesting. Their absorption coefficients at various wavelengths display dramatic dependence on the photon flux. This newly found phenomenon is attributed to a coherence-electronic-energy-transfer-mediated (CEETRAM) photon absorption process of light-harvesting pigment-protein complexes of green algae. Under the ambient light level, algae and higher plants can utilize this quantum mechanical mechanism to create two entangled electronic excitations adjacently in their light-harvesting networks. Concerted multiple electron transfer reactions in the reaction centers and oxygen evolving complexes can be implemented efficiently by the coherent motion of two entangled excitons from antennae to the charge separation reaction sites. To fabricate nanostructured, synthetic light-harvesting apparatus, the paramount role of the CEETRAM photon absorption mechanism should be seriously considered in the strategic guidelines.

  1. New insight in boron chemistry: Application in two-photon absorption

    Science.gov (United States)

    Bolze, F.; Hayek, A.; Sun, X. H.; Baldeck, P. L.; Bourgogne, C.; Nicoud, J.-F.

    2011-07-01

    Two groups of one-dimensional (1D) boron containing two-photon absorbing fluorophores have been prepared and characterized. One group includes boron atoms incorporated in the conjugated or pseudo conjugated central core and the other contain a boron cluster as an acceptor group at one end of the fluorophores. Two boron containing central cores (with two boron atoms) have been explored: the cyclodiborazane and the pyrazabole moieties. The chosen boron cluster, p-carborane, contains 10 boron atoms. All the prepared fluorophores present high two-photon absorption cross-sections. Some water-soluble as well as lipophylic dyes have been prepared and used in bio-imaging.

  2. Two-Photon Absorption in Conjugated Energetic Molecules.

    Science.gov (United States)

    Bjorgaard, Josiah A; Sifain, Andrew E; Nelson, Tammie; Myers, Thomas W; Veauthier, Jacqueline M; Chavez, David E; Scharff, R Jason; Tretiak, Sergei

    2016-07-07

    Time-dependent density functional theory (TD-DFT) was used to investigate the relationship between molecular structure and the one- and two-photon absorption (OPA and TPA, respectively) properties of novel and recently synthesized conjugated energetic molecules (CEMs). The molecular structures of CEMs can be strategically altered to influence the heat of formation and oxygen balance, two factors that can contribute to the sensitivity and strength of an explosive material. OPA and TPA are sensitive to changes in molecular structure as well, influencing the optical range of excitation. We found calculated vertical excitation energies to be in good agreement with experiment for most molecules. Peak TPA intensities were found to be significant and on the order of 10(2) GM. Natural transition orbitals for essential electronic states defining TPA peaks of relatively large intensity were used to examine the character of relevant transitions. Modification of molecular substituents, such as additional oxygen or other functional groups, produces significant changes in electronic structure, OPA, and TPA and improves oxygen balance. The results show that certain molecules are apt to undergo nonlinear absorption, opening the possibility for controlled, direct optical initiation of CEMs through photochemical pathways.

  3. Investigation of two-photon absorption induced excited state absorption in a fluorenyl-based chromophore.

    Science.gov (United States)

    Li, Changwei; Yang, Kun; Feng, Yan; Su, Xinyan; Yang, Junyi; Jin, Xiao; Shui, Min; Wang, Yuxiao; Zhang, Xueru; Song, Yinglin; Xu, Hongyao

    2009-12-03

    Two-photon absorption induced excited state absorption in the solution of a new fluorenyl-based chromophore is investigated by a time-resolved pump-probe technique using femtosecond pulses. With the help of an additional femtosecond open-aperture Z-scan technique, numerical simulations based on a three-energy level model are used to interpret the experimental results, and we determine the nonlinear optical parameters of this new chromophore uniquely. Large two-photon absorption cross section and excited state absorption cross section for singlet excited state are obtained, indicating a good candidate for optical limiting devices. Moreover, the influence of two-beam coupling induced energy transfer in neat N,N'-dimethylformamide solvent is also considered, although this effect is strongly restrained by the instantaneous two-photon absorption.

  4. Electromagnetically induced absorption and transparency in an optical-rf two-photon coupling configuration

    Energy Technology Data Exchange (ETDEWEB)

    Fu Guangsheng [College of Physical Science and Technology, Hebei University, Baoding 071002 (China); Li Xiaoli [College of Physical Science and Technology, Hebei University, Baoding 071002 (China)], E-mail: xiaolixiaoli001@yahoo.com.cn; Zhuang Zhonghong; Zhang Lianshui; Yang Lijun; Li Xiaowei; Han Li [College of Physical Science and Technology, Hebei University, Baoding 071002 (China); Manson, Neil B.; Wei Changjiang [Laser Physics Center, Research School of Physical Sciences and Engineering, Australian Nation University, Canberra, ACT 0200 (Australia)

    2008-01-07

    We study electromagnetically induced absorption (EIA) and transparency (EIT) in an optical-rf two-photon coupling configuration. It is shown that the interference effect due to interacting dark resonances results in an EIA for a resonant two-photon coupling and this EIA is observed to evolve into an EIT when there is a detuning in the two-photon coupling.

  5. Two-photon absorption in gapped bilayer graphene with a tunable chemical potential

    Science.gov (United States)

    Brinkley, M. K.; Abergel, D. S. L.; Clader, B. D.

    2016-09-01

    Despite the now vast body of two-dimensional materials under study, bilayer graphene remains unique in two ways: it hosts a simultaneously tunable band gap and electron density; and stems from simple fabrication methods. These two advantages underscore why bilayer graphene is critical as a material for optoelectronic applications. In the work that follows, we calculate the one- and two-photon absorption coefficients for degenerate interband absorption in a graphene bilayer hosting an asymmetry gap and adjustable chemical potential—all at finite temperature. Our analysis is comprehensive, characterizing one- and two-photon absorptive behavior over wide ranges of photon energy, gap, chemical potential, and thermal broadening. The two-photon absorption coefficient for bilayer graphene displays a rich structure as a function of photon energy and band gap due to the existence of multiple absorption pathways and the nontrivial dispersion of the low energy bands. This systematic work will prove integral to the design of bilayer-graphene-based nonlinear optical devices.

  6. Biological oxygen sensing via two-photon absorption by an Ir(III) complex using a femtosecond fiber laser

    Science.gov (United States)

    Moritomo, Hiroki; Fujii, Akinari; Suzuki, Yasutaka; Yoshihara, Toshitada; Tobita, Seiji; Kawamata, Jun

    2016-09-01

    Near-infrared two-photon absorption of the phosphorescent Ir(III) complex (2,4-pentanedionato-κO 2,κO 4)bis[2-(6-phenanthridinyl-κN)benzo[b]thien-3-yl-κC]iridium (BTPHSA) was characterized. It exhibited a 800-1200 nm two-photon absorption band, and thus could be electronically excited by 1030-nm femtosecond Ti:sapphire and Yb-doped fiber lasers. By using BTPHSA, oxygen concentrations in human embryonic kidney 293 (HEK293) cells were imaged. These results demonstrate two-photon oxygen sensing of live tissues via easily operable excitation sources.

  7. Effect of morphology and solvent on two-photon absorption of nano zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    Kavitha, M.K. [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695547, Kerala (India); Haripadmam, P.C.; Gopinath, Pramod; Krishnan, Bindu [Department of Physics, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695547, Kerala (India); John, Honey, E-mail: honey@iist.ac.in [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695547, Kerala (India)

    2013-05-15

    Highlights: ► ZnO nanospheres and triangular structures synthesis by novel precipitation technique. ► The effect of precursor concentration on the size and shape of nano ZnO. ► Open aperture Z-scan measurements of the ZnO nanoparticle dispersions. ► Nanospheres exhibit higher two photon absorption coefficient than triangular nanostructures. ► Nanospheres dispersed in water exhibit higher two photon absorption coefficient than its dispersion in 2-propanol. - Abstract: In this paper, we report the effect of morphology and solvent on the two-photon absorption of nano zinc oxide. Zinc oxide nanoparticles in two different morphologies like nanospheres and triangular nanostructures are synthesized by novel precipitation technique and their two-photon absorption coefficient is measured using open aperture Z-scan technique. Experimental results show that the zinc oxide nanospheres exhibit higher two-photon absorption coefficient than the zinc oxide triangular nanostructures. The zinc oxide nanospheres dispersed in water exhibit higher two-photon absorption coefficient than that of its dispersion in 2-propanol. The zinc oxide nanospheres dispersed in water shows a decrease in two-photon absorption coefficient with an increase in on-axis irradiance. The result confirms the dependence of shape and solvent on the two-photon absorption of nano zinc oxide.

  8. Calculation of the spatial resolution in two-photon absorption spectroscopy applied to plasma diagnosis

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Lechuga, M. [Departamento de Física Teórica, Atómica y Óptica, Universidad de Valladolid, 47011-Valladolid (Spain); Laser Processing Group, Instituto de Óptica “Daza de Valdés,” CSIC, 28006-Madrid (Spain); Fuentes, L. M. [Departamento de Física Aplicada, Universidad de Valladolid, 47011-Valladolid (Spain); Grützmacher, K.; Pérez, C., E-mail: concha@opt.uva.es; Rosa, M. I. de la [Departamento de Física Teórica, Atómica y Óptica, Universidad de Valladolid, 47011-Valladolid (Spain)

    2014-10-07

    We report a detailed characterization of the spatial resolution provided by two-photon absorption spectroscopy suited for plasma diagnosis via the 1S-2S transition of atomic hydrogen for optogalvanic detection and laser induced fluorescence (LIF). A precise knowledge of the spatial resolution is crucial for a correct interpretation of measurements, if the plasma parameters to be analysed undergo strong spatial variations. The present study is based on a novel approach which provides a reliable and realistic determination of the spatial resolution. Measured irradiance distribution of laser beam waists in the overlap volume, provided by a high resolution UV camera, are employed to resolve coupled rate equations accounting for two-photon excitation, fluorescence decay and ionization. The resulting three-dimensional yield distributions reveal in detail the spatial resolution for optogalvanic and LIF detection and related saturation due to depletion. Two-photon absorption profiles broader than the Fourier transform-limited laser bandwidth are also incorporated in the calculations. The approach allows an accurate analysis of the spatial resolution present in recent and future measurements.

  9. Two-photon absorption of [2.2]paracyclophane derivatives in solution: A theoretical investigation

    Science.gov (United States)

    Ferrighi, Lara; Frediani, Luca; Fossgaard, Eirik; Ruud, Kenneth

    2007-12-01

    The two-photon absorption of a class of [2.2]paracyclophane derivatives has been studied using quadratic response and density functional theories. For the molecules investigated, several effects influencing the two-photon absorption spectra have been investigated, such as side-chain elongation, hydrogen bonding, the use of ionic species, and solvent effects, the latter described by the polarizable continuum model. The calculations have been carried out using a recent parallel implementation of the polarizable continuum model in the DALTON code. Special attention is given to those aspects that could explain the large solvent effect on the two-photon absorption cross sections observed experimentally for this class of compounds.

  10. Four-State Model for Three-Branch Molecule's Two-Photon Absorption Properties

    Institute of Scientific and Technical Information of China (English)

    SU Yan; WANG Pei-Ji; ZHAO Peng; RONG Zhen-Yu

    2006-01-01

    @@ We present a four-state model for calculating the two-photon absorption of multi-branched molecules by using the time-depended function method. The numerical results indicate that the two-photon absorption cross section has a strong enhancement for three-branch molecules compared to two-branch structures. The maximal two-photon-absorption cross section is 2.358 × 10-47 cm 4 s/photon. At the same time, the charge-transfer process for the charge-transfer states is visualized in order to explain mechanism about the maximal TPA cross section.

  11. Two-photon absorption and transient photothermal imaging of pigments in tissues

    Science.gov (United States)

    Ye, Tong; Fu, Dan; Matthews, Thomas E.; Hong, Lian; Simon, John D.; Warren, Warren S.

    2008-02-01

    As a main pigment in skin tissues, melanin plays an important role in photo-protecting skin from UV radiation. However, melanogenesis may be altered due to disease or environmental factors; for example, sun exposure may cause damage and mutation of melanocytes and induce melanoma. Imaging pigmentation changes may provide invaluable information to catch the malignant transformation in its early stage and in turn improve the prognosis of patients. We have demonstrated previously that transmission mode, two-photon, one- or two-color absorption microscopy could provide remarkable contrast in imaging melanin in skin. In this report we demonstrate significantly improved sensitivity, so that we are now able to image in epi-mode (or back reflection) in two-photon absorption. This improvement makes possible for us to characterize the different types of pigmentation on the skin in vivo at virtually any location. Another finding is that we can also image transient photothermal dynamics due to the light absorption of melanin. By carefully choosing excitation and probe wavelengths, we might be able to image melanin in different structures under different micro-environments in skin, which could provide useful photochemical and photophysical insights in understanding how pigments are involved in photoprotection and photodamage of cells.

  12. Influence of Two Photon Absorption on Soliton Self-Frequency Shift

    DEFF Research Database (Denmark)

    Steffensen, Henrik; Rottwitt, Karsten; Jepsen, Peter Uhd;

    2011-01-01

    The creation of mid-infrared supercontinua necessitates the use of soft-glass fibers. However, some materials, like chalcogenide, have a substantial two photon absorption. We introduce a model for soliton self-frequency shift that successfully includes this effect.......The creation of mid-infrared supercontinua necessitates the use of soft-glass fibers. However, some materials, like chalcogenide, have a substantial two photon absorption. We introduce a model for soliton self-frequency shift that successfully includes this effect....

  13. Two-photon absorption properties of a new series of 2CTσ chromophores

    Science.gov (United States)

    Zhou, Yu-fang; Meng, Fan-qing; Zhao, Xian; Xu, Dong; Jiang, Min-hu

    2000-10-01

    We have designed and synthesized a new series of two-photon ASPT-like charge transfer moieties linked by σ-bond spacers to N-position of pyridine cycle. Both theoretical and experimental results show there is no linear absorption in 600-1300 nm, so two-photon properties can be expected in this range. Two-photon absorption (TPA) cross-sections were calculated by using INDO/CI and SOS methods. The results show that those compounds possess large cross-sections as well as appropriate absorption wavelengths. Also the magnitude of the cross-section changes regularly with the number of the σ-bond spacers. These imply that they are good candidates for two-photon devices.

  14. Pseudopotential calculations and photothermal lensing measurements of two-photon absorption in solids

    Energy Technology Data Exchange (ETDEWEB)

    White, W.T. III

    1985-11-04

    We have studied two-photon absorption in solids theoretically and experimentally. We have shown that it is possible to use accurate band structure techniques to compute two-photon absorption spectra within 15% of measured values in a wide band-gap material, ZnS. The empirical pseudopotential technique that we used is significantly more accurate than previous models of two-photon absorption in zinc blende materials, including present tunneling theories (which are essentially parabolic-band results in disguise) and the nonparabolic-band formalism of Pidgeon et al. and Weiler. The agreement between our predictions and previous measurements allowed us to use ZnS as a reference material in order to validate a technique for measuring two-photon absorption that was previously untried in solids, pulsed dual-beam thermal lensing. With the validated technique, we examined nonlinear absorption in one other crystal (rutile) and in several glasses, including silicates, borosilicates, and one phosphate glass. Initially, we believed that the absorption edges of all the materials were comparable; however, subsequent evidence suggested that the effective band-gap energies of the glasses were above the energy of two photons in our measurement. Therefore, we attribute the nonlinear absorption that we observed in glasses to impurities or defects. The measured nonlinear absorption coefficients were of the order of a few cm/TW in the glasses and of the order of 10 cm/GW in the crystals, four orders of magnitude higher than in glasses. 292 refs.

  15. Two-photon STED spectral determination for a new V-shaped organic fluorescent probe with efficient two-photon absorption.

    Science.gov (United States)

    Belfield, Kevin D; Bondar, Mykhailo V; Morales, Alma R; Padilha, Lazaro A; Przhonska, Olga V; Wang, Xuhua

    2011-10-24

    Two-photon stimulated emission depletion (STED) cross sections were determined over a broad spectral range for a novel two-photon absorbing organic molecule, representing the first such report. The synthesis, comprehensive linear photophysical, two-photon absorption (2PA), and stimulated emission properties of a new fluorene-based compound, (E)-2-{3-[2-(7-(diphenylamino)-9,9-diethyl-9H-fluoren-2-yl)vinyl]-5-methyl-4-oxocyclohexa-2,5-dienylidene} malononitrile (1), are presented. Linear spectral parameters, including excitation anisotropy and fluorescence lifetimes, were obtained over a broad range of organic solvents at room temperature. The degenerate two-photon absorption (2PA) spectrum of 1 was determined with a combination of the direct open-aperture Z-scan and relative two-photon-induced fluorescence methods using 1 kHz femtosecond excitation. The maximum value of the 2PA cross section ~1700 GM was observed in the main, long wavelength, one-photon absorption band. One- and two-photon stimulated emission spectra of 1 were obtained over a broad spectral range using a femtosecond pump-probe technique, resulting in relatively high two-photon stimulated emission depletion cross sections (~1200 GM). A potential application of 1 in bioimaging was demonstrated through one- and two-photon fluorescence microscopy images of HCT 116 cells incubated with micelle-encapsulated dye.

  16. Highly selective population of two excited states in nonresonant two-photon absorption

    Institute of Scientific and Technical Information of China (English)

    Zhang Hui; Zhang Shi-An; Sun Zhen-Rong

    2011-01-01

    A nonresonant two-photon absorption process can be manipulated by tailoring the ultra-short laser pulse.In this paper,we theoretically demonstrate a highly selective population of two excited states in the nonresonant two-photon absorption process by rationally designing a spectral phase distribution.Our results show that one excited state is maximally populated while the other state population is widely tunable from zero to the maximum value.We believe that the theoretical results may play an important role in the selective population of a more complex nonlinear process comprising nonresonant two-photon absorption,such as resonance-mediated(2+1)-three-photon absorption and (2+1)-resonant multiphoton ionization.

  17. Near IR two photon absorption of cyanines dyes: application to optical power limiting at telecommunication wavelengths

    Science.gov (United States)

    Bouit, Pierre-Antoine; Wetzel, Guillaume; Feneyrou, Patrick; Bretonnière, Yann; Kamada, Kenji; Maury, Olivier; Andraud, Chantal

    2008-02-01

    The design and synthesis of symmetrical and unsymmetrical heptamethine cyanines is reported. These chromophores present significant two-photon cross section in the 1400-1600 nm spectral range. In addition, they display optical power limiting (OPL) properties. OPL curves were interpreted on the basis of two-photon absorption (2PA) followed by excited state absorption (ESA). Finally, these molecules present several relevant properties (nonlinear absorption properties, two-step gram scale synthesis, high solubility, good thermal stability), which could lead to numerous practical applications in material science (solid state optical limiting, signal processing) or in biology (imaging).

  18. Two-Photon Absorption Properties of Mn-Doped ZnS Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    ZHENG Jia-Jin; ZHANG Gui-Lan; GUO Yang-Xue; WANG Xiao-Yan; CHEN Wen-Ju; ZHANG Xiao-Song; HUA Yu-Lin

    2006-01-01

    @@ We investigate the two-photon absorption and nonlinear refractive index properties of a quantum dot material based on ZnS nanocrystals doped with Mn isoelectronic impurities, using the Z-scan technique with 532nm picosecond laser pulses. The Mn-doped ZnS quantum dots have an average two-photon absorption cross section as high as 13600 Goeppert-Mayer units, which turn it into a very promising material for fluorescent label and imaging in biological samples. In addition, we also found that the two-photon absorption coeflicient initially increases and then decreases with increasing pulse irradiance, which demonstrates the presence of the higherorder nonlinearity under the strong excitation.

  19. Dispersion of nonlinear refractive index in layered WS2 and WSe2 semiconductor films induced by two-photon absorption.

    Science.gov (United States)

    Dong, Ningning; Li, Yuanxin; Zhang, Saifeng; McEvoy, Niall; Zhang, Xiaoyan; Cui, Yun; Zhang, Long; Duesberg, Georg S; Wang, Jun

    2016-09-01

    Both the nonlinear absorption and nonlinear refraction properties of WS2 and WSe2 semiconductor films have been characterized by using Z-scan technique with femtosecond pulses at the wavelength of 1040 nm. It is found that these films have two-photon absorption response with the nonlinear absorption coefficient of ∼103  cm GW-1, and a dispersion of nonlinear refractive index in the WS2 films that translated from positive in the monolayer to negative in bulk materials.

  20. Effects of torsional disorder and position isomerism on two-photon absorption properties of polar chromophore dimers

    Science.gov (United States)

    Jia, Hai-Hong; Zhao, Ke; Wu, Xiang-Lian

    2014-09-01

    Two-photon absorption properties of a push-pull molecule and its covalent dimers have been studied by density functional response theory in combination with polarizable continuum model. A set of constrained geometries with different torsional angles are optimized and used to calculate two-photon absorption spectra. It is found that the torsional disorder could possibly produce the experimental two-photon absorption additive behavior. We have also designed a series of covalent dimers and investigated the effects of position isomerism. Our results suggest that the cooperative two-photon absorption enhancement can be achieved when the subunits are substituted in closer proximity and have larger interchromophore angle.

  1. Two-Photon Absorption-Induced Emission Properties of Dye HMASPS Doped Polymer

    Institute of Scientific and Technical Information of China (English)

    王东; 周广勇; 任燕; 杨胜军; 许心光; 邵宗书; 蒋民华

    2002-01-01

    The 0.01M two-photon absorption dye trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methyl-pyridinium p-toluene sulfonate (HMASPS) doped polymer has been prepared. When pumped by the picosecond pulse from the pulsed mode-locked Nd: YAG laser, the polymer emits more intense upconverted fluorescence and superradiance compared to the solution sample of the dye. The two-photon pumped lasing with oscillating pulses has also been obtained. Compared to the dye in its solution state, the emission spectra of the polymer are all blueshifted.The polymer has a long upconverted fluorescent lifetime of about 4.041 ± 0.04 ns.

  2. Two-photon absorption and two-photon circular dichroism of L-tryptophan in the near to far UV region

    Science.gov (United States)

    Vesga, Yuly; Hernandez, Florencio E.

    2017-09-01

    Herein we report on the first measurements of the two-photon absorption (TPA) spectrum of L-tryptophan in DMSO solution in the near to far UV region and the two-photon circular dichroism (TPCD) signal corresponding to a transition at 200 nm. We demonstrate the application of the Double L-scan technique in the near to far UV region to perform polarization dependent TPA measurements of chiral molecules. TPCD measurements below 400 nm reveal that chiral molecules in solution, such as tryptophan/DMSO, can undergo photochemical reactions in front of prolonged exposure to UV radiation.

  3. Determination of Kerr and two-photon absorption coefficients of indandione derivatives

    Science.gov (United States)

    Bundulis, Arturs; Mihailovs, Igors; Nitiss, Edgars; Busenbergs, Janis; Rutkis, Martins

    2017-05-01

    We studied nonlinear optical properties of two different aminobenziliden-1,3-indandione derivatives - DDMABI and DMABI-OH by employing the Z-scan method. Through this we described how different donor and acceptor groups influence third-order nonlinear optical properties such as Kerr effect and two-photon absorption. During experimental measurements we used 1064 nm Nd:YAG laser with 30 ps pulse duration and 10 Hz repetition rate. From acquired values of Kerr and two-photon absorption coefficients we calculated values for real and imaginary parts of third-order susceptibility, as well as second-order hyperpolarizability. Quantum chemical calculations were carried out for secondorder hyperpolarizability to study how well calculations correlate with experimental values. Acquired data for DDMABI and DMABI-OH were compared with data for other ABI derivatives studied previously.

  4. Two-photon absorption in mesoionic compounds pumped at the visible and at the infrared

    CERN Document Server

    Rakov, N; Da Rocha, G B; Simas, A M; Athayde-Filho, P A F; Miller, J

    2000-01-01

    Intensity dependent transmission and laser-induced fluorescence were observed in liquid solutions of mesoionic compounds (MIC) pumped with nanosecond lasers operating at 1064, 604, and 570 nm. The results indicate that two-photon absorption (TPA) is the dominant mechanism which causes the observed behavior. The TPA cross-sections measured have values from 0.33*10/sup -20/ cm/sup 4//GW to 0.43*10/sup -18/ cm /sup 4//GW. (20 refs).

  5. Morphology dependent two photon absorption in plasmonic structures and plasmonic-organic hybrids

    Science.gov (United States)

    Gambhir, Kaweri; Ray, Bhumika; Mehrotra, Ranjana; Sharma, Parag

    2017-05-01

    Two photon absorption coefficients of two distinct plasmonic structures, namely, gold nanoflowers (GNF) and gold nanopebbles (GNP) have been investigated and compared with conventional gold nanospheres (GNS). All three different nanoshapes were synthesized by changing the reaction solvent under the same experimental procedure. Further, hybrids of these plasmonic structures were prepared with an organic dye Eosin yellow (EY), to investigate the morphology effect of plasmonic structures on plasmonic-organic hybrids in terms of their linear extinction spectra and two photon absorption coefficients. The NLO investigations were conducted using 20 ps laser pulses of wavelength 532 nm as an excitation source in single beam Z-scan setup. UV/visible spectroscopy was employed for monitoring plasmon resonances and changes in linear extinction spectra. The experimental outcomes revealed two photon absorption coefficients of EY increased 120%, 32% and 39%, while 69%, 60% and 53% enhancement in the peaks of linear extinction maxima of EY has been observed, when hybridized with GNF, GNS and GNP, respectively. This boost in the optical coefficients may be attributed to dimerization of EY molecules on the surface of nanoparticles. Keeping the toxicity of EY in view, we propose that the two photon absorption coefficients of this dye and control thereof, by the addition of plasmonic structures would be helpful not only in understanding the interactions between plasmons and fluorophore, but also pave an efficient way, to reduce the operative concentration of this hazardous dye in a wide range of applications and thereby, mitigating the environmental degradation caused by its highly concentrated effluents.

  6. Two-photon absorption coefficient dichroism in Ⅱ-Ⅵ semiconductor crystals

    Institute of Scientific and Technical Information of China (English)

    Ma Guo-Hong; Ma Hong-Liang; Tang Sing-Hai

    2007-01-01

    Considering two beams propagate in semiconductor crystal, this paper discusses the polarization dependence of pump beam-induced intensity attenuation of probe beam due to two-photon absorption (TPA). Numerical calculation and experimental measurement demonstrate that TPA coefficient is polarization dependent. For homogeneous materials,probe beam attenuation arises from the imaginary part of diagonal and off-diagonal components of third-order nonlinear susceptibilities.

  7. Colloidal quantum-dot-based silica gel glass: two-photon absorption, emission, and quenching mechanism.

    Science.gov (United States)

    Li, Jingzhou; Dong, Hongxing; Zhang, Saifeng; Ma, Yunfei; Wang, Jun; Zhang, Long

    2016-09-28

    Two-photon (TP) three-dimensional solid matrices have potential applications in high density optical data reading and storage, infrared-pumped visible displays, lasers, etc. Such technologies will benefit greatly from the advantageous properties of TP materials including tunable emission wavelength, photostability, and simple chemical processing. Here, this ideal TP solid is made possible by using a facile sol-gel process to engineer colloid quantum dots into silica gel glass. Characterization using an open-aperture Z-scan technique shows that the solid matrices exhibited significant TP optical properties with a TP absorption coefficient of (9.41 ± 0.39) × 10(-2) cm GW(-1) and a third-order nonlinear figure of merit of (7.30 ± 0.30) × 10(-14) esu cm. In addition, the dependence of the TP properties on high-temperature thermal treatment is studied in detail to obtain a clear insight for practical applications. The results illustrate that the sample can maintain stable TP performance below the synthesis temperature of the CdTe/CdS colloidal quantum dots. Furthermore, the mechanisms for thermal quenching of photoluminescence under different temperature regimes are clarified as a function of the composition.

  8. Novel xenon calibration scheme for two-photon absorption laser induced fluorescence of hydrogen

    Science.gov (United States)

    Elliott, Drew; Scime, Earl; Short, Zachary

    2016-11-01

    Two photon absorption laser induced fluorescence (TALIF) measurements of neutral hydrogen and its isotopes are typically calibrated by performing TALIF measurements on krypton with the same diagnostic system and using the known ratio of the absorption cross sections [K. Niemi et al., J. Phys. D 34, 2330 (2001)]. Here we present the measurements of a new calibration method based on a ground state xenon scheme for which the fluorescent emission wavelength is nearly identical to that of hydrogen, thereby eliminating chromatic effects in the collection optics and simplifying detector calibration. We determine that the ratio of the TALIF cross sections of xenon and hydrogen is 0.024 ± 0.001.

  9. A Relative Study on Two-photon Absorption Properties of C60 and C70

    Institute of Scientific and Technical Information of China (English)

    ZHOU,Xin(周新); REN,Ai-Min(任爱民); FENG,Ji-Kang(封继康); LIU,Xiao-Juan(刘孝娟)

    2004-01-01

    We have theoretically investigated the one- and two-photon absorption properties of C60 and C70 using the ZINDO method. From the results it is suggested that the one-photon absorption spectra are in agreement with the experimental observations. It is found that the maximum TPA cross section of C70 is more than twice that of C60,which is consistent with the experimental results. A notable point is that the TPA process of C60 is different from that of C70 as well as other ordinary conjugated molecules.

  10. Two-photon absorption measurements in graphene fragments: Role of electron-electron interactions

    Science.gov (United States)

    Sandhu, A.; Roberts, A.; Aryanpour, K.; Shukla, A.; Mazumdar, S.

    2012-02-01

    Many-body interactions in graphene are an active field of research. There is a clear evidence of strong electron correlation effects in other carbon based materials which have the same sp^2 hybridization as graphene. For example, in linear-polyenes, the electron-electron interactions are considered responsible for the occurrence of lowest two-photon state below the optical one-photon state. The electronic correlation in these linear systems is a strong function of the chain length. Thus, it is pertinent to question if the two-dimensional graphene fragments also exhibit strong correlation effects and how these effects scale with fragment size. Using a white light super-continuum source, we perform z-scan measurements to extract frequency-dependent two-photon absorption coefficients in symmetric molecular fragments of graphene, e.g. coronene and hexabenzocoronene. A comparison of one-photon and two-photon absorption coefficients is then used to uncover the extent of correlation effects. In the smallest fragment, coronene, our results indicate a strong signature of the Coulomb interactions. We will discuss how the importance of electron-electron interaction varies with system size and its implication for the correlation effects in graphene.

  11. Generalized Kramers-Heisenberg expressions for stimulated Raman scattering and two-photon absorption

    Science.gov (United States)

    Roslyak, Oleksiy; Marx, Christoph A.; Mukamel, Shaul

    2010-01-01

    The frequency-domain pump-probe signal of a material system interacting with two quantum modes of the radiation field is recast in terms of products of scattering amplitudes (T matrix elements) rather than the third-order susceptibility Im χ(3). The resulting expression offers a more intuitive physical picture for the optical process compared with the semiclassical approach which treats the radiation field as classical. It can be derived and interpreted using closed-time-path-loop diagrams which represent the joint state of the matter and the field for each contribution to the signal. The signal has two components representing stimulated Raman scattering ω1 − ω2 and two-photon absorption ω1 + ω2 two-photon resonances. Both are expressed as nonequi-librium steady-state photon and matter fluxes, as is common in the description of dissipative processes in open quantum systems. PMID:20613889

  12. Enhancement of Two-photon Absorption by Ce3+ Sensitization in Organic Dyes

    Institute of Scientific and Technical Information of China (English)

    LI Jian-fu; SUN Cheng-lin; ZHOU Hai-ling; XU Li-hua; YANG Qing-xin; JIANG Zhan-kui

    2007-01-01

    The two-photon absorption (TPA) and TPA-induced frequency upconversion emission properties of the dyes4-[P-(dicyanoethylamino) crystal]-N-methypyrdinium iodide and the complex of 4-[ P-(dicyanoethylamino) crystal]-N-methypyrdinium iodide and Ce( NO3 )3 were experimentally studied. It was found that the TPA cross section for the dye sensitized by Ce3+ is two factors larger than that of the dye without being sensitized. A three-level system model of the dye molecules was used to analyze the enhancement of TPA by the sensitizer Ce3+, which indicated that the sensitizer results in the increase of the transition dipole moment from the one-photon allowed excited state(1Bu)to the two-photon allowed excited state(2Ag).

  13. Confined optical-phonon-assisted cyclotron resonance in quantum wells via two-photon absorption process

    Science.gov (United States)

    Phuc, Huynh Vinh; Hien, Nguyen Dinh; Dinh, Le; Phong, Tran Cong

    2016-06-01

    The effect of confined phonons on the phonon-assisted cyclotron resonance (PACR) via both one and two photon absorption processes in a quantum well is theoretically studied. We consider cases when electrons are scattered by confined optical phonons described by the Fuchs-Kliewer slab, Ridley's guided, and Huang-Zhu models. The analytical expression of the magneto-optical absorption coefficient (MOAC) is obtained by relating it to the transition probability for the absorption of photons. It predicts resonant peaks caused by transitions between Landau levels and electric subband accompanied by confined phonons emission in the absorption spectrum. The MOAC and the full-width at half-maximum (FWHM) for the intra- and inter-subband transitions are given as functions of the magnetic field, temperature, and quantum well width. In narrow quantum wells, the phonon confinement becomes more important and should be taken into account in studying FWHM.

  14. Two-photon absorption and frequency-upconversion properties of a new organic dye HMASPS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Two-photon absorption (TPA) and frequency- upconversion properties of a new upconversion laser dye trans-4-[p-(N-hydroxyethyl-N-methyl-amino)styryl]-N-meth- ylpyridinium toluene-p-sulfonate (abbreviated to HMASPS) were reported in this note. The linear absorption, TPA, single-photon induced fluorescence, TPA induced fluorescence and TPA induced upconverted lasing spectra of HMASPS solution in dimethyl formamide (abbreviated to DMF) were measured at room temperature. The red shift for the central wavelength of TPA induced fluorescence peak, which was compared with that of the single-photon induced fluorescen-ce peak, and the blue shift for that of TPA induced upcon-verted lasing compared with that of TPA induced fluores-cence, were explained by using re-absorption effect. TPA peak was at 930 nm. There is an 11 nm blue shift for two-photon energy of TPA peak compared with the linear ab-sorption peak. The molecular TPA cross-section at 1064 nm was measured to be 6.0′10-48 cm4 ·s/photon by using the open aperture Z-scanning system. The highest upconversion efficiency was measured to be 8.4% at 1064 nm.

  15. Aggregation induced enhanced emission of conjugated dendrimers with a large intrinsic two-photon absorption cross-section

    NARCIS (Netherlands)

    Xu, Bin; Zhang, Jibo; Fang, Honghua; Ma, Suqian; Chen, Qidai; Sun, Hongbo; Im, Chan; Tian, Wenjing

    2014-01-01

    Organic nonlinear optical materials combining high luminescence quantum yields and large two-photon absorption cross-sections are attractive for both fundamental research and practical applications, such as up-converted lasers and two-photon fluorescence microscopy. Herein, we reported a series of

  16. Ophthalmic drug delivery utilizing two-photon absorption: a novel approach to treat posterior capsule opacification

    Science.gov (United States)

    Kim, H.-C.; Träger, J.; Zorn, M.; Haberkorn, N.; Hampp, N.

    2007-07-01

    Intraocular lens (IOL) implantation is the standard technique to treat cataract. Despite recent progress in surgical procedures, posterior capsule opacification is one of the sill remaining postoperative complications of cataract surgery. We present a novel strategy to reduce the incidence of posterior capsule opacification. A drug delivery polymer suitable for manufacturing intraocular lenses has been developed which enables repeated drug release in a non-invasive and controlled manner. The therapeutic molecules are attached through a UV light sensitive linkage to the polymer backbone which is mainly responsible for the optical properties of the intraocular lenses. However, UV light can not trigger the release of drug from the polymer due to the high absorption of the cornea. We developed linkers which enable drug release by two-photon absorption induced cleavage of the linker structure. Since the two-photon absorption requires high photon densities, this does not occur in ambient light conditions in daily life, but is easily triggered by focused laser beams from a pulsed laser. In this proof-of-principle study we have employed a cyclobutane type linker and investigated the properties of the therapeutic system with the approved drugs 5-fluorouracil and chlorambucil. The controlled drug delivery was successfully demonstrated in vitro and additional cell tests confirmed that the device itself shows no cytotoxicity until photochemical activation. This presented concept can provide a powerful method in ophthalmic drug delivery.

  17. Two-Photon Absorption and Optical Power Limiting Based on New Organic Dyes

    Institute of Scientific and Technical Information of China (English)

    周广勇; 王东; 邵宗书; 蒋民华; 雷虹

    2001-01-01

    Two new organic dye samples J and L with a large two-photon absorption (TPA) cross section have been reported.The linear absorption spectra show that there is no linear absorption at the wavelength from 650 to 1200 nm.The molecular TPA cross section was measured to be as high as 2.59×10-47 cm4.s and 2.98×10-47 cm4.s at 1064 nm for samples J and L, respectively. The input-output curves indicate that there is a clear optical power limiting behaviour when the input intensity is higher than 0.4 GW/cm2. Furthermore, the basic theory of the TPA process has been discussed.

  18. Giant Two-photon Absorption in Circular Graphene Quantum Dots in Infrared Region

    Science.gov (United States)

    Feng, Xiaobo; Li, Zhisong; Li, Xin; Liu, Yingkai

    2016-01-01

    We investigate theoretically the two-photon absorption (TPA) for circular graphene quantum dots (GQDs) with the edge of armchair and zigzag on the basis of electronic energy states obtained by solving the Dirac-Weyl equation numerically under finite difference method. The expressions for TPA cross section are derived and the transition selection rules are obtained. Results reveal that the TPA is significantly greater in GQDs than conventional semiconductor QDs in infrared spectrum (2–6 um) with a resonant TPA cross section of up to 1011 GM. The TPA peaks are tuned by the GQDs’ size, edge and electron relaxation rate. PMID:27629800

  19. Giant Two-photon Absorption in Circular Graphene Quantum Dots in Infrared Region

    Science.gov (United States)

    Feng, Xiaobo; Li, Zhisong; Li, Xin; Liu, Yingkai

    2016-09-01

    We investigate theoretically the two-photon absorption (TPA) for circular graphene quantum dots (GQDs) with the edge of armchair and zigzag on the basis of electronic energy states obtained by solving the Dirac-Weyl equation numerically under finite difference method. The expressions for TPA cross section are derived and the transition selection rules are obtained. Results reveal that the TPA is significantly greater in GQDs than conventional semiconductor QDs in infrared spectrum (2-6 um) with a resonant TPA cross section of up to 1011 GM. The TPA peaks are tuned by the GQDs’ size, edge and electron relaxation rate.

  20. Symmetry Breaking in Platinum Acetylide Chromophores Studied by Femtosecond Two-Photon Absorption Spectroscopy

    Science.gov (United States)

    2014-02-01

    The 1PA spectrum in toluene (solid line, top and right axes) and NLT of blank sample (filled black diamonds ) are shown for comparison. The Journal of...G.W., and M.D. ■ REFERENCES (1) Guha, S.; Frazier, C. C.; Porter , P. L.; Kang, K.; Finberg, S. E. Measurement of the 3rd-Order Hyperpolarizability of Pt...Poly-Ynes. Opt. Lett. 1989, 14, 952−954. (2) Guha, S.; kang, K.; Porter , P. L. Two-Photon Absorption-Induced Thermal Effects in Platinum Poly-Ynes

  1. Two-Photon Absorption Spectroscopy of Rubidium with a Dual-Comb Tequnique

    Science.gov (United States)

    Nishiyama, Akiko; Yoshida, Satoru; Hariki, Takuya; Nakajima, Yoshiaki; Minoshima, Kaoru

    2017-06-01

    Dual-comb spectroscopies have great potential for high-resolution molecular and atomic spectroscopies, thanks to the broadband comb spectrum consisting of dense narrow modes. In this study, we apply the dual-comb system to Doppler-free two-photon absorption spectroscopy. The outputs of two frequency combs excite several two-photon transitions of rubidium, and we obtained broadband Doppler-free spectra from dual-comb fluorescence signals. The fluorescence detection scheme circumvents the sensitivity limit which is effectively determined by the dynamic range of photodetectors in absorption-based dual-comb spectroscopies. Our system realized high-sensitive, Doppler-free high-resolution and broadband atomic spectroscopy. A part of observed spectra of 5S_{1/2} - 5D_{5/2} transition is shown in the figure. The hyperfine structures of the F" = 1 - F' = 3,2,1 transitions are fully-resolved and the spectral widths are approximately 5 MHz. The absolute frequency axis is precisely calibrated from comb mode frequencies which were stabilized to a GPS-disciplined clock. This work was supported by JST through the ERATO MINOSHIMA Intelligent Optical Synthesizer Project and Grant-in-Aid for JSPS Fellows (16J02345). A. Nishiyama, S. Yoshida, Y. Nakajima, H. Sasada, K. Nakagawa, A. Onae, K. and Minoshima, Opt. Express 24, 25894 (2016). A. Hipke, S. A. Meek, T. Ideguchi, T.W. Hänsch, and N. Picqué, Phys. Rev. A 90, 011805(R) (2014).

  2. One- and two-photon absorption properties of two metalloporphyrin complexes

    Institute of Scientific and Technical Information of China (English)

    Sun Yuan-Hong; Wang Chuan-Kui

    2011-01-01

    The linear and nonlinear optical properties of two metalloporphyrin complexes formed by the complementary coordination of central zinc or magnesium ions to the ligand 5,10,15-tri-(p-tolyl)-20-phenylethynylporphyrin are theoretically investigated by using the analytic response theory at the density functional theory level.The results indicate that the studied complexes present more symmetric geometry structures than the ligand.The charge-transfer states of the two complexes in the lower energy region are all almost degenerate but those of the ligand are well separated.The ratio of the two-photon absorption cross sections of the ligand,zinc-porphyrin and magnesium-porphyrin complexes is 1.0:1.5:1.8,demonstrating that the two-photon absorption capability can be greatly increased when the ligand is coordinated with a metal ion.Moreover,several physical micro-mechanisms including electron transitions and intramolecular charge-transfer processes are discussed to explore the differences in optical property between the ligand and two complexes.

  3. Optical limiting effect in a two-photon absorption dye doped solid matrix

    Science.gov (United States)

    He, Guang S.; Bhawalkar, Jayant D.; Zhao, Chan F.; Prasad, Paras N.

    1995-10-01

    We recently reported a new lasing dye, trans-4-[p-(N-ethyl-N-hydroxylethylamino)styryl]-N-methylpyridinium tetraphenylborate (ASPT), which has also been shown to possess a strong two-photon absorption (TPA) and subsequent frequency upconversion fluorescence behavior when excited with near infrared laser radiation. Based on the TPA mechanism, a highly efficient optical limiting performance has been demonstrated in a 2 cm long ASPT-doped epoxy rod pumped with 1.06 μm Q-switched laser pulses at 50-250 MW/cm2 intensity levels. The measured nonlinear absorption coefficient reached 6 cm/GW for the tested sample of dopant concentration d0=4×10-3 M/L. The molecular TPA cross section of ASPT in the epoxy matrix is estimated as σ2=2.5×10-18 cm4/GW or σ2'=4.7×10-46 cm4/photon/s, respectively. Two-photon pumped cavity lasing is also observed in an ASPT-doped polymer rod.

  4. Two-photon absorption induced drug delivery from polymeric intraocular lenses

    Science.gov (United States)

    Hampp, Norbert A.; Kim, Hee-Cheol; Kreiling, Stefan; Hesse, Lutz; Greiner, Andreas

    2003-10-01

    Secondary cataracts are quite often observed after implantation of polymeric intraocular lenses. The reason for this complication is that lens epithelial cells remain in the capsular bag when the natural lens is removed. They begin proliferation and cause secondary cataracts. It is not desireable to add cell toxic agents at the time of the implantation because wound healing is negatively affected. We have developed polymeric intraocular lenses which are equipped with a drug depot which may be released non-invasively through photochemical treatment. In the example presented the drug is 5-fluoruracil (5FU) which is covalently bound to the polymer. Deliberation of 5FU from the polymer is done photochemically. Since light is transmitted permanently through the artificial intraocular lens and wearing of special glasses by the patient should be omitted conventional photochemistry is not a suitable tool for the drug release. The polymer-5FU linkage is designed in a way that it has a high two-photon absorption cross-section. Two-photon absorption is used to selectively release 5FU from the lens. The one-photon reaction is blocked since the cornea does absorb UV light. The principle shown here is not limited to 5FU but may be applied to other drugs also.

  5. Measurement of degenerate two-photon absorption spectra of a series of developed two-photon initiators using a dispersive white light continuum Z-scan

    Science.gov (United States)

    Ajami, Aliasghar; Husinsky, Wolfgang; Tromayer, Maximilian; Gruber, Peter; Liska, Robert; Ovsianikov, Aleksandr

    2017-08-01

    To achieve efficient micro- and nanostructuring based on two-photon polymerization (2PP), the development and evaluation of specialized two-photon initiators (2PIs) are essential. Hence, a reliable method to determine the two-photon absorption (2PA) spectra of the synthesized 2PIs used for 2PP structuring is crucial. A technique by which absolute visible-to-near-infrared 2PA spectra of degenerate nature can be determined via performing a single dispersive white-light continuum (WLC) Z-scan has been realized. Using a dispersed white light beam containing 8 fs pulses at wavelengths ranging from 650 nm to 950 nm, the nonlinear transmittance as a function of the sample position can be measured for all spectral components by performing a single scan along the laser beam propagation direction. In this work, the 2PA spectrum of three different 2PIs was determined using this technique. 2PP structuring was also accomplished using the developed 2PIs at different wavelengths. Tuning the wavelength of the laser to match the peak of the 2PA spectra of the developed 2PIs resulted in lower intensity thresholds and facilitated higher structuring speeds. As an example, using M2CMK 2PI for 2PP, the scanning speed can be increased up to 5 folds when the laser wavelength is tuned to 760 nm (i.e., 2PA maximum) instead of the conventionally used 800 nm.

  6. Two-Photon-Absorption Induced Superradiance of a New Organic Dye PSPS

    Institute of Scientific and Technical Information of China (English)

    周广勇; 王东; 王筱梅; 杨胜军; 许心光; 赵显; 邵宗书; 蒋民华

    2002-01-01

    The linear and nonlinear optical properties of a new two-photon absorption (TPA) dye, trans-4-(4'-pyrrolidinyl styryl)-N-methyl pyridinium methyl sulfate (abbreviated as PSPS) is reported. Intense red superradiance with a peak located at 625nm can be observed from PSPS solution in benzyl alcohol when pumped by a focused picosecond laser beam operated at 1064nm. The lifetimes of one-photon absorption (OPA) and TPA fluorescence were measured to be 370 and 384ps, respectively. The pulse widths of OPA and TPA superradiance were 60 and 58 ps, respectively. The highest net upconversion efficiency from the absorbed pump laser to the upconverted superradiance is 8.3% at the pump energy of 0.6 mJ.

  7. Broadband Two-Photon Absorption Characteristics of Highly Photostable Fluorenyl-Dicyanoethylenylated [60]Fullerene Dyads

    Directory of Open Access Journals (Sweden)

    Seaho Jeon

    2016-05-01

    Full Text Available We synthesized four C60-(light-harvesting antenna dyads C60 (>CPAF-Cn (n = 4, 9, 12, or 18 1-Cn for the investigation of their broadband nonlinear absorption effect. Since we have previously demonstrated their high function as two-photon absorption (2PA materials at 1000 nm, a different 2PA wavelength of 780 nm was applied in the study. The combined data taken at two different wavelength ranges substantiated the broadband characteristics of 1-Cn. We proposed that the observed broadband absorptions may be attributed by a partial π-conjugation between the C60 > cage and CPAF-Cn moieties, via endinitrile tautomeric resonance, giving a resonance state with enhanced molecular conjugation. This transient state could increase its 2PA and excited-state absorption at 800 nm. In addition, a trend of concentration-dependent 2PA cross-section (σ2 and excited-state absorption magnitude was detected showing a higher σ value at a lower concentration that was correlated to increasing molecular separation with less aggregation for dyads C60(>CPAF-C18 and C60(>CPAF-C9, as better 2PA and excited-state absorbers.

  8. Molecular engineering of nanoscale quadrupolar chromophores for two-photon absorption

    Science.gov (United States)

    Porres, Laurent; Mongin, Olivier; Blanchard-Desce, Mireille H.; Ventelon, Lionel; Barzoukas, Marguerite; Moreaux, Laurent; Pons, Thomas; Mertz, Jerome

    2003-02-01

    Our aim has been the design of optimized NLO-phores with very high two-photon absorption (TPA) cross-sections (s2) in the red-NIR region, while maintaining high linear transparency and high fluorescence quantum yield. Our molecular engineering strategy is based on the push-push or pull-pull functionalization of semi-rigid nanoscale conjugated systems. The central building blocks were selected as rigid units that may assist quadrupolar intramolecular charge transfer by acting either as a (weak) donor or acceptor core. Quadrupolar molecules derived either from a phenyl unit, a rigidified biphenyl moiety or a fused bithiophene unit have been considered. Conjugated oligomers made of phenylene-vinylene and/or phenylene-ethynylene units were selected as connecting spacers between the core and the electroactive end groups to ensure effective electronic conjugation while maintaining suitable transparency/fluorescence. The TPA cross-sections were determined by investigating the two-photon-excited fluorescence properties using a Ti:sapphire laser delivering fs pulses. Both the nature of the end groups and of the core moiety play an important role in determining the TPA spectra. In addition, by adjusting the length and nature of the conjugated extensor, both amplification and spectral tuning of TPA cross-sections can be achieved. As a result, push-push fluorophores which demonstrate giant TPA cross-sections (up to 3000 GM) in the visible red, high fluorescence quantum yields and good transparency in the visible range have been obtained.

  9. Two-photon absorption-induced drug delivery from polymers for medical applications

    Science.gov (United States)

    Kim, Hee-Cheol; Kreiling, Stefan; Haertner, Sebastian; Hesse, Lutz; Greiner, Andreas; Hampp, Norbert A.

    2004-06-01

    Novel polymeric materials carrying a drug depot have been developed which are suitable for fabrication of photochemically modulated drug delivery devices. In order to avoid uncontrolled drug release the drug is covalently attached to the polymer backbone using a photo-active linker. Controlled drug release from the polymer can be accomplished either via single-photon excitation or by two-photon absorption (TPA). In particular the second possibility is of interest for applications where exposure to day light or UV light may not be omitted. One example are polymeric intraocular lenses (IOL), which are implanted instead of the opaque natural lens during cataract surgery. Secondary cataract formation is quite often observed after implantation of polymeric IOLs. In this study the well known cell toxic agent 5-fluorouracil (5FU) attached to a methylmethacrylate-based polymer was investigated as an IOL which can upon photochemical excitation release 5FU in order to treat or to prevent secondary cataract formation. The photochemical cleavage of the linker molecule was analyzed with single- and two-photon excitation. UV/VIS spectroscopy and HPLC analysis confirmed the release of 5FU form the polymer backbone. The diffusion of the drug precursor out from the polymer as well as the hydrolysis of the drug precursor which leads to 5FU formation were investigated in vitro.

  10. Numerical approaches for predicting two-photon absorption induced single-event effects in semiconductors

    Science.gov (United States)

    Hales, Joel M.; Khachatrian, Ani; Roche, Nicolas J.; Buchner, Stephen; Warner, Jeffrey; McMorrow, Dale

    2016-05-01

    Two numerical approaches for determining the charge generated in semiconductors via two-photon absorption (2PA) under conditions relevant for laser-based single-event effects (SEE) experiments are presented. The first approach uses a simple analytical expression incorporating a small number of experimental/material parameters while the second approach employs a comprehensive beam propagation method that accounts for all the complex nonlinear optical (NLO) interactions present. The impact of the excitation conditions, device geometry, and specific NLO interactions on the resulting collected charge in silicon devices is also discussed. These approaches can provide value to the radiation-effects community by predicting the impacts that varying experimental parameters will have on 2PA SEE measurements.

  11. Observation of two-photon absorption at UV radiation in ZnS quantum dots

    Indian Academy of Sciences (India)

    Manajit Chattopadhyay; Pathik Kumbhakar; Udit Chatterjee

    2014-02-01

    Research studies on quantum dots (QDs) of semiconductor materials are of potential interest in present days having promising applications in different optoelectronic devices. Among other materials, ZnS is a direct bandgap semiconductor material having a wide bandgap of 3.6 eV for its cubic phase at room temperature and it shows excellent optical properties. However, here the nonlinear optical (NLO) properties of chemically synthesized ZnS QDs of average size of ∼ 1.5 nm have been reported which are measured by using an indigenously developed Z-scan technique. The pump radiation is 355 nm which is the third harmonic of the Q-switched Nd:YAG laser radiation having pulsed duration of 10 ns with the repetition rate of 10 Hz. The measured experimental data have been analysed by using analytical models and two-photon absorption coefficients of the ZnS QDs at 355 nm have been extracted.

  12. Two-photon Absorption and Nonlinear Optical Properties of A New Organic Dye DEASPI

    Institute of Scientific and Technical Information of China (English)

    Guangyong ZHOU; Xiaomei WANG; Dong WANG; Chun WANG; Xian ZHAO; Zongshu SHAO; Minhua JIANG

    2001-01-01

    A new organic dye trans-4- [p-(N,N-diethylamino) styryl ]-N-methylpyridinium iodide (abbreviatedas DEASPI thereafter) with large two-photon absorption (TPA) cross section and excellent upconverted lasing properties was synthesized. The melting point and decompound point were measured to be 230℃ and 264.7℃ respectively. The molecular TPA cross section was meaThe linear and nonlinear optical properties of this dye were systematically studied. The highest net upconversion efficiency from the absorbed pump energy to the output upconverted lasing energy is as high as 18.6% at the pump energy of 2.17 mJ from a mode-locked Nd:YAG ps laser.The nonlinear transmittance at the wavelengths from 720 to 1100 nm was measured. The dye solution also shows a clear optical power limiting effect.

  13. Two-photon Absorption In Quantum Dots,quantum Dashes And Related Materials

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Ravinder

    2009-08-31

    We have proposed the use of USQDs for various deep-tissue biological imaging applications, notably wavelength-multiplexed multicolor imaging and intra-nuclear studies such as those involving cell apoptosis, and have studied the issue of maximizing two-photon absorption-induced fluorescence (TPAF) signals from CdSe/ZnS USQDs to be used for this application. In particular, using 2 nm USQDs, we have shown that the TPAF signal at 780 nm is ~ 8 times that at 850 nm and 68 times that at 900 nm, two wavelengths that have been used in previous studies using CdSe/ZnS SQDs for deep-tissue imaging of biological studies via TPAF .

  14. Theoretical studies on the one- and two-photon absorption properties of azulenylporphyrins and azulene-fused porphyrins

    Institute of Scientific and Technical Information of China (English)

    Li Wen-Chao; Feng Ji-Kang; Ren Ai-Min; Zhang Xiang-Biao; Sun Jia-Zhong

    2009-01-01

    The electronic structures, one-photon absorption (OPA) and two-photon absorption (TPA) properties of the azulenylporphyrins and azulene-fused porphyrins have been comparatively studied by using DFT/B3LYP/6-31G(d)and the ZINDO/SDCI method. With the number of azulenyl groups increasing, the OPA wavelengths of all molecules are red-shifted in 400-600 nm and the two-photon absorption cross section is gradually enlarged. The azulene-fused structures facilitate an expanding conjugated area and increasing TPA cross section. The origin of TPA properties of studied compounds is studied with a two-level model. In summary, the azulene-fused porphyrins exhibit strong two-photon absorption.

  15. Design, synthesis, and characterization of photoinitiators for two-photon polymerization

    Science.gov (United States)

    Whitby, Reece; MacMillan, Ryan; Janssens, Stefaan; Raymond, Sebastiampillai; Clarke, Dave; Kay, Andrew; Jin, Jianyong; Simpson, Cather M.

    2016-09-01

    A series of dipolar and quadrupolar two-photon absorption (2PA) photoinitiators (PIs) based around the well-known triphenylamine (TPA) core and tricyanofuran (TCF) acceptors have been prepared for use in two-photon polymerisation (TPP). The synthesised dipolar species are designated as 5 and 7, and the remaining quadrupolar species are 6, 8, 9 and 10. Large two-photon absorption cross-sections (δ2PA) ranging between 333 - 507 GM were measured at 780 nm using the z-scan technique. Fluorescence quantum yields (ΦF) were below 3% across the series when compared to Rhodamine 6G as a reference standard. Finally, TPP tests were conducted on PIs 7 and 8 to assess their ability to initiate the polymerisation of acrylate monomers using an 800 nm femtosecond Ti:Sapphire laser system.

  16. Acetylene bridged porphyrin-monophthalocyaninato ytterbium(III) hybrids with strong two-photon absorption and high singlet oxygen quantum yield.

    Science.gov (United States)

    Ke, Hanzhong; Li, Wenbin; Zhang, Tao; Zhu, Xunjin; Tam, Hoi-Lam; Hou, Anxin; Kwong, Daniel W J; Wong, Wai-Kwok

    2012-04-21

    Several acetylene bridged porphyrin-monophthalocyaninato ytterbium(III) hybrids, PZn-PcYb, PH(2)-PcYb and PPd-PcYb, have been prepared and characterized by (1)H and (31)P NMR, mass spectrometry, and UV-vis spectroscopy. Their photophysical and photochemical properties, especially the relative singlet oxygen ((1)O(2)) quantum yields and the two-photon absorption cross-section (σ(2)), were investigated. These three newly synthesized compounds exhibited very large σ(2) values and substantial (1)O(2) quantum yields upon photo-excitation, making them potential candidates as one- and two-photon photodynamic therapeutic agents.

  17. Pressure broadening of atomic oxygen two-photon absorption laser induced fluorescence

    Science.gov (United States)

    Marinov, Daniil; Drag, Cyril; Blondel, Christophe; Guaitella, Olivier; Golda, Judith; Klarenaar, Bart; Engeln, Richard; Schulz-von der Gathen, Volker; Booth, Jean-Paul

    2016-12-01

    Atomic oxygen, considered to be a determining reactant in plasma applications at ambient pressure, is routinely detected by two-photon absorption laser induced fluorescence (TALIF). Here, pressure broadening of the (2p 4 3 P 2  →  3p 3 P J=0,1,2) two-photon transition in oxygen atoms was investigated using a high-resolution TALIF technique in normal and Doppler-free configurations. The pressure broadening coefficients determined were {γ{{\\text{O}2}}}   =  0.40  ±  0.08  cm-1/bar for oxygen molecules and {γ\\text{He}}   =  0.46  ±  0.03 cm-1/bar for helium atoms. These correspond to pressure broadening rate constants k\\text{PB}{{\\text{O}2}}   =  9 · 10-9 cm3 s-1 and k\\text{PB}\\text{He}   =  4 · 10-9 cm3 s-1, respectively. The well-known quenching rate constants of O(3p 3 P J ) by O2 and He are at least one order of magnitude smaller, which signifies that non-quenching collisions constitute the main line-broadening mechanism. In addition to providing new insights into collisional processes of oxygen atoms in electronically excited 3p 3 P J state, reported pressure broadening parameters are important for quantification of oxygen TALIF line profiles when both collisional and Doppler broadening mechanisms are important. Thus, the Doppler component (and hence the temperature of oxygen atoms) can be accurately determined from high resolution TALIF measurements in a broad range of conditions.

  18. Theoretical Studies on the Third-order Nonlinear Optical Properties and Two-photon Absorption of Stilbene Derivatives

    Institute of Scientific and Technical Information of China (English)

    REN, Ai-Min(任爱民); FENG, Ji-Kang(封继康); LIU, Xiao-Juan(刘孝娟)

    2004-01-01

    Different types of stilbene derivatives (D-π-D, A-π-A, D-π-A) were investigated with AM1, and specially, equilibrium geometries of symmetrical stilbene derivatives (D-π-D) were studied using of PM3. With the same method INDO/CI, the UV-vis spectra were explored and the position and strength of the two-photon absorption were predicated by Sum-Over-States expression. The relationships of the structures, spectra and nonlinear optical properties have been examined. The influence of various substituents on two photon absorption cross-sections was discussed micromechanically.

  19. Polarization control efficiency manipulation in resonance-mediated two-photon absorption by femtosecond spectral frequency modulation

    Science.gov (United States)

    Yao, Yunhua; Cheng, Wenjing; Zheng, Ye; Xu, Cheng; Liu, Pei; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong; Zhang, Shian

    2017-04-01

    The femtosecond laser polarization modulation is considered as a very simple and efficient method to control the multi-photon absorption process. In this work, we theoretically and experimentally show that the polarization control efficiency in the resonance-mediated two-photon absorption can be artificially manipulated by modulating the femtosecond spectral frequency components. We theoretically demonstrate that the on- and near-resonant parts in the resonance-mediated two-photon absorption process depend on the different femtosecond spectral frequency components, and therefore their contributions in the whole excitation process can be controlled by properly designing the femtosecond spectral frequency components. The near-resonant two-photon absorption is correlated with the femtosecond laser polarization while the on-resonant two-photon absorption is independent of it, and thus the polarization control efficiency in the resonance-mediated two-photon absorption can be manipulated by the femtosecond spectral frequency modulation. We experimentally verify these theoretical results by performing the laser polarization control experiment in the Dy3+-doped glass sample under the modulated femtosecond spectral frequency components, and the experimental results show that the polarization control efficiency can be increased when the central spectral frequency components are cut off, while it is decreased when both the low and high spectral frequency components are cut off, which is in good agreement with the theoretical predictions. Our works can provide a feasible pathway to understand and control the resonance-mediated multi-photon absorption process under the femtosecond laser field excitation, and also may open a new opportunity to the related application areas.

  20. Enhancement of Two-photon Absorption in Quantum Wells for Extremely Nondegenerate Photon Pairs

    CERN Document Server

    Pattanaik, Himansu S; Khurgin, Jacob B; Hagan, David J; Van Stryland, Eric W

    2015-01-01

    We recently demonstrated orders of magnitude enhancement of two-photon absorption (2PA) in direct gap semiconductors due to intermediate state resonance enhancement for photons of very different energies. It can be expected that further enhancement of nondegenerate 2PA will be observed in quantum wells (QWs) since the intraband matrix elements do not vanish near the band center as they do in the bulk, and the density of states in QWs is larger near the band edge. Here we present a perturbation-theory based theoretical description of nondegenerate 2PA in semiconductor QWs, where both frequency and polarization of two incident waves can vary independently. Analytical expressions for all possible permutations of frequencies and polarizations have been obtained, and the results are compared with degenerate 2PA in quantum wells along with degenerate and nondegenerate 2PA in bulk semiconductors. We show that using QWs in place of bulk semiconductors with both beams in the TM-polarized mode leads to an additional or...

  1. Two-photon absorption-induced photoacoustic imaging of Rhodamine B dyed polyethylene spheres using a femtosecond laser.

    Science.gov (United States)

    Langer, Gregor; Bouchal, Klaus-Dieter; Grün, Hubert; Burgholzer, Peter; Berer, Thomas

    2013-09-23

    In the present paper we demonstrate the possibility to image dyed solids, i.e. Rhodamine B dyed polyethylene spheres, by means of two-photon absorption-induced photoacoustic scanning microscopy. A two-photon luminescence image is recorded simultaneously with the photoacoustic image and we show that location and size of the photoacoustic and luminescence image match. In the experiments photoacoustic signals and luminescence signals are generated by pulses from a femtosecond laser. Photoacoustic signals are acquired with a hydrophone; luminescence signals with a spectrometer or an avalanche photo diode. In addition we derive the expected dependencies between excitation intensity and photoacoustic signal for single-photon absorption, two-photon absorption and for the combination of both. In order to verify our setup and evaluation method the theoretical predictions are compared with experimental results for liquid and solid specimens, i.e. a carbon fiber, Rhodamine B solution, silicon, and Rhodamine B dyed microspheres. The results suggest that the photoacoustic signals from the Rhodamine B dyed microspheres do indeed stem from two-photon absorption.

  2. Experimental evidence and theoretical modeling of two-photon absorption dynamics in the reduction of intensity noise of solid-state Er:Yb lasers.

    Science.gov (United States)

    El Amili, Abdelkrim; Kervella, Gaël; Alouini, Mehdi

    2013-04-01

    A theoretical and experimental investigation of the intensity noise reduction induced by two-photon absorption in a Er,Yb:Glass laser is reported. The time response of the two-photon absorption mechanism is shown to play an important role on the behavior of the intensity noise spectrum of the laser. A model including an additional rate equation for the two-photon-absorption losses is developed and allows the experimental observations to be predicted.

  3. Off-Resonant Two-Photon Absorption Cross-Section Enhancement of an Organic Chromophore on Gold Nanorods

    Science.gov (United States)

    Sivapalan, Sean T.; Vella, Jarrett H.; Yang, Timothy K.; Dalton, Matthew J.; Haley, Joy E.; Cooper, Thomas M.; Urbas, Augustine M.; Tan, Loon-Seng; Murphy, Catherine J.

    2013-01-01

    Surface-plasmon-initiated interference effects of polyelectrolyte-coated gold nanorods on the two-photon absorption of an organic chromophore were investigated. With polyelectrolyte bearing gold nanorods of 2,4,6 and 8 layers, the role of the plasmonic fields as function of distance on such effects was examined. An unusual distance dependence was found: enhancements in the two-photon cross-section were at a minimum at an intermediate distance, then rose again at a further distance. The observed values of enhancement were compared to theoretical predictions using finite element analysis and showed good agreementdue to constructive and destructive interference effects. PMID:23687561

  4. Solvent and branching effect on the two-photon absorption properties of push-pull triphenylamine derivatives

    OpenAIRE

    Cvejn, Daniel; Michail, E.; Seintis, M.; Klikar, M.; Pytela, Oldřich; Mikysek, Tomáš; Almonasy, Numan; Ludwig, Miroslav; Giannetas, V.; Fakis, M.; Bureš, Filip

    2016-01-01

    The photophysical and two-photon absorption (2PA) properties of two tri-podal molecules and of their quadrupolar and dipolar counterparts are reported for a series of solvents with varying polarity. The molecules possess a tri-phenylamine electron donating group and mono-cyano acceptors while olefinic and acetylenic π-linkers have been used. Branching led to an increase of the molar extinction coefficient and to a slight bathochromic shift of the absorption spectra while the fluorescence quan...

  5. Optical control of cardiac cell excitability based on two-photon infrared absorption of AzoTAB

    CERN Document Server

    Shcherbakov, D; Erofeev, I; Astafiev, A

    2014-01-01

    Recent studies of AzoTAB activity in excitable cell cultures have shown that this substance is able to control excitability depending on isomer, cis or trans, predominating in the cellular membrane. Control of isomerization can be performed noninvasively by UV-visual radiation. At the same time it is well-known that azobenezenes can be effectively transformed from one isomer into another by two-photon absorption. Current work is devoted to the study of trans-AzoTAB two-photon transformation in aqueous solution and inside primal neonatal contractive rat cardiomyocytes. In accordance with results obtained Azo-TAB can be used as a probe for two-photon optical control of cardiac excitability.

  6. Simultaneous control of emission localization and two-photon absorption efficiency in dissymmetrical chromophores

    Energy Technology Data Exchange (ETDEWEB)

    Tretiak, Sergei [Los Alamos National Laboratory

    2009-01-01

    The aim of the present work is to demonstrate that combined spectral tuning of fluorescence and two-photon absorption (TPA) properties of multipolar chromophores can be achieved by introduction of slight electronic chemical dissymmetry. In that perspective, two novel series of structurally related chromophores have been designed and studied: a first series based on rod-like quadrupolar chromophores bearing different electron-donating (D) end groups and a second series based on three-branched octupolar chromophores built from a trigonal donating moiety and bearing various acceptor (A) peripheral groups. The influence of the electronic dissymmetry is investigated by combined experimental and theoretical studies of the linear and nonlinear optical properties of dissymmetric chromophores compared to their symmetrical counterparts. In both types of systems (i.e. quadrupoles and octupoles) experiments and theory reveal that excitation is essentially delocalized and that excitation involves synchronized charge redistribution between the different D and A moieties within the multipolar structure (i.e. concerted intramolecular charge transfer). In contrast, the emission stems only from a particular dipolar subunit bearing the strongest D or A moieties due to fast excitation localization after excitation prior to emission. Hence control of emission characteristics (polarization and emission spectrum) in addition to localization can be achieved by controlled introduction of electronic dissymmetry (i.e. replacement of one of the D or A end-groups by a slightly stronger D{prime} or A{prime} units). Interestingly dissymmetrical functionalization of both quadrupolar and octupolar compounds does not lead to significant loss in TPA responses and can even be beneficial due to the spectral broadening and peak position tuning that it allows. This study thus reveals an original molecular engineering route strategy allowing major TPA enhancement in multipolar structures due to concerted

  7. Selective Two-Photon-Absorption-Induced Reactions of Anthracene-2-Carboxylic Acid on Tunable Plasmonic Substrate with Incoherent Light Source.

    Science.gov (United States)

    Pincella, Francesca; Isozaki, Katsuhiro; Taguchi, Tomoya; Song, Yeji; Miki, Kazushi

    2015-02-01

    In this research, we report the development, characterization and application of various plasmonic substrates (with localized surface plasmon resonance wavelength tunable by gold nanoparticle size) for two-photon absorption (TPA)-induced photodimerization of an anthracene derivative, anthracene carboxylic acid, in both surface and solution phase under incoherent visible light irradiation. Despite the efficient photoreaction property of anthracene derivatives and the huge number of publications about them, there has never been a report of a multiphoton photoreaction involving an anthracene derivative with the exception of a reverse photoconversion of anthracene photodimer to monomer with three-photon absorption. We examined the progress of the TPA-induced photoreaction by means of surface-enhanced Raman scattering, taking advantage of the ability of our plasmonic substrate to enhance and localize both incident light for photoreaction and Raman scattering signal for analysis of photoreaction products. The TPA-induced photoreaction in the case of anthracene carboxylic acid coated 2D array of gold nanoparticles gave different results according to the properties of the plasmonic substrate, such as the size of the gold nanoparticle and also its resultant optical properties. In particular, a stringent requirement to achieve TPA-induced photodimerization was found to be the matching between irradiation wavelength, localized surface plasmon resonance of the 2D array, and twice the wavelength of the molecular excitation of the target material (in this case, anthracene carboxylic acid). These results will be useful for the future development of efficient plasmonic substrates for TPA-induced photoreactions with various materials.

  8. Two Photon Absorption Laser Induced Fluorescence for Neutral Hydrogen Profile Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Scime, Earl E. [West Virginia Univ., Morgantown, WV (United States)

    2016-09-23

    The magnitude and spatial dependence of neutral density in magnetic confinement fusion experiments is a key physical parameter, particularly in the plasma edge. Modeling codes require precise measurements of the neutral density to calculate charge-exchange power losses and drag forces on rotating plasmas. However, direct measurements of the neutral density are problematic. In this work, we proposed to construct a laser-based diagnostic capable of providing spatially resolved measurements of the neutral density in the edge of plasma in the DIII-D tokamak. The diagnostic concept is based on two-photon absorption laser induced fluorescence (TALIF). By injecting two beams of 205 nm light (co or counter propagating), ground state hydrogen (or deuterium or tritium) can be excited from the n = 1 level to the n = 3 level at the location where the two beams intersect. Individually, the beams experience no absorption, and therefore have no difficulty penetrating even dense plasmas. After excitation, a fraction of the hydrogen atoms decay from the n = 3 level to the n = 2 level and emit photons at 656 nm (the Hα line). Calculations based on the results of previous TALIF experiments in magnetic fusion devices indicated that a laser pulse energy of approximately 3 mJ delivered in 5 ns would provide sufficient signal-to-noise for detection of the fluorescence. In collaboration with the DIII-D engineering staff and experts in plasma edge diagnostics for DIII-D from Oak Ridge National Laboratory (ORNL), WVU researchers designed a TALIF system capable of providing spatially resolved measurements of neutral deuterium densities in the DIII-D edge plasma. The laser systems were specified, purchased, and assembled at WVU. The TALIF system was tested on a low-power hydrogen discharge at WVU and the plan was to move the instrument to DIII-D for installation in collaboration with ORNL researchers. After budget cuts at DIII-D, the DIII-D facility declined to support

  9. Temperature-dependent excitonic photoluminescence Excited by Two-Photon Absorption in Perovskite CsPbBr3 Quantum Dots

    CERN Document Server

    Wei, Ke; Xu, Zhongjie; Shen, Chao; Cheng, Xiangai; Jiang, Tian

    2016-01-01

    Recently lead halide nanocrystals (quantum dots) have been reported with potential for photovoltaic and optoelectronic applications due to their excellent luminescent properties. Herein excitonic photoluminescence (PL) excited by two-photon absorption in perovskite CsPbBr3 quantum dots (QDs) have been studied across a broad temperature range from 80K to 380K. Two-photon absorption has been investigated with absorption coefficient up to 0.085 cm/GW at room temperature. Moreover, the photoluminescence excited by two-photon absorption shows a linear blue-shift (0.25meV/K) below temperature of ~220K and turned steady with fluctuation below 1nm (4.4meV) for higher temperature up to 380K. These phenomena are distinctly different from general red-shift of semiconductor and can be explained by the competition between lattice expansion and electron-phonon couplling.Our results reveal the strong nonlinear absorption and temperature-independent chromaticity in a large temperature range from 220K to 380K in the CsPbX3 QD...

  10. Two-photon absorption of Tl1-xIn1-xSnxSe2 nanocrystallites

    Science.gov (United States)

    Myronchuk, Galyna; Parasyuk, Oleg; Piskach, Ludmila; Alzayed, Nasser Saleh; Prokhorenko, Serhii; Piasecki, Michal; Kityk, Iwan

    2016-12-01

    Novel materials for the infrared two-photon absorption — Tl1-xIn1-xSnxSe2 single crystals (x = 0.1,0.2) were grown. Two-photon absorption (TPA) was studied at CO2 laser wave-length 9.4μm with pulse duration 1μs. The studies were performed at different temperatures and for the nanocrystallite sizes varying within the 7-200 nm. The studies have shown that the TPA may be enhanced during the decrease of the nanocrystallite sizes below 50-60 nm. There exists also some critical x value at which the TPA value begin substantially to increase. The studied nanocrystallites are relatively stable to the infrared laser treatment and are not hygroscopic which allow to use them in different IR optoelectronic devices.

  11. Application of two-photon absorption in PWO scintillator for fast timing of interaction with ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Auffray, E. [CERN, Geneva (Switzerland); Buganov, O. [Stepanov Institute of Physics, Minsk (Belarus); Korjik, M.; Fedorov, A. [Research Institute for Nuclear Problems, Belarus State University, 11 Bobruiskaya, 220030 Minsk (Belarus); Nargelas, S.; Tamulaitis, G. [Semiconductor Physics Department and Institute of Applied Research, Vilnius University, Saulėtekio 9-III, LT-10222 Vilnius (Lithuania); Tikhomirov, S. [Stepanov Institute of Physics, Minsk (Belarus); Vaitkevičius, A., E-mail: augustas.vaitkevicius@ff.vu.lt [Semiconductor Physics Department and Institute of Applied Research, Vilnius University, Saulėtekio 9-III, LT-10222 Vilnius (Lithuania)

    2015-12-21

    This work was aimed at searching for fast phenomena in scintillators in sub-10-ps range, a benchmark timing for the time response of radiation detectors in particle colliders. The pump-and-probe optical absorption technique with a tunable-wavelength parametric oscillator as the pump and a continuous-spectrum source as the probe beam was used to study lead tungstate PbWO{sub 4} (PWO) single crystals. It is shown that the rise time of the probe pulse absorption induced by the pump pulse is shorter than the pump pulse width of 200 fs. The approximately linear dependence of the probe absorption on the pump pulse energy density evidences that the induced absorption is caused by two-photon absorption involving one probe and one pump photon. We demonstrate that the intensity of the induced absorption at certain wavelengths is influenced by gamma irradiation, provided that an appropriate light polarization is selected. The application of the irradiation-sensitive nonlinearity for fast timing in radiation detectors is discussed. - Highlights: • Nonlinear transmittance with femtosecond rise time is observed in PWO scintillators. • The nonlinearity is caused by two-photon absorption of pump and probe photons. • Gamma irradiation imposes change in the nonlinearity for certain light polarization. • Application of the nonlinearity for fast timing in radiation detectors is feasible.

  12. Evidence for strong electron correlations in graphene molecular fragments: Theory and experiments on two-photon absorptions

    Science.gov (United States)

    Aryanpour, Karan; Roberts, Adam; Sandhu, Arvinder; Shukla, Alok; Mazumdar, Sumit

    2013-03-01

    Historically, the occurrence of the lowest two-photon state below the optical one-photon state in linear polyenes, polyacetylenes and polydiacetylenes provided the strongest evidence for strong electron correlations in these linear π-conjugated systems. We demonstrate similar behavior in several molecular fragments of graphene with D6 h symmetry, theoretically and experimentally. Theoretically, we have calculated one versus two-photon absorptions in coronene, two different hexabenzocoronenes and circumcoronene, within the Pariser-Parr-Pople π-electron Hamiltonian using high order configuration interaction. Experimentally, we have performed z-scan measurements using a white light super-continuum source on coronene and hexa-peri-hexabenzocoronene to determine frequency-dependent two-photon absorption coefficients, for comparison to the ground state absorptions. Excellent agreement between experiment and theory in our work gives strong evidence for significant electron correlations between the π-electrons in the graphene molecular fragments. We particularly benchmark high order electron-hole excitations in graphene fragments as a key element behind the agreement between theory and experiment in this work. We acknowledge NSF-CHE-1151475 grant as our funding source.

  13. Synthesis and two-photon absorption property of new -conjugated donor-acceptor polymers carrying different heteroaromatics

    Indian Academy of Sciences (India)

    M S Sunitha; K A Vishnumurthy; A V Adhikari

    2013-01-01

    In this communication, we report the synthesis of three newly designed fluorescent polymers P1-P3, starting from simple thiophene derivatives through precursor polyhydrazide route. The new polymers, carrying donor and acceptor heterocyclic moieties with different spacer groups were found to be thermally stable and good of nonlinear optical (NLO) materials with two photon absorption property. The structures of newly synthesized monomers and polymers were confirmed by FTIR, NMR spectral and elemental analyses. Further, polymers were characterized by GPC and TGA studies. Their linear optical and electrochemical properties were evaluated by UV-vis, fluorescence spectroscopic and cyclic voltammetric (CV) studies, respectively, whereas their NLO properties were studied by Z-scan technique using Nd: YAG laser at 532 nm with 7 ns pulse. The electrochemical band gap of P1-P3 was determined to be 1.98, 1.91 and 2.05 eV, respectively. The NLO results reveal that polymers P1-P3 show good optical limiting property with TPA coefficient values 2.9 × 10−11 m/W, 8.0 × 10−11 m/W and 1.4 × 10−11 m/W, respectively.

  14. Autocorrelation measurement of femtosecond laser pulses based on two-photon absorption in GaP photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Chong, E. Z.; Watson, T. F.; Festy, F., E-mail: frederic.festy@kcl.ac.uk [Biomaterials, Biomimetics and Biophotonics Division, King' s College London—Dental Institute, SE1 9RT London (United Kingdom)

    2014-08-11

    Semiconductor materials which exhibit two-photon absorption characteristic within a spectral region of interest can be useful in building an ultra-compact interferometric autocorrelator. In this paper, we report on the evidence of a nonlinear absorption process in GaP photodiodes which was exploited to measure the temporal profile of femtosecond Ti:sapphire laser pulses with a tunable peak wavelength above 680 nm. The two-photon mediated conductivity measurements were performed at an average laser power of less than a few tenths of milliwatts. Its suitability as a single detector in a broadband autocorrelator setup was assessed by investigating the nonlinear spectral sensitivity bandwidth of a GaP photodiode. The highly favourable nonlinear response was found to cover the entire tuning range of our Ti:sapphire laser and can potentially be extended to wavelengths below 680 nm. We also demonstrated the flexibility of GaP in determining the optimum compensation value of the group delay dispersion required to restore the positively chirped pulses inherent in our experimental optical system to the shortest pulse width possible. With the rise in the popularity of nonlinear microscopy, the broad two-photon response of GaP and the simplicity of this technique can provide an alternative way of measuring the excitation laser pulse duration at the focal point of any microscopy systems.

  15. Selective Two-Photon Absorptive Resonance Femtosecond-Laser Electronic-Excitation Tagging (STARFLEET) Velocimetry in Flow and Combustion Diagnostics

    Science.gov (United States)

    Jiang, Naibo; Halls, Benjamin R.; Stauffer, Hans U.; Roy, Sukesh; Danehy, Paul M.; Gord, James R.

    2016-01-01

    Selective Two-Photon Absorptive Resonance Femtosecond-Laser Electronic-Excitation Tagging (STARFLEET), a non-seeded ultrafast-laser-based velocimetry technique, is demonstrated in reactive and non-reactive flows. STARFLEET is pumped via a two-photon resonance in N2 using 202.25-nm 100-fs light. STARFLEET greatly reduces the per-pulse energy required (30 µJ/pulse) to generate the signature FLEET emission compared to the conventional FLEET technique (1.1 mJ/pulse). This reduction in laser energy results in less energy deposited in the flow, which allows for reduced flow perturbations (reactive and non-reactive), increased thermometric accuracy, and less severe damage to materials. Velocity measurements conducted in a free jet of N2 and in a premixed flame show good agreement with theoretical velocities and further demonstrate the significantly less-intrusive nature of STARFLEET.

  16. Theoretical investigation of one-photon and two-photon absorption properties for multiply N-confused porphyrins.

    Science.gov (United States)

    Yang, Zhao-Di; Feng, Ji-Kang; Ren, Ai-Min; Sun, Chia-Chung

    2006-12-28

    We have theoretically investigated a series of multiply N-confused porphyrins and their Zn or Cu complexes for the first time by using DFT(B3LYP/6-31G*) and ZINDO/SOS methods. The electronic structure, one-photon absorption (OPA), and two-photon absorption (TPA) properties have been studied in detail. The calculated results indicate that the OPA spectra of multiply N-confused porphyrins are red-shifted and the OPA intensities decrease compared to normal porphyrin. The maximum two photon absorption wavelengths lambda(max) are blue-shifted and the TPA cross sections delta(max) are increased 22.7-112.1 GM when the N atoms one by one are inverted from core to beta position to form multiply N-confused porphyrins. Especially delta(max) of N3CP get to 164.7 GM. The electron donors -C6F5s at meso-position can make the TPA cross section delta(max) increase. After forming metal complexes with Cu or Zn, the TPA properties of multiply N-confused porphyrins are further increased except for N3CP, N4CP. Our theoretical findings demonstrate that the multiply N-confused prophyrins as well as their metal complexes and derivatives are promising molecules that can be assembled series of materials with large TPA cross section, and are sure to be the subject of further investigation.

  17. Nonlinear two-photon absorption properties induced by femtosecond laser with the films of two novel anthracene derivatives

    Institute of Scientific and Technical Information of China (English)

    Liang Li; Yiqun Wu; Yang Wang

    2012-01-01

    Two novel anthracene derivatives containing 4-vinylpyridine (FPEA) and 2-vinylpyridine (TPEA) poly(methyl methacrylate) films are prepared on quartz glass substrates.Their nonlinear absorption properties are investigated by using a 120-fs,800-am Ti:sapphire femtosecond pulsed laser operating at a 1-kHz repetition rate.The unique nonlinear absorption properties of these new compounds are observed by utilizing a Z-scan system.These two-photon absorption (TPA) properties are proven by the two-photon fluorescence excited at 800 nm.The FPEA and TPEA films have nonlinear TPA coefficients of 0.164 and 0.148 cm/GW and the TPA cross sections of 3.345 × 10-48 and 3.081 × 10-48 cm4.s/photon,respectively.The influence of the chemical structures on the nonlinear TPA properties of the compounds is also discussed.The highly nonlinear TPA activities of the films implied that the new anthracene derivatives are suitable materials with promising applications in super-high-density three-dimensional data storage and nano- or microstructure fabrication.

  18. Giant Two-Photon Absorption Coefficient and Frequency Up-Converted Luminescence in Monolayer MoS2

    CERN Document Server

    Li, Yuanxin; Zhang, Saifeng; Zhang, Xiaoyan; Feng, Yanyan; Wang, Kangpeng; Zhang, Long; Wang, Jun

    2015-01-01

    Strong two-photon absorption (TPA) in monolayer MoS2 is demonstrated in contrast to saturable absorption (SA) in multilayer MoS2 under the excitation of femtosecond laser pulses in the near infrared region. MoS2 in the forms of monolayer single crystal and multilayer triangular islands are grown on either quartz or SiO2/Si by employing the seeding method through chemistry vapor deposition. The nonlinear transmission measurements reveal that monolayer MoS2 possesses a giant nonsaturation TPA coefficient, larger than that of conventional semiconductors. As a result of TPA, two-photon pumped frequency up-converted luminescence is observed directly in the monolayer MoS2. For the multilayer MoS2, the SA response is demonstrated with the ratio of the excited-state absorption cross section to ground-state cross section of 0.18. In addition, the laser damage threshold of the monolayer MoS2 is 97 GW/cm2, larger than that of the multilayer MoS2 of 78 GW/cm2.

  19. Theoretical study relating the two-photon absorption cross section to the susceptibility controlling four-wave mixing

    Science.gov (United States)

    Burris, J.; Mcilrath, T. J.

    1985-01-01

    A theory that it is necessary to extract a two-photon absorption cross section from a mixing signal is developed. The dependence of the cross section on the third-order susceptibility is shown and both the mixing signal and reference signal dependences on the susceptibility are given. Techniques to process the measured value of the susceptibility and relate it to the cross section are developed and limits of validity are established. Finally, a comparison is made between the expression for the cross section presently reported and values given elsewhere.

  20. Theoretical Studies on the One- and Two-Photon Absorption Properties of Double-bis(styryl)benzene Derivatives

    Institute of Scientific and Technical Information of China (English)

    HAN,De-Ming; FENG,Ji-Kang; REN,Ai-Min; SHANG,Xiao-Hong; ZHANG,Xiang-Biao; MA,Yu-Guang; HE,Feng

    2008-01-01

    Two series of bis(styryl)benzene derivatives (BSBD), namely the single-BSBD and the double-BSBD, were investigated. The equilibrium geometries and electronic structures were obtained by using the density functional theory B3LYP and 6-31G basis set. In succession, the one- and two-photon absorption properties of all the molecules were studied theoretically with a ZINDO-SOS (sum-over-states) method in detail. It can be seen that the double-BSBDs have larger two-photon absorption (TPA) cross sections in the visible-IR range than the corresponding single-BSBDs,demonstrating that increasing the molecular dimension is a very effective method to enhance the values of the TPA cross sections. On the other hand, it can be also noticed that the values of the TPA cross sections are correlative with the ability of donating (accepting) electrons of the terminal substituent groups R[N(CH3)2, CH3, H and CF3] in these molecules. That is, the intramolecular charge transfer is also a factor for the enhancement of the TPA efficiency. To sum up, the idea of increasing the molecular dimension to enhance the TPA cross section value is a helpful direction to explore better TPA materials for practical applications. And the double-BSBD molecules are promising TPA materials for the further investigation from the standpoint of the high transparency and the larger TPA cross sections.

  1. Lighting the Way to See Inside Two-Photon Absorption Materials: Structure-Property Relationship and Biological Imaging.

    Science.gov (United States)

    Zhang, Qiong; Tian, Xiaohe; Zhou, Hongping; Wu, Jieying; Tian, Yupeng

    2017-02-23

    The application of two-photon absorption (2PA) materials is a classical research field and has recently attracted increasing interest. It has generated a demand for new dyes with high 2PA cross-sections. In this short review, we briefly cover the structure-2PA property relationships of organic fluorophores, organic-inorganic nanohybrids and metal complexes explored by our group. (1) The two-photon absorption cross-section (δ) of organic fluorophores increases with the extent of charge transfer, which is important to optimize the core, donor-acceptor pair, and conjugation-bridge to obtain a large δ value. Among the various cores, triphenylamine appears to be an efficient core. Lengthening of the conjugation with styryl groups in the D-π-D quadrupoles and D-π-A dipoles increased δ over a long wavelength range than when vinylene groups were used. Large values of δ were observed for extended conjugation length and moderate donor-acceptors in the near-IR wavelengths. The δ value of the three-arm octupole is larger than that of the individual arm, if the core has electron accepting groups that allow significant electronic coupling between the arms; (2) Optical functional organic/inorganic hybrid materials usually show high thermal stability and excellent optical activity; therefore the design of functional organic molecules to build functional organic-inorganic hybrids and optimize the 2PA properties are significant. Advances have been made in the design of organic-inorganic nanohybrid materials of different sizes and shapes for 2PA property, which provide useful examples to illustrate the new features of the 2PA response in comparison to the more thoroughly investigated donor-acceptor based organic compounds and inorganic components; (3) Metal complexes are of particular interest for the design of new materials with large 2PA ability. They offer a wide range of metals with different ligands, which can give rise to tunable electronic and 2PA properties. The metal

  2. Lighting the Way to See Inside Two-Photon Absorption Materials: Structure–Property Relationship and Biological Imaging

    Science.gov (United States)

    Zhang, Qiong; Tian, Xiaohe; Zhou, Hongping; Wu, Jieying; Tian, Yupeng

    2017-01-01

    The application of two-photon absorption (2PA) materials is a classical research field and has recently attracted increasing interest. It has generated a demand for new dyes with high 2PA cross-sections. In this short review, we briefly cover the structure-2PA property relationships of organic fluorophores, organic-inorganic nanohybrids and metal complexes explored by our group. (1) The two-photon absorption cross-section (δ) of organic fluorophores increases with the extent of charge transfer, which is important to optimize the core, donor-acceptor pair, and conjugation-bridge to obtain a large δ value. Among the various cores, triphenylamine appears to be an efficient core. Lengthening of the conjugation with styryl groups in the D-π-D quadrupoles and D-π-A dipoles increased δ over a long wavelength range than when vinylene groups were used. Large values of δ were observed for extended conjugation length and moderate donor-acceptors in the near-IR wavelengths. The δ value of the three-arm octupole is larger than that of the individual arm, if the core has electron accepting groups that allow significant electronic coupling between the arms; (2) Optical functional organic/inorganic hybrid materials usually show high thermal stability and excellent optical activity; therefore the design of functional organic molecules to build functional organic-inorganic hybrids and optimize the 2PA properties are significant. Advances have been made in the design of organic-inorganic nanohybrid materials of different sizes and shapes for 2PA property, which provide useful examples to illustrate the new features of the 2PA response in comparison to the more thoroughly investigated donor-acceptor based organic compounds and inorganic components; (3) Metal complexes are of particular interest for the design of new materials with large 2PA ability. They offer a wide range of metals with different ligands, which can give rise to tunable electronic and 2PA properties. The metal

  3. Lighting the Way to See Inside Two-Photon Absorption Materials: Structure–Property Relationship and Biological Imaging

    Directory of Open Access Journals (Sweden)

    Qiong Zhang

    2017-02-01

    Full Text Available The application of two-photon absorption (2PA materials is a classical research field and has recently attracted increasing interest. It has generated a demand for new dyes with high 2PA cross-sections. In this short review, we briefly cover the structure-2PA property relationships of organic fluorophores, organic-inorganic nanohybrids and metal complexes explored by our group. (1 The two-photon absorption cross-section (δ of organic fluorophores increases with the extent of charge transfer, which is important to optimize the core, donor-acceptor pair, and conjugation-bridge to obtain a large δ value. Among the various cores, triphenylamine appears to be an efficient core. Lengthening of the conjugation with styryl groups in the D-π-D quadrupoles and D-π-A dipoles increased δ over a long wavelength range than when vinylene groups were used. Large values of δ were observed for extended conjugation length and moderate donor-acceptors in the near-IR wavelengths. The δ value of the three-arm octupole is larger than that of the individual arm, if the core has electron accepting groups that allow significant electronic coupling between the arms; (2 Optical functional organic/inorganic hybrid materials usually show high thermal stability and excellent optical activity; therefore the design of functional organic molecules to build functional organic-inorganic hybrids and optimize the 2PA properties are significant. Advances have been made in the design of organic-inorganic nanohybrid materials of different sizes and shapes for 2PA property, which provide useful examples to illustrate the new features of the 2PA response in comparison to the more thoroughly investigated donor-acceptor based organic compounds and inorganic components; (3 Metal complexes are of particular interest for the design of new materials with large 2PA ability. They offer a wide range of metals with different ligands, which can give rise to tunable electronic and 2PA

  4. Effects of two-photon absorption on terahertz radiation generated by femtosecond-laser excited photoconductive antennas.

    Science.gov (United States)

    Lee, Chao-Kuei; Yang, Chan-Shan; Lin, Sung-Hui; Huang, Shiuan-Hua; Wada, Osamu; Pan, Ci-Ling

    2011-11-21

    Terahertz (THz) radiation can be generated more efficiently from a low-temperature-grown GaAs (LT-GaAs) photoconductive (PC) antenna by considering the two-photon absorption (TPA) induced photo-carrier in the photoconductor. A rate-equation-based approach using the Drude-Lorentz model taking into account the band-diagram of LT-GaAs is used for the theoretical analysis. The use of transform-limited pulses at the PC antenna is critical experimentally. Previously unnoticed THz pulse features and anomalously increasing THz radiation power rather than saturation were observed. These are in good agreement with the theoretical predictions. The interplay of intensity dependence and dynamics of generation of photoexcited carriers by single-photon absorption and TPA for THz emission is discussed.

  5. Two photon absorption and its saturation of WS2 and MoS2 monolayer and few-layer films

    CERN Document Server

    Zhang, Saifeng; McEvoy, Niall; O'Brien, Maria; Winters, Sinéad; Berner, Nina C; Yim, Chanyoung; Zhang, Xiaoyan; Chen, Zhanghai; Zhang, Long; Duesberg, Georg S; Wang, Jun

    2015-01-01

    The optical nonlinearity of WS2, MoS2 monolayer and few-layer films was investigated using the Z-scan technique with femtosecond pulses from the visible to the near infrared. The dependence of nonlinear absorption of the WS2 and MoS2 films on layer number and excitation wavelength was studied systematically. WS2 with 1~3 layers exhibits a giant two-photon absorption (TPA) coefficient. Saturation of TPA for WS2 with 1~3 layers and MoS2 with 25~27 layers was observed. The giant nonlinearity of WS2 and MoS2 is attributed to two dimensional confinement, a giant exciton effect and the band edge resonance of TPA.

  6. Difluorenyl carbo-Benzenes: Synthesis, Electronic Structure, and Two-Photon Absorption Properties of Hydrocarbon Quadrupolar Chromophores.

    Science.gov (United States)

    Baglai, Iaroslav; de Anda-Villa, Manuel; Barba-Barba, Rodrigo M; Poidevin, Corentin; Ramos-Ortíz, Gabriel; Maraval, Valérie; Lepetit, Christine; Saffon-Merceron, Nathalie; Maldonado, José-Luis; Chauvin, Remi

    2015-09-28

    The synthesis, crystal and electronic structures, and one- and two-photon absorption properties of two quadrupolar fluorenyl-substituted tetraphenyl carbo-benzenes are described. These all-hydrocarbon chromophores, differing in the nature of the linkers between the fluorenyl substituents and the carbo-benzene core (C-C bonds for 3 a, C-C=C-C expanders for 3 b), exhibit quasi-superimposable one-photon absorption (1PA) spectra but different two-photon absorption (2PA) cross-sections σ2PA. Z-scan measurements (under NIR femtosecond excitation) indeed showed that the C≡C expansion results in an approximately twofold increase in the σ2PA value, from 336 to 656 GM (1 GM = 10(-50) cm(4) s molecule(-1) photon(-1)) at λ = 800 nm. The first excited states of Au and Ag symmetry accounting for 1PA and 2PA, respectively, were calculated at the TDDFT level of theory and used for sum-over-state estimations of σ2PA(λi), in which λi = 2 hc/Ei, h is Planck's constant, c is the speed of light, and Ei is the energy of the 2PA-allowed transition. The calculated σ2PA values of 227 GM at 687 nm for 3 a and 349 GM at 708 nm for 3 b are in agreement with the Z-scan results.

  7. Two-photon absorption and efficient encapsulation of near-infrared-emitting CdSe{sub x}Te{sub 1−x} quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Szeremeta, Janusz [Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Lamch, Lukasz [Department of Organic and Pharmaceutical Technology, Faculty of Chemistry, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Wawrzynczyk, Dominika [Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Wilk, Kazimiera A. [Department of Organic and Pharmaceutical Technology, Faculty of Chemistry, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Samoc, Marek [Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Nyk, Marcin, E-mail: marcin.nyk@pwr.edu.pl [Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland)

    2015-07-29

    Highlights: • Synthesis of the IR emitting alloyed CdSe{sub x}Te{sub 1−x} quantum dots has been performed. • Two-photon absorption cross section of the CdSe{sub x}Te{sub 1−x} QDs was measured in the IR range. • The QDs were encapsulated into Brij 58® micelles and transferred to the aqueous environment. • A blue-shift of fluorescence of QDs in the micelles was observed. - Abstract: Hydrophobic CdSe{sub x}Te{sub 1−x} quantum dots with near infrared emission in the 700–750 nm range were synthesized by a wet chemistry technique. Their nonlinear optical properties were studied using Z-scan technique with a tunable femtosecond laser system. The peak value of the two-photon absorption cross section was found to be ∼2400 GM at 1400 nm. To demonstrate a possible way of utilizing the CdSe{sub x}Te{sub 1−x} quantum dots in aqueous environment we describe here a convenient method of preparation of Brij 58® micellar systems loaded with the quantum dots. The obtained nanoconstructs were characterized using optical spectroscopy, TEM and DLS. The micelles colloidal stability, and the influence of the encapsulation process on the spectroscopic properties of the quantum dots are discussed. In particular, we have observed a 60 nm blue-shift of the emission maxima upon loading quantum dots inside the micelles.

  8. Two-photon absorption laser induced fluorescence measurement of atomic oxygen density in an air atmospheric pressure plasma jet

    Science.gov (United States)

    Conway, Jim; Gogna, Gurusharan; Daniels, Stephen

    2016-09-01

    Two-photon Absorption Laser Induced Fluorescence (TALIF) is used to measure atomic oxygen number density [O] in an air Atmospheric Pressure Plasma Jet (APPJ). A novel technique based on photolysis of O2 is used to calibrate the TALIF system ensuring the same species (O) is probed during calibration and measurement. As a result, laser intensity can be increased outside the TALIF quadratic laser power region without affecting calibration reliability as any high intensity saturation effects will be identical for calibration and experiment. Higher laser intensity gives stronger TALIF signals helping overcome weak TALIF signals often experienced at atmospheric pressure due to collisional quenching. O2 photo-dissociation and two-photon excitation of the resulting [O] are both achieved within the same laser pulse. The photolysis [O] is spatially non-uniform and time varying. To allow valid comparison with [O] in a plasma, spatial and temporal correction factors are required. Knowledge of the laser pulse intensity I0(t), and wavelength allows correction factors to be found using a rate equation model. The air flow into the jet was fixed and the RF power coupled into the system varied. The resulting [O] was found to increase with RF power.

  9. Development of an automated two-photon absorption cross section spectrometer%双光子吸收截面自动化测量系统研究

    Institute of Scientific and Technical Information of China (English)

    屈军乐; 周藩; 邵永红; 张新富; 仉华; 姜娜; 彭孝军; 肖义

    2013-01-01

    为快速精确测量双光子材料的吸收截面,研究制作了一套基于双光子诱导荧光法的自动化双光子吸收截面谱仪.该系统基于虚拟仪器平台,实现了功率实时反馈、步进电机同步控制、荧光光谱快速采集、线性分析和双光子吸收光谱分析等功能,是集功率反馈控制到光谱采集、处理为一体的软件自动化操作平台,是研究双光子吸收截面的实用工具.%Two-photon absorption cross section is an important property of organic two-photon fluorophores and is critical to the study of two-photon materials. In order to measure two-photon absorption cross section quickly and accurately, we developed an automated two-photon absorption spectrometer that is based on two-photon induced fluorescence method. The system can perform the functions of real-time feedback of power, stepper motor synchronous control, fast acquisition of fluorescence spectra, linear analysis and two-photon absorption spectroscopy analysis using a virtual instrument platform. The system has an integrated and automated software platform for power feedback control, spectra acquisition and data processing. It can function as an important tool in the study of two-photon absorption cross section of fluorophores

  10. New insights into two-photon absorption properties of functionalized aza-BODIPY dyes at telecommunication wavelengths: a theoretical study.

    Science.gov (United States)

    Liu, Xiaoting; Zhang, Jilong; Li, Kai; Sun, Xiaobo; Wu, Zhijian; Ren, Aimin; Feng, Jikang

    2013-04-01

    Special attention has been paid to understanding the structural effect on electronic structure and absorption spectra for an extensive series of functionalized aza-BODIPY molecules. We have employed the quadratic response theory as well as a sum-over-states approach involving few intermediate states to calculate the two-photon cross section (δmax). The results suggest that chemical modifications on the aza-BODIPY core and peripheral moieties using various substituents can finely tune their linear and nonlinear optical properties. Therefore, some new fluorophores absorbing in the near infrared region and featuring considerably high δmax at telecommunication wavelengths are proposed, which are excellent candidates for nonlinear transmission and fluorescent labeling materials. The investigation contributes a useful starting point for further design of more effective aza-BODIPY dyes and can be valuable as a foundation for future experimental research and development.

  11. Resonant metallic nanostructure for enhanced two-photon absorption in a thin GaAs p-i-n diode

    Energy Technology Data Exchange (ETDEWEB)

    Portier, Benjamin; Pardo, Fabrice; Péré-Laperne, Nicolas; Steveler, Emilie; Dupuis, Christophe; Bardou, Nathalie; Lemaître, Aristide; Pelouard, Jean-Luc, E-mail: jean-luc.pelouard@lpn.cnrs.fr [Laboratoire de Photonique et de Nanostructures (LPN-CNRS), Route de Nozay, 91460 Marcoussis (France); Vest, Benjamin; Jaeck, Julien; Rosencher, Emmanuel [ONERA The French Aerospace Lab, Chemin de la Hunière, F-91760 Palaiseau (France); Haïdar, Riad [ONERA The French Aerospace Lab, Chemin de la Hunière, F-91760 Palaiseau (France); École Polytechnique, Département de Physique, F-91128 Palaiseau (France)

    2014-07-07

    Degenerate two-photon absorption (TPA) is investigated in a 186 nm thick gallium arsenide (GaAs) p-i-n diode embedded in a resonant metallic nanostructure. The full device consists in the GaAs layer, a gold subwavelength grating on the illuminated side, and a gold mirror on the opposite side. For TM-polarized light, the structure exhibits a resonance close to 1.47 μm, with a confined electric field in the intrinsic region, far from the metallic interfaces. A 109 times increase in photocurrent compared to a non-resonant device is obtained experimentally, while numerical simulations suggest that both gain in TPA-photocurrent and angular dependence can be further improved. For optimized grating parameters, a maximum gain of 241 is demonstrated numerically and over incidence angle range of (−30°; +30°).

  12. Entangled two photon absorption cross section on the 808 nm region for the common dyes Zinc tetraphenylporphyrin and Rhodamine B

    CERN Document Server

    Villabona-Monsalve, Juan P; Portela, Mayerlin Nuñez; Valencia, Alejandra

    2016-01-01

    We report the measurement of the entangled two photon absorption cross section, $\\sigma_E$, at 808 nm on organic chromophores in solution in a low photon flux regime. We performed measurements on Zinc tetraphenylporphyrin (ZnTPP) in Toluene and Rhodamine B (RhB) in Methanol. This is, to the best of our knowledge, the first time that $\\sigma_E$ is measured for RhB. Additionally, we report a systematic study of the dependence of $\\sigma_E$ on the molecular concentration for both molecular systems. In contrast to previous experiments, our measurements are based on detecting the pairs of photons that are transmitted by the molecular system. By using a coincidence count circuit it was possible to improve the signal to noise ratio. This type of work is important for the development of spectroscopic and microscopic techniques using entangled photons.

  13. Enhancement of two photon absorption with Ni doping in the dilute magnetic semiconductor ZnO crystalline nanorods

    Science.gov (United States)

    Rana, Amit Kumar; J, Aneesh; Kumar, Yogendra; M. S, Arjunan; Adarsh, K. V.; Sen, Somaditya; Shirage, Parasharam M.

    2015-12-01

    In this letter, we have investigated the third-order optical nonlinearities of high-quality Ni doped ZnO nanorods crystallized in wurtzite lattice, prepared by the wet chemical method. In our experiments, we found that the two photon absorption coefficient (β) increases by as much as 14 times, i.e., 7.6 ± 0.4 to 112 ± 6 cm/GW, when the Ni doping is increased from 0% to 10%. The substantial enhancement in β is discussed in terms of the bandgap scaling and Ni doping. Furthermore, we also show that the optical bandgap measured by UV-Vis and photoluminescence spectroscopies, continuously redshift with increasing Ni doping concentration. We envision that the strong nonlinear optical properties together with their dilute magnetic effects, they form an important class of materials for potential applications in magneto-optical and integrated optical chips.

  14. Enhancement of two photon absorption with Ni doping in the dilute magnetic semiconductor ZnO crystalline nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Rana, Amit Kumar; Kumar, Yogendra; Arjunan, M.S.; Sen, Somaditya; Shirage, Parasharam M., E-mail: pmshirage@iiti.ac.in, E-mail: paras.shirage@gmail.com [Department of Physics, Indian Institute of Technology Indore, Simrol Campus, Khandwa Road, Indore 452020 (India); Centre of Materials Science and Engineering, Indian Institute of Technology Indore, Simrol Campus, Khandwa Road, Indore 452020 (India); J, Aneesh; Adarsh, K. V. [Department of Physics, Indian Institute of Science Education and Research, Bhopal 462023 (India)

    2015-12-07

    In this letter, we have investigated the third-order optical nonlinearities of high-quality Ni doped ZnO nanorods crystallized in wurtzite lattice, prepared by the wet chemical method. In our experiments, we found that the two photon absorption coefficient (β) increases by as much as 14 times, i.e., 7.6 ± 0.4 to 112 ± 6 cm/GW, when the Ni doping is increased from 0% to 10%. The substantial enhancement in β is discussed in terms of the bandgap scaling and Ni doping. Furthermore, we also show that the optical bandgap measured by UV-Vis and photoluminescence spectroscopies, continuously redshift with increasing Ni doping concentration. We envision that the strong nonlinear optical properties together with their dilute magnetic effects, they form an important class of materials for potential applications in magneto-optical and integrated optical chips.

  15. High-accuracy reference standards for two-photon absorption in the 680-1050 nm wavelength range.

    Science.gov (United States)

    de Reguardati, Sophie; Pahapill, Juri; Mikhailov, Alexander; Stepanenko, Yuriy; Rebane, Aleksander

    2016-04-18

    Degenerate two-photon absorption (2PA) of a series of organic fluorophores is measured using femtosecond fluorescence excitation method in the wavelength range, λ2PA = 680-1050 nm, and ~100 MHz pulse repetition rate. The function of relative 2PA spectral shape is obtained with estimated accuracy 5%, and the absolute 2PA cross section is measured at selected wavelengths with the accuracy 8%. Significant improvement of the accuracy is achieved by means of rigorous evaluation of the quadratic dependence of the fluorescence signal on the incident photon flux in the whole wavelength range, by comparing results obtained from two independent experiments, as well as due to meticulous evaluation of critical experimental parameters, including the excitation spatial- and temporal pulse shape, laser power and sample geometry. Application of the reference standards in nonlinear transmittance measurements is discussed.

  16. Two-photon absorption, nonlinear optical and UV-vis spectral properties of 2-furanylmethyleneaminoantipyrine, benzylideneaminoantipyrine and cinnamilideneaminoantipyrine

    Energy Technology Data Exchange (ETDEWEB)

    Sun Yuxi, E-mail: yuxisun@163.com [Key Laboratory for Soft Chemistry and Functional Materials of Education Ministry, Nanjing University of Science and Technology, Nanjing 210094 (China) and Key Laboratory of Life-Organic Analysis, School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu, Shandong 273165 (China); Hao Qingli; Tang Weihua; Wang Yufeng [Key Laboratory for Soft Chemistry and Functional Materials of Education Ministry, Nanjing University of Science and Technology, Nanjing 210094 (China); Yang Xujie, E-mail: yangx@mail.njust.edu.cn [Key Laboratory for Soft Chemistry and Functional Materials of Education Ministry, Nanjing University of Science and Technology, Nanjing 210094 (China); Lu Lude; Wang Xin [Key Laboratory for Soft Chemistry and Functional Materials of Education Ministry, Nanjing University of Science and Technology, Nanjing 210094 (China)

    2011-09-15

    Highlights: {yields} Three imine-bridged aromatic antipyrine derivatives as photo-responsive materials. {yields} The compounds exhibit two-photon absorption and first-hyperpolarization properties {yields} The compounds have long-range electron transfer characteristics. - Abstract: Organic compounds as functional materials have attracted much keen interest in the past three decades owing to their potential applications in science and technology. Currently, great efforts have been made in looking for suitable photo-responsive materials among the multifarious organic compounds. Herein we reported the photophysical properties of 2-furanylmethylene-aminoantipyrine (FMAAP), benzylideneaminoantipyrine (BIAAP) and cinnamilideneamino-antipyrine (CIAAP) studied by a combined experimental and theoretical investigation. Two-photon absorption measurements give the cross-section values of 1.350 x 10{sup -50} cm{sup 4} s/photon for FMAAP, 1.046 x 10{sup -50} cm{sup 4} s/photon for BIAAP and 2.047 x 10{sup -50} cm{sup 4} s/photon for CIAAP. The calculated first-hyperpolarization values are of 2.303 x 10{sup -30}, 1.257 x 10{sup -29}, 2.889 x 10{sup -29} cm{sup 5}/esu for FMAAP, BIAAP and CIAAP, respectively. UV-vis spectroscopy technique further reveals that the studied compounds display long-range electron transfer characteristics by absorbing light of specific wavelengths of 294.5 nm for FMAAP, 293.2 nm for BIAAP and 303.1 nm for CIAAP. All the results indicate that the studied compounds are promising candidates of functionally photo-responsive materials.

  17. High-resolution three-dimensional imaging of a depleted CMOS sensor using an edge Transient Current Technique based on the Two Photon Absorption process (TPA-eTCT)

    CERN Document Server

    García, Marcos Fernández; Echeverría, Richard Jaramillo; Moll, Michael; Santos, Raúl Montero; Moya, David; Pinto, Rogelio Palomo; Vila, Iván

    2016-01-01

    For the first time, the deep n-well (DNW) depletion space of a High Voltage CMOS sensor has been characterized using a Transient Current Technique based on the simultaneous absorption of two photons. This novel approach has allowed to resolve the DNW implant boundaries and therefore to accurately determine the real depleted volume and the effective doping concentration of the substrate. The unprecedented spatial resolution of this new method comes from the fact that measurable free carrier generation in two photon mode only occurs in a micrometric scale voxel around the focus of the beam. Real three-dimensional spatial resolution is achieved by scanning the beam focus within the sample.

  18. Synthesis, crystals of centrosymmetric triphenylamine chromophores bearing prodigious two-photon absorption cross-section and biological imaging

    Science.gov (United States)

    Wang, Shichao; Xu, Shasha; Wang, Yiming; Tian, Xiaohe; Zhang, Yujin; Wang, Chuankui; Wu, Jieying; Yang, Jiaxiang; Tian, Yupeng

    2017-02-01

    Two centrosymmetric D-π-D type triphenylamine chromophores with long π-conjugated bridge and strong electron-donating moiety were designed, synthesized and fully characterized. The crystal analysis revealed that multiple Csbnd H ⋯ π interactions existed in two chromophores, which played a crucial role in generating molecular 1D chains and 2D layers structures. Linear and nonlinear optical properties of the chromophores were systematically investigated with the aid of theoretical calculations. Two chromophores both exhibited intense and wide-dispersed one-photon/two-photon excited fluorescence, bear prodigious 2PA cross section (δ). Especially for Dye2, with ethyoxyl groups, displayed the strong 2PA activity, large cross-sections (δmax > 16,000 GM) and high NLO efficiency (δmax/MW > 16 GM/(g·mol)) in the range of 680-830 nm in DMF. In addition, one- and two-photon fluorescence microscopy images of HepG2 cells incubated with Dye2 were obtained and found that Dye2 could effectively uptake toward living cells and display a uniformly localized in cytosolic space.

  19. Highly efficient flexible piezoelectric nanogenerator and femtosecond two-photon absorption properties of nonlinear lithium niobate nanowires

    Science.gov (United States)

    Gupta, Manoj Kumar; Aneesh, Janardhanakurup; Yadav, Rajesh; Adarsh, K. V.; Kim, Sang-Woo

    2017-05-01

    We present a high performance flexible piezoelectric nanogenerator (NG) device based on the hydrothermally grown lead-free piezoelectric lithium niobate (LiNbO3) nanowires (NWs) for scavenging mechanical energies. The non-linear optical coefficient and optical limiting properties of LiNbO3 were analyzed using femtosecond laser pulse assisted two photon absorption techniques for the first time. Further, a flexible hybrid type NG using a composite structure of the polydimethylsiloxane polymer and LiNbO3 NWs was fabricated, and their piezoelectric output signals were measured. A large output voltage of ˜4.0 V and a recordable large current density of about 1.5 μA cm-2 were obtained under the cyclic compressive force of 1 kgf. A subsequent UV-Vis analysis of the as-prepared sample provides a remarkable increase in the optical band gap (UV absorption cut-off, ˜251 nm) due to the nanoscale size effect. The high piezoelectric output voltage and current are discussed in terms of large band gap, significant nonlinear optical response, and electric dipole alignments under poling effects. Such high performance and unique optical properties of LiNbO3 show its great potential towards various next generation smart electronic applications and self-powered optoelectronic devices.

  20. Theory of direct and indirect effect of two-photon absorption on nonlinear optical losses in high power semiconductor lasers

    Science.gov (United States)

    Avrutin, E. A.; Ryvkin, B. S.

    2017-01-01

    The effect of the transverse laser structure on two-photon absorption (TPA) related effects in high-power diode lasers is analysed theoretically. The direct effect of TPA is found to depend significantly on the transverse waveguide structure, and predicted to be weaker in broad and asymmetric waveguide designs. The indirect effect of TPA, via carrier generation in the waveguide and free-carrier absorption, is analysed for the case of a symmetric laser waveguide and shown to be strongly dependent on the active layer position. With the active layer near the mode peak, the indirect effect is weaker than the direct effect due to the population of TPA-created carriers being efficiently depleted by their diffusion and capture into the active layer, whereas for the active layer position strongly shifted towards the p-cladding, the indirect effect can become the dominant power limitation at very high currents. It is shown that for optimizing a laser design for pulsed high power operation, both TPA related effects and the inhomogeneous carrier accumulation in the waveguide caused by diffusive current need to be taken into account.

  1. Two-Photon Polymerization Metrology: Characterization Methods of Mechanisms and Microstructures

    Directory of Open Access Journals (Sweden)

    Christopher N. LaFratta

    2017-03-01

    Full Text Available The ability to create complex three-dimensional microstructures has reached an unprecedented level of sophistication in the last 15 years. For the most part, this is the result of a steady development of the additive manufacturing technique named two-photon polymerization (TPP. In a short amount of time, TPP has gone from being a microfabrication novelty employed largely by laser specialists to a useful tool in the hands of scientists and engineers working in a wide range of research fields including microfluidics. When used in combination with traditional microfabrication processes, TPP can be employed to add unique three-dimensional components to planar platforms, thus enabling the realization of lab-on-a-chip solutions otherwise impossible to create. To take full advantage of TPP, an in-depth understanding is required of the materials photochemistry and the fabricated microstructures’ mechanical and chemical properties. Thus, we review methods developed so far to investigate the underling mechanism involved during TPP and analytical methods employed to characterize TPP microstructures. Furthermore, we will discuss potential opportunities for using optofluidics and lab-on-a-chip systems for TPP metrology.

  2. Fs-transient absorption and fluorescence upconversion after two- photon excitation of carotenoids in solution and in LHC II

    CERN Document Server

    Wall, P J; Fleming, G R

    2000-01-01

    With time resolved two-photon techniques we determined the lifetime and two-photon spectrum of the forbidden S/sub 1/ state of beta - carotene (9+or-0.2 ps), lutein (15+or-0.5 ps) and the energy transferring carotenoids in LHC II (250+or-50 fs). (7 refs).

  3. Synthesis, characterization and preclinical studies of two-photon-activated targeted PDT therapeutic triads

    Science.gov (United States)

    Spangler, C. W.; Starkey, J. R.; Rebane, A.; Meng, F.; Gong, A.; Drobizhev, M.

    2006-02-01

    Photodynamic therapy (PDT) continues to evolve into a mature clinical treatment of a variety of cancer types as well as age-related macular degeneration of the eye. However, there are still aspects of PDT that need to be improved in order for greater clinical acceptance. While a number of new PDT photo-sensitizers, sometimes referred to as second- or third- generation therapeutic agents, are currently under clinical investigation, the direct treatment through the skin of subcutaneous tumors deeper than 5 mm remains problematic. Currently approved PDT porphyrin photo-sensitizers, as well as several modified porphyrins (e.g. chlorins, bacteriochlorins, etc.) that are under clinical investigation can be activated at 630-730 nm, but none above 800 nm. It would be highly desirable if new PDT paradigms could be developed that would allow photo-activation deep in the tissue transparency window in the Near-infrared (NIR) above 800 nm to reduce scattering and absorption phenomena that reduce deep tissue PDT efficacy. Rasiris and MPA Technologies have developed new porphyrins that have greatly enhanced two-photon absorption ( P A ) cross-sections and can be activated deep in the NIR (ca. 780-850 nm). These porphyrins can be incorporated into a therapeutic triad that also employs an small molecule targeting agent that directs the triad to over-expressed tumor receptor sites, and a NIR onephoton imaging agent that allows tracking the delivery of the triad to the tumor site, as well as clearance of excess triad from healthy tissue prior to the start of PDT treatment. We are currently using these new triads in efficacy studies with a breast cancer cell line that has been transfected with luciferase genes that allow implanted tumor growth and post- PDT treatment efficacy studies in SCID mouse models by following the rise and decay of the bioluminescence signal. We have also designed highly absorbing and scattering collagen breast cancer phantoms in which we have demonstrated

  4. Two-photon absorption spectroscopy of stilbene and phenanthrene: Excited-state analysis and comparison with ethylene and toluene

    Science.gov (United States)

    de Wergifosse, Marc; Elles, Christopher G.; Krylov, Anna I.

    2017-05-01

    Two-photon absorption (2PA) spectra of several prototypical molecules (ethylene, toluene, trans- and cis-stilbene, and phenanthrene) are computed using the equation-of-motion coupled-cluster method with single and double substitutions. The states giving rise to the largest 2PA cross sections are analyzed in terms of their orbital character and symmetry-based selection rules. The brightest 2PA transitions correspond to Rydberg-like states from fully symmetric irreducible representations. Symmetry selection rules dictate that totally symmetric transitions typically have the largest 2PA cross sections for an orientationally averaged sample when there is no resonance enhancement via one-photon accessible intermediate states. Transition dipole arguments suggest that the strongest transitions also involve the most delocalized orbitals, including Rydberg states, for which the relative transition intensities can be rationalized in terms of atomic selection rules. Analysis of the 2PA transitions provides a foundation for predicting relative 2PA cross sections of conjugated molecules based on simple symmetry and molecular orbital arguments.

  5. Two-photon absorption properties of cationic 1,4-bis(styryl)benzene derivative and its inclusion complexes with cyclodextrins.

    Science.gov (United States)

    Nag, Okhil Kumar; Nayak, Rati Ranjan; Lim, Chang Su; Kim, In Hong; Kyhm, Kwangseuk; Cho, Bong Rae; Woo, Han Young

    2010-07-29

    Two-photon absorption properties of 1,4-bis{4'-[N,N-bis(6''-trimethylammoniumhexyl)amino]styryl}benzene tetrabromide (C1) and its inclusion complexes (ICs) with cyclodextrins (CDs) have been studied. Upon complexation with CDs, the absorption spectra of C1 showed a slight red shift, whereas the emission spectra showed a blue shift with concomitant increase in the fluorescence quantum efficiency. A Stern-Volmer study using K(3)Fe(CN)(6) as a quencher revealed significant reduction in the photoinduced charge transfer quenching, in accord with the IC formation. Comparison of the spectroscopic results reveals that C1 forms increasingly more stable ICs in the order C1/beta-CD < C1/gamma-CD < C1/(3gamma:beta)-CD (gamma-CD/beta-CD 3:1, mole ratio). Moreover, the two-photon action cross section of C1 increased from 200 GM for C1 to 400 GM for C1/beta-CD, 460 GM for C1/gamma-CD, and 650 GM for C1/(3gamma:beta)-CD, respectively. Furthermore, the two-photon microscopy images of HeLa cells stained with C1 emitted strong two-photon excited fluorescence in the plasma membrane. These results provide a useful guideline for the development of efficient two-photon materials for bioimaging applications.

  6. Synthesis, singlet-oxygen photogeneration, two-photon absorption, photo-induced DNA cleavage and cytotoxic properties of an amphiphilic β-Schiff-base linked Ru(II) polypyridyl–porphyrin conjugate

    Energy Technology Data Exchange (ETDEWEB)

    Ke, Hanzhong, E-mail: kehanz@163.com [Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan, Hubei 430074 (China); Ma, Wanpeng; Wang, Hongda; Cheng, Guoe [Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan, Hubei 430074 (China); Yuan, Han [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Wong, Wai-Kwok, E-mail: wkwong@hkbu.edu.hk [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Institute of Advanced Materials, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Kwong, Daniel W.J. [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Tam, Hoi-Lam; Cheah, Kok-Wai [Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Institute of Advanced Materials, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Chan, Chi-Fai; Wong, Ka-Leung [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China)

    2014-10-15

    A novel porphyrin–polypyridyl ruthenium(II) conjugate (TPP–Ru), in which the ruthenium(II) polypyridyl moiety is linked to the β-position of the tetraphenylporphyrin via a Schiff base linkage, has been synthesized and characterized by {sup 1}H NMR, HRMS and UV–visible spectroscopy. The relative singlet oxygen quantum yield and two-photon absorption cross-section of this conjugate, together with its photo-induced DNA cleavage and cytotoxic activities were measured. The results show that the amphiphilic ruthenium(II) polypyridyl–porphyrin conjugate is an effective DNA photocleavage agent, with potential application in one- and two-photon absorption anti-cancer photodynamic therapy. - Highlights: • New porphyrin–ruthenium(II) polypyridyl complexes (TTP–Ru) have been synthesized. • The TTP–Ru shows substantial two-photon absorption cross-section (σ{sub 2}=391 GM). • The TTP–Ru exhibits a substantial {sup 1}O{sub 2} quantum yield (0.64±0.13). • The TTP–Ru exhibits a strong DNA cleavage activity upon photo-excitation. • The TTP–Ru is available for in vitro imaging and as a photodynamic therapy agent.

  7. Merged beam laser design for reduction of gain-saturation and two-photon absorption in high power single mode semiconductor lasers.

    Science.gov (United States)

    Lysevych, M; Tan, H H; Karouta, F; Fu, L; Jagadish, C

    2013-04-08

    In this paper we report a method to overcome the limitations of gain-saturation and two-photon absorption faced by developers of high power single mode InP-based lasers and semiconductor optical amplifiers (SOA) including those based on wide-waveguide or slab-coupled optical waveguide laser (SCOWL) technology. The method is based on Y-coupling design of the laser cavity. The reduction in gain-saturation and two-photon absorption in the merged beam laser structures (MBL) are obtained by reducing the intensity of electromagnetic field in the laser cavity. Standard ridge-waveguide lasers and MBLs were fabricated, tested and compared. Despite a slightly higher threshold current, the reduced gain-saturation in MBLs results in higher output power. The MBLs also produced a single spatial mode, as well as a strongly dominating single spectral mode which is the inherent feature of MBL-type cavity.

  8. Measurement of the Two-photon Absorption Coefficient of Gallium Phosphide (GaP) Using a Dispersion-minimized Sub-10 Femtosecond Z-scan Measurement System

    Science.gov (United States)

    2012-09-01

    samples of semiconductors and thin films of organic materials on substrates. The use of dispersive media in the optical path has been eliminated...other semiconductors such as cadmium sulfide (CdS) and zinc selenide (ZnSe). We will also begin measuring the two-photon absorption coefficient for...organic thin - film materials deposited on various substrates. 15 6. References 1. Sheik-Bahae, M.; Said, A. A.; Van Stryland, E. W. High

  9. Saturable absorption and two-photon absorption of 1,2,5-thiadiazolo[3,4-g]quinoxaline based derivatives with near-infrared fluorescence

    Science.gov (United States)

    Du, Yabing; Lin, Xiaodong; Jia, Tingjian; Dong, Jun

    2015-03-01

    Organic molecules with near-infrared (NIR) fluorescence are extremely interesting for the applications in nonlinear optical devices and bioimaging. However, such kind of materials have been relatively rarely studied. In this work, the nonlinear optical properties of 1,2,5-thiadiazolo[3,4-g]quinoxaline based derivatives with NIR fluorescence emission have been investigated for the first time. Under the excitation of femtosecond pulses at 532 nm, the chromophore with dithienyl as donor (TQ2) presents saturable absorption (SA) behavior, while no SA has been observed in the derivative with biphenyl (TQ1) as donor. Moreover, TQ2 exhibits much larger two-photon absorption (TPA) cross-sections with strong NIR fluorescence in the second biological window. The larger nonlinear optical properties of TQ2 is due to the introduction of stronger electron-donating group (dithienyl) and the resultant enhanced intramolecular charge transfer properties. At the end, TPA based optical limiting behaviors of the molecules are demonstrated in THF solutions, thanks to their large solubility and strong TPA.

  10. Two-Photon Microscopy Allows Imaging and Characterization of Cochlear Microvasculature In Vivo

    Directory of Open Access Journals (Sweden)

    Friedrich Ihler

    2015-01-01

    Full Text Available Impairment of cochlear blood flow has been discussed as factor in the pathophysiology of various inner ear disorders. However, the microscopic study of cochlear microcirculation is limited due to small scale and anatomical constraints. Here, two-photon fluorescence microscopy is applied to visualize cochlear microvessels. Guinea pigs were injected with Fluorescein isothiocyanate- or Texas red-dextrane as plasma marker. Intravital microscopy was performed in four animals and explanted cochleae from four animals were studied. The vascular architecture of the cochlea was visualized up to a depth of 90.0±22.7 μm. Imaging yielded a mean contrast-to-noise ratio (CNR of 3.3±1.7. Mean diameter in vivo was 16.5±6.0 μm for arterioles and 8.0±2.4 μm for capillaries. In explanted cochleae, the diameter of radiating arterioles and capillaries was measured with 12.2±1.6 μm and 6.6±1.0 μm, respectively. The difference between capillaries and arterioles was statistically significant in both experimental setups (P<0.001 and P=0.022, two-way ANOVA. Measured vessel diameters in vivo and ex vivo were in agreement with published data. We conclude that two-photon fluorescence microscopy allows the investigation of cochlear microvessels and is potentially a valuable tool for inner ear research.

  11. Pushing the limits of CMOS optical parametric amplifiers with USRN:Si7N3 above the two-photon absorption edge

    Science.gov (United States)

    Ooi, K. J. A.; Ng, D. K. T.; Wang, T.; Chee, A. K. L.; Ng, S. K.; Wang, Q.; Ang, L. K.; Agarwal, A. M.; Kimerling, L. C.; Tan, D. T. H.

    2017-01-01

    CMOS platforms operating at the telecommunications wavelength either reside within the highly dissipative two-photon regime in silicon-based optical devices, or possess small nonlinearities. Bandgap engineering of non-stoichiometric silicon nitride using state-of-the-art fabrication techniques has led to our development of USRN (ultra-silicon-rich nitride) in the form of Si7N3, that possesses a high Kerr nonlinearity (2.8 × 10−13 cm2 W−1), an order of magnitude larger than that in stoichiometric silicon nitride. Here we experimentally demonstrate high-gain optical parametric amplification using USRN, which is compositionally tailored such that the 1,550 nm wavelength resides above the two-photon absorption edge, while still possessing large nonlinearities. Optical parametric gain of 42.5 dB, as well as cascaded four-wave mixing with gain down to the third idler is observed and attributed to the high photon efficiency achieved through operating above the two-photon absorption edge, representing one of the largest optical parametric gains to date on a CMOS platform. PMID:28051064

  12. Two photon absorption energy transfer in the light-harvesting complex of photosystem II (LHC-II) modified with organic boron dye.

    Science.gov (United States)

    Chen, Li; Liu, Cheng; Hu, Rui; Feng, Jiao; Wang, Shuangqing; Li, Shayu; Yang, Chunhong; Yang, Guoqiang

    2014-07-15

    The plant light-harvesting complexes of photosystem II (LHC-II) play important roles in collecting solar energy and transferring the energy to the reaction centers of photosystems I and II. A two photon absorption compound, 4-(bromomethyl)-N-(4-(dimesitylboryl)phenyl)-N-phenylaniline (DMDP-CH2Br), was synthesized and covalently linked to the LHC-II in formation of a LHC-II-dye complex, which still maintained the biological activity of LHC-II system. Under irradiation with femtosecond laser pulses at 754 nm, the LHC-II-dye complex can absorb two photons of the laser light effectively compared with the wild type LHC-II. The absorbed excitation energy is then transferred to chlorophyll a with an obvious fluorescence enhancement. The results may be interesting and give potentials for developing hybrid photosystems.

  13. Dynamic characterization of hydrophobic and hydrophilic solutes in oleic-acid enhanced transdermal delivery using two-photon fluorescence microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, Te-Yu; Yang, Chiu-Sheng; Chen, Yang-Fang [Department of Physics, National Taiwan University, Taipei, Taiwan (China); Tsai, Tsung-Hua [Department of Dermatology, Far Eastern Memorial Hospital, New Taipei City, Taiwan (China); Dong, Chen-Yuan, E-mail: cydong@phys.ntu.edu.tw [Department of Physics, National Taiwan University, Taipei, Taiwan (China); Center for Quantum Science and Engineering, National Taiwan University, Taipei, Taiwan (China); Center for Optoelectronic Biomedicine, National Taiwan University, Taipei, Taiwan (China)

    2014-10-20

    In this letter, we propose an efficient methodology of investigating dynamic properties of sulforhodamine B and rhodamine B hexyl ester molecules transporting across ex-vivo human stratum corneum with and without oleic acid enhancement. Three-dimensional, time-lapse fluorescence images of the stratum corneum can be obtained using two-photon fluorescence microscopy. Furthermore, temporal quantifications of transport enhancements in diffusion parameters can be achieved with the use of Fick's second law. Dynamic characterization of solutes transporting across the stratum corneum is an effective method for understanding transient phenomena in transdermal delivery of probe molecules, leading to improved delivery strategies of molecular species for therapeutic purposes.

  14. Characterization of scintillating CaWO{sub 4} crystals for the CRESST experiment using two-photon excitation

    Energy Technology Data Exchange (ETDEWEB)

    Hampf, Raphael; Dandl, Thomas; Muenster, Andrea; Oberauer, Lothar; Roth, Sabine; Schoenert, Stefan; Ulrich, Andreas [Physik-Department and Excellence Cluster Universe, Technische Universitaet Muenchen, D-85747 Garching (Germany)

    2016-07-01

    In the CRESST experiment for direct dark matter search, phonon and photon signals from cryogenic CaWO{sub 4} crystals are used to search for WIMP-induced nuclear recoil events. We present a novel table-top setup in which the scintillation of CaWO{sub 4} is induced by 0.7 ns laser pulses of 355 nm wavelength. The excitation occurs via two-photon absorption in the bulk material. The scintillation light is observed by time resolved optical spectroscopy. By varying the focusing of the laser-beam the excitation density can be made high enough to study quenching effects due to exciton-exciton annihilation. This allows to perform experiments to test models for the quenching factors of different ionizing projectiles in CaWO{sub 4} which are used to identify these projectiles on an event by event basis.

  15. Relation between bond-length alternation and two-photon absorption of a push pull conjugated molecules: a quantum-chemical study

    Science.gov (United States)

    Bartkowiak, W.; Zaleśny, R.; Leszczynski, J.

    2003-02-01

    The results of the semiempirical study of the structure/property relationships for the two-photon absorption cross-section ( δ) of a series of prototypical π-conjugated push-pull molecules are presented. The calculations of δ for the first charge-transfer (CT) excited state were performed as a function of the bond length alternation (BLA). The molecular hyperpolarizabilities ( β and γ) were calculated using the finite-field (FF) method. The obtained data were analyzed based on the simple two-state models. A strong dependence of δ on the BLA parameter was noticed.

  16. Relation between bond-length alternation and two-photon absorption of a push-pull conjugated molecules: a quantum-chemical study

    Energy Technology Data Exchange (ETDEWEB)

    Bartkowiak, W.; Zalesny, R.; Leszczynski, J

    2003-02-01

    The results of the semiempirical study of the structure/property relationships for the two-photon absorption cross-section ({delta}) of a series of prototypical {pi}-conjugated push-pull molecules are presented. The calculations of {delta} for the first charge-transfer (CT) excited state were performed as a function of the bond length alternation (BLA). The molecular hyperpolarizabilities ({beta} and {gamma}) were calculated using the finite-field (FF) method. The obtained data were analyzed based on the simple two-state models. A strong dependence of {delta} on the BLA parameter was noticed.

  17. Effects of the structure of the branches on the two-photon absorption properties for the multi-branched molecules with nitrogen (N) as coupling center

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In order to investigate the effects of the structure of branches on the TPA properties for multi-branched molecules, the TPA cross section is calculated by using ZINDO/SOS method. The investigated mole- cules have different branches (chomorfores based on stilbene, dithienothiophene and flourene) with nitrogen(N) as coupling center. The results show that the cooperative enhancement in multi-branched molecules depends on the structures of the branches and the structures of branches play an important role in the enhancement of the TPA cross section. The designed molecules with stilbene and dithie- nothiophene as branched possess relatively larger two-photon absorption cross sections.

  18. Effects of the structure of the branches on the two-photon absorption properties for the multi-branched molecules with nitrogen (N) as coupling center

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In order to investigate the effects of the structure of branches on the TPA properties for multi-branched molecules, the TPA cross section is calculated by using ZINDO/SOS method. The investigated molecules have different branches (chomorfores based on stilbene, dithienothiophene and flourene) with nitrogen(N) as coupling center. The results show that the cooperative enhancement in multi-branched molecules depends on the structures of the branches and the structures of branches play an important role in the enhancement of the TPA cross section. The designed molecules with stilbene and dithienothiophene as branched possess relatively larger two-photon absorption cross sections.

  19. Multi-point strain and displacement sensor based on intensity-modulated light and two-photon absorption process in Si-avalanche photodiode

    Science.gov (United States)

    Miyazawa, Hiromasa; Nemoto, Masaya; Yamada, Yoshiki; Tanaka, Yosuke; Kurokawa, Takashi

    2017-04-01

    We propose a system for precise measurement of multi-point displacement and strain using fiber Bragg grating (FBG) sensors along with intensity-modulated light and two-photon absorption process in a Si-avalanche photodiode (Si-APD). This method sweeps both the optical wavelength and the phase difference between the two modulation signals. The FBGs' reflection spectra and their change due to strain are successfully observed at the same time with the precision measurement of the FBG's displacement, where the relative measurement uncertainty is 10-4. This fiber sensing system is especially suitable for structural health monitoring.

  20. The use of one- and two- photon induced fluorescence spectroscopy for the optical characterization of carcinogenic aflatoxins

    Science.gov (United States)

    Smeesters, L.; Meulebroeck, W.; Raeymaekers, S.; Thienpont, H.

    2014-09-01

    Carcinogenic and toxic contaminants in food and feed products are nowadays mostly detected by destructive, time-consuming chemical analyses, like HPLC and LC-MS/MS methods. However, as a consequence of the severe and growing regulations on food products by the European Union, there arose an increased demand for the ultra-fast, high-sensitive and non-destructive detection of contaminants in food and feed products. Therefore, we have investigated fluorescence spectroscopy for the characterization of carcinogenic aflatoxins. With the use of a tunable titanium-sapphire laser in combination with second and third harmonic wavelength generation, both one- and two-photon induced fluorescence excitation wavelengths could be generated using the same setup. We characterized and compared the one- and two-photon induced fluorescence spectra of pure aflatoxin powder, after excitation with 365nm and 730nm respectively. Moreover, we investigated the absolute fluorescence intensity as function of the excitation power density. Afterwards, we applied our characterization setup to the detection of aflatoxins in maize grains. The fluorescence spectra of both healthy and contaminated maize samples were experimentally characterized. In addition to the fluorescence spectrum of the pure aflatoxin, we observed an unwanted influence of the intrinsic fluorescence of the maize. Depending on the excitation wavelength, a varying contrast between the fluorescence spectra of the healthy and contaminated samples was obtained. After a comparison of the measured fluorescence signals, a detection criterion for the optical identification of the contaminated maize samples could be defined. As a result, this illustrates the use of fluorescence spectroscopy as a valuable tool for the non-destructive, real-time and high-sensitive detection of aflatoxins in maize.

  1. Visualizing the Contributions of Virtual States to Two-Photon Absorption Cross Sections by Natural Transition Orbitals of Response Transition Density Matrices.

    Science.gov (United States)

    Nanda, Kaushik D; Krylov, Anna I

    2017-07-20

    Observables such as two-photon absorption cross sections cannot be computed from the wave functions of initial and final states alone because of their nonlinear nature. Rather, they depend on the entire manifold of the excited states, which follows from the familiar sum-over-states expressions of second- and higher-order properties. Consequently, the interpretation of the computed nonlinear optical properties in terms of molecular orbitals is not straightforward and usually relies on approximate few-states models. Here, we show that the two-photon absorption (2PA) transitions can be visualized using response one-particle transition density matrices, which are defined as transition density matrices between the zero-order and first-order perturbed states. We also extend the concept of natural transition orbitals to 2PA transitions. We illustrate the utility of this new tool, which provides a rigorous black box alternative to traditional qualitative few-states analysis, by considering 2PA transitions in ethylene, trans-stilbene, and para-nitroaniline.

  2. Calculations of nonlinear response properties using the intermediate state representation and the algebraic-diagrammatic construction polarization propagator approach: two-photon absorption spectra.

    Science.gov (United States)

    Knippenberg, S; Rehn, D R; Wormit, M; Starcke, J H; Rusakova, I L; Trofimov, A B; Dreuw, A

    2012-02-14

    An earlier proposed approach to molecular response functions based on the intermediate state representation (ISR) of polarization propagator and algebraic-diagrammatic construction (ADC) approximations is for the first time employed for calculations of nonlinear response properties. The two-photon absorption (TPA) spectra are considered. The hierarchy of the first- and second-order ADC∕ISR computational schemes, ADC(1), ADC(2), ADC(2)-x, and ADC(3/2), is tested in applications to H(2)O, HF, and C(2)H(4) (ethylene). The calculated TPA spectra are compared with the results of coupled cluster (CC) models and time-dependent density-functional theory (TDDFT) calculations, using the results of the CC3 model as benchmarks. As a more realistic example, the TPA spectrum of C(8)H(10) (octatetraene) is calculated using the ADC(2)-x and ADC(2) methods. The results are compared with the results of TDDFT method and earlier calculations, as well as to the available experimental data. A prominent feature of octatetraene and other polyene molecules is the existence of low-lying excited states with increased double excitation character. We demonstrate that the two-photon absorption involving such states can be adequately studied using the ADC(2)-x scheme, explicitly accounting for interaction of doubly excited configurations. Observed peaks in the experimental TPA spectrum of octatetraene are assigned based on our calculations.

  3. N-Annulated perylene-substituted and fused porphyrin dimers with intense near-infrared one-photon and two-photon absorption

    KAUST Repository

    Luo, Jie

    2015-01-21

    Fusion of two N-annulated perylene (NP) units with a fused porphyrin dimer along the S0-S1 electronic transition moment axis has resulted in new near-infrared (NIR) dyes 1a/1b with very intense absorption (ε>1.3×105M-1cm-1) beyond 1250nm. Both compounds displayed moderate NIR fluorescence with fluorescence quantum yields of 4.4×10-6 and 6.0×10-6 for 1a and 1b, respectively. The NP-substituted porphyrin dimers 2a/2b have also been obtained by controlled oxidative coupling and cyclodehydrogenation, and they showed superimposed absorptions of the fused porphyrin dimer and the NP chromophore. The excited-state dynamics of all of these compounds have been studied by femtosecond transient absorption measurements, which revealed porphyrin dimer-like behaviour. These new chromophores also exhibited good nonlinear optical susceptibility with large two-photon absorption cross-sections in the NIR region due to extended π-conjugation. Time-dependent density functional theory calculations have been performed to aid our understanding of their electronic structures and absorption spectra.

  4. N-annulated perylene-substituted and fused porphyrin dimers with intense near-infrared one-photon and two-photon absorption.

    Science.gov (United States)

    Luo, Jie; Lee, Sangsu; Son, Minjung; Zheng, Bin; Huang, Kuo-Wei; Qi, Qingbiao; Zeng, Wangdong; Li, Gongqiang; Kim, Dongho; Wu, Jishan

    2015-02-23

    Fusion of two N-annulated perylene (NP) units with a fused porphyrin dimer along the S0-S1 electronic transition moment axis has resulted in new near-infrared (NIR) dyes 1 a/1 b with very intense absorption (ε>1.3×10(5) M(-1) cm(-1)) beyond 1250 nm. Both compounds displayed moderate NIR fluorescence with fluorescence quantum yields of 4.4×10(-6) and 6.0×10(-6) for 1 a and 1 b, respectively. The NP-substituted porphyrin dimers 2 a/2 b have also been obtained by controlled oxidative coupling and cyclodehydrogenation, and they showed superimposed absorptions of the fused porphyrin dimer and the NP chromophore. The excited-state dynamics of all of these compounds have been studied by femtosecond transient absorption measurements, which revealed porphyrin dimer-like behaviour. These new chromophores also exhibited good nonlinear optical susceptibility with large two-photon absorption cross-sections in the NIR region due to extended π-conjugation. Time-dependent density functional theory calculations have been performed to aid our understanding of their electronic structures and absorption spectra.

  5. Synthesis of Dual NIR Two-photon Absorptive [60]fullerenyl Multiadducts for Nonlinear Light-transmittance Reduction Application

    Science.gov (United States)

    2014-11-01

    based reverse saturable absorption (RSA) [1,2] events of both the C60 cage and antenna units in the combined wide UV-visible‒NIR region and effective...is available at http://spiedigitallibrary.org. 14. ABSTRACT Synthesis of several C60-( antenna )x conjugates was performed to demonstrate high...range of wavelengths. It was achieved by covalent attachment of a hybrid combination of two types of light- harvesting fluorescent antenna

  6. Precision distance measurement using a two-photon absorption process in a silicon avalanche photodiode with saw-tooth phase modulation.

    Science.gov (United States)

    Tanaka, Yosuke; Tominaka, Seiji; Kurokawa, Takashi

    2015-10-01

    We present a novel configuration of a precision laser distance measurement based on the two-photon absorption (TPA) photocurrent from a silicon avalanche photodiode (Si-APD). The proposed system uses saw-tooth phase modulation, known as serrodyne modulation, in order to shift the frequency of the reference light from that of the probe light. It suppresses the coherent interference noise between the probe and the reference. The serrodyne modulation also enables lock-in detection of the TPA photocurrent. Furthermore, it contributes to the reduction of the system components. The precision measurement is experimentally demonstrated by measuring a fiber length difference of 2.6 m with a standard deviation of 27 μm under constant temperature. The high-precision displacement measurement is also demonstrated by measuring the temperature-induced change in the optical path length difference of a fiber interferometer.

  7. Generation of ultrafast pulse via combined effects of stimulated Raman scattering and non-degenerate two-photon absorption in silicon nanophotonic chip

    Indian Academy of Sciences (India)

    Jianwei Wu; Fengguang Luo; Mingcui Cao

    2009-04-01

    A project of ultrafast pulse generation has been presented and demonstrated by utilizing the combined nonlinear effects of stimulated Raman scattering (SRS) and non-degenerate two-photon absorption (TPA) based on silicon nanophotonic chip, in which a continuous wave (CW) and an ultrafast dark pulse are co-propagating in the silicon chip so that the CW will be modulated inversely by the dark pulse during the propagation. As a result, an ultrafast bright pulse is achieved using the technique. Simulation results show that an ultrafast pulse with a pulsewidth (full-width at half-maximum (FWHM)) of about 50 fs is generated at the end of a 5-mm long silicon chip, when the initial conditions, including an input maximum of 0.5 W and FWHM of ∼ 176 fs for dark pulse, and CW with power of 5 W, are chosen.

  8. Two-photon-absorption cross section of Nd3+ in yttrium aluminum garnet and yttrium lithium fluoride near 1.06 μm

    Science.gov (United States)

    Chase, L. L.; Payne, Stephen A.

    1986-12-01

    We have measured the spectrally integrated two-photon-absorption (TPA) cross sections for the 4I9/2--> 4G7/2 transitions of Nd3+ and obtained values of 1.2×10-40 and 0.15×10-40 cm4 for Nd3+-doped yttrium aluminum garnet (YAG) and yttrium lithium fluoride (YLF), respectively. These results are in satisfactory agreement with theoretical calculations based on the properties of Nd3+ free-ion wave functions. The difference between YAG and YLF, however, is not accounted for by the free-ion theory and suggests that the intermediate-state energies and wave functions are considerably host dependent. In addition, we conclude, based on our measurements, that rare-earth TPA will not contribute significantly to either losses or the nonlinear refractive index in typical laser media employing rare-earth ions.

  9. Assessment of mode-mixing and Herzberg-Teller effects on two-photon absorption and resonance hyper-Raman spectra from a time-dependent approach.

    Science.gov (United States)

    Ma, HuiLi; Zhao, Yi; Liang, WanZhen

    2014-03-07

    A time-dependent approach is presented to simulate the two-photon absorption (TPA) and resonance hyper-Raman scattering (RHRS) spectra including Duschinsky rotation (mode-mixing) and Herzberg-Teller (HT) vibronic coupling effects. The computational obstacles for the excited-state geometries, vibrational frequencies, and nuclear derivatives of transition dipole moments, which enter the expressions of TPA and RHRS cross sections, are further overcome by the recently developed analytical excited-state energy derivative approaches in the framework of time-dependent density functional theory. The excited-state potential curvatures are evaluated at different levels of approximation to inspect the effects of frequency differences, mode-mixing and HT on TPA and RHRS spectra. Two types of molecules, one with high symmetry (formaldehyde, p-difluorobenzene, and benzotrifluoride) and the other with non-centrosymmetry (cis-hydroxybenzylidene-2,3-dimethylimidazolinone in the deprotonated anion state (HDBI(-))), are used as test systems. The calculated results reveal that it is crucial to adopt the exact excited-state potential curvatures in the calculations of TPA and RHRS spectra even for the high-symmetric molecules, and that the vertical gradient approximation leads to a large deviation. Furthermore, it is found that the HT contribution is evident in the TPA and RHRS spectra of HDBI(-) although its one- and two-photon transitions are strongly allowed, and its effect results in an obvious blueshift of the TPA maximum with respect to the one-photon absorption maximum. With the HT and solvent effects getting involved, the simulated blueshift of 1291 cm(-1) agrees well with the experimental measurement.

  10. Assessment of mode-mixing and Herzberg-Teller effects on two-photon absorption and resonance hyper-Raman spectra from a time-dependent approach

    Energy Technology Data Exchange (ETDEWEB)

    Ma, HuiLi [State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Institute of Fujian Provincial Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Zhao, Yi; Liang, WanZhen, E-mail: liangwz@xmu.edu.cn [State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Institute of Fujian Provincial Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China)

    2014-03-07

    A time-dependent approach is presented to simulate the two-photon absorption (TPA) and resonance hyper-Raman scattering (RHRS) spectra including Duschinsky rotation (mode-mixing) and Herzberg-Teller (HT) vibronic coupling effects. The computational obstacles for the excited-state geometries, vibrational frequencies, and nuclear derivatives of transition dipole moments, which enter the expressions of TPA and RHRS cross sections, are further overcome by the recently developed analytical excited-state energy derivative approaches in the framework of time-dependent density functional theory. The excited-state potential curvatures are evaluated at different levels of approximation to inspect the effects of frequency differences, mode-mixing and HT on TPA and RHRS spectra. Two types of molecules, one with high symmetry (formaldehyde, p-difluorobenzene, and benzotrifluoride) and the other with non-centrosymmetry (cis-hydroxybenzylidene-2,3-dimethylimidazolinone in the deprotonated anion state (HDBI{sup −})), are used as test systems. The calculated results reveal that it is crucial to adopt the exact excited-state potential curvatures in the calculations of TPA and RHRS spectra even for the high-symmetric molecules, and that the vertical gradient approximation leads to a large deviation. Furthermore, it is found that the HT contribution is evident in the TPA and RHRS spectra of HDBI{sup −} although its one- and two-photon transitions are strongly allowed, and its effect results in an obvious blueshift of the TPA maximum with respect to the one-photon absorption maximum. With the HT and solvent effects getting involved, the simulated blueshift of 1291 cm{sup −1} agrees well with the experimental measurement.

  11. Benzothiazoles with tunable electron-withdrawing strength and reverse polarity: a route to triphenylamine-based chromophores with enhanced two-photon absorption.

    Science.gov (United States)

    Hrobárik, Peter; Hrobáriková, Veronika; Sigmundová, Ivica; Zahradník, Pavol; Fakis, Mihalis; Polyzos, Ioannis; Persephonis, Peter

    2011-11-01

    A series of dipolar and octupolar triphenylamine-derived dyes containing a benzothiazole positioned in the matched or mismatched fashion have been designed and synthesized via palladium-catalyzed Sonogashira cross-coupling reactions. Linear and nonlinear optical properties of the designed molecules were tuned by an additional electron-withdrawing group (EWG) and by changing the relative positions of the donor and acceptor substituents on the heterocyclic ring. This allowed us to examine the effect of positional isomerism and extend the structure-property relationships useful in the engineering of novel heteroaromatic-based systems with enhanced two-photon absorption (TPA). The TPA cross-sections (δ(TPA)) in the target compounds dramatically increased with the branching of the triphenylamine core and with the strength of the auxiliary acceptor. In addition, a change from the commonly used polarity in push-pull benzothiazoles to a reverse one has been revealed as a particularly useful strategy (regioisomeric control) for enhancing TPA cross-sections and shifting the absorption and emission maxima to longer wavelengths. The maximum TPA cross-sections of the star-shaped three-branched triphenylamines are ∼500-2300 GM in the near-infrared region (740-810 nm); thereby the molecular weight normalized δ(TPA)/MW values of the best performing dyes within the series (2.0-2.4 GM·g(-1)·mol) are comparable to those of the most efficient TPA chromophores reported to date. The large TPA cross-sections combined with high emission quantum yields and large Stokes shifts make these compounds excellent candidates for various TPA applications, including two-photon fluorescence microscopy.

  12. Evaluation of hybrid polymers for high-precision manufacturing of 3D optical interconnects by two-photon absorption lithography

    Science.gov (United States)

    Schleunitz, A.; Klein, J. J.; Krupp, A.; Stender, B.; Houbertz, R.; Gruetzner, G.

    2017-02-01

    The fabrication of optical interconnects has been widely investigated for the generation of optical circuit boards. Twophoton absorption (TPA) lithography (or high-precision 3D printing) as an innovative production method for direct manufacture of individual 3D photonic structures gains more and more attention when optical polymers are employed. In this regard, we have evaluated novel ORMOCER-based hybrid polymers tailored for the manufacture of optical waveguides by means of high-precision 3D printing. In order to facilitate future industrial implementation, the processability was evaluated and the optical performance of embedded waveguides was assessed. The results illustrate that hybrid polymers are not only viable consumables for industrial manufacture of polymeric micro-optics using generic processes such as UV molding. They also are potential candidates to fabricate optical waveguide systems down to the chip level where TPA-based emerging manufacturing techniques are engaged. Hence, it is shown that hybrid polymers continue to meet the increasing expectations of dynamically growing markets of micro-optics and optical interconnects due to the flexibility of the employed polymer material concept.

  13. Femtosecond, two-photon-absorption, laser-induced-fluorescence (fs-TALIF) imaging of atomic hydrogen and oxygen in non-equilibrium plasmas

    Science.gov (United States)

    Schmidt, Jacob B.; Roy, Sukesh; Kulatilaka, Waruna D.; Shkurenkov, Ivan; Adamovich, Igor V.; Lempert, Walter R.; Gord, James R.

    2017-01-01

    Femtosecond, two-photon-absorption laser-induced fluorescence (fs-TALIF) is employed to measure space- and time-resolved distributions of atomic hydrogen and oxygen in moderate-pressure, non-equilibrium, nanosecond-duration pulsed-discharge plasmas. Temporally and spatially resolved hydrogen and oxygen TALIF images are obtained over a range of low-temperature plasmas in mixtures of helium and argon at 100 Torr total pressure. The high-peak-intensity, low-average-energy fs pulses combined with the increased spectral bandwidth compared to traditional ns-duration laser pulses provide a large number of photon pairs that are responsible for the two-photon excitation, which results in an enhanced TALIF signal. Krypton and xenon TALIF are used for quantitative calibration of the hydrogen and oxygen concentrations, respectively, with similar excitation schemes being employed. This enables 2D collection of atomic-hydrogen and -oxygen TALIF signals with absolute number densities ranging from 2  ×  1012 cm-3 to 6  ×  1015 cm-3 and 1  ×  1013 cm-3 to 3  ×  1016 cm-3, respectively. These 2D images are the first application of TALIF imaging in moderate-pressure plasma discharges. 1D self-consistent modeling predictions show agreement with experimental results within the estimated experimental error of 25%. The present results can be used to further the development of higher fidelity kinetic models while quantifying plasma-source characteristics.

  14. Two-photon physics

    Energy Technology Data Exchange (ETDEWEB)

    Bardeen, W.A.

    1981-10-01

    A new experimental frontier has recently been opened to the study of two photon processes. The first results of many aspects of these reactions are being presented at this conference. In contrast, the theoretical development of research ito two photon processes has a much longer history. This talk reviews the many different theoretical ideas which provide a detailed framework for our understanding of two photon processes.

  15. Theoretical analysis of the two-photon absorption spectrum of Tb sup 3 sup + in Cs sub 2 NaTbCl sub 6

    CERN Document Server

    Wang Dian Yuan; Xia Shang Da; Tanner, P A

    2003-01-01

    Eighteen selected two-photon absorption (TPA) transition line strengths with polarization angles theta = 0 deg. and 45 deg., spanning several orders of magnitude, have been calculated for the Tb sup 3 sup + ion in the cubic host Cs sub 2 NaTbCl sub 6. The results are in reasonable agreement with experimental results in the literature. The calculation utilized the crystal field (CF) wavefunctions for the initial and final states of the 4f sup 8 configuration, and utilized free ion or CF wavefunctions (with the corresponding energies) for 4f sup 7 core states of the whole intermediate 4f sup 7 5d configuration comprising 34 320 states. The intensities of certain transitions were found to be very sensitive to the inclusion of the CF interaction within the 4f sup 7 core. In contrast to previous fourth- or third-order calculations of the TPA transition line strength of the strong transition ( sup 7 F sub 6)A sub 1 sub g -> ( sup 5 D sub 4)A sub 1 sub g using pure Russell-Saunders (RS) wavefunctions for the | sup 7...

  16. Absolute atomic oxygen density measurements for nanosecond-pulsed atmospheric-pressure plasma jets using two-photon absorption laser-induced fluorescence spectroscopy

    Science.gov (United States)

    Jiang, C.; Carter, C.

    2014-12-01

    Nanosecond-pulsed plasma jets that are generated under ambient air conditions and free from confinement of electrodes have become of great interest in recent years due to their promising applications in medicine and dentistry. Reactive oxygen species that are generated by nanosecond-pulsed, room-temperature non-equilibrium He-O2 plasma jets among others are believed to play an important role during the bactericidal or sterilization processes. We report here absolute measurements of atomic oxygen density in a 1 mm-diameter He/(1%)O2 plasma jet at atmospheric pressure using two-photon absorption laser-induced fluorescence spectroscopy. Oxygen number density on the order of 1013 cm-3 was obtained in a 150 ns, 6 kV single-pulsed plasma jet for an axial distance up to 5 mm above the device nozzle. Temporally resolved O density measurements showed that there are two maxima, separated in time by 60-70 µs, and a total pulse duration of 260-300 µs. Electrostatic modeling indicated that there are high-electric-field regions near the nozzle exit that may be responsible for the observed temporal behavior of the O production. Both the field-distribution-based estimation of the time interval for the O number density profile and a pulse-energy-dependence study confirmed that electric-field-dependent, direct and indirect electron-induced processes play important roles for O production.

  17. Production mechanism of atomic nitrogen in atmospheric pressure pulsed corona discharge measured using two-photon absorption laser-induced fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Teramoto, Yoshiyuki; Ono, Ryo [Department of Advanced Energy, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 227-8568 (Japan); Oda, Tetsuji [Department of Electrical Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2012-06-01

    To study the production mechanism of atomic nitrogen, the temporal profile and spatial distribution of atomic nitrogen are measured in atmospheric pressure pulsed positive corona discharge using two-photon absorption laser-induced fluorescence. The absolute atomic nitrogen density in the streamer filaments is estimated from decay rate of atomic nitrogen in N{sub 2} discharge. The results indicate that the absolute atomic nitrogen density is approximately constant against discharge energy. When the discharge voltage is 21.5 kV, production yield of atomic nitrogen produced by an N{sub 2} discharge pulse is estimated to be 2.9 - 9.8 Multiplication-Sign 10{sup 13} atoms and the energy efficiency of atomic nitrogen production is estimated to be about 1.8 - 6.1 Multiplication-Sign 10{sup 16} atoms/J. The energy efficiency of atomic nitrogen production in N{sub 2} discharge is constant against the discharge energy, while that in N{sub 2}/O{sub 2} discharge increases with discharge energy. In the N{sub 2}/O{sub 2} discharge, two-step process of N{sub 2} dissociation plays significant role for atomic nitrogen production.

  18. Spectral characterization and unmixing of intrinsic contrast in intact normal and diseased gastric tissues using hyperspectral two-photon microscopy.

    Directory of Open Access Journals (Sweden)

    Lauren E Grosberg

    Full Text Available BACKGROUND: Living tissues contain a range of intrinsic fluorophores and sources of second harmonic generation which provide contrast that can be exploited for fresh tissue imaging. Microscopic imaging of fresh tissue samples can circumvent the cost and time associated with conventional histology. Further, intrinsic contrast can provide rich information about a tissue's composition, structure and function, and opens the potential for in-vivo imaging without the need for contrast agents. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we used hyperspectral two-photon microscopy to explore the characteristics of both normal and diseased gastrointestinal (GI tissues, relying only on their endogenous fluorescence and second harmonic generation to provide contrast. We obtained hyperspectral data at subcellular resolution by acquiring images over a range of two-photon excitation wavelengths, and found excitation spectral signatures of specific tissue types based on our ability to clearly visualize morphology. We present the two-photon excitation spectral properties of four major tissue types that are present throughout the GI tract: epithelium, lamina propria, collagen, and lymphatic tissue. Using these four excitation signatures as basis spectra, linear unmixing strategies were applied to hyperspectral data sets of both normal and neoplastic tissue acquired in the colon and small intestine. Our results show that hyperspectral unmixing with excitation spectra allows segmentation, showing promise for blind identification of tissue types within a field of view, analogous to specific staining in conventional histology. The intrinsic spectral signatures of these tissue types provide information relating to their biochemical composition. CONCLUSIONS/SIGNIFICANCE: These results suggest hyperspectral two-photon microscopy could provide an alternative to conventional histology either for in-situ imaging, or intraoperative 'instant histology' of fresh tissue

  19. One- and two-photon absorption of fluorescein dianion in water: a study using S-QM/MM methodology and ZINDO method.

    Science.gov (United States)

    Silva, D L; Barreto, R C; Lacerda, E G; Coutinho, K; Canuto, S

    2014-02-05

    One- and two-photon absorption (1PA and 2PA) of fluorescein dianion (FSD) in water were studied using a combined and sequential Quantum Mechanics/Molecular Dynamics methodology. Different sets of 250 statistically relevant (uncorrelated) configurations composed by the solute and several solvent molecules were sampled from the classical simulation. On these configurations, the electronic properties were calculated a posteriori using the Zerner's intermediate neglect of differential overlap (ZINDO) method. The linear and nonlinear absorption of FSD in water were calculated using discrete and explicit solvent models. In the largest case, the relevant configurations are composed by FSD and 47 explicit water molecules embedded in the electrostatic field of all remaining water molecules. Both INDO/CIS and INDO/CISD calculations were performed to study the absorption processes of FSD and the Sum-Over-States (SOS) model was used to describe the 2PA process. A semi-classical method for spectrum simulations was employed to simulate the 1PA and 2PA cross-section spectra of FSD in water. For comparison purposes, in the case of the 2PA process two approaches, the "full expression" and "resonant expression" methods, were employed to simulate the nonlinear spectrum. The last method assumes resonant conditions and on the computation point of view it represents an interesting option to study the 2PA process. The INDO/CI calculations give a satisfactory description of the 1PA spectrum of FSD and properly describe the unusual blue-shift of its first π→π(*) transition in water. In the case of 2PA, the introduction of doubly excited configuration interactions (INDO/CISD) has proven to be essential for an appropriate description of the process at the higher energy spectral region. It was observed that the solvent effects do not drastically change the cross-sections of both processes. The simulated 2PA cross-section spectrum provided by the "full expression" method presents a better

  20. Two-photon cryomicroscope

    Science.gov (United States)

    Breunig, H. G.; Köhler, C.; König, K.

    2012-03-01

    We report on a new two-photon cryomicroscope which consist of a compact laser-scanning microscope combined with a motorized heating and freezing stage. Samples can be cooled down to -196 °C (77 K) and heated up to 600 °C (873 K) with adjustable heating/freezing rates between 0.01 K / min and 150 K / min. Two-photon imaging is realized by near infrared femtosecond-laser pulse excitation. The abilities of the two-photon cryomicroscope are illustrated in several measurements: imaging of fluorescent microspheres inside a piece of ice illustrates the feasibility of deep-microscopic imaging inside frozen sample. The temperature-dependent structural integrity of collagen is monitored by detection of second harmonic generation signals from porcine cornea. The measurements reveal also the dependence of the collagendenaturation temperature on hydration state of the cornea collagen. Furthermore, the potential of the two-photon cryomicroscope for optimization of freezing and thawing procedures as well as to evaluate the viability of frozen cells and tissue is discussed.

  1. Platinum Acetylide Two-Photon Chromophores (Preprint)

    Science.gov (United States)

    2007-04-01

    the higher energy range that lead to its photodegradation . Secondly, because there is a quadratic dependence of two-photon absorption (2PA) on the...to either an electron donating amino- fluorenyl or electron withdrawing benzothiazolyl-fluorene that are themselves known as two-photon absorbing dyes ...groups in place of phenyl groups have shown a doubling of the intrinsic cr2value at 740 nm.40,41In this paper we describe novel platinum dyes that

  2. Characterizing the intracellular distribution of metabolites in intact Chlamydia-infected cells by Raman and two-photon microscopy.

    Science.gov (United States)

    Szaszák, Márta; Chang, Jiun Chiun; Leng, Weinan; Rupp, Jan; Ojcius, David M; Kelley, Anne Myers

    2013-06-01

    Chlamydia species are obligate intracellular pathogens that proliferate only within infected cells. Currently, there are no known techniques or systems that can probe the spatial distribution of metabolites of interest within intact Chlamydia-infected cells. Here we investigate the ability of Raman microscopy to probe the chemical composition of different compartments (nucleus, inclusion, and cytoplasm) of Chlamydia trachomatis-infected epithelial cells. The overall intensity of the Raman spectrum is greatest in the inclusions and lowest in the cytoplasm in fixed cells. Difference spectra generated by normalizing to the intensity of the strong 1004 cm(-1) phenylalanine line show distinct differences among the three compartments. Most notably, the concentrations of adenine are greater in both the inclusions and the nucleus than in the cytoplasm, as seen by Raman microscopy. The source of the adenine was explored through a complementary approach, using two-photon microscopy imaging. Autofluorescence measurements of living, infected cells show that the adenine-containing molecules, NAD(P)H and FAD, are present mainly in the cytoplasm, suggesting that these molecules are not the source of the additional adenine signal in the nucleus and inclusions. Experiments of infected cells stained with a DNA-binding dye, Hoechst 33258, reveal that most of the DNA is present in the nucleus and the inclusions, suggesting that DNA/RNA is the main source of the additional Raman adenine signal in the nucleus and inclusions. Thus, Raman and two-photon microscopy are among the few non-invasive methods available to investigate cells infected with Chlamydia and, together, should also be useful for studying infection by other intracellular pathogens that survive within intracellular vacuoles.

  3. Sideband-Induced Two-Photon Transparency

    Institute of Scientific and Technical Information of China (English)

    CHENG Guang-Ling; HU Xiang-Ming

    2006-01-01

    @@ We show that it is possible to use a single sideband to induce two-photon transparency in a three-level cascade medium. The medium simultaneously absorbs two photons as a one-step process when the middle level is far off one-photon resonance. A resonant sideband coupling on the upper transition and the two-photon one-step process drive the medium into a trapped state, and the dominant component is the ground state. Thus almost all population is trapped in the ground state and the two-photon absorption is dramatically suppressed. We present a numerical calculation for arbitrary values of the atomic and field parameters and also provide an analytic description for the required conditions.

  4. Medical prototyping using two photon polymerization

    Directory of Open Access Journals (Sweden)

    Roger J Narayan

    2010-12-01

    Full Text Available Two photon polymerization involves nearly simultaneous absorption of ultrashort laser pulses for selective curing of photosensitive material. This process has recently been used to create small-scale medical devices out of several classes of photosensitive materials, such as acrylate-based polymers, organically-modified ceramic materials, zirconium sol-gels, and titanium-containing hybrid materials. In this review, the use of two photon polymerization for fabrication of several types of small-scale medical devices, including microneedles, artificial tissues, microfluidic devices, pumps, sensors, and valves, from computer models is described. Necessary steps in the development of two photon polymerization as a commercially viable medical device manufacturing method are also considered.

  5. Two-photon absorption prop erties of novel charge transfer molecules with divinyl sulfide/sulfone center%以二乙烯硫/砜基为中心的新型电荷转移分子双光子吸收特性∗

    Institute of Scientific and Technical Information of China (English)

    武香莲; 赵珂; 贾海洪; 王富青

    2015-01-01

    Organic materials with strong two-photon absorption response have attracted a great deal of interest in recent years for their many potential applications such as two-photon fluorescence microscopy, optical limiting, photodynamic therapy, and so on. Theoretical study on the relationships between molecular structure and two-photon absorption property has great importance in guiding the experimental design and synthesis of functional materials. Nowadays, quantum chemical calculations become very useful and popular tools in investigating the structure-property relations. At the same compu-tational level, the two-photon absorption properties of different compounds can be compared accurately, and thus provide reasonable structure-property relations. Recently, a series of novel divinyl sulfides/sulfonesbased molecules have been synthesized and it is found that their photophysical properties behave like quadrupolar charge-transfer chromophores. In order to explore their potential two-photon absorption applications, in this paper, the two-photon absorption properties of these new molecules are calculated by using quantum chemical methods. Their molecular geometries are optimized at the hybrid B3LYP level with 6-31+g(d, p) basis set in the Gaussian 09 program. The two-photon absorption cross sec-tions are calculated by response theory using the B3LYP functional with 6-31g(d) and 6-31+g(d) basis sets respectively in the Dalton program. In response theory, the single residue of the quadratic response function is used to identify the two-photon transition matrix element. Using the same methods, the two-photon absorption properties of distyrylbenzene compounds are computed for comparison. The basis set effects on excitation energies and two-photon absorption cross sections have been checked. It is found that the use of large basis sets could probably provide better numerical results, but the overall property trends would not change. Calculations show that the molecule with a

  6. One- and Two-photon Excited Fluorescence of Zinc(Ⅱ), Cadmium(Ⅱ) Complexes Containing Phenothiazine Ligand

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A new ligand, 10-ethylphenothiazinyl - 3 - yl - methylene thiosemicarbazon (HL) and its complexes ML2 (M=Zn2+, Cd2+), which exhibit intensive two-photon excited (TPE) fluorescence at 800 nm laser pulses in femtosecond regime, were synthesized and characterized.The measured power dependence of the fluorescence signals provided direct evidence for TPE.All of them exhibited a large two-photon absorptive cross section and, more importantly from the application point of view, high photochemical/photothermal stability.

  7. Two photon physics. Personal recollection

    CERN Document Server

    Ginzburg, Ilya F

    2015-01-01

    The term two--photon processes is used for the reactions in which some system of particles is produced in collision of two photons, either real or virtual. In the study of these processes our main goal was to suggest approach, allowing to extract from the data information on proper two--photon process separating it from mechanism which responsible for the production of photons. Here I present my view for history of two--photon physics. I don't try to give complete review, concentrating mainly on works of our team (which cover essential part of the topic) and some colleagues. My citation is strongly incomplete. I cite here only papers which were essential in our understanding of the problems. The choice of presented details is the result of my discussions with Gleb Kotkin and Valery Serbo. 1. Prehistory. 2. Two photon processes at e^+e^- colliders. 3. Photon colliders. 4. Notes on physical program.

  8. Two-photon ionization of colliding atoms

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, M.H.

    1977-09-01

    Semiclassical expressions of two-photon ionization of two colliding atoms are derived for a wide range of electromagnetic field intensity and detunings from the isolated atom line. The dependence of the ionization yield on the details of the interaction potential of the system is derived. This process promises an extremely sensitive method for studying line broadening on the far wing, especially when absorption or fluorescence becomes very weak.

  9. Excited-state dynamics and two-photon absorption cross sections of fluorescent diphenyl-tin(IV) derivatives with schiff bases: a comparative study of the effect of chelation from the ultrafast to the steady-state time scale.

    Science.gov (United States)

    Zugazagoitia, Jimena S; Maya, Mauricio; Damián-Zea, Carlos; Navarro, Pedro; Beltrán, Hiram I; Peon, Jorge

    2010-01-21

    Schiff bases bearing an intramolecular hydrogen bond are known to undergo excited-state intramolecular proton transfer and E-Z isomerization, which are related to their thermochromism and solvatochromism properties. In this study, we explored these ultrafast photoinduced processes for two doubly hydroxylated Schiff bases, salicylidene-2-aminophenol and 2-hydroxynaphthylmethylidene-2-aminophenol. From comparisons with our previously reported results for the parent monohidroxylated Schiff base salicylideneaniline, we were able to establish the lack of an effect of a second intramolecular hydrogen bond in the excited-state intramolecular proton-transfer process. Moreover, we synthesized and studied the photophysics of 14 diphenyl-tin(IV) derivatives with Schiff bases with the same framework as the former two. In these organometallic compounds, we observed an increase of more than 50 times in the excited-state decay times in comparison with those of the free ligands. This finding is attributed to the coordination with the metallic center, which restricts the fluctuations of the geometry of the organic Schiff base skeleton. The emission bands of these complexes can be easily tuned through substitutions at the Schiff base ligand and can be made to be centered well above 600 nm. The much enhanced emissive behavior of all diphenyl-tin(IV) derivatives allowed the study of several properties of their electronically excited states, including the effects of different substituents on their femtosecond and picosecond dynamics. Considering potential applications, we also performed transient absorption experiments to assess the wavelength interval for stimulated emission of this type of compound. Finally, we determined their two-photon absorption cross sections in the 760-820-nm range by measuring their two-photon induced fluorescence excitation spectra. Mainly, our results illustrate that the diphenyl-tin(IV) moiety, thanks to its size and its coordination mode with a single

  10. The development of efficient two-photon singlet oxygen sensitizers

    DEFF Research Database (Denmark)

    Nielsen, Christian Benedikt

    The development of efficient two-photon singlet oxygen sensitizers is addressed focusing on organic synthesis. Photophysical measurements were carried out on new lipophilic molecules, where two-photon absorption cross sections and singlet oxygen quantumyields were measured. Design principles...... for making efficient two-photon singlet oxygen sensitizers were then constructed from these results. Charge-transfer in the excited state of the prepared molecules was shown to play a pivotal role in the generationof singlet oxygen. This was established through studies of substituent effects on both...... the singlet oxygen yield and the two-photon absorption cross section, where it was revealed that a careful balancing of the amount of charge transfer present in theexcited state of the sensitizer is necessary to obtain both a high singlet oxygen quantum yield and a high two-photon cross section. An increasing...

  11. Two-photon microscopy for chemical neuroscience.

    Science.gov (United States)

    Ellis-Davies, Graham C R

    2011-04-20

    Microscopes using non-linear excitation of chromophores with pulsed near-IR light can generate highly localized foci of molecules in the electronic singlet state that are concentrated in volumes of less than one femtoliter. The three-dimensional confinement of excitation arises from the simultaneous absorption of two IR photons of approximately half the energy required for linear excitation. Two-photon microscopy is especially useful for two types of interrogation of neural processes. First, uncaging of signaling molecules such as glutamate, as stimulation is so refined it can be used to mimic normal unitary synaptic levels. In addition, uncaging allows complete control of the timing and position of stimulation, so the two-photon light beam provides the chemical neuroscientist with an "optical conductor's baton" which can command synaptic activity at will. A second powerful feature of two-photon microscopy is that when used for fluorescence imaging it enables the visualization of cellular structure and function in living animals at depths far beyond that possible with normal confocal microscopes. In this review I provide a survey of the many important applications of two-photon microscopy in these two fields of neuroscience, and suggest some areas for future technical development.

  12. Arduino Due based tool to facilitate in vivo two-photon excitation microscopy.

    Science.gov (United States)

    Artoni, Pietro; Landi, Silvia; Sato, Sebastian Sulis; Luin, Stefano; Ratto, Gian Michele

    2016-04-01

    Two-photon excitation spectroscopy is a powerful technique for the characterization of the optical properties of genetically encoded and synthetic fluorescent molecules. Excitation spectroscopy requires tuning the wavelength of the Ti:sapphire laser while carefully monitoring the delivered power. To assist laser tuning and the control of delivered power, we developed an Arduino Due based tool for the automatic acquisition of high quality spectra. This tool is portable, fast, affordable and precise. It allowed studying the impact of scattering and of blood absorption on two-photon excitation light. In this way, we determined the wavelength-dependent deformation of excitation spectra occurring in deep tissues in vivo.

  13. Higgs Decay to Two Photons

    OpenAIRE

    Marciano, William J.; Zhang, Cen; Willenbrock, Scott

    2011-01-01

    The amplitude for Higgs decay to two photons is calculated in renormalizable and unitary gauges using dimensional regularization at intermediate steps. The result is finite, gauge independent, and in agreement with previously published results. The large Higgs mass limit is examined using the Goldstone-boson equivalence theorem as a check on the use of dimensional regularization and to explain the absence of decoupling.

  14. Two-photon absorption cross sections within equation-of-motion coupled-cluster formalism using resolution-of-the-identity and Cholesky decomposition representations: Theory, implementation, and benchmarks.

    Science.gov (United States)

    Nanda, Kaushik D; Krylov, Anna I

    2015-02-14

    The equation-of-motion coupled-cluster (EOM-CC) methods provide a robust description of electronically excited states and their properties. Here, we present a formalism for two-photon absorption (2PA) cross sections for the equation-of-motion for excitation energies CC with single and double substitutions (EOM-CC for electronically excited states with single and double substitutions) wave functions. Rather than the response theory formulation, we employ the expectation-value approach which is commonly used within EOM-CC, configuration interaction, and algebraic diagrammatic construction frameworks. In addition to canonical implementation, we also exploit resolution-of-the-identity (RI) and Cholesky decomposition (CD) for the electron-repulsion integrals to reduce memory requirements and to increase parallel efficiency. The new methods are benchmarked against the CCSD and CC3 response theories for several small molecules. We found that the expectation-value 2PA cross sections are within 5% from the quadratic response CCSD values. The RI and CD approximations lead to small errors relative to the canonical implementation (less than 4%) while affording computational savings. RI/CD successfully address the well-known issue of large basis set requirements for 2PA cross sections calculations. The capabilities of the new code are illustrated by calculations of the 2PA cross sections for model chromophores of the photoactive yellow and green fluorescent proteins.

  15. Two-photon absorption cross sections within equation-of-motion coupled-cluster formalism using resolution-of-the-identity and Cholesky decomposition representations: Theory, implementation, and benchmarks

    Energy Technology Data Exchange (ETDEWEB)

    Nanda, Kaushik D.; Krylov, Anna I. [Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482 (United States)

    2015-02-14

    The equation-of-motion coupled-cluster (EOM-CC) methods provide a robust description of electronically excited states and their properties. Here, we present a formalism for two-photon absorption (2PA) cross sections for the equation-of-motion for excitation energies CC with single and double substitutions (EOM-CC for electronically excited states with single and double substitutions) wave functions. Rather than the response theory formulation, we employ the expectation-value approach which is commonly used within EOM-CC, configuration interaction, and algebraic diagrammatic construction frameworks. In addition to canonical implementation, we also exploit resolution-of-the-identity (RI) and Cholesky decomposition (CD) for the electron-repulsion integrals to reduce memory requirements and to increase parallel efficiency. The new methods are benchmarked against the CCSD and CC3 response theories for several small molecules. We found that the expectation-value 2PA cross sections are within 5% from the quadratic response CCSD values. The RI and CD approximations lead to small errors relative to the canonical implementation (less than 4%) while affording computational savings. RI/CD successfully address the well-known issue of large basis set requirements for 2PA cross sections calculations. The capabilities of the new code are illustrated by calculations of the 2PA cross sections for model chromophores of the photoactive yellow and green fluorescent proteins.

  16. Two-photon absorption cross sections within equation-of-motion coupled-cluster formalism using resolution-of-the-identity and Cholesky decomposition representations: Theory, implementation, and benchmarks

    Science.gov (United States)

    Nanda, Kaushik D.; Krylov, Anna I.

    2015-02-01

    The equation-of-motion coupled-cluster (EOM-CC) methods provide a robust description of electronically excited states and their properties. Here, we present a formalism for two-photon absorption (2PA) cross sections for the equation-of-motion for excitation energies CC with single and double substitutions (EOM-CC for electronically excited states with single and double substitutions) wave functions. Rather than the response theory formulation, we employ the expectation-value approach which is commonly used within EOM-CC, configuration interaction, and algebraic diagrammatic construction frameworks. In addition to canonical implementation, we also exploit resolution-of-the-identity (RI) and Cholesky decomposition (CD) for the electron-repulsion integrals to reduce memory requirements and to increase parallel efficiency. The new methods are benchmarked against the CCSD and CC3 response theories for several small molecules. We found that the expectation-value 2PA cross sections are within 5% from the quadratic response CCSD values. The RI and CD approximations lead to small errors relative to the canonical implementation (less than 4%) while affording computational savings. RI/CD successfully address the well-known issue of large basis set requirements for 2PA cross sections calculations. The capabilities of the new code are illustrated by calculations of the 2PA cross sections for model chromophores of the photoactive yellow and green fluorescent proteins.

  17. Effect of the diradical character on static polarizabilities and two-photon absorption cross sections: A closer look with spin-flip equation-of-motion coupled-cluster singles and doubles method

    Science.gov (United States)

    Nanda, Kaushik D.; Krylov, Anna I.

    2017-06-01

    We present static polarizabilities and two-photon absorption (2PA) cross sections for the low-lying electronic states of prototypical diradicals such as benzynes and analogues of m-xylylene and p-quinodimethane computed with the spin-flip equation-of-motion coupled-cluster singles and doubles (EOM-SF-CCSD) method. The static polarizabilities were calculated as analytic second derivatives of the EOM energies, and the 2PA cross sections were calculated using the expectation-value approach. We explain the trends in the nonlinear responses of the SF target states by constructing few-states models based on truncated sum-over-states expressions for these nonlinear properties. By using a Huckel-type treatment of the frontier molecular orbitals that host the unpaired electrons, we rationalize the trends in the dipole interactions between the SF target states relevant in the few-states models. We demonstrate the correlation between the nonlinear responses of these electronic states and the diradical character.

  18. Synthesis and characterization of cell-permeable caged phosphates that can be photolyzed by visible light or 800 nm two-photon photolysis.

    Science.gov (United States)

    Herbivo, Cyril; Omran, Ziad; Revol, Julia; Javot, Hélène; Specht, Alexandre

    2013-11-25

    We report the synthesis and photolytic properties of caged inorganic phosphates (Pi compounds) based on the 2-(4'-{bis[2-(2-methoxyethoxy)ethyl]amino}-4-nitro-[1,1'-biphenyl]-3-yl)propan-1-ol (EANBP) and 7-(diethylamino)coumarin-4-yl]methyl (DEACM) protecting groups. The EANBP-Pi showed unprecedented photolysis efficiency at 405 nm, with 95 % release of free phosphate and a quantum yield of 0.28. Thanks to the high two-photon sensitivity of the EANBP chromophore, Pi release through two-photon photolysis is also possible, with an action cross section of 20.5 GM at 800 nm. Two bioactivatable acetoxymethyl protection groups were added to the "caged-Pi" compounds. The resulting triesters of phosphoric acid were able to diffuse through the cellular membranes of plant cells. Once inside a cell, the cleavage of these biocleavable motifs by intracellular esterases allows intracellular accumulation of EANBP-Pi. Bis(AM)-EANBP-Pi therefore represents a very attractive tool for study of the Pi signal transduction cascade in living cells.

  19. Two-photon pumped lead halide perovskite nanowire lasers

    CERN Document Server

    Gu, Zhiyuan; Sun, Wenzhao; Li, Jinakai; Liu, Shuai; Song, Qinghai; Xiao, Shumin

    2015-01-01

    Solution-processed lead halide perovskites have shown very bright future in both solar cells and microlasers. Very recently, the nonlinearity of perovskites started to attract considerable research attention. Second harmonic generation and two-photon absorption have been successfully demonstrated. However, the nonlinearity based perovskite devices such as micro- & nano- lasers are still absent. Here we demonstrate the two-photon pumped nanolasers from perovskite nanowires. The CH3NH3PbBr3 perovskite nanowires were synthesized with one-step solution self-assembly method and dispersed on glass substrate. Under the optical excitation at 800 nm, two-photon pumped lasing actions with periodic peaks have been successfully observed at around 546 nm. The obtained quality (Q) factors of two-photon pumped nanolasers are around 960, and the corresponding thresholds are about 674?J=cm2. Both the Q factors and thresholds are comparable to conventional whispering gallery modes in two-dimensional polygon microplates. Ou...

  20. Three-dimensional microfabrication using two-photon polymerization

    Science.gov (United States)

    Cumpston, Brian H.; Ehrlich, Jeffrey E.; Kuebler, Stephen M.; Lipson, Matthew; Marder, Seth R.; McCord-Maughon, D.; Perry, Joseph W.; Roeckel, Harold; Rumi, Maria Cristina

    1998-09-01

    Photopolymerization initiated by the simultaneous absorption of two photons is unique in its ability to produce complex three-dimensional (3D) structures from a single, thick photopolymer film. Strong 3D confinement of the polymerization process is not possible in other polymer microfabrication techniques such as LIGA, rapid prototyping, and conventional photoresist technology. Two-photon polymerization also permits the fabrication of 3D structures and the definition of lithographic features on non-planar surfaces. We have developed a wide array of chromophores which hold great promise for 3D microfabrication, as well as other applications, such as two-photon fluorescence imaging and 3D optical data storage. These materials are based on a donor- (pi) -donor, donor-acceptor-donor, or acceptor-donor-acceptor structural motif. The magnitude of the two-photon absorption cross-section, (delta) , and the position of the two-photon absorption maximum, (lambda) (2)max, can be controlled by varying the length of the conjugated bridge and by varying the strength of the donor/acceptor groups. In this way, chromophores have been developed which exhibit strong two- photon absorption in the range of 500 - 975 nm, in some cases as high as 4400 X 10-50 cm4 s/photon-molecule. In the case of donor-(pi) -donor structures, quantum-chemical calculations show that the large absorption cross-sections arise from the symmetric re-distribution of charge from the donor end-groups to the conjugated bridge, resulting in an electronic excited-state which is more delocalized than the ground state. For many of these molecules, two-photon excitation populates a state which is sufficiently reducing that a charge transfer reaction can occur with acrylate monomers. The efficiency of these processes can be described using Marcus theory. Under suitable conditions, such reactions can induce radical polymerization of acrylate resins. Polymerization rates have been measured, and we show that these two-photon

  1. Extreme nonlinearities in InAs/InP nanowire gain media: the two-photon induced laser

    DEFF Research Database (Denmark)

    Capua, Amir; Kami, Ouri; Eisenstein, Gadi;

    2012-01-01

    We demonstrate a novel laser oscillation scheme in an InAs / InP wire-like quantum dash gain medium. A short optical pulse excites carriers by two photon absorption which relax to the energy levels providing gain thereby enabling laser oscillations. The nonlinear dynamic interaction is analyzed...... and quantified using multi-color pump-probe measurements and shows a highly efficient nonlinear two photon excitation process which is larger by more than an order of magnitude compared to common quantum well and bulk gain media. The dynamic response of the nonlinearly induced laser line is characterized...

  2. Two-Photon Flow Cytometry

    Science.gov (United States)

    Zhog, Cheng Frank; Ye, Jing Yong; Norris, Theodore B.; Myc, Andrzej; Cao, Zhengyl; Bielinska, Anna; Thomas, Thommey; Baker, James R., Jr.

    2004-01-01

    Flow cytometry is a powerful technique for obtaining quantitative information from fluorescence in cells. Quantitation is achieved by assuring a high degree of uniformity in the optical excitation and detection, generally by using a highly controlled flow such as is obtained via hydrodynamic focusing. In this work, we demonstrate a two-beam, two- channel detection and two-photon excitation flow cytometry (T(sup 3)FC) system that enables multi-dye analysis to be performed very simply, with greatly relaxed requirements on the fluid flow. Two-photon excitation using a femtosecond near-infrared (NIR) laser has the advantages that it enables simultaneous excitation of multiple dyes and achieves very high signal-to-noise ratio through simplified filtering and fluorescence background reduction. By matching the excitation volume to the size of a cell, single-cell detection is ensured. Labeling of cells by targeted nanoparticles with multiple fluorophores enables normalization of the fluorescence signal and thus ratiometric measurements under nonuniform excitation. Quantitative size measurements can also be done even under conditions of nonuniform flow via a two-beam layout. This innovative detection scheme not only considerably simplifies the fluid flow system and the excitation and collection optics, it opens the way to quantitative cytometry in simple and compact microfluidics systems, or in vivo. Real-time detection of fluorescent microbeads in the vasculature of mouse ear demonstrates the ability to do flow cytometry in vivo. The conditions required to perform quantitative in vivo cytometry on labeled cells will be presented.

  3. Holographic Two-Photon Induced Photopolymerization

    Data.gov (United States)

    Federal Laboratory Consortium — Holographic two-photon-induced photopolymerization (HTPIP) offers distinct advantages over conventional one-photon-induced photopolymerization and current techniques...

  4. Two-Photon-Pumped Perovskite Semiconductor Nanocrystal Lasers.

    Science.gov (United States)

    Xu, Yanqing; Chen, Qi; Zhang, Chunfeng; Wang, Rui; Wu, Hua; Zhang, Xiaoyu; Xing, Guichuan; Yu, William W; Wang, Xiaoyong; Zhang, Yu; Xiao, Min

    2016-03-23

    Two-photon-pumped lasers have been regarded as a promising strategy to achieve frequency up-conversion for situations where the condition of phase matching required by conventional approaches cannot be fulfilled. However, their practical applications have been hindered by the lack of materials holding both efficient two-photon absorption and ease of achieving population inversion. Here, we show that this challenge can be tackled by employing colloidal nanocrystals of perovskite semiconductors. We observe highly efficient two-photon absorption (with a cross section of 2.7 × 10(6) GM) in toluene solutions of CsPbBr3 nanocrystals that can excite large optical gain (>500 cm(-1)) in thin films. We have succeeded in demonstrating stable two-photon-pumped lasing at a remarkable low threshold by coupling CsPbBr3 nanocrystals with microtubule resonators. Our findings suggest perovskite nanocrystals can be used as excellent gain medium for high-performance frequency-up-conversion lasers toward practical applications.

  5. Resonant two-photon ionization of phenol in methylene chloride doped solid argon using 248 nm KrF laser and 254 nm Hg lamp radiation, a comparative study. The UV/VIS absorption spectrum of phenol radical cation

    Science.gov (United States)

    Kesper, Karl; Diehl, Frank; Simon, Jens Georg Günther; Specht, Harald; Schweig, Armin

    1991-06-01

    Resonant two-photon ionization (TPI) of phenol (PhOH) has been successfully achieved in methylene chloride (CH 2Cl 2) doped solid argon using a KrF laser and a Hg resonance lamp. The result constitutes the first-time TPI of a typically organic molecule in this medium using an excimer laser as well as the first-time spectroscopic identification of PhOH +•. A qualitative model is proposed which is consistent with both the unexpected photostability of PhOH +• and the incomplete running of the TPI process in the applied medium.

  6. Synthesis of two carbazole-based dyes and application of two-photon initiating polymerization

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Two carbazole-based polymerization initiators possessing blue fluorescence emission have been synthesized via Wittig reaction in the solid phase at room temperature.Two-photon excited fluorescence(TPEF) spectra for them were investigated under 800 nm fs laser pulse and two-photon absorption cross sections were determined by the Z-scan technique.Then two-photon initiating polymerization(TPIP) microfabrication experiments were successfully carried out.Three-dimensional lattice and artificial defects were gained,indicating that they were viable candidates for the two-photon polymerization initiator in practical application of microfabrication.

  7. Synthesis of two carbazole-based dyes and application of two-photon initiating polymerization

    Institute of Scientific and Technical Information of China (English)

    HU RenTao; LU LiangFei; RUAN BanFeng; WANG Peng; ZHANG MingLiang; ZHOU HongPing; LI ShengLi; WU JieYing; TIAN YuPeng

    2009-01-01

    Two carbazole-based polymerization initiators possessing blue fluorescence emission have been synthesized via Wittig reaction in the solid phase at room temperature.Two-photon excited fluorescence (TPEF) spectra for them were investigated under 800 nm fs laser pulse and two-photon absorption cross sections were determined by the Z-scan technique.Then two-photon initiating polymerization (TPIP) microfabrication experiments were successfully carried out.Three-dimensional lattice and artificial defects were gained,indicating that they were viable candidates for the two-photon polymerization initiator in practical application of microfabrication.

  8. Absorption mapping for characterization of glass surfaces.

    Science.gov (United States)

    Commandré, M; Roche, P; Borgogno, J P; Albrand, G

    1995-05-01

    The surface quality of bare substrates and preparation procedures take on an important role in optical coating performances. The most commonly used techniques of characterization generally give information about roughness and local defects. A photothermal deflection technique is used for mapping surface absorption of fused-silica and glass substrates. We show that absorption mapping gives specific information on surface contamination of bare substrates. We present experimental results concerning substrates prepared by different cleaning and polishing techniques. We show that highly polished surfaces lead to the lowest values of residual surface absorption. Moreover the cleaning behavior of surfaces of multicomponent glasses and their optical performance in terms of absorption are proved to be different from those of fused silica.

  9. Non-linear imaging and characterization of atherosclerotic arterial tissue using combined two photon fluorescence, second-harmonic generation and CARS microscopy

    Science.gov (United States)

    Cicchi, Riccardo; Matthäus, Christian; Meyer, Tobias; Lattermann, Annika; Dietzek, Benjamin; Brehm, Bernhard R.; Popp, Jürgen; Pavone, Francesco S.

    2014-02-01

    Atherosclerosis is among the most widespread cardiovascular diseases and one of the leading cause of death in the Western World. Characterization of arterial tissue in atherosclerotic condition is extremely interesting from the diagnostic point of view. Routinely used diagnostic methods, such as histopathological examination, are limited to morphological analysis of the examined tissues, whereas an exhaustive characterization requires a morpho-functional approach. Multimodal non-linear microscopy has the potential to bridge this gap by providing morpho-functional information on the examined tissues in a label-free way. Here we employed multiple non-linear microscopy techniques, including CARS, TPF, and SHG to provide intrinsic optical contrast from various tissue components in both arterial wall and atherosclerotic plaques. CARS and TPF microscopy were used to respectively image lipid depositions within plaques and elastin in the arterial wall. Cholesterol deposition in the lumen and collagen in the arterial wall were selectively imaged by SHG microscopy and distinguished by forward-backward SHG ratio. Image pattern analysis allowed characterizing collagen organization in different tissue regions. Different values of fiber mean size, distribution and anisotropy are calculated for lumen and media prospectively allowing for automated classification of atherosclerotic lesions. The presented method represents a promising diagnostic tool for evaluating atherosclerotic tissue and has the potential to find a stable place in clinical setting as well as to be applied in vivo in the near future.

  10. Synthesis and Nonlinear Optical Properties of a New Two-photon Polymerization Initiator: DPAMOB with a Large TPA Cross-section

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xian; YU Xiao-Qiang; ZHANG Bao-Qin; FENG Yun-Guo; TAO Xu-Tang; JIANG Min-Hua

    2006-01-01

    E,E-1,4-Bis(4′-N,N-diphenylaminostyryl)-2,5-dimethoxybenzene (DPAMOB) has been synthesized by a simple and effective solid phase Wittig reaction and characterized by 1H NMR spectra and elemental analysis. Linear absorption, single-photon induced fluorescence and two-photon induced fluorescence spectra were experimentally studied. The new dye has a large two-photon absorption (TPA) cross-section of σr= 1007.2 GM [1 GM= 1 × 10-50results confirm that DPAMOB is a good TPA chromophore and can successfully initiate two-photon photopolymerization of ethoxylated trimethylolpropane triacrylate esters (SR454). Finally, a microstructure has been fabricated by use of DPAMOB as initiator.

  11. Modulation of attosecond beating by resonant two-photon transition

    CERN Document Server

    Galán, Álvaro Jiménez; Martín, Fernando

    2015-01-01

    We present an analytical model that characterizes two-photon transitions in the presence of autoionising states. We applied this model to interpret resonant RABITT spectra, and show that, as a harmonic traverses a resonance, the phase of the sideband beating significantly varies with photon energy. This phase variation is generally very different from the $\\pi$ jump observed in previous works, in which the direct path contribution was negligible. We illustrate the possible phase profiles arising in resonant two-photon transitions with an intuitive geometrical representation.

  12. Exploring control parameters of two photon processes in solutions

    Indian Academy of Sciences (India)

    Debabrata Goswami; Amit Nag

    2012-01-01

    Two-photon microscopy depends extensively on the two-photon absorption cross-sections of biologically relevant chromophores. High repetition rate (HRR) lasers are essential in multiphoton microscopy for generating satisfactory signal to noise at low average powers. However, HRR lasers generate thermal distortions in samples even with the slightest single photon absorption. We use an optical chopper with HRR lasers to intermittently `blank’ irradiation and effectively minimize thermal effects to result in a femtosecond z-scan setup that precisely measures the two-photon absorption (TPA) cross-sections of chromophores. Though several experimental factors impact such TPA measurements, a systematic effort to modulate and influence TPA characteristics is yet to evolve. Here, we present the effect of several control parameters on the TPA process that are independent of chromophore characteristics for femtosecond laser pulse based measurements; and demonstrate how the femtosecond laser pulse repetition rate, chromophore environment and incident laser polarization can become effective control parameters for such nonlinear optical properties.

  13. Two-photon absorbing porphyrins for oxygen microscopy (Conference Presentation)

    Science.gov (United States)

    Esipova, Tatiana V.; Vinogradov, Sergei A.

    2016-03-01

    The ability to quantify oxygen in vivo in 3D with high spatial and temporal resolution is invaluable for many areas of the biomedical science, including ophthalmology, neuroscience, cancer and stem biology. An optical method based on oxygen-dependent quenching of phosphorescence is being developed, that allows quantitative minimally invasive real-time imaging of partial pressure of oxygen (pO2) in tissue. In the past, dendritically protected phosphorescent oxygen probes with controllable quenching parameters and defined bio-distributions have been developed. More recently our probe strategy has extended to encompass two-photon excitable oxygen probes, which brought about first demonstrations of two-photon phosphorescence lifetime microscopy (2PLM) of oxygen in vivo, providing new valuable information for neuroscience and stem cell biology. However, current two-photon oxygen probes suffer from a number of limitations, such as low brightness and high cost of synthesis, which dramatically reduce imaging performance and limit usability of the method. Here we present an approach to new bright phosphorescent chromophores with internally enhanced two-photon absorption cross-sections, which pave a way to novel proves for 2PLM. In addition to substantial increase in performance, the new probes can be synthesized by much more efficient methods, thereby greatly reducing the cost of the synthesis and making the technique accessible to a broader range of researchers across different fields.

  14. Fano interference in two-photon transport

    Science.gov (United States)

    Xu, Shanshan; Fan, Shanhui

    2016-10-01

    We present a general input-output formalism for the few-photon transport in multiple waveguide channels coupled to a local cavity. Using this formalism, we study the effect of Fano interference in two-photon quantum transport. We show that the physics of Fano interference can manifest as an asymmetric spectral line shape in the frequency dependence of the two-photon correlation function. The two-photon fluorescence spectrum, on the other hand, does not exhibit the physics of Fano interference.

  15. Adiabatic following in two-photon transition

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, M.H.; Nayfeh, A.H.

    1977-01-01

    There has been much interest recently in coherent multiphoton transitions in many-level systems. The present work considers the effect of relaxation in the response of a three-level system to a smoothly varying, near-resonant, two-photon field. The relaxation-dependent contributions to the nonlinear refractive index are calculated. It is shown that the coherent interaction of two smoothly varying, near-resonant, two-photon pulses with a three-level system can be described by ''two-photon damped Bloch equations'' which are analogous to those for a one-photon transition in a two-level system except for the presence of a two-photon coupling and a frequency shift. 1 figure. (RWR)

  16. Two-Photon Physics in Hadronic Processes

    Energy Technology Data Exchange (ETDEWEB)

    Carl Carlson; Marc Vanderhaeghen

    2007-11-01

    Two-photon exchange contributions to elastic electron-scattering are reviewed. The apparent discrepancy in the extraction of elastic nucleon form factors between unpolarized Rosenbluth and polarization transfer experiments is discussed, as well as the understanding of this puzzle in terms of two-photon exchange corrections. Calculations of such corrections both within partonic and hadronic frameworks are reviewed. In view of recent spin-dependent electron scattering data, the relation of the two-photon exchange process to the hyperfine splitting in hydrogen is critically examined. The imaginary part of the two-photon exchange amplitude as can be accessed from the beam normal spin asymmetry in elastic electron-nucleon scattering is reviewed. Further extensions and open issues in this field are outlined.

  17. Correlations of two photons at hadron colliders

    OpenAIRE

    Kozlov, G. A.

    2011-01-01

    We study the Bose-Einstein correlations of two photons and their coherent properties that can provide the information about the space-time structure of the emitting source through the Higgs-boson decays into two photons. We argue that such an investigation could probe the Higgs-boson mass. The model is rather sensitive to the temperature of the environment and to the external distortion effect in medium.

  18. Spectral Features of FM Spectroscopy of Two-Photon Interactions

    Institute of Scientific and Technical Information of China (English)

    夏慧荣; JohnL.Hall

    1994-01-01

    The spectral features of FM two-photon resonant interaction processes have been calculated for five different frequency modulation versions of counter-propagating incident fields. It is found that the proposed new modulation version (case b in the text) provides novel spectral features for a completely canceled absorption and a sharp dispersion shape at the fundamental beat note. Moreover, its absorption feature appears at the second harmonic of the RF modulation frequency generated by the joint modes via six interaction pathways without mutual phase shift. Such features persist even when the effects of the second-order sidebands of the incident fields are taken into account. Application potentials are emphasized.

  19. Synthesis of Two-Photon Materials and Two-Photon Liquid Crystals

    Science.gov (United States)

    Subramaniam, Girija

    2001-01-01

    The duration of the grant was interrupted by two major accidents that the PI met with-- an auto accident in Pasadena, CA during her second summer at JPL which took almost eight months for recovery and a second accident during Fall 2000 that left her in crutches for the entire semester. Further, the time released agreed by the University was not given in a timely fashion. The candidate has been given post-grant expire time off. In spite of all these problems, the PI synthesized a number of new two-photon materials and studied the structure-activity correlation to arrive at the best-optimized structure. The PI's design proved to be one of the best in the sense that these materials has a hitherto unreported two-photon absorption cross section. Many materials based on PI's design was later made by the NASA colleague. This is Phase 1. Phase II of this grant is to orate liquid crystalline nature into this potentially useful materials and is currently in progress. Recent observations of nano- and pico-second response time of homeotropically aligned liquid crystals suggest their inherent potentials to act as laser hardening materials, i.e., as protective devices against short laser pulses. The objective of the current project is to exploit this potential by the synthesis of liquid crystals with high optical nonlinearity and optimizing their performance. The PI is trying structural variations to bring in liquid crystalline nature without losing the high two-photon cross section. Both Phase I and Phase II led to many invited presentations and publications in reputed journals like 'Science' and 'Molecular Crystals'. The list of presentations and reprints are enclosed. Another important and satisfying outcome of this grant is the opportunity that this grant offered to the budding undergraduate scientists to get involved in a visible research of international importance. All the students had a chance to learn a lot during research, had the opportunity to present their work at

  20. Two-photon-induced cycloreversion reaction of chalcone photodimers

    Science.gov (United States)

    Träger, J.; Härtner, S.; Heinzer, J.; Kim, H.-C.; Hampp, N.

    2008-04-01

    The photocleavage reaction of chalcone photodimers has been studied using a two-photon process. For this purpose, a novel chalcone dimer has been synthesized as a low molecular weight model substance for polymer bound chalcones and its photochemistry triggered by two-photon-absorption (2PA) has been investigated using a pulsed frequency-doubled Nd:YAG-laser. The 2PA-induced cycloreversion reaction selectively leads to the cleavage of the chalcone photodimers resulting in the formation of monomeric chalcone molecules. Hence, as an application chalcones can be used as a photosensitive linker which can be cleaved beyond an UV-absorbing barrier. The 2PA cross section of the chalcone photodimer was determined to be of 1.1 × 10 -49 cm 4 s photon -1 (11 GM).

  1. Two-photon vibrational excitation of air by long-wave infrared laser pulses

    CERN Document Server

    Palastro, J P; Johnson, L A; Hafizi, B; Wahlstrand, J K; Milchberg, H M

    2016-01-01

    Ultrashort long-wave infrared (LWIR) laser pulses can resonantly excite vibrations in N2 and O2 through a two-photon transition. The absorptive, vibrational component of the ultrafast optical nonlinearity grows in time, starting smaller than, but quickly surpassing, the electronic, rotational, and vibrational refractive components. The growth of the vibrational component results in a novel mechanism of 3rd harmonic generation, providing an additional two-photon excitation channel, fundamental + 3rd harmonic. The original and emergent two-photon excitations drive the resonance exactly out of phase, causing spatial decay of the absorptive, vibrational nonlinearity. This nearly eliminates two-photon vibrational absorption. Here we present simulations and analytical calculations demonstrating how these processes modify the ultrafast optical nonlinearity in air. The results reveal nonlinear optical phenomena unique to the LWIR regime of ultrashort pulse propagation in atmosphere.

  2. A new approach to dual-color two-photon microscopy with fluorescent proteins

    Directory of Open Access Journals (Sweden)

    Rebane Aleks

    2010-02-01

    Full Text Available Abstract Background Two-photon dual-color imaging of tissues and cells labeled with fluorescent proteins (FPs is challenging because most two-photon microscopes only provide one laser excitation wavelength at a time. At present, methods for two-photon dual-color imaging are limited due to the requirement of large differences in Stokes shifts between the FPs used and their low two-photon absorption (2PA efficiency. Results Here we present a new method of dual-color two-photon microscopy that uses the simultaneous excitation of the lowest-energy electronic transition of a blue fluorescent protein and a higher-energy electronic transition of a red fluorescent protein. Conclusion Our method does not require large differences in Stokes shifts and can be extended to a variety of FP pairs with larger 2PA efficiency and more optimal imaging properties.

  3. Two Photon Couplings of Hybrid Mesons

    CERN Document Server

    Page, P R

    1996-01-01

    A new formalism is developed for the two photon production of hybrid mesons via intermediate hadronic decays. In an adiabatic and non--relativistic context with spin 1 pair creation we obtain the first absolute estimates of unmixed hybrid production strengths to be small (0.03 - 3 eV) in relation to experimental meson widths (0.1 - 5 keV). Within this context, two photon collisions therefore strongly discriminate between hybrid and conventional meson wave function components at BaBar, Cleo II, LEP2 and LHC, filtering out non--gluonic components. Decay widths of unmixed hybrids are tiny. The formalism also induces conventional meson two photon widths roughly in agreement with experiment.

  4. Tuning Ag29 nanocluster light emission from red to blue with one and two-photon excitation

    Science.gov (United States)

    Russier-Antoine, Isabelle; Bertorelle, Franck; Hamouda, Ramzi; Rayane, Driss; Dugourd, Philippe; Sanader, Željka; Bonačić-Koutecký, Vlasta; Brevet, Pierre-François; Antoine, Rodolphe

    2016-01-01

    We demonstrate that the tuning of the light emission from red to blue in dihydrolipoic acid (DHLA) capped Ag29 nanoclusters can be trigged with one and two photon excitations. The cluster stoichiometry was determined with mass spectrometry and found to be Ag29(DHLA)12. In a detailed optical investigation, we show that these silver nanoclusters exhibit a strong red photoluminescence visible to the naked eye and characterized by a quantum yield of nearly ~2% upon one-photon excitation. In the nonlinear optical (NLO) study of the properties of the clusters, the two-photon excited fluorescence spectra were recorded and their first hyperpolarizability obtained. The two-photon absorption cross-section at ~800 nm for Ag29(DHLA)12 is higher than 104 GM and the hyperpolarizability is 106 × 10-30 esu at the same excitation wavelength. The two-photon excited fluorescence spectrum appears strongly blue-shifted as compared to the one-photon excited spectrum, displaying a broad band between 400 and 700 nm. The density functional theory (DFT) provides insight into the structural and electronic properties of Ag29(DHLA)12 as well as into interplay between metallic subunit or core and ligands which is responsible for unique optical properties.We demonstrate that the tuning of the light emission from red to blue in dihydrolipoic acid (DHLA) capped Ag29 nanoclusters can be trigged with one and two photon excitations. The cluster stoichiometry was determined with mass spectrometry and found to be Ag29(DHLA)12. In a detailed optical investigation, we show that these silver nanoclusters exhibit a strong red photoluminescence visible to the naked eye and characterized by a quantum yield of nearly ~2% upon one-photon excitation. In the nonlinear optical (NLO) study of the properties of the clusters, the two-photon excited fluorescence spectra were recorded and their first hyperpolarizability obtained. The two-photon absorption cross-section at ~800 nm for Ag29(DHLA)12 is higher than 104

  5. Cyanines as new fluorescent probes for DNA detection and two-photon excited bioimaging.

    Science.gov (United States)

    Feng, Xin Jiang; Wu, Po Lam; Bolze, Frédéric; Leung, Heidi W C; Li, King Fai; Mak, Nai Ki; Kwong, Daniel W J; Nicoud, Jean-François; Cheah, Kok Wai; Wong, Man Shing

    2010-05-21

    A series of cyanine fluorophores based on fused aromatics as an electron donor for DNA sensing and two-photon bioimaging were synthesized, among which the carbazole-based biscyanine exhibits high sensitivity and efficiency as a fluorescent light-up probe for dsDNA, which shows selective binding toward the AT-rich regions. The synergetic effect of the bischromophoric skeleton gives a several-fold enhancement in a two-photon absorption cross-section as well as a 25- to 100-fold enhancement in two-photon excited fluorescence upon dsDNA binding.

  6. Two-photon physics at LEP2

    Energy Technology Data Exchange (ETDEWEB)

    Cartwright, Susan; Lehto, Mark [University of Sheffield Department of Physics, Sheffield S3 7RH (United Kingdom); Seymour, Michael H.; Close, Frank; Wright, Alison [Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Affholderbach, Klaus; Cowan, Glen [Universitaet Siegen, Fachbereich Physik, D-57068 Siegen (Germany); Finch, Alex [University of Lancaster, Lancaster LA1 4YB (United Kingdom); Lauber, Jan [University College London, Gower Street, London WC1E 6BT (United Kingdom)

    1998-02-01

    The working group on two-photon physics concentrated on three main subtopics: modelling the hadronic final state of deep inelastic scattering on a photon; unfolding the deep inelastic scattering data to obtain the photon structure function; and resonant production of exclusive final states, particularly of glueball candidates. In all three areas, new results were presented. (author)

  7. Two-photon quantum interference in plasmonics: theory and applications.

    Science.gov (United States)

    Gupta, S Dutta; Agarwal, G S

    2014-01-15

    We report perfect two-photon quantum interference with near-unity visibility in a resonant tunneling plasmonic structure in folded Kretschmann geometry. This is despite absorption-induced loss of unitarity in plasmonic systems. The effect is traced to perfect destructive interference between the squares of amplitude reflection and transmission coefficients. We further highlight yet another remarkable potential of coincidence measurements as a probe with better resolution as compared to standard spectroscopic techniques. The finer features show up in both angle resolved and frequency resolved studies.

  8. Two-Photon Activation of p-Hydroxyphenacyl Phototriggers: Toward Spatially Controlled Release of Diethyl Phosphate and ATP.

    Science.gov (United States)

    Houk, Amanda L; Givens, Richard S; Elles, Christopher G

    2016-03-31

    Two-photon activation of the p-hydroxyphenacyl (pHP) photoactivated protecting group is demonstrated for the first time using visible light at 550 nm from a pulsed laser. Broadband two-photon absorption measurements reveal a strong two-photon transition (>10 GM) near 4.5 eV that closely resembles the lowest-energy band at the same total excitation energy in the one-photon absorption spectrum of the pHP chromophore. The polarization dependence of the two-photon absorption band is consistent with excitation to the same S3 ((1)ππ*) excited state for both one- and two-photon activation. Monitoring the progress of the uncaging reaction under nonresonant excitation at 550 nm confirms a quadratic intensity dependence and that two-photon activation of the uncaging reaction is possible using visible light in the range 500-620 nm. Deprotonation of the pHP chromophore under mildly basic conditions shifts the absorption band to lower energy (3.8 eV) in both the one- and two-photon absorption spectra, suggesting that two-photon activation of the pHP chromophore may be possible using light in the range 550-720 nm. The results of these measurements open the possibility of spatially and temporally selective release of biologically active compounds from the pHP protecting group using visible light from a pulsed laser.

  9. Modulation of attosecond beating in resonant two-photon ionization

    CERN Document Server

    Galán, Álvaro J; Martín, Fernando

    2014-01-01

    We present a theoretical study of the photoelectron attosecond beating at the basis of RABBIT (Reconstruction of Attosecond Beating By Interference of Two-photon transitions) in the presence of autoionizing states. We show that, as a harmonic traverses a resonance, its sidebands exhibit a peaked phase shift as well as a modulation of the beating frequency itself. Furthermore, the beating between two resonant paths persists even when the pump and the probe pulses do not overlap, thus providing a sensitive non-holographic interferometric means to reconstruct coherent metastable wave packets. We characterize these phenomena quantitatively with a general finite-pulse analytical model that accounts for the effect of both intermediate and final resonances on two-photon processes, at a negligible computational cost. The model predictions are in excellent agreement with those of accurate ab initio calculations for the helium atom in the region of the N=2 doubly excited states.

  10. Transparency induced by two photon interference in a beam splitter

    Institute of Scientific and Technical Information of China (English)

    Wang Kai-Ge; Yang Guo-Jian

    2004-01-01

    We propose a special two-photon state which is completely transparent in a 50/50 beam splitter. This effect is caused by the destructive two-photon interference and shows the signature of photon entanglement. We find that the symmetry of the two-photon spectrum plays the key role for the properties of two-photon interference.

  11. Two-photon cooling of magnesium atoms

    DEFF Research Database (Denmark)

    Malossi, N.; Damkjær, S.; Hansen, P. L.

    2005-01-01

    A two-photon mechanism for cooling atoms below the Doppler temperature is analyzed. We consider the magnesium ladder system (3s2)S01¿(3s3p)P11 at 285.2nm followed by the (3s3p)P11¿(3s3d)D21 transition at 880.7nm . For the ladder system quantum coherence effects may become important. Combined...... with the basic two-level Doppler cooling process this allows for reduction of the atomic sample temperature by more than a factor of 10 over a broad frequency range. First experimental evidence for the two-photon cooling process is presented and compared to model calculations. Agreement between theory...... and experiment is excellent. In addition, by properly choosing the Rabi frequencies of the two optical transitions a velocity independent atomic dark state is observed....

  12. Magnetic two-photon scattering and two-photon emission - Cross sections and redistribution functions

    Science.gov (United States)

    Alexander, S. G.; Meszaros, P.

    1991-01-01

    The magnetic two-photon scattering cross section is discussed within the framework of QED, and the corresponding scattering redistribution function for this process and its inverse, as well as the scattering source function are calculated explicitly. In a similar way, the magnetic two-photon emission process which follows the radiative excitation of Landau levels above ground is calculated. The two-photon scattering and two-photon emission are of the same order as the single-photon magnetic scattering. All three of these processes, and in optically thick cases also their inverses, are included in radiative transport calculations modeling accreting pulsars and gamma-ray bursters. These processes play a prominent role in determining the relative strength of the first two cyclotron harmonics, and their effects extend also to the higher harmonics.

  13. Two-photon cooling of magnesium atoms

    DEFF Research Database (Denmark)

    Malossi, N.; Damkjær, S.; Hansen, P. L.;

    2005-01-01

    A two-photon mechanism for cooling atoms below the Doppler temperature is analyzed. We consider the magnesium ladder system (3s2)S01¿(3s3p)P11 at 285.2nm followed by the (3s3p)P11¿(3s3d)D21 transition at 880.7nm . For the ladder system quantum coherence effects may become important. Combined...

  14. Two-Photon Collective Atomic Recoil Lasing

    Directory of Open Access Journals (Sweden)

    James A. McKelvie

    2015-11-01

    Full Text Available We present a theoretical study of the interaction between light and a cold gasof three-level, ladder configuration atoms close to two-photon resonance. In particular, weinvestigate the existence of collective atomic recoil lasing (CARL instabilities in differentregimes of internal atomic excitation and compare to previous studies of the CARL instabilityinvolving two-level atoms. In the case of two-level atoms, the CARL instability is quenchedat high pump rates with significant atomic excitation by saturation of the (one-photoncoherence, which produces the optical forces responsible for the instability and rapid heatingdue to high spontaneous emission rates. We show that in the two-photon CARL schemestudied here involving three-level atoms, CARL instabilities can survive at high pump rateswhen the atoms have significant excitation, due to the contributions to the optical forces frommultiple coherences and the reduction of spontaneous emission due to transitions betweenthe populated states being dipole forbidden. This two-photon CARL scheme may form thebasis of methods to increase the effective nonlinear optical response of cold atomic gases.

  15. Two-photon super bunching of thermal light via multiple two-photon-path interference

    CERN Document Server

    Hong, Peilong; Zhang, Guoquan

    2012-01-01

    We propose a novel scheme to achieve two-photon super bunching of thermal light through multiple two-photon-path interference, in which two mutually first-order incoherent optical channels are introduced by inserting a modified Michelson interferometer into a traditional two-photon HBT interferometer, and the bunching peak-to-background ratio can reach 3 theoretically. Experimentally, the super bunching peak-to-background ratio was measured to be 2.4, much larger than the ratio 1.7 measured with the same thermal source in a traditional HBT interferometer. The peak-to-background ratio of two-photon super bunching of thermal light can be increased up to $2\\times1.5^n$ by inserting cascadingly $n$ pairs of mutually first-order incoherent optical channels into the traditional two-photon HBT interferometer. The two-photon super bunching of thermal light should be of great significance in improving the visibility of classical ghost imaging.

  16. Localized Polymerization Using Single Photon Photoinitiators in Two-photon process for Fabricating Subwavelength Structures

    CERN Document Server

    Ummethala, Govind; Chaudhary, Raghvendra P; Hawal, Suyog; Saxena, Sumit; Shukla, Shobha

    2016-01-01

    Localized polymerization in subwavelength volumes using two photon dyes has now become a well-established method for fabrication of subwavelength structures. Unfortunately, the two photon absorption dyes used in such process are not only expensive but also proprietary. LTPO-L is an inexpensive, easily available single photon photoinitiator and has been used extensively for single photon absorption of UV light for polymerization. These polymerization volumes however are not localized and extend to micron size resolution having limited applications. We have exploited high quantum yield of radicals of LTPO-Lfor absorption of two photons to achieve localized polymerization in subwavelength volumes, much below the diffraction limit. Critical concentration (10wt%) of LTPO-Lin acrylate (Sartomer) was found optimal to achieve subwavelength localized polymerization and has been demonstrated by fabricating 2D/3D complex nanostructures and functional devices such as variable polymeric gratings with nanoscaled subwavelen...

  17. Observation of Nondegenerate Two-Photon Gain in GaAs

    CERN Document Server

    Reichert, Matthew; Salamo, Greg; Hagan, David J; Van Stryland, Eric W

    2016-01-01

    Two-photon lasers require materials with large two-photon gain (2PG) coefficients and low linear and nonlinear losses. Our previous demonstration of large enhancement of two-photon absorption in semiconductors for very different photon energies translates directly into enhancement of 2PG. We experimentally demonstrate nondegenerate 2PG in optically excited bulk GaAs via femtosecond pump-probe measurements. 2PG is isolated from other pump induced effects through the difference between measurements performed with parallel and perpendicular polarizations of pump and probe. An enhancement in the 2PG coefficient of nearly two orders-of-magnitude is reported. The results point a possible way toward two-photon semiconductor lasers.

  18. Two Photon Induced Lasing in 1550 nm Quantum Dash Optical Gain Media

    DEFF Research Database (Denmark)

    Capua, Amir; Saal, Abigael; Reithmaier, Johann Peter

    2011-01-01

    We report on a unique lasing mechanism observed in quantum dash Gain media. While the gain media is electrically pumped below lasing threshold, a strong optical pulse excites carriers by two photon absorption into high energy states of the quantum dashes and wetting layer. Fast inter band carrier...... by the XFROG scheme is performed. We show the lasing mechanism to be governed mainly by the wetting layer dynamics and extract a direct measurement of the carrier-carrier scattering time constant....... relaxation and capture processes into the ground states of the quantum dashes result in increased gain followed by lasing at the gain peak irrespective of the stimulating pulse wavelength. The temporal response of the lasing line is examined on a 40 GHz scope and full characterization of the pulse...

  19. A [111]-Cut Si Hemisphere Two-Photon Response Photodetector

    Institute of Scientific and Technical Information of China (English)

    LIU Xiu-Huan; CHEN Zhan-Guo; JIA Gang; WANG Hai-Yan; GAO Yan-Jun; LI Yi1

    2011-01-01

    Properties of two-photon response in a [lll]-cut nearly-intrinsic Si hemisphere photodetector are studied. The measured photocurrent of the photodetector responding to the 1.32μm continuous wave laser shows a quadratic dependence on the coupled optical power and is saturated with the bias voitage. Also, the photocurrent is independent of polarization. Such properties are in good agreement with the theory of two-photon absorption. The isotropic photocurrent generated from the [lll]-cut Si hemisphere is compared to the anisotropic one induced in the [110]-cut Si sample and the ratio of Xxxxx /Xxxyy for silicon performing at 1.32μm is calculated to be 2.4 via the fitted function of the anisotropic photocurrent from the [110]-cut sample.%Properties of two-photon response in a [111]-cut nearly-intrinsic Si hemisphere photodetector are studied.The measured photocurrent of the photodetector responding to the 1.32 μm continuous wave laser shows a quadratic dependence on the coupled optical power and is saturated with the bias voltage.Also,the photocurrent is independent of polarization.Such properties are in good agreement with the theory of two-photon absorption.The isotropic photocurrent generated from the [111]-cut Si hemisphere is compared to the anisotropic one induced in the [110]-cut Si sample and the ratio of Xxxxx /Xxxyy for silicon performing at 1.32μm is calculated to be 2.4via the fitted function of the anisotropic photocurrent from the [110]-cut sample.Silicon materials have a variety of applications in microelectronics and silicon optoelectronics and are still attractive to relevant researchers.Commercial Si photodetectors are largely designed based on singlephoton absorption (SPA).However,nonlinear characteristics have been exhibited in silicon devices.Specifically,two-photon absorption (TPA) has attracted much attention in such devices of Si p-n and p-i-n photodiodes,Si waveguides and Si avalanche diodes,etc.for the autocorrelation measurements of

  20. Ab initio study of the one- and two-photon circular dichroism of R-(+)-3-methyl-cyclopentanone

    Science.gov (United States)

    Rizzo, Antonio; Lin, Na; Ruud, Kenneth

    2008-04-01

    One- and two-photon circular dichroism spectra of R-(+)-3-methyl-cyclopentanone, a system that has been the subject of recent experimental studies of (2+1) resonance-enhanced multiphoton ionization circular dichroism, have been calculated with an origin-invariant density functional theory approximation in the region of the lowest electronic excited states, both for the gas phase and for a selection of solvents. A polarizable continuum model is used in the calculations performed on the solvated system. Two low-lying conformers are analyzed, and a comparison of the intensities and characteristic features is made with the corresponding two-photon absorption for each species, also for the Boltzmann-averaged spectra. The effect of the choice of geometry, basis set, and exchange-correlation functional is carefully analyzed. It is found that a density functional theory approach using the Coulomb attenuating method variant of Becke's three-parameter exchange and the Lee-Yang-Parr correlation functionals with correlation-consistent basis sets of double-zeta quality can reproduce the experimental electronic circular dichroism spectra very well. The features appearing in experiment are characterized in terms of molecular excitations, and the differences in the response of each state in the one- and two-photon processes are highlighted.

  1. Two-photon-excited fluorescence spectroscopy of atomic fluorine at 170 nm

    Science.gov (United States)

    Herring, G. C.; Dyer, Mark J.; Jusinski, Leonard E.; Bischel, William K.

    1988-01-01

    Two-photon-excited fluorescence spectroscopy of atomic fluorine is reported. A doubled dye laser at 286-nm is Raman shifted in H2 to 170 nm (sixth anti-Stokes order) to excite ground-state 2P(0)J fluorine atoms to the 2D(0)J level. The fluorine atoms are detected by one of two methods: observing the fluorescence decay to the 2PJ level or observing F(+) production through the absorption of an additional photon by the excited atoms. Relative two-photon absorption cross sections to and the radiative lifetimes of the 2D(0)J states are measured.

  2. Adiabatic following in two-photon transition

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, M.H.; Nayfeh, A.H.

    1977-03-01

    The coherent interaction of two smoothly varying, near-resonant, two-photon pulses with a three-level system can be described by ''two-photon damped Bloch equations'' which are analogous to those for a one-photon transition in a two-level system except for the presence of a two-photon coupling and a frequency shift. These equations are solved for the cases ..gamma../sub 1/, ..gamma../sub 2/ very-much-less-than ..cap omega.., ..gamma../sub 1/ = ..gamma../sub 2/, and ..gamma../sub 2/k/sup 2/epsilon/sup 4//..cap omega../sup 2/, ..gamma../sub 1/ very-much-less-than ..cap omega.., where ..gamma../sub 1/ and ..gamma../sub 2/ are the atomic energy and phase relaxation widths, respectively, and ..cap omega.. is the Rabi frequency. The leading contribution to the refractive index is intensity dependent, caused by the level shifts inherent in multiphoton processes; it includes a relaxation dependent part which is important at times shorter than ..gamma../sup -1//sub 1/. The second-order contributions depend on the square of the intensity and the time-integrated square of the intensity. The latter contribution, which is relaxation dependent, causes line asymmetry at the long-wavelength wing; it consists of a term proportional to ..gamma../sub 2/-..gamma../sub 1/ and only important at early times and a term proportional to 2..gamma../sub 2/-..gamma../sub 1/.

  3. Denoising two-photon calcium imaging data.

    Science.gov (United States)

    Malik, Wasim Q; Schummers, James; Sur, Mriganka; Brown, Emery N

    2011-01-01

    Two-photon calcium imaging is now an important tool for in vivo imaging of biological systems. By enabling neuronal population imaging with subcellular resolution, this modality offers an approach for gaining a fundamental understanding of brain anatomy and physiology. Proper analysis of calcium imaging data requires denoising, that is separating the signal from complex physiological noise. To analyze two-photon brain imaging data, we present a signal plus colored noise model in which the signal is represented as harmonic regression and the correlated noise is represented as an order autoregressive process. We provide an efficient cyclic descent algorithm to compute approximate maximum likelihood parameter estimates by combing a weighted least-squares procedure with the Burg algorithm. We use Akaike information criterion to guide selection of the harmonic regression and the autoregressive model orders. Our flexible yet parsimonious modeling approach reliably separates stimulus-evoked fluorescence response from background activity and noise, assesses goodness of fit, and estimates confidence intervals and signal-to-noise ratio. This refined separation leads to appreciably enhanced image contrast for individual cells including clear delineation of subcellular details and network activity. The application of our approach to in vivo imaging data recorded in the ferret primary visual cortex demonstrates that our method yields substantially denoised signal estimates. We also provide a general Volterra series framework for deriving this and other signal plus correlated noise models for imaging. This approach to analyzing two-photon calcium imaging data may be readily adapted to other computational biology problems which apply correlated noise models.

  4. Nonresonant two-photon transitions in length and velocity gauges

    Science.gov (United States)

    Jentschura, U. D.

    2016-08-01

    We reexamine the invariance of two-photon transition matrix elements and corresponding two-photon Rabi frequencies under the "gauge" transformation from the length to the velocity gauge. It is shown that gauge invariance, in the most general sense, only holds at exact resonance, for both one-color as well as two-color absorption. The arguments leading to this conclusion are supported by analytic calculations which express the matrix elements in terms of hypergeometric functions, and ramified by a "master identity" which is fulfilled by off-diagonal matrix elements of the Schrödinger propagator under the transformation from the velocity to the length gauge. The study of the gauge dependence of atomic processes highlights subtle connections between the concept of asymptotic states, the gauge transformation of the wave function, and infinitesimal damping parameters for perturbations and interaction Hamiltonians that switch off the terms in the infinite past and future [of the form exp(-ɛ |t |)] . We include a pertinent discussion.

  5. A spirobifluorene-based two-photon fluorescence probe for mercury ions and its applications in living cells

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Haibo, E-mail: xiaohb@shnu.edu.cn; Zhang, Yanzhen; Zhang, Wu; Li, Shaozhi; Tan, Jingjing; Han, Zhongying

    2017-05-01

    A novel spirobifluorene derivative SPF-TMS, which containing dithioacetal groups and triphenylamine units, was synthesized. The probing behaviors toward various metal ions were investigated via UV/Vis absorption spectra as well as one-photon fluorescence changes. The results indicated that SPF-TMS exhibits high sensitivity and selectivity for mercury ions. The detection limit was at least 8.6 × 10{sup −8}M, which is excellent comparing with other optical sensors for Hg{sup 2+}. When measured by two-photon excited fluorescence technique in THF at 800 nm, the two-photon cross-section of SPF-TMS is 272 GM. Especially, upon reaction with mercury species, SPF-TMS yielded another two-photon dye SPF-DA. Both SPF-TMS and SPF-DA emit strong two-photon induced fluorescence and can be applied in cell imaging by two-photon microscopy. - Highlights: • We report a spirobifluorene-based molecule as two-photon fluorescent probe with large two-photon cross-section. • The molecule has exclusive selectivity and sensitivity for mercury species. • The molecule has large two-photon emission changes before and after addition of Hg{sup 2+}. • Both the probe and the mercury ion-promoted reaction product can be applied in cell imaging by two-photon microscopy.

  6. Coherent control of non-resonant two-photon transition in molecular system

    Institute of Scientific and Technical Information of China (English)

    Zhang Hui; Zhang Shi-An; Wang Zu-Geng; Sun Zhen-Rong

    2010-01-01

    In this paper,we study theoretically and experimentally the coherent control of non-resonant two-photon transition in a molecular system (Perylene dissolved in chloroform solution) by shaping the femtosecond pulses with simple phase patterns (cosinusoidal and π phase step-function shape).The control efficiency of the two-photon transition probability is correlated with both the laser field and the molecular absorption bandwidth.Our results demonstrate that,the two-photon transition probability in a molecular system can be reduced but not completely eliminated by manipulating the laser field,and the control efficiency is minimal when the molecular absorption bandwidth is larger than twice the laser spectral bandwidth.

  7. A Theranostic Agent Combining a Two-Photon-Absorbing Photosensitizer for Photodynamic Therapy and a Gadolinium(III) Complex for MRI Detection.

    Science.gov (United States)

    Schmitt, Julie; Heitz, Valérie; Sour, Angélique; Bolze, Frédéric; Kessler, Pascal; Flamigni, Lucia; Ventura, Barbara; Bonnet, Célia S; Tóth, Éva

    2016-02-18

    The convergent synthesis and characterization of a potential theranostic agent, [DPP-ZnP-GdDOTA](-), which combines a diketopyrrolopyrrole-porphyrin component DPP-ZnP as a two-photon photosensitizer for photodynamic therapy (PDT) with a gadolinium(III) DOTA complex as a magnetic resonance imaging probe, is presented. [DPP-ZnP-GdDOTA](-) has a remarkably high longitudinal water proton relaxivity (19.94 mm(-1)  s(-1) at 20 MHz and 25 °C) for a monohydrated molecular system of this size. The Nuclear Magnetic Relaxation Dispersion (NMRD) profile is characteristic of slow rotation, related to the extended and rigid aromatic units integrated in the molecule and to self-aggregation occurring in aqueous solution. The two-photon properties were examined and large two-photon absorption cross-sections around 1000 GM were determined between 910 and 940 nm in DCM with 1 % pyridine and in DMSO. Furthermore, the new conjugate was able to generate singlet oxygen, with quantum yield of 0.42 and 0.68 in DCM with 1 % pyridine and DMSO, respectively. Cellular studies were also performed. The [DPP-ZnP-GdDOTA](-) conjugate demonstrated low dark toxicity and was able to induce high one-photon and moderate two-photon phototoxicity on cancer cells.

  8. Two-photon interference : spatial aspects of two-photon entanglement, diffraction, and scattering

    NARCIS (Netherlands)

    Peeters, Wouter Herman

    2010-01-01

    This dissertation contains scientific research within the realm of quantum optics, which is a branch of physics. An experimental and theoretical study is made of two-photon interference phenomena in various optical systems. Spatially entangled photon pairs are produced via the nonlinear optical proc

  9. Two-photon imaging of stem cells

    Science.gov (United States)

    Uchugonova, A.; Gorjup, E.; Riemann, I.; Sauer, D.; König, K.

    2008-02-01

    A variety of human and animal stem cells (rat and human adult pancreatic stem cells, salivary gland stem cells, dental pulpa stem cells) have been investigated by femtosecond laser 5D two-photon microscopy. Autofluorescence and second harmonic generation have been imaged with submicron spatial resolution, 270 ps temporal resolution, and 10 nm spectral resolution. In particular, NADH and flavoprotein fluorescence was detected in stem cells. Major emission peaks at 460nm and 530nm with typical mean fluorescence lifetimes of 1.8 ns and 2.0 ns, respectively, were measured using time-correlated single photon counting and spectral imaging. Differentiated stem cells produced the extracellular matrix protein collagen which was detected by SHG signals at 435 nm.

  10. Two-photon imaging and analysis of neural network dynamics

    Science.gov (United States)

    Lütcke, Henry; Helmchen, Fritjof

    2011-08-01

    The glow of a starry night sky, the smell of a freshly brewed cup of coffee or the sound of ocean waves breaking on the beach are representations of the physical world that have been created by the dynamic interactions of thousands of neurons in our brains. How the brain mediates perceptions, creates thoughts, stores memories and initiates actions remains one of the most profound puzzles in biology, if not all of science. A key to a mechanistic understanding of how the nervous system works is the ability to measure and analyze the dynamics of neuronal networks in the living organism in the context of sensory stimulation and behavior. Dynamic brain properties have been fairly well characterized on the microscopic level of individual neurons and on the macroscopic level of whole brain areas largely with the help of various electrophysiological techniques. However, our understanding of the mesoscopic level comprising local populations of hundreds to thousands of neurons (so-called 'microcircuits') remains comparably poor. Predominantly, this has been due to the technical difficulties involved in recording from large networks of neurons with single-cell spatial resolution and near-millisecond temporal resolution in the brain of living animals. In recent years, two-photon microscopy has emerged as a technique which meets many of these requirements and thus has become the method of choice for the interrogation of local neural circuits. Here, we review the state-of-research in the field of two-photon imaging of neuronal populations, covering the topics of microscope technology, suitable fluorescent indicator dyes, staining techniques, and in particular analysis techniques for extracting relevant information from the fluorescence data. We expect that functional analysis of neural networks using two-photon imaging will help to decipher fundamental operational principles of neural microcircuits.

  11. Two-photon imaging and analysis of neural network dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Luetcke, Henry; Helmchen, Fritjof [Brain Research Institute, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich (Switzerland)

    2011-08-15

    The glow of a starry night sky, the smell of a freshly brewed cup of coffee or the sound of ocean waves breaking on the beach are representations of the physical world that have been created by the dynamic interactions of thousands of neurons in our brains. How the brain mediates perceptions, creates thoughts, stores memories and initiates actions remains one of the most profound puzzles in biology, if not all of science. A key to a mechanistic understanding of how the nervous system works is the ability to measure and analyze the dynamics of neuronal networks in the living organism in the context of sensory stimulation and behavior. Dynamic brain properties have been fairly well characterized on the microscopic level of individual neurons and on the macroscopic level of whole brain areas largely with the help of various electrophysiological techniques. However, our understanding of the mesoscopic level comprising local populations of hundreds to thousands of neurons (so-called 'microcircuits') remains comparably poor. Predominantly, this has been due to the technical difficulties involved in recording from large networks of neurons with single-cell spatial resolution and near-millisecond temporal resolution in the brain of living animals. In recent years, two-photon microscopy has emerged as a technique which meets many of these requirements and thus has become the method of choice for the interrogation of local neural circuits. Here, we review the state-of-research in the field of two-photon imaging of neuronal populations, covering the topics of microscope technology, suitable fluorescent indicator dyes, staining techniques, and in particular analysis techniques for extracting relevant information from the fluorescence data. We expect that functional analysis of neural networks using two-photon imaging will help to decipher fundamental operational principles of neural microcircuits.

  12. Experimental method for the determination of two-photon cross sections using four-wave mixing

    Science.gov (United States)

    Burris, J.; Mcilrath, T. J.

    1985-01-01

    The two-photon absorption cross section for the R22 + S12(J double prime = 9 1/2) transition in nitric oxide's gamma band has been determined. The value is in good agreement with previous measurements on several other NO transitions. The technique described here can be used to obtain accurate cross sections for other diatomic molecules.

  13. Experimental method for the determination of two-photon cross sections using four-wave mixing

    Science.gov (United States)

    Burris, J.; Mcilrath, T. J.

    1985-01-01

    The two-photon absorption cross section for the R22 + S12(J double prime = 9 1/2) transition in nitric oxide's gamma band has been determined. The value is in good agreement with previous measurements on several other NO transitions. The technique described here can be used to obtain accurate cross sections for other diatomic molecules.

  14. Two-photon excited highly polarized and directional upconversion emission from slab organic crystals

    NARCIS (Netherlands)

    Fang, Hong-Hua; Chen, Qi-Dai; Yang, Jie; Xia, Hong; Ma, Yu-Guang; Wang, Hai-Yu; Sun, Hong-Bo; Fang, Honghua

    2010-01-01

    Effective upconversion emission from an organic crystal of cyano-substituted oligo (p-phenylenevinylene) (CNDPASDB) based on two-photon absorption is presented. Frequency upconverted cavityless lasing, or amplified spontaneous emission, from the crystal pumped by a femtosecond laser of 800 nm was ob

  15. Two-photon Interference with Non-identical Photons

    CERN Document Server

    Liu, Jianbin; Zheng, Huaibin; Chen, Hui; Li, Fu-Li; Xu, Zhuo

    2014-01-01

    The indistinguishability of non-identical photons is dependent on detection system in quantum physics. If two photons with different wavelengths are indistinguishable for a detection system, there can be two-photon interference when these two photons are incident to two input ports of a Hong-Ou-Mandel interferometer, respectively. The reason why two-photon interference phenomena are different for classical and nonclassical light is not due to interference, but due to the properties of light and detection system. These conclusions are helpful to understand the physics and applications of two-photon interference.

  16. Second harmonic generation and two-photon luminescence upconversion in glasses doped with ZnSe nanocrystalline quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Thantu, Napoleon [Idaho National Engineering and Environmental Laboratory, 2525 Fremont Avenue, Idaho Falls, ID 83415 (United States)]. E-mail: Napoleon.Thantu@ngc.com

    2005-01-01

    We report two-photon excited emission in borosilicate glasses doped with ZnSe nanocrystalline quantum dots. The emission, predominantly near the two-photon energy and detected in the direction of the excitation beam, is in the visible, and the fundamental excitation is the near-infrared output of a tunable femtosecond laser. Depending on the two-photon energy, time- and frequency-resolved measurements at room temperature reveal that the emission largely consists of second harmonic generation (SHG) and two-photon luminescence upconversion, and a much smaller luminescence from redshifted, low-lying trap states and other trap levels residing near the semiconductor band edge. We discuss the SHG origin in terms of bulk-like and surface contributions from the nanocrystals and the two-photon resonant enhancement near the excitonic absorption.

  17. Two-Photon or Higher-Order Absorbing Optical Materials for Generation of Reactive Species

    Science.gov (United States)

    Cumpston, Brian (Inventor); Lipson, Matthew (Inventor); Marder, Seth R. (Inventor); Perry, Joseph W. (Inventor)

    2013-01-01

    Disclosed are highly efficient multiphoton absorbing compounds and methods of their use. The compounds generally include a bridge of pi-conjugated bonds connecting electron donating groups or electron accepting groups. The bridge may be substituted with a variety of substituents as well. Solubility, lipophilicity, absorption maxima and other characteristics of the compounds may be tailored by changing the electron donating groups or electron accepting groups, the substituents attached to or the length of the pi-conjugated bridge. Numerous photophysical and photochemical methods are enabled by converting these compounds to electronically excited states upon simultaneous absorption of at least two photons of radiation. The compounds have large two-photon or higher-order absorptivities such that upon absorption, one or more Lewis acidic species, Lewis basic species, radical species or ionic species are formed.

  18. Fluorenyl porphyrins for combined two-photon excited fluorescence and photosensitization

    Science.gov (United States)

    Mongin, Olivier; Hugues, Vincent; Blanchard-Desce, Mireille; Merhi, Areej; Drouet, Samuel; Yao, Dandan; Paul-Roth, Christine

    2015-04-01

    The two-photon absorption (2PA), the luminescence and the photosensitization properties of porphyrin-cored fluorenyl dendrimers and meso-substituted fluorenylporphyrin monomer, dimer and trimer are described. In comparison with model tetraphenylporphyrin, these compounds combine enhanced (non-resonant) 2PA cross-sections in the near infrared and enhanced fluorescence quantum yields, together with maintained singlet oxygen generation quantum yields. 'Semi-disconnection' between fluorenyl groups and porphyrins (i.e. direct meso substitution) proved to be more efficient than non-conjugated systems (based on efficient FRET between fluorenyl antennae and porphyrins). These results are of interest for combined two-photon imaging and photodynamic therapy.

  19. Free electron laser induced two-photon photoconductivity in Hg1-xCdxTe

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Beijing free electron laser (BFEL) has been employed for the first time to study the nonlinear photoconductivity characteristics of the typical infrared photoelectronic material Hg1-xCdxTe. Taking advantage of the high photon flux density of BFEL, we have investigated the photoconductivity characteristics in Hg1-xCdxTe induced by two-photon absorption by means of the photoconductivity technique, observed the photoconductivity signals saturation, and studied the two-photon photoconductivity characteristics on different bias voltages across the sample.

  20. Solvent effects on optical properties of a newly synthesized two-photon polymerization initiator: BPYPA

    Institute of Scientific and Technical Information of China (English)

    Guo Ya-Hui; Sun Yuan-Hong; Tao Li-Min; Zhao Ke; Wang Chuan-Kui

    2005-01-01

    Time-dependent hybrid density functional theory in combination with polarized continuum model is applied to study the solvent effects on the geometrical and electronic structures as well as one- and two-photon absorption processes,of a newly synthesized asymmetrical charge-transfer organic molecule bis-(4-bromo-phenyl)-[4-(2-pyridin-4-yl-vinyl)phenyl]-amine (BPYPA). There exist two charge-transfer states for the compound in visible region. The two-photon absorption cross section calculated by a three-state model and solvatochromic shift of the charge-transfer states are found to be solvent-dependent, where a nonmonotonic behaviour with respect to the polarity of the solvents is observed. The numerical results show that the organic molecule exhibits a rather large two-photon absorption cross section as compared with the compound 4-trans-[p-(N, N-Di-n-butylamino)-p-stilbenyl vinyl] pyridine (DBASVP) reported previously, and is predicted to be a good two-photon polymerization initiator. The hydrogen-bond effect is analysed. The computational results are in good agreement with the measurements.

  1. Highly Efficient and Excitation Tunable Two-Photon Luminescence Platform For Targeted Multi-Color MDRB Imaging Using Graphene Oxide

    Science.gov (United States)

    Pramanik, Avijit; Fan, Zhen; Chavva, Suhash Reddy; Sinha, Sudarson Sekhar; Ray, Paresh Chandra

    2014-08-01

    Multiple drug-resistance bacteria (MDRB) infection is one of the top three threats to human health according to the World Health Organization (WHO). Due to the large penetration depth and reduced photodamage, two-photon imaging is an highly promising technique for clinical MDRB diagnostics. Since most commercially available water-soluble organic dyes have low two-photon absorption cross-section and rapid photobleaching tendency, their applications in two-photon imaging is highly limited. Driven by the need, in this article we report extremely high two-photon absorption from aptamer conjugated graphene oxide (σ2PA = 50800 GM) which can be used for highly efficient two-photon fluorescent probe for MDRB imaging. Reported experimental data show that two-photon photoluminescence imaging color, as well as luminescence peak position can be tuned from deep blue to red, just by varying the excitation wavelength without changing its chemical composition and size. We have demonstrated that graphene oxide (GO) based two-photon fluorescence probe is capable of imaging of multiple antibiotics resistance MRSA in the first and second biological transparency windows using 760-1120 nm wavelength range.

  2. Two-photon conductivity in semiconductors: a new tool for the study of the quantum properties of light

    Science.gov (United States)

    Rosencher, E.; Boitier, F.; Godard, A.; Fabre, C.

    2012-01-01

    Two-photon absorption in GaAs occurs once two photon impinge on the semiconductor surface within the virtual state lifetime, i.e. few fs. Two photon conductivity (TPC) in GaAs is thus particulary well fitted to measure photon coincidence rates in the femtosecond range. Using this new TPC technique we have evidenced various original quantum properties of light, such as photon bunching in thermal light and extrabunching of twin beams. This technique opens new avenues in quantum optics, for quantum cryptography, ghost imaging or non linear optics.

  3. Enhancement of a Two-Photon-Induced Reaction in Solution Using Light-Harvesting Gold Nanodimer Structures.

    Science.gov (United States)

    Wu, Botao; Ueno, Kosei; Yokota, Yukie; Sun, Kai; Zeng, Heping; Misawa, Hiroaki

    2012-06-07

    We performed a quantitative analysis of plasmon-assisted two-photon photochromic reactions on light-harvesting gold nanodimer structures. Our strategy for the quantitative analysis of two-photon-induced photochemical reactions on gold nanostructures is using not only a confined photochemical reaction chamber but also a solution system. The strong intensification of near-field light at the nanogap positions on gold nanodimer pairs promoted two-photon absorption by a closed-form diarylethene derivative, resulting in highly efficient photochromic conversion to the open-form structure.

  4. Stationary States in Saturated Two-Photon Processes and Generation of Phase-Averaged Mixtures of Even and Odd Quantum States

    CERN Document Server

    Dodonov, V V

    1998-01-01

    We consider a relaxation of a single mode of the quantized field in a presence of one- and two-photon absorption and emission processes. Exact stationary solutions of the master equation for the diagonal elements of the density matrix in the Fock basis are found in the case of completely saturated two-photon emission. If two-photon processes dominate over single-photon ones, the stationary state is a mixture of phase averaged even and odd coherent states.

  5. Anomalous two-photon spectral features in warm rubidium vapor

    Science.gov (United States)

    Perrella, C.; Light, P. S.; Milburn, T. J.; Kielpinski, D.; Stace, T. M.; Luiten, A. N.

    2016-09-01

    We report observation of anomalous fluorescence spectral features in the environs of a two-photon transition in a rubidium vapor when excited with two different wavelength lasers that are both counterpropagating through the vapor. These features are characterized by an unusual trade-off between the detunings of the driving fields. Three different hypothetical processes are presented to explain the observed spectra: a simultaneous three-atom and four-photon collision, a four-photon excitation involving a light field produced via amplified spontaneous emission, and population pumping perturbing the expected steady-state spectra. Numerical modeling of each hypothetical process is presented, supporting the population pumping process as the most plausible mechanism.

  6. Terahertz-visible two-photon rotational spectroscopy of cold OD-

    CERN Document Server

    Lee, Seunghyun; Lakhmanskaya, Olga; Spieler, Steffen; Endres, Eric S; Geistlinger, Katharina; Kumar, Sunil S; Wester, Roland

    2016-01-01

    We present a method to measure rotational transitions of molecular anions in the terahertz domain by sequential two-photon absorption. Ion excitation by bound-bound terahertz absorption is probed by absorption in the visible on a bound-free transition. The visible frequency is tuned to a state-selective photodetachment transition of the excited anions. This provides a terahertz action spectrum for just few hundred molecular ions. To demonstrate this we measure the two lowest rotational transitions, J=1<-0 and J =2<-1 of OD- anions in a cryogenic 22-pole trap. We obtain rotational transition frequencies of 598596.08(19) MHz for J=1<-0 and 1196791.57(27) MHz for J=2<-1 of OD-, in good agreement with their only previous measurement. This two-photon scheme opens up terahertz rovibrational spectroscopy for a range of molecular anions, in particular for polyatomic and cluster anions.

  7. Efficient two-photon sensitized luminescence of europium (Ⅲ) complex based on hypersensitive transitions

    Institute of Scientific and Technical Information of China (English)

    Meng Shi; Hua Li; Mei Pan; Fufang Su; Lili Ma; Peigao Han; Hezhou Wang

    2011-01-01

    Red frequency-upconversion fluorescence emission is observed in europium(Ⅲ) complex with encapsulating polybenzimidazole tripodal ligands, pumped with 930- and 1070-nm picosecond laser pulses. The luminescence of transition 5D0 →7F2 (612 nm) is induced by two-photon absorption of hypersensitive transitions 7F0 →5D2 (465 nm) and 7F1 →5D1 (535 nm). Analysis results suggest that the two-photon excitation strength of these hypersensitive transitions is increased dramatically owing to the C3 symmetry of the coordination field.%@@ Red frequency-upconversion fluorescence emission is observed in europium(Ⅲ) complex with encapsulating polybenzimidazole tripodal ligands, pumped with 930- and 1070-nm picosecond laser pulses.The luminescence of transition 5D0 →7F2 (612 nm) is induced by two-photon absorption of hypersensitive transitions 7F0 →5D2 (465 nm) and 7F1 →5D1 (535 nm).Analysis results suggest that the two-photon excitation strength of these hypersensitive transitions is increased dramatically owing to the Ca symmetry of the coordination field.

  8. [Intensity loss of two-photon excitation fluorescence microscopy images of mouse oocyte chromosomes].

    Science.gov (United States)

    Zhao, Feng-Ying; Wu, Hong-Xin; Chen, Die-Yan; Ma, Wan-Yun

    2014-07-01

    As an optical microscope with high resolution, two-photon excitation (TPE) fluorescence microscope is widely used in noninvasive 3D optical imaging of biological samples. Compared with confocal laser scanning microscope, TPE fluorescence microscope provides a deeper detecting depth. In spite of that, the image quality of sample always declines as the detecting depth increases when a noninvasive 3D optical imaging of thicker samples is performed. Mouse oocytes with a large diameter, which play an important role in clinical and biological fields, have obvious absorption and scattering effects. In the present paper, we performed compensation for two-photon fluorescence images of mouse oocyte chromosomes. Using volume as a parameter, the attenuation degree of these chromosomes was also studied. The result of our data suggested that there exists a severe axial intensity loss in two-photon microscopic images of mouse oocytes due to the absorption and scattering effects. It is necessary to make compensation for these images of mouse oocyte chromosomes obtained from two-photon microscopic system. It will be specially needed in studying the quantitative three-dimensional information of mouse oocytes.

  9. Several Organic Salts with High Two-Photon Active

    Institute of Scientific and Technical Information of China (English)

    TIAN, Yu-Peng; JIANG, Min-Hua; WANG, He-Zhou; FANG, Qi

    2001-01-01

    Several organic salts with D-A molecular structure and different counterion have been prepared and experimentally investigated. The two-photon induced frequency-upconverted spectra and two-photon pumped lasing are measured for the organic salt solutions in various solvents. The results indicate that counterions have influence on their stability and lasing property.

  10. Characterization of hydrophobic nanoporous particle liquids for energy absorption

    Science.gov (United States)

    Hsu, Yi; Liu, Yingtao

    2016-04-01

    Recently, the development of hydrophobic nanoporous technologies has drawn increased attention, especially for the applications of energy absorption and impact protection. Although significant amount of research has been conducted to synthesis and characterize materials to protect structures from impact damage, the tradition methods focused on converting kinetic energy to other forms, such as heat and cell buckling. Due to their high energy absorption efficiency, hydrophobic nanoporous particle liquids (NPLs) are one of the most attractive impact mitigation materials. During impact, such particles directly trap liquid molecules inside the non-wetting surface of nanopores in the particles. The captured impact energy is simply stored temporarily and isolated from the original energy transmission path. In this paper we will investigate the energy absorption efficiency of combinations of silica nanoporous particles and with multiple liquids. Inorganic particles, such as nanoporous silica, are characterized using scanning electron microscopy. Small molecule promoters, such as methanol and ethanol, are introduced to the prepared NPLs. Their effects on the energy absorption efficiency are studied in this paper. NPLs are prepared by dispersing the studied materials in deionized water. Energy absorption efficiency of these liquids are experimentally characterized using an Instron mechanical testing frame and in-house develop stainless steel hydraulic cylinder system.

  11. Two-Photon Photodynamic Therapy by Water-Soluble Self-Assembled Conjugated Porphyrins

    Directory of Open Access Journals (Sweden)

    Kazuya Ogawa

    2013-01-01

    Full Text Available Studies on two-photon absorption (2PA photodynamic therapy (PDT by using three water-soluble porphyrin self-assemblies consisting of ethynylene-linked conjugated bis (imidazolylporphyrin are reviewed. 2PA cross-section values in water were obtained by an open aperture Z-scan measurement, and values were extremely large compared with those of monomeric porphyrins such as hematoporphyrin. These compounds were found to generate singlet oxygen efficiently upon one- as well as two-photon absorption as demonstrated by the time-resolved luminescence measurement at the characteristic band of singlet oxygen at 1270 nm and by using its scavenger. Photocytotoxicities for HeLa cancer cells were examined and found to be as high as those of hematoporphyrin, demonstrating that these compounds are potential candidates for 2PA-photodynamic therapy agents.

  12. Dependence of the two-photon photoluminescence yield of gold nanostructures on the laser pulse duration

    Science.gov (United States)

    Biagioni, P.; Celebrano, M.; Savoini, M.; Grancini, G.; Brida, D.; Mátéfi-Tempfli, S.; Mátéfi-Tempfli, M.; Duò, L.; Hecht, B.; Cerullo, G.; Finazzi, M.

    2009-07-01

    Two-photon photoluminescence (TPPL) from gold nanostructures is becoming one of the most relevant tools for plasmon-assisted biological imaging and photothermal therapy as well as for the investigation of plasmonic devices. Here we study the yield of TPPL as a function of the temporal width δ of the excitation laser pulses for a fixed average power. In the δ>1ps regime, the TPPL yield decreases as δ is increased, while for shorter pulse widths it becomes independent of δ and, consequently, of the laser-pulse peak power. This peculiar dynamics is understood and modeled by considering that two-photon absorption in Au is a two-step process governed by the lifetime of the metastable state populated by the first photon absorption.

  13. Two-photon polymerization of 3-D zirconium oxide hybrid scaffolds for long-term stem cell growth.

    Science.gov (United States)

    Skoog, Shelby A; Nguyen, Alexander K; Kumar, Girish; Zheng, Jiwen; Goering, Peter L; Koroleva, Anastasia; Chichkov, Boris N; Narayan, Roger J

    2014-06-01

    Two-photon polymerization is a technique that involves simultaneous absorption of two photons from a femtosecond laser for selective polymerization of a photosensitive material. In this study, two-photon polymerization was used for layer-by-layer fabrication of 3-D scaffolds composed of an inorganic-organic zirconium oxide hybrid material. Four types of scaffold microarchitectures were created, which exhibit layers of parallel line features at various orientations as well as pores between the line features. Long-term cell culture studies involving human bone marrow stromal cells were conducted using these 3-D scaffolds. Cellular adhesion and proliferation were demonstrated on all of the scaffold types; tissuelike structure was shown to span the pores. This study indicates that two-photon polymerization may be used to create microstructured scaffolds out of an inorganic-organic zirconium oxide hybrid material for use in 3-D tissue culture systems.

  14. In vivo two-photon calcium imaging in the visual system.

    Science.gov (United States)

    Ohki, Kenichi; Reid, R Clay

    2014-04-01

    Two-photon imaging of calcium-sensitive dyes in vivo has become a common tool used by neuroscientists, largely because of the development of bolus loading techniques, which can label every neuron in a local circuit with calcium-sensitive dye. Like multielectrode recordings, two-photon imaging paired with bolus loading provides a method for monitoring many neurons at once, but, in addition, it provides a means for determining the precise location of every neuron. Thus, it is an ideal method for studying the fine-scale functional architecture of the cortex and guiding the experimenter to individual neurons that can be targeted for further anatomical study. Two-photon calcium imaging enables study of the fine structure of functional maps in the visual cortex in cats and rodents. In mice, it can allow the characterization of specific cell types when paired with transgenic or retrograde labeling.

  15. Enhancement of two-photon photoluminescence and SERS for low-coverage gold films

    DEFF Research Database (Denmark)

    Novikov, Sergey M.; Beermann, Jonas; Frydendahl, Christian

    2016-01-01

    Electromagnetic field enhancement (FE) effects occurring in thin gold films 3-12-nm are investigated with two-photon photoluminescence (TPL) and Raman scanning optical microscopies. The samples are characterized using scanning electron microscopy images and linear optical spectroscopy. TPL images...

  16. Two-photon processes in highly charged ions

    Energy Technology Data Exchange (ETDEWEB)

    Jahrsetz, Thorsten

    2015-03-05

    Two-photon processes are atomic processes in which an atom interacts simultaneously with two photons. Such processes describe a wide range of phenomena, such as two-photon decay and elastic or inelastic scattering of photons. In recent years two-photon processes involving highly charged heavy ions have become an active area of research. Such studies do not only consider the total transition or scattering rates but also their angular and polarization dependence. To support such examinations in this thesis I present a theoretical framework to describe these properties in all two-photon processes with bound initial and final states and involving heavy H-like or He-like ions. I demonstrate how this framework can be used in some detailed studies of different two-photon processes. Specifically a detailed analysis of two-photon decay of H-like and He-like ions in strong external electromagnetic fields shows the importance of considering the effect of such fields for the physics of such systems. Furthermore I studied the elastic Rayleigh as well as inelastic Raman scattering by heavy H-like ions. I found a number of previously unobserved phenomena in the angular and polarization dependence of the scattering cross-sections that do not only allow to study interesting details of the electronic structure of the ion but might also be useful for the measurement of weak physical effects in such systems.

  17. Two-photon interference of temporally separated photons

    Science.gov (United States)

    Kim, Heonoh; Lee, Sang Min; Moon, Han Seb

    2016-10-01

    We present experimental demonstrations of two-photon interference involving temporally separated photons within two types of interferometers: a Mach-Zehnder interferometer and a polarization-based Michelson interferometer. The two-photon states are probabilistically prepared in a symmetrically superposed state within the two interferometer arms by introducing a large time delay between two input photons; this state is composed of two temporally separated photons, which are in two different or the same spatial modes. We then observe two-photon interference fringes involving both the Hong-Ou-Mandel interference effect and the interference of path-entangled two-photon states simultaneously in a single interferometric setup. The observed two-photon interference fringes provide simultaneous observation of the interferometric properties of the single-photon and two-photon wavepackets. The observations can also facilitate a more comprehensive understanding of the origins of the interference phenomena arising from spatially bunched/anti-bunched two-photon states comprised of two temporally separated photons within the interferometer arms.

  18. Two photon dissociation of benzene, phenylacetylene, and benzaldehyde at 243 nm: translational energy releases in the H atom channel

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Seung Keun; Kim, Hong Lae [Kangwon National Univ., Chuncheon (Korea, Republic of); Park, Chan Ryang [Kookmin Univ., Seoul (Korea, Republic of)

    2002-02-01

    Hydrogen atom production channels from photodissociation of benzene, phenylacetylene, and benzaldehyde at 243 nm have been investigated by detecting H atoms using two photon absorption at 243.2 nm and induced fluorescence at 121.6 nm. Translational energies of the H atoms were measured by Doppler broadened H atom spectra. By absorption of two photons at 243 nm, the H atoms are statistically produced from benzene and phenylacetylene whereas the H atoms from the aldehyde group in benzaldehyde are produced from different pathways. The possible dissociation mechanisms are discussed from the measured translational energy releases.

  19. Mitigating thermal mechanical damage potential during two-photon dermal imaging.

    Science.gov (United States)

    Masters, Barry R; So, Peter T C; Buehler, Christof; Barry, Nicholas; Sutin, Jason D; Mantulin, William W; Gratton, Enrico

    2004-01-01

    Two-photon excitation fluorescence microscopy allows in vivo high-resolution imaging of human skin structure and biochemistry with a penetration depth over 100 microm. The major damage mechanism during two-photon skin imaging is associated with the formation of cavitation at the epidermal-dermal junction, which results in thermal mechanical damage of the tissue. In this report, we verify that this damage mechanism is of thermal origin and is associated with one-photon absorption of infrared excitation light by melanin granules present in the epidermal-dermal junction. The thermal mechanical damage threshold for selected Caucasian skin specimens from a skin bank as a function of laser pulse energy and repetition rate has been determined. The experimentally established thermal mechanical damage threshold is consistent with a simple heat diffusion model for skin under femtosecond pulse laser illumination. Minimizing thermal mechanical damage is vital for the potential use of two-photon imaging in noninvasive optical biopsy of human skin in vivo. We describe a technique to mitigate specimen thermal mechanical damage based on the use of a laser pulse picker that reduces the laser repetition rate by selecting a fraction of pulses from a laser pulse train. Since the laser pulse picker decreases laser average power while maintaining laser pulse peak power, thermal mechanical damage can be minimized while two-photon fluorescence excitation efficiency is maximized.

  20. Phosphorescent probes for two-photon microscopy of oxygen (Conference Presentation)

    Science.gov (United States)

    Vinogradov, Sergei A.; Esipova, Tatiana V.

    2016-03-01

    The ability to quantify oxygen in vivo in 3D with high spatial and temporal resolution is much needed in many areas of biological research. Our laboratory has been developing the phosphorescence quenching technique for biological oximetry - an optical method that possesses intrinsic microscopic capability. In the past we have developed dendritically protected oxygen probes for quantitative imaging of oxygen in tissue. More recently we expanded our design on special two-photon enhanced phosphorescent probes. These molecules brought about first demonstrations of the two-photon phosphorescence lifetime microscopy (2PLM) of oxygen in vivo, providing new information for neouroscience and stem cell biology. However, current two-photon oxygen probes suffer from a number of limitations, such as sub-optimal brightness and high cost of synthesis, which dramatically reduce imaging performance and limit usability of the method. In this paper we discuss principles of 2PLM and address the interplay between the probe chemistry, photophysics and spatial and temporal imaging resolution. We then present a new approach to brightly phosphorescent chromophores with internally enhanced two-photon absorption cross-sections, which pave a way to a new generation of 2PLM probes.

  1. Quantum homodyne tomography of a two-photon Fock state

    CERN Document Server

    Ourjoumtsev, A; Grangier, P; Ourjoumtsev, Alexei; Tualle-Brouri, Rosa; Grangier, Philippe

    2006-01-01

    We present a continuous-variable experimental analysis of a two-photon Fock state of free-propagating light. This state is obtained from a pulsed non-degenerate parametric amplifier, which produces two intensity-correlated twin beams. Counting two photons in one beam projects the other beam in the desired two-photon Fock state, which is analyzed by using a pulsed homodyne detection. The Wigner function of the measured state is clearly negative. We developed a detailed analytic model which allows a fast and efficient analysis of the experimental results.

  2. Quantum homodyne tomography of a two-photon Fock state.

    Science.gov (United States)

    Ourjoumtsev, Alexei; Tualle-Brouri, Rosa; Grangier, Philippe

    2006-06-02

    We present a continuous-variable experimental analysis of a two-photon Fock state of free-propagating light. This state is obtained from a pulsed nondegenerate parametric amplifier, which produces two intensity-correlated twin beams. Counting two photons in one beam projects the other beam in the desired two-photon Fock state, which is analyzed by using a pulsed homodyne detection. The Wigner function of the measured state is clearly negative. We developed a detailed analytic model which allows a fast and efficient analysis of the experimental results.

  3. Scattering of two photons from two distant qubits: exact solution

    Energy Technology Data Exchange (ETDEWEB)

    Laakso, Matti; Pletyukhov, Mikhail [Institute for Theory of Statistical Physics, RWTH Aachen, 52056 Aachen (Germany)

    2015-07-01

    We consider the inelastic scattering of two photons from two qubits separated by an arbitrary distance and coupled to a one-dimensional transmission line. We present an exact, analytical solution to the problem, and use it to explore a particular configuration of qubits which is transparent to single-photon scattering, thus highlighting non-Markovian effects of inelastic two-photon scattering: Strong two-photon interference and momentum dependent photon (anti)bunching. This latter effect can be seen as an inelastic generalization of the Hong-Ou-Mandel effect.

  4. Targeted two-photon PDT photo-sensitizers for the treatment of subcutaneous tumors

    Science.gov (United States)

    Spangler, C. W.; Rebane, A.; Starkey, J.; Drobizhev, M.

    2009-06-01

    New porphyrin-based photo-sensitizers have been designed, synthesized and characterized that exhibit greatly enhanced intrinsic two-photon absorption. These new photo-sensitizers have been incorporated into triad formulations that also incorporate Near-infrared (NIR) imaging agents, and small-molecule targeting agents that direct the triads to cancerous tumors' over-expressed receptor sites. PDT can be initiated deep into the tissue transparency window at 780-800 nm utilizing a regeneratively amplified Ti:sapphire laser using 100-150 fs pulses of 600-800 mW. Human tumor xenografts of human breast cancer (MDA-MB-231) and both small SCLC (NCI-H69) and NSCLC (A-459) have been successfully treated using octreotate targeting of over-expressed SST2 receptors. In particular, the lung cancer xenografts can be successfully treated by irradiating from the side of the mouse opposite the implanted tumor, thereby passing through ca. 2 cm of mouse skin, tissue and organs with no discernible damage to healthy tissue while causing regression in the tumors. These results suggest a new PDT paradigm for the noninvasive treatment of subcutaneous tumors, including the possibility that the targeting moiety could be matched to individual patient genetic profiles (patient-specific therapeutics).

  5. NLO Electroweak Corrections to Higgs Decay to Two Photons

    OpenAIRE

    Actis, Stefano

    2009-01-01

    The recent calculation of the next-to-leading order electroweak corrections to the decay of the Standard Model Higgs boson to two photons in the framework of the complex-mass scheme is briefly summarized.

  6. Standard Model Higgs decay for two Photons in CMS

    CERN Multimedia

    Daniel Denegri

    2000-01-01

    Simulated two-photon mass distribution for SM Higgs and expected background in the CMS PbW04 crystal calorimeter for an integrated luminosity of 10 . 5 pb-1, with detailed simulation of calorimeter response.

  7. Pulse-shaping based two-photon FRET stoichiometry.

    Science.gov (United States)

    Flynn, Daniel C; Bhagwat, Amar R; Brenner, Meredith H; Núñez, Marcos F; Mork, Briana E; Cai, Dawen; Swanson, Joel A; Ogilvie, Jennifer P

    2015-02-09

    Förster Resonance Energy Transfer (FRET) based measurements that calculate the stoichiometry of intermolecular interactions in living cells have recently been demonstrated, where the technique utilizes selective one-photon excitation of donor and acceptor fluorophores to isolate the pure FRET signal. Here, we present work towards extending this FRET stoichiometry method to employ two-photon excitation using a pulse-shaping methodology. In pulse-shaping, frequency-dependent phases are applied to a broadband femtosecond laser pulse to tailor the two-photon excitation conditions to preferentially excite donor and acceptor fluorophores. We have also generalized the existing stoichiometry theory to account for additional cross-talk terms that are non-vanishing under two-photon excitation conditions. Using the generalized theory we demonstrate two-photon FRET stoichiometry in live COS-7 cells expressing fluorescent proteins mAmetrine as the donor and tdTomato as the acceptor.

  8. Mass distribution for the two-photon channel

    CERN Multimedia

    ATLAS, collaboration

    2012-01-01

    Mass distribution for the two-photon channel. The strongest evidence for this new particle comes from analysis of events containing two photons. The smooth dotted line traces the measured background from known processes. The solid line traces a statistical fit to the signal plus background. The new particle appears as the excess around 126.5 GeV. The full analysis concludes that the probability of such a peak is three chances in a million.

  9. Two-photon or higher-order absorbing optical materials and methods of use

    Science.gov (United States)

    Marder, Seth (Inventor); Perry, Joseph (Inventor)

    2012-01-01

    Compositions capable of simultaneous two-photon absorption and higher order absorptivities are provided. Compounds having a donor-pi-donor or acceptor-pi-acceptor structure are of particular interest, where the donor is an electron donating group, acceptor is an electron accepting group, and pi is a pi bridge linking the donor and/or acceptor groups. The pi bridge may additionally be substituted with electron donating or withdrawing groups to alter the absorptive wavelength of the structure. Also disclosed are methods of generating an excited state of such compounds through optical stimulation with light using simultaneous absorption of photons of energies individually insufficient to achieve an excited state of the compound, but capable of doing so upon simultaneous absorption of two or more such photons. Applications employing such methods are also provided, including controlled polymerization achieved through focusing of the light source(s) used.

  10. Selective two-photon collagen crosslinking in situ measured by Brillouin microscopy (Conference Presentation)

    Science.gov (United States)

    Kwok, Sheldon J. J.; Kuznetsov, Ivan A.; Kim, Moonseok; Choi, Myunghwan; Scarcelli, Giuliano; Yun, Seok-Hyun

    2017-02-01

    Two-photon polymerization and crosslinking are commonly used methods for microfabrication of three-dimensional structures with applications spanning from photonic microdevices, drug delivery systems, to cellular scaffolds. However, the use of two-photon processes for precise, internal modification of biological tissues has not yet been reported. One of the major challenges has been a lack of appropriate tools to monitor and characterize crosslinked regions nondestructively. Here, we demonstrate spatially selective two-photon collagen crosslinking (2P-CXL) in intact tissue for the first time. Using riboflavin photosensitizer and femtosecond laser irradiation, we crosslinked a small volume of tissue within animal corneas. Collagen fiber orientations and photobleaching were characterized by second harmonic generation and two-photon fluorescence imaging, respectively. Using confocal Brillouin microscopy, we measured local changes in longitudinal mechanical moduli and visualized the cross-linked pattern without perturbing surrounding non-irradiated regions. 2P-CXL-induced tissue stiffening was comparable to that achieved with conventional one-photon CXL. Our results demonstrate the ability to selectively stiffen biological tissue in situ at high spatial resolution, with broad implications in ophthalmology, laser surgery, and tissue engineering.

  11. Two-photon autofluorescence spectroscopy of oral mucosa tissue

    Science.gov (United States)

    Edward, Kert; Shilagard, Tuya; Qiu, Suimin; Vargas, Gracie

    2011-03-01

    The survival rate for individuals diagnosed with oral cancer is correlated with the stage of detection. Thus the development of novel techniques for the earliest possible detection of malignancies is of critical importance. Single photon (1P) autofluorescence spectroscopy has proven to be a powerful diagnostic tool in this regard, but 2P (two photon) spectroscopy remains essentially unexplored. In this investigation, a spectroscopic system was incorporated into a custom-built 2P laser scanning microscope. Oral cancer was induced in the buccal pouch of Syrian Golden hamsters by tri-weekly topical application of 9,10-dimethyl-1,2-benzanthracene (DMBA).Three separated sites where investigated in each hamster at four excitation wavelengths from 780 nm to 890 nm. A Total of 8 hamsters were investigated (4 normal and 4 DMBA treated). All investigated sites were imaged via 2p imaging, marked for biopsy, processed for histology and H&E staining, and graded by a pathologist. The in vivo emission spectrum for normal, mild/high grade dysplasia and squamous cell carcinoma is presented. It is shown that the hamsters with various stages of dysplasia are characterized by spectral differences as a function of depth and excitation wavelength, compared to normal hamsters.

  12. Voltage-sensitive rhodol with enhanced two-photon brightness.

    Science.gov (United States)

    Kulkarni, Rishikesh U; Kramer, Daniel J; Pourmandi, Narges; Karbasi, Kaveh; Bateup, Helen S; Miller, Evan W

    2017-03-14

    We have designed, synthesized, and applied a rhodol-based chromophore to a molecular wire-based platform for voltage sensing to achieve fast, sensitive, and bright voltage sensing using two-photon (2P) illumination. Rhodol VoltageFluor-5 (RVF5) is a voltage-sensitive dye with improved 2P cross-section for use in thick tissue or brain samples. RVF5 features a dichlororhodol core with pyrrolidyl substitution at the nitrogen center. In mammalian cells under one-photon (1P) illumination, RVF5 demonstrates high voltage sensitivity (28% ΔF/F per 100 mV) and improved photostability relative to first-generation voltage sensors. This photostability enables multisite optical recordings from neurons lacking tuberous sclerosis complex 1, Tsc1, in a mouse model of genetic epilepsy. Using RVF5, we show that Tsc1 KO neurons exhibit increased activity relative to wild-type neurons and additionally show that the proportion of active neurons in the network increases with the loss of Tsc1. The high photostability and voltage sensitivity of RVF5 is recapitulated under 2P illumination. Finally, the ability to chemically tune the 2P absorption profile through the use of rhodol scaffolds affords the unique opportunity to image neuronal voltage changes in acutely prepared mouse brain slices using 2P illumination. Stimulation of the mouse hippocampus evoked spiking activity that was readily discerned with bath-applied RVF5, demonstrating the utility of RVF5 and molecular wire-based voltage sensors with 2P-optimized fluorophores for imaging voltage in intact brain tissue.

  13. Two-photon excitation photodynamic therapy with Photofrin

    Science.gov (United States)

    Karotki, Aliaksandr; Khurana, Mamta; Lepock, James R.; Wilson, Brian C.

    2005-09-01

    Photodynamic therapy (PDT) based on simultaneous two-photon (2-γ) excitation has a potential advantage of highly targeted treatment by means of nonlinear localized photosensitizer excitation. One of the possible applications of 2-γ PDT is a treatment of exodus age-related macular degeneration where highly targeted excitation of photosensitizer in neovasculature is vital for reducing collateral damage to healthy surrounding tissue. To investigate effect of 2-γ PDT Photofrin was used as an archetypal photosensitizer. First, 2-γ absorption properties of Photofrin in the 750 - 900 nm excitation wavelength range were investigated. It was shown that above 800 nm 2-γ interaction was dominant mode of excitation. The 2-γ cross section of Photofrin was rather small and varied between 5 and 10 GM (1 GM = 10-50 cm4s/photon) in this wavelength range. Next, endothelial cells treated with Photofrin were used to model initial effect of 2-γ PDT on neovasculature. Ultrashort laser pulses provided by mode-locked Ti:sapphire laser (pulse duration at the sample 300 fs, repetition rate 90 MHz, mean laser power 10 mW, excitation wavelength 850 nm) were used for the excitation of the photosensitizer. Before 2-γ excitation of the Photofrin cells formed a single continuous sheet at the bottom of the well. The tightly focused laser light was scanned repeatedly over the cell layer. After irradiation the cell layer of the control cells stayed intact while cells treated with photofrin became clearly disrupted. The light doses required were high (6300 Jcm(-2) for ~ 50% killing), but 2-γ cytotoxicity was unequivocally demonstrated.

  14. Nonlinear processes upon two-photon interband picosecond excitation of PbWO4 crystal

    Science.gov (United States)

    Lukanin, V. I.; Karasik, A. Ya

    2016-09-01

    A new experimental method is proposed to study the dynamics of nonlinear processes occurring upon two-photon interband picosecond excitation of a lead tungstate crystal and upon its excitation by cw probe radiation in a temporal range from several nanoseconds to several seconds. The method is applied to the case of crystal excitation by a sequence of 25 high-power picosecond pulses with a wavelength of 523.5 nm and 633-nm cw probe radiation. Measuring the probe beam transmittance during crystal excitation, one can investigate the influence of two-photon interband absorption and the thermal nonlinearity of the refractive index on the dynamics of nonlinear processes in a wide range of times (from several nanoseconds to several seconds). The time resolution of the measuring system makes it possible to distinguish fast and slow nonlinear processes of electronic or thermal nature, including the generation of a thermal lens and thermal diffusion. An alternative method is proposed to study the dynamics of induced absorption transformation and, therefore, the dynamics of the development of nonlinear rocesses upon degenerate two-photon excitation of the crystal in the absence of external probe radiation.

  15. Dynamical modeling of pulsed two-photon interference

    Science.gov (United States)

    Fischer, Kevin A.; Müller, Kai; Lagoudakis, Konstantinos G.; Vučković, Jelena

    2016-11-01

    Single-photon sources are at the heart of quantum-optical networks, with their uniquely quantum emission and phenomenon of two-photon interference allowing for the generation and transfer of nonclassical states. Although a few analytical methods have been briefly investigated for describing pulsed single-photon sources, these methods apply only to either perfectly ideal or at least extremely idealized sources. Here, we present the first complete picture of pulsed single-photon sources by elaborating how to numerically and fully characterize non-ideal single-photon sources operating in a pulsed regime. In order to achieve this result, we make the connection between quantum Monte-Carlo simulations, experimental characterizations, and an extended form of the quantum regression theorem. We elaborate on how an ideal pulsed single-photon source is connected to its photocount distribution and its measured degree of second- and first-order optical coherence. By doing so, we provide a description of the relationship between instantaneous source correlations and the typical experimental interferometers (Hanbury-Brown and Twiss, Hong-Ou-Mandel, and Mach-Zehnder) used to characterize such sources. Then, we use these techniques to explore several prototypical quantum systems and their non-ideal behaviors. As an example numerical result, we show that for the most popular single-photon source—a resonantly excited two-level system—its error probability is directly related to its excitation pulse length. We believe that the intuition gained from these representative systems and characters can be used to interpret future results with more complicated source Hamiltonians and behaviors. Finally, we have thoroughly documented our simulation methods with contributions to the Quantum Optics Toolbox in Python in order to make our work easily accessible to other scientists and engineers.

  16. Two-photon spectroscopy of trapped HD$^+$ ions in the Lamb-Dicke regime

    CERN Document Server

    Tran, Vu Quang; Douillet, Albane; Koelemeij, Jeroen C J; Hilico, Laurent

    2013-01-01

    We study the feasibility of nearly-degenerate two-photon rovibrational spectroscopy in ensembles of trapped, sympathetically cooled hydrogen molecular ions using a resonance-enhanced multiphoton dissociation (REMPD) scheme. Taking advantage of quasi-coincidences in the rovibrational spectrum, the excitation lasers are tuned close to an intermediate level to resonantly enhance two-photon absorption. Realistic simulations of the REMPD signal are obtained using a four-level model that takes into account saturation effects, ion trajectories, laser frequency noise and redistribution of population by blackbody radiation. We show that the use of counterpropagating laser beams enables optical excitation in an effective Lamb-Dicke regime. Sub-Doppler lines having widths in the 100 Hz range can be observed with good signal-to-noise ratio for an optimal choice of laser detunings. Our results indicate the feasibility of molecular spectroscopy at the $10^{-14}$ accuracy level for improved tests of molecular QED, a new det...

  17. Slow reflection and two-photon generation of microcavity exciton-polaritons

    CERN Document Server

    Steger, Mark; Snoke, David W; Pfeiffer, Loren; West, Ken

    2014-01-01

    We resonantly inject polaritons into a microcavity and track them in time and space as they feel a force due to the cavity gradient. This is an example of "slow reflection," as the polaritons, which can be viewed as renormalized photons, slow down to zero velocity and then move back in the opposite direction. These measurements accurately measure the lifetime of the polaritons in our samples, which is 180 $\\pm$ 10 ps, corresponding to a cavity leakage time of 135 ps and a cavity $Q$ of 320,000. Such long-lived polaritons propagate millimeters in these wedge-shaped microcavities. Additionally, we generate polaritons by two-photon excitation directly into the polariton states, allowing the possibility of modulation of the two-photon absorption by a polariton condensate.

  18. Diagnostics of MCF plasmas using Lyman-{alpha} fluorescence excited by one or two photons

    Energy Technology Data Exchange (ETDEWEB)

    Voslamber, D

    1998-11-01

    Laser-induced Lyman-{alpha} fluorescence of the hydrogen isotopes is investigated with regard to diagnostic applications in magnetically confined fusion plasmas. A formal analysis is presented for two excitation schemes: one-photon and Doppler-free two-photon excitation. The analysis includes estimates of the expected experimental errors arising from the photon noise and from the sensitivity of the observed fluorescence signals to variations of the plasma and laser parameters. Both excitation schemes are suitable primarily for application in the plasma edge, but even in the plasma bulk of large machines they can still be applied in combination with a diagnostic neutral beam. The two-photon excitation scheme is particularly attractive because it involves absorption spectra that are resolved within the Doppler width. This implies a large diagnostic potential and in particular offers a way to measure the deuterium-tritium fuel mix in fusion reactors. (author) 37 refs.

  19. Direct two-photon excitation of isomeric transition in thorium-229 nucleus

    CERN Document Server

    Romanenko, V I; Yatsenko, L P; Romanenko, A V; Litvinov, A N; Kazakov, G A

    2012-01-01

    A possibility of the two-photon excitation of an isomeric state in a nucleus of thorium-229 has been discussed. The fluorescence intensity of the excitation is demonstrated to be identical for the irradiation of nuclei with either monochromatic light or polychromatic radiation consisting of a sequence of short light pulses of the same intensity. The two-photon excitation of Th^{3+} ion in an electromagnetic trap with a focused laser beam with a wavelength of about 320 nm and power of 100 mW can lead to the absorption saturation, at which the fluorescence emission with the frequency of the transition in a nucleus is maximal. In crystals doped with Th^{4+} to a concentration of about 10^{18} cm^{-3} and irradiated with a laser radiation 10 W in power, the emission of several photons per second with a wavelength of about 160 nm becomes possible.

  20. Ag@Aggregation-induced emission dye core/shell nanostructures with enhanced one- and two-photon fluorescence

    Science.gov (United States)

    Wang, Cheng; Li, Yang; Xu, Qiujin; Luo, Liang

    2017-10-01

    Combining plasmonic nanostructures with two-photon fluorescence materials is a promising way to significantly enhance two-photon fluorescence. Ag@1,4-bis(2-cyano-2-phenylethenyl) benzene (BCPEB) core/shell nanostructures were fabricated by simply incubating the isolated Ag nanoparticles with BCPEB microrods in ethanol. BCPEB was chosen as the fluorescent organic molecule owing to the aggregation-induced-emission (AIE) nature which would reduce the emission loss as being practically applied in solid phase. By utilizing the match of the extinction spectrum of Ag nanoparticles and BCPEB's absorption band, the target Ag@BCPEB core/shell nanostructures showed an enhanced one-photon (12×) fluorescence, integrating with SERS signal as well. Moreover, the resultant second harmonic generation of Ag nanoparticles under two-photon excitation also well matched with the absorption band of BCPEB, and significant enhanced two-photon (17×) fluorescence was obtained. The confocal images of NIH-3T3 cells with these nanostructures under one- and two-photon excitation showed good contrast and brightness for bio-imaging.

  1. Two-photon imaging and spectroscopy of fresh human colon biopsies

    Science.gov (United States)

    Cicchi, R.; Sturiale, A.; Nesi, G.; Tonelli, F.; Pavone, F. S.

    2012-03-01

    Two-photon fluorescence (TPEF) microscopy is a powerful tool to image human tissues up to 200 microns depth without any exogenously added probe. TPEF can take advantage of the autofluorescence of molecules intrinsically contained in a biological tissue, as such NADH, elastin, collagen, and flavins. Two-photon microscopy has been already successfully used to image several types of tissues, including skin, muscles, tendons, bladder. Nevertheless, its usefulness in imaging colon tissue has not been deeply investigated yet. In this work we have used combined two-photon excited fluorescence (TPEF), second harmonic generation microscopy (SHG), fluorescence lifetime imaging microscopy (FLIM), and multispectral two-photon emission detection (MTPE) to investigate different kinds of human ex-vivo fresh biopsies of colon. Morphological and spectroscopic analyses allowed to characterize both healthy mucosa, polyp, and colon samples in a good agreement with common routine histology. Even if further analysis, as well as a more significant statistics on a large number of samples would be helpful to discriminate between low, mild, and high grade cancer, our method is a promising tool to be used as diagnostic confirmation of histological results, as well as a diagnostic tool in a multiphoton endoscope or colonoscope to be used in in-vivo imaging applications.

  2. Two-photon flow cytometer with laser scanning Bessel beams

    Science.gov (United States)

    Wang, Yongdong; Ding, Yu; Ray, Supriyo; Paez, Aurelio; Xiao, Chuan; Li, Chunqiang

    2016-03-01

    Flow cytometry is an important technique in biomedical discovery for cell counting, cell sorting and biomarker detection. In vivo flow cytometers, based on one-photon or two-photon excited fluorescence, have been developed for more than a decade. One drawback of laser beam scanning two-photon flow cytometer is that the two-photon excitation volume is fairly small due to the short Rayleigh range of a focused Gaussian beam. Hence, the sampling volume is much smaller than one-photon flow cytometry, which makes it challenging to count or detect rare circulating cells in vivo. Bessel beams have narrow intensity profiles with an effective spot size (FWHM) as small as several wavelengths, making them comparable to Gaussian beams. More significantly, the theoretical depth of field (propagation distance without diffraction) can be infinite, making it an ideal solution as a light source for scanning beam flow cytometry. The trade-off of using Bessel beams rather than a Gaussian beam is the fact that Bessel beams have small concentric side rings that contribute to background noise. Two-photon excitation can reduce this noise, as the excitation efficiency is proportional to intensity squared. Therefore, we developed a two-photon flow cytometer using scanned Bessel beams to form a light sheet that intersects the micro fluidic channel.

  3. Confocal and Two-Photon Microscopy: Foundations, Applications and Advances

    Science.gov (United States)

    Diaspro, Alberto

    2001-11-01

    Confocal and Two-Photon Microscopy Foundations, Applications, and Advances Edited by Alberto Diaspro Confocal and two-photon fluorescence microscopy has provided researchers with unique possibilities of three-dimensional imaging of biological cells and tissues and of other structures such as semiconductor integrated circuits. Confocal and Two-Photon Microscopy: Foundations, Applications, and Advances provides clear, comprehensive coverage of basic foundations, modern applications, and groundbreaking new research developments made in this important area of microscopy. Opening with a foreword by G. J. Brakenhoff, this reference gathers the work of an international group of renowned experts in chapters that are logically divided into balanced sections covering theory, techniques, applications, and advances, featuring: In-depth discussion of applications for biology, medicine, physics, engineering, and chemistry, including industrial applications Guidance on new and emerging imaging technology, developmental trends, and fluorescent molecules Uniform organization and review-style presentation of chapters, with an introduction, historical overview, methodology, practical tips, applications, future directions, chapter summary, and bibliographical references Companion FTP site with full-color photographs The significant experience of pioneers, leaders, and emerging scientists in the field of confocal and two-photon excitation microscopy Confocal and Two-Photon Microscopy: Foundations, Applications, and Advances is invaluable to researchers in the biological sciences, tissue and cellular engineering, biophysics, bioengineering, physics of matter, and medicine, who use these techniques or are involved in developing new commercial instruments.

  4. Free electron laser induced two-photon photoconductivity in Hg1-xCdxTe

    Institute of Scientific and Technical Information of China (English)

    YUAN; Xianzhang

    2001-01-01

    [1]Nathan, V., Guenther, A. H., Mitra, S. S., Review of multiphoton absortion in crystalline solids, J. Opt. Soc. Am. B, 1985, 2: 294—316.[2]Gibson, A. F., Hatch, C. B., Maggs, P. N. D. et al., Two-photon absorption in indium antimonide and germanium, J. Phys., C, 1976, 9: 3259—3275.[3]Miller, A., Johnston, A., Dempsey, J. et al., Two-photon absorption in InSb and Hg1-xCdxTe, J. Phys. C, 1929, 12: 4839—4849.[4]Burghoorn, J., Anderegg, V. F., Klaassen, T. O. et al., Free electron laser induced two-photon absorption in Hg1-xCdxTe, Appl. Phys. Lett., 1992, 61(19): 2320—2322.[5]Hui, Z. X., Yang, Z. H., Free Electron Laser (in Chinese), Beijing: National Defense Industry Press, 1995, 7—8.[6]Matter, J. C., Smirt, A. L., Scully, M. O., Saturable transmission in mercury cadmium telluride, Appl. Phys. Lett., 1976, 28(9): 507—509.[7]Nurmikko, A. V., Nonlinear absorption at 10.6 μm in Hg1-xCdxTe, Optics Communications, 1976, 18(4): 522—524.[8]Catalano, I. M., Cingolani, A., Minafra, A., Multiphoton transitions in ionic crystals, Phys. Rev. B, 1972, 5(4): 1629—1632.[9]Blakemore, J. S., Semiconductor Statistics, Oxford: Pergamon, 1962, 221—222.[10]Shen, S. C., Optical Property of Semiconductor (in Chinese), Beijing: Science Press, 1992, 392—394.

  5. Two-photon interference between disparate sources for quantum networking

    Science.gov (United States)

    McMillan, A. R.; Labonté, L.; Clark, A. S.; Bell, B.; Alibart, O.; Martin, A.; Wadsworth, W. J.; Tanzilli, S.; Rarity, J. G.

    2013-06-01

    Quantum networks involve entanglement sharing between multiple users. Ideally, any two users would be able to connect regardless of the type of photon source they employ, provided they fulfill the requirements for two-photon interference. From a theoretical perspective, photons coming from different origins can interfere with a perfect visibility, provided they are made indistinguishable in all degrees of freedom. Previous experimental demonstrations of such a scenario have been limited to photon wavelengths below 900 nm, unsuitable for long distance communication, and suffered from low interference visibility. We report two-photon interference using two disparate heralded single photon sources, which involve different nonlinear effects, operating in the telecom wavelength range. The measured visibility of the two-photon interference is 80 +/- 4%, which paves the way to hybrid universal quantum networks.

  6. Polarization Effects in Two-Photon Free-Free Transitions in Laser-Assisted Electron-Hydrogen Collisions

    CERN Document Server

    Cionga, Aurelia

    2013-01-01

    Two-photon free-free transitions in elastic laser-assisted electron-hydrogen collisions are studied in the domain of high scattering energies and low or moderate field intensities, in the third order of perturbation theory, taking into account all the involved Feynman diagrams. Based on the analytical expressions of the transition amplitudes, the differential cross sections for two-photon absorption/emission are computed at impact energy $E_i=100$ eV. The effect of field polarizations on the angular distribution and on the frequency dependence of the differential cross section is analyzed.

  7. Two-photon interference with non-identical photons

    Science.gov (United States)

    Liu, Jianbin; Zhou, Yu; Zheng, Huaibin; Chen, Hui; Li, Fu-li; Xu, Zhuo

    2015-11-01

    Two-photon interference with non-identical photons is studied based on the superposition principle in Feynman's path integral theory. The second-order temporal interference pattern is observed by superposing laser and pseudothermal light beams with different spectra. The reason why there is two-photon interference for photons of different spectra is that non-identical photons can be indistinguishable for the detection system when Heisenberg's uncertainty principle is taken into account. These studies are helpful to understand the second-order interference of light in the language of photons.

  8. Two-Photon Total Annihilation of Molecular Positronium

    CERN Document Server

    Pérez-Ríos, Jesús; Greene, Chris H

    2014-01-01

    The rate for complete two-photon annihilation of molecular positronium Ps$_{2}$ is reported. This decay channel involves a four-body collision among the fermions forming Ps$_{2}$, and two photons of 1.022 MeV, each, as the final state. The quantum electrodynamics result for the rate of this process is found to be $\\Gamma_{Ps_{2} \\rightarrow \\gamma\\gamma}$ = 9.0 $\\times 10^{-12}$ s$^{-1}$. This decay channel completes the most comprehensive decay chart for Ps$_{2}$ up to date.

  9. Two-photon Compton process in pulsed intense laser fields

    CERN Document Server

    Seipt, D

    2012-01-01

    Based on strong-field QED in the Furry picture we use the Dirac-Volkov propagator to derive a compact expression for the differential emission probability of the two-photon Compton process in a pulsed intense laser field. The relation of real and virtual intermediate states is discussed, and the natural regularization of the on-shell contributions due to the finite laser pulse is highlighted. The inclusive two-photon spectrum is two orders of magnitude stronger than expected from a perturbative estimate.

  10. Precision two-photon spectroscopy of alkali elements

    Indian Academy of Sciences (India)

    P V Kiran Kumar; M V Suryanarayana

    2014-08-01

    In this paper, we have briefly reviewed the work on two-photon spectroscopy of alkali elements and its applications. The technique of Doppler-free two-photon spectroscopy is briefly summarized. A review of various techniques adopted for measuring absolute frequencies of the atomic transitions and precision measurements of isotope shifts and hyperfine structures (HFS) is presented. Some of the recent works on precision measurements of HFS constants of 6 ${}^2S_{1/2}$ level of ${}^{39}$K and ${}^{41}$K, 9 ${}^2S_{1/2}$ level and 7 ${}^2D_{3/2}$ level of 133Cs are also discussed.

  11. Distribution of quantum information between an atom and two photons

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Bernhard

    2008-11-03

    The construction of networks consisting of optically interconnected processing units is a promising way to scale up quantum information processing systems. To store quantum information, single trapped atoms are among the most proven candidates. By placing them in high finesse optical resonators, a bidirectional information exchange between the atoms and photons becomes possible with, in principle, unit efficiency. Such an interface between stationary and ying qubits constitutes a possible node of a future quantum network. The results presented in this thesis demonstrate the prospects of a quantum interface consisting of a single atom trapped within the mode of a high-finesse optical cavity. In a two-step process, we distribute entanglement between the stored atom and two subsequently emitted single photons. The long atom trapping times achieved in the system together with the high photon collection efficiency of the cavity make the applied protocol in principle deterministic, allowing for the creation of an entangled state at the push of a button. Running the protocol on this quasi-stationary quantum interface, the internal state of the atom is entangled with the polarization state of a single emitted photon. The entanglement is generated by driving a vacuum-stimulated Raman adiabatic passage between states of the coupled atom-cavity system. In a second process, the atomic part of the entangled state is mapped onto a second emitted photon using a similar technique and resulting in a polarization-entangled two-photon state. To verify and characterize the photon-photon entanglement, we measured a violation of a Bell inequality and performed a full quantum state tomography. The results prove the prior atom-photon entanglement and demonstrate a quantum information transfer between the atom and the two emitted photons. This reflects the advantages of a high-finesse cavity as a quantum interface in future quantum networks. (orig.)

  12. In vivo reactive neural plasticity investigation by means of correlative two photon: electron microscopy

    Science.gov (United States)

    Allegra Mascaro, A. L.; Cesare, P.; Sacconi, L.; Grasselli, G.; Mandolesi, G.; Maco, B.; Knott, G.; Huang, L.; De Paola, V.; Strata, P.; Pavone, F. S.

    2013-02-01

    In the adult nervous system, different populations of neurons correspond to different regenerative behavior. Although previous works showed that olivocerebellar fibers are capable of axonal regeneration in a suitable environment as a response to injury1, we have hitherto no details about the real dynamics of fiber regeneration. We set up a model of singularly axotomized climbing fibers (CF) to investigate their reparative properties in the adult central nervous system (CNS) in vivo. Time lapse two-photon imaging has been combined to laser nanosurgery2, 3 to define a temporal pattern of the degenerative event and to follow the structural rearrangement after injury. To characterize the damage and to elucidate the possible formation of new synaptic contacts on the sprouted branches of the lesioned CF, we combined two-photon in vivo imaging with block face scanning electron microscopy (FIB-SEM). Here we describe the approach followed to characterize the reactive plasticity after injury.

  13. Stepwise Two-Photon-Gated Photochemical Reaction in Photochromic [2.2]Paracyclophane-Bridged Bis(imidazole dimer).

    Science.gov (United States)

    Mutoh, Katsuya; Nakagawa, Yuki; Sakamoto, Akira; Kobayashi, Yoichi; Abe, Jiro

    2015-05-06

    Stepwise two-photon processes not only have great potential for efficient light harvesting but also can provide valuable insights into novel photochemical sciences. Here we have designed a [2.2]paracyclophane-bridged bis(imidazole dimer), a molecule that is composed of two photochromic units and absorbs two photons in a stepwise manner. The absorption of the first photon leads to the formation of a short-lived biradical species (half-life = 88 ms at 298 K), while the absorption of the additional photon by the biradical species triggers a subsequent photochromic reaction to afford a long-lived quinoid species. The short-lived biradical species and the long-lived quinoid species display significantly different absorption spectra and rates of the thermal back-reaction. The stepwise two-photon excitation process in this photochromic system can be initiated even by incoherent continuous-wave light irradiation, indicating that this two-photon reaction is highly efficient. Our molecule based on the bridged bis(imidazole dimer) unit should be a good candidate for multiphoton-gated optical materials.

  14. Two-photon fluorescent sensor for K+ imaging in live cells (Conference Presentation)

    Science.gov (United States)

    Sui, Binglin; Yue, Xiling; Kim, Bosung; Belfield, Kevin D.

    2016-03-01

    It is difficult to overstate the physiological importance of potassium for life as its indispensable roles in a variety of biological processes are widely known. As a result, efficient methods for determining physiological levels of potassium are of paramount importance. Despite this, relatively few K+ fluorescence sensors have been reported, with only one being commercially available. A new two-photon excited fluorescent K+ sensor is reported. The sensor is comprised of three moieties, a highly selective K+ chelator as the K+ recognition unit, a boron-dipyrromethene (BODIPY) derivative modified with phenylethynyl groups as the fluorophore, and two polyethylene glycol chains to afford water solubility. The sensor displays very high selectivity (physiological metal cations. Upon binding K+, the sensor switches from non-fluorescent to highly fluorescent, emitting red to near-IR (NIR) fluorescence. The sensor exhibited a good two-photon absorption cross section, 500 GM at 940 nm. Moreover, it is not sensitive to pH in the physiological pH range. Time-dependent cell imaging studies via both one- and two-photon fluorescence microscopy demonstrate that the sensor is suitable for dynamic K+ sensing in living cells.

  15. Two-photon fluorescence and fluorescence imaging of two styryl heterocyclic dyes combined with DNA.

    Science.gov (United States)

    Gao, Chao; Liu, Shu-yao; Zhang, Xian; Liu, Ying-kai; Qiao, Cong-de; Liu, Zhao-e

    2016-03-01

    Two new styryl heterocyclic two-photon (TP) materials, 4-[4-(N-methyl)styrene]-imidazo [4,5-f][1,10] phenanthroline-benzene iodated salt (probe-1) and 4,4-[4-(N-methyl)styrene]-benzene iodated salt (probe-2) were successfully synthesized and studied as potential fluorescent probes of DNA detection. The linear and nonlinear photophysical properties of two compounds in different solvents were investigated. The absorption, one- and two-photon fluorescent spectra of the free dye and dye-DNA complex were also examined to evaluate their photophysical properties. The binding constants of dye-DNA were obtained according to Scatchard equation with good values. The results showed that two probes could be used as fluorescent DNA probes by two-photon excitation, and TP fluorescent properties of probe-1 are superior to that of probe-2. The fluorescent method date indicated that the mechanisms of dye-DNA complex interaction may be groove binding for probe-1 and electrostatic interaction for probe-2, respectively. The MTT assay experiments showed two probes are low toxicity. Moreover, the TP fluorescence imaging of DNA detection in living cells at 800 nm indicated that the ability to locate in cell nuclei of probe-1 is better than that of probe-2.

  16. Second harmonic imaging of plants tissues and cell implosion using two-photon process in ZnO nanoparticles.

    Science.gov (United States)

    Urban, Ben E; Neogi, Purnima B; Butler, Sween J; Fujita, Yasuhisa; Neogi, Arup

    2012-03-01

    The optical properties of colloidal ZnO nanoparticle (NP) solutions, with size ranging from several nm to around 200 nm, have been tailored to have high optical nonlinearity for bioimaging with no auto-fluorescence above 750 nm and minimal auto-fluorescence below 750 nm. The high second harmonic conversion efficiency enables selective tissue imaging and cell tracking using tunable near-infrared femtosecond laser source ranging from 750-980 nm. For laser energies exceeding the two-photon energy of the bandgap of ZnO (half of 3.34 eV), the SHG signal greatly decreases and the two-photon emission becomes the dominant signal. The heat generated due to two-photon absorption within the ZnO NPs enable selective cell or localized tissue destruction using excitation wavelength ranging from 710-750 nm. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Steady state anisotropy two-photon microscopy resolves multiple, spectrally similar fluorophores, enabling in vivo multilabel imaging.

    Science.gov (United States)

    Dubach, J Matthew; Vinegoni, Claudio; Weissleder, Ralph

    2014-08-01

    The use of spectrally distinguishable fluorescent dyes enables imaging of multiple targets. However, in two-photon microscopy, the number of fluorescent labels with distinct emission spectra that can be effectively excited and resolved is constrained by the confined tuning range of the excitation laser and the broad and overlapping nature of fluorophore two-photon absorption spectra. This limitation effectively reduces the number of available imaging channels. Here, we demonstrate that two-photon steady state anisotropy imaging (2PSSA) offers the capability to resolve otherwise unresolvable fluorescent tracers both in live cells and in mouse tumor models. This approach expands the number of biological targets that can be imaged simultaneously, increasing the total amount of information that can be obtained through imaging.

  18. Two-color two-photon excited fluorescence of indole: Determination of wavelength-dependent molecular parameters

    Energy Technology Data Exchange (ETDEWEB)

    Herbrich, Sebastian; Al-Hadhuri, Tawfik; Gericke, Karl-Heinz, E-mail: k.Gericke@tu-bs.de [Institut für Physikalische und Theoretische Chemie, TU Braunschweig, Hans-Sommer-Straße 10, 38106 Braunschweig (Germany); Shternin, Peter S., E-mail: pshternin@gmail.com; Vasyutinskii, Oleg S., E-mail: osv@pms.ioffe.ru [Ioffe Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); St. Petersburg Polytechnic University, Politekhnicheskaya 29, St. Petersburg 195251 (Russian Federation); Smolin, Andrey G. [Ioffe Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation)

    2015-01-14

    We present a detailed study of two-color two-photon excited fluorescence in indole dissolved in propylene glycol. Femtosecond excitation pulses at effective wavelengths from 268 to 293.33 nm were used to populate the two lowest indole excited states {sup 1}L{sub a} and {sup 1}L{sub b} and polarized fluorescence was then detected. All seven molecular parameters and the two-photon polarization ratio Ω containing information on two-photon absorption dynamics, molecular lifetime τ{sub f}, and rotation correlation time τ{sub rot} have been determined from experiment and analyzed as a function of the excitation wavelength. The analysis of the experimental data has shown that {sup 1}L{sub b}–{sup 1}L{sub a} inversion occurred under the conditions of our experiment. The two-photon absorption predominantly populated the {sup 1}L{sub a} state at all excitation wavelengths but in the 287–289 nm area which contained an absorption hump of the {sup 1}L{sub b} state 0-0 origin. The components of the two-photon excitation tensor S were analyzed giving important information on the principal tensor axes and absorption symmetry. The results obtained are in a good agreement with the results reported by other groups. The lifetime τ{sub f} and the rotation correlation time τ{sub rot} showed no explicit dependence on the effective excitation wavelength. Their calculated weighted average values were found to be τ{sub f} = 3.83 ± 0.14 ns and τ{sub rot} = 0.74 ± 0.06 ns.

  19. Internal conversions in Higgs decays to two photons

    OpenAIRE

    Firan, Ana; Stroynowski, Ryszard

    2007-01-01

    We evaluate the partial widths for internal conversions in the Higgs decays to two photons. For the Higgs masses of interest at LHC in the range of 100-150 GeV, the conversions to pairs of fermions represent significant fraction of Higgs decays.

  20. Direct Writing of Photonic Structures by Two-Photon Polymerization

    Directory of Open Access Journals (Sweden)

    Li Yan

    2013-11-01

    Full Text Available Single-mode dielectric-loaded surface plasmon-polariton nanowaveguides with strong mode confinement at excitation wavelength of 830 nm and high-Q polymer whispering gallery mode microcavities with surface roughness less than 12 nm have been directly written by two-photon polymerization, which pave the way to fabricate 3D plasmonic photonic structures by direct laser writing.

  1. Electron correlations and two-photon states in polycyclic aromatic hydrocarbon molecules: A peculiar role of geometry

    Energy Technology Data Exchange (ETDEWEB)

    Aryanpour, Karan [Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States); Shukla, Alok [Department of Physics, Indian Institute of Technology, Powai, Mumbai 400076 (India); Mazumdar, Sumit [Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States); College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States)

    2014-03-14

    We present numerical studies of one- and two-photon excited states ordering in a number of polycyclic aromatic hydrocarbon molecules: coronene, hexa-peri-hexabenzocoronene, and circumcoronene, all possessing D{sub 6h} point group symmetry versus ovalene with D{sub 2h} symmetry, within the Pariser-Parr-Pople model of interacting π-electrons. The calculated energies of the two-photon states as well as their relative two-photon absorption cross-sections within the interacting model are qualitatively different from single-particle descriptions. More remarkably, a peculiar role of molecular geometry is found. The consequence of electron correlations is far stronger for ovalene, where the lowest spin-singlet two-photon state is a quantum superposition of pairs of lowest spin triplet states, as in the linear polyenes. The same is not true for D{sub 6h} group hydrocarbons. Our work indicates significant covalent character, in valence bond language, of the ground state, the lowest spin triplet state and a few of the lowest two-photon states in D{sub 2h} ovalene but not in those with D{sub 6h} symmetry.

  2. Electron correlations and two-photon states in polycyclic aromatic hydrocarbon molecules: A peculiar role of geometry

    Science.gov (United States)

    Aryanpour, Karan; Shukla, Alok; Mazumdar, Sumit

    2014-03-01

    We present numerical studies of one- and two-photon excited states ordering in a number of polycyclic aromatic hydrocarbon molecules: coronene, hexa-peri-hexabenzocoronene, and circumcoronene, all possessing D6h point group symmetry versus ovalene with D2h symmetry, within the Pariser-Parr-Pople model of interacting π-electrons. The calculated energies of the two-photon states as well as their relative two-photon absorption cross-sections within the interacting model are qualitatively different from single-particle descriptions. More remarkably, a peculiar role of molecular geometry is found. The consequence of electron correlations is far stronger for ovalene, where the lowest spin-singlet two-photon state is a quantum superposition of pairs of lowest spin triplet states, as in the linear polyenes. The same is not true for D6h group hydrocarbons. Our work indicates significant covalent character, in valence bond language, of the ground state, the lowest spin triplet state and a few of the lowest two-photon states in D2h ovalene but not in those with D6h symmetry.

  3. Resonant transfer of one- and two-photon excitations in quantum dot-bacteriorhodopsin complexes

    Science.gov (United States)

    Krivenkov, V. A.; Samokhvalov, P. S.; Bilan, R. S.; Chistyakov, A. A.; Nabiev, I. R.

    2017-01-01

    Light-sensitive protein bacteriorhodopsin (BR), which is capable of electrical response upon exposure to light, is a promising material for photovoltaics and optoelectronics. However, the rather narrow absorption spectrum of BR does not allow achieving efficient conversion of the light energy in the blue and infrared spectral regions. This paper summarizes the results of studies showing the possibility of extending the spectral region of the BR function by means of the Förster resonance energy transfer (FRET) from CdSe/ZnS quantum dots (QDs), which have a broad spectrum of one-photon absorption and a large twophoton absorption cross section (TPACS), to BR upon one- and two-photon excitation. In particular, it is shown that, on the basis of QDs and BR-containing purple membranes, it is possible to create electrostatically associated bio-nano hybrid systems in which FRET is implemented. In addition, the large TPACS of QDs, which is two orders of magnitude larger than those of BR and organic dyes, opens up a means for selective two-photon excitation of synthesized bio-nano hybrid complexes. On the basis of the results of this work, the spectral region in which BR converts the light energy into electrical energy can be extended from the UV to near-IR region, creating new opportunities for the use of this material in photovoltaics and optoelectronics.

  4. Suitable photo-resists for two-photon polymerization using femtosecond fiber lasers

    KAUST Repository

    Rajamanickam, V.P.

    2014-06-01

    We present suitable materials with good optical and mechanical properties, simple processing, efficient and optimized for two-photon polymerization (TPP) with femtosecond fiber lasers. We selected readily available acrylic monomer Bisphenol A ethoxylate diacrylate (BPA-EDA) with three different photo-initiators (PIs), isopropyl thioxanthone (ITX), 7-diethylamino-3-thenoylcoumarin (DETC), and 4,4′ bis(diethylamino) benzophenone (BDEB), since their absorption spectra match well with the laser wavelength at 780 nm. These PIs grant efficient radical generation, reactivity and high solubility in acrylic monomers. Finally, good optical and mechanical properties are demonstrated by the fabrication of different micro-structures.

  5. Polarised two-photon excitation of quantum well excitons for manipulation of optically pumped terahertz lasers

    Energy Technology Data Exchange (ETDEWEB)

    Slavcheva, G., E-mail: gsk23@bath.ac.uk [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom); Kavokin, A.V., E-mail: A.Kavokin@soton.ac.uk [School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Spin Optics Laboratory, St. Petersburg State University, 1, Ulyanovskaya 198504 (Russian Federation)

    2014-11-15

    Optical pumping of excited exciton states in a semiconductor quantum well embedded in a microcavity is a tool for realisation of ultra-compact terahertz (THz) lasers based on stimulated optical transition between excited (2p) and ground (1s) exciton state. We show that the probability of two-photon absorption by a 2p-exciton is strongly dependent on the polarisation of both pumping photons. Five-fold variation of the threshold power for terahertz lasing by switching from circular to co-linear pumping is predicted. We identify photon polarisation configurations for achieving maximum THz photon generation quantum efficiency.

  6. Two-photon polarization data storage in bacteriorhodopsin films and its potential use in security applications

    Science.gov (United States)

    Imhof, Martin; Rhinow, Daniel; Hampp, Norbert

    2014-02-01

    Bacteriorhodopsin (BR) films allow write-once-read-many recording of polarization data by a two-photon-absorption (TPA) process. The optical changes in BR films induced by the TPA recording were measured and the Müller matrix of a BR film was determined. A potential application of BR films in security technology is shown. Polarization data can be angle-selective retrieved with high signal-to-noise ratio. The BR film does not only carry optical information but serves also as a linear polarizer. This enables that polarization features recorded in BR films may be retrieved by merely using polarized light from a mobile phone display.

  7. Two-photon polarization data storage in bacteriorhodopsin films and its potential use in security applications

    Energy Technology Data Exchange (ETDEWEB)

    Imhof, Martin; Hampp, Norbert, E-mail: hampp@staff.uni-marburg.de [Department of Chemistry, Material Sciences Center, University of Marburg, Hans-Meerwein-Str., D-35032 Marburg (Germany); Rhinow, Daniel [Max-Planck-Institute of Biophysics, Max-von-Laue-Straße 3, D-60438 Frankfurt (Germany)

    2014-02-24

    Bacteriorhodopsin (BR) films allow write-once-read-many recording of polarization data by a two-photon-absorption (TPA) process. The optical changes in BR films induced by the TPA recording were measured and the Müller matrix of a BR film was determined. A potential application of BR films in security technology is shown. Polarization data can be angle-selective retrieved with high signal-to-noise ratio. The BR film does not only carry optical information but serves also as a linear polarizer. This enables that polarization features recorded in BR films may be retrieved by merely using polarized light from a mobile phone display.

  8. In vitro imaging of thyroid tissues using two-photon excited fluorescence and second harmonic generation.

    Science.gov (United States)

    Huang, Zufang; Li, Zuanfang; Chen, Rong; Lin, Juqiang; Li, Yongzeng; Li, Chao

    2010-08-01

    To evaluate the feasibility of two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) imaging to discriminate the normal, nodular goiter and papillary cancerous thyroid tissue. In total, 45 fresh thyroid specimens (normal, 15; nodular goiter, 12; and papillary cancerous, 18) from 31 subjects were directly imaged by the TPEF and SHG combination method. The microstructure of follicle and collagen structure in thyroid tissue were clearly identified, morphologic changes between normal, nodular goiter, and papillary cancerous thyroid tissue were well characterized by using two-photon excitation fluorescence. SHG imaging of the collagen matrix also revealed the differences between normal and abnormal. Our preliminary study suggests that the TPEF and SHG combination method might be a useful tool in revealing pathologic changes in thyroid tissue.

  9. Characterization of oxidized carbon materials with photoinduced absorption response

    Science.gov (United States)

    Uklein, A. V.; Diyuk, V. E.; Grishchenko, L. M.; Kozhanov, V. O.; Boldyrieva, O. Yu.; Lisnyak, V. V.; Multian, V. V.; Gayvoronsky, V. Ya.

    2016-12-01

    An efficient application of fast remote diagnostics for carbon material (CM) bulk particles was demonstrated. Porous layers of CM particles with different oxidation levels were characterized by self-action of picosecond laser pulses at 1064 nm. Nitrogen adsorption, Boehm titration, and thermal analysis of the oxidized CMs revealed diverse specific surface area S_{BET}, reasonable surface acidity, and high concentration of surface oxygen-containing groups. Dense CM porous layers showed a monotonous reduction of the absorptive nonlinear optical (NLO) response efficiency versus the oxidation level with characteristic magnitude Im(χ _C^{(3)})˜ 10^{-10} esu for the carbon particles fraction. The obtained Im(χ _C^{(3)})/S_{BET} ratio remains approximately constant, which indicates the certain proportion between the absorptive NLO response efficiency and the specific surface area. We suggest to use Im(χ _C^{(3)}) as a figure of merit for carbons subjected to the oxidation—the route to enhance the CM surface reactivity.

  10. 540--900 nm photodissociation of 300 K NCNO: One- and two-photon processes

    Energy Technology Data Exchange (ETDEWEB)

    Nadler, I.; Pfab, J.; Reisler, H.; Wittig, C.

    1984-07-15

    The laser photodissociation of 300 K NCNO throughout the region 540--900 nm is reported, and both 1- and 2-photon processes are discussed. By monitoring CN fragments produced via the 1-photon process, we show that with photolysis wavelengths >592 nm, dissociation occurs predominantly by exciting NCNO ''hot bands.'' At shorter photolysis wavelengths, dissociation from the ground vibrational state of NCNO is observed as well, but the contributions from hot bands are still manifest in high CN rotational levels which are energetically inaccessible from the ground state (D/sub 0/ = 48.8 kcal mol/sup -1/). Energy distributions in the CN fragments were determined for excess energies up to 1800 cm/sup -1/, and are in agreement with phase space theory calculations and a vibrational predissociation mechanism. In addition, throughout the region 620--900 nm, stepwise two-photon photodissociation proceeds using the A /sup 1/A'' state as a gateway, and results in rotationally and vibrationally ''hot'' CN fragments. The hot CN fragment yield vs photolysis wavelength shows peaks which correspond exactly to peaks in the NCNO absorption spectrum, allowing us to obtain high resolution spectra of the A /sup 1/A''reverse arrow X /sup 1/A' absorption system. The one- and two-photon processes are in competition, and the latter disappears at wavelengths where one-photon photodissociation of NCNO via its ground vibrational level sets in. The nature of the electronic states involved in the one- and two-photon processes is also discussed.

  11. NEAR-IR TWO PHOTON MICROSCOPY IMAGING OF SILICA NANOPARTICLES FUNCTIONALIZED WITH ISOLATED SENSITIZED Yb(III) CENTERS

    Energy Technology Data Exchange (ETDEWEB)

    Lapadula, Giuseppe; Bourdolle, Adrien; Allouche, Florian; Conley, Matthew P.; Maron, Laurent; Lukens, Wayne W.; Guyot, Yannick; Andraud, Chantal; Brasselet, Sophie; Copé; ret, Christophe; Maury, Olivier; Andersen, Richard A.

    2013-01-12

    Bright nano objects emitting in the near infrared with a maximal cross section of 41.4 x 103 GM (Goppert Mayer), were prepared by implanting ca. 180 4,4 diethylaminostyryl 2,2 bipyridine (DEAS) Yb(III) complexes on the surface of 12 nm silica nanoparticles. The surface complexes ([DEAS Ln SiO2], Ln =Y,Yb) were characterized using IR, solid state NMR, UV Vis, EXAFS spectroscopies in combination with the preparation and characterization of similar molecular analogues by analytical techniques (IR, solution NMR, UV Vis, X ray crystallography) as well as DFT calculations. Starting from the partial dehydroxylation of the silica at 700 C on high vacuum having 0.8 OH.nm 2, the grafting of Ln(N(SiMe3)2)3 generate ≤SiO Ln(N(SiMe3)2)2, which upon thermal step and coordination of the DEAS chromophore yields (≤SiO)3Ln(DEAS). Surface and molecular analogues display similar properties, in terms of DEAS binding constants absorption maxima and luminescence properties (intense emission band assigned to a ligand centered CT fluorescence and life time) in the solid state, consistent with the molecular nature of the surface species. The densely functionalized nanoparticles can be dispersed via ultra-sonication in small ca. 15-20 nm aggregates (1 to 6 elementary particles) that were detected using two photon microscopy imaging at 720 nm excitation, making them promising nano objects for bio imaging.

  12. Synthesizing arbitrary two-photon polarization mixed states

    CERN Document Server

    Wei, T C; Branning, D; Goldbart, P M; James, D F V; Jeffrey, E; Kwiat, P G; Mukhopadhyay, S; Peters, N A; Wei, Tzu-Chieh; Altepeter, Joseph B.; Branning, David; Goldbart, Paul M.; Jeffrey, Evan; Kwiat, Paul G.; Mukhopadhyay, Swagatam; Peters, Nicholas A.

    2005-01-01

    Two methods for creating arbitrary two-photon polarization pure states are introduced. Based on these, four schemes for creating two-photon polarization mixed states are proposed and analyzed. The first two schemes can synthesize completely arbitrary two-qubit mixed states, i.e., control all 15 free parameters: Scheme I requires several sets of crystals, while Scheme II requires only a single set, but relies on decohering the pump beam. Additionally, we describe two further schemes which are much easier to implement. Although the total capability of these is still being studied, we show that they can synthesize all two-qubit Werner states, maximally entangled mixed states, Collins-Gisin states, and arbitrary Bell-diagonal states.

  13. Direct frequency comb two-photon laser cooling and trapping

    Science.gov (United States)

    Jayich, Andrew; Long, Xueping; Campbell, Wesley C.

    2016-05-01

    Generating and manipulating high energy photons for spectroscopy on electric dipole transitions of atoms and molecules with deeply bound valence electrons is difficult. Further, laser cooling of such species is even more challenging for lack of laser power. A possible solution is to drive two-photon transitions. This may alleviate the photon energy problem and open the door to cold, trapped samples of highly desirable species with tightly bound electrons. We perform a proof of principle experiment with rubidium by driving a two-photon transition with an optical frequency comb. We perform optical cooling and extend this technique to trapping, where we are able to make a magneto-optical trap in one dimension. This work is supported by the National Science Foundation CAREER program.

  14. Two-photon excited ultraviolet photoluminescence of zinc oxide nanorods.

    Science.gov (United States)

    Zhu, Guangping; Xu, Chunxiang; Zhu, Jing; Lu, Changgui; Cui, Yiping; Sun, Xiaowei

    2008-11-01

    High density zinc oxide nanorods with uniform size were synthesized on (100) silicon substrate by vapor-phase transport method. The scanning electron microscopy images reveal that the nanorods have an average diameter of about 400 nm. The X-ray diffraction pattern demonstrates the wurtzite crystalline structure of the ZnO nanorods growing along [0001] direction. The single-photon excited photoluminescence presents a strong ultraviolet emission band at 394 nm and a weak visible emission band at 600 nm. When the ZnO nanorods were respectively pumped by various wavelength lasers from 520 nm to 700 nm, two-photon excited ultraviolet photoluminescence was observed. The dependence of the two-photon excited photoluminescence intensity on the excitation wavelength and power was investigated in detail.

  15. High-order dispersion effects in two-photon interference

    CERN Document Server

    Mazzotta, Z; Cipriani, D; Olivares, S; Paris, M G A

    2016-01-01

    Two-photon interference and Hong-Ou-Mandel (HOM) effect are relevant tools for quantum metrology and quantum information processing. In optical coherence tomography, HOM effect is exploited to achieve high-resolution measurements with the width of the HOM dip being the main parameter. On the other hand, applications like dense coding require high-visibility performances. Here we address high-order dispersion effects in two-photon interference and study, theoretically and experimentally, the dependence of the visibility and the width of the HOM dip on both the pump spectrum and the downconverted photon spectrum. In particular, a spatial light modulator is exploited to experimentally introduce and manipulate a custom phase function to simulate the high-order dispersion effects.

  16. Two-photon interference from two blinking quantum emitters

    Science.gov (United States)

    Jöns, Klaus D.; Stensson, Katarina; Reindl, Marcus; Swillo, Marcin; Huo, Yongheng; Zwiller, Val; Rastelli, Armando; Trotta, Rinaldo; Björk, Gunnar

    2017-08-01

    We investigate the effect of blinking on the two-photon interference measurement from two independent quantum emitters. We find that blinking significantly alters the statistics in the Hong-Ou-Mandel second-order intensity correlation function g(2 )(τ ) and the outcome of two-photon interference measurements performed with independent quantum emitters. We theoretically demonstrate that the presence of blinking can be experimentally recognized by a deviation from the gD(2 )(0 ) =0.5 value when distinguishable photons from two emitters impinge on a beam splitter. Our findings explain the significant differences between linear losses and blinking for correlation measurements between independent sources and are experimentally verified using a parametric down-conversion photon-pair source. We show that blinking imposes a mandatory cross-check measurement to correctly estimate the degree of indistinguishability of photons emitted by independent quantum emitters.

  17. Two-photon interaction between trapped ions and cavity fields

    CERN Document Server

    Semião, F L

    2006-01-01

    In this paper, we generalize the ordinary two-photon Jaynes-Cummings model (TPJCM) by considering the atom (or ion) to be trapped in a simple harmonic well. A typical setup would be an optical cavity containing a single ion in a Paul trap. Due to the inclusion of atomic vibrational motion, the atom-field coupling becomes highly nonlinear what brings out quite different behaviors for the system dynamics when compared to the ordinary TPJCM. In particular, we derive an effective two-photon Hamiltonian with dependence on the number operator of the ion's center-of-mass motion. This dependence occurs both in the cavity induced Stark-shifs and in the ion-field coupling, and its role in the dynamics is illustrated by showing the time evolution of the probability of occupation of the electronic levels for simple initial preparations of the state of the system.

  18. Two-photon microscopy using fiber-based nanosecond excitation.

    Science.gov (United States)

    Karpf, Sebastian; Eibl, Matthias; Sauer, Benjamin; Reinholz, Fred; Hüttmann, Gereon; Huber, Robert

    2016-07-01

    Two-photon excitation fluorescence (TPEF) microscopy is a powerful technique for sensitive tissue imaging at depths of up to 1000 micrometers. However, due to the shallow penetration, for in vivo imaging of internal organs in patients beam delivery by an endoscope is crucial. Until today, this is hindered by linear and non-linear pulse broadening of the femtosecond pulses in the optical fibers of the endoscopes. Here we present an endoscope-ready, fiber-based TPEF microscope, using nanosecond pulses at low repetition rates instead of femtosecond pulses. These nanosecond pulses lack most of the problems connected with femtosecond pulses but are equally suited for TPEF imaging. We derive and demonstrate that at given cw-power the TPEF signal only depends on the duty cycle of the laser source. Due to the higher pulse energy at the same peak power we can also demonstrate single shot two-photon fluorescence lifetime measurements.

  19. Four-dimensional multi-site two-photon excitation

    CERN Document Server

    Daria, Vincent Ricardo; Bowman, Richard; Redman, Stephen; Bachor, Hans-A

    2009-01-01

    We report the first demonstration of dynamic and arbitrary multi-site two-photon excitation in three-dimensional (3D) space using the holographic projection method. Rapid temporal response (fourth dimension) is achieved through high-speed non-iterative and non-optimized calculation of the hologram using a video graphics accelerator board. We verify that the projected asymmetric spot configurations have sufficient spatiotemporal photon density for localized two-photon excitation. This system is a significant advance and ready for applications such as time-resolved 3D photolysis of complex biological cell and neuronal networks, 3D microscopy, non-linear micro-fabrication and volume holographic optical storage.

  20. Simultaneous two-photon excitation of photodynamic therapy agents

    Energy Technology Data Exchange (ETDEWEB)

    Wachter, E.A.; Fisher, W.G. [Oak Ridge National Lab., TN (United States)]|[Photogen, Inc., Knoxville, TN (United States); Partridge, W.P. [Oak Ridge National Lab., TN (United States); Dees, H.C. [Photogen, Inc., Knoxville, TN (United States); Petersen, M.G. [Univ. of Tennessee, Knoxville, TN (United States). College of Veterinary Medicine

    1998-01-01

    The spectroscopic and photochemical properties of several photosensitive compounds are compared using conventional single-photon excitation (SPE) and simultaneous two-photon excitation (TPE). TPE is achieved using a mode-locked titanium:sapphire laser, the near infrared output of which allows direct promotion of non-resonant TPE. Excitation spectra and excited state properties of both type 1 and type 2 photodynamic therapy (PDT) agents are examined.

  1. Two-photon imaging through a multimode fiber

    CERN Document Server

    Morales-Delgado, Edgar E; Moser, Christophe

    2015-01-01

    In this work we demonstrate 3D imaging using two-photon excitation through a 20 cm long multimode optical fiber (MMF) of 350 micrometers diameter. The imaging principle is similar to single photon fluorescence through a MMF, except that a focused femtosecond pulse is delivered and scanned over the sample. In our approach, focusing and scanning through the fiber is accomplished by digital phase conjugation using mode selection by time gating with an ultra-fast reference pulse. The excited two-photon emission is collected through the same fiber. We demonstrate depth sectioning by scanning the focused pulse in a 3D volume over a sample consisting of fluorescent beads suspended in a polymer. The achieved resolution is 1 micrometer laterally and 15 micrometers axially. Scanning is performed over an 80x80 micrometers field of view. To our knowledge, this is the first demonstration of high-resolution three-dimensional imaging using two-photon fluorescence through a multimode fiber.

  2. Two-photon production of charged pion and kaon pairs

    CERN Document Server

    Dominick, J; Sanghera, S; Shelkov, V; Skwarnicki, T; Stroynowski, R; Volobuev, I P; Wei, G; Zadorozhny, P; Artuso, M; Goldberg, M; He, D; Horwitz, N; Kennett, R; Mountain, R; Moneti, G C; Muheim, F; Mukhin, Y; Playfer, S; Rozen, Y; Stone, S; Thulasidas, M; Vasseur, G; Zhu, G; Bartelt, J; Csorna, S E; Egyed, Z; Jain, V; Kinoshita, K; Edwards, K W; Ogg, M; Britton, D I; Hyatt, E R F; MacFarlane, D B; Patel, P M; Akerib, D S; Barish, B C; Chadha, M; Chan, S; Cowen, D F; Eigen, G; Miller, J S; O'Grady, C; Urheim, J; Weinstein, A J; Acosta, D; Athanas, M; Masek, G E; Paar, H P; Sivertz, M; Gronberg, J B; Kutschke, R; Menary, S R; Morrison, R J; Nakanishi, S; Nelson, H N; Nelson, T K; Qiao, C; Richman, J D; Ryd, A; Tajima, H; Sperka, D; Witherell, M S; Procario, M; Balest, R; Cho, K; Daoudi, M; Ford, W T; Johnson, D R; Lingel, K; Lohner, M; Rankin, P; Smith, J G; Alexander, J P; Bebek, C; Berkelman, K; Bloom, K; Browder, T E; Cassel, David G; Cho, H A; Coffman, D M; Drell, P S; Ehrlich, R; Gaidarev, P B; Galik, R S; García-Sciveres, M; Geiser, B; Gittelman, B; Gray, S W; Hartill, D L; Heltsley, B K; Jones, C D; Jones, S L; Kandaswamy, J; Katayama, N; Kim, P C; Kreinick, D L; Ludwig, G S; Masui, J; Mevissen, J; Mistry, N B; Ng, C R; Nordberg, E; Patterson, J R; Peterson, D; Riley, D; Salman, S; Sapper, M; Würthwein, F; Avery, P; Freyberger, A P; Rodríguez, J; Stephens, R; Yang, S; Yelton, J; Cinabro, D; Henderson, S; Liu, T; Saulnier, M; Wilson, R; Yamamoto, H; Bergfeld, T; Eisenstein, B I; Gollin, G; Ong, B; Palmer, M; Selen, M; Thaler, J J; Sadoff, A J; Ammar, R; Ball, S; Baringer, P; Bean, A; Besson, D; Coppage, D; Copty, N K; Davis, R; Hancock, N; Kelly, M; Kwak, N; Lam, H; Kubota, Y; Lattery, M; Nelson, J K; Patton, S; Perticone, D; Poling, R A; Savinov, V; Schrenk, S; Wang, R; Alam, M S; Kim, I J; Nemati, B; O'Neill, J J; Severini, H; Sun, C R; Zoeller, M M; Crawford, G; Daubenmier, C M; Fulton, R; Fujino, D; Gan, K K; Honscheid, K; Kagan, H; Kass, R; Lee, J; Malchow, R L; Skovpen, Y; Sung, M; White, C; Butler, F; Fu, X; Kalbfleisch, G R; Ross, W R; Skubic, P L; Snow, J; Wang, P L; Wood, M; Brown, D N; Fast, J; McIlwain, R L; Miao, T; Miller, D H; Modesitt, M; Payne, D; Shibata, E I; Shipsey, I P J; Wang Pei Ning; Battle, M; Ernst, J; Kwon, Y; Roberts, S; Thorndike, E H; Wang, C H

    1994-01-01

    A measurement of the cross section for the combined two-photon production of charged pion and kaon pairs is performed using 1.2~\\rm fb^{-1} of data collected by the CLEO II detector at the Cornell Electron Storage Ring. The cross section is measured at invariant masses of the two-photon system between 1.5 and 5.0~GeV/c^2, and at scattering angles more than 53^\\circ away from the \\gamma\\gamma collision axis in the \\gamma\\gamma center-of-mass frame. The large background of leptonic events is suppressed by utilizing the CsI calorimeter in conjunction with the muon chamber system. The reported cross section is compared with leading order QCD models as well as previous experiments. In particular, although the functional dependence of the measured cross section disagrees with leading order QCD at small values of the two-photon invariant mass, the data show a transition to perturbative behavior at an invariant mass of approximately 2.5~GeV/c^2. hardcopies with figures can be obtained by writing to to: Pam Morehouse ...

  3. Two photon exchange in elastic electron-nucleon scattering

    Energy Technology Data Exchange (ETDEWEB)

    Peter Blunden; Wolodymyr Melnitchouk; John Tjon

    2005-06-01

    A detailed study of two-photon exchange in unpolarized and polarized elastic electron-nucleon scattering is presented, taking particular account of nucleon finite size effects. Contributions from nucleon elastic intermediate states are found to have a strong angular dependence, which leads to a partial resolution of the discrepancy between the Rosenbluth and polarization transfer measurements of the proton electric to magnetic form factor ratio. The two-photon exchange contribution to the longitudinal polarization transfer ratio P{sub L} is small, whereas the contribution to the transverse polarization transfer ratio P{sub T} is enhanced at backward angles by several percent, increasing with Q{sup 2}. This gives rise to a several percent enhancement of the polarization transfer ratio P{sub T}/P{sub l} at large Q{sup 2} and backward angles. We compare the two-photon exchange effects with data on the ratio of e{sup +p} to e{sup -p} cross sections, which is predicted to be enhanced at backward angles. Finally, we evaluate the corrections to the form factors of the neutron, and estimate the elastic intermediate state contribution to the {sup 3}He form factors.

  4. Recent two-photon physics results from ARGUS

    Science.gov (United States)

    Živko Representing Argus Collaboration, Tomi

    1995-07-01

    Two photon production of π+π+π0π-π-, K+K-π+π-, K+K-π+π0π-, π+π0π-, and π+π- has been studied using the ARGUS detector at the e+e- storage ring DORIS II at DESY. A partial wave analysis was performed on the five-pion and three-pion final states. In the reaction γγ→ωρ0 is showed that the partial-wave with spin and parity (JP,Jz)=(2+,±2) dominates. The cross section and angular distributions of the reaction γγ→φρ0→K+K-π+π- were measured for the first time. The production of the vector-meson pair φω is observed in the two-photon reaction γγ→K+K-π+π0π-. The two-photon width of the tensor meson a2(1320) was measured in the decay channel π+π0π-. An upper limit, significantly lower than indicated by previous experiments was set on the radiative width of the π2(1670) meson. An upper limit was set on the radiative width of the f0(975)in the decay channel π+π-.

  5. Diagnosis of basal cell carcinoma by two photon excited fluorescence combined with lifetime imaging

    Science.gov (United States)

    Fan, Shunping; Peng, Xiao; Liu, Lixin; Liu, Shaoxiong; Lu, Yuan; Qu, Junle

    2014-02-01

    Basal cell carcinoma (BCC) is the most common type of human skin cancer. The traditional diagnostic procedure of BCC is histological examination with haematoxylin and eosin staining of the tissue biopsy. In order to reduce complexity of the diagnosis procedure, a number of noninvasive optical methods have been applied in skin examination, for example, multiphoton tomography (MPT) and fluorescence lifetime imaging microscopy (FLIM). In this study, we explored two-photon optical tomography of human skin specimens using two-photon excited autofluorescence imaging and FLIM. There are a number of naturally endogenous fluorophores in skin sample, such as keratin, melanin, collagen, elastin, flavin and porphyrin. Confocal microscopy was used to obtain structures of the sample. Properties of epidermic and cancer cells were characterized by fluorescence emission spectra, as well as fluorescence lifetime imaging. Our results show that two-photon autofluorescence lifetime imaging can provide accurate optical biopsies with subcellular resolution and is potentially a quantitative optical diagnostic method in skin cancer diagnosis.

  6. Two-photon spectroscopic behaviors and photodynamic effect on the BEL-7402 cancer cells of the new chlorophyll photosensitizer

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The spectroscopic properties of a new chlorophyll derivate photosensitizer(CDP) are studied under the excitation wavelengths at 800 and 400 nm using femtosecond pulses from a Ti:sapphire laser.The damaging effect of CDP on the BEL-7402 cancer cells is also investigated upon two-photon illumination at 800 nm.The normalized fluorescence spectra of CDP in tetrahydrofuran(THF) show that two-photon and one-photon spectra have the same distributions and the same emission bands(675 nm).The life-times of two-and one-photon induced fluorescence of this molecule are of the order of 5.0 ns.By comparing the data it is shown that there is some difference between the two lifetimes,but the differ-ence is less than one nanosecond.The two-photon absorption cross section of the molecule is also measured at 800 nm and estimated as about σ′2 ≈ 31.5×10-50 cm4·s·photon-1.The results of two-photon photodynamic therapy(TPPDT) tests show that CDP can kill all of the tested cancer cells according to the usual Eosine assessment.Our results indicate that the two-photon-induced photophysical,photo-chemical and photosensitizing processes of CDP may be basically similar to those of one-photon ex-citation.These behaviors of the sample suggest that one may find other possible methods to estimate some photosensitizers’ effects in details such as their distribution in cells and the reactive targets of the sub-cellular parts of some tumor cells via two-photon excitation techniques.

  7. Two-photon spectroscopic behaviors and photodynamic effect on the BEL-7402 cancer cells of the new chlorophyll photosensitizer

    Institute of Scientific and Technical Information of China (English)

    ZHAO PeiDe; ZHANG GuiLan; CHEN WenJu; CHEN Ping; TANG GuoQing; LIU JinWei; LIN Lie; GUO Peng; YU Qing; YAO JianZhong; MA DongMing

    2008-01-01

    The spectroscopic properties of a new chlorophyll derivate photosensitizer (CDP) are studied under the excitation wavelengths at 800 and 400 nm using femtosecond pulses from a Ti: sapphire laser. The damaging effect of CDP on the BEL-7402 cancer cells is also investigated upon two-photon illumination at 800 nm. The normalized fluorescence spectra of CDP in tetrahydrofuran (THF) show that two-photon and one-photon spectra have the same distributions and the same emission bands (675 nm). The life-times of two- and one-photon induced fluorescence of this molecule are of the order of 5.0 ns. By comparing the data it is shown that there is some difference between the two lifetimes, but the differ-ence is less than one nanosecond. The two-photon absorption cross section of the molecule is also measured at 800 nm and estimated as about σ'2≈31.5×10-50 cm4·s·photon-1. The results of two-photon photodynamic therapy (TPPDT) tests show that CDP can kill all of the tested cancer cells according to the usual Eosine assessment. Our results indicate that the two-photon-induced photophysical, photochemical and photosensitizing processes of CDP may be basically similar to those of one-photon excitation. These behaviors of the sample suggest that one may find other possible methods to estimate some photosensitizers' effects in details such as their distribution in cells and the reactive targets of the sub-cellular parts of some tumor cells via two-photon excitation techniques.

  8. (Un)determined finite regularization dependent quantum corrections: the Higgs decay into two photons and the two photon scattering examples

    CERN Document Server

    Cherchiglia, A L; Nemes, M C; Sampaio, Marcos

    2012-01-01

    We investigate the appearance of arbitrary, regularization dependent parameters introduced by divergent integrals in two a priori finite but superficially divergent amplitudes: the Higgs decay into two photons and the two photon scattering. We use a general parametrization of ultraviolet divergences which explicitates such ambiguities. Thus we separate in a consistent way using Implicit Regularization the divergent, finite and regularization dependent parts of the amplitudes which in turn are written as surface terms. We find that, although finite, these amplitudes are ambiguous before the imposition of physical conditions namely momentum routing invariance in the loops of Feynman diagrams. In the examples we study momentum routing invariance turns out to be equivalent to gauge invariance. We also discuss the results obtained by different regularizations and show how they can be reproduced within our framework allowing for a clear view on the origin of regularization ambiguities.

  9. Confinement of pyridinium hemicyanine dye within an anionic metal-organic framework for two-photon-pumped lasing

    Science.gov (United States)

    Yu, Jiancan; Cui, Yuanjing; Xu, Hui; Yang, Yu; Wang, Zhiyu; Chen, Banglin; Qian, Guodong

    2013-10-01

    Two-photon-pumped dye lasers are very important because of their applications in wavelength up-conversion, optical data storage, biological imaging and photodynamic therapy. Such lasers are very difficult to realize in the solid state because of the aggregation-caused quenching. Here we demonstrate a new two-photon-pumped micro-laser by encapsulating the cationic pyridinium hemicyanine dye into an anionic metal-organic framework (MOF). The resultant MOF⊃dye composite exhibits significant two-photon fluorescence because of the large absorption cross-section and the encapsulation-enhanced luminescent efficiency of the dye. Furthermore, the well-faceted MOF crystal serves as a natural Fabry-Perot resonance cavity, leading to lasing around 640 nm when pumped with a 1064-nm pulse laser. This strategy not only combines the crystalline benefit of MOFs and luminescent behaviour of organic dyes but also creates a new synergistic two-photon-pumped lasing functionality, opening a new avenue for the future creation of solid-state photonic materials and devices.

  10. New two-photon based nanoscopic modalities and optogenetics

    DEFF Research Database (Denmark)

    Glückstad, Jesper

    -matter interaction on these scales involves the combination of optimal light-sculpting [4] with the use of optimized shapes in micro-robotics structures [5]. Microfabrication processes such as two-photon photo-polymerization offer three-dimensional resolutions for creating custom-designed monolithic microstructures...... that can be equipped with optical trapping handles for convenient mechanical control using only optical forces [6]. These microstructures illustrated above can be effectively handled with simultaneous top- and side-view on our BioPhotonics Workstation to undertake six-degree-of-freedom optical actuation...

  11. Two-photon polymerization of immune cell scaffolds

    DEFF Research Database (Denmark)

    Olsen, Mark Holm

    and easy to use chip integrated migration platform. Free-form constructs with three-dimensional (3D) microporosity were fabricated by two-photon polymerization inside the closed microchannel of an injection molded commercially available polymer chip for analysis of directed cell migration. Acrylate...... also present a poly (ethylene glycol) diacrylate (PEGDA) based strategy to fabricate soft 3D hydrogel scaffolds. Our experiments with the hydrogel confirm we can control the mechanical properties and introduce biochemical cues on the surface that are recognized by fibroblast cells. Finally we present...

  12. The Nelson Model with Less Than Two Photons

    CERN Document Server

    Galtbayar, A; Yajima, K

    2002-01-01

    We study the spectral and scattering theory of the Nelson model for an atom interacting with a photon field in the subspace with less than two photons. For the free electron-photon system, the spectral property of the reduced Hamiltonian in the center of mass coordinates and the large time dynamics are determined. If the electron is under the influence of the nucleus via spatially decaying potentials, we locate the essential spectrum, prove the absence of singular continuous spectrum and the existence of the ground state, and construct wave operators giving the asymptotic dynamics.

  13. Two-photon tomography using on-chip quantum walks

    CERN Document Server

    Titchener, James; Sukhorukov, Andrey

    2016-01-01

    We present a conceptual approach to quantum tomography based on first expanding a quantum state across extra degrees of freedom and then exploiting the introduced sparsity to perform reconstruction. We formulate its application to photonic circuits, and show that measured spatial photon correlations at the output of a specially tailored discrete-continuous quantum-walk can enable full reconstruction of any two-photon spatially entangled and mixed state at the input. This approach does not require any tunable elements, so is well suited for integration with on-chip superconducting photon detectors.

  14. Two Photon Decays of Charmonia from Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Jozef Dudek; Robert Edwards

    2006-07-12

    We make the first calculation in lattice QCD of two-photon decays of mesons. Working in the charmonium sector, using the LSZ reduction to relate a photon to a sum of hadronic vector eigenstates, we compute form-factors in both the space-like and time-like domains for the transitions {eta}{sub c} {yields} {gamma}*{gamma}* and {chi}{sub c0} {yields} {gamma}*{gamma}*. At the on-shell point we find approximate agreement with experimental world-average values.

  15. Quantum teleportation of one- and two-photon superposition states

    Institute of Scientific and Technical Information of China (English)

    李英; 张天才; 张俊香; 谢常德

    2003-01-01

    Quantum teleportation of one- and two-photon superposition states based on EPR entanglement of continuouswave two-mode squeezed state is discussed. The fidelities of teleportation are deduced for two different input quantum states. The dependence of the fidelity on the parameters of EPR entanglement and the gain of the classical channels are shown numerically. Comparing with the teleportation of Fock state and coherent state, it is pointed out that for given EPR entanglement and classical gain, the higher the nonclassicality of the input state, the lower the accessible fidelity of teleportation.

  16. Inclusive $D*^{+-}$ Production in Two-Photon Collisions at LEP

    CERN Document Server

    Achard, P; Aguilar-Benítez, M; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alviggi, M G; Anderhub, H; Andreev, V P; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Bajo, A; Baksay, G; Baksay, L; Baldew, S V; Banerjee, S; Banerjee, Sw; Barczyk, A; Barillère, R; Bartalini, P; Basile, M; Batalova, N; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Bellucci, L; Berbeco, R; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Biasini, M; Biglietti, M; Biland, A; Blaising, J J; Blyth, S C; Bobbink, Gerjan J; Böhm, A; Boldizsar, L; Borgia, B; Bottai, S; Bourilkov, D; Bourquin, Maurice; Braccini, S; Branson, J G; Brochu, F; Burger, J D; Burger, W J; Cai, X D; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A M; Casaus, J; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada, M; Chamizo-Llatas, M; Chang, Y H; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chiefari, G; Cifarelli, Luisa; Cindolo, F; Clare, I; Clare, R; Coignet, G; Colino, N; Costantini, S; de la Cruz, B; Cucciarelli, S; van Dalen, J A; De Asmundis, R; Déglon, P L; Debreczeni, J; Degré, A; Deiters, K; Della Volpe, D; Delmeire, E; Denes, P; De Notaristefani, F; De Salvo, A; Diemoz, M; Dierckxsens, M; Dionisi, C; Dittmar, Michael; Doria, A; Dova, M T; Duchesneau, D; Echenard, B; Eline, A; El-Mamouni, H; Engler, A; Eppling, F J; Ewers, A; Extermann, Pierre; Falagán, M A; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, Marta; Ferguson, T; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, Frank; Fisher, P H; Fisher, W; Fisk, I; Forconi, G; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gataullin, M; Gentile, S; Giagu, S; Gong, Z F; Grenier, G; Grimm, O; Grünewald, M W; Guida, M; van Gulik, R; Gupta, V K; Gurtu, A; Gutay, L J; Haas, D; Hakobyan, R S; Hatzifotiadou, D; Hebbeker, T; Hervé, A; Hirschfelder, J; Hofer, H; Hohlmann, M; Holzner, G; Hou, S R; Hu, Y; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Käfer, D; Kaur, M; Kienzle-Focacci, M N; Kim, J K; Kirkby, Jasper; Kittel, E W; Klimentov, A; König, A C; Kopal, M; Koutsenko, V F; Kräber, M H; Krämer, R W; Krenz, W; Krüger, A; Kunin, A; Ladrón de Guevara, P; Laktineh, I; Landi, G; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Le Goff, J M; Leiste, R; Levtchenko, M; Levchenko, P M; Li, C; Likhoded, S A; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lü, Y S; Lübelsmeyer, K; Luci, C; Luminari, L; Lustermann, W; Ma Wen Gan; Malgeri, L; Malinin, A; Maña, C; Mangeol, D J J; Mans, J; Martin, J P; Marzano, F; Mazumdar, K; McNeil, R R; Mele, S; Merola, L; Meschini, M; Metzger, W J; Mihul, A; Milcent, H; Mirabelli, G; Mnich, J; Mohanty, G B; Muanza, G S; Muijs, A J M; Musicar, B; Musy, M; Nagy, S; Natale, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Niessen, T; Nisati, A; Nowak, H; Ofierzynski, R A; Organtini, G; Palomares, C; Pandoulas, D; Paolucci, P; Paramatti, R; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Pedace, M; Pensotti, S; Perret-Gallix, D; Petersen, B; Piccolo, D; Pierella, F; Pioppi, M; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Pothier, J; Prokofiev, D O; Prokofev, D; Quartieri, J; Rahal-Callot, G; Rahaman, M A; Raics, P; Raja, N; Ramelli, R; Rancoita, P G; Ranieri, R; Raspereza, A V; Razis, P A; Ren, D; Rescigno, M; Reucroft, S; Riemann, S; Riles, K; Roe, B P; Romero, L; Rosca, A; Rosier-Lees, S; Roth, S; Rosenbleck, C; Roux, B; Rubio, Juan Antonio; Ruggiero, G; Rykaczewski, H; Sakharov, A; Saremi, S; Sarkar, S; Salicio, J; Sánchez, E; Sanders, M P; Schäfer, C; Shchegelskii, V; Schmidt-Kärst, S; Schmitz, D; Schopper, Herwig Franz; Schotanus, D J; Schwering, G; Sciacca, C; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shumilov, E; Shvorob, A V; Siedenburg, T; Son, D; Spillantini, P; Steuer, M; Stickland, D P; Stoyanov, B; Strässner, A; Sudhakar, K; Sultanov, G G; Sun, L Z; Sushkov, S V; Suter, H; Swain, J D; Szillási, Z; Tang, X W; Tarjan, P; Tauscher, Ludwig; Taylor, L; Tellili, B; Teyssier, D; Timmermans, C; Ting, Samuel C C; Ting, S M; Tonwar, S C; Tóth, J; Tully, C; Tung, K L; Ulbricht, J; Valente, E; Van, R T; De Walle, M; Veszpremi, V; Vesztergombi, G; Vetlitskii, I; Vicinanza, D; Viertel, Gert M; Villa, S; Vivargent, M; Vlachos, S; Vodopyanov, I; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Wadhwa, M; Wallraff, W; Wang, X L; Wang, Z M; Weber, M; Wienemann, P; Wilkens, H; Wynhoff, S; Xia, L; Xu, Z Z; Yamamoto, J; Yang, B Z; Yang, C G; Yang, H J; Yang, M; Yeh, S C; Zalite, A; Zalite, Yu; Zhang, Z P; Zhao, J; Zhu, G Y; Zhu, R Y; Zhuang, H L; Zichichi, A; Zilizi, G; Zimmermann, B; Zöller, M

    2002-01-01

    Inclusive D^{*+-} production in two-photon collisions is studied with the L3 detector at LEP, using 683 pb^{-1} of data collected at centre-of-mass energies from 183 to 208 GeV. Differential cross sections are determined as functions of the transverse momentum and pseudorapidity of the D^{*+-} mesons in the kinematic region 1 GeV e^+e^-D^{*+-}X)$ in this kinematical region is measured and the sigma(e^+e^- ---> e^+e^- cc{bar}X) cross section is derived. The measurements are compared with next-to-leading order perturbative QCD calculations.

  17. Two-photon photoassociative spectroscopy of ultracold 88-Sr

    CERN Document Server

    de Escobar, Y N Martinez; Pellegrini, P; Nagel, S B; Traverso, A; Yan, M; Côté, R; Killian, T C

    2008-01-01

    We present results from two-photon photoassociative spectroscopy of the least-bound vibrational level of the X$^1\\Sigma_g^+$ state of the $^{88}$Sr$_2$ dimer. Measurement of the binding energy allows us to determine the s-wave scattering length, $a_{88}=-1.4(6) a_0$. For the intermediate state, we use a bound level on the metastable $^1S_0$-$^3P_1$ potential, which provides large Franck-Condon transition factors and narrow one-photon photoassociative lines that are advantageous for observing quantum-optical effects such as Autler-Townes resonance splittings.

  18. Two-photon photoassociative spectroscopy of ultracold Sr88

    Science.gov (United States)

    Martinez de Escobar, Y. N.; Mickelson, P. G.; Pellegrini, P.; Nagel, S. B.; Traverso, A.; Yan, M.; Côté, R.; Killian, T. C.

    2008-12-01

    We present results from two-photon photoassociative spectroscopy of the least-bound vibrational level of the XΣg+1 state of the Sr288 dimer. Measurement of the binding energy allows us to determine the s -wave scattering length a88=-1.4(6)a0 . For the intermediate state, we use a bound level on the metastable S01-P13 potential, which provides large Franck-Condon transition factors and narrow one-photon photoassociative lines that are advantageous for observing quantum-optical effects such as Autler-Townes resonance splittings.

  19. A superradiant laser based on two-photon Raman transition of caesium atoms

    CERN Document Server

    Liu, Pengfei

    2013-01-01

    We propose a superradiant laser based on two-photon Raman transition of caesium-133 atoms which collectively emit photons on an ultra narrow transition into the mode of a low Q resonator known as optical bad-cavity regime. The spin-spin correlation which characterizes the collective effect is demonstrated. We theoretically predict that the optical radiation has an extremely narrow linewidth in the 98 (1) *10-2 mHz range, smaller than the transition itself due to collective effects, and a power level of 7 (1)*10-10 W is possible, which can provide a possible new way to realize an optical clock with a millihertz linewidth.

  20. Resonance Two-Photon Ionization of Diarylethene in the Presence of Cyclodextrin

    Directory of Open Access Journals (Sweden)

    Michihiro Hara

    2013-01-01

    Full Text Available The transient absorption of the diarylethene 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl-3,3,4,4,5,5-hexafluoro-1-cyclopentene (DE was measured using 266 nm laser flash photolysis in the presence of various cyclodextrins (CDs in aqueous solvent. Ionization of DE occurred within the laser flash (5 ns to give the DE radical cation and water-solvated electron. The electron was generated by two-photon excitation through simultaneous irradiation with 266 nm laser light, and the ionization quantum yields of DE in the presence of α-CD, β-CD, m-β-CD, and γ-CD depended on the properties of the DE/CD complexes. These results suggest that useful two-photon ionization occurred for these complexes. The ionization quantum yield of DE was found to increase in aqueous solution after the addition of m-β-CD (50 mM, in which m-β-CD likely controlled the photochromic reactivity of DE.

  1. Fully integrated reflection-mode photoacoustic, two-photon, and second harmonic generation microscopy in vivo

    Science.gov (United States)

    Song, Wei; Xu, Qiang; Zhang, Yang; Zhan, Yang; Zheng, Wei; Song, Liang

    2016-01-01

    The ability to obtain comprehensive structural and functional information from intact biological tissue in vivo is highly desirable for many important biomedical applications, including cancer and brain studies. Here, we developed a fully integrated multimodal microscopy that can provide photoacoustic (optical absorption), two-photon (fluorescence), and second harmonic generation (SHG) information from tissue in vivo, with intrinsically co-registered images. Moreover, using a delicately designed optical-acoustic coupling configuration, a high-frequency miniature ultrasonic transducer was integrated into a water-immersion optical objective, thus allowing all three imaging modalities to provide a high lateral resolution of ~290 nm with reflection-mode imaging capability, which is essential for studying intricate anatomy, such as that of the brain. Taking advantage of the complementary and comprehensive contrasts of the system, we demonstrated high-resolution imaging of various tissues in living mice, including microvasculature (by photoacoustics), epidermis cells, cortical neurons (by two-photon fluorescence), and extracellular collagen fibers (by SHG). The intrinsic image co-registration of the three modalities conveniently provided improved visualization and understanding of the tissue microarchitecture. The reported results suggest that, by revealing complementary tissue microstructures in vivo, this multimodal microscopy can potentially facilitate a broad range of biomedical studies, such as imaging of the tumor microenvironment and neurovascular coupling. PMID:27576922

  2. Fully integrated reflection-mode photoacoustic, two-photon, and second harmonic generation microscopy in vivo

    Science.gov (United States)

    Song, Wei; Xu, Qiang; Zhang, Yang; Zhan, Yang; Zheng, Wei; Song, Liang

    2016-08-01

    The ability to obtain comprehensive structural and functional information from intact biological tissue in vivo is highly desirable for many important biomedical applications, including cancer and brain studies. Here, we developed a fully integrated multimodal microscopy that can provide photoacoustic (optical absorption), two-photon (fluorescence), and second harmonic generation (SHG) information from tissue in vivo, with intrinsically co-registered images. Moreover, using a delicately designed optical-acoustic coupling configuration, a high-frequency miniature ultrasonic transducer was integrated into a water-immersion optical objective, thus allowing all three imaging modalities to provide a high lateral resolution of ~290 nm with reflection-mode imaging capability, which is essential for studying intricate anatomy, such as that of the brain. Taking advantage of the complementary and comprehensive contrasts of the system, we demonstrated high-resolution imaging of various tissues in living mice, including microvasculature (by photoacoustics), epidermis cells, cortical neurons (by two-photon fluorescence), and extracellular collagen fibers (by SHG). The intrinsic image co-registration of the three modalities conveniently provided improved visualization and understanding of the tissue microarchitecture. The reported results suggest that, by revealing complementary tissue microstructures in vivo, this multimodal microscopy can potentially facilitate a broad range of biomedical studies, such as imaging of the tumor microenvironment and neurovascular coupling.

  3. Two-photon pumped cavity lasing in novel dye doped bulk matrix rods

    Science.gov (United States)

    He, Guang S.; Zhao, Chan F.; Bhawalkar, Jayant D.; Prasad, Paras N.

    1995-12-01

    Trans-4-[p-(N-ethyl-N-hydroxyethylamino)styryl]-N-methylpyridi that possesses a much greater two-photon absorption cross section and much stronger upconversion fluorescence emission than common organic dyes (such as rhodamine), when excited with near infrared laser radiation. Utilizing ASPT doped bulk polymer rods, two-photon pumped frequency upconverted cavity lasing has been accomplished using a Q-switched Nd:YAG laser as the pump source. The wavelength and pulse duration were ˜600 nm and 3-6 ns, respectively, for the cavity lasing; whereas the corresponding values for pump pulses were 1.06 μm and ˜10 ns, respectively. For a 7 mm long sample rod with a dopant concentration d0=8×10-3 M/L, the conversion efficiency from the absorbed pump energy to the cavity lasing output was ˜3.5% at a pump energy level of 1.3 mJ. The lasing lifetime, in terms of pulse numbers, was more than 4×104 pulses at 2 Hz repetition rate and room temperature.

  4. Properties of two-photon pumped cavity lasing in novel dye doped solid matrices

    Energy Technology Data Exchange (ETDEWEB)

    He, G.S.; Bhawalkar, J.D.; Zhao, C.; Prasad, P.N. [State Univ. of New York, Buffalo, NY (United States). Dept. of Chemistry

    1996-05-01

    Two-photon pumped frequency upconversion cavity lasing at {approximately}600 nm is accomplished in three types of dye-doped solid rods pumped with {approximately}10 ns and 1.06-{micro}m IR laser pulses. The dopant is a new dye, trans-4-[p-(N-ethyl-N-(hydroxyethyl)amino)styryl]-N-methylpyridinium tetraphenylborate, abbreviated as ASPT, which possesses a greater two-photon absorption cross section and stronger upconversion fluorescence emission than common commercial dyes (such as rhodamine). Three different materials were chosen as solid matrices: poly(2-hydroxyethyl methacrylate), VYCOR porous glass, and sol-gel glass. Using a Q-switched Nd:YAG pulse laser as the pump source, strong cavity lasing could be achieved in these three ASPT doped solid rods as well as in ASPT solution in a liquid cell. The spectral, temporal, and spatial characteristics of the cavity lasing output have been systematically investigated. The measured output-input characteristics, lasing lifetime, and damage threshold for the three different rods are presented.

  5. Charge Transport in Two-Photon Semiconducting Structures for Solar Fuels.

    Science.gov (United States)

    Liu, Guohua; Du, Kang; Haussener, Sophia; Wang, Kaiying

    2016-10-20

    Semiconducting heterostructures are emerging as promising light absorbers and offer effective electron-hole separation to drive solar chemistry. This technology relies on semiconductor composites or photoelectrodes that work in the presence of a redox mediator and that create cascade junctions to promote surface catalytic reactions. Rational tuning of their structures and compositions is crucial to fully exploit their functionality. In this review, we describe the possibilities of applying the two-photon concept to the field of solar fuels. A wide range of strategies including the indirect combination of two semiconductors by a redox couple, direct coupling of two semiconductors, multicomponent structures with a conductive mediator, related photoelectrodes, as well as two-photon cells are discussed for light energy harvesting and charge transport. Examples of charge extraction models from the literature are summarized to understand the mechanism of interfacial carrier dynamics and to rationalize experimental observations. We focus on a working principle of the constituent components and linking the photosynthetic activity with the proposed models. This work gives a new perspective on artificial photosynthesis by taking simultaneous advantages of photon absorption and charge transfer, outlining an encouraging roadmap towards solar fuels.

  6. On the origin of large two-photon activity of DANS molecule.

    Science.gov (United States)

    Alam, Md Mehboob; Chattopadhyaya, Mausumi; Chakrabarti, Swapan

    2012-11-15

    In this work, using the quadratic response theory and two-state model approach, we have explained the origin of high two-photon activity and the corresponding solvent dependence of 4,4'-dimethyl-amino-nitro-stilbene (DANS) molecule. For this purpose, we have made two structural modifications in the DANS molecule (1) at the donor-acceptor part and (2) at the unsaturated bridge between the two rings and calculated the one- and two-photon (OP and TP) absorption parameters of all the systems in gas phase and in three different solvents, viz., MeCN, THF, and toluene. We found that the removal of donor-acceptor groups from the original DANS molecule vanishes the transition moment between the ground and excited states and also the corresponding dipole moment difference, and the saturation of the π-conjugation bridge between the two rings keeping the donor-acceptor groups intact causes a large decrease in the ground to excited state transition moment. These changes, in turn, decrease the overall TP activity of the molecules as compared to DANS. On the basis of our analysis, we have concluded that neither the donor-acceptor pair nor the π-conjugation bridge between the two, rather their cooperative involvement leads to a large overlap between the ground and virtual and also the virtual and charge-transfer states, which are eventually responsible for the very large TP activity of DANS.

  7. In situ electrical and thermal monitoring of printed electronics by two-photon mapping.

    Science.gov (United States)

    Pastorelli, Francesco; Accanto, Nicolò; Jørgensen, Mikkel; van Hulst, Niek F; Krebs, Frederik C

    2017-06-19

    Printed electronics is emerging as a new, large scale and cost effective technology that will be disruptive in fields such as energy harvesting, consumer electronics and medical sensors. The performance of printed electronic devices relies principally on the carrier mobility and molecular packing of the polymer semiconductor material. Unfortunately, the analysis of such materials is generally performed with destructive techniques, which are hard to make compatible with in situ measurements, and pose a great obstacle for the mass production of printed electronics devices. A rapid, in situ, non-destructive and low-cost testing method is needed. In this study, we demonstrate that nonlinear optical microscopy is a promising technique to achieve this goal. Using ultrashort laser pulses we stimulate two-photon absorption in a roll coated polymer semiconductor and map the resulting two-photon induced photoluminescence and second harmonic response. We show that, in our experimental conditions, it is possible to relate the total amount of photoluminescence detected to important material properties such as the charge carrier density and the molecular packing of the printed polymer material, all with a spatial resolution of 400 nm. Importantly, this technique can be extended to the real time mapping of the polymer semiconductor film, even during the printing process, in which the high printing speed poses the need for equally high acquisition rates.

  8. Optically Pumped Atomic Rubidium Lasers: Two-Photon and Exciplex Excitation Mechanisms

    Science.gov (United States)

    Gallagher, Jeffrey E.

    The Doppler-broadened two-photon absorption (TPA) cross-section for the 52S1/2 → 52 D5/2 transition in Rb is measured using direct absorption methods. The selection rule |DeltaF| ≤ 2 applied to both isotopes yields 17 transitions in 3 Doppler limited lines. A detailed model of the intensity profile was also developed to account for a focused Gaussian beam (with an M2 value of 1.09) propagating through a two-photon absorption medium. A peak absorbance of 24% was observed for an intensity of 6.28 kWcm2 at the focus, a Rb density of 4.6x1015 cm-3 , and a path length of 15 cm. Alkali concentrations from 1.61 - 8.52x1015 cm -3 were monitored in the far wing of the D 2 line. Extracting the hyperfine-broadened TPA cross-section from 87 test configurations, while varying the pump power, alkali concentration and focal length, yielded an error-weighted average of 6.75x10^-21 cm4W with a standard deviation of 3.61x10-21 cm4W. This cross-section is sufficient for a pulsed dye laser to bleach the pump transition in the Two-Photon Pumped Alkali Laser (TPAL) that lases at 420 nm and 5.2 microm. Optically pumped atomic rubidium lasers pumped in the blue satellite of the D2 line from the ground Rb-Ar or Rb-Kr collision pair to the dissociative B2S+1/2 state produce laser emission at 780.2 nm. Lasing is achieved for pump wavelengths of 752.3 to greater than 760 nm for the Rb-Ar system and 757.1 -- 760.4 nm for the Rb-Kr system. Slope efficiencies increase with both Rb and Ar concentrations and exceed 0.25% using a heat pipe configuration. The gain is very high with photon build-up times of 1--3.7 ns. Laser induced heating and subsequent condensation of alkali vapor in the heat pipe configuration currently limits operation to less than 2500 Torr.

  9. Two-Photon Holographic Stimulation of ReaChR

    Science.gov (United States)

    Chaigneau, Emmanuelle; Ronzitti, Emiliano; Gajowa, Marta A.; Soler-Llavina, Gilberto J.; Tanese, Dimitrii; Brureau, Anthony Y. B.; Papagiakoumou, Eirini; Zeng, Hongkui; Emiliani, Valentina

    2016-01-01

    Optogenetics provides a unique approach to remotely manipulate brain activity with light. Reaching the degree of spatiotemporal control necessary to dissect the role of individual cells in neuronal networks, some of which reside deep in the brain, requires joint progress in opsin engineering and light sculpting methods. Here we investigate for the first time two-photon stimulation of the red-shifted opsin ReaChR. We use two-photon (2P) holographic illumination to control the activation of individually chosen neurons expressing ReaChR in acute brain slices. We demonstrated reliable action potential generation in ReaChR-expressing neurons and studied holographic 2P-evoked spiking performances depending on illumination power and pulse width using an amplified laser and a standard femtosecond Ti:Sapphire oscillator laser. These findings provide detailed knowledge of ReaChR's behavior under 2P illumination paving the way for achieving in depth remote control of multiple cells with high spatiotemporal resolution deep within scattering tissue. PMID:27803649

  10. Inclusive D*(+/-) production in two photon collisions at LEP

    CERN Document Server

    Prokofiev, Denis Olegovich

    2001-01-01

    In this thesis I present my results on the measurement of the open charm production in two-photon collision events done with the L3 detector at Large Electron Positron machine (LEP). The data sample was collected from 1997 through 2000 at center-of-mass energies ranging from 183 GeV to 209 GeV, corresponding to a total integrated luminosity of 683.4pb −1. The open charm production in two-photon collision events extrapolated to the full phase space is estimated to be: s&parl0;e+e-&rarrr;e +e-cc&d1;X&parr0;=9 23±69±109±222pb. The differential cross sections d s /dpT(D*±) and d s /d:η(D*±): are also measured as functions of transverse momentum pT(D*±) and the absolute value of pseudorapidity :η(D*±):, respectively. A fit to the data estimating the relative contributions of Direct and Resolved open charm production mechanisms is performed, giving (28.7 ± 5.6)% and (71.3 ± 8.8)%, respectively. Using those relative fractions, the Direct and Resolved process cross sections yield: s&p...

  11. High-order dispersion effects in two-photon interference

    Science.gov (United States)

    Mazzotta, Zeudi; Cialdi, Simone; Cipriani, Daniele; Olivares, Stefano; Paris, Matteo G. A.

    2016-12-01

    Two-photon interference and Hong-Ou-Mandel (HOM) effect are relevant tools for quantum metrology and quantum information processing. In optical coherence tomography, the HOM effect is exploited to achieve high-resolution measurements with the width of the HOM dip being the main parameter. On the other hand, applications like dense coding require high-visibility performance. Here we address high-order dispersion effects in two-photon interference and study, theoretically and experimentally, the dependence of the visibility and the width of the HOM dip on both the pump spectrum and the downconverted photon spectrum. In particular, a spatial light modulator is exploited to experimentally introduce and manipulate a custom phase function to simulate the high-order dispersion effects. Overall, we show that it is possible to effectively introduce high-order dispersion effects on the propagation of photons and also to compensate for such effect. Our results clarify the role of the different dispersion phenomena and pave the way for optimization procedures in quantum technological applications involving PDC photons and optical fibers.

  12. Simultaneous two-photon excitation of photodynamic therapy agents

    Science.gov (United States)

    Wachter, Eric A.; Partridge, W. P., Jr.; Fisher, Walter G.; Dees, Craig; Petersen, Mark G.

    1998-07-01

    The spectroscopic and photochemical properties of several photosensitive compounds are compared using conventional single-photon excitation (SPE) and simultaneous two-photon excitation (TPE). TPE is achieved using a mode-locked titanium:sapphire laser, the near infrared output of which allows direct promotion of non-resonant TPE. Excitation spectra and excited state properties of both type I and type II photodynamic therapy (PDT) agents are examined. In general, while SPE and TPE selection rules may be somewhat different, the excited state photochemical properties are equivalent for both modes of excitation. In vitro promotion of a two-photon photodynamic effect is demonstrated using bacterial and human breast cancer models. These results suggest that use of TPE may be beneficial for PDT, since the technique allows replacement of visible or ultraviolet excitation with non- damaging near infrared light. Further, a comparison of possible excitation sources for TPE indicates that the titanium:sapphire laser is exceptionally well suited for non- linear excitation of PDT agents in biological systems due to its extremely short pulse width and high repetition rate; these features combine to effect efficient PDT activation with minimal potential for non-specific biological damage.

  13. Single metal nanoparticle absorption spectroscopy and optical characterization

    Science.gov (United States)

    Muskens, O. L.; Del Fatti, N.; Vallée, F.; Huntzinger, J. R.; Billaud, P.; Broyer, M.

    2006-02-01

    Optical absorption spectra of small single metal nanoparticles are measured using a far-field technique combining a spatial modulation microscope with a broadband light source. Quantitative determination of the spectral and polarization dependencies of the absorption cross section of individual gold nanoparticles permits precise determination of their geometrical properties in excellent agreement with transmission electron microscopy measurements.

  14. Measurement of Ultra-Short Single-Photon Pulse Duration with Two-Photon Interference

    Institute of Scientific and Technical Information of China (English)

    LV Fan; SUN Fang-Wen; ZOU Chang-Ling; HAN Zheng-Fu; GUO Guang-Can

    2011-01-01

    We proposed a protocol of measuring the duration of ultra-short single-photon pulse with two-photon interference.The pulse duration can be obtained from the width of the visibility of two-photon Hong-Ou-Mandel interference or the indistinguishability of the two photons. Moreover, the shape of a single-photon pulse can be measured with ultra-short single-photon pulses through the two-photon interference.%@@ We proposed a protocol of measuring the duration of ultra-short single-photon pulse with two-photon interference.The pulse duration can be obtained from the width of the visibility of two-photon Hong-Ou-Mandel interference or the indistinguishability of the two photons.Moreover, the shape of a single-photon pulse can be measured with ultra-short single-photon pulses through the two-photon interference.

  15. A bistriphenylamine-substituted spirobifluorene derivative exhibiting excellent nonlinearity/transparency/thermal stability trade-off and strong two-photon induced blue fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Hongyao [Department of Chemistry, Shanghai Normal University, Shanghai 200234 (China); Xiao, Haibo, E-mail: xiaohb@shnu.edu.cn [Department of Chemistry, Shanghai Normal University, Shanghai 200234 (China); Ding, Lei [Department of Chemistry, Shanghai Normal University, Shanghai 200234 (China); Zhang, Chun; Ren, Aiming [State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023 (China); Li, Bo [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200241 (China)

    2015-02-01

    A spirobifluorene-bridged donor/donor chromophore, 2,7-bis-(4-(N,N-diphenylamino)phen-1-yl)-9,9′-spirobifluorene (SPF-TP), was found to combine excellent transparency in the near UV–visible region (λ{sub cut-off} ≤ 420 nm), large two-photon absorption cross-section (4.5 × 10{sup 3}GM) and high thermal stability (T{sub d} = 501 °C). In comparison to the reported two-photon absorption molecules, SPF-TP represents the best thermal stability so far described in the literature. The main electronic factors explaining the high two-photon absorption activities of SPF-TP were analyzed by theoretical calculations. Cyclic voltammograms were employed to explore the causes of the excellent transparency of SPF-TP. It was found that the spiroconjugation effect is responsible for the excellent nonlinearity/transparency/thermal stability trade-off in SPF-TP. In addition, SPF-TP is also a good two-photon induced blue fluorescent material with high fluorescence quantum yield (Φ = 0.90, in THF). - Highlights: • We report a molecule exhibiting excellent transparency. • The two-photon absorption cross-section is as large as 4.5 × 10{sup 3}GM. • The molecule exhibits excellent thermal stability. • The molecule is a good two-photon induced blue fluorescent material. • The spiroconjugation effect explains the excellent properties.

  16. Two-photon photodissociation of H 2O via the B˜ state

    Science.gov (United States)

    Underwood, J.; Wittig, C.

    2004-03-01

    The H 2O B˜← X˜ system has been excited by using 266 nm two-photon absorption, and H-atom products have been probed by using high- n Rydberg time-of-flight spectroscopy. The B˜/ X˜ conical intersection results in the efficient transfer of flux from B˜ to X˜, with dissociation occurring mainly on X˜ . Though the OH(X 2Π) product is highly rotationally excited, this bias is less than that observed at higher energies. The OH(A 2Σ +)/OH(X 2Π) branching ratio is <0.1%, which is significantly smaller than branching ratios obtained at higher excitation energies, and two orders of magnitude less than predicted by theory.

  17. Fully integrated reflection-mode photoacoustic/two-photon microscopy in vivo (Conference Presentation)

    Science.gov (United States)

    Song, Liang; Song, Wei; Zhang, Yang; Zheng, Wei

    2016-03-01

    Using a water-immersion optical objective in conjunction with a miniature 40-MHz ultrasonic transducer, we developed reflection-mode photoacoustic microscopy with a transverse resolution as high as 320 nm. Here, we further integrated two-photon microscopy capability into the system to enable multimodality in vivo biomedical imaging at submicron resolution. As a result, the system is capable of tri-modality label-free imaging of microvasculature, collagen, and cell morphology, based on the contrast of optical absorption, second-harmonic generation, and autofluorescence, respectively. In addition, we demonstrated simultaneous microscopic imaging of neuron and microvasculature in the brain cortex of a living mouse, which may offer new opportunities for studying the mechanisms of neurovascular coupling.

  18. Ultrabroadband ghost imaging exploiting optoelectronic amplified spontaneous emission and two-photon detection.

    Science.gov (United States)

    Hartmann, Sébastien; Molitor, Andreas; Elsäßer, Wolfgang

    2015-12-15

    Ghost imaging (GI) is one of the recent fascinating and probably counterintuitive topics of quantum optics. Here, we present an alternative classical GI scheme using spectrally ultrabroadband amplified spontaneous emission from an optoelectronic quantum dot based superluminescent diode source. This light source exhibits highly incoherent properties regarding both first- and second-order correlations with a 70 nm-wide optical spectrum as well as thermal-like photon statistics. Exploiting a two-photon-absorption detection method, we demonstrate for the first time, to the best of our knowledge, a GI experiment handling the corresponding femtosecond correlation timescales. By introducing compact broadband light sources to GI, this work contributes toward practical application of GI.

  19. Resonant two-photon ionization spectroscopy of Al atoms and dimers solvated in helium nanodroplets

    Energy Technology Data Exchange (ETDEWEB)

    Krasnokutski, Serge A.; Huisken, Friedrich [Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Institute of Solid State Physics, Helmholtzweg 3, D-07743 Jena (Germany)

    2015-02-28

    Resonant two-photon ionization (R2PI) spectroscopy has been applied to investigate the solvation of Al atoms in helium droplets. The R2PI spectra reveal vibrational progressions that can be attributed to Al–He{sub n} vibrations. It is found that small helium droplets have very little chance to pick up an aluminum atom after collision. However, the pick-up probability increases with the size of the helium droplets. The absorption band that is measured by monitoring the ions on the mass of the Al dimer is found to be very little shifted with respect to the Al monomer band (∼400 cm{sup −1}). However, using the same laser wavelength, we were unable to detect any Al{sub n} photoion with n larger than two.

  20. Resonant two-photon ionization spectroscopy of Al atoms and dimers solvated in helium nanodroplets.

    Science.gov (United States)

    Krasnokutski, Serge A; Huisken, Friedrich

    2015-02-28

    Resonant two-photon ionization (R2PI) spectroscopy has been applied to investigate the solvation of Al atoms in helium droplets. The R2PI spectra reveal vibrational progressions that can be attributed to Al-He(n) vibrations. It is found that small helium droplets have very little chance to pick up an aluminum atom after collision. However, the pick-up probability increases with the size of the helium droplets. The absorption band that is measured by monitoring the ions on the mass of the Al dimer is found to be very little shifted with respect to the Al monomer band (∼400 cm(-1)). However, using the same laser wavelength, we were unable to detect any Al(n) photoion with n larger than two.

  1. Clinical multiphoton tomography and clinical two-photon microendoscopy

    Science.gov (United States)

    König, Karsten; Bückle, Rainer; Weinigel, Martin; Elsner, Peter; Kaatz, Martin

    2009-02-01

    We report on applications of high-resolution clinical multiphoton tomography based on the femtosecond laser system DermaInspectTM with its flexible mirror arm in Australia, Asia, and Europe. Applications include early detection of melanoma, in situ tracing of pharmacological and cosmetical compounds including ZnO nanoparticles in the epidermis and upper dermis, the determination of the skin aging index SAAID as well as the study of the effects of anti-aging products. In addition, first clinical studies with novel rigid high-NA two-photon 1.6 mm GRIN microendoscopes have been conducted to study the effect of wound healing in chronic wounds (ulcus ulcera) as well as to perform intrabody imaging with subcellular resolution in small animals.

  2. Two-Photon Micromaser with Initial Atomic Coherence

    Institute of Scientific and Technical Information of China (English)

    SUN Wei-Hui; DU Si-De; CHEN Xiao-Shuang

    2005-01-01

    @@ We investigate the quantum dynamics ora two-photon micromaser pumped by atoms injected in the superpositionstate of the upper and intermediate levels. We simulate a master equation governing the system by the MonteCarlo wavefunction approach and analyse the steady-state behaviour as a function of the atomic transit time.The atomic coherence can effectively enhance the intensity and sub-Poissonian of the cavity field as comparedwith the atomic mixture. It is also discovered that the phase of the cavity field can be shifted by adjusting thedetuning between the atom and field. This result shows that it is possible to manipulate the phase of the cavityfield by detuning, due to atomic coherence.

  3. Two-photon resonant, stimulated processes in krypton and xenon

    Energy Technology Data Exchange (ETDEWEB)

    Miller, J.C.

    1988-11-01

    Both on-axis and conical emissions have been observed following two-photon pumping of the 5p states of krypton and the 6p', 7p, 8p, and 4f states of xenon. In the former case, coherent emissions from the 5p states to the 5s are observed, and in the latter case, many p..-->..s, d..-->..p, and f..-->..d cascade emissions are observed. By analogy to the well-studied alkali and alkaline earth examples, the emissions are discussed in terms of amplified spontaneous emission (ASE), stimulated hyper-Raman scattering, and parametric four-wave mixing. The physical processes responsible for the conical emission and for intensity anomalies in the xenon p..-->..s emissions are not understood at present. Interference effects due to coherent cancellation between competing excitation pathways may be occurring. 4 refs., 3 figs.

  4. Whole brain imaging with Serial Two-Photon Tomography

    Directory of Open Access Journals (Sweden)

    Stephen P Amato

    2016-03-01

    Full Text Available Imaging entire mouse brains at submicron resolution has historically been a challenging undertaking and largely confined to the province of dedicated atlasing initiatives. The has limited systematic investigations into important areas of neuroscience, such as neural circuits, brain mapping and neurodegeneration. In this paper, we describe in detail Serial Two-Photon (STP tomography, a robust, reliable method for imaging entire brains with histological detail. We provide examples of how the basic methodology can be extended to other imaging modalities, such as optical coherence tomography, in order to provide unique contrast mechanisms. Furthermore we provide a survey of the research that STP tomography has enabled in the field of neuroscience, provide examples of how this technology enables quantitative whole brain studies, and discuss the current limitations of STP tomography-based approaches

  5. Two-photon assisted clock comparison to picosecond precision

    CERN Document Server

    Zhang, Shi-Wei; Yao, Yin-Ping; Wan, Ren-Gang; Zhang, Tong-Yi

    2015-01-01

    We have experimentally demonstrated a clock comparison scheme utilizing time-correlated photon pairs generated from the spontaneous parametric down conversion process of a laser pumped beta-barium borate crystal. The coincidence of two-photon events are analyzed by the cross correlation of the two time stamp sequences. Combining the coarse and fine part of the time differences at different resolutions, a 64 ps precision for clock synchronization has been realized. We also investigate the effects of hardware devices used in the system on the precision of clock comparison. The results indicate that the detector's time jitter and the background noise will degrade the system performance. With this method, comparison and synchronization of two remote clocks could be implemented with a precision at the level of a few tens of picoseconds.

  6. Measurement of bottom quark production in two photon collisions

    CERN Document Server

    Saremi, Sepehr

    2001-01-01

    The cross section for bottom quark production in two-photon collisions, sigma( e+e- → e+e- bb¯X), is measured for the first time. The measurement is performed with the L3 detector at the Large Electron Positron (LEP) collider at the European Center for Nuclear and Particle Physics (CERN). The data corresponds to 410 pb-1 taken at center-of-mass energies from 189 GeV to 202 GeV. Hadrons containing a bottom quark are identified by detecting electrons or muons from their semi-leptonic decays. The measured cross section is in excess of the Next to Leading Order QCD prediction by a factor of three.

  7. High contrast two-photon imaging of fingermarks

    Science.gov (United States)

    Stoltzfus, Caleb R.; Rebane, Aleksander

    2016-04-01

    Optically-acquired fingermarks are widely used as evidence across law enforcement agencies as well as in the courts of law. A common technique for visualizing latent fingermarks on nonporous surfaces consists of cyanoacrylate fuming of the fingerprint material, followed by impregnation with a fluorescent dye, which under ultra violet (UV) illumination makes the fingermarks visible and thus accessible for digital recording. However, there exist critical circumstances, when the image quality is compromised due to high background scattering, high auto-fluorescence of the substrate material, or other detrimental photo-physical and photo-chemical effects such as light-induced damage to the sample. Here we present a novel near-infrared (NIR), two-photon induced fluorescence imaging modality, which significantly enhances the quality of the fingermark images, especially when obtained from highly reflective and/or scattering surfaces, while at the same time reducing photo-damage to sensitive forensic samples.

  8. Two-photon transition form factor of c ¯ quarkonia

    Science.gov (United States)

    Chen, Jing; Ding, Minghui; Chang, Lei; Liu, Yu-xin

    2017-01-01

    The two-photon transition of c ¯c quarkonia are studied within a covariant approach based on the consistent truncation scheme of the quantum chromodynamics Dyson-Schwinger equation for the quark propagator and the Bethe-Salpeter equation for the mesons. We find the decay widths of ηc→γ γ and χc 0 ,2→γ γ in good agreement with experimental data. The obtained transition form factor of ηc→γ γ* for a wide range of spacelike photon-momentum-transfer squared is also in agreement with the experimental findings of the BABAR experiment. As a by-product, the decay widths of ηb,χb 0 ,2→γ γ and the transition form factor of ηb,χc 0 ,b 0→γ γ* are predicted, which await experimental testing.

  9. Nuclear two-photon decay in 0 +→0 + transitions

    Science.gov (United States)

    Kramp, J.; Habs, D.; Kroth, R.; Music, M.; Schirmer, J.; Schwalm, D.; Broude, C.

    1987-11-01

    The two-photon decay of the first excited 0 + state of 16O has been measured using the Heidelberg-Darmstadt crystal ball. A branching ratio of {Γ γγ}/{Γ tot} = (6.6±0.5) · 10 -4 was obtained. As in the cases of 40Ca and 90Zr previously reported by us, the 2γ decay of 16O proceeds via double E1 and M1 transitions of similar strength; the evidence is the observed interference term in the 2γ angular correlation. The ratio of the matrix elements {α E1 }/{χ} for 16O was restricted to the two inverse values (-6.2±1.5) or (-0.16±0.04). An interpretation of 2γ matrix elements observed for 16O, 40Ca and 90Zr in terms of the electric polarizabilities and magnetic susceptibility is given leading to a qualitative understanding of this decay mode.

  10. Fluorescent detection and imaging of Hg{sup 2+} using a novel phenanthroline derivative based single- and two-photon excitation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xian, E-mail: zhangx@qlu.edu.cn; Li, Long-long; Liu, Ying-kai

    2016-02-01

    A novel phenanthroline derivative, 4-[4-(N-methyl)styrene]-imidazo[4,5-f][1,10]phenanthroline-benzene iodated salt (MSIPBI), was synthesized, and the linear absorption and fluorescent spectra of MSIPBI in different solvents were investigated. The photophysical properties in unbound and in ligand–metal complexes were evaluated by UV absorption and one- and two-photon fluorescent spectra, and the quantum yields, two-photon active cross-sections and the binding constant of dye–metal were calculated. The results indicated that MSIPBI has a large Stokes shift (more than 167 nm), and the dye was selective and sensitive for the detection of Hg{sup 2+} with a two-photon active cross-section of 55.5 GM in tris–HCl buffer solution at 800 nm. Furthermore, the results of the fluorescence microscopy imaging indicated that MSIPBI is an efficient fluorescent probe for the detection of Hg{sup 2+} in living cells by one- and two-photon excitation. Moreover, the experiments of determination Hg{sup 2+} in river water and tap water were finished. - Highlights: • A novel phenanthroline derivative (MSIPBI) has been synthesized. • The dye of MSIPBI was selective and sensitive to detect Hg{sup 2+}. • MSIPBI has a large Stokes shift (≥ 167 nm). • Hg{sup 2+} in living cells was successfully imaged by one- and two-photon excitation.

  11. Carbon nanodots featuring efficient FRET for two-photon photodynamic cancer therapy with a low fs laser power density.

    Science.gov (United States)

    Wang, Jing; Zhang, Zehui; Zha, Shuai; Zhu, Yinyan; Wu, Peiyi; Ehrenberg, Benjamin; Chen, Ji-Yao

    2014-11-01

    The 5,10,15,20-tetrakis(1-methyl 4-pyridinio) porphyrins (TMPyP), a photosensitizer used for photodynamic therapy of cancers (PDT), were linked to carbon dots (CDots) to form the conjugates of CDot-TMPyP by the electrostatic force. The 415 nm emission band of CDots was well overlapped with the absorption band of TMPyP, so that the Cdots in conjugates can work as donor to transfer the energy to TMPyP moiety by fluorescence resonance energy transfer (FRET) with an FRET efficiency of 45%, determined by the fluorescence lifetime change between the free CDots and conjugated CDots. The two-photon absorption cross section (TPACS) of TMPyP is as low as 110 GM and the TMPyP thus be not suitable for two-photon PDT. Whereas the CDots have high TPACS, and their TPACS are excitation wavelength dependent with the maximum value of 15000 GM at 700 nm. Therefore, the conjugates of CDot-TMPyP were explored for two-photon excitation (TPE) PDT. The two-photon image of CDot-TMPyP in Hela cells was clearly seen under the excitation of a 700 nm femto-second (fs) laser. The singlet oxygen production of CDot-TMPyP was also much higher than that of TMPyP alone under TPE of a 700 nm fs laser. The in vitro PDT killing was further achieved with CDot-TMPyP by TPE of the 700 nm fs laser. Particularly herein the low power density of fs laser from unfocused laser beam was successfully used to carry out the TPE PDT, because of the high TPACS of CDots. These results demonstrate that the CDot-TMPyP conjugates are promising for TPE PDT and needed to investigate further. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Two-Photon Pumped Amplified Spontaneous Emission from Cyano-Substituted Oligo(p-phenylenevinylene) Crystals with Aggregation-Induced Emission Enhancement

    NARCIS (Netherlands)

    Fang, Hong-Hua; Chen, Qi-Dai; Yang, Jie; Xia, Hong; Gao, Bing-Rong; Feng, Jing; Ma, Yu-Guang; Sun, Hong-Bo; Fang, Honghua

    2010-01-01

    We report the effective two-photon absorption-induced upconversion amplified spontaneous emission (ASE) in the cyano-substituted oligo(p-phenylenevinylene) 1,4-bis[1-cyano-2-(4-(diphenylamino)phenyl)vinyl]benzene (TPCNDSB) organic crystals. The material shows enhanced emission in the solid state (31

  13. Linear and nonlinear optical absorption characterization of natural laccaic acid dye

    Science.gov (United States)

    Zongo, S.; Dhlamini, M. S.; Kerasidou, A. P.; Beukes, P.; Sahraoui, B.; Maaza, M.

    2015-09-01

    We report on the optical performances of laccaic acid dye in solution at different concentrations and dye-poly(methyl methacrylate) composite thin films. The linear spectral characteristics including optical constants, i.e. refractive index ( n) and extinction coefficient ( k), were carried out in a comprehensive way through absorbance, fluorescence and ellipsometric studies. The nonlinear optical parameters such as nonlinear absorption coefficient β eff (or β 2), the imaginary third-order susceptibility (Im[ χ (3)]) and the imaginary part of second-order hyperpolarizability ( γ) of the samples were evaluated using the open-aperture Z-scan technique with a laser pulse duration of 10 ns at 532 nm wavelength. The corresponding numerical values of these parameters were of 10-10, 10-11 and 10-32 order, respectively. Two-photon absorption was revealed to be the main driving physical mechanism in the nonlinear response. This suggests that laccaic acid dye can be a potential candidate for NLO materials application.

  14. Fluorescence enhancement of asCP595 is due to consecutive absorbance of two photons

    Science.gov (United States)

    Savitsky, Alexander P.; Agranat, Michail B.; Lukyanov, Konstantin A.; Schuttrigkeit, Tanja; von Feilitzsch, Till; Kompa, Christian; Michel-Beyerle, Maria-Elisabeth

    2004-06-01

    Colored proteins are widely used as gene markers in biotechnology. Chromophores result from autocatalytic posttranslational reactions involving several amino acids. The protein asCP595 was isolated for the first time from the coral as a weakly fluorescent chromoprotein with a fluorescence maximum at 595 nm. Strong illumination in the blue wing of the low energy absorption band results in a superlinear increase of the fluorescence yield and shifts its fluorescence spectrum by about 10 nm to the red. Time resolved fluorescence measurements using excitation pulses with 10 ps duration revealed a multiexponential decay pattern with time constants in the range from 20 ps to 2.1 ns. The ratio of amplitudes related to the different time constants depends on the intensity of illumination favoring the ns component at high intensities. Transient absorption measurements using ultrashort excitation pulses (150 fs, 1 kHz repetition rate) did not reveal excited states with nanosecond lifetimes as observed in fluorescence upon excitation using 10 ps pulses. This observation leads to the notion that within 10 ps a second photon is absorbed by a state not yet populated within 150 fs. As a consequence we propose two different excited singlet states operative in asCP595, one with low fluorescence quantum yield peaking at 595 nm and one with high fluorescence quantum yield peaking at 605 nm which is populated via the consecutive absorption of two photons at high excitation intensities.

  15. Multidimensional two-photon imaging and spectroscopy of fresh human bladder biopsies

    Science.gov (United States)

    Cicchi, Riccardo; Crisci, Alfonso; Cosci, Alessandro; Nesi, Gabriella; Giancane, Saverio; Carini, Marco; Pavone, Francesco S.

    2010-02-01

    Two-photon microscopy has been successfully used to image several types of tissues, including skin, muscles, tendons. Nevertheless, its usefulness in imaging bladder tissue has not been investigated yet. In this work we used combined twophoton excited fluorescence, second-harmonic generation microscopy, fluorescence lifetime imaging microscopy, and multispectral two-photon emission detection to investigate different kinds of human ex-vivo fresh biopsies of bladder. Morphological and spectroscopic analyses allowed to characterize both healthy mucosa and carcinoma in-situ samples in a good agreement with common routine histology. Cancer cells showed different morphology with respect to the corresponding healthy cells: they appeared more elongated and with a larger nucleus to cytoplasm ratio. From the spectroscopic point of view, differences between the two tissue types in both spectral emission and fluorescence lifetime distribution were found. Even if further analysis, as well as a more significant statistics on a larger number of samples would be helpful to discriminate between low, mild, and high grade cancer, our method is a promising tool to be used as diagnostic confirmation of histological results, as well to be implemented in a multi-photon endoscope or in a spectroscopic for in in-vivo imaging applications.

  16. Two photon fluorescence imaging of lipid membrane domains and potentials using advanced fluorescent probes

    Science.gov (United States)

    Kilin, Vasyl; Darwich, Zeinab; Richert, Ludovic; Didier, Pascal; Klymchenko, Andrey; Mély, Yves

    2013-02-01

    Biomembranes are ordered and dynamic nanoscale structures critical for cell functions. The biological functions of the membranes strongly depend on their physicochemical properties, such as electrostatics, phase state, viscosity, polarity and hydration. These properties are essential for the membrane structure and the proper folding and function of membrane proteins. To monitor these properties, fluorescence techniques and notably, two-photon microscopy appear highly suited due to their exquisite sensitivity and their capability to operate in complex biological systems, such as living cells and tissues. In this context, we have developed multiparametric environment-sensitive fluorescent probes tailored for precise location in the membrane bilayer. We notably developed probes of the 3-hydroxychromone family, characterized by an excited state intramolecular proton transfer reaction, which generates two tautomeric emissive species with well-separated emission bands. As a consequence, the response of these probes to changes in their environment could be monitored through changes in the ratios of the two bands, as well as through changes in the fluorescence lifetimes. Using two-photon ratiometric imaging and FLIM, these probes were used to monitor the surface membrane potential, and were applied to detect apoptotic cells and image membrane domains.

  17. Two-Photon Ghost Image and Interference-Diffraction

    Science.gov (United States)

    Shih, Y. H.; Sergienko, A. V.; Pittman, T. B.; Strekalov, D. V.; Klyshko, D. N.

    1996-01-01

    One of the most surprising consequences of quantum mechanics is entanglement of two or more distance particles. The two-particle entangled state was mathematically formulated by Schrodinger. Based on this unusual quantum behavior, EPR defined their 'physical reality' and then asked the question: 'Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?' One may not appreciate EPR's criterion of physical reality and insist that 'no elementary quantum phenomenon is a phenomenon until it is a recorded phenomenon'. Optical spontaneous parametric down conversion (SPDC) is the most effective mechanism to generate an EPR type entangled two-photon state. In SPDC, an optical beam, called the pump, is incident on a birefringent crystal. The pump is intense enough so that nonlinear effects lead to the conversion of pump photons into pairs of photons, historically called signal and idler. Technically, the SPDC is said to be type-1 or type-2, depending on whether the signal and idler beams have parallel or orthogonal polarization. The SPDC conversion efficiency is typically on the order of 10(exp -9) to 10(exp -11), depending on the SPDC nonlinear material. The signal and idler intensities are extremely low, only single photon detection devices can register them. The quantum entanglement nature of SPDC has been demonstrated in EPR-Bohm experiments and Bell's inequality measurements. The following two experiments were recently performed in our laboratory, which are more closely related to the original 1935 EPR gedankenezperiment. The first experiment is a two-photon optical imaging type experiment, which has been named 'ghost image' by the physics community. The signal and idler beams of SPDC are sent in different directions, so that the detection of the signal and idler photons can be performed by two distant photon counting detectors. An aperture object (mask) is placed in front of the signal photon detector and illuminated by the signal beam through a

  18. Two-dimensional imaging of molecular hydrogen in H2-air diffusion flames using two-photon laser-induced fluorescence

    Science.gov (United States)

    Lempert, W.; Kumar, V.; Glesk, I.; Miles, R.; Diskin, G.

    1991-01-01

    The use of a tunable ArF laser at 193.26 nm to record simultaneous single-laser-shot, planar images of molecular hydrogen and hot oxygen in a turbulent H2-air diffusion flame. Excitation spectra of fuel and oxidant-rich flame zones confirm a partial overlap of the two-photon H2 and single-photon O2 Schumann-Runge absorption bands. UV Rayleigh scattering images of flame structure and estimated detection limits for the H2 two-photon imaging are also presented.

  19. Peptide backbone orientation and dynamics in spider dragline silk and two-photon excitation in nuclear magnetic and quadrupole resonance

    Energy Technology Data Exchange (ETDEWEB)

    Eles, P.T

    2005-07-01

    In the first part of the dissertation, spider dragline silk is studied by solid state NMR techniques. The dependence of NMR frequency on molecular orientation is exploited using the DECODER experiment to determine the orientation of the protein backbone within the silk fibre. Practical experimental considerations require that the silk fibres be wound about a cylindrical axis perpendicular to the external magnetic field, complicating the reconstruction of the underlying orientation distribution and necessitating the development of numerical techniques for this purpose. A two-component model of silk incorporating static b-sheets and polyglycine II helices adequately fits the NMR data and suggests that the b-sheets are well aligned along the silk axis (20 FWHM) while the helices are poorly aligned (68 FWHM). The effects of fibre strain, draw rate and hydration on orientation are measured. Measurements of the time-scale for peptide backbone motion indicate that when wet, a strain-dependent fraction of the poorly aligned component becomes mobile. This suggests a mechanism for the supercontraction of silk involving latent entropic springs that undergo a local strain-dependent phase transition, driving supercontraction. In the second part of this dissertation a novel method is developed for exciting NMR and nuclear quadrupole resonance (NQR) by rf irradiation at multiple frequencies that sum to (or differ by) the resonance frequency. This is fundamentally different than traditional NMR experiments where irradiation is applied on-resonance. With excitation outside the detection bandwidth, two-photon excitation allows for detection of free induction signals during excitation, completely eliminating receiver dead-time. A theoretical approach to describing two-photon excitation is developed based on average Hamiltonian theory. An intuition for two-photon excitation is gained by analogy to the coherent absorption of multiple photons requiring conservation of total energy and

  20. Two-photon polymerization for fabrication of biomedical devices

    Science.gov (United States)

    Ovsianikov, Aleksandr; Doraiswamy, Anand; Narayan, R.; Chichkov, B. N.

    2007-01-01

    Two-photon polymerization (2PP) is a novel technology which allows the fabrication of complex three-dimensional (3D) microstructures and nanostructures. The number of applications of this technology is rapidly increasing; it includes the fabrication of 3D photonic crystals [1-4], medical devices, and tissue scaffolds [5-6]. In this contribution, we discuss current applications of 2PP for microstructuring of biomedical devices used in drug delivery. While in general this sector is still dominated by oral administration of drugs, precise dosing, safety, and convenience are being addressed by transdermal drug delivery systems. Currently, main limitations arise from low permeability of the skin. As a result, only few types of pharmacological substances can be delivered in this manner [7]. Application of microneedle arrays, whose function is to help overcome the barrier presented by the epidermis layer of the skin, provides a very promising solution. Using 2PP we have fabricated arrays of hollow microneedles with different geometries. The effect of microneedle geometry on skin penetration is examined. Our results indicate that microneedles created using 2PP technique are suitable for in vivo use, and for integration with the next generation of MEMS- and NEMS-based drug delivery devices.

  1. Review of two-photon exchange in electron scattering

    Energy Technology Data Exchange (ETDEWEB)

    J. Arrington, P. G. Blunden, W. Melnitchouk

    2011-10-01

    We review the role of two-photon exchange (TPE) in electron-hadron scattering, focusing in particular on hadronic frameworks suitable for describing the low and moderate Q^2 region relevant to most experimental studies. We discuss the effects of TPE on the extraction of nucleon form factors and their role in the resolution of the proton electric to magnetic form factor ratio puzzle. The implications of TPE on various other observables, including neutron form factors, electroproduction of resonances and pions, and nuclear form factors, are summarized. Measurements seeking to directly identify TPE effects, such as through the angular dependence of polarization measurements, nonlinear epsilon contributions to the cross sections, and via e+p to e-p cross section ratios, are also outlined. In the weak sector, we describe the role of TPE and gamma-Z interference in parity-violating electron scattering, and assess their impact on the extraction of the strange form factors of the nucleon and the weak charge of the proton.

  2. Higgs decay into two photons in a warped extra dimension

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, Juliane; Hoerner, Clara; Malm, Raoul; Novotny, Kristiane; Schmell, Christoph [Johannes Gutenberg University, PRISMA Cluster of Excellence and Mainz Institute for Theoretical Physics, Mainz (Germany); Neubert, Matthias [Johannes Gutenberg University, PRISMA Cluster of Excellence and Mainz Institute for Theoretical Physics, Mainz (Germany); Cornell University, Department of Physics, LEPP, Ithaca, NY (United States)

    2014-05-15

    A detailed five-dimensional calculation of the Higgs-boson decay into two photons is performed in both the minimal and the custodially protected Randall-Sundrum (RS) model, where the Standard Model (SM) fields propagate in the bulk and the scalar sector lives on or near the IR brane. It is explicitly shown that the R{sub ξ} gauge invariance of the sum of diagrams involving bosonic fields in the SM also applies to the case of these RS scenarios. An exact expression for the h → γγ amplitude in terms of the five-dimensional (5D) gauge-boson and fermion propagators is presented, which includes the full dependence on the Higgs-boson mass. Closed expressions for the 5D W-boson propagators in theminimal and the custodial RS model are derived, which are valid to all orders in v{sup 2}/M{sup 2}{sub KK}. In contrast to the fermion case, the result for the bosonic contributions to the h → γγ amplitude is insensitive to the details of the localization of the Higgs profile on or near the IR brane. The various RS predictions for the rate of the pp → h → γγ process are compared with the latest LHC data, and exclusion regions for the RS model parameters are derived. (orig.)

  3. Two-photon excited photoconversion of cyanine-based dyes

    Science.gov (United States)

    Kwok, Sheldon J. J.; Choi, Myunghwan; Bhayana, Brijesh; Zhang, Xueli; Ran, Chongzhao; Yun, Seok-Hyun

    2016-03-01

    The advent of phototransformable fluorescent proteins has led to significant advances in optical imaging, including the unambiguous tracking of cells over large spatiotemporal scales. However, these proteins typically require activating light in the UV-blue spectrum, which limits their in vivo applicability due to poor light penetration and associated phototoxicity on cells and tissue. We report that cyanine-based, organic dyes can be efficiently photoconverted by nonlinear excitation at the near infrared (NIR) window. Photoconversion likely involves singlet-oxygen mediated photochemical cleavage, yielding blue-shifted fluorescent products. Using SYTO62, a biocompatible and cell-permeable dye, we demonstrate photoconversion in a variety of cell lines, including depth-resolved labeling of cells in 3D culture. Two-photon photoconversion of cyanine-based dyes offer several advantages over existing photoconvertible proteins, including use of minimally toxic NIR light, labeling without need for genetic intervention, rapid kinetics, remote subsurface targeting, and long persistence of photoconverted signal. These findings are expected to be useful for applications involving rapid labeling of cells deep in tissue.

  4. Two-Photon-Exchange Effects and $\\Delta(1232)$ Deformation

    CERN Document Server

    Zhou, Hai-Qing

    2016-01-01

    The two-photon-exchange (TPE) contribution in $ep\\rightarrow ep\\pi ^0$ with $W=M_{\\Delta}$ and small $Q^2$ is calculated and its corrections to the ratios of electromagnetic transition form factors $R_{EM} = E_{1+}^{(3/2)}/M_{1+}^{(3/2)} $ and $R_{SM} = S_{1+}^{(3/2)}/M_{1+}^{(3/2)}$, are analysed. A simple hadronic model is used to estimate the TPE amplitude. Two phenomenological models, MAID2007 and SAID, are used to approximate the full $ep\\rightarrow ep\\pi ^0$ cross sections which contain both the TPE and the one-photon-exchange (OPE) contributions. The genuine the OPE amplitude is then extracted from an integral equation by iteration. We find that the TPE contribution is not sensitive to whether MAID or SAID is used as input in the region with $Q^2<2$ GeV$^2$. It gives small correction to $R_{EM}$ while for $R_{SM}$, the correction is about -10\\% at small $\\epsilon$ and about $1\\%$ at large $\\epsilon$ for $Q^2\\approx2.5$ GeV$^2$. The large correction from TPE at small $\\epsilon$ must be included in th...

  5. Time-resolved two-photon photoemission from metal surfaces

    CERN Document Server

    Weinelt, M

    2002-01-01

    The Rydberg-like series of image-potential states is a prototype system for loosely bound electrons at a metal surface. The electronic structure and the femtosecond dynamics of these states is studied by high-resolution energy-and time-resolved two-photon photoemission spectroscopy. The electron trapped in the image potential moves virtually freely laterally to the surface where it is subject to inelastic and quasielastic scattering processes which cause decay of population and phase relaxation. The influence of surface corrugation on these processes has been investigated for adsorbates on Cu(001) and stepped Cu(117) and Cu(119) surfaces which are vicinal to Cu(001). The dynamics depend on both the distance of the electron in front of the surface and the parallel momentum. For CO molecules on Cu(001) inelastic scattering into bulk states and adsorbate-induced resonances determine the decay rate. For small numbers of Cu adatoms on Cu(001) and the vicinal surfaces the decay rate of image-potential states is sig...

  6. Two-photon holographic optogenetics of neural circuits (Conference Presentation)

    Science.gov (United States)

    Yang, Weijian; Carrillo-Reid, Luis; Peterka, Darcy S.; Yuste, Rafael

    2016-03-01

    Optical manipulation of in vivo neural circuits with cellular resolution could be important for understanding cortical function. Despite recent progress, simultaneous optogenetic activation with cellular precision has either been limited to 2D planes, or a very small numbers of neurons over a limited volume. Here we demonstrate a novel paradigm for simultaneous 3D activation using a low repetition rate pulse-amplified fiber laser system and a spatial light modulator (SLM) to project 3D holographic excitation patterns on the cortex of mice in vivo for targeted volumetric 3D photoactivation. This method is compatible with two-photon imaging, and enables the simultaneous activation of multiple cells in 3D, using red-shifted opsins, such as C1V1 or ReaChR, while simultaneously imaging GFP-based sensors such as GCaMP6. This all-optical imaging and 3D manipulation approach achieves simultaneous reading and writing of cortical activity, and should be a powerful tool for the study of neuronal circuits.

  7. Precision atomic beam density characterization by diode laser absorption spectroscopy

    Science.gov (United States)

    Oxley, Paul; Wihbey, Joseph

    2016-09-01

    We provide experimental and theoretical details of a simple technique to determine absolute line-of-sight integrated atomic beam densities based on resonant laser absorption. In our experiments, a thermal lithium beam is chopped on and off while the frequency of a laser crossing the beam at right angles is scanned slowly across the resonance transition. A lock-in amplifier detects the laser absorption signal at the chop frequency from which the atomic density is determined. The accuracy of our experimental method is confirmed using the related technique of wavelength modulation spectroscopy. For beams which absorb of order 1% of the incident laser light, our measurements allow the beam density to be determined to an accuracy better than 5% and with a precision of 3% on a time scale of order 1 s. Fractional absorptions of order 10-5 are detectable on a one-minute time scale when we employ a double laser beam technique which limits laser intensity noise. For a lithium beam with a thickness of 9 mm, we have measured atomic densities as low as 5 × 104 atoms cm-3. The simplicity of our technique and the details we provide should allow our method to be easily implemented in most atomic or molecular beam apparatuses.

  8. Tracking of mercury ions in living cells with a fluorescent chemodosimeter under single- or two-photon excitation

    Energy Technology Data Exchange (ETDEWEB)

    Lu Zhoujun [State Key Lab for Advanced Photonic Materials and Devices, Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Wang Peinan [State Key Lab for Advanced Photonic Materials and Devices, Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China)], E-mail: pnwang@fudan.edu.cn; Zhang Yu [State Key Lab for Advanced Photonic Materials and Devices, Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Chen Jiyao; Zhen Shen [Department of Physics, Fudan University, Shanghai 200433 (China); Leng Bing; Tian He [Labs for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237 (China)

    2007-08-10

    Tracking of Hg{sup 2+} in solutions as well as in living cells was conducted with a fluorescent chemodosimeter by measuring the spectral shift of its fluorescence under single- or two-photon excitation. The spectral hypsochromic shifts of this chemodosimeter when reacting with Hg{sup 2+} were found to be about 50 nm in acetonitrile/water solutions and 32 nm in Euglena gracilis 277 living cells. This chemodosimeter shows high sensitivity and selectivity, and is not influenced by the pH values. It can signal Hg{sup 2+} in solutions down to the ppb range under either single-photon excitation (SPE) at 405 nm or two-photon excitation (TPE) at 800 nm. However, with low cellular chemodosimeter concentrations, the SPE spectra were disturbed by the auto-fluorescence from the native fluorophore in the cell, while the TPE spectra were still of high quality since the two-photon absorption cross section of this chemodosimeter is much larger than that of the native fluorophores in the cell.

  9. Effect of the coherent cancellation of the two-photon resonance on the generation of vacuum ultraviolet light by two-photon reasonantly enhanced four-wave mixing

    Energy Technology Data Exchange (ETDEWEB)

    Payne, M.G.; Garrett, W.R.; Judish, J.P.; Wunderlich, R.

    1988-11-01

    Many of the most impressive demonstrations of the efficient generation of vacuum ultraviolet (VUV) light have made use of two- photon resonantly enhanced four-wave mixing to generate light at ..omega../sub VUV/ = 2..omega../sub L1/ +- ..omega../sub L2/. The two-photon resonance state is coupled to the ground state both by two photons from the first laser, or by a photon from the second laser and one from the generated VUV beam. We show here that these two coherent pathways destructively interfere once the second laser is made sufficiently intense, thereby leading to an important limiting effect on the achievable conversion efficiency. 4 refs.

  10. Emission turn-on and solubility turn-off in conjugated polymers: one- and two-photon-induced removal of fluorescence-quenching solubilizing groups.

    Science.gov (United States)

    Schelkle, Korwin M; Becht, Steffy; Faraji, Shirin; Petzoldt, Martin; Müllen, Klaus; Buckup, Tiago; Dreuw, Andreas; Motzkus, Marcus; Hamburger, Manuel

    2015-01-01

    The synthesis of highly efficient two-photon uncaging groups and their potential use in functional conjugated polymers for post-polymerization modification are reported. Careful structural design of the employed nitrophenethyl caging groups allows to efficiently induce bond scission by a two-photon process through a combination of exceptionally high two-photon absorption cross-sections and high reaction quantum yields. Furthermore, π-conjugated polyfluorenes are functionalized with these photocleavable side groups and it is possible to alter their emission properties and solubility behavior by simple light irradiation. Cleavage of side groups leads to a turn-on of the fluorescence while solubility of the π-conjugated materials is drastically reduced.

  11. Two-photon excitation with pico-second fluorescence lifetime imaging to detect nuclear association of flavanols.

    Science.gov (United States)

    Mueller-Harvey, Irene; Feucht, Walter; Polster, Juergen; Trnková, Lucie; Burgos, Pierre; Parker, Anthony W; Botchway, Stanley W

    2012-03-16

    Two-photon excitation enabled for the first time the observation and measurement of excited state fluorescence lifetimes from three flavanols in solution, which were ~1.0 ns for catechin and epicatechin, but <45 ps for epigallocatechin gallate (EGCG). The shorter lifetime for EGCG is in line with a lower fluorescence quantum yield of 0.003 compared to catechin (0.015) and epicatechin (0.018). In vivo experiments with onion cells demonstrated that tryptophan and quercetin, which tend to be major contributors of background fluorescence in plant cells, have sufficiently low cross sections for two-photon excitation at 630 nm and therefore do not interfere with detection of externally added or endogenous flavanols in Allium cepa or Taxus baccata cells. Applying two-photon excitation to flavanols enabled 3-D fluorescence lifetime imaging microscopy and showed that added EGCG penetrated the whole nucleus of onion cells. Interestingly, EGCG and catechin showed different lifetime behaviour when bound to the nucleus: EGCG lifetime increased from <45 to 200 ps, whilst catechin lifetime decreased from 1.0 ns to 500 ps. Semi-quantitative measurements revealed that the relative ratios of EGCG concentrations in nucleoli associated vesicles: nucleus: cytoplasm were ca. 100:10:1. Solution experiments with catechin, epicatechin and histone proteins provided preliminary evidence, via the appearance of a second lifetime (τ(2)=1.9-3.1 ns), that both flavanols may be interacting with histone proteins. We conclude that there is significant nuclear absorption of flavanols. This advanced imaging using two-photon excitation and biophysical techniques described here will prove valuable for probing the intracellular trafficking and functions of flavanols, such as EGCG, which is the major flavanol of green tea.

  12. New design strategy for the two-photon active material based on push-pull substituted bisanthene molecule.

    Science.gov (United States)

    Chattopadhyaya, Mausumi; Alam, Md Mehboob; Chakrabarti, Swapan

    2011-03-31

    In the present work, we have critically examined the origin of strong two-photon transition probability of a donor-acceptor substituted bisanthene molecule that imitates a small piece of edge passivated (4, 4) graphene nanoribbon. In our calculations, we have considered -OMe, and -NH(2) as donors and -NO(2) as an acceptor. The one- and two-photon absorption parameters are evaluated using state-of-the-art linear and quadratic response theory, respectively, and all these calculations are carried out within the framework of time dependent density functional theory. To give a proper judgment on our findings, we have used the long-range corrected CAMB3LYP functional for all of the time dependent calculations. The present investigation reveals that the bisanthene molecule with three pairs of donor/acceptor moiety has a lower two-photon transition probability than that of a suitably designed bisanthene with only a single pair of donor/acceptor moiety. This in silico observation is consistent for all of the donor/acceptor moieties chosen in the present work. A comprehensive analysis at the two state model level of theory clearly offers us a verdict that by placing the donor/acceptor moiety in a suitable position of bisanthene, we can create a significant asymmetry in the electron density in the first excited state, which eventually leads to a significant difference in the ground and excited state dipole moment and is attributed to the higher two-photon transition probability of a particular bisanthene with a single pair of donor/acceptor moiety than bisanthene with three pairs of donor/acceptor.

  13. Nanofluid optical property characterization: towards efficient direct absorption solar collectors.

    Science.gov (United States)

    Taylor, Robert A; Phelan, Patrick E; Otanicar, Todd P; Adrian, Ronald; Prasher, Ravi

    2011-03-15

    Suspensions of nanoparticles (i.e., particles with diameters nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.

  14. Nanofluid optical property characterization: towards efficient direct absorption solar collectors

    Directory of Open Access Journals (Sweden)

    Otanicar Todd

    2011-01-01

    Full Text Available Abstract Suspensions of nanoparticles (i.e., particles with diameters < 100 nm in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm. A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power increase.

  15. Nanofluid optical property characterization: towards efficient direct absorption solar collectors

    Science.gov (United States)

    Taylor, Robert A.; Phelan, Patrick E.; Otanicar, Todd P.; Adrian, Ronald; Prasher, Ravi

    2011-12-01

    Suspensions of nanoparticles (i.e., particles with diameters nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.

  16. Galaxies in the Early Universe characterized in absorption and emission

    CERN Document Server

    Krogager, Jens-Kristian

    2016-01-01

    Understanding how galaxies evolved from the early Universe through cosmic time is a fundamental part of modern astrophysics. In order to study this evolution it is important to sample the galaxies at various times in a consistent way through time. In regular luminosity selected samples, our analyses are biased towards the brightest galaxies at all times (as these are easier to observe and identify). A complementary method relies on the absorption imprint from neutral gas in galaxies, the so-called damped Ly-alpha absorbers (DLAs) seen towards distant bright objects. This thesis seeks to understand how the absorption selected galaxies relate to the emission selected galaxies by identifying the faint glow from the absorbing galaxies at redshift z~2. In the last Chapter, a study of the more evolved, massive galaxies is presented. These galaxies are observed to be a factor of 2 to 6 times smaller than local galaxies of similar masses. A new spectroscopically selected sample is presented and the increased precisio...

  17. Determining the Quark Charges by One and Two Photon Processes.

    Science.gov (United States)

    Janah, Arjun

    1982-05-01

    Testable predictions are presented, which may be used to decide between the gauge theories of integer and fractionally charged quarks (icq and fcq). Two distinctive features of icq are exploited, namely (a) presence of color non-singlet components in weak and electromagnetic currents and (b) possible liberation of color non-singlet states above a threshold energy. Consequences are sought in lepton-hadron interaction processes, taking into account the known "color-suppression" effect. Single photon/weak-boson processes such as (nu)N (--->) (nu)X distinguish between icq and fcq only above color-threshold. Experimental consequences of color-liberation in the above process are obtained. It is found that the gluon-parton contribution survives color-suppression to produce a significant rise in the structure functions when color-threshold is exceeded. Two-photon processes such as e('+)e('-) (--->) e('+)e('-) + 2 jets distinguish between the two theories even below color threshold. To obtain the icq predictions for this process, one must take into account (a) the (momentum -dependent) color suppression and (b) the added contribution from pair production of charged gluons. This is done, and it is observed that: (i) in icq, the ratio R('(gamma)(gamma)(2 jet)) is not simply a number given by the quark charges; it depends on the gluon mass, on kinematics and on the particular differential cross-section considered; (ii) the deviation of icq cross-sections from the fcq values depends crucially on whether one includes "untagged" events; if this is done, the deviation is large; the charged gluon contribution is mainly responsible for this deviation; the quark contribution is smaller than naively expected. Finally, comparison is made with experimental data on e('+)e('-) (--->) e('+)e('-) + 2 jets. Here, icq is found to be in better agreement than fcq, for a broad range of gluon masses. A suitably modified equivalent photon approximation is employed.

  18. A Two- Photon Femtosecond Laser System for Three-Dimensional Microfabrication and Data Storage

    Institute of Scientific and Technical Information of China (English)

    蒋中伟; 周拥军; 袁大军; 黄文浩; 夏安东

    2003-01-01

    Utilizing the well-focused femtosecond laser with extreme high pulse intensity, we built a two-photon microfabrication and data storage system, which was introduced through several functional parts. Based on this homemade system, several three-dimensional microstructures were fabricated by two-photon polymerization, and three-dimensional data storage of six-layers was achieved by two-photon excitation with a photochromic material.

  19. Two-photon path-entangled states in multi-mode waveguides

    CERN Document Server

    Poem, Eilon; Silberberg, Yaron

    2012-01-01

    We experimentally show that two-photon path-entangled states can be coherently manipulated by multi-mode interference in multi-mode waveguides. By measuring the output two-photon spatial correlation function versus the phase of the input state, we show that multi-mode waveguides perform as nearly-ideal multi-port beam splitters at the quantum level, creating a large variety of entangled and separable multi-path two-photon states.

  20. Two-photon approximation in the theory of the electron recombination in hydrogen

    OpenAIRE

    Solovyev, D.; Labzowsky, L.

    2010-01-01

    A rigorous QED theory of the multiphoton decay of excited states in hydrogen atom is presented. The "two-photon" approximation is formulated which is limited by the one-photon and two-photon transitions including cascades transitions with two-photon links. This may be helpful for the strict description of the recombination process in hydrogen atom and, in principle, for the history of the hydrogen recombination in the early Universe.

  1. Coherent blue emission generated by Rb two-photon excitation using diode and femtosecond lasers

    Science.gov (United States)

    Lopez, Jesus P.; Moreno, Marco P.; de Miranda, Marcio H. G.; Vianna, Sandra S.

    2017-04-01

    The coherent blue light generated in rubidium vapor due to the combined action of an ultrashort pulse train and a continuous wave diode laser is investigated. Each step of the two-photon transition 5S-5P{}3/2-5D is excited by one of the lasers, and the induced coherence between the 5S and 6P{}3/2 states is responsible for generating the blue beam. Measurements of the excitation spectrum reveal the frequency comb structure and allow us to identify the resonant modes responsible for inducing the nonlinear process. Further, each resonant mode excites a different group of atoms, making the process selective in atomic velocity. The signal dependency on the atomic density is characterized by a sharp growth and a rapid saturation. We also show that for high intensity of the diode laser, the Stark shift at resonance causes the signal suppression observed at low atomic density.

  2. Controlling and tracking of colloidal nanostructures through two-photon fluorescence

    Science.gov (United States)

    Mondal, Dipankar; Goswami, Debabrata

    2016-12-01

    Multiphoton absorbing dye-coated trapped spherical bead at the focal plane of femtosecond optical tweezers shows nonlinear optical (NLO) phenomena. One such NLO process of two-photon fluorescence (TPF) has been used for the background-free imaging of a femtosecond laser-trapping event. Due to the high peak powers of femtosecond laser pulses with low average powers, it is possible to not only trap single nanospheres, but encourage optically directed self-assembly. The TPF signatures of trapped particles show evidence of such a directed self-assembly process which, in turn, can provide information about the structural dynamics during the process of cluster formation. We are able to trap and characterize structure and dynamics in 3D until pentamer formation from the decay characteristics of trapping at the focal plane.

  3. Description of the states of two-photon interference in an optical gating Michelson interferometer

    Science.gov (United States)

    Pongophas, Ekkarat; Sriklin, Watthana; Sinsarp, Asawin; Suwanna, Sujin; Chunwachirasiri, Withoon; Singhsomroje, Wisit

    2016-01-01

    We investigate the interference of two photons in an optical gating Michelson interferometer. The phenomenon is studied using two different representations of photons: the space-time domain and a step-by-step two-photon state evolution. Both representations lead to identical results. The evolution analysis describes the result by the interference of four two-photon traveling states, whereas the space-time domain analysis reveals that the classical interference of the high-intensity light source is identical to two-photon interference in the quantum regime, except for a multiplicative factor of (n2), where n is the number of photons.

  4. Two-photon induced photoluminescence and singlet oxygen generation from aggregated gold nanoparticles.

    Science.gov (United States)

    Jiang, Cuifeng; Zhao, Tingting; Yuan, Peiyan; Gao, Nengyue; Pan, Yanlin; Guan, Zhenping; Zhou, Na; Xu, Qing-Hua

    2013-06-12

    Metal nanoparticles have potential applications as bioimaging and photosensitizing agents. Aggregation effects are generally believed to be adverse to their biomedical applications. Here we have studied the aggregation effects on two-photon induced photoluminescence and singlet oxygen generation of Au nanospheres and Au nanorods of two different aspect ratios. Aggregated Au nanospheres and short Au nanorods were found to display enhanced two-photon induced photoluminescence and singlet oxygen generation capabilities compared to the unaggregated ones. The two-photon photoluminescence of Au nanospheres and short Au nanorods were enhanced by up to 15.0- and 2.0-fold upon aggregation, and the corresponding two-photon induced singlet oxygen generation capabilities were enhanced by 8.3 and 1.8-fold, respectively. The two-photon induced photoluminescence and singlet oxygen generation of the aggregated long Au nanorods were found to be lower than the unaggregated ones. These results support that the change in their two-photon induced photoluminescence and singlet oxygen generation originate from aggregation modulated two-photon excitation efficiency. This finding is expected to foster more biomedical applications of metal nanoparticles as Au nanoparticles normally exist in an aggregated form in the biological environments. Considering their excellent biocompatibility, high inertness, ready conjugation, and easy preparation, Au nanoparticles are expected to find more applications in two-photon imaging and two-photon photodynamic therapy.

  5. Time-reversed two-photon interferometry for phase super-resolution

    CERN Document Server

    Ogawa, Kazuhisa; Kobayashi, Hirokazu; Nakanishi, Toshihiro; Kitano, Masao

    2013-01-01

    We observed two-photon phase super-resolution in an unbalanced Michelson interferometer with classical Gaussian laser pulses. Our work is a time-reversed version of a two-photon interference experiment using an unbalanced Michelson interferometer. A measured interferogram exhibits two-photon phase super-resolution with a high visibility of 97.9% \\pm 0.4%. Its coherence length is about 22 times longer than that of the input laser pulses. It is a classical analogue to the large difference between the one- and two-photon coherence lengths of entangled photon pairs.

  6. Novel Bis-β-diketone-type Ligand and Its Copper and Zinc Complexes for Two-photon Biological Imaging

    Institute of Scientific and Technical Information of China (English)

    ZHOU Shuang-sheng; XUE Xuan; WEI Dong; JIANG Bo; WANG Jia-feng; LU Cheng-hua

    2012-01-01

    A curcumin derivative ligand,1,7-bis(3-methoxyl-4-oxyethylacetate)phenyl-1,6-heptadiene-3,5-diketone (diethyl acetatecurcumin,abbreviated as HL),and its Cu(Ⅱ) and Zn(Ⅱ) complexes have been synthesized and characterized by elemental analyses,infrared(IR),1H NMR and molar conductivity.The experimental results show that the resulting complexes bear strong two-photon excited fluorescence(TPEF) in N,N-dimethyformamide solvent,which has been proven to be potentially useful for two-photon microscopy imaging in living cells.In addition,cytotoxicity tests show that the low-micromolar concentrations of metal-ligand complex(ML2) did not cause significant reduction in cell viability over a pcriod of,at least,24 h and should be safe for further biological studies.

  7. Two-photon excited fluorescence of intrinsic fluorophores enables label-free assessment of adipose tissue function

    Science.gov (United States)

    Alonzo, Carlo Amadeo; Karaliota, Sevasti; Pouli, Dimitra; Liu, Zhiyi; Karalis, Katia P.; Georgakoudi, Irene

    2016-08-01

    Current methods for evaluating adipose tissue function are destructive or have low spatial resolution. These limit our ability to assess dynamic changes and heterogeneous responses that occur in healthy or diseased subjects, or during treatment. Here, we demonstrate that intrinsic two-photon excited fluorescence enables functional imaging of adipocyte metabolism with subcellular resolution. Steady-state and time-resolved fluorescence from intracellular metabolic co-factors and lipid droplets can distinguish the functional states of excised white, brown, and cold-induced beige fat. Similar optical changes are identified when white and brown fat are assessed in vivo. Therefore, these studies establish the potential of non-invasive, high resolution, endogenous contrast, two-photon imaging to identify distinct adipose tissue types, monitor their functional state, and characterize heterogeneity of induced responses.

  8. Sequential and coherent, optical and x-ray two-photon processes in atoms and molecules

    Science.gov (United States)

    Mills, Jeffrey Dean

    1997-09-01

    Vibronic and rovibronic implementations of conventional semiclassical theories, employing a phenomenological lineshape and descriptive of the absorption of a single photon by isolated chemical particles, are used to account for the absolute magnitude of the highly structured, broadband optical absorption, emission, radiation transfer, and refractive index of high- temperature (T ≈ 2000K), rare-gas-buffered, and locally equilibrated atomic and diatomic metal vapors (Li, Na, Al, and Li/Al). The polarized, resonant, inelastic scattering of x-rays (hν /approx 2.5 keV) from the K-edges of unoriented, chlorine- and sulfur- containing molecular gases (CH3Cl, H2S, and Cl2) is also modeled by means of the fully quantum- mechanical, time-independent Kramers-Heisenberg formalism applied in electronic and vibronic resolution. This accounts for the energy, polarization, and direction dependence of the anisotropic signal, concretely treats the demise of core-excited states by Auger-electron emission within the Feshbach-Fano theory of resonance- continuum mixing, and is in general valid for resonant, nonresonant, inelastic, and 'distinguishable' elastic scattering. Unusual, coherent interference phenomena within and between vibronic and electronic channels and related novel, otherwise-forbidden nondipole features expected to arise in molecules with equivalent atomic centers and recently observed in the chlorine molecule are explored along with their implications for common conceptions of 'localized, equivalent core-hole excited states.' Transition coherence, especially as manifested within the quantum-mechanical treatment of the spectral lineshape, is shown to provide the key to unifying the present single-step interpretation of two-photon x-ray scattering with that involving a pair of successive absorption and emission transitions generally regarded as two independent single-photon processes of the type described in the first portion of the work.

  9. Two-photon photoemission investigation of electronic and dynamical properties of alkali atoms adsorbed on noble metal surfaces

    Science.gov (United States)

    Sametoglu, Vahit

    We present a systematic time-resolved two-photon photoemission study of the electronic and dynamical properties of Li through Cs adsorbed on Cu(111) and Ag(111) surfaces. A fundamental problem in surface science is how to describe the electronic structure of a chemisorption interface based on the intrinsic properties of the interacting materials. Because of their simple s-electron structure, elements of the alkali atom group comprise paradigmatic adsorbates in many theories of chemisorption, whereas the complementary experimental studies are sparse and incomplete. Through a combination of spectroscopic and femtosecond time-resolved surface measurements, we are able to probe systematically the binding energies, symmetries, and electron and nuclear relaxation dynamics of the initially unoccupied alkali atom resonances. As a prelude, we study the two-photon photoemission process occurring at the bare Ag(111) surface. We develop a quantitative model for two-photon photoemission process, where the nonresonant and k-dependent two-photon absorption between the lower and upper sp-bands is modeled by the optical Bloch equations, and the angle-dependent intensities are described by the Fresnel equations. Our two-photon photoemission spectra of Li through Cs chemisorbed Cu(111) and Ag(111) surfaces reveal two resonances with the m = 0 and m = +/-1 symmetry ('m' is the projection of the orbital angular momentum 'l' onto the surface plane). For the m = 0 resonance, which is derived from the hybridization of the ns and npz orbitals of alkali atoms, we find a binding energy of 1.84--1.99 eV below the vacuum level, which is independent of the alkali atom period, and tunes with coverage in a universal manner. At 0.3--0.7 eV higher energy, we discover and identify the m = +/-1 resonance by its characteristic angular intensity distribution, which derives from the antisymmetry of the npx and npy orbitals. We implement a quantitative model for the alkali atom chemisorption based on the

  10. Enhancement of Squeezing in Two-Photon Jaynes-Cummings Model with Atomic Measurement

    Institute of Scientific and Technical Information of China (English)

    YE Sai-Yun

    2006-01-01

    We investigate the squeezing properties of the cavity field in the degenerate two-photon Jaynes-Cummings model. Compared with the one-photon Jaynes-Cummings model, the squeezing is more pronounced in the case of two-photon Jaynes-Cummings model under certain conditions.

  11. Event-by-event simulation of nonclassical effects in two-photon interference experiments

    NARCIS (Netherlands)

    Michielsen, K.; Jin, F.; Delina, M.; Raedt, H. De

    2012-01-01

    A corpuscular simulation model for second-order intensity interference phenomena is discussed. It is shown that both the visibility V = 1/2 predicted for two-photon interference experiments with two independent sources and the visibility V = 1 predicted for two-photon interference experiments with a

  12. Integrated single- and two-photon light sheet microscopy using accelerating beams

    DEFF Research Database (Denmark)

    Piksarv, Peeter; Marti, Dominik; Le, Tuan

    2017-01-01

    We demonstrate the first light sheet microscope using propagation invariant, accelerating Airy beams that operates both in single- and two-photon modes. The use of the Airy beam permits us to develop an ultra compact, high resolution light sheet system without beam scanning. In two-photon mode, a...

  13. Two-photon fluorescence probes for imaging of mitochondria and lysosomes.

    Science.gov (United States)

    Yang, Wanggui; Chan, Pui Shan; Chan, Miu Shan; Li, King Fai; Lo, Pik Kwan; Mak, Nai Ki; Cheah, Kok Wai; Wong, Man Shing

    2013-04-28

    Novel biocompatible cyanines show not only a very large two-photon cross-section of up to 5130 GM at 910 nm in aqueous medium for high-contrast and -brightness two-photon fluorescence live cell imaging but also highly selective subcellular localization properties including localization of mitochondria and lysosomes.

  14. Production of e, $\\mu$ and $\\tau$ Pairs in Untagged Two-Photon Collisions at LEP

    CERN Document Server

    Acciarri, M; Aguilar-Benítez, M; Ahlen, S P; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alverson, G; Alviggi, M G; Ambrosi, G; Anderhub, H; Andreev, V P; Angelescu, T; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Baksay, L; Ball, R C; Banerjee, S; Banerjee, Sw; Banicz, K; Barczyk, A; Barillère, R; Barone, L; Bartalini, P; Baschirotto, A; Basile, M; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Bhattacharya, S; Biasini, M; Biland, A; Bilei, G M; Blaising, J J; Blyth, S C; Bobbink, Gerjan J; Böck, R K; Böhm, A; Boldizsar, L; Borgia, B; Boucham, A; Bourilkov, D; Bourquin, Maurice; Boutigny, D; Braccini, S; Branson, J G; Brigljevic, V; Brock, I C; Buffini, A; Buijs, A; Burger, J D; Burger, W J; Busenitz, J K; Cai, X D; Campanelli, M; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A M; Casaus, J; Castellini, G; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada-Canales, M; Cesaroni, F; Chamizo-Llatas, M; Chang, Y H; Chaturvedi, U K; Chekanov, S V; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chen, M; Chiefari, G; Chien, C Y; Cifarelli, Luisa; Cindolo, F; Civinini, C; Clare, I; Clare, R; Cohn, H O; Coignet, G; Colijn, A P; Colino, N; Commichau, V; Costantini, S; Cotorobai, F; de la Cruz, B; Csilling, Akos; Dai, T S; D'Alessandro, R; De Asmundis, R; Degré, A; Deiters, K; Denes, P; De Notaristefani, F; DiBitonto, Daryl; Diemoz, M; Van Dierendonck, D N; Di Lodovico, F; Dionisi, C; Dittmar, Michael; Dominguez, A; Doria, A; Dorne, I; Dova, M T; Drago, E; Duchesneau, D; Duinker, P; Durán, I; Dutta, S; Easo, S; Efremenko, Yu V; El-Mamouni, H; Engler, A; Eppling, F J; Erné, F C; Ernenwein, J P; Extermann, Pierre; Fabre, M; Faccini, R; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, Marta; Fenyi, B; Ferguson, T; Ferroni, F; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, Frank; Fisher, P H; Fisk, I; Forconi, G; Fredj, L; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gau, S S; Gentile, S; Gerald, J; Gheordanescu, N; Giagu, S; Goldfarb, S; Goldstein, J; Gong, Z F; Gougas, Andreas; Gratta, Giorgio; Grünewald, M W; Gupta, V K; Gurtu, A; Gutay, L J; Hartmann, B; Hasan, A; Hatzifotiadou, D; Hebbeker, T; Hervé, A; Van Hoek, W C; Hofer, H; Hong, S J; Hoorani, H; Hou, S R; Hu, G; Innocente, Vincenzo; Janssen, H; Jenkes, K; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Kasser, A; Khan, R A; Kamrad, D; Kamyshkov, Yu A; Kapustinsky, J S; Karyotakis, Yu; Kaur, M; Kienzle-Focacci, M N; Kim, D; Kim, D H; Kim, J K; Kim, S C; Kim, Y G; Kinnison, W W; Kirkby, A; Kirkby, D; Kirkby, Jasper; Kiss, D; Kittel, E W; Klimentov, A; König, A C; Kopp, A; Korolko, I; Koutsenko, V F; Krämer, R W; Krenz, W; Kunin, A; Ladrón de Guevara, P; Landi, G; Lapoint, C; Lassila-Perini, K M; Laurikainen, P; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Leggett, C; Le Goff, J M; Leiste, R; Leonardi, E; Levchenko, P M; Li Chuan; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lu, W; Lü, Y S; Lübelsmeyer, K; Luci, C; Luckey, D; Luminari, L; Lustermann, W; Ma Wen Gan; Maity, M; Majumder, G; Malgeri, L; Malinin, A; Maña, C; Mangeol, D J J; Mangla, S; Marchesini, P A; Marin, A; Martin, J P; Marzano, F; Massaro, G G G; McNally, D; Mele, S; Merola, L; Meschini, M; Metzger, W J; Von der Mey, M; Mi, Y; Mihul, A; Van Mil, A J W; Mirabelli, G; Mnich, J; Molnár, P; Monteleoni, B; Moore, R; Morganti, S; Moulik, T; Mount, R; Müller, S; Muheim, F; Muijs, A J M; Nahn, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Niessen, T; Nippe, A; Nisati, A; Nowak, H; Oh, Yu D; Opitz, H; Organtini, G; Ostonen, R; Palomares, C; Pandoulas, D; Paoletti, S; Paolucci, P; Park, H K; Park, I H; Pascale, G; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Peach, D; Pei, Y J; Pensotti, S; Perret-Gallix, D; Petersen, B; Petrak, S; Pevsner, A; Piccolo, D; Pieri, M; Pinto, J C; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Postema, H; Produit, N; Prokofev, D; Prokofiev, D O; Rahal-Callot, G; Raja, N; Rancoita, P G; Rattaggi, M; Raven, G; Razis, P A; Read, K; Ren, D; Rescigno, M; Reucroft, S; Van Rhee, T; Riemann, S; Riles, K; Rind, O; Robohm, A; Rodin, J; Roe, B P; Romero, L; Rosier-Lees, S; Rosselet, P; Van Rossum, W; Roth, S; Rubio, Juan Antonio; Ruschmeier, D; Rykaczewski, H; Salicio, J; Sánchez, E; Sanders, M P; Sarakinos, M E; Sarkar, S; Sassowsky, M; Sauvage, G; Schäfer, C; Shchegelskii, V; Schmidt-Kärst, S; Schmitz, D; Schmitz, P; Schneegans, M; Scholz, N; Schopper, Herwig Franz; Schotanus, D J; Schwenke, J; Schwering, G; Sciacca, C; Sciarrino, D; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shukla, J; Shumilov, E; Shvorob, A V; Siedenburg, T; Son, D; Sopczak, André; Soulimov, V; Smith, B; Spillantini, P; Steuer, M; Stickland, D P; Stone, H; Stoyanov, B; Strässner, A; Strauch, K; Sudhakar, K; Sultanov, G G; Sun, L Z; Susinno, G F; Suter, H; Swain, J D; Tang, X W; Tauscher, Ludwig; Taylor, L; Ting, Samuel C C; Ting, S M; Tonutti, M; Tonwar, S C; Tóth, J; Tully, C; Tuchscherer, H; Tung, K L; Uchida, Y; Ulbricht, J; Uwer, U; Valente, E; Van de Walle, R T; Vesztergombi, G; Vetlitskii, I; Viertel, Gert M; Vivargent, M; Völkert, R; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Vorvolakos, A; Wadhwa, M; Wallraff, W; Wang, J C; Wang, X L; Wang, Z M; Weber, A; Wittgenstein, F; Wu, S X; Wynhoff, S; Xu, J; Xu, Z Z; Yang, B Z; Yang, C G; Yao, X Y; Ye, J B; Yeh, S C; You, J M; Zalite, A; Zalite, Yu; Zemp, P; Zeng, Y; Zhang, Z; Zhang, Z P; Zhou, B; Zhou, Y; Zhu, G Y; Zhu, R Y; Zichichi, Antonino; Ziegler, F

    1997-01-01

    The two-photon collision reaction e+e- --> e+e-l+l- has been studied at root(s) ~ 91 GeV using the L3 detector at LEP for l = e, muon , tau. We have analysed untagged configurations where the two photons are quasi-real. Good agreement is found between our measurements and the order alpha**4 QED expectation.

  15. Temporal dynamics of two-photon-pumped amplified spontaneous emission in slab organic crystals

    NARCIS (Netherlands)

    Fang, Hong-Hua; Chen, Qi-Dai; Ding, Ran; Yang, Jie; Ma, Yu-Guang; Wang, Hai-Yu; Gao, Bing-Rong; Feng, Jing; Sun, Hong-Bo; Fang, Honghua

    2010-01-01

    We have studied the ultrafast dynamics of two-photon-pumped amplified spontaneous emission (ASE) from a single crystal by the time-resolved fluorescence upconversion technique. With the increase of two-photon pump intensities, the emission decay time is dramatically shortened by 30 times (from 3 ns

  16. Two-Photon Interference with the Type Ⅱ Spontaneous Parametric Down-Conversion

    Institute of Scientific and Technical Information of China (English)

    江云坤; 史保森; 李剑; 段开敏; 范晓锋; 郭光灿

    2001-01-01

    The two-photon polarized entangled state is generated from the type Ⅱ spontaneous parametric down-conversion pumped by a femtosecond pulse. The two-photon interference is observed in the Hong-Ou-Mandel interferometer. The high visibility of the interference is restored with narrow band interference filters placed in front of the detectors.

  17. Time-dependent study of radiation trapping by time-delayed two-photon absorption

    Energy Technology Data Exchange (ETDEWEB)

    Molander, W.; Belsley, M.; Streater, A.; Burnett, K.

    1983-10-01

    The transport of resonance radiation through an optically thick vapor of Sr atoms is studied. A pulsed dye laser tuned to the 461 nm resonance line excites a narrow (approx. 60 ..mu..m diam) column of Sr atoms along the axis of a cylindrical oven containing Sr vapor and Ar buffer gas. After a delay of less than or equal to 80 ns, a second dye laser excites the atom from the first excited state (5s5p) to a higher excited state (5s7s). The fluorescence from this latter transition is monitored as the second laser is translated parallel to the first. Since the excited state-excited state fluorescence is not trapped the result is a plot of density of atoms in the 5s5p state as a function of position from the originally excited volume. The results are discussed qualitatively.

  18. Understanding the Two-Photon Absorption Spectrum of PE2 Platinum Acetylide Complex

    Science.gov (United States)

    2014-07-09

    Materials Division Marcelo G. Vivas - Instituto de Ciência de Tecnologia , Universidade Federal de Alfenas, Cidade Universitári, BR Leonardo De Boni...Instituto de Ciência de Tecnologia , Universidade Federal de Alfenas, Cidade Universitári, BR 267 Km 533, 37715- 400 Poços de Caldas, MG Brazil...Saõ Paulo, CP 369, 13560-970, Saõ Carlos, SP Brazil ‡Instituto de Cien̂cia de Tecnologia , Universidade Federal de Alfenas, Cidade UniversitaŕiaBR

  19. Description of states of two-photon interference in optical gating Michelson interferometer

    Science.gov (United States)

    Pongophas, Ekkarat; Sinsarp, Asawin; Suwanna, Sujin; Chunwachirasiri, Withoon; Singhsomroje, Wisit

    2015-07-01

    The interference of two photons in the optical gating Michelson interferometer is investigated. The phenomenon is studied using two different representations of photons: the space-time domain and a step-by-step two photon state evolution. Both representations lead to an equivalent description of the two-photon states which is the interference of four cases of two-photon traveling states, as implied by the evolution analysis. Additionally, the space-time domain analysis reveals that the classical interference of high-intensity light source is identical to the two-photon interference in the quantum regime except for a multiplicative factor of (n 2), where n is the number of photons.

  20. Imaging theory and resolution improvement of two-photon confocal microscopy

    Institute of Scientific and Technical Information of China (English)

    唐志列; 杨初平; 裴红津; 梁瑞生; 刘颂豪

    2002-01-01

    The nonlinear effect of two-photon excitation on the imaging property of two-photonconfocal microscopy has been analyzed by the two-photon fluorescence intensity transfer functionderived in this paper. The two-photon fluorescence intensity transfer function in a confocal micros-copy is given. Furthermore the three-dimensional point spread function (3D-PSF) and thethree-dimensional optical transfer function (3D-OTF) of two-photon confocal microscopy are de-rived based on the nonlinear effect of two-photon excitation. The imaging property of two-photonconfocal microscopy is discussed in detail based on 3D-OTF. Finally the spatial resolution limit oftwo-photon confocal microscopy is discussed according to the uncertainty principle.

  1. Theoretical investigation on ratiometric two-photon fluorescent probe for Zn2+ detection based on ICT mechanism

    Science.gov (United States)

    Huang, Shuang; Yang, Bao-Zhu; Ren, Ai-Min

    2016-06-01

    OPA (one-photon absorption), TPA (two-photon absorption) and fluorescence properties of a free ligand L upon coordination with Zn2+, and the regeneration with CN- were investigated in theory. According to our research, OPA spectra of ligand L show red-shift binding with Zn2+ while blue-shift with CN-. The fluorescence spectra and TPA wavelength are shifted in the same situation as those of OPA spectra. The value of TPA cross-section decreased at first, and then increased to 1813 GM for [L-Zn(CN)4]2-. Intramolecular charge transfer (ICT) mechanism was investigated by natural bond orbital (NBO) analysis. It demonstrates that L is hopeful to be a good ratiometric fluorescent probe for zinc ion detection in solution, and it can regenerate after CN- was introduced.

  2. Enhanced two photon fluorescence microfluidic sensor based on dual cladding photonic-crystal fiber

    Science.gov (United States)

    Amitonova, Lyubov; Fedotov, Ilya; Fedotov, Andrey; Zheltikov, Aleksei

    2012-11-01

    The architecture of photonic-crystal fibers (PCFs) suggests a variety of strategies for optical sensing. A combination of TPA approaches with capabilities of fiber-optic probes offers numerous advantages, suggesting a convenient format for beam delivery, facilitating manipulation of excitation radiation, and allowing this excitation to be applied locally and selectively. In this work, we show that a PCF with a special design can realize different protocols of optical sensing, simultaneously serving, whenever necessary, for the collection and on-line monitoring of liquid-phase samples. Specially designed PCF is shown to substantially increase the guided-wave luminescent response from molecules excited through two-photon absorption (TPA) by femtosecond near-infrared laser pulses. Biophotonic implications of this waveguide TPL-response enhancement include fiber-format solutions for online monitoring of drug delivery and drug activation, interrogation of neural activity, biosensing, endoscopy, and locally controlled singlet oxygen generation in photodynamic therapy. This work was supported by the Russian Foundation for Basic Research, project 11-04-12185-ofi-m.

  3. A two-photon laser induced fluorescence diagnostic with improved sensitivity, localization, and measurement rate

    Science.gov (United States)

    Elliott, Drew; Scime, Earl; Short, Zachary

    2016-10-01

    A two-photon absorption laser induced fluorescence diagnostic has been developed for measuring neutrals in fusion plasmas. Implementation of this diagnostic on the HIT-SI3 spheromak has demonstrated the sensitivity of the diagnostic and shown that measurements taken over several plasma pulses are possible. These measurements yielded an unexpected loss of signal when complex collection optics were utilized. Simulations show that this loss of signal can be explained by chromatic aberrations caused by the disparate Kr and D emission. This loss of signal has been addressed with the development of a new calibration scheme involving xenon gas. The Xe calibration scheme emission occurs at 656.00 nm while the deuterium emission is 656.09 nm. This nearly identical emission allows for advanced optical techniques such as confocal collection/injection and spatial filtering to be employed without loss of signal. Spatial filtering has been demonstrated to decrease noise while improving measurement localization, while confocal collection/injection allows for probing and measuring to occur through one viewport. The Xe scheme also allows for a Doppler-free hydrogen measurement. Doppler-free measurements eliminate the need to scan the laser spectrally thus greatly increasing the rate of measurement.

  4. Zn2+ responsive two-photon fluorescent probes based on branch structure: a computational investigation

    Science.gov (United States)

    Huang, Shuang; Yang, Bao-Zhu; Guo, Jing-Fu; Ren, Ai-Min

    2015-03-01

    A series of zinc ion fluorescent probes on the basis of multi-branched ligands were investigated in theory. The three-branched ligand TPPA (N,N,N‧,N‧-tetraphenyl-p-phenylenediamine) has better three-dimensional spatial localisation, which can detect zinc at the parts per million level. The complex coordinated with Zn2+ can show a significant improvement in two-photon absorption (TPA) cross-section in the near-infrared (NIR) excitation region. The calculated results reveal that the stability and sensitivity of Zn2+ complexes will be enhanced by increasing the number of branches. The selectivity of double phenyl-p-phenylenediamine (DPPA) ligand to Zn2+ will be better compared to Cd2+. With regard to the studied ligands single phenyl-p-phenylenediamine (SPPA), two connected single phenyl-p-phenylenediamine (2CSPPA), DPPA and TPPA, λEMmax shows a red-shift and ƒEM gets stronger upon the addition of Zn2+. Most of the molecules exhibit TPA peaks in the NIR region. The theoretical investigations demonstrate that DPPA-Zn2+ shows good TPA activity at a telecommunication wavelength.

  5. A two-photon probe for Al(3+) in aqueous solution and its application in bioimaging.

    Science.gov (United States)

    Wang, Haihong; Wang, Bei; Shi, Zhaohua; Tang, Xiaoliang; Dou, Wei; Han, Qingxin; Zhang, Yange; Liu, Weisheng

    2015-03-15

    A salicylimine probe L with a simple structure has been researched more in-depth on fluorescence sensor properties based on two-photon (TP) absorption. L displays excellent selective turn-on fluorescence response for Al(3+) in hexamethylenetetramine-buffered (HMTA) aqueous solution (0.3M, pH=5.8) under one-photon (OP) excitation. With the help of OP fluorescence, TP fluorescence titration, UV-spectra titration and Job's plot, the stoichiometric ratio of L with Al(3+) was determined to be 1:1. The coordination sites and the coordination mechanism of L with Al(3+) were analyzed in detail through (1)H NMR data. Not only with a detection limit of 5.2×10(-9)M in vitro, but also the probe has been successfully used in the live cells and tissues for the imaging of Al(3+) with TP fluorescence microscopy due to the enlarged TP cross section, providing a novel testing method for measuring Al(3+) in solution or cell tissue with low autofluorescence and cytotoxicity.

  6. Measurement of drug-target engagement in live cells by two-photon fluorescence anisotropy imaging.

    Science.gov (United States)

    Vinegoni, Claudio; Fumene Feruglio, Paolo; Brand, Christian; Lee, Sungon; Nibbs, Antoinette E; Stapleton, Shawn; Shah, Sunil; Gryczynski, Ignacy; Reiner, Thomas; Mazitschek, Ralph; Weissleder, Ralph

    2017-07-01

    The ability to directly image and quantify drug-target engagement and drug distribution with subcellular resolution in live cells and whole organisms is a prerequisite to establishing accurate models of the kinetics and dynamics of drug action. Such methods would thus have far-reaching applications in drug development and molecular pharmacology. We recently presented one such technique based on fluorescence anisotropy, a spectroscopic method based on polarization light analysis and capable of measuring the binding interaction between molecules. Our technique allows the direct characterization of target engagement of fluorescently labeled drugs, using fluorophores with a fluorescence lifetime larger than the rotational correlation of the bound complex. Here we describe an optimized protocol for simultaneous dual-channel two-photon fluorescence anisotropy microscopy acquisition to perform drug-target measurements. We also provide the necessary software to implement stream processing to visualize images and to calculate quantitative parameters. The assembly and characterization part of the protocol can be implemented in 1 d. Sample preparation, characterization and imaging of drug binding can be completed in 2 d. Although currently adapted to an Olympus FV1000MPE microscope, the protocol can be extended to other commercial or custom-built microscopes.

  7. Responsive mechanism of 2-(2’-hydroxyphenyl)benzoxazole-based two-photon fluorescent probes for zinc and hydroxide ions

    Institute of Scientific and Technical Information of China (English)

    张玉瑾; 张秋月; 丁红娟; 宋秀能; 王传奎

    2015-01-01

    The response theory is used to investigate one-and two-photon absorption (TPA) as well as emission properties of a series of potential zinc ion and pH sensitive materials containing 2-(2’-hydroxyphenyl)benzoxazole (HPBO) end groups. Special emphasis is placed on the evolution of their optical properties upon combining with zinc ions or deprotonation. Calculated results indicate that upon combining with zinc ions or deprotonation, these HPBO derivatives show drastic changes in their one-photon absorption (OPA), emission, and TPA properties. Moreover, mechanisms of the probes are analyzed to be intramolecular charge transfer. These compounds are thus proved to be excellent candidates for two-photon fl uorescent zinc and pH probes.

  8. Two-photon excitation of surface plasmon and the period-increasing effect of low spatial frequency ripples on a GaP crystal in air/water

    Science.gov (United States)

    Liu, Jukun; Jia, Tianqing; Zhao, Hongwei; Huang, Yaoqing

    2016-11-01

    We report the period-increasing effect of low spatial frequency ripples on a GaP crystal irradiated by 1 kHz, 50 fs, 800 nm femtosecond laser pulses. Massive free electrons are excited by a two-photon absorption process and surface plasmon is excited. The Drude model is used to estimate the changing of the dielectric constant of the GaP crystal. The period-increasing effects of low spatial frequency laser-induced ripples are theoretically predicted in air/water, and the experimental results agree well. The experimental and theoretical results indicate that surface plasmon excited by two-photon absorption plays a key role in the formation of low spatial frequency ripples.

  9. Application of FTIR Absorption Spectroscopy to Characterize Waste and Biofuels for Pyrolysis and Gasification

    OpenAIRE

    KALISZ Sylwester; Svoboda, Karel; ROBAK Zbigniew; Baxter, David; Andersen, Lars

    2008-01-01

    The paper discusses the various applications of FTIR absorption spectroscopy as a tool for characterizing waste biofuels for pyrolysis and gasification. The FTIR spectrometer used in the study allows for analysis of solid and liquid waste and biofuel samples. Further, an attached dedicated gas cell is used in the characterization of gases evolving during pyrolysis in a versatile pyrolyser/gasifier attached to the FTIR. The pyrolyser operates in a batch mode and generates large quantities o...

  10. Characteristic measurement for femtosecond laser pulses using a GaAs PIN photodiode as a two-photon photovoltaic receiver

    Science.gov (United States)

    Chen, Junbao; Xia, Wei; Wang, Ming

    2017-06-01

    Photodiodes that exhibit a two-photon absorption effect within the spectral communication band region can be useful for building an ultra-compact autocorrelator for the characteristic inspection of optical pulses. In this work, we develop an autocorrelator for measuring the temporal profile of pulses at 1550 nm from an erbium-doped fiber laser based on the two-photon photovoltaic (TPP) effect in a GaAs PIN photodiode. The temporal envelope of the autocorrelation function contains two symmetrical temporal side lobes due to the third order dispersion of the laser pulses. Moreover, the joint time-frequency distribution of the dispersive pulses and the dissimilar two-photon response spectrum of GaAs and Si result in different delays for the appearance of the temporal side lobes. Compared with Si, GaAs displays a greater sensitivity for pulse shape reconstruction at 1550 nm, benefiting from the higher signal-to-noise ratio of the side lobes and the more centralized waveform of the autocorrelation trace. We also measure the pulse width using the GaAs PIN photodiode, and the resolution of the measured full width at half maximum of the TPP autocorrelation trace is 0.89 fs, which is consistent with a conventional second-harmonic generation crystal autocorrelator. The GaAs PIN photodiode is shown to be highly suitable for real-time second-order autocorrelation measurements of femtosecond optical pulses. It is used both for the generation and detection of the autocorrelation signal, allowing the construction of a compact and inexpensive intensity autocorrelator.

  11. Dispersion spreading of biphotons in optical fibres and two-photon interference

    CERN Document Server

    Brida, G; Genovèse, M; Gramegna, M; Krivitsky, L A

    2006-01-01

    We present the first observation of two-photon polarization interference structure in the second-order Glauber's correlation function of two-photon light generated via type-II spontaneous parametric down-conversion. In order to obtain this result, two-photon light is transmitted through an optical fibre and the coincidence distribution is analyzed by means of the START-STOP method. Beyond the experimental demonstration of an interesting effect in quantum optics, these results also have considerable relevance for quantum communications.

  12. Coalescence and Anti-Coalescence Interference of Two-Photon Wavepacket in a Beam Splitter

    Institute of Scientific and Technical Information of China (English)

    WANG Kai-Ge; YANG Guo-Jian

    2004-01-01

    @@ We study theoretically the interference of a two-photon wavepacket in a beam splitter. We find that the spectrum symmetry for the two-photon wavepacket dominates the perfect coalescence and anti-coalescence interference.The coalescence interference is unrelated to photon entanglement. Only the anti-coalescence interference has evidence of photon entanglement. We prove that the two-photon wavepacket with an anti-symmetric spectrum is transparent to pass the 50/50 beam splitter, showing perfect anti-coalescence interference.

  13. The two-photon exchange contribution to elastic electron-nucleon scattering at large momentum transfer

    Energy Technology Data Exchange (ETDEWEB)

    Andrei V. Afanasev; Stanley J. Brodsky; Carl E. Carlson; Yu-Chun Chen; Marc Vanderhaeghen

    2005-01-01

    We estimate the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer by using a quark-parton representation of virtual Compton scattering. We thus can relate the two-photon exchange amplitude to the generalized parton distributions which also enter in other wide angle scattering processes. We find that the interference of one- and two-photon exchange contribution is able to substantially resolve the difference between electric form factor measurements from Rosenbluth and polarization transfer experiments.

  14. Dispersion spreading of biphotons in optical fibers and two-photon interference.

    Science.gov (United States)

    Brida, G; Chekhova, M V; Genovese, M; Gramegna, M; Krivitsky, L A

    2006-04-14

    We present the first observation of two-photon polarization interference structure in the second-order Glauber correlation function of two-photon light generated via type-II spontaneous parametric down-conversion. In order to obtain this result, two-photon light is transmitted through an optical fiber and the coincidence distribution is analyzed by means of the start-stop method. Beyond the experimental demonstration of an interesting effect in quantum optics, these results also have considerable relevance for quantum communications.

  15. Search for a Higgs boson decaying into two photons in the CMS detector

    Indian Academy of Sciences (India)

    Roberta Volpe; on behalf of the CMS Collaboration

    2012-11-01

    A search for a Higgs boson decaying into two photons in collisions at the LHC at a centre-of-mass energy of 7 TeV is presented. The analysis is performed on a dataset corresponding to 1.66 fb-1 of data recorded in 2011 by the CMS experiment. Limits are set on the cross-section of a Standard Model Higgs boson decaying into two photons, and on the cross-section of a fermiophobic Higgs boson decaying into two photons.

  16. Dicke Coherent Narrowing in Two-Photon and Raman Spectroscopy of Thin Vapour Cells

    CERN Document Server

    Dutier, G; Hamdi, I; Maurin, I; Saltiel, S; Bloch, D; Ducloy, M; Dutier, Gabriel; Todorov, Petko; Hamdi, Ismah\\`{e}ne; Maurin, Isabelle; Saltiel, Solomon; Bloch, Daniel; Ducloy, Martial

    2005-01-01

    The principle of coherent Dicke narrowing in a thin vapour cell, in which sub-Doppler spectral lineshapes are observed under a normal irradiation for a l/2 thickness, is generalized to two-photon spectroscopy. Only the sum of the two wave vectors must be normal to the cell, making the two-photon scheme highly versatile. A comparison is provided between the Dicke narrowing with copropagating fields, and the residual Doppler-broadening occurring with counterpropagating geometries. The experimental feasibility is discussed on the basis of a first observation of a two-photon resonance in a 300 nm-thick Cs cell. Extension to the Raman situation is finally considered.

  17. Monitoring photosensitizer uptake using two photon fluorescence lifetime imaging microscopy.

    Science.gov (United States)

    Yeh, Shu-Chi Allison; Diamond, Kevin R; Patterson, Michael S; Nie, Zhaojun; Hayward, Joseph E; Fang, Qiyin

    2012-01-01

    Photodynamic Therapy (PDT) provides an opportunity for treatment of various invasive tumors by the use of a cancer targeting photosensitizing agent and light of specific wavelengths. However, real-time monitoring of drug localization is desirable because the induction of the phototoxic effect relies on interplay between the dosage of localized drug and light. Fluorescence emission in PDT may be used to monitor the uptake process but fluorescence intensity is subject to variability due to scattering and absorption; the addition of fluorescence lifetime may be beneficial to probe site-specific drug-molecular interactions and cell damage. We investigated the fluorescence lifetime changes of Photofrin(®) at various intracellular components in the Mat-LyLu (MLL) cell line. The fluorescence decays were analyzed using a bi-exponential model, followed by segmentation analysis of lifetime parameters. When Photofrin(®) was localized at the cell membrane, the slow lifetime component was found to be significantly shorter (4.3 ± 0.5 ns) compared to those at other locations (cytoplasm: 7.3 ± 0.3 ns; mitochondria: 7.0 ± 0.2 ns, p < 0.05).

  18. Monitoring Photosensitizer Uptake Using Two Photon Fluorescence Lifetime Imaging Microscopy

    Directory of Open Access Journals (Sweden)

    Shu-Chi Allison Yeh, Kevin R. Diamond, Michael S. Patterson, Zhaojun Nie, Joseph E. Hayward, Qiyin Fang

    2012-01-01

    Full Text Available Photodynamic Therapy (PDT provides an opportunity for treatment of various invasive tumors by the use of a cancer targeting photosensitizing agent and light of specific wavelengths. However, real-time monitoring of drug localization is desirable because the induction of the phototoxic effect relies on interplay between the dosage of localized drug and light. Fluorescence emission in PDT may be used to monitor the uptake process but fluorescence intensity is subject to variability due to scattering and absorption; the addition of fluorescence lifetime may be beneficial to probe site-specific drug-molecular interactions and cell damage. We investigated the fluorescence lifetime changes of Photofrin® at various intracellular components in the Mat-LyLu (MLL cell line. The fluorescence decays were analyzed using a bi-exponential model, followed by segmentation analysis of lifetime parameters. When Photofrin® was localized at the cell membrane, the slow lifetime component was found to be significantly shorter (4.3 ± 0.5 ns compared to those at other locations (cytoplasm: 7.3 ± 0.3 ns; mitochondria: 7.0 ± 0.2 ns, p < 0.05.

  19. Energy transfer in aminonaphthalimide-boron-dipyrromethene (BODIPY) dyads upon one- and two-photon excitation: applications for cellular imaging.

    Science.gov (United States)

    Collado, Daniel; Remón, Patricia; Vida, Yolanda; Najera, Francisco; Sen, Pratik; Pischel, Uwe; Perez-Inestrosa, Ezequiel

    2014-03-01

    Aminonaphthalimide-BODIPY energy transfer cassettes were found to show very fast (kEET ≈ 10(10)-10(11) s(-1) and efficient BODIPY fluorescence sensitization. This was observed upon one- and two-photon excitation, which extends the application range of the investigated bichromophoric dyads in terms of accessible excitation wavelengths. In comparison with the direct excitation of the BODIPY chromophore, the two-photon absorption cross-section δ of the dyads is significantly incremented by the presence of the aminonaphthalimide donor [δ ≈ 10 GM for the BODIPY versus 19-26 GM in the dyad at λ(exc)=840 nm; 1 GM (Goeppert-Mayer unit)=10(-50) cm(4) smolecule(-1) photon-(1)]. The electronic decoupling of the donor and acceptor, which is a precondition for the energy transfercassette concept, was demonstrated by time-dependent density functional theory calculations. The applicability of the new probes in the one- and twophoton excitation mode was demonstrated in a proof-of-principle approach in the fluorescence imaging of HeLa cells. To the best of our knowledge, this is the first demonstration of the merging of multiphoton excitation with the energy transfer cassette concept for a BODIPY-containing dyad.

  20. Deep-red polymer dots with bright two-photon fluorescence and high biocompatibility for in vivo mouse brain imaging

    Science.gov (United States)

    Alifu, Nuernisha; Sun, Zezhou; Zebibula, Abudureheman; Zhu, Zhenggang; Zhao, Xinyuan; Wu, Changfeng; Wang, Yalun; Qian, Jun

    2017-09-01

    With high contrast and deep penetration, two-photon fluorescence (2PF) imaging has become one of the most promising in vivo fluorescence imaging techniques. To obtain good imaging contrast, fluorescent nanoprobes with good 2PF properties are highly needed. In this work, bright 2PF polymer dots (P dots) were applied for in vivo mouse brain imaging. Deep-red emissive P dots with PFBT as the donor and PFDBT5 as the acceptor were synthesized and used as a contrast agent. P dots were further encapsulated by poly(styrene-co-maleic anhydride) (PSMA) and grafted with poly(ethylene glycol) (PEG). The P dots-PEG exhibit large two-photon absorption (2PA) cross-sections (δ≥8500 g), good water dispersibility, and high biocompatibility. P dots-PEG was further utilized first time for in vivo vascular imaging of mouse ear and brain, under 690-900 nm femtosecond (fs) laser excitation. Due to the large 2PA cross-section and deep-red emission, a large imaging depth ( 720 μm) was achieved.

  1. Plasmonic-enhanced two-photon fluorescence with single gold nanoshell

    Science.gov (United States)

    Zhang, TianYue; Lu, GuoWei; Shen, HongMing; Perriat, P.; Martini, M.; Tillement, O.; Gong, QiHuang

    2014-06-01

    Single gold nanoshell with mutilpolar plasmon resonances is proposed to enhance two-photon fluorescence efficiently. The single emitter single nanoshell configuration is studied systematically by employing the finite-difference time-domain method. The emitter located inside or outside the nanoshell at various positions leads to a significantly different enhancement effect. The fluorescent emitter placed outside the nanoshell can achieve large fluorescence intensity given that both the position and orientation of the emission dipole are optimally controlled. In contrast, for the case of the emitter placed inside the nanoshell, it can experience substantial two-photon fluorescence enhancement without strict requirements upon the position and dipole orientations. Metallic nanoshell encapsulating many fluorescent emitters should be a promising nanocomposite configuration for bright two-photon fluorescence label. The results provide a comprehensive understanding about the plasmonic-enhanced two-photon fluorescence behaviors, and the nanocomposite configuration has great potential for optical detecting, imaging and sensing in biological applications.

  2. LANTHANIDE ENHANCE LUMINESCENCE (LEL) WITH ONE AND TWO PHOTON EXCITATION OF QUANTUM DYES LANTHANIDE (III) - MACROCYCLES

    Science.gov (United States)

    Title: Lanthanide Enhance Luminescence (LEL) with one and two photon excitation of Quantum Dyes? Lanthanide(III)-Macrocycles Principal Author:Robert C. Leif, Newport InstrumentsSecondary Authors:Margie C. Becker, Phoenix Flow Systems Al Bromm, Virginia Commonw...

  3. A compact two photon light sheet microscope for applications in neuroscience

    DEFF Research Database (Denmark)

    Piksarv, Peeter; Marti, Dominik; Le, Tuan

    2016-01-01

    We present a compact setup for two photon light sheet microscopy. By using pulsed Airy beam illumination we demonstrate eight-fold increase of the FOV compared to Gaussian light sheet with the same axial resolution....

  4. Solving Two Kinds of JC Models Relating to Two-Photon Process by Supersymmetric Transformation

    Institute of Scientific and Technical Information of China (English)

    FAN Hong-Yi; Wei-Jun

    2004-01-01

    We propose two kinds of new Jaynes Cummings models relating to two-photon process by using the supersymmetric unitary transformation. The corresponding energy eigenvalues and eigenvectors are obtained.

  5. LANTHANIDE ENHANCE LUMINESCENCE (LEL) WITH ONE AND TWO PHOTON EXCITATION OF QUANTUM DYES LANTHANIDE (III) - MACROCYCLES

    Science.gov (United States)

    Title: Lanthanide Enhance Luminescence (LEL) with one and two photon excitation of Quantum Dyes? Lanthanide(III)-Macrocycles Principal Author:Robert C. Leif, Newport InstrumentsSecondary Authors:Margie C. Becker, Phoenix Flow Systems Al Bromm, Virginia Commonw...

  6. Two-photon excitation with pico-second fluorescence lifetime imaging to detect nuclear association of flavanols

    Energy Technology Data Exchange (ETDEWEB)

    Mueller-Harvey, Irene, E-mail: i.mueller-harvey@reading.ac.uk [Chemistry and Biochemistry Laboratory, Food Production and Quality Research Division, School of Agriculture, Policy and Development, University of Reading, P O Box 236, Reading RG6 6AT (United Kingdom); Feucht, Walter, E-mail: walter.feucht@gmail.com [Department of Plant Sciences, Technical University of Munich (TUM), Wissenschaftszentrum Weihenstephan (WZW), D-85354 Freising (Germany); Polster, Juergen, E-mail: j.polster@wzw.tum.de [Department of Physical Biochemistry, Technical University of Munich (TUM), Wissenschaftszentrum Weihenstephan (WZW), D-85354 Freising (Germany); Trnkova, Lucie, E-mail: lucie.trnkova@uhk.cz [University of Hradec Kralove, Faculty of Science, Department of Chemistry, Rokitanskeho 62, 50003 Hradec Kralove (Czech Republic); Burgos, Pierre, E-mail: pierre.burgos@stfc.ac.uk [Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell-Oxford, Didcot, Oxfordshire, OX11 0QX (United Kingdom); Parker, Anthony W., E-mail: tony.parker@stfc.ac.uk [Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell-Oxford, Didcot, Oxfordshire, OX11 0QX (United Kingdom); Botchway, Stanley W., E-mail: stan.botchway@stfc.ac.uk [Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell-Oxford, Didcot, Oxfordshire, OX11 0QX (United Kingdom)

    2012-03-16

    is significant nuclear absorption of flavanols. This advanced imaging using two-photon excitation and biophysical techniques described here will prove valuable for probing the intracellular trafficking and functions of flavanols, such as EGCG, which is the major flavanol of green tea.

  7. Absolute Frequency Measurement of Rubidium 5S-7S Two-Photon Transitions

    CERN Document Server

    Morzynski, Piotr; Ablewski, Piotr; Gartman, Rafal; Gawlik, Wojciech; Maslowski, Piotr; Nagorny, Bartlomiej; Ozimek, Filip; Radzewicz, Czeslaw; Witkowski, Marcin; Ciurylo, Roman; Zawada, Michal

    2013-01-01

    We report the absolute frequency measurements of rubidium 5S-7S two-photon transitions with a cw laser digitally locked to an atomic transition and referenced to an optical frequency comb. The narrow, two-photon transition, 5S-7S (760 nm) insensitive to first order in a magnetic field, is a promising candidate for frequency reference. The performed tests yield the transition frequency with accuracy better than reported previously.

  8. Fast two-photon neuronal imaging and control using a spatial light modulator and ruthenium compounds

    Science.gov (United States)

    Peterka, Darcy S.; Nikolenko, Volodymyr; Fino, Elodie; Araya, Roberto; Etchenique, Roberto; Yuste, Rafael

    2010-02-01

    We have developed a spatial light modulator (SLM) based microscope that uses diffraction to shape the incoming two-photon laser source to any arbitrary light pattern. This allows the simultaneous imaging or photostimulation of different regions of a sample with three-dimensional precision at high frame rates. Additionally, we have combined this microscope with a new class of two photon active neuromodulators with Ruthenium BiPyridine (RuBi) based cages that offer great flexibility for neuronal control.

  9. Two-photon ionization of atomic hydrogen with elliptically polarized light

    Science.gov (United States)

    Kassaee, A.; Rustgi, M. L.; Long, S. A. T.

    1988-01-01

    The theory of two-photon ionization of a hydrogenic state in the nonrelativistic dipole approximation is generalized for elliptically polarized light. An application to the metastable 2S state of atomic hydrogen is made. Significant differences in the angular distribution of the outgoing electrons are found depending upon the polarization of the photons. It is claimed that two-photon ionization employing elliptically polarized photons from lasers may provide an additional test for the theories of multiphoton ionization.

  10. Two-photon neuronal and astrocytic stimulation with azobenzene-based photoswitches.

    Science.gov (United States)

    Izquierdo-Serra, Mercè; Gascón-Moya, Marta; Hirtz, Jan J; Pittolo, Silvia; Poskanzer, Kira E; Ferrer, Èric; Alibés, Ramon; Busqué, Félix; Yuste, Rafael; Hernando, Jordi; Gorostiza, Pau

    2014-06-18

    Synthetic photochromic compounds can be designed to control a variety of proteins and their biochemical functions in living cells, but the high spatiotemporal precision and tissue penetration of two-photon stimulation have never been investigated in these molecules. Here we demonstrate two-photon excitation of azobenzene-based protein switches and versatile strategies to enhance their photochemical responses. This enables new applications to control the activation of neurons and astrocytes with cellular and subcellular resolution.

  11. Three-Dimensional Control of DNA Hybridization by Orthogonal Two-Color Two-Photon Uncaging.

    Science.gov (United States)

    Fichte, Manuela A H; Weyel, Xenia M M; Junek, Stephan; Schäfer, Florian; Herbivo, Cyril; Goeldner, Maurice; Specht, Alexandre; Wachtveitl, Josef; Heckel, Alexander

    2016-07-25

    We successfully introduced two-photon-sensitive photolabile groups ([7-(diethylamino)coumarin-4-yl]methyl and p-dialkylaminonitrobiphenyl) into DNA strands and demonstrated their suitability for three-dimensional photorelease. To visualize the uncaging, we used a fluorescence readout based on double-strand displacement in a hydrogel and in neurons. Orthogonal two-photon uncaging of the two cages is possible, thus enabling complex scenarios of three-dimensional control of hybridization with light.

  12. Two-photon cooperative emission in the presence of athermal electromagnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Enaki, N.A.; Mihalache, D

    1997-05-15

    The possibility of cooperative spontaneous two-photon emission of an extended radiators system and the influence of the external thermal electromagnetic field on the spontaneous emission rate, in such a system, are investigated. It is concluded that, in an external electromagnetic field, the two-photon cooperative emission rate increases significantly. The importance of this effect on the emission of gamma rays from inverted long-lived isomers triggered by X-ray thermal fields, is emphasized.

  13. Engineering Two-Atom Thermal Entanglement via Two-Photon Process

    Institute of Scientific and Technical Information of China (English)

    GUO Yan-Qing; ZHOU Ling; SONG He-Shan; YI Xue-Xi

    2004-01-01

    We study that two atoms simultaneously interact with a single mode thermal field via different couplings and different spontaneous emission rates when two-photon process is involved. It is found that we indeed can employ the different couplings to produce the two-atom thermal entanglement in two-photon process. The different atomic spontaneous emission rates are also utilizable in generating thermal entanglement. We also investigate the effect of the can obtain a strong and steady entanglement.

  14. Two-Photon Exchange Corrections to Single Spin Asymmetry of Neutron and 3He

    Institute of Scientific and Technical Information of China (English)

    CHEN Dian-Yong; DONG Yu-Bing

    2011-01-01

    In a simple hadronic model, the two-photon exchange contributions to the single spin asymmetries for the nucleon and the 3He are estimated. The results show that the elastic contributions of two-photon exchange to the single spin asymmetries for the nucleon are rather small while those for the 3He are relatively large. Besides the strong angular dependence, the twophoton contributions to the single spin asymmetry for the 3He are very sensitive to the momentum transfer.

  15. Two-Photon and Second Harmonic Microscopy in Clinical and Translational Cancer Research

    Science.gov (United States)

    PERRY, SETH W.; BURKE, RYAN M.; BROWN, EDWARD B.

    2012-01-01

    Application of two-photon microscopy (TPM) to translational and clinical cancer research has burgeoned over the last several years, as several avenues of pre-clinical research have come to fruition. In this review, we focus on two forms of TPM—two-photon excitation fluorescence microscopy, and second harmonic generation microscopy—as they have been used for investigating cancer pathology in ex vivo and in vivo human tissue. We begin with discussion of two-photon theory and instrumentation particularly as applicable to cancer research, followed by an overview of some of the relevant cancer research literature in areas that include two-photon imaging of human tissue biopsies, human skin in vivo, and the rapidly developing technology of two-photon microendoscopy. We believe these and other evolving two-photon methodologies will continue to help translate cancer research from the bench to the bedside, and ultimately bring minimally invasive methods for cancer diagnosis and treatment to therapeutic reality. PMID:22258888

  16. Diffuse optical characterization of collagen absorption from 500 to 1700 nm

    Science.gov (United States)

    Sekar, Sanathana Konugolu Venkata; Bargigia, Ilaria; Mora, Alberto Dalla; Taroni, Paola; Ruggeri, Alessandro; Tosi, Alberto; Pifferi, Antonio; Farina, Andrea

    2017-01-01

    Reduction in scattering, high absorption, and spectral features of tissue constituents above 1000 nm could help in gaining higher spatial resolution, penetration depth, and specificity for in vivo studies, opening possibilities of near-infrared diffuse optics in tissue diagnosis. We present the characterization of collagen absorption over a broadband range (500 to 1700 nm) and compare it with spectra presented in the literature. Measurements were performed using a time-domain diffuse optical technique. The spectrum was extracted by carefully accounting for various spectral distortion effects, due to sample and system properties. The contribution of several tissue constituents (water, lipid, collagen, oxy, and deoxy-hemoglobin) to the absorption properties of a collagen-rich in vivo bone location, such as radius distal in the 500- to 1700-nm wavelength region, is also discussed, suggesting bone diagnostics as a potential area of interest.

  17. Optical absorption and emission characterization of P3HT: graphene composite for its prospective photovoltaic application

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Joginder, E-mail: jsdevgan.singh@gmail.com; Prasad, Neetu; Nirwal, Varun Singh; Gautam, Khyati; Peta, Koteswara Rao; Bhatnagar, P. K. [Department of Electronic Science, University of Delhi South Campus, Benito Juarez Road, New Delhi, India-110021 (India)

    2016-05-23

    In the present work, regioregular P3HT (Poly (3-hexylthiophene-2, 5-diyl) was blended with graphene nanopowder and the optical spectroscopic characterization of the composite has been performed. It was observed that at low concentration of graphene (up to 0.1 wt %) there is no significant variation in absorption intensity or wavelength range. But at higher concentration (> 0.1 wt %) the absorption intensity starts reducing. Whereas, the photoluminescence of the composite solution quenches as we increase the concentration of graphene. It reveals that charge recombination decreases with increase in concentration (0.05 to 0.5 wt %) of graphene. Therefore 0.1 wt % seems to be the optimized concentration of graphene in the composite for which appropriate quenching of PL was observed without any significant reduction in absorption of photons. Thus maximum efficiency in P3HT: graphene composite photovoltaic cell is expected for 0.1 wt % of graphene concentration in our typical case.

  18. Enhanced two-photon fluorescence imaging and therapy of cancer cells via Gold@bridged silsesquioxane nanoparticles.

    Science.gov (United States)

    Croissant, Jonas; Maynadier, Marie; Mongin, Olivier; Hugues, Vincent; Blanchard-Desce, Mireille; Chaix, Arnaud; Cattoën, Xavier; Wong Chi Man, Michel; Gallud, Audrey; Gary-Bobo, Magali; Garcia, Marcel; Raehm, Laurence; Durand, Jean-Olivier

    2015-01-21

    A two-photon photosensitizer with four triethoxysilyl groups is synthesized through the click reaction. This photosensitizer allows the design of bridged silsesquioxane (BS) nanoparticles through a sol-gel process; moreover, gold core BS shells or BS nanoparticles decorated with gold nanospheres are synthesized. An enhancement of the two-photon properties is noted with gold and the nanoparticles are efficient for two-photon imaging and two-photon photodynamic therapy of cancer cells.

  19. Imaging-guided two-photon excitation-emission-matrix measurements of human skin tissues

    Science.gov (United States)

    Yu, Yingqiu; Lee, Anthony M. D.; Wang, Hequn; Tang, Shuo; Zhao, Jianhua; Lui, Harvey; Zeng, Haishan

    2012-07-01

    There are increased interests on using multiphoton imaging and spectroscopy for skin tissue characterization and diagnosis. However, most studies have been done with just a few excitation wavelengths. Our objective is to perform a systematic study of the two-photon fluorescence (TPF) properties of skin fluorophores, normal skin, and diseased skin tissues. A nonlinear excitation-emission-matrix (EEM) spectroscopy system with multiphoton imaging guidance was constructed. A tunable femtosecond laser was used to vary excitation wavelengths from 730 to 920 nm for EEM data acquisition. EEM measurements were performed on excised fresh normal skin tissues, seborrheic keratosis tissue samples, and skin fluorophores including: NADH, FAD, keratin, melanin, collagen, and elastin. We found that in the stratum corneum and upper epidermis of normal skin, the cells have large sizes and the TPF originates from keratin. In the lower epidermis, cells are smaller and TPF is dominated by NADH contributions. In the dermis, TPF is dominated by elastin components. The depth resolved EEM measurements also demonstrated that keratin structure has intruded into the middle sublayers of the epidermal part of the seborrheic keratosis lesion. These results suggest that the imaging guided TPF EEM spectroscopy provides useful information for the development of multiphoton clinical devices for skin disease diagnosis.

  20. Nanomechanical probing of soft matter through hydrophobic AFM tips fabricated by two-photon polymerization

    Science.gov (United States)

    Suriano, Raffaella; Zandrini, Tommaso; De Marco, Carmela; Osellame, Roberto; Turri, Stefano; Bragheri, Francesca

    2016-04-01

    Atomic force microscopy (AFM) nanoindentation of soft materials is a powerful tool for probing mechanical properties of biomaterials. Though many results have been reported in this field over the last decade, adhesion forces between the tip and the sample hinder the elastic modulus measurement when hydrophilic soft samples are investigated. Here, two-photon polymerization (2PP) technology was used to fabricate hydrophobic perfluoropolyether-based AFM tips. The hydrophobic 2PP tips allowed us to overcome the limitations of commercial and functionalized tips as well as to successfully measure the elastic modulus of medically relevant soft materials in air. Our results obtained in the characterization of poly(dimethyl siloxane) and polyethylene glycol hydrogels showed lower adhesion forces over a larger measurement range when compared to measurements performed with commercial tips. The elastic moduli measured by means of hydrophobic 2PP AFM tips were also found to be comparable to those obtained using conventional techniques for macroscopic samples. We successfully showed that the hydrophobic AFM tips developed by this highly versatile technology enable the study of mechanical properties of soft matter, benefiting from reduced sample-tip interactions, and a custom-made shape and dimension of the tips.

  1. Multispot two-photon imaging of mice heart tissue detecting calcium waves

    Science.gov (United States)

    de Mauro, C.; Cecchetti, C. A.; Alfieri, D.; Borile, G.; Mongillo, M.; Pavone, F. S.

    2012-06-01

    High rate, full field image acquisition in multiphoton imaging is achievable by parallelization of the excitation and of the detection paths. Via a Diffractive Optical Elements (DOEs) which splits a pulsed laser, and a spatial resolved descanned detection path, a new approach to microscopy has been developed. By exploiting the three operating mode, single beam, 16 beamlets or 64 beamlets, the best experimental conditions can be found by adapting the power per beamlet. This Multiphoton Multispot system (MCube) has been characterized in thick tissue samples, and subsequently used for the first time for Ca2+ imaging of acute heart slices. A test sample with fixed mice heart slices with embedded sub-resolution fluorescent beads has been used to test the capability of optical axial resolution up to ~200 microns in depth. Radial and axial resolutions of 0.6 microns and 3 microns have been respectively obtained with a 40X water immersion objective, getting close to the theoretical limit. Then images of heart slices cardiomyocites, loaded with Fluo4-AM have been acquired. The formation of Ca2+ waves during electrostimulated beating has been observed, and the possibility of easily acquire full frame images at 15 Hz (16 beamlets) has been demonstrated, towards the in vivo study of time resolved cellular dynamics and arrhythmia trigger mechanisms in particular. A very high speed two-photon Random Access system for in vivo electrophysiological studies, towards the correlation of voltage and calcium signals in arrhythmia phenomena, is now under developing at Light4tech.

  2. Two-photon excited fluorescence lifetime imaging and spectroscopy of melanins in vitro and in vivo

    Science.gov (United States)

    Krasieva, Tatiana B.; Stringari, Chiara; Liu, Feng; Sun, Chung-Ho; Kong, Yu; Balu, Mihaela; Meyskens, Frank L.; Gratton, Enrico; Tromberg, Bruce J.

    2013-03-01

    Changes in the amounts of cellular eumelanin and pheomelanin have been associated with carcinogenesis. The goal of this work is to develop methods based on two-photon-excited-fluorescence (TPEF) for measuring relative concentrations of these compounds. We acquire TPEF emission spectra (λex=1000 nm) of melanin in vitro from melanoma cells, hair specimens, and in vivo from healthy volunteers. We find that the pheomelanin emission peaks at approximately 615 to 625 nm and eumelanin exhibits a broad maximum at 640 to 680 nm. Based on these data we define an optical melanin index (OMI) as the ratio of fluorescence intensities at 645 and 615 nm. The measured OMI for the MNT-1 melanoma cell line is 1.6±0.22 while the Mc1R gene knockdown lines MNT-46 and MNT-62 show substantially greater pheomelanin production (OMI=0.5±0.05 and 0.17±0.03, respectively). The measured values are in good agreement with chemistry-based melanin extraction methods. In order to better separate melanin fluorescence from other intrinsic fluorophores, we perform fluorescence lifetime imaging microscopy of in vitro specimens. The relative concentrations of keratin, eumelanin, and pheomelanin components are resolved using a phasor approach for analyzing lifetime data. Our results suggest that a noninvasive TPEF index based on spectra and lifetime could potentially be used for rapid melanin ratio characterization both in vitro and in vivo.

  3. Nanomechanical probing of soft matter through hydrophobic AFM tips fabricated by two-photon polymerization.

    Science.gov (United States)

    Suriano, Raffaella; Zandrini, Tommaso; De Marco, Carmela; Osellame, Roberto; Turri, Stefano; Bragheri, Francesca

    2016-04-15

    Atomic force microscopy (AFM) nanoindentation of soft materials is a powerful tool for probing mechanical properties of biomaterials. Though many results have been reported in this field over the last decade, adhesion forces between the tip and the sample hinder the elastic modulus measurement when hydrophilic soft samples are investigated. Here, two-photon polymerization (2PP) technology was used to fabricate hydrophobic perfluoropolyether-based AFM tips. The hydrophobic 2PP tips allowed us to overcome the limitations of commercial and functionalized tips as well as to successfully measure the elastic modulus of medically relevant soft materials in air. Our results obtained in the characterization of poly(dimethyl siloxane) and polyethylene glycol hydrogels showed lower adhesion forces over a larger measurement range when compared to measurements performed with commercial tips. The elastic moduli measured by means of hydrophobic 2PP AFM tips were also found to be comparable to those obtained using conventional techniques for macroscopic samples. We successfully showed that the hydrophobic AFM tips developed by this highly versatile technology enable the study of mechanical properties of soft matter, benefiting from reduced sample-tip interactions, and a custom-made shape and dimension of the tips.

  4. Mapping of hemoglobin in erythrocytes and erythrocyte ghosts using two photon excitation fluorescence microscopy

    Science.gov (United States)

    Bukara, Katarina; Jovanić, Svetlana; Drvenica, Ivana T.; Stančić, Ana; Ilić, Vesna; Rabasović, Mihailo D.; Pantelić, Dejan; Jelenković, Branislav; Bugarski, Branko; Krmpot, Aleksandar J.

    2017-02-01

    The present study describes utilization of two photon excitation fluorescence (2PE) microscopy for visualization of the hemoglobin in human and porcine erythrocytes and their empty membranes (i.e., ghosts). High-quality, label- and fixation-free visualization of hemoglobin was achieved at excitation wavelength 730 nm by detecting visible autofluorescence. Localization in the suspension and spatial distribution (i.e., mapping) of residual hemoglobin in erythrocyte ghosts has been resolved by 2PE. Prior to the 2PE mapping, the presence of residual hemoglobin in the bulk suspension of erythrocyte ghosts was confirmed by cyanmethemoglobin assay. 2PE analysis revealed that the distribution of hemoglobin in intact erythrocytes follows the cells' shape. Two types of erythrocytes, human and porcine, characterized with discocyte and echinocyte morphology, respectively, showed significant differences in hemoglobin distribution. The 2PE images have revealed that despite an extensive washing out procedure after gradual hypotonic hemolysis, a certain amount of hemoglobin localized on the intracellular side always remains bound to the membrane and cannot be eliminated. The obtained results open the possibility to use 2PE microscopy to examine hemoglobin distribution in erythrocytes and estimate the purity level of erythrocyte ghosts in biotechnological processes.

  5. Visualization of laser tattoo removal treatment effects in a mouse model by two-photon microscopy

    Science.gov (United States)

    Jang, Won Hyuk; Yoon, Yeoreum; Kim, Wonjoong; Kwon, Soonjae; Lee, Seunghun; Song, Duke; Choi, Jong Woon; Kim, Ki Hean

    2017-01-01

    Laser tattoo removal is an effective method of eliminating tattoo particles in the skin. However, laser treatment cannot always remove the unwanted tattoo completely, and there are risks of either temporary or permanent side effects. Studies using preclinical animal models could provide detailed information on the effects of laser treatment in the skin, and might help to minimize side effects in clinical practices. In this study, two-photon microscopy (TPM) was used to visualize the laser treatment effects on tattoo particles in both phantom specimens and in vivo mouse models. Fluorescent tattoo ink was used for particle visualization by TPM, and nanosecond (ns) and picosecond (ps) lasers at 532 nm were used for treatment. In phantom specimens, TPM characterized the fragmentation of individual tattoo particles by tracking them before and after the laser treatment. These changes were confirmed by field emission scanning electron microscopy (FE-SEM). TPM was used to measure the treatment efficiency of the two lasers at different laser fluences. In the mouse model, TPM visualized clusters of tattoo particles in the skin and detected their fragmentation after the laser treatment. Longitudinal TPM imaging observed the migration of cells containing tattoo particles after the laser treatment. These results show that TPM may be useful for the assessment of laser tattoo removal treatment in preclinical studies. PMID:28856046

  6. Two-photon brightness of azobenzene photoswitches designed for glutamate receptor optogenetics.

    Science.gov (United States)

    Carroll, Elizabeth C; Berlin, Shai; Levitz, Joshua; Kienzler, Michael A; Yuan, Zhe; Madsen, Dorte; Larsen, Delmar S; Isacoff, Ehud Y

    2015-02-17

    Mammalian neurotransmitter-gated receptors can be conjugated to photoswitchable tethered ligands (PTLs) to enable photoactivation, or photoantagonism, while preserving normal function at neuronal synapses. "MAG" PTLs for ionotropic and metabotropic glutamate receptors (GluRs) are based on an azobenzene photoswitch that is optimally switched into the liganding state by blue or near-UV light, wavelengths that penetrate poorly into the brain. To facilitate deep-tissue photoactivation with near-infrared light, we measured the efficacy of two-photon (2P) excitation for two MAG molecules using nonlinear spectroscopy. Based on quantitative characterization, we find a recently designed second generation PTL, L-MAG0460, to have a favorable 2P absorbance peak at 850 nm, enabling efficient 2P activation of the GluK2 kainate receptor, LiGluR. We also achieve 2P photoactivation of a metabotropic receptor, LimGluR3, with a new mGluR-specific PTL, D-MAG0460. 2P photoswitching is efficiently achieved using digital holography to shape illumination over single somata of cultured neurons. Simultaneous Ca(2+)-imaging reports on 2P photoswitching in multiple cells with high temporal resolution. The combination of electrophysiology or Ca(2+) imaging with 2P activation by optical wavefront shaping should make second generation PTL-controlled receptors suitable for studies of intact neural circuits.

  7. Test of theoretical models for ultrafast heterogeneous electron transfer with femtosecond two-photon photoemission data

    Indian Academy of Sciences (India)

    Lars Gundlach; Tobias Letzig; Frank Willig

    2009-09-01

    The energy distribution of electrons injected into acceptor states on the surface of TiO2 was measured with femtosecond two-photon photoemission. Shape and relative energetic position of these distribution curves with respect to the corresponding donor states, i.e. of perylene chromophores in the first excited singlet state attached via different bridge-anchor groups to the TiO2 surface, were compared with the predictions of different theoretical models for light-induced ultrafast heterogeneous electron transfer (HET). Gerischer’s early scenario for light-induced HET was considered and two recent explicit calculations, i.e. a fully quantum mechanical analytical model and a time-dependent density functional theory model based on molecular dynamics simulations for the vibrational modes were also considered. Based on the known vibrational structure in the photoionization spectrum of perylene in the gas phase and that measured in the linear absorption spectra of the perylene chromophores anchored on the TiO2 surface the energy distribution curves for the injected electrons were fitted assuming the excitation of the dominant 0.17 eV vibrational mode in the ionized perylene chromophore leading to a corresponding Franck-Condon dictated progression in the energy distribution curves. Each individual peak was fitted with a Voigt profile where the Lorentzian contribution was taken from the time-resolved HET data and the Gaussian contribution attributed to inhomogeneous broadening. The measured room temperature energy distribution curves for the injected electrons are explained with the fully quantum mechanical model for light-induced HET with the high energy, 0.17 eV, skeletal stretching mode excited in the ionized perylene chromophore. The corresponding energy distribution of the injected electrons is fully accommodated in acceptor states on the TiO2 surface fulfilling the wide band limit.

  8. Relaxation Process of Excitonic Molecules in CuCl under the Two-Photon Resonant Excitation. II. Transverse Relaxation

    Science.gov (United States)

    Itoh, Tadashi; Katohno, Takashi; Kirihara, Toshio; Ueta, Masayasu

    1984-02-01

    Under the off-resonant excitation at the slightly higher energy side of the giant two-photon absorption band (GTA) for the direct generation of excitonic molecules (EM) in CuCl, new narrow emission bands designated as XT and XL have been found in the energy region of the MT and ML broad bands, respectively. Their photon energies increase with the decrease of the pump photon energy from the higher-energy side of the resonance and finally, at the on-resonant excitation, their bands merge into MT0 and ML0 bands, respectively, previously reported by Mita et al. Based on the detailed studies on these bands, it is found that there exists a certain kind of transverse relaxation process which acts on the EM just after their generation by the GTA and brings about the X emission as a hot luminescence.

  9. Studies of the optical properties of solids. I. Two-photon electroabsorption. II. Electron-hole exchange coupling at L-II, L-III edges

    Energy Technology Data Exchange (ETDEWEB)

    Kolber, Michael Allen

    1978-01-01

    In Chapter I, it is shown that direct-gap covalent semiconductors, such as GaAs, should exhibit electric-field induced Franz-Keldysh-like structures in their two-photon absorption spectra. These structures are evaluated employing exciton theory; the resulting lineshapes are shown to be proportional to the lineshapes for one-photon ''forbidden'' transitions, a property which greatly facilitates computations of the two-photon absorption. In chapter two, exchange mixes the L/sub II/ and L/sub III/ soft x-ray absorption edges of metallic Na, Mg, and Al, affecting the detailed absorption lineshape and the L/sub II//L/sub III/ intensity ratio. The Onodera theory of this mixing is generalized and the requirements of particle conservation and causality lead to significant modifications of the theoretical absorption lineshape. It is shown that under certain conditions an exchange-free lineshape can be extracted from experimental data for comparison with non-asymptotic theories of x-ray edges.

  10. Two-photon sensitized visible and near-IR luminescence of lanthanide complexes using a fluorene-based donor-π-acceptor diketonate.

    Science.gov (United States)

    Woodward, Adam W; Frazer, Andrew; Morales, Alma R; Yu, Jin; Moore, Anthony F; Campiglia, Andres D; Jucov, Evgheni V; Timofeeva, Tatiana V; Belfield, Kevin D

    2014-11-28

    A fluorene-based donor-acceptor ligand was successfully employed to sensitize visible and near-IR emitting lanthanide centers. The ligand construct is based on a donor-π-acceptor architecture with diphenylamino acting as the donor and a fluorenyl π bridge derivatized with a trifluoroacetonate moiety acting as both a strong acceptor and the classic bidentate scaffold for complexing metals. (1)H NMR analysis in the polar solvents THF and CDCl3 revealed the enolic form of the diketone dominant in solution equilibria at room temperature. This preferred cis-enol form binds strongly to the lanthanide(III) ions (Ln = Eu, Sm, Dy, Tb, Yb, Nd, Er, and Gd) in the presence of phenanthroline affording the resulting ternary tris(diketonates) complexes with 1,10-phenanthroline. Detailed characterization of these complexes was conducted, with particular emphasis on linear and nonlinear photophysical properties. Steady-state and time-resolved emission spectroscopy and overall photoluminescence quantum yield (PLQY) measurements were performed on all the complexes. Sizeable visible and near-IR efficiency for europium (room temperature, visible), samarium (low temperature, visible) and ytterbium, neodymium and erbium (room temperature, near-IR) was displayed, with long luminescent lifetimes for the europium and samarium complexes of 85 and 70 μs, respectively Measurement of the luminescence decay for the Yb complex at 976 nm, Nd complex at 874 nm, and Er complex at 1335 nm yielded mono-exponential decay curves, with lifetimes of ~13 μs, ~1.6 μs, and ~2.5 μs, respectively, inferring that the emission was generated by a single species. In addition, fluorescence anisotropy and two-photon absorption (2PA) spectra (via Z-scan) were obtained for the ligand and europium complex, revealing a maximum 2PA cross section of 340 GM for the latter upon excitation at 760 nm. A quadratic relationship was found by varying laser excitation power vs. luminescence intensity of the europium complex

  11. Light-harvesting ytterbium(III)-porphyrinate-BODIPY conjugates: synthesis, excitation-energy transfer, and two-photon-induced near-infrared-emission studies.

    Science.gov (United States)

    Zhang, Tao; Zhu, Xunjin; Wong, Wai-Kwok; Tam, Hoi-Lam; Wong, Wai-Yeung

    2013-01-07

    Based on a donor-acceptor framework, several conjugates have been designed and prepared in which an electron-donor moiety, ytterbium(III) porphyrinate (YbPor), was linked through an ethynyl bridge to an electron-acceptor moiety, boron dipyrromethene (BODIPY). Photoluminescence studies demonstrated efficient energy transfer from the BODIPY moiety to the YbPor counterpart. When conjugated with the YbPor moiety, the BODIPY moiety served as an antenna to harvest the lower-energy visible light, subsequently transferring its energy to the YbPor counterpart, and, consequently, sensitizing the Yb(III) emission in the near-infrared (NIR) region with a quantum efficiency of up to 0.73% and a lifetime of around 40 μs. Moreover, these conjugates exhibited large two-photon-absorption cross-sections that ranged from 1048-2226 GM and strong two-photon-induced NIR emission.

  12. Characterizing trace metal impurities in optical waveguide materials using x-ray absorption

    Energy Technology Data Exchange (ETDEWEB)

    Citrin, P.H.; Northrup, P.A.; Atkins, R.M.; Niu, L.; Marcus, M.A.; Jacobson, D.C. [Lucent Technologies, Murray Hill, NJ (United States). Bell Labs.; Glodis, P.F. [Lucent Technologies, Norcross, GA (United States). Bell Labs.

    1998-12-31

    X-ray absorption measurements are described for identifying metal impurities in silica preforms, the rod-like starting materials from which hair-like optical fibers are drawn. The results demonstrate the effectiveness of this approach as a non-destructive, quantitative, element-selective, position-sensitive, and chemical-state-specific means for characterizing transition metals in the concentration regime of parts per billion.

  13. One- and two-photon induced fluorescence spectroscopy enabling the detection of localized aflatoxin contamination in individual maize kernels

    Science.gov (United States)

    Smeesters, L.; Meulebroeck, W.; Raeymaekers, S.; Thienpont, H.

    2016-04-01

    The presence of carcinogenic aflatoxins in food and feed products is a major worldwide problem. To date, the aflatoxin contamination can only be detected by the use of destructive sample-based chemical analyses. Therefore, we developed an optical setup able to detect the localized aflatoxin contamination in individual maize kernels, on the basis of one- and two- photon induced fluorescence spectroscopy. Our developed optical configuration comprises a tunable titanium-sapphire laser (710nm-830nm) in combination with second harmonic wavelength generation (355nm-415nm), enabling the measurement of both one- and two-photon induced fluorescence spectra. Moreover, an accurate scanning of the kernel's surface was induced by the use of automated translation stages, allowing to study the localized maize contamination. First, the operation of the setup is validated by the characterization of pure aflatoxin B1 powder. Second, the fluorescence spectra of healthy (maize kernels (>70ppb aflatoxin B1) were measured, after excitation with 365nm, 730nm, 750nm and 780nm. For both the one- and two- photon induced fluorescence processes, the presence of the aflatoxin inside the contaminated maize kernels influenced the intrinsic fluorescence signals. Based on the fluorescence spectrum between 400nm and 550nm, we defined a detection criterion to identify the contaminated maize kernels. Furthermore, we demonstrate the sensing of the localized contamination level, indicating both contaminated maize kernels with a high contamination level in a limited surface area (as small as 1mm2) as with a lower contamination spread over a large surface area (up to 20mm2). As a result, our developed measurement methodology allows the identification of the localized aflatoxin contamination, paving the way to the non-destructive, real-time and high-sensitive industrial scanning-based detection of aflatoxins in food products.

  14. Note: Derivation of two-photon circular dichroism - Addendum to "two-photon circular dichroism" [J. Chem. Phys. 62, 1006 (1975)

    OpenAIRE

    Friese, Daniel Henrik

    2015-01-01

    Published version, also available at http://dx.doi.org/10.1063/1.4930017 This addendum shows the detailed derivation of the fundamental equations for two-photon circular dichroism which are given in a very condensed form in the original publication [I. Tinoco, J. Chem. Phys. 62, 1006 (1975)]. In addition, some minor errors are corrected and some of the derivations in the original publication are commented.

  15. Dispersion-tolerant two-photon Michelson interferometer using telecom-band frequency-entangled photon pairs generated by spontaneous parametric downconversion

    Science.gov (United States)

    Yoshizawa, Akio; Fukuda, Daiji; Tsuchida, Hidemi; Yamamoto, Noritsugu

    2015-05-01

    The chromatic group velocity dispersion tolerance of a fiber-optic two-photon interferometer is characterized for telecom-band photon pairs that are frequency entangled. Two indium-gallium-arsenide single-photon detectors are used to record the coincidence counts. A single-wavelength laser diode continuously pumps a periodically poled lithium niobate waveguide of 1-mm length. For near-degenerate spontaneous parametric downconversion, it generates wideband entangled collinear photon pairs. The spectral width of 115.8 nm is centered at 1550 nm. It is restricted by the performance of the single-photon detectors whose efficiency is poor beyond 1610 nm. Using a Michelson interferometer, two-photon interference signals are recorded with and without frequency entanglement. The frequency-entangled photon pairs are found to exhibit dispersion-tolerant two-photon interference, even though the two paths through the interferometer have different group velocity dispersion. The observed two-photon interference signal has a correlation time of 42.7 fs, in good agreement with calculations for a 115.8-nm spectral width. For comparison, results are also presented for photon pairs lacking frequency entanglement.

  16. Near infrared two-photon excitation cross-sections of voltage-sensitive dyes.

    Science.gov (United States)

    Fisher, Jonathan A N; Salzberg, Brian M; Yodh, Arjun G

    2005-10-15

    Microscopy based on voltage-sensitive dyes has proven effective for revealing spatio-temporal patterns of neuronal activity in vivo and in vitro. Two-photon microscopy using voltage-sensitive dyes offers the possibility of wide-field visualization of membrane potential on sub-cellular length scales, hundreds of microns below the tissue surface. Very little information is available, however, about the utility of voltage-sensitive dyes for two-photon imaging purposes. Here we report on measurements of two-photon fluorescence excitation cross-sections for nine voltage-sensitive dyes in a solvent, octanol, intended to simulate the membrane environment. Ultrashort light pulses from a Ti:sapphire laser were used for excitation from 790 to 960 nm, and fluorescein dye was used as a calibration standard. Overall, dyes RH795, RH421, RH414, di-8-ANEPPS, and di-8-ANEPPDHQ had the largest two-photon excitation cross-sections ( approximately 15 x 10(-50)cm4 s photon(-1)) in this wavelength region and are therefore potentially useful for two-photon microscopy. Interestingly, di-8-ANEPPDHQ, a chimera constructed from the potentiometric dyes RH795 and di-8-ANEPPS, exhibited larger cross-sections than either of its constituents.

  17. New advances in the use of infrared absorption spectroscopy for the characterization of heterogeneous catalytic reactions.

    Science.gov (United States)

    Zaera, Francisco

    2014-11-21

    Infrared absorption spectroscopy has proven to be one of the most powerful spectroscopic techniques available for the characterization of catalytic systems. Although the history of IR absorption spectroscopy in catalysis is long, the technique continues to provide key fundamental information about a variety of catalysts and catalytic reactions, and to also offer novel options for the acquisition of new information on both reaction mechanisms and the nature of the solids used as catalysts. In this review, an overview is provided of the main contributions that have been derived from IR absorption spectroscopy studies of catalytic systems, and a discussion is included on new trends and new potential directions of research involving IR in catalysis. We start by briefly describing the power of Fourier-transform IR (FTIR) instruments and the main experimental IR setups available, namely, transmission (TIR), diffuse reflectance (DRIFTS), attenuated total reflection (ATR-IR), and reflection-absorption (RAIRS), for advancing research in catalysis. We then discuss the different environments under which IR characterization of catalysts is carried out, including in situ and operando studies of typical catalytic processes in gas-phase, research with model catalysts in ultrahigh vacuum (UHV) and so-called high-pressure cell instruments, and work involving liquid/solid interfaces. A presentation of the type of information extracted from IR data follows in terms of the identification of adsorbed intermediates, the characterization of the surfaces of the catalysts themselves, the quantitation of IR intensities to extract surface coverages, and the use of probe molecules to identify and titrate specific catalytic sites. Finally, the different options for carrying out kinetic studies with temporal resolution such as rapid-scan FTIR, step-scan FTIR, and the use of tunable lasers or synchrotron sources, and to obtain spatially resolved spectra, by sample rastering or by 2D imaging, are

  18. The Application of Atomic Absorption Spectroscopy and Optical Microscopy to the Characterization of Sized Airborne Particulate in Dayton, Ohio.

    Science.gov (United States)

    1978-01-01

    PERIOD COVERED " AneT Appication of Atomic Absorption Spectroscopy ’ and Optical Microscopy to the Characterization of THESIS/DISSERTATION 4 Sized...1978 U I HEREBY REC04MEND THAT THE THESIS PREPARED ’NDER MY SUPERVISION BY Lorelei Ann Krebs ENTITLED The Application of Atomic Absorption Spectroscopy and...acid and diluted with distilled water in a 25 milliliter volumetric flask. Atomic absorption . spectroscopy was used to analyze the solutions for

  19. Visualization of two-photon Rabi oscillations in evanescently coupled optical waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Ornigotti, M; Valle, G Della; Fernandez, T Toney; Laporta, P; Longhi, S [Dipartimento di Fisica and Istituto di Fotonica e Nanotecnologie del CNR, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano (Italy); Coppa, A; Foglietti, V [Istituto di Fotonica e Nanotecnologie del CNR, sezione di Roma, Via Cineto Romano 42, 00156 Roma (Italy)], E-mail: longhi@fisi.polimi.it

    2008-04-28

    An optical analogue of two-photon Rabi oscillations, occurring in a three-level atomic or molecular system coherently driven by two detuned laser fields, is theoretically proposed and experimentally demonstrated using three evanescently coupled optical waveguides realized on an active glass substrate. The optical analogue stems from the formal analogy between spatial propagation of light waves in the three-waveguide structure and the coherent temporal evolution of populations in a three-level atomic medium driven by two laser fields under two-photon resonance. In our optical experiment, two-photon Rabi oscillations are thus visualized as a slow spatial oscillatory exchange of light power between the two outer waveguides of the structure with a small excitation of the central waveguide.

  20. Selective two-photon excitation of a vibronic state by correlated photons.

    Science.gov (United States)

    Oka, Hisaki

    2011-03-28

    We theoretically investigate the two-photon excitation of a molecular vibronic state by correlated photons with energy anticorrelation. A Morse oscillator having three sets of vibronic states is used, as an example, to evaluate the selectivity and efficiency of two-photon excitation. We show that a vibrational mode can be selectively excited with high efficiency by the correlated photons, without phase manipulation or pulse-shaping techniques. This can be achieved by controlling the quantum correlation so that the photon pair concurrently has two pulse widths, namely, a temporally narrow width and a spectrally narrow width. Though this concurrence is seemingly contradictory, we can create such a photon pair by tailoring the quantum correlation between two photons.

  1. Observation of single- and two-photon beating between independent Raman scattering

    CERN Document Server

    Chen, Li-Qing; Zhang, Guo-Wan; Ou, Z Y; Zhang, Weiping

    2010-01-01

    By using spontaneous Raman processes in the high gain regime, we produce two independent Raman Stokes fields from an atomic ensemble. Temporal beating is observed between the two directly generated Stokes fields in a single realization. The beat frequency is found to be a result of an AC Stark frequency shift effect. However, due to the spontaneous nature of the process, the phases of the two Stokes fields change from one realization to another so that the beat signal disappears after average over many realizations. On the other hand, the beat signal is recovered in a two-photon correlation measurement, showing a two-photon interference effect. The two-photon beat signal enables us to obtain dephasing information in the Raman process. The dephasing effect is found to depend on the temperature of the atomic medium.

  2. Enhanced-locality fiber-optic two-photon-fluorescence live-brain interrogation

    Energy Technology Data Exchange (ETDEWEB)

    Fedotov, I. V.; Doronina-Amitonova, L. V. [International Laser Center, Physics Department, M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Russian Quantum Center, ul. Novaya 100, Skolkovo, Moscow Region 1430125 (Russian Federation); Kurchatov Institute National Research Center, Moscow (Russian Federation); Sidorov-Biryukov, D. A.; Fedotov, A. B. [International Laser Center, Physics Department, M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Russian Quantum Center, ul. Novaya 100, Skolkovo, Moscow Region 1430125 (Russian Federation); Anokhin, K. V. [Kurchatov Institute National Research Center, Moscow (Russian Federation); P.K. Anokhin Institute of Normal Physiology, Russian Academy of Medical Sciences, Moscow (Russian Federation); Kilin, S. Ya. [B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus); Sakoda, K. [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Zheltikov, A. M. [International Laser Center, Physics Department, M.V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Russian Quantum Center, ul. Novaya 100, Skolkovo, Moscow Region 1430125 (Russian Federation); Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States); Center of Photochemistry, Russian Academy of Sciences, ul. Novatorov 7a, Moscow 117421 (Russian Federation)

    2014-02-24

    Two-photon excitation is shown to substantially enhance the locality of fiber-based optical interrogation of strongly scattering biotissues. In our experiments, a high-numerical-aperture, large-core-are fiber probe is used to deliver the 200-fs output of a 100-MHz mode-locked ytterbium fiber laser to samples of live mouse brain, induce two-photon fluorescence of nitrogen–vacancy centers in diamond markers in brain sample. Fiber probes with a high numerical aperture and a large core area are shown to enable locality enhancement in fiber-laser–fiber-probe two-photon brain excitation and interrogation without sacrificing the efficiency of fluorescence response collection.

  3. Two-photon calcium imaging in mice navigating a virtual reality environment.

    Science.gov (United States)

    Leinweber, Marcus; Zmarz, Pawel; Buchmann, Peter; Argast, Paul; Hübener, Mark; Bonhoeffer, Tobias; Keller, Georg B

    2014-02-20

    In recent years, two-photon imaging has become an invaluable tool in neuroscience, as it allows for chronic measurement of the activity of genetically identified cells during behavior(1-6). Here we describe methods to perform two-photon imaging in mouse cortex while the animal navigates a virtual reality environment. We focus on the aspects of the experimental procedures that are key to imaging in a behaving animal in a brightly lit virtual environment. The key problems that arise in this experimental setup that we here address are: minimizing brain motion related artifacts, minimizing light leak from the virtual reality projection system, and minimizing laser induced tissue damage. We also provide sample software to control the virtual reality environment and to do pupil tracking. With these procedures and resources it should be possible to convert a conventional two-photon microscope for use in behaving mice.

  4. Three-dimensional protein networks assembled by two-photon activation.

    Science.gov (United States)

    Gatterdam, Volker; Ramadass, Radhan; Stoess, Tatjana; Fichte, Manuela A H; Wachtveitl, Josef; Heckel, Alexander; Tampé, Robert

    2014-05-26

    Spatial and temporal control over chemical and biological processes plays a key role in life and material sciences. Here we synthesized a two-photon-activatable glutathione (GSH) to trigger the interaction with glutathione S-transferase (GST) by light at superior spatiotemporal resolution. The compound shows fast and well-confined photoconversion into the bioactive GSH, which is free to interact with GST-tagged proteins. The GSH/GST interaction can be phototriggered, changing its affinity over several orders of magnitude into the nanomolar range. Multiplexed three-dimensional (3D) protein networks are simultaneously generated in situ through two-photon fs-pulsed laser-scanning excitation. The two-photon activation facilitates the three-dimensional assembly of protein structures in real time at hitherto unseen resolution in time and space, thus opening up new applications far beyond the presented examples.

  5. Polarization properties of optical phase conjugation by two-photon resonant degenerate four-wave mixing

    Science.gov (United States)

    Kauranen, Martti; Gauthier, Daniel J.; Malcuit, Michelle S.; Boyd, Robert W.

    1989-08-01

    We develop a semiclassical theory of the polarization properties of phase conjugation by two-photon resonant degenerate four-wave mixing. The theory includes the effects of saturation by the pump waves. We solve the density-matrix equations of motion in steady state for a nonlinear medium consisting of stationary atoms with a ground and excited state connected by two-photon transitions. As an illustration of the general results, we consider an S0-->S0 two-photon transition, which is known to lead to perfect polarization conjugation in the limit of third-order theory. We show that the fidelity of the polarization-conjugation process is degraded for excessively large pump intensities. The degradation can occur both due to transfer of population to the excited state and due to nonresonant Stark shifts. Theoretical results are compared to those of a recent experiment [Malcuit, Gauthier, and Boyd, Opt. Lett. 13, 663 (1988)].

  6. Scanless functional imaging of hippocampal networks using patterned two-photon illumination through GRIN lenses

    KAUST Repository

    Moretti, Claudio

    2016-09-12

    Patterned illumination through the phase modulation of light is increasingly recognized as a powerful tool to investigate biological tissues in combination with two-photon excitation and light-sensitive molecules. However, to date two-photon patterned illumination has only been coupled to traditional microscope objectives, thus limiting the applicability of these methods to superficial biological structures. Here, we show that phase modulation can be used to efficiently project complex two-photon light patterns, including arrays of points and large shapes, in the focal plane of graded index (GRIN) lenses. Moreover, using this approach in combination with the genetically encoded calcium indicator GCaMP6, we validate our system performing scanless functional imaging in rodent hippocampal networks in vivo ~1.2 mm below the brain surface. Our results open the way to the application of patterned illumination approaches to deep regions of highly scattering biological tissues, such as the mammalian brain.

  7. Robust spatial-polarization hyperentanglement distribution of two-photon systems against collective noise

    Science.gov (United States)

    Gao, Cheng-Yan; Wang, Guan-Yu; Alzahrani, Faris; Hobiny, Aatef; Deng, Fu-Guo

    2017-03-01

    Hyperentanglement is a significant resource for high-capacity quantum communication. Here we present a robust spatial-polarization hyperentanglement distribution scheme for two-photon systems. The error on the polarization states of two-photon systems transmitted from two paths can be corrected resorting to the robust time-bin entanglement which suffers little from the channel noise. The spatial bit-flip error takes place with a very small probability and the spatial phase-flip error can be precluded by adjusting the path-length of spatial modes. Using this scheme, the two parties in quantum communication can share a maximally hyperentangled state of two-photon systems in a deterministic way, which will improve the efficiency of quantum communication largely.

  8. Automated image analysis for diameters and branching points of cerebral penetrating arteries and veins captured with two-photon microscopy.

    Science.gov (United States)

    Sugashi, Takuma; Yoshihara, Kouichi; Kawaguchi, Hiroshi; Takuwa, Hiroyuki; Ito, Hiroshi; Kanno, Iwao; Yamada, Yukio; Masamoto, Kazuto

    2014-01-01

    The present study was aimed to characterize 3-dimensional (3D) morphology of the cortical microvasculature (e.g., penetrating artery and emerging vein), using two-photon microscopy and automated analysis for their cross-sectional diameters and branching positions in the mouse cortex. We observed that both artery and vein had variable cross-sectional diameters across cortical depths. The mean diameter was similar for both artery (17 ± 5 μm) and vein (15 ± 5 μm), and there were no detectable differences over depths of 50-400 μm. On the other hand, the number of branches was slightly increased up to 400-μm depth for both the artery and vein. The mean number of branches per 0.1 mm vessel length was 1.7 ± 1.2 and 3.8 ± 1.6 for the artery and vein, respectively. This method allows for quantification of the large volume data of microvascular images captured with two-photon microscopy. This will contribute to the morphometric analysis of the cortical microvasculature in functioning brains.

  9. Tunable structures comprising two photonic crystal slabs--optical study in view of multi-analyte enhanced detection.

    Science.gov (United States)

    Shi, Lina; Pottier, Pierre; Skorobogatiy, Maksim; Peter, Yves-Alain

    2009-06-22

    Using finite-difference time-domain method, we characterize the normal-incidence transmission properties of a two slab photonic crystal device in a view of its applications in fluorescence enhancement and multi-analyte detection. Individual slabs consist of a square or a triangular lattice of air holes embedded into a silicon nitride slab. The geometrical parameters are chosen so that the individual slabs operate in a guided resonance regime where strong reflectivity under the normal incidence angle is observed in a broad spectral range. When placed in the close proximity of each other, the two photonic crystal slab system exhibits a narrow Fabry-Perot type transmission peak corresponding to the excitation of a resonant mode in the cavity formed by the two slabs. We then study the effects of the size of the air gap between the two photonic crystal slabs on the spectral position and bandwidth of a resonance transmission peak. Finally, we investigate the electromagnetic energy distributions at the wavelength of a transmission resonance in the double slab photonic crystals. As a final result we demonstrate that this structure can provide electric field enhancement at the slab surface, which can be used for fluorescence enhancement.

  10. One- and two-photon scattering from generalized V-type atoms

    OpenAIRE

    Sánchez-Burillo, Eduardo; Martín-Moreno, Luis; Zueco, David; García-Ripoll, Juan José

    2016-01-01

    The one- and two-photon scattering matrix S is obtained analytically for a one-dimensional waveguide and a point-like scatterer with N excited levels (generalized V -type atom). We argue that the two-photon scattering matrix contains sufficient information to distinguish between different level structures which are equivalent for single-photon scattering, such as a V -atom with N = 2 excited levels and two two-level systems. In particular, we show that the scattering with the V -type atom exh...

  11. A direct frequency comb for two-photon transition spectroscopy in a cesium vapor

    Institute of Scientific and Technical Information of China (English)

    Zhang Yi-Chi; Wu Ji-Zhou; Li Yu-Qing; Jin Li; Ma Jie; Wang Li-Rong; Zhao Yan-Ting; Xiao Lian-Tuan; Jia Suo-Tang

    2012-01-01

    A phase-stabilized femtosecond frequency comb is used to measure high-resolution spectra of two-photon transition 62S1/2-62P1/2,3/2-82S1/2 in a cesium vapor.The broadband laser output from a femtosecond frequency comb is split into counter-propagating parts,shaped in an original way,and focused into a room-temperature cesium vapor.We obtain high-resolution two-photon spectroscopy by scanning the repetition rate of femtosecond frequency comb,and through absolute frequency measurements.

  12. Manipulation of multiple electromagnetically induced two-photon transparency in a six-level atomic system

    Institute of Scientific and Technical Information of China (English)

    Jia Wen-Zhi; Wang Shun-Jin

    2009-01-01

    In the five-level K-type atomic system, by using another control field to couple the excited level of the coupling transition to the sixth higher excited level, a six-level atomic system is constructed. In this system, the multiple electromagnetically induced two-photon transparency has been investigated. What is more, if choosing the parameters of the control fields properly the triple transparency window will reduce to a double one which means that the multiple electromagnetically induced two-photon transparency can be manipulated in this system. The physical interpretation of these phenomena is given in terms of the dressed states and the dark states.

  13. Insights into esophagus tissue architecture using two-photon confocal microscopy

    Science.gov (United States)

    Liu, Nenrong; Wang, Yue; Feng, Shangyuan; Chen, Rong

    2013-08-01

    In this paper, microstructures of human esophageal mucosa were evaluated using the two-photon laser scanning confocal microscopy (TPLSCM), based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG). The distribution of epithelial cells, muscle fibers of muscularis mucosae has been distinctly obtained. Furthermore, esophageal submucosa characteristics with cancer cells invading into were detected. The variation of collagen, elastin and cancer cells is very relevant to the pathology in esophagus, especially early esophageal cancer. Our experimental results indicate that the MPM technique has the much more advantages for label-free imaging, and has the potential application in vivo in the clinical diagnosis and monitoring of early esophageal cancer.

  14. Axial range of conjugate adaptive optics in two-photon microscopy

    CERN Document Server

    Paudel, Hari P; Mertz, Jerome; Bifano, Thomas

    2015-01-01

    We describe an adaptive optics technique for two-photon microscopy in which the deformable mirror used for aberration compensation is positioned in a plane conjugate to the plane of the aberration. We demonstrate in a proof-of-principle experiment that this technique yields a large field of view advantage in comparison to standard pupil-conjugate adaptive optics. Further, we show that the extended field of view in conjugate AO is maintained over a relatively large axial translation of the deformable mirror with respect to the conjugate plane. We conclude with a discussion of limitations and prospects for the conjugate AO technique in two-photon biological microscopy.

  15. Two-photon luminescence microscopy of field enhancement at gold nanoparticles

    DEFF Research Database (Denmark)

    Beermann, Jonas; Bozhevolnyi, Sergey I.

    2005-01-01

    Using a reflection scanning optical microscope detecting two-photon luminescence (TPL) we have imaged square gold bumps positioned in a periodic array either on a smooth gold film or directly on a glass substrate. The second-harmonic (SH) and TPL response from these structures show both polarizat......Using a reflection scanning optical microscope detecting two-photon luminescence (TPL) we have imaged square gold bumps positioned in a periodic array either on a smooth gold film or directly on a glass substrate. The second-harmonic (SH) and TPL response from these structures show both...

  16. Two-photon laser fabrication of three-dimensional silver microstructures with submicron scale linewidth

    Energy Technology Data Exchange (ETDEWEB)

    Tsutsumi, Naoto; Nagata, Kazuya; Sakai, Wataru [Kyoto Institute of Technology, Department of Macromolecular Science and Engineering, Graduate School of Science and Technology, Kyoto (Japan)

    2011-05-15

    We show three-dimensional silver microstructures with a submicron scale linewidth fabricated via two-photon photoreduction of silver ions in a poly(N-vinylpyrrolidone) (PVP) matrix. Femtosecond laser at 508 nm directly excites the carbonyl group of PVP via two-photon excitation to reduce silver ions. Lone pair electrons in PVP stabilized silver ions and lower molecular weight of PVP prevented silver clusters growing larger. The effect of molecular weight of PVP on linewidth of silver nanowire is investigated. (orig.)

  17. Threshold Property of Photoresist Film for Two-photon Optical Memory

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jiangying; MING Hai; LIANG Zhongcheng; WANG Pei; XIE Jianping; XIE Aifang; ZHANG Zebo

    2001-01-01

    Two-photon threshold property of photoresist films have been studied by changing exposure energy. When photoresist film is irradiated by Ti∶Sapphire laser with wavelength 770 nm, pulse width 130 fs, repetition rate 82 MHz, the damage and recording thresholds of the material are 9.15×105 J/cm2 and below 5.57×105 J/cm2, respectively. The principle experiments of two-photon optical memory are demonstrated in photoresist film. The patterns of optical bit data storage are realized at different input power density. The corresponding 3-D tomographies of these recorded spots are scanned under near-field optical microscope.

  18. Two-photon photoemission from metals induced by picosecond laser pulses

    Science.gov (United States)

    Bechtel, J. H.; Smith, W. L.; Bloembergen, N.

    1977-01-01

    We have measured the two-photon photoemission current density from tungsten, tantalum, and molybdenum when irradiated by 532-nm wavelength radiation. This wavelength was produced by the second-harmonic radiation of single picosecond laser pulses from a mode-locked neodymium-doped yttrium-aluminum-garnet laser. The results are interpreted in terms of both a simple temperature-independent two-photon photoemission effect and a generalization of the Fowler-DuBridge theory of photoemission. The laser polarization dependence of the emitted current is also reported.

  19. Two-photon quantum walks in an elliptical direct-write waveguide array

    CERN Document Server

    Owens, J O; Biggerstaff, D N; Goggin, M E; Fedrizzi, A; Linjordet, T; Ams, M; Marshall, G D; Twamley, J; Withford, M J; White, A G

    2011-01-01

    Integrated optics provides an ideal test bed for the emulation of quantum systems via continuous-time quantum walks. Here we study the evolution of two-photon states in an elliptic array of waveguides. We characterise the photonic chip via coherent-light tomography and use the results to predict distinct differences between temporally indistinguishable and distinguishable two-photon inputs which we then compare with experimental observations. Our work highlights the feasibility for emulation of coherent quantum phenomena in three-dimensional waveguide structures.

  20. THE TWO-PHOTON DEGENERATE JAYNES-CUMMINGS MODEL WITH AND WITHOUT ROTATING-WAVE APPROXIMATION

    Institute of Scientific and Technical Information of China (English)

    ZHOU LING; SONG HE-SHAN; YAO LI

    2001-01-01

    We take into account the two-photon process and generalize the Jaynes-Cummings (JC) model to the case of atomic level degenerate in the projections of the angular momenta, and we establish two-photon degenerate JC models with and without the rotating-wave approximation (RWA) quantum theory. Comparing the atom population inversion of the generalized JC model with that of the original JC model, we found that the revival period of the degenerate JC model becomes longer and the maximum amplitude of atomic inversion decreases with RWA. Without RWA, the quantum chaos of the generalized JC model is much weaker than that of the original JC model