Sample records for excitation laser radiation

  1. LASERS: Atomic xenon recombination laser excited by thermal ionizing radiation from a magnetoplasma compressor and discharge (United States)

    Kamrukov, A. S.; Kozlov, N. P.; Opekan, A. G.; Protasov, Yu S.; Rudoĭ, I. G.; Soroka, A. M.


    A description is given and the results are reported of the first photoionization-recombination laser using atomic xenon excited by thermal ionizing radiation from a plasma. The pump source was a multichannel plasmadynamic discharge in magnetoplasma compressors, which was ignited in the active medium of the laser. When the composition of the working mixture was optimal (Xe:Ar = 1:250) and the total pressure was 1 atm, the output energy was ~ 0.5 J in the form of pulses of ~ 10 μs duration and the maximum specific output energy represented by laser radiation was 1-2 J/liter. The unsaturated gain was 27 m - 1. A kinetic laser scheme was proposed and analyzed. It allowed for the processes of photoionization, ion conversion, dissociative recombination, interaction of excited states with electron and buffer gases, etc. An important role played by heating of the active medium during pumping was demonstrated and it explained the observed characteristics of the spatial and temporal structure of the lasing process, particularly bleaching of large volumes of the active medium. The potential output energy of the laser was considered and specific constructions were proposed to attain a lasing efficiency amounting to a few percent.

  2. Radiative processes in air excited by an ArF laser (United States)

    Laufer, Gabriel; Mckenzie, Robert L.; Huo, Winifred M.


    The emission spectrum of air that is excited by an ArF laser has been investigated experimentally and theoretically to determine the conditions under which fluorescence from O2 can be used for the measurement of temperature in aerodynamic flows. In addition to the expected fluorescence from O2, the spectrum from excitation with an intense laser beam is shown to contain significant contributions from the near-resonant Raman fundamental and overtone bands, the four-photon fluorescence excitation of C produced from ambient CO2, and possibly the three-photon excitation of O(2+). The nature of the radiative interactions contributing to these additional features is described.

  3. Coherent phase control of excitation of atoms by bichromatic laser radiation in an electric field

    NARCIS (Netherlands)

    Astapenko, VA

    A new method for coherent phase control of excitation of atoms in a discrete spectrum under the action of bichromatic laser radiation with the frequency ratio 1 : 2 is analysed. An important feature of this control method is the presence of a electrostatic field, which removes the parity selection

  4. Atomic xenon recombination laser excited by thermal ionizing radiation from a magnetoplasma compressor and discharge (United States)

    Kamrukov, A. S.; Kozlov, Nicolay P.; Opekan, A. G.; Protasov, Yuri S.; Rudoi, I. G.; Soroka, A. M.


    A description is given and the results are reported of the first photoionization-recombination laser using atomic xenon excited by thermal ionizing radiation from a plasma. The pump source was a multichannel plasmadynamic in magnetoplasma compressors, which was ignited in the active medium of the laser. When the composition of the working mixture was optimal (Xe:Ar equals 1:250) and the total pressure was 1 atm, the output energy was approximately 0.5 in the form of pulses of approximately 10 microsecond(s) duration, and maximum specific output energy represented by laser radiation was 1-2 J/l. The unsaturated gain was 27 m. A kinetic laser scheme was proposed and analyzed. It allowed for the processes of photoionization, ion conversion, dissociative recombination, interaction of excited states with electron and buffer gases, etc. An important role played by heating of the active medium during pumping was demonstrated; it explained the observed characteristics of the spatial and temporal structure of the lasing process, particularly bleaching of large volumes of the active medium. The potential output energy of the laser was considered, and specific constructions were proposed to attain a lasing efficiency amounting to a few percent.

  5. BRIEF COMMUNICATIONS: Bleaching-wave laser excited by radiation from magnetoplasma compressors (United States)

    Kamrukov, A. S.; Logunov, O. A.; Ovchinnikov, P. A.; Protasov, Yu S.; Startsev, Aleksandr V.; Stoĭlov, Yu Yu


    A bleaching-wave laser (utilizing an ether solution of coumarin 6 and 1,4-diphenylbutadiene) was pumped by a flashlamp-type source utilizing magnetoplasma compressors. When the bleaching wave propagated in the solution at a velocity of ~ 1 km/s, cw lasing was obtained for 30-40 μs with an output energy of 1.2 J in the 517 ± 5 nm range. Estimates were made of the threshold pump intensity and of the internal losses in the bleaching-wave laser. It was found that, compared with a laser without a bleaching wave (utilizing an ethyl solution of coumarin 6), a bleaching wave improved greatly (under the same excitation conditions) the output energy and the directionality of the radiation.

  6. Directed high-power THz radiation from transverse laser wakefield excited in an electron density filament (United States)

    Kalmykov, Serge; Englesbe, Alexander; Elle, Jennifer; Domonkos, Matthew; Schmitt-Sody, Andreas


    A tightly focused femtosecond, weakly relativistic laser pulse partially ionizes the ambient gas, creating a string (a ``filament'') of electron density, locally reducing the nonlinear index and compensating for the self-focusing effect caused by bound electrons. While maintaining the filament over many Rayleigh lengths, the pulse drives inside it a three-dimensional (3D) wave of charge separation - the plasma wake. If the pulse waist size is much smaller than the Langmuir wavelength, electron current in the wake is mostly transverse. Electrons, driven by the wake across the sharp radial boundary of the filament, lose coherence within 2-3 periods of wakefield oscillations, and the wake decays. The laser pulse is thus accompanied by a short-lived, almost aperiodic electron current coupled to the sharp index gradient. The comprehensive 3D hydrodynamic model shows that this structure emits a broad-band THz radiation, with the highest power emitted in the near-forward direction. The THz radiation pattern contains information on wake currents surrounding the laser pulse, thus serving as an all-optical diagnostic tool. The results are tested in cylindrical and full 3D PIC simulations using codes WAKE and EPOCH.

  7. Fluorescence spectra of Rhodamine 6G for high fluence excitation laser radiation

    CERN Document Server

    Hung, J; Olaizola, A M


    Fluorescence spectral changes of Rhodamine 6G in ethanol and glycerol solutions and deposited as a film on a silica surface have been studied using a wide range of pumping field fluence at 532 nm at room temperature. Blue shift of the fluorescence spectra and fluorescence quenching of the dye molecule in solution are observed at high excitation fluence values. Such effects are not reported for the film sample. The effects are interpreted as the result of population redistribution in the solute-solvent molecular system induced by the high fluence field and the fluence dependence of the radiationless decay mechanism.

  8. Core exciton migration in Rb{sub 0.82}Cs{sub 0.18}Cl under excitation with synchrotron radiation and laser light

    Energy Technology Data Exchange (ETDEWEB)

    Tsujibayashi, Toru [Department of Physics, Osaka Dental University, 8-1 Kuzuha-hanazono, Hirakata, Osaka 573-1121 (Japan)]. E-mail:; Azuma, Junpei [Synchrotron Light Application Center, Saga University, Saga 840-8502 (Japan); Inabe, Yoshiyuki [Department of Electrical and Electronic Engineering, Shinshu University, Nagano 380-8553 (Japan); Toyoda, Koichi [Department of Physics, Osaka Dental University, 8-1 Kuzuha-hanazono, Hirakata, Osaka 573-1121 (Japan); Kamada, Masao [Synchrotron Light Application Center, Saga University, Saga 840-8502 (Japan); Itoh, Minoru [Department of Electrical and Electronic Engineering, Shinshu University, Nagano 380-8553 (Japan)


    The migration of the core exciton in a mixed crystal of Rb{sub 0.82}Cs{sub 0.18}Cl is investigated through time-resolved measurement under excitation with synchrotron radiation (SR) and laser. The photon energy of SR is tuned to the absorption band due to the exciton composed of a conduction electron and the hole originated from the outermost core state of the Rb ion (Rb-core exciton). The time-integrated intensity of Auger-free luminescence (AFL) due to the outermost core state of the Cs ion is increased by the laser irradiation. The lifetime of the laser-induced AFL depends on the photon energy of SR. The experimental result suggests the difference between the migration length of the Rb-core exciton and that of the Cs-core hole.

  9. Non-radiative excitation fluorescence microscopy (United States)

    Riachy, Lina; Vézy, Cyrille; Jaffiol, Rodolphe


    Non-radiative Excitation Fluorescence Microscopy (NEFM) constitutes a new way to observe biological samples beyond the diffraction limit. Non-radiative excitation of the samples is achieved by coating the substrate with donor species, such as quantum dots (QDs). Thus the dyes are not excited directly by the laser source, as in common fluorescence microscopy, but through a non-radiative energy transfer. To prevent dewetting of the donor film, we have recently implemented a silanization process to covalently bond the QDs on the substrate. An homogeneous monolayer of QDs was then deposited on only one side of the coverslips. Atomic force microscopy was then used to characterize the QD layer. We highlight the potential of our method through the study of Giant Unilamellar Vesicles (GUVs) labeled with DiD as acceptor, in interaction with surface functionalized with poly-L-lysine. In the presence of GUVs, we observed a quenching of QDs emission, together with an emission of DiD located in the membrane, which clearly indicated that non-radiative energy transfer from QDs to DiD occurs.

  10. Femtosecond laser excitation of dielectric materials

    DEFF Research Database (Denmark)

    Wædegaard, Kristian Juncher; Balling, Peter; Frislev, Martin Thomas


    We report an approach to modeling the interaction between ultrashort laser pulses and dielectric materials. The model includes the excitation of carriers by the laser through strongfield excitation, collisional excitation, and absorption in the plasma consisting of conduction-band electrons formed...

  11. Efficient two-step Positronium laser excitation to Rydberg levels

    Energy Technology Data Exchange (ETDEWEB)

    Cialdi, S.; Boscolo, I.; Castelli, F. [Universita degli Studi di Milano, via Celoria 16, 20133 Milano (Italy); Istituto Nazionale di Fisica Nucleare, sezione di Milano, via Celoria 16, 20133 Milano (Italy); Villa, F., E-mail: [Universita degli Studi di Milano, via Celoria 16, 20133 Milano (Italy); Istituto Nazionale di Fisica Nucleare, sezione di Milano, via Celoria 16, 20133 Milano (Italy); Ferrari, G. [INO-CNR BEC Center, via Sommarive 14, 38123 Povo, Trento (Italy); LENS-Universita di Firenze, via Carrara 1, 50019 Sesto Fiorentino (Italy); Istituto Nazionale di Fisica Nucleare, Gruppo collegato di Trento, via Sommarive 14, 38123 Povo, Trento (Italy); Giammarchi, M.G. [Istituto Nazionale di Fisica Nucleare, sezione di Milano, via Celoria 16, 20133 Milano (Italy)


    Antihydrogen production by charge exchange reaction between Positronium atoms and antiprotons requires efficient excitation of Positronium atoms up to high-n levels (Rydberg levels). A two-step optical excitation, the first from ground to n=3 and the second from this level to a Rydberg level, is proposed and a suitable laser system is discussed. The requirements on the energy and bandwidth of the excitation laser suggest the use of optical parametric generation technology for both wavelengths. The laser system is composed by two subsystems: one for the generation of 205 nm radiation and the other for the generation of 1670 nm radiation. We have separately developed and tested the laser sources and results are here presented.

  12. Observation of coherent optical phonons excited by femtosecond laser radiation in Sb films by ultrafast electron diffraction method

    Energy Technology Data Exchange (ETDEWEB)

    Mironov, B. N.; Kompanets, V. O.; Aseev, S. A., E-mail: [Russian Academy of Sciences, Institute of Spectroscopy (Russian Federation); Ischenko, A. A. [Moscow Technological University, Institute of High Chemical Technologies (Russian Federation); Kochikov, I. V. [Moscow State University (Russian Federation); Misochko, O. V. [Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation); Chekalin, S. V.; Ryabov, E. A. [Russian Academy of Sciences, Institute of Spectroscopy (Russian Federation)


    The generation of coherent optical phonons in a polycrystalline antimony film sample has been investigated using femtosecond electron diffraction method. Phonon vibrations have been induced in the Sb sample by the main harmonic of a femtosecond Ti:Sa laser (λ = 800 nm) and probed by a pulsed ultrashort photoelectron beam synchronized with the pump laser. The diffraction patterns recorded at different times relative to the pump laser pulse display oscillations of electron diffraction intensity corresponding to the frequencies of vibrations of optical phonons: totally symmetric (A{sub 1g}) and twofold degenerate (E{sub g}) phonon modes. The frequencies that correspond to combinations of these phonon modes in the Sb sample have also been experimentally observed.

  13. Radiation power control of the industrial CO2 lasers excited by a nonself-sustained glow discharge with regard to dissociation in a working gas mixture (United States)

    Shemyakin, Andrey N.; Rachkov, Michael Yu.; Solovyov, Nikolay G.; Yakimov, Mikhail Yu.


    The action of a working gas mixture degradation related to the plasma chemical reactions in a glow discharge on the laser output power of the molecular laser excited by a nonself-sustained glow discharge has been studied by the example of an industrial laser of ;Lantan; CO2 laser series. It was found that the laser power overshoot when operating on a fresh gas mixture may exceed 3 times power level set in a steady-state regime. The working algorithm for the control system was proposed and developed setting standard fresh CO2/N2/He laser gas mixture to plasma chemical equilibrium composition during the laser turn-on procedure after full refill of a working gas mixture.

  14. Photodissociation C/sub 3/F/sub 7/I laser excited by radiation from a magnetoplasma compressor

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, N.P.; Kamrukov, A.S.; Kashnikov, G.N.; Malashchenko, V.A.; Orlov, V.K.; Protasov, Yu.S.


    The necessary conditions are realized in the plasma focus of a magnetoplasma compressor of the erosion type. The investigations of the radiation properties of the plasma focus in the visible and UV regions have shown that the emission spectrum differs strongly from a Planck spectrum. Experiments on optical pumping of active media were performed. (MHR)

  15. Electronically Excited C2 from Laser Photodissociated C60 (United States)

    Arepalli, Sivaram; Scott, Carl D.; Nikolaev, Pavel; Smalley, Richard E.


    Spectral and transient emission measurements are made of radiation from products of laser excitation of buckminsterfullerene (C60) vapor diluted in argon at 973 K. The principal radiation is from the Swan band system of C2 and, at early times, also from a black body continuum. The C2 radiation is observed only when C60 is excited by green (532 nm) and not with IR (1064 nm) laser radiation at energy densities of about 1.5 J/square cm. Transient measurements indicate that there are two characteristic periods of decay of radiation. The first period, lasting about 2 micro seconds, has a characteristic decay time of about 0.3 micro seconds. The second period, lasting at least 50 micro seconds, has a characteristic decay time of about 5 micro seconds. These characteristic times are thought to be associated with cooling of C60 molecules or nanosized carbon particles during the early period; and with electronically excited C2 that is a decomposition product of laser excited C60, C58, ... molecules during the later period.

  16. Laser Excited Fluorescence For Forensic Diagnostics (United States)

    McKinney, Robert E.


    The application of laser excited fluorescence to the detection and identification of latent fingerprints was first accomplished ten years ago. The development of the technology has progressed rapidly with the introduction of commercial equipment by several manufacturers. Systems based on Argon-ion, Copper-vapor, and frequency-doubled Nd:YAG lasers are compared. The theoretical basis of detection by fluorescence is discussed along with the more useful techniques of dye staining. Other applications of the laser excited fluorescence in forensic investigation include gunshot residue analysis, serology, collection of trace evidence, and document examination.

  17. Excitation of XUV radiation in solar flares (United States)

    Emslie, A. Gordon


    The goal of the proposed research was to understand the means by which XUV radiation in solar flares is excited, and to use this radiation as diagnostics of the energy release and transport processes occurring in the flare. Significant progress in both of these areas, as described, was made.

  18. Laser undulator radiation

    CERN Document Server

    Kawamura, Y; Ruschin, S; Tanabé, T; Toyoda, K


    Various characteristics such as the number of photons, the wavelength, and the solid angle of the laser undulator radiation have been measured quantitatively. It was performed in the visible wavelength region using the interaction between a high-power pulsed CO sub 2 laser and a high-quality electron beam having an energy of 0.65-0.85 MeV. The experimental results were in good agreement with the theoretical calculations. A criterion to determine the limitation to the number of periods of the laser undulator was also proposed.

  19. Laser radiation bracket debonding (United States)

    Dostálová, Tat'jana; Jelínková, Helena; Šulc, Jan; Koranda, Petr; Nemec, Michal; Racek, Jaroslav; Miyagi, Mitsunobu


    Ceramic brackets are an aesthetic substitute for conventional stainless steel brackets in orthodontic patients. However, ceramic brackets are more brittle and have higher bond strengths, which can lead to bracket breakage and enamel damage during classical type of debonding. This study examined the possibility of laser radiation ceramic brackets removing as well as the possible damage of a surface structure of hard dental tissue after this procedure. Two types of lasers were used for the experiments - a laser diode LIMO HLU20F400 generating a wavelength of 808 nm with the maximum output power 20W at the end of the fiber (core diameter 400 μm, numerical aperture 0.22). As a second source, a diode-pumped Tm:YAP laser system generating a wavelength of 1.9 μm, with up to 3.8 W maximum output power was chosen. For the investigation, extracted incisors with ceramic brackets were used. In both cases, laser radiation was applied for 0.5 minute at a maximum power of 1 W. Temperature changes of the irradiated tissue was registered by camera Electrophysics PV320. After the interaction experiment, the photo-documentation was prepared by the stereomicroscope Nikon SMZ 2T, Japan. The surface tissue analysis was processed in "low vacuum" (30 Pa) regime without desiccation. This technique was used to record back-scattered electron images. Selecting the appropriate laser, resin, and bracket combination can minimize risks of enamel degradation and make debonding more safe.

  20. Sound Radiation of Aerodynamically Excited Flat Plates into Cavities

    Directory of Open Access Journals (Sweden)

    Johannes Osterziel


    Full Text Available Flow-induced vibrations and the sound radiation of flexible plate structures of different thickness mounted in a rigid plate are experimentally investigated. Therefore, flow properties and turbulent boundary layer parameters are determined through measurements with a hot-wire anemometer in an aeroacoustic wind tunnel. Furthermore, the excitation of the vibrating plate is examined by laser scanning vibrometry. To describe the sound radiation and the sound transmission of the flexible aluminium plates into cavities, a cuboid-shaped room with adjustable volume and 34 flush-mounted microphones is installed at the non flow-excited side of the aluminium plates. Results showed that the sound field inside the cavity is on the one hand dependent on the flow parameters and the plate thickness and on the other hand on the cavity volume which indirectly influences the level and the distribution of the sound pressure behind the flexible plate through different excited modes.

  1. Excimer Lasers With Capacitively Excited Tubular Discharges (United States)

    Eichler, Hans J.; Herweg, Helmut; de la Rosa, Jose


    The excitation of excimer lasers in tubular discharges results in simple and compact devices needing no preionization. Optical output energies are in the millijoule range. We investigated XeF, KrF and ArF lasers for various operating conditions. The lasers consist of capillary glass tubes with two internal electrodes at the ends and an aluminium-foil wrapped around the tube as capacitive electrode. A maximum output energy of 0.3 mJ has been achieved for the XeF laser. The good quality of the discharge is indicated by the observation of spontaneous mode locking. The detailed study of the discharge for different polarities of the electrodes has shown that efficient operation with a high gas lifetime can be obtained by a purely capacitively excited discharge. A gas lifetime of about 10,000 pulses for 3 litres gas mixture has been observed. Using a two stage Marx generator to generate 100 kV excitation voltage a maximum output energy of 0.7 mJ was obtained for a gas mixture of Kr, F2 and He with an efficiency of 0.17%. The KrF laser operates also without the buffer gas. Laser action in ArF has been achieved with 15 μJ pulse energy and 10 ns duration.

  2. Radiative widths of neutral kaon excitations

    Indian Academy of Sciences (India)

    we limit the radiative widths Γr(K*(1410)) and Γr(K*. 2(1430)) to 52.9 and 5.4 keV, respectively, at 90% CL. While there is no prediction for Γr(K*(1410)), Babcock and Rosner [9] used SU(3) invariance to predict that excitations with JPC = 1++ or 2++ would have vanishing radiative widths. In the limit of SU(3), K*. 2(1430) has.

  3. Laser-induced incandescence of suspended particles as a source of excitation of dye luminescence

    CERN Document Server

    Zelensky, S


    The interaction of pulsed YAG-Nd sup 3 sup + laser radiation with submicron light-absorbing particles suspended in an aqueous solution of Rhodamine 6G is investigated experimentally. The experiments demonstrate that the laser-induced incandescence of suspended particles excites the luminescence of the dissolved dye molecules. The mechanism of the luminescence excitation consists in the reabsorption of the thermal radiation within the volume of the sample cell. On the ground of this mechanism of excitation, a method of measurement of the luminescence quantum yield is proposed and realized. The method requires the knowledge of the geometrical parameters of the cell and does not require the use of reference samples.

  4. Laser techniques for spectroscopy of core-excited atomic levels (United States)

    Harris, S. E.; Young, J. F.; Falcone, R. W.; Rothenberg, J. E.; Willison, J. R.


    We discuss three techniques which allow the use of tunable lasers for high resolution and picosecond time scale spectroscopy of core-excited atomic levels. These are: anti-Stokes absorption spectroscopy, laser induced emission from metastable levels, and laser designation of selected core-excited levels.

  5. Differential cross sections for ionization and excitation of laser-aligned atoms by electron impact (United States)

    Murray, Andrew


    Differential cross section measurements will be presented for electron impact ionization and excitation of atoms prepared using high resolution continuous wave laser radiation. In the case of ionization, low energy coplanar asymmetric (e,2e) experiments were performed from laser excited Mg atoms that were aligned using radiation around 285nm. The atoms were subjected to linearly polarized radiation whose polarization vector was varied from in the plane to perpendicular to the scattering plane. Ionization measurements were then conducted from the laser-excited 3P state, and the differential cross section determined. By careful analysis of the laser pumping, these measurements were directly compared to those from the ground state. Such experiments provide valuable information on the ionization of aligned targets. In the second experiment to be described here, a resonant enhancement cavity has been placed around the interaction region and super-elastic scattering measurements have been carried out from laser-excited atoms inside the cavity. This new technique opens up many new targets for study, since the cavity increases the effective intensity of the laser radiation that is exciting the atoms by a factor of up to 50. As such, new ionization and excitation measurements are possible using deep UV radiation where the laser power is only a few mW. Results from calcium will be presented, and progress towards studies from silver, copper and gold will be discussed. We are also advancing this new technique to allow simultaneous excitation from the hyperfine levels of different targets (such as Rb), which will allow the method to be adopted in different fields, such as laser cooling and trapping.

  6. Modeling of collisional excited x-ray lasers using short pulse laser pumping

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Akira; Moribayashi, Kengo; Utsumi, Takayuki; Tajima, Toshiki [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment


    A simple atomic kinetics model of electron collisional excited x-ray lasers has been developed. The model consists of a collisional radiative model using the average ion model (AIM) and a detailed term accounting (DTA) model of Ni-like Ta. An estimate of plasma condition to produce gain in Ni-like Ta ({lambda}=44A) is given. Use of the plasma confined in a cylinder is proposed to preform a uniform high density plasma from 1-D hydrodynamics calculations. (author)

  7. Radiative and Excited State Charmonium Physics

    Energy Technology Data Exchange (ETDEWEB)

    Jozef Dudek


    Renewed interest in the spectroscopy of charmonium has arisen from recent unexpected observations at $e^+e^-$ colliders. Here we report on a series of works from the previous two years examining the radiative physics of charmonium states as well as the mass spectrum of states of higher spin and internal excitation. Using new techniques applied to Domain-Wall and Clover quark actions on quenched isotropic and anisotropic lattices, radiative transitions and two-photon decays are considered for the first time. Comparisons are made with experimental results and with model approaches. Forthcoming application to the light-quark sector of relevance to experiments like Jefferson Lab's GlueX is discussed.

  8. Rapidly tuning miniature transversely excited atmospheric-pressure CO2 laser. (United States)

    Qu, Yanchen; Ren, Deming; Hu, Xiaoyong; Liu, Fengmei; Zhao, Jingshan


    An experimental study of a rapidly tuning miniature transversely excited atmospheric-pressure CO2 laser is reported. To rapidly shift laser wavelengths over selected transitions in the 9-11 microm wavelength region, we have utilized a high-frequency stepping motor and a diffraction grating. The laser is highly automated with a monolithic microprocessor controlled laser line selection. For the achievement of stable laser output, a system of laser excitation with a voltage of 10 kV, providing effective surface corona preionization and allowing one to work at various gas pressures, is utilized. Laser operation at 59 emission lines of the CO2 molecule rotational transition is obtained and at 51 lines, the pulse energy of laser radiation exceeds 30 mJ. The system can be tuned between two different rotational lines spanning the wavelength range from 9.2 to 10.8 microm within 10 ms.

  9. Introduction to gas lasers with emphasis on selective excitation processes

    CERN Document Server

    Willett, Colin S


    Introduction to Gas Lasers: Population Inversion Mechanisms focuses on important processes in gas discharge lasers and basic atomic collision processes that operate in a gas laser. Organized into six chapters, this book first discusses the historical development and basic principles of gas lasers. Subsequent chapters describe the selective excitation processes in gas discharges and the specific neutral, ionized and molecular laser systems. This book will be a valuable reference on the behavior of gas-discharge lasers to anyone already in the field.

  10. Semiclassical treatment of laser excitation of the hydrogen atom

    DEFF Research Database (Denmark)

    Billing, Gert D.; Henriksen, Niels Engholm; Leforestier, C.


    We present an alternative method for studying excitation of atoms in intense laser fields. In the present paper we focus upon the optical harmonic generation by hydrogen atoms.......We present an alternative method for studying excitation of atoms in intense laser fields. In the present paper we focus upon the optical harmonic generation by hydrogen atoms....

  11. Excitable solitons in a semiconductor laser with a saturable absorber (United States)

    Turconi, Margherita; Prati, Franco; Barland, Stéphane; Tissoni, Giovanna


    Self-pulsing cavity solitons may exist in a semiconductor laser with an intracavity saturable absorber. They show locally the passive Q -switching behavior that is typical of lasers with saturable absorbers in the plane-wave approximation. Here we show that excitable cavity solitons are also possible in a suitable parameter range and characterize their excitable dynamics and properties.

  12. Modeling short-pulse laser excitation of dielectric materials

    DEFF Research Database (Denmark)

    Wædegaard, Kristian Juncher; Sandkamm, Ditte Både; Haahr-Lillevang, Lasse


    A theoretical description of ultrashort-pulse laser excitation of dielectric materials based on strong-field excitation in the Keldysh picture combined with a multiple-rateequation model for the electronic excitation including collisional processes is presented. The model includes light attenuation...

  13. Near-ultraviolet laser diodes for brilliant ultraviolet fluorophore excitation. (United States)

    Telford, William G


    Although multiple lasers are now standard equipment on most modern flow cytometers, ultraviolet (UV) lasers (325-365 nm) remain an uncommon excitation source for cytometry. Nd:YVO4 frequency-tripled diode pumped solid-state lasers emitting at 355 nm are now the primary means of providing UV excitation on multilaser flow cytometers. Although a number of UV excited fluorochromes are available for flow cytometry, the cost of solid-state UV lasers remains prohibitively high, limiting their use to all but the most sophisticated multilaser instruments. The recent introduction of the brilliant ultraviolet (BUV) series of fluorochromes for cell surface marker detection and their importance in increasing the number of simultaneous parameters for high-dimensional analysis has increased the urgency of including UV sources in cytometer designs; however, these lasers remain expensive. Near-UV laser diodes (NUVLDs), a direct diode laser source emitting in the 370-380 nm range, have been previously validated for flow cytometric analysis of most UV-excited probes, including quantum nanocrystals, the Hoechst dyes, and 4',6-diamidino-2-phenylindole. However, they remain a little-used laser source for cytometry, despite their significantly lower cost. In this study, the ability of NUVLDs to excite the BUV dyes was assessed, along with their compatibility with simultaneous brilliant violet (BV) labeling. A NUVLD emitting at 375 nm was found to excite most of the available BUV dyes at least as well as a UV 355 nm source. This slightly longer wavelength did produce some unwanted excitation of BV dyes, but at sufficiently low levels to require minimal additional compensation. NUVLDs are compact, relatively inexpensive lasers that have higher power levels than the newest generation of small 355 nm lasers. They can, therefore, make a useful, cost-effective substitute for traditional UV lasers in multicolor analysis involving the BUV and BV dyes. Published 2015 Wiley Periodicals Inc. on

  14. Ultraviolet 320 nm laser excitation for flow cytometry. (United States)

    Telford, William; Stickland, Lynn; Koschorreck, Marco


    Although multiple lasers and high-dimensional analysis capability are now standard on advanced flow cytometers, ultraviolet (UV) lasers (usually 325-365 nm) remain an uncommon excitation source for cytometry. This is primarily due to their cost, and the small number of applications that require this wavelength. The development of the Brilliant Ultraviolet (BUV fluorochromes, however, has increased the importance of this formerly niche excitation wavelength. Historically, UV excitation was usually provided by water-cooled argon- and krypton-ion lasers. Modern flow cytometers primary rely on diode pumped solid state lasers emitting at 355 nm. While useful for all UV-excited applications, DPSS UV lasers are still large by modern solid state laser standards, and remain very expensive. Smaller and cheaper near UV laser diodes (NUVLDs) emitting at 375 nm make adequate substitutes for 355 nm sources in many situations, but do not work as well with very short wavelength probes like the fluorescent calcium chelator indo-1. In this study, we evaluate a newly available UV 320 nm laser for flow cytometry. While shorter in wavelength that conventional UV lasers, 320 is close to the 325 nm helium-cadmium wavelength used in the past on early benchtop cytometers. A UV 320 nm laser was found to excite almost all Brilliant Ultraviolet dyes to nearly the same level as 355 nm sources. Both 320 nm and 355 nm sources worked equally well for Hoechst and DyeCycle Violet side population analysis of stem cells in mouse hematopoetic tissue. The shorter wavelength UV source also showed excellent excitation of indo-1, a probe that is not compatible with NUVLD 375 nm sources. In summary, a 320 nm laser module made a suitable substitute for conventional 355 nm sources. This laser technology is available in a smaller form factor than current 355 nm units, making it useful for small cytometers with space constraints. © 2017 International Society for Advancement of Cytometry. © 2017 International

  15. Excitation and Control of Plasma Wakefields by Multiple Laser Pulses (United States)

    Cowley, J.; Thornton, C.; Arran, C.; Shalloo, R. J.; Corner, L.; Cheung, G.; Gregory, C. D.; Mangles, S. P. D.; Matlis, N. H.; Symes, D. R.; Walczak, R.; Hooker, S. M.


    We demonstrate experimentally the resonant excitation of plasma waves by trains of laser pulses. We also take an important first step to achieving an energy recovery plasma accelerator by showing that a plasma wave can be damped by an out-of-resonance trailing laser pulse. The measured laser wakefields are found to be in excellent agreement with analytical and numerical models of wakefield excitation in the linear regime. Our results indicate a promising direction for achieving highly controlled, GeV-scale laser-plasma accelerators operating at multikilohertz repetition rates.

  16. Plasma lasers (a strong source of coherent radiation in astrophysics) (United States)

    Papadopoulos, K.


    The generation of electromagnetic radiation from the free energy available in electron streams is discussed. The fundamental principles involved in a particular class of coherent plasma radiation sources, i.e., plasma lasers, are reviewed, focusing on three wave coupling, nonlinear parametric instabilities, and negative energy waves. The simplest case of plasma lasers, that of an unmagnetized plasma containing a finite level of density fluctuations and electrons streaming with respect to the ions, is dealt with. A much more complicated application of plasma lasers to the case of auroral kilometric radiation is then examined. The concept of free electron lasers, including the role of relativistic scattering, is elucidated. Important problems involving the escape of the excited radiation from its generation region, effects due to plasma shielding and nonlinear limits, are brought out.

  17. Transient radiation from a ring resonant medium excited by an ultrashort superluminal pulse

    Energy Technology Data Exchange (ETDEWEB)

    Arkhipov, R M [Humboldt University at Berlin (Germany); Arkhipov, M V; Tolmachev, Yu A [Department of Physics, Saint-Petersburg State University (Russian Federation); Babushkin, I V [Institute of Quantum Optics, Leibniz University Hannover, Welfengarten 1 30167, Hannover (Germany)


    We report some specific features of transient radiation from a periodic spatially modulated one-dimensional medium with a resonant response upon excitation by an ultrashort pulse. The case of ring geometry (with particle density distributed along the ring according to the harmonic law) is considered. It is shown that the spectrum of scattered radiation contains (under both linear and nonlinear interaction), along with the frequency of intrinsic resonance of the medium, a new frequency, which depends on the pulse velocity and the spatial modulation period. The case of superluminal motion of excitation, when the Cherenkov effect manifests itself, is also analysed. (laser applications and other topics in quantum electronics)

  18. Charges and Electromagnetic Radiation as Topological Excitations

    Directory of Open Access Journals (Sweden)

    Manfried Faber


    Full Text Available We discuss a model with stable topological solitons in Minkowski space with only three degrees of freedom, the rotational angles of a spatial Dreibein. This model has four types of solitons differing in two topological quantum numbers which we identify with electric charge and spin. The vacuum has a two-dimensional degeneracy leading to two types of massless excitations, characterised by a topological quantum number which could have a physical equivalent in the photon number.

  19. Laser excitation of Antihydrogen in ALPHA

    CERN Multimedia


    Animation of how a trapped antihydrogen atom is excited by two photons from the 1S to the 2S state in antihydrogen, and further photo-ionised by a third foton. The first part of the movie shows how antihydrogen is made and captured in a magnetic minimum trap.

  20. Laser-excited fluorescence for measuring atmospheric pollution (United States)

    Menzies, R. T.


    System measures amount of given pollutant at specific location. Infrared laser aimed at location has wavelength that will cause molecules of pollutant to fluoresce. Detector separates fluorescence from other radiation and measures its intensity to indicate concentration of pollutant.

  1. Laser-excitation atomic fluorescence spectroscopy in a helium microwave-induced plasma (United States)

    Schroeder, Timothy S.

    The focus of this dissertation is to report the first documented coupling of helium microwave induced plasmas (MIPs) to laser excitation atomic fluorescence spectroscopy. The ability to effectively produce intense atomic emission from both metal and nonmetal analytes gives helium microwave induced plasmas a greater flexibility than the more commonly utilized argon inductively coupled plasma (ICP). Originally designed as an element selective detector for non-aqueous chromatography applications at low applied powers (500 W). The helium MIP has been shown to be a very powerful analytical atomic spectroscopy tool. The development of the pulsed dye laser offered an improved method of excitation in the field of atomic fluorescence. The use of laser excitation for atomic fluorescence was a logical successor to the conventional excitation methods involving hollow cathode lamps and continuum sources. The highly intense, directional, and monochromatic nature of laser radiation results in an increased population of atomic species in excited electronic states where atomic fluorescence can occur. The application of laser excitation atomic fluorescence to the analysis of metals in a helium microwave induced plasma with ultrasonic sample nebulization was the initial focus of this work. Experimental conditions and results are included for the aqueous characterization of manganese, lead, thallium, and iron in the helium MIP- LEAFS system. These results are compared to previous laser excitation atomic fluorescence experimentation. The effect of matrix interferences on the analytical fluorescence signal was also investigated for each element. The advantage of helium MIPs over argon ICPs in the determination of nonmetals in solution indicates that the helium MIP is an excellent candidate for laser excitation atomic fluorescence experiments involving nonmetals such as chlorine, bromine, iodine, and sulfur. Preliminary investigations into this area are reported, including documentation

  2. Water splitting by infrared femtosecond laser excitation of surface plasmon (United States)

    Klett, Charles; Mirica, Jean-Philippe; Hergott, Jean-François; Lepetit, Fabien; Renault, Jean-Philippe


    Gold nanoparticles supported on soda-lime glass exhibit a photochemical water splitting activity under infrared femtosecond laser excitation. Both H2 and hydroxyl radicals productions were characterized. The hydroxyl radicals production mechanism was identified by comparison with three prototypal mechanisms, photoionization of organic compound in the UV, VUV dissociation of water and water gamma radiolysis. The mechanisms involved in the case of laser femtosecond seem to be water ionization events occurring at distance from the gold particles.

  3. Ultrashort-pulse laser excitation and damage of dielectric materials

    DEFF Research Database (Denmark)

    Haahr-Lillevang, Lasse; Balling, Peter


    Ultrashort-pulse laser excitation of dielectrics is an intricate problem due to the strong coupling between the rapidly changing material properties and the light. In the present paper, details of a model based on a multiple-rate-equation description of the conduction band are provided. The model...... is verified by comparison with recent experimental measurements of the transient optical properties in combination with ablation-depth determinations. The excitation process from the first creation of conduction-band electrons at low intensities to the formation of a highly-excited plasma and associated...

  4. Alternating-laser excitation : single-molecule FRET and beyond

    NARCIS (Netherlands)

    Hohlbein, Johannes; Craggs, Timothy D.; Cordes, Thorben


    The alternating-laser excitation (ALEX) scheme continues to expand the possibilities of fluorescence-based assays to study biological entities and interactions. Especially the combination of ALEX and single-molecule Forster Resonance Energy Transfer (smFRET) has been very successful as ALEX enables

  5. Alternating-laser excitation: single-molecule FRET and beyond

    NARCIS (Netherlands)

    Hohlbein, J.C.; Craggs, T.D.; Cordes, T.


    The alternating-laser excitation (ALEX) scheme continues to expand the possibilities of fluorescence-based assays to study biological entities and interactions. Especially the combination of ALEX and single-molecule Förster Resonance Energy Transfer (smFRET) has been very successful as ALEX enables

  6. Survey of nuclei for low-energy nuclear excitation in laser-produced plasma

    Energy Technology Data Exchange (ETDEWEB)

    Granja, C. [Institute of Experimental and Applied Physics, Czech Technical University, 128 00 Prague 2 (Czech Republic)]. E-mail:; Kuba, J. [Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, 115 19 Prague 1 (Czech Republic); Haiduk, A. [Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, 115 19 Prague 1 (Czech Republic); Renner, O. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic)


    We present a survey of stable and long-lived nuclei as well as nuclear isomers looking for candidates of studies of low-energy (1-30 keV) nuclear excitation by laser-produced plasma radiation. We concentrate on medium-size high-power lasers with pulse duration of hundreds of ps providing energy up to 1000 J and subrelativistic intensity of 10{sup 16}-10{sup 17} Wcm{sup -2}. Screening criteria are primarily the transition energy and the half-life, spin and parity of nuclear levels. Ta181 is suggested as first candidate for which an estimation of reaction efficiency is included.

  7. [Effects of laser shot frequency on plasma radiation characteristics]. (United States)

    Chen, Jin-Zhong; Bai, Jin-Ning; Song, Guang-Ju; Sun, Jiang; Deng, Ze-Chao; Wang, Ying-Long


    To improve the quality of laser-induced breakdown spectroscopy, nanosecond pulse laser generated by Nd:YAG laser was used to excite soil sample. The intensity and signal-to-background ratio of A1 I 394.401 nm, Ba I 455.403 nm, Fe I 430.791 nm and Ti I 498.173 nm were observed using a grating spectrometer and a photoelectric detection system. The effects of laser shot frequency (5, 10 and 15 Hz)on the radiation characteristics of laser-induced plasma was studied. The experimental results show that as compared with the laser shot frequency of 5 Hz, the spectral line intensity of A1, Ba, Fe and Ti increased by about 50.94%, 112.7%, 107.46%, and 99.38% at 15 Hz respectively under the same laser energy, while the spectral signal-to-background ratio increased by about 15.16%, 24.08%, 40.26% and 72.06% respectively. The effects mechanism of the laser shot frequency on radiation characteristics of plasma is explained by measuring plasma parameters.

  8. Laser Doppler velocimetry based on the optoacoustic effect in a RF-excited CO2 laser. (United States)

    Lee, Teaghee; Choi, Jong Woon; Kim, Yong Pyung


    We present a compact optoacoustic laser Doppler velocimetry method that utilizes the self-mixing effect in a RF-excited CO(2) laser. A portion of a Doppler-shifted laser beam, produced by irradiating a single wavelength laser beam on a moving object, is mixed with an originally existing laser beam inside a laser cavity. The fine change of pressure in the laser cavity modulated by the Doppler-shifted frequency is detected by a condenser microphone in the laser tube. In our studies, the frequency of the Doppler signal due to the optoacoustic effect was detected as high as 50 kHz. Our measurements also confirmed that the signal varied linearly with the velocity of the external scatterer (the moving object) and the cosine of the angle between the laser beam and the velocity vector of the object.

  9. Electron scattering by laser-excited barium atoms (United States)

    Register, D. F.; Trajmar, S.; Jensen, S. W.; Poe, R. T.


    Inelastic and superelastic scattering of 30- and 100-eV electrons by laser-excited 6s 6p 1P and subsequent cascade-populated 6s 6p 3P, 6s 5d 1D, and 6s 5d 3D Ba atoms have been observed. Absolute differential cross sections for the singlet and relative scattering intensities for the triplet species have been determined in the 5 to 20 deg angular region. Under the present conditions excitations dominate over deexcitations.

  10. Selective emission and luminescence of Er2O3 under intense laser excitation (United States)

    Marchenko, V. M.; Iskhakova, L. D.; Studenikin, M. I.


    The microstructure of Er2O3 polycrystals synthesised by laser heating is studied. The synthesis of erbium silicate (Er2SiO5) layers was observed upon interaction of Er2O3 and SiO2 melts. The dependences of the selective emission (SE) and luminescence spectra of Er2O3 polycrystals in the range 200 - 1700 nm on the intensity of laser-thermal (at the wavelength λ = 10.6 μm) and resonant laser (λ ≈ 975 nm) excitation are investigated. The emission of heated Er2O3 polycrystals arises as a result of multiphonon relaxation of absorbed energy and is a superposition of the SE at the electronic-vibrational transitions of Er3+ ions and the thermal radiation of the crystal lattice. The shape of the SE spectra of Er2O3 polycrystals in the range 400 - 1700 nm almost does not change upon laser-thermal heating from 300 to 1500 K and subsequent cooling and corresponds to the absorption spectra of Er3+ ions. With increasing temperature, the thermal radiation intensity increases faster than the SE intensity, and the shape of the Er2O3 spectrum becomes closer to the calculated spectrum of a blackbody. The anti-Stokes luminescence spectra of Er3+ ions formed under intense laser excitation of the 4I11/2 level are explained by additional SE caused by heating of the crystal matrix due to the Stokes losses. A difference between the SE and luminescence spectra is observed at low intensities of resonant laser excitation and low temperatures, when only the Stokes luminescence occurs. The temperature dependences of the SE and luminescence spectra of Er2O3 upon laser excitation testify to the fundamental role played by the interaction of the electronic f-shell of Er3+ ions with crystal lattice vibrations in the processes of multiphonon radiative and nonradiative relaxation. The laser-thermal synthesis is promising for inprocess variation of the chemical composition of rare-earth samples.

  11. Mode-locked solid state lasers using diode laser excitation (United States)

    Holtom, Gary R [Boston, MA


    A mode-locked laser employs a coupled-polarization scheme for efficient longitudinal pumping by reshaped laser diode bars. One or more dielectric polarizers are configured to reflect a pumping wavelength having a first polarization and to reflect a lasing wavelength having a second polarization. An asymmetric cavity provides relatively large beam spot sizes in gain medium to permit efficient coupling to a volume pumped by a laser diode bar. The cavity can include a collimation region with a controlled beam spot size for insertion of a saturable absorber and dispersion components. Beam spot size is selected to provide stable mode locking based on Kerr lensing. Pulse durations of less than 100 fs can be achieved in Yb:KGW.

  12. Electromagnetic radiation from a laser wakefield accelerator

    NARCIS (Netherlands)

    Khachatryan, A.G.; van Goor, F.A.; Boller, Klaus J.


    Coherent and incoherent electromagnetic radiation emitted from a laser wakefield accelerator is calculated based on Lienard-Wiechert potentials. It is found that at wavelengths longer than the bunch length, the radiation is coherent. The coherent radiation, which typically lies in the infrared

  13. Luminescence and excitation spectra of YAG:Nd{sup 3+} excited by synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Ning Lixin [Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Tanner, Peter A. [Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)], E-mail:; Harutunyan, Vachagan V.; Aleksanyan, Eduard [Yerevan Physics Institute, 2 Alikhanian Brothers Str., 375036 Yerevan (Armenia); Makhov, Vladimir N. [Lebedev Physical Institute, Leninskii Prospect 53, 119991 Moscow (Russian Federation); Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia); Kirm, Marco [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia)


    The low-temperature 4f{sup 2}5d{yields}4f{sup 3} fast emission of Nd{sup 3+} from YAG:Nd{sup 3+} has been studied under excitation by synchrotron radiation. Additionally, 4f{sup 3}{yields}4f{sup 3} luminescence of Nd{sup 3+} has been observed and assigned to transitions from the {sup 2}F(2){sub 5/2} and {sup 4}F{sub 3/2} multiplet terms. The observed experimental spectra of Nd{sup 3+} d-f emission and f-d excitation are well simulated by crystal-field calculations.

  14. Finite-amplitude strain waves in laser-excited plates. (United States)

    Mirzade, F Kh


    The governing equations for two-dimensional finite-amplitude longitudinal strain waves in isotropic laser-excited solid plates are derived. Geometric and weak material nonlinearities are included, and the interaction of longitudinal displacements with the field of concentration of non-equilibrium laser-generated atomic defects is taken into account. An asymptotic approach is used to show that the equations are reducible to the Kadomtsev-Petviashvili-Burgers nonlinear evolution equation for a longitudinal self-consistent strain field. It is shown that two-dimensional shock waves can propagate in plates.

  15. Is the segmented plasma excitation recombination laser a recombination laser

    Energy Technology Data Exchange (ETDEWEB)

    Apollonov, V.V.; Sirotkin, A.A. (Institut Obshchei Fiziki, Moscow (USSR))


    The role of plasmachemical reactions in the formation of active media in lasers with a sectional plasma source for metal vapor is investigated. It is shown that the population of ionic levels in Cd II and Zn II occurs under recharging with He(+) and in the process of Penning ionization. It is found that these processes are more efficient than recombination and electron impact. 13 refs.

  16. Planck's Radiation Law: Thermal Excitations of Vacuum Induced Fluctuations

    Directory of Open Access Journals (Sweden)

    Ogiba F.


    Full Text Available The second Planck’s radiation law is derived considering that “resonators” induced by the vacuum absorb thermal excitations as additional fluctuations. The maximum energy transfer, as required by the maximum entropy equilibrium, occurs when the frequencies of these two kind of vibrations are equal. The motion resembles that of the coherent states of the quantum oscillator, as originally pointed by Schrödinger [1]. The resulting variance, due to random phases, coincides with that used by Einstein to reproduce the first Planck’s radiation law from his thermal fluctuation equation [2].

  17. Electromagnetic Radiation Generated by Acoustic Excitation of Rock Samples (United States)

    Yavorovich, Lyudmila V.; Bespalko, Anatolii A.; Fedotov, Pavel I.; Baksht, Rina B.


    The paper presents an experiment on acoustic excitation of electromagnetic radiation (EMR) signals in skarn, sandstone, and magnetite ore samples. For the skarn and sandstone samples, the EMR signal amplitude was observed to decrease with increasing ultimate strength. Supposedly, this effect can be explained by assuming that EMR is generated when an acoustic wave propagates through an electrical double layer. The presence of piezoelectric inclusions ( e.g., quartz) in the magnetite ore enhances the analog EMR signal and its spectral components.

  18. UV Resonant Raman Spectrometer with Multi-Line Laser Excitation (United States)

    Lambert, James L.; Kohel, James M.; Kirby, James P.; Morookian, John Michael; Pelletier, Michael J.


    A Raman spectrometer employs two or more UV (ultraviolet) laser wavel engths to generate UV resonant Raman (UVRR) spectra in organic sampl es. Resonant Raman scattering results when the laser excitation is n ear an electronic transition of a molecule, and the enhancement of R aman signals can be several orders of magnitude. In addition, the Ra man cross-section is inversely proportional to the fourth power of t he wavelength, so the UV Raman emission is increased by another fact or of 16, or greater, over visible Raman emissions. The Raman-scatter ed light is collected using a high-resolution broadband spectrograph . Further suppression of the Rayleigh-scattered laser light is provi ded by custom UV notch filters.

  19. Excitation wavelength dependence of water-window line emissions from boron-nitride laser-produced plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Crank, M.; Harilal, S. S.; Hassan, S. M.; Hassanein, A. [Center for Materials Under Extreme Environment, School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)


    We investigated the effects of laser excitation wavelength on water-window emission lines of laser-produced boron-nitride plasmas. Plasmas are produced by focusing 1064 nm and harmonically generated 532 and 266 nm radiation from a Nd:YAG laser on BN target in vacuum. Soft x-ray emission lines in the water-window region are recorded using a grazing-incidence spectrograph. Filtered photodiodes are used to obtain complementary data for water-window emission intensity and angular dependence. Spectral emission intensity changes in nitrogen Ly-{alpha} and He-{alpha} are used to show how laser wavelength affects emission. Our results show that the relative intensity of spectral lines is laser wavelength dependent, with the ratio of Ly-{alpha} to He-{alpha} emission intensity decreasing as laser wavelength is shortened. Filtered photodiode measurements of angular dependence showed that 266 and 532 nm laser wavelengths produce uniform emission.

  20. Excitation wavelength dependence of water-window line emissions from boron-nitride laser-produced plasmas (United States)

    Crank, M.; Harilal, S. S.; Hassan, S. M.; Hassanein, A.


    We investigated the effects of laser excitation wavelength on water-window emission lines of laser-produced boron-nitride plasmas. Plasmas are produced by focusing 1064 nm and harmonically generated 532 and 266 nm radiation from a Nd:YAG laser on BN target in vacuum. Soft x-ray emission lines in the water-window region are recorded using a grazing-incidence spectrograph. Filtered photodiodes are used to obtain complementary data for water-window emission intensity and angular dependence. Spectral emission intensity changes in nitrogen Ly-α and He-α are used to show how laser wavelength affects emission. Our results show that the relative intensity of spectral lines is laser wavelength dependent, with the ratio of Ly-α to He-α emission intensity decreasing as laser wavelength is shortened. Filtered photodiode measurements of angular dependence showed that 266 and 532 nm laser wavelengths produce uniform emission.

  1. Sound wave and laser excitation for acousto-optical landmine detection

    NARCIS (Netherlands)

    Lutzmann, P.; Heuvel, J.C. van den; Klien, V.; Schleijpen, H.M.A.; Hebel, M.; Putten, F.J.M. van


    Acoustic landmine detection (ALD) is a technique for the detection of buried landmines including non-metal mines. An important issue in ALD is the acoustic excitation of the soil. Laser excitation is promising for complete standoff detection using lasers for excitation and monitoring. Acoustic

  2. [Laser radiations in medical therapy]. (United States)

    Richand, P; Boulnois, J L


    The therapeutic effects of various types of laser beams and the various techniques employed are studied. Clinical and experimental research has shown that Helio-Neon laser beams are most effective as biological stimulants and in reducing inflammation. For this reasons they are best used in dermatological surgery cases (varicose ulcers, decubital and surgical wounds, keloid scars, etc.). Infrared diode laser beams have been shown to be highly effective painkillers especially in painful pathologies like postherpetic neuritis. The various applications of laser therapy in acupuncture, the treatment of reflex dermatologia and optic fibre endocavital therapy are presented. The neurophysiological bases of this therapy are also briefly described.

  3. Theory of propagation of spectrum and correlations of radiation in optically dense gas in the case of the closed excitation contour

    Directory of Open Access Journals (Sweden)

    Barantsev K.A.


    Full Text Available This work is devoted to generalization of the semi-classical theory of interaction of broadband laser radiation with the atomic gas at the room temperature in the cell in the case of the closed excitation contour. The atomic density matrix equations and spectrum and correlations transport equations have been derived for excitation by fluctuating field with Gaussian statistics. It is shown that the spatial oscillations of radiation intensity and atomic density matrix can be excited. It was found that such medium can serve as a filter of incoherent part of the radiation.

  4. Laser synchrotron radiation and beam cooling

    Energy Technology Data Exchange (ETDEWEB)

    Esarey, E.; Sprangle, P.; Ting, A. [Naval Research Lab., Washington, DC (United States)] [and others


    The interaction of intense {approx_gt} 10{sup 18} W/cm{sup 2}, short pulse ({approx_lt} 1 ps) lasers with electron beams and plasmas can lead to the generation of harmonic radiation by several mechanisms. Laser synchrotron radiation may provide a practical method for generating tunable, near monochromatic, well collimated, short pulse x-rays in compact, relatively inexpensive source. The mechanism for the generation of laser synchrotron radiation is nonlinear Thomson scattering. Short wavelengths can be generated via Thomson scattering by two methods, (i) backscattering from relativistic electron beams, in which the radiation frequency is upshifted by the relativistic factor 4{gamma}{sup 2}, and (ii) harmonic scattering, in which a multitude of harmonics are generated with harmonic numbers extending out to the critical harmonic number nc{approx_equal}a{sub 0}{sup 3} {much_gt} 1, where a{sub 0} {approx_equal}10{sup -9}{lambda}I{sup 1/2}, {lambda} is the laser wavelength in {mu}m and I is the laser intensity in W/cm{sup 2}. Laser synchrotron sources are capable of generating short ({approx_lt} ps) x-ray pulses with high peak flux ({approx_gt} 10{sup 21} photons/s) and brightness ({approx_gt}{sup 19} photons/s-mm{sup 2}-mrad{sup 2} 0.1%BW. As the electron beam radiates via Thomson scattering, it can subsequently be cooled, i.e., the beam emittance and energy spread can be reduced. This cooling can occur on rapid ({approximately} ps) time scales. In addition, electron distributions with sufficiently small axial energy spreads can be used to generate coherent XUV radiation via a laser-pumped FEL mechanism.

  5. Trapped electronic states in YAG crystal excited by femtosecond radiation

    Energy Technology Data Exchange (ETDEWEB)

    Zavedeev, E.V.; Kononenko, V.V.; Konov, V.I. [General Physics Institute of RAS, Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation)


    The excitation of an electronic subsystem of an yttrium aluminum garnet by 800 nm femtosecond radiation was studied theoretically and experimentally. The spatio-temporal dynamics of the refractive index (n) inside the beam waist was explored by means of the pump-probe interferometric technique with a submicron resolution. The observed increase in n indicated the formation of bound electronic states relaxed for ∝ 150 ps. We showed that the experimental data agreed with the computational simulation based on the numerical solution of the nonlinear Schroedinger equation only if these transient states were considered to arise from a direct light-induced process but not from the decay of radiatively generated free-electron-hole pairs. (orig.)

  6. Laser Plasmas: Effect of rippled laser beam on excitation of ion ...

    Indian Academy of Sciences (India)

    ... superimposed on a Gaussian laser beam in collisional unmagnetised plasma is investigated. From numerical computation, it is observed that self-focusing of main beam as well as ripple determine the growth dynamics of ripple with the distance of propagation. The effect of growing ripple on excitation of ion acoustic wave ...

  7. Spectrochemical analysis of powdered biological samples using transversely excited atmospheric carbon dioxide laser plasma excitation (United States)

    Zivkovic, Sanja; Momcilovic, Milos; Staicu, Angela; Mutic, Jelena; Trtica, Milan; Savovic, Jelena


    The aim of this study was to develop a simple laser induced breakdown spectroscopy (LIBS) method for quantitative elemental analysis of powdered biological materials based on laboratory prepared calibration samples. The analysis was done using ungated single pulse LIBS in ambient air at atmospheric pressure. Transversely-Excited Atmospheric pressure (TEA) CO2 laser was used as an energy source for plasma generation on samples. The material used for the analysis was a blue-green alga Spirulina, widely used in food and pharmaceutical industries and also in a few biotechnological applications. To demonstrate the analytical potential of this particular LIBS system the obtained spectra were compared to the spectra obtained using a commercial LIBS system based on pulsed Nd:YAG laser. A single sample of known concentration was used to estimate detection limits for Ba, Ca, Fe, Mg, Mn, Si and Sr and compare detection power of these two LIBS systems. TEA CO2 laser based LIBS was also applied for quantitative analysis of the elements in powder Spirulina samples. Analytical curves for Ba, Fe, Mg, Mn and Sr were constructed using laboratory produced matrix-matched calibration samples. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used as the reference technique for elemental quantification, and reasonably well agreement between ICP and LIBS data was obtained. Results confirm that, in respect to its sensitivity and precision, TEA CO2 laser based LIBS can be successfully applied for quantitative analysis of macro and micro-elements in algal samples. The fact that nearly all classes of materials can be prepared as powders implies that the proposed method could be easily extended to a quantitative analysis of different kinds of materials, organic, biological or inorganic.

  8. Polycarbonate resin drilling by longitudinally excited CO2 laser (United States)

    Uno, Kazuyuki; Kato, Masaya; Akitsu, Tetsuya; Jitsuno, Takahisa


    We developed a longitudinally excited CO2 laser with a long external cavity and investigated the drilling characteristics of polycarbonate resin. The CO2 laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 13 mm, a pulse power supply, a step-up transformer, a storage capacitance, and a long external optical cavity with a cavity length of 175 cm and an aperture of 9 mm. The CO2 laser produced a short pulse that had a spike pulse with the width of 282 ns and the energy of 0.45 mJ, a pulse tail with the length of 66.9 μs and the energy of 15.65 mJ, and a good circular beam. In a processing system, a ZnSe focusing lens with the focal length of 50 mm was used and the location of the focal plane was that of the sample surface. In the drilling of polycarbonate resin by the CO2 laser, the drilling characteristics depended on the number of pulses and the fluence was investigated. Clear drilling without carbonization was produced by the irradiation of 50 pulses or less with the fluence of 19 J/cm2 and the irradiation of 100 pulses or less with the fluence of 8 J/cm2. The clear drilling with the deepest depth in this work was 403 μm at the 50 pulses irradiation with the fluence of 19 J/cm2. The number of pulses and the fluence can control thermal influence in the CO2 laser processing of polycarbonate resin.

  9. Dental hard tissue drilling by longitudinally excited CO2 laser (United States)

    Uno, Kazuyuki; Yamamoto, Takuya; Akitsu, Tetsuya; Jitsuno, Takahisa


    We developed a longitudinally excited CO2 laser with a long optical cavity and investigated the drilling characteristics of dental hard tissue. The CO2 laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 13 mm, a pulse power supply, a step-up transformer, a storage capacitance, a spark gap, and a long optical cavity with a cavity length of 175 cm. The CO2 laser produced a short pulse that had a spike pulse with the width of 337 ns and the energy of 1.9 mJ, a pulse tail with the length of 180 μs and the energy of 37.6 mJ, and a doughnut-like beam. In the investigation, a sample was a natural drying human tooth (enamel and dentine). In a processing system, a ZnSe focusing lens with the focal length of 50 mm was used and the location of the focal plane was that of the sample surface. In 1 pulse irradiation, the drilling characteristics depended on the fluence was investigated. In the enamel and dentin drilling, the drilling depth increased with the fluence. The 1 pulse irradiation with the fluence of 21.5 J/cm2 produced the depth of 79.3 μm in the enamel drilling, and the depth of 152.7 μm in the dentin drilling. The short-pulse CO2 laser produced a deeper drilling depth at a lower fluence than long-pulse CO2 lasers in dental hard tissue processing.

  10. Effect of laser radiation on rat radiosensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Laprun, I.B.


    Quite a few experimental data have been obtained to date indicating that radioresistance of the organism is enhanced under the influence of electromagnetic emissions in the radiofrequency and optical ranges. But no studies were made of the possible radioprotective properties of coherent laser radiation. At the same time, it was demonstrated that the low-energy emission of optical quantum generators (lasers) in the red band stimulates the protective forces of the organism and accelerates regenerative processes; i.e., it induces effects that are the opposite of that of ionizing radiation. Moreover, it was recently demonstrated that there is activation of catalase, a radiosensitive enzyme that plays an important role in the metabolism of peroxide compounds, under the influence of lasers. For this reason, the effect of pre-exposure to laser beams on radiosensitivity of rats was tested.

  11. Heat pump processes induced by laser radiation (United States)

    Garbuny, M.; Henningsen, T.


    A carbon dioxide laser system was constructed for the demonstration of heat pump processes induced by laser radiation. The system consisted of a frequency doubling stage, a gas reaction cell with its vacuum and high purity gas supply system, and provisions to measure the temperature changes by pressure, or alternatively, by density changes. The theoretical considerations for the choice of designs and components are dicussed.

  12. Vapor deposition of polystyrene thin films by intense laser vibrational excitation

    DEFF Research Database (Denmark)

    Bubb, D.M.; Papantonakis, M.R.; Horwitz, J.S.


    -induced damage to the target can be seen. RIR-PLD is a fundamentally new approach to polymer thin film growth as the absorption of radiation resonant with vibrational modes allow the energy to be deposited into the polymer and transfers between macromolecules in such a way as to promote efficient, non......Polystyrene films were deposited using resonant infrared pulsed laser depositions (RIR-PLD). Thin films were grown on Si(1 1 1) wafers and NaCl substrates and analyzed by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The depositions were carried out...... in vacuum (10(-4)-10(-5) Torr) at wavelengths 3.28, 3.30, 3.42 and 3.48 mum which are resonant with CH2 stretching modes in the polymer. We also attempted to deposit a films using non-resonant infrared (RIR) excitation (2.90 mum). At this wavelength no films were deposited, and evidence for laser...

  13. Plasma channel undulator excited by high-order laser modes (United States)

    Wang, Jingwei; Schroeder, Carl; Zepf, Matt; Rykovanov, Sergey


    The possibility of utilizing plasma undulators and plasma accelerators to produce compact and economical ultraviolet and X-ray radiation sources has attracted considerable interest for a few decades. This interest has been driven by the great potential to decrease the threshold for accessing such sources, which are now mainly provided by a very few dedicated large-scale synchrotron or free-electron laser (FEL) facilities. However, the typically broad radiation bandwidth of such plasma devices limits the source brightness and makes it difficult for the FEL instability to develop. Here, using multi-dimensional electromagnetic particle-in-cell simulations, we demonstrate that a plasma undulator generated by the beating of a mixture of high-order laser modes propagating inside a plasma channel, leads to a few percent radiation bandwidth. The strength of the undulator can reach unity, the period can be less than a millimeter, and the total number of undulator periods can be significantly increased by a phase locking technique based on the longitudinal density modulation. According to analytical estimates and simulations, in the fully beam loaded regime, the electron current in the undulator can reach 0.3 kA, making such an undulator a potential candidate towards a table-top FEL.

  14. Advanced nanoparticle generation and excitation by lasers in liquids. (United States)

    Barcikowski, Stephan; Compagnini, Giuseppe


    Today, nanoparticles are widely implemented as functional elements onto surfaces, into volumes and as nano-hybrids, resulting for example in bioactive composites and biomolecule conjugates. However, only limited varieties of materials compatible for integration into advanced functional materials are available: nanoparticles synthesized using conventional gas phase processes are often agglomerated into micro powders that are hard to re-disperse into functional matrices. Chemical synthesis methods often lead to impurities of the nanoparticle colloids caused by additives and precursor reaction products. In the last decade, laser ablation and nanoparticle generation in liquids has proven to be a unique and efficient technique to generate, excite, fragment, and conjugate a large variety of nanostructures in a scalable and clean manner. This editorial briefly highlights selected recent advancements and critical aspects in the field of pulsed laser-based nanoparticle generation and manipulation, including exemplary strategies to harvest the unique properties of the laser-generated nanomaterials in the field of biomedicine and catalysis. The presented critical aspects address future assignments such as size control and scale-up.

  15. Parametric excitation of multiple resonant radiations from localized wavepackets

    CERN Document Server

    Conforti, Matteo; Mussot, Arnaud; Kudlinski, Alexandre


    Fundamental physical phenomena such as laser-induced ionization, driven quantum tunneling, Faraday waves, Bogoliubov quasiparticle excitations, and the control of new states of matter rely on time-periodic driving of the system. A remarkable property of such driving is that it can induce the localized (bound) states to resonantly couple to the continuum. Therefore experiments that allow for enlightening and controlling the mechanisms underlying such coupling are of paramount importance. We implement such an experiment in a special fiber optics system characterized by a dispersion oscillating along the propagation coordinate, which mimics "time". The quasi-momentum associated with such periodic perturbation is responsible for the efficient coupling of energy from the localized wave-packets sustained by the fiber nonlinearity into free-running linear dispersive waves (continuum), at multiple resonant frequencies. Remarkably, the observed resonances can be explained by means of a unified approach, regardless of ...

  16. Interaction of laser radiation with urinary calculi


    Mayo, M E


    Urolithias, calculus formation in the urinary system, affects 5 – 10% of the population and is a painful and recurrent medical condition. A common approach in the treatment of calculi is the use of laser radiation, a procedure known as laser lithotripsy, however, the technique has not yet been fully optimised. This research examines the experimental parameters relevant to the interactions of the variable microsecond pulsed holmium laser (λ = 2.12 μm, τp = 120 – 800 μs, I ~ 3 MW...

  17. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Microwave generation in an optical breakdown plasma created by modulated laser radiation (United States)

    Antipov, A. A.; Grasyuk, Arkadii Z.; Losev, Leonid L.; Soskov, V. I.


    It was established that when laser radiation, intensity modulated at a frequency of 2.2 GHz, interacted with an optical breakdown plasma which it had created, a microwave component appeared in the thermal emf of the plasma. The amplitude of the microwave thermal emf reached 0.7 V for a laser radiation intensity of 6 GW/cm2. Laser radiation with λL = 1.06 μm was converted to the microwave range with λmω = 13 cm in the optical breakdown plasma. A microwave signal power of ~ 0.5 W was obtained from a laser power of ~ 5 MW.

  18. Radiation from laser accelerated electron bunches: Coherent terahertz and femtosecond X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Leemans, W.P.; Esarey, E.; van Tilborg, J.; Michel, P.A.; Schroeder, C.B.; Toth, Cs.; Geddes, C.G.R.; Shadwick, B.A.


    Electron beam based radiation sources provide electromagnetic radiation for countless applications. The properties of the radiation are primarily determined by the properties of the electron beam. Compact laser driven accelerators are being developed that can provide ultra-short electron bunches (femtosecond duration) with relativistic energies reaching towards a GeV. The electron bunches are produced when an intense laser interacts with a dense plasma and excites a large amplitude plasma density modulation (wakefield) that can trap background electrons and accelerate them to high energies. The short pulse nature of the accelerated bunches and high particle energy offer the possibility of generating radiation from one compact source that ranges from coherent terahertz to gamma rays. The intrinsic synchronization to a laser pulse and unique character of the radiation offers a wide range of possibilities for scientific applications. Two particular radiation source regimes are discussed: Coherent terahertz emission and x-ray emission based on betatron oscillations and Thomson scattering.

  19. Laser control of molecular excitations in stochastic dissipative media. (United States)

    Tremblay, Jean Christophe


    In the present work, ideas for controlling photochemical reactions in dissipative environments using shaped laser pulses are presented. New time-local control algorithms for the stochastic Schrödinger equation are introduced and compared to their reduced density matrix analog. The numerical schemes rely on time-dependent targets for guiding the reaction along a preferred path. The methods are tested on the vibrational control of adsorbates at metallic surfaces and on the ultrafast electron dynamics in a strong dissipative medium. The selective excitation of the specific states is achieved with improved yield when using the new algorithms. Both methods exhibit similar convergence behavior and results compare well with those obtained using local optimal control for the reduced density matrix. The favorable scaling of the methods allows to tackle larger systems and to control photochemical reactions in dissipative media of molecules with many more degrees of freedom.

  20. White light source with laser-excited phosphor (United States)

    Abdullaev, O. R.; Aluev, A. V.; Akhmerov, Yu. L.; Kourova, N. V.; Mezhennyi, M. V.; Chelny, A. A.


    The principles of operation of a white light source based on a remote phosphor, made of cerium-doped yttrium aluminium garnet (YAG : Ce3+), whose luminescence is excited by a blue laser diode, are considered. The colorimetric and photometric characteristics of phosphors of different types are analysed as functions of the phosphor film thickness. The following parameters are obtained at an output power of 1 W and a wavelength of 445±3 nm in the cw regime: luminous flux of 165 lm, correlated colour temperature of 5595 K, colour rendering index of 66, colour coordinates x = 0.3303 and y = 0.3427, luminous efficiency of 165 lm W‑1, and light efficacy of 30 lm W‑1. These characteristics are comparable with similar parameters of commercial white LEDs.

  1. Effect of the excitation source on the quantum-yield measurements of rhodamine B laser dye studied using thermal-lens technique. (United States)

    Bindhu, C V; Harilal, S S


    A dual-beam transient thermal-lens technique was employed for the determination of absolute fluorescence quantum-yield measurements of Rhodamine B laser dye in different solvents. We investigated the effect of excitation on the absolute fluorescence quantum yield of Rhodamine B. 514 nm radiation from an argon ion laser was used as a cw excitation source and 532 nm pulses from a Q-switched Nd:YAG laser were used as a pulsed excitation source. The fluorescence quantum-yield values were found to be strongly influenced by environmental effects as well as the transient nature of the excitation beam. Our results also indicate that parameters, like the concentration of the dye solution, aggregate formation and excited state absorption, affect the absolute values of the fluorescence yield significantly.

  2. Excitability and self-pulsations near homoclinic bifurcations in semiconductor laser systems

    NARCIS (Netherlands)

    Krauskopf, B.; Schneider, K.; Sieber, J.; Wieczorek, S.; Wolfrum, M.


    Many laser systems show self-pulsations with a large amplitude that are born suddenly in a homoclinic bifurcation. Just before the onset of these self-pulsations the laser is excitable where the excitability threshold is formed by the stable manifold of a saddle point. We show that there exists a

  3. Femtosecond laser electronic excitation tagging for aerodynamic and thermodynamic measurements (United States)

    Calvert, Nathan David

    This thesis presents applications of Femtosecond Laser Electronic Excitation Tagging (FLEET) to a variety of aerodynamic and thermodynamic measurements. FLEET tagged line characteristics such as intensity, width and spectral features are investigated in various flow conditions (pressure, temperature, velocity, steadiness, etc.) and environments (gas composition) for both temporally and spatially instantaneous and averaged data. Special attention is drawn to the nature of first and second positive systems of molecular nitrogen and the ramifications on FLEET measurements. Existing laser-based diagnostic techniques are summarized and FLEET is directly compared with Particle Image Velocimetry (PIV) in various low speed flows. Multidimensional velocity, acceleration, vorticity and other flow parameters are extracted in supersonic free jets and within an enclosed in-draft tunnel test section. Probability distribution functions of the mean and standard deviation of critical flow parameters are unveiled by utilizing a Bayesian statistical framework wherein likelihood functions are established from prior and posterior distributions. Advanced image processing techniques based on fuzzy logic are applied to single-shot FLEET images with low signal-to-noise ratio to improve image quality and reduce uncertainty in data processing algorithms. Lastly, FLEET second positive and first negative emission are considered at a wide range of pressures to correct for changes in select rovibrational peak magnitude and shape due to density from which bulk gas temperature may be extracted.

  4. Laser excitation of the n=3 level of positronium for antihydrogen production

    CERN Document Server

    Aghion, S; Ariga, A; Ariga, T; Bonomi, G; Braunig, P; Bremer, J; Brusa, R S; Cabaret, L; Caccia, M; Caravita, R; Castelli, F; Cerchiari, G; Chlouba, K; Cialdi, S; Comparat, D; Consolati, G; Demetrio, A; Di Noto, L; Doser, M; Dudarev, A; Ereditato, A; Evans, C; Ferragut, R; Fesel, J; Fontana, A; Forslund, O K; Gerber, S; Giammarchi, M; Gligorova, A; Gninenko, S N; Guatieri, F; Haider, S; Holmestad, H; Huse, T; Jernelv, I L; Jordan, E; Kellerbauer, A; Kimura, M; Koetting, T; Krasnicky, D; Lagomarsino, V; Lansonneur, P; Lebrun, P; Lehner, S; Liberadzka, J; Malbrunot, C; Mariazzi, S; Marx, L; Matveev, V A; Mazzotta, Z; Nebbia, G; Nedelec, P; Oberthaler, M K; Pacifico, N; Pagano, D; Penasa, L; Petracek, V; Pistillo, C; Prelz, F; Prevedelli, M; Ravelli, L; Resch, L; Rienacker, B; Røhne, O M; Rotondi, A; Sacerdoti, M; Sandaker, H; Santoro, R; Scampoli, P; Smestad, L; Sorrentino, F; Spacek, M; Storey, J; Strojek, I M; Testera, G; Tietje, I; Vamosi, S; Widmann, E; Yzombard, P; Zmeskal, J; Zurlo, N.


    We demonstrate laser excitation of the n=3 state of positronium (Ps) in vacuum. A specially designed high-efficiency pulsed slow positron beam and single shot positronium annihilation lifetime spectroscopy were used to produce and detect Ps. Pulsed laser excitation of n=3 level at 205 nm was monitored via Ps photoionization induced by a second intense laser pulse at 1064 nm. About 15% of the overall positronium emitted in vacuum was excited to n=3 and photoionized. Saturation of both the n=3 excitation and the following photoionization was observed and is explained by a simple rate equation model. Scanning the laser frequency allowed us to extract the positronium transverse temperature related to the width of the Doppler-broadened line. Moreover, preliminary observation of excitation to Rydberg states (n = 15...17) using n=3 as intermediate level was observed, giving an independent confirmation of efficient excitation to the 33P state.

  5. Doppler- and recoil-free laser excitation of Rydberg states via three-photon transitions


    Ryabtsev, I. I.; Beterov, I. I.; Tretyakov, D. B.; Entin, V. M.; Yakshina, E. A.


    Three-photon laser excitation of Rydberg states by three different laser beams can be arranged in a star-like geometry that simultaneously eliminates the recoil effect and Doppler broadening. Our analytical and numerical calculations for a particular laser excitation scheme 5S_{1/2}->5P_{3/2}->6S_{1/2}->nP in Rb atoms have shown that compared to the one- and two-photon laser excitation this approach provides much narrower line width and longer coherence time for both cold atom samples and hot...

  6. Particular features of the emission of radiation by a superluminally excited Raman-active medium (United States)

    Arkhipov, R. M.


    Particular features of the emission of radiation by a Raman-active medium excited by a sequence of ultrashort superluminal pulses have been studied theoretically. It is shown that such an excitation gives rise to the possibility of obtaining unipolar rectangular videopulses the duration and amplitude of which depend on the velocity of propagation of the excitation over the medium.

  7. Livermore experience: contributions of J. H. Eberly to laser excitation theory

    Energy Technology Data Exchange (ETDEWEB)

    Shore, B W; Kulander, K; Davis, J I


    This article summarizes the developing understanding of coherent atomic excitation, as gained through a collaboration of J. H. Eberly with the Laser Isotope Separation Program of the Lawrence Livermore National Laboratory, particularly aspects of coherence, population trapping, multilevel multiphoton excitation sequences, analytic solutions to multistate excitation chains, the quasicontinuum, pulse propagation, and noise. In addition to the discovery of several curious and unexpected properties of coherent excitation, mentioned here, the collaboration provided an excellent example of unexpected benefits from investment into basic research.

  8. Laser Two-Proton Excited Fluorometric Detection for High Pressure Liquid Chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Sepaniak, Michael J. [Iowa State Univ., Ames, IA (United States)


    The aim of this thesis is to explore the potential of the laser in fluorometric HPLC detection. To this end research efforts which show the improved selectivity (without loss of sensitivity) of laser two-photon excited fluorometric (LTPEF) detection will be presented, followed by suggestions for further study involving additional modes of laser fluorometric detection.

  9. Radiative trapping in intense laser beams

    CERN Document Server

    Kirk, J G


    The dynamics of electrons in counter-propagating, circularly polarized laser beams are shown to exhibit attractors whose ability to trap particles depends on the ratio of the beam intensities and a single parameter describing radiation reaction. Analytical expressions are found for the underlying limit cycles and the parameter range in which they are stable. In high-intensity optical pulses, where radiation reaction strongly modifies the trajectories, the production of collimated gamma-rays and the initiation of non-linear cascades of electron-positron pairs can be optimized by a suitable choice of the intensity ratio.

  10. Longitudinally excited CO2 laser with short laser pulse operating at high repetition rate (United States)

    Li, Jianhui; Uno, Kazuyuki; Akitsu, Tetsuya; Jitsuno, Takahisa


    A short-pulse longitudinally excited CO2 laser operating at a high repetition rate was developed. The discharge tube was made of a 45 cm-long or 60 cm-long dielectric tube with an inner diameter of 16 mm and two metallic electrodes at the ends of the tube. The optical cavity was formed by a ZnSe output coupler with a reflectivity of 85% and a high-reflection mirror. Mixed gas (CO2:N2:He = 1:1:2) was flowed into the discharge tube. A high voltage of about 33 kV with a rise time of about 200 ns was applied to the discharge tube. At a repetition rate of 300 Hz and a gas pressure of 3.4 kPa, the 45 cm-long discharge tube produced a short laser pulse with a laser pulse energy of 17.5 mJ, a spike pulse energy of 0.2 mJ, a spike width of 153 ns, and a pulse tail length of 90 μs. The output power was 5.3 W. The laser pulse waveform did not depend on the repetition rate, but the laser beam profile did. At a low repetition rate of less than 50 Hz, the laser beam had a doughnut-like shape. However, at a high repetition rate of more than 150 Hz, the discharge concentrated at the center of the discharge tube, and the intensity at the center of the laser beam was higher. The laser beam profile depended on the distribution of the discharge. An output power of 7.0 W was achieved by using the 60 cm-long tube.

  11. Dependence of laser-induced fluorescence on exciting-laser power: partial saturation and laser - plasma interaction (United States)

    Voráč, Jan; Dvořák, Pavel; Procházka, Vojtěch; Morávek, Tomas; Ráhel, Jozef


    In recent publications on laser-induced fluorescence (LIF), the measurements are usually constricted to the region of weak exciting-laser power - the so called linear LIF. In this work, a practical formula describing the dependence of partially saturated fluorescence on the exciting-laser power is derived, together with practical implementation suggestions and comments on its limitations. In the conclusion, the practical formula F({E}_L)= {α{E}_L}/{1+β {E}_L} is proposed with the limitation for validity β EL ≤ 0.4, where α EL is the hypothetical linear fluorescence without saturation effects, and a more general formula is derived, which is valid for higher values of α EL as well. Extending the range of exciting laser power to the region of partial saturation enhances the signal-to-noise ratio. Such measurements in a surface dielectric barrier discharge further reveal discharge disruption by photoelectrons emitted from the dielectric surface. Methods of control and solution of this problem are discussed. Contribution to the topical issue "The 14th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XIV)", edited by Nicolas Gherardi, Ronny Brandenburg and Lars Stollenwark

  12. Xenon plasma sustained by pulse-periodic laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Rudoy, I. G.; Solovyov, N. G.; Soroka, A. M.; Shilov, A. O.; Yakimov, M. Yu., E-mail: [Russian Academy of Sciences, A. Ishlinsky Institute for Problems in Mechanics (Russian Federation)


    The possibility of sustaining a quasi-stationary pulse-periodic optical discharge (POD) in xenon at a pressure of p = 10–20 bar in a focused 1.07-μm Yb{sup 3+} laser beam with a pulse repetition rate of f{sub rep} ⩾ 2 kHz, pulse duration of τ ⩾ 200 μs, and power of P = 200–300 W has been demonstrated. In the plasma development phase, the POD pulse brightness is generally several times higher than the stationary brightness of a continuous optical discharge at the same laser power, which indicates a higher plasma temperature in the POD regime. Upon termination of the laser pulse, plasma recombines and is then reinitiated in the next pulse. The initial absorption of laser radiation in successive POD pulses is provided by 5p{sup 5}6s excited states of xenon atoms. This kind of discharge can be applied in plasma-based high-brightness broadband light sources.

  13. Calculation and analysis of the number of return photons from sodium laser beacon excited by the long pulse laser with circular polarization (United States)

    Liu, Xiang-Yuan; Qian, Xian-Mei; Li, Yu-Jie; Rao, Rui-Zhong


    The number of return photons from sodium laser beacon (SLB) greatly suffers down-pumping, recoil, and geomagnetic field when the long pulse laser with circular polarization interacts with sodium atoms in the mesosphere. Considering recoil and down-pumping effects on the number of return photons from SLB, the spontaneous radiation rates are obtained by numerical computations and fittings. Furthermore, combining with the geomagnetic field effects, a new expression is achieved for calculating the number of return photons. By using this expression and considering the stochastic distribution of laser intensity in the mesosphere under different turbulence models for atmosphere, the number of return photons excited by the narrow-band single mode laser and that by the narrow-band three-mode laser are respectively calculated. The results show that the narrow-band three-mode laser with a specific spectrum structure has a higher spontaneous radiation rate and more return photons than a narrow-band single mode laser. Of note, the effect of the atmospheric turbulence on the number of return photons is remarkable. Calculation results indicate that the number of return photons under the HV5/7 model for atmospheric turbulence is much higher than that under the Greenwood and ModHV models.

  14. Study of ultra-high gradient wakefield excitation by intense ultrashort laser pulses in plasma (United States)

    Kotaki, Hideyuki; Kando, Masaki; Oketa, Takatsugu; Masuda, Shinichi; Koga, James K.; Kondo, Shuji; Kanazawa, Shuhei; Yokoyama, Takashi; Matoba, Toru; Nakajima, Kazuhisa


    We investigate a laser wakefield excited by intense laser pulses, and the possibility of generating an intense bright electron source by an intense laser pulse. The coherent wakefield excited by 2 TW, 50 fs laser pulses in a gas-jet plasma around 1018 cm-3 is measured with a time-resolved frequency domain interferometer (FDI). The results show an accelerating wakefield excitation of 20 GeV/m with good coherency. This is the first time-resolved measurement of laser wakefield excitation in a gas-jet plasma. The experimental results agree with the simulation results and linear theory. The pump-probe interferometer system of FDI will be modified to the optical injection system as a relativistic electron beam injector. In 1D particle in cell simulation we obtain results of high quality intense electron beam generation.

  15. The effect of excitation wavelength on dynamics of laser-produced tin plasma (United States)

    Harilal, S. S.; Sizyuk, T.; Hassanein, A.; Campos, D.; Hough, P.; Sizyuk, V.


    We investigated the effect of the excitation wavelength on the density evolution of laser-produced tin plasmas, both experimentally and numerically. For producing plasmas, Sn targets were excited with either 10.6 μm CO2 laser or 1.06 μm Nd:yttrium aluminum garnet laser; both are considered to be potential excitation lasers for extreme ultraviolet lithography laser-produced plasma light sources. The electron density of the plasma during the isothermal expansion regime was estimated using an interferometric technique. The Stark broadening of isolated singly-ionized emission was employed for deducing the density during the plasma adiabatic expansion regime. Our results indicate that the excitation source wavelength determines the initial density of the plasma, as well the plume expansion dynamics. Numerical simulation using HEIGHTS simulation package agrees well with the experimentally measured density profile.

  16. Single fiber laser based wavelength tunable excitation for CRS spectroscopy. (United States)

    Su, Jue; Xie, Ruxin; Johnson, Carey K; Hui, Rongqing


    We demonstrate coherent Raman spectroscopy (CRS) using a tunable excitation source based on a single femtosecond fiber laser. The frequency difference between the pump and the Stokes pulses was generated by soliton self-frequency shifting (SSFS) in a nonlinear optical fiber. Spectra of C-H stretches of cyclohexane were measured simultaneously by stimulated Raman gain (SRG) and coherent anti-Stokes Raman scattering (CARS) and compared. We demonstrate the use of spectral focusing through pulse chirping to improve CRS spectral resolution. We analyze the impact of pulse stretching on the reduction of power efficiency for CARS and SRG. Due to chromatic dispersion in the fiber-optic system, the differential pulse delay is a function of Stokes wavelength. This differential delay has to be accounted for when performing spectroscopy in which the Stokes wavelength needs to be scanned. CARS and SRG signals were collected and displayed in two dimensions as a function of both the time delay between chirped pulses and the Stokes wavelength, and we demonstrate how to find the stimulated Raman spectrum from the two-dimensional plots. Strategies of system optimization consideration are discussed in terms of practical applications.

  17. Discharge modulation noise in He---Ne laser radiation

    NARCIS (Netherlands)

    Bolwijn, P.T.


    Discharge modulation noise in He---Ne laser radiation is considered theoretically, including explicitly the laser oscillator properties. Experiments reported previously by us and other authors are in agreement with our analysis.

  18. How Plasmonic excitation influences the LIPSS formation on diamond during multipulse femtosecond laser irradiation ?

    Directory of Open Access Journals (Sweden)

    Abdelmalek Ahmed


    Full Text Available A generalized plasmonic model is proposed to calculate the nanostructure period induced by multipulse laser femtosecond on diamond at 800 nm wavelengths. We follow the evolution of LIPSS formation by changing diamond optical parameters in function of electron plasma excitation during laser irradiation. Our calculations shows that the ordered nanostructures can be observed only in the range of surface plasmon polariton excitation.

  19. Study of ultra-high gradient wakefield excitation by intense ultrashort laser pulses in plasma

    CERN Document Server

    Kotaki, H


    We investigate a mechanism of nonlinear phenomena in laser-plasma interaction, a laser wakefield excited by intense laser pulses, and the possibility of generating an intense bright electron source by an intense laser pulse. We need to understand and further employ some of these phenomena for our purposes. We measure self-focusing, filamentation, and the anomalous blueshift of the laser pulse. The ionization of gas with the self-focusing causes a broad continuous spectrum with blueshift. The normal blueshift depends on the laser intensity and the plasma density. We, however, have found different phenomenon. The laser spectrum shifts to fixed wavelength independent of the laser power and gas pressure above some critical power. We call the phenomenon 'anomalous blueshift'. The results are explained by the formation of filaments. An intense laser pulse can excite a laser wakefield in plasma. The coherent wakefield excited by 2 TW, 50 fs laser pulses in a gas-jet plasma around 10 sup 1 sup 8 cm sup - sup 3 is mea...

  20. A DC excited waveguide multibeam CO2 laser using high frequency ...

    Indian Academy of Sciences (India)

    A DC excited waveguide multibeam CO2 laser is reported having six glass discharge tubes. Simultaneous excitation of DC discharge in all sections is achieved by producing pre-ionization using an auxiliary high frequency pulsed discharge along with its other advantages. Maximum 170 W output power is obtained with all ...

  1. Discrete excitation of mode pulses using a diode-pumped solid-state digital laser

    CSIR Research Space (South Africa)

    Ngcobo, Sandile


    Full Text Available In this paper, we experimentally demonstrate novel method of generating discrete excitation of on-demand Lagaurre-Gaussian (LG) mode pulses, in a diode pumped solid-state digital laser. The digital laser comprises of an intra-cavity spatial light...

  2. Ponderomotive dressing of doubly-excited states with intensity-controlled laser light

    Directory of Open Access Journals (Sweden)

    Ding Thomas


    Full Text Available We laser-dress several doubly-excited states in helium. Tuning the coupling-laser intensity from perturbative to the strong-coupling regime, we are able to measure phases imprinted on the two-electron wavefunctions, and observe a new continuum coupling mechanism.

  3. Disorder-induced localization of excitability in an array of coupled lasers (United States)

    Lamperti, M.; Perego, A. M.


    We report on the localization of excitability induced by disorder in an array of coupled semiconductor lasers with a saturable absorber. Through numerical simulations we show that the exponential localization of excitable waves occurs if a certain critical amount of randomness is present in the coupling coefficients among the lasers. The results presented in this Rapid Communication demonstrate that disorder can induce localization in lattices of excitable nonlinear oscillators, and can be of interest in the study of photonics-based random networks, neuromorphic systems, and, by analogy, in biology, in particular, in the investigation of the collective dynamics of neuronal cell populations.

  4. Plastic lab-on-a-chip for fluorescence excitation with integrated organic semiconductor lasers. (United States)

    Vannahme, Christoph; Klinkhammer, Sönke; Lemmer, Uli; Mappes, Timo


    Laser light excitation of fluorescent markers offers highly sensitive and specific analysis for bio-medical or chemical analysis. To profit from these advantages for applications in the field or at the point-of-care, a plastic lab-on-a-chip with integrated organic semiconductor lasers is presented here. First order distributed feedback lasers based on the organic semiconductor tris(8-hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyril)-4H-pyrane (DCM), deep ultraviolet induced waveguides, and a nanostructured microfluidic channel are integrated into a poly(methyl methacrylate) (PMMA) substrate. A simple and parallel fabrication process is used comprising thermal imprint, DUV exposure, evaporation of the laser material, and sealing by thermal bonding. The excitation of two fluorescent marker model systems including labeled antibodies with light emitted by integrated lasers is demonstrated.

  5. Negative Binomial States of the Radiation Field and their Excitations are Nonlinear Coherent States


    Wang, Xiao-Guang; Fu, Hong-Chen


    We show that the well-known negative binomial states of the radiation field and their excitations are nonlinear coherent states. Excited nonlinear coherent state are still nonlinear coherent states with different nonlinear functions. We finally give exponential form of the nonlinear coherent states and remark that the binomial states are not nonlinear coherent states.

  6. Analysis of UV-excited fluorochromes by flow cytometry using near-ultraviolet laser diodes. (United States)

    Telford, William G


    Violet laser diodes have become common and reliable laser sources for benchtop flow cytometers. While these lasers are very useful for a variety of violet and some ultraviolet-excited fluorochromes (e.g., DAPI), they do not efficiently excite most UV-stimulated probes. In this study, the next generation of InGaN near-UV laser diodes (NUVLDs) emitting in the 370-375-nm range have been evaluated as laser sources for cuvette-based flow cytometers. Several NUVLDs, ranging in wavelength from 370 to 374 nm and in power level from 1.5 to 10 mW, were mounted on a BD Biosciences LSR II and evaluated for their ability to excite cells labeled with the UV DNA binding dye DAPI, several UV phenotyping fluorochromes (including Alexa Fluor 350, Marina Blue, and quantum dots), and the fluorescent calcium chelator indo-1. NUVLDs at the 8-10-mW power range gave detection sensitivity levels comparable to more powerful solid-state and ion laser sources, using low-fluorescence microsphere beads as measurement standards. NUVLDs at all tested power levels allowed extremely high-resolution DAPI cell cycle analysis, and sources in the 8-10-mW power range excited Alexa Fluor 350, Marina Blue, and a variety of quantum dots at virtually the same signal-to-noise ratios as more powerful UV sources. These evaluations indicate that near-UV laser diodes installed on a cuvette-based flow cytometer performed nearly as well as more powerful solid-state UV lasers on the same instrumentation, and comparably to more powerful ion lasers on a jet-in-air system, and. Despite their limited power, integration of these small and inexpensive lasers into benchtop flow cytometers should allow the use of flow cytometric applications requiring UV excitation on a wide variety of instruments. Copyright 2004 Wiley-Liss, Inc.

  7. Low-cost photoacoustic imaging systems based on laser diode and light-emitting diode excitation

    Directory of Open Access Journals (Sweden)

    Qingkai Yao


    Full Text Available Photoacoustic imaging, an emerging biomedical imaging modality, holds great promise for preclinical and clinical researches. It combines the high optical contrast and high ultrasound resolution by converting laser excitation into ultrasonic emission. In order to generate photoacoustic signal efficiently, bulky Q-switched solid-state laser systems are most commonly used as excitation sources and hence limit its commercialization. As an alternative, the miniaturized semiconductor laser system has the advantages of being inexpensive, compact, and robust, which makes a significant effect on production-forming design. It is also desirable to obtain a wavelength in a wide range from visible to near-infrared spectrum for multispectral applications. Focussing on practical aspect, this paper reviews the state-of-the-art developments of low-cost photoacoustic system with laser diode and light-emitting diode excitation source and highlights a few representative installations in the past decade.

  8. Doppler- and recoil-free laser excitation of Rydberg states via three-photon transitions

    Energy Technology Data Exchange (ETDEWEB)

    Ryabtsev, I. I.; Beterov, I. I.; Tretyakov, D. B.; Entin, V. M.; Yakshina, E. A. [A. V. Rzhanov Institute of Semiconductor Physics SB RAS, Prospekt Lavrentyeva 13, 630090 Novosibirsk (Russian Federation)


    Three-photon laser excitation of Rydberg states by three different laser beams can be arranged in a starlike geometry that simultaneously eliminates the recoil effect and Doppler broadening. Our analytical and numerical calculations for a particular laser excitation scheme 5S{sub 1/2}{yields}5P{sub 3/2}{yields}6S{sub 1/2}{yields}nP in Rb atoms have shown that, compared to the one- and two-photon laser excitation, this approach provides much narrower linewidth and longer coherence time for both cold atom samples and hot vapors, if the intermediate one-photon resonances of the three-photon transition are detuned by more than respective single-photon Doppler widths. This method can be used to improve fidelity of Rydberg quantum gates and precision of spectroscopic measurements in Rydberg atoms.

  9. Laser method for simulating the transient radiation effects of semiconductor (United States)

    Li, Mo; Sun, Peng; Tang, Ge; Wang, Xiaofeng; Wang, Jianwei; Zhang, Jian


    In this paper, we demonstrate the laser simulation adequacy both by theoretical analysis and experiments. We first explain the basic theory and physical mechanisms of laser simulation of transient radiation effect of semiconductor. Based on a simplified semiconductor structure, we describe the reflection, optical absorption and transmission of laser beam. Considering two cases of single-photon absorption when laser intensity is relatively low and two-photon absorption with higher laser intensity, we derive the laser simulation equivalent dose rate model. Then with 2 types of BJT transistors, laser simulation experiments and gamma ray radiation experiments are conducted. We found good linear relationship between laser simulation and gammy ray which depict the reliability of laser simulation.

  10. Laser-plasma-based Space Radiation Reproduction in the Laboratory. (United States)

    Hidding, B; Karger, O; Königstein, T; Pretzler, G; Manahan, G G; McKenna, P; Gray, R; Wilson, R; Wiggins, S M; Welsh, G H; Beaton, A; Delinikolas, P; Jaroszynski, D A; Rosenzweig, J B; Karmakar, A; Ferlet-Cavrois, V; Costantino, A; Muschitiello, M; Daly, E


    Space radiation is a great danger to electronics and astronauts onboard space vessels. The spectral flux of space electrons, protons and ions for example in the radiation belts is inherently broadband, but this is a feature hard to mimic with conventional radiation sources. Using laser-plasma-accelerators, we reproduced relativistic, broadband radiation belt flux in the laboratory, and used this man-made space radiation to test the radiation hardness of space electronics. Such close mimicking of space radiation in the lab builds on the inherent ability of laser-plasma-accelerators to directly produce broadband Maxwellian-type particle flux, akin to conditions in space. In combination with the established sources, utilisation of the growing number of ever more potent laser-plasma-accelerator facilities worldwide as complementary space radiation sources can help alleviate the shortage of available beamtime and may allow for development of advanced test procedures, paving the way towards higher reliability of space missions.

  11. Emission of radiation by a resonance medium excited with a variable superluminal velocity (United States)

    Arkhipov, R. M.; Pakhomov, A. V.


    Specific properties of the radiation emitted by a spatially modulated resonance medium excited by an ultrashort light pulse propagating through the medium at a variable superluminal velocity are analyzed. In so doing, frequencies different from that of the resonance transition of the medium may appear in the emission spectrum. It is demonstrated that, in contrast to an earlier studied case of medium excitation at constant velocity, variation of the excitation velocity leads to generation of a spectral continuum, the boundaries of which are determined by the range of variation of the medium-excitation velocity.

  12. Comparison of luminescence spectra of natural spodumene under KrCl laser and e-beam excitation

    Energy Technology Data Exchange (ETDEWEB)

    Lipatov, E.I. [High Current Electronics Institute SB RAS, 2/3, Akademichesky Avenue, Tomsk 634055 (Russian Federation)]. E-mail:; Orlovskii, V.M. [High Current Electronics Institute SB RAS, 2/3, Akademichesky Avenue, Tomsk 634055 (Russian Federation); Tarasenko, V.F. [High Current Electronics Institute SB RAS, 2/3, Akademichesky Avenue, Tomsk 634055 (Russian Federation); Solomonov, V.I. [Institute of Electrophysics UB RAS, 106, Amundsen Street, Ekaterinburg (Russian Federation)


    Spectral characteristics of pulsed photoluminescence (PL) and pulsed cathodoluminescence (PCL) of a natural spodumene were investigated. PL was excited by laser radiation at 222 nm with pulse duration of 10 ns at FWHM. PCL was excited by electron beams with pulse duration from 0.1 up to 4 ns and with current densities of 40-200 A/cm{sup 2}. There was a dominant broad band at 600 nm due to the manganese impurity in PCL spectra. But in PL spectra, the orange band had the intensity comparable with intensities of intrinsic defect bands. At sample cooling by liquid nitrogen, the intensity of orange band in the PCL spectrum increased by two times and the short-wave shoulder of the band reduced.

  13. Synchrotron radiation photoionization mass spectrometry of laser ablated species


    Alvarez Ruiz, Jesus; Casu, A.; Coreno, M.; De Simone, M.; Hoyos Campos, L.M.; Juarez-Reyes, A.M.; Kivimäki, A.; Orlando, S.; Sanz, M.; Spezzani, C.; Stankiewicz, M; Trucchi, D. M.


    The present paper describes an experimental apparatus suitable to create and study free clusters by combining laser ablation and synchrotron radiation. First tests on sulfur samples, S, showed the production, through laser ablation, of neutral Sn clusters (n = 1–8). These clusters were ionized using synchrotron radiation at photon energies from 160 eV to 175 eV, across the S 2p core edge. The feasibility of such combined ablation–synchrotron radiation experiments is demonstrated, opening new ...

  14. Helical magnetized wiggler for synchrotron radiation laser

    CERN Document Server

    Wang Mei; Hirshfield, J L


    A helical magnetized iron wiggler has been built for a novel infrared synchrotron radiation laser (SRL) experiment. The wiggler consists of four periods of helical iron structure immersed in a solenoid field. This wiggler is to impart transverse velocity to a prebunched 6 MeV electron beam, and thus to obtain a desired high orbit pitch ratio for the SRL. Field tapering at beam entrance is considered and tested on a similar wiggler. Analytic and simulated characteristics of wigglers of this type are discussed and the performance of the fabricated wigglers is demonstrated experimentally. A 4.7 kG peak field was measured for a 6.4 mm air gap and a 5.4 cm wiggler period at a 20 kG solenoid field. The measured helical fields compare favorably with the analytical solution. This type of helical iron wigglers has the potential to be scaled to small periods with strong field amplitude.

  15. Сomparative Analysis of 0.266 and 0.355 µm Fluorescence Excitation Wavelengths for Laser Fluores-Cence Monitoring of Oil Pollution Detection

    Directory of Open Access Journals (Sweden)

    M. L. Belov


    Full Text Available The on-line detection of pipeline spillage is really essential for the fast oil spill response to the ecological and economical consequences. However existing on-line pipelines spillage detection systems have a sensibility of 0.2 – 1 % of pipe flow and do not detect the smaller-sized spillages.For unpeopled or sparsely populated regions an advanced technique for detection of pipeline spillages (including low-intensity ones is to monitor oil pollution (petroleum spills on the earth surface along the pipeline using, for example, an air drone.The laser remote sensing method is an effective method to detect the pipelines spillage.The paper is dedicated to development of laser fluorescence detection method of oil pollution. The remote sensing laser method to monitor oil pollution is based on the fluorescence excitation of oil in UV spectral band and on the data record of the earth surface laser-induced fluorescence radiation.For laser fluorescence method of monitoring oil pollution the paper presents a comparative analysis  of 0.266 and 0.355 µm wavelengths of the fluorescence excitation in terms of earth atmosphere propagation, eye-safety, laser characteristics, and petroleum fluorescence excitation efficiency.It is shown that in terms of eye-safety, laser characteristics, and propagation in the earth atmosphere a 0.355 µm laser wavelength of the fluorescence excitation has a sure advantage.In the context of petroleum fluorescence excitation efficiency a 0.266 µm laser wavelength of the fluorescence excitation has the advantage, but this advantage depends heavily on the petroleum base. For low-sulfur (sweet oil for instance,  it is not that big.At large, in solving the task of oil pollution detection because of the oil pipeline spillages the 0.355 µm wavelength of fluorescence excitation ought to be preferable. However, when creating a monitoring system for the pipeline with a specific petroleum base the irreversible decision depends on the

  16. Studying laser radiation effect on steel structure and properties

    Directory of Open Access Journals (Sweden)

    А. М. Gazaliyev


    Full Text Available There was studied the effect of laser radiation on the structure and properties of annealed and tempered steel with different content of carbon. For surface hardening there was used a laser complex equipped with Nd: YAG pulse laser with power density up to 30 kW/сm2. As a result of the carried-out studies there were calculated characteristics of laser, steel microstructure and properties.

  17. Coherent blue emission generated by Rb two-photon excitation using diode and femtosecond lasers (United States)

    Lopez, Jesus P.; Moreno, Marco P.; de Miranda, Marcio H. G.; Vianna, Sandra S.


    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.

  18. [Research on radiation intensity of nanosecond pulse laser-induced soil plasma]. (United States)

    Chen, Jin-zhong; Song, Guang-ju; Sun, Jiang; Li, Xu; Wei, Yan-hong


    To improve the quality of laser-induced breakdown spectroscopy, nanosecond pulse laser generated by Nd : YAG laser was used to excite soil sample. The laser-induced plasma spectrum was observed using a grating spectrometer and a photoelectric detection system. The influence of laser output energy ranging from 100 to 500 mJ on the radiation intensity of plasma was studied. The results show that both the line intensity and signal-to-background ratio can be enhanced under the optimized condition that the laser energy is 200 mJ. The quality of spectrum was further improved after the laser beam used to excite the sample was defocused properly. When the defocusing position is + 6 mm, the spectral lines intensity of element Mg, Al, K and Fe increased about 46%, 63%, 59% and 45% compared to that without defocusing respectively. The spectral signal-to-background ratio increased about 11%, 31%, 35% and 38% respectively. This lays a foundation for detection of trace impurity element in soil.

  19. Exploring the effect of laser excitation wavelength on signal recovery with deep tissue transmission Raman spectroscopy. (United States)

    Ghita, Adrian; Matousek, Pavel; Stone, Nicholas


    The aim of this research was to find the optimal Raman excitation wavelength to attain the largest possible sensitivity in deep Raman spectroscopy of breast tissue. This involved careful consideration of factors such as tissue absorption, scattering, fluorescence and instrument response function. The study examined the tissue absorption profile combined with Raman scattering and detection sensitivity at seven different, laser excitation wavelengths in the near infrared region of the spectrum. Several key scenarios in regards to the sample position within the tissue were examined. The highest Raman band visibility over the background ratio in respect to biological tissue provides the necessary information for determining the optimum laser excitation wavelength for deep tissue analysis using transmission Raman spectroscopy, including detection of breast calcifications. For thick tissues with a mix of protein and fat, such as breast tissue, 790-810 nm is concluded to be the optimum excitation wavelength for deep Raman measurements.

  20. Ultrashort laser modification of transparent materials: synergy of excitation/relaxation kinetics, thermodynamics and mechanics


    Bulgakova, N.M.; Zhukov, V.P.; Meshcheryakov, Y.P.; Kazansky, P.G.


    Ultrafast laser modification of transparent materials is an important technique enabling production of 3D photonic structures whose practical applications are rapidly widening. The physics behind laser-induced modifications is extremely rich and involves a variety of consecutive processes initiated by radiation absorption during the laser pulse and extending to millisecond timescales when the final structure becomes "frozen" in the material matrix. The quality of the final structures depends ...

  1. Interaction of CO2 laser radiation with dense plasma


    Abdel-Raoof, Wasfi Sharkawy


    The instabilities which occur in the interaction of CO2 laser radiation with a dense plasma have been studied. A TEA CO2 laser provided pulses of up to 30 joules of energy with a duration of 50 nanoseconds. By focussing the radiation on to a plane target a focal spot of about 180 micrometers diameter was formed with a irradiance of 10 to 10 W cm. The scattered radiation was collected by a laser focussing lens and analysed with a grating spectrometer. Linear relationships have been found betwe...

  2. Coherent and Incoherent Structural Dynamics in Laser-Excited Antimony

    CERN Document Server

    Waldecker, Lutz; Bertoni, Roman; Vasileiadis, Thomas; Garcia, Martin E; Zijlstra, Eeuwe S; Ernstorfer, Ralph


    We investigate the excitation of phonons in photoexcited antimony and demonstrate that the entire electron-lattice interactions, in particular coherent and incoherent electron-phonon coupling, can be probed simultaneously. Using femtosecond electron diffraction (FED) with high temporal resolution, we observe the coherent excitation of the fully symmetric \\Ag\\ optical phonon mode via the shift of the minimum of the atomic potential energy surface. Molecular dynamics simulations are performed to quantify the change in lattice potential and the associated real-space amplitude of the coherent atomic oscillations. In addition, our experimental configuration allows observing the energy transfer from electrons to phonons via incoherent electron-lattice scattering events. Applying a modified two-temperature model, the electron-phonon coupling is determined from the data as a function of electronic temperature.

  3. Pulsed laser excitation of phosphate stabilised silver nanoparticles

    Indian Academy of Sciences (India)

    Laser flash photolysis studies were carried out on two types of silver nanoparticles prepared by -radiolysis of Ag+ solutions in the presence of polyphosphate as the stabiliser. Type I silver nanoparticles displayed a surface plasmon band at 390 nm. Type II silver nanoparticles showed a 390 nm surface plasmon band with a ...

  4. Frontiers in propulsion research: Laser, matter-antimatter, excited helium, energy exchange thermonuclear fusion (United States)

    Papailiou, D. D. (Editor)


    Concepts are described that presently appear to have the potential for propulsion applications in the post-1990 era of space technology. The studies are still in progress, and only the current status of investigation is presented. The topics for possible propulsion application are lasers, nuclear fusion, matter-antimatter annihilation, electronically excited helium, energy exchange through the interaction of various fields, laser propagation, and thermonuclear fusion technology.

  5. Selective excitation of laser modes in an organic photonic dot microcavity (United States)

    Langner, M.; Sudzius, M.; Fröb, H.; Lyssenko, V. G.; Leo, K.


    We experimentally investigate variable laser mode excitation in an organic photonic dot microcavity by shifting the excitation beam position. The sample comprises two highly reflective dielectric mirrors (R >99.9%) and a square-shaped organic dye mesa of a DCM doped (2 wt %) Alq3-matrix. Its wavelength-size (≈5×5 μm2) transforms the cavity mode dispersion to a set of discrete states, each with a different intensity distribution of the electromagnetic field in space. Numerical simulations, including absorption and gain, confirm the experimentally observed relation between mode distribution and progression on the excitation condition.

  6. Controlling the Radiation Parameters of a Resonant Medium Excited by a Sequence of Ultrashort Superluminal Pulses (United States)

    Arkhipov, R. M.; Arkhipov, M. V.; Belov, P. A.; Babushkin, I.; Tolmachev, Yu. A.


    We investigate the possibility of controlling the radiation parameters of a spatially periodic one-dimensional medium consisting of classical harmonic oscillators by means of a sequence of ultrashort pulses that propagate through the medium with a superluminal velocity. We show that, in the spectrum of the transient process, in addition to the radiation at a resonant frequency of oscillators, new frequencies arise that depend on the period of the spatial distribution of the oscillator density, the excitation velocity, and the angle of observation. We have examined in detail the case of excitation of the medium by a periodic sequence of ultrashort pulses that travel with a superluminal velocity. We show that it is possible to excite oscillations of complex shapes and to control the radiation parameters of the resonant medium by changing the relationship between the pulse repetition rate, the medium resonant frequency, and the new frequency.

  7. Collision of counterpropagating laser-excited wake bubbles (United States)

    Deng, Z. G.; Yang, L.; Zhou, C. T.; Yu, M. Y.; Ying, H. P.; Wang, X. G.


    The collision of wake bubbles behind two counterpropagating laser pulses in rarefied plasma is investigated using particle-in-cell simulation. Special attention is paid to the highly nonlinear dynamics of the electrons in the interaction region. It is found that, as the two bubbles approach each other and collide, the electrons in the interaction region first oscillate in a periodic fashion, forming a quasistationary dense electron density ripple with fairly regular spatial structure. At longer times, the electron motion becomes chaotic, and the density grating is gradually smeared. The electrons escape in the transverse direction, and eventually the two bubbles merge to form a single one. The transition of the electron motion from regular to chaotic is confirmed by analytical modeling using test electrons moving in counterpropagating planar electromagnetic waves. The findings shed light on the dynamics of wake-bubble collisions and the complex behavior induced by multiple laser pulses in plasmas.

  8. Transient radiation from a ring resonant medium excited by an ultrashort superluminal pulse (United States)

    Arkhipov, R. M.; Arkhipov, M. V.; Babushkin, I. V.; Tolmachev, Yu A.


    We report some specific features of transient radiation from a periodic spatially modulated one-dimensional medium with a resonant response upon excitation by an ultrashort pulse. The case of ring geometry (with particle density distributed along the ring according to the harmonic law) is considered. It is shown that the spectrum of scattered radiation contains (under both linear and nonlinear interaction), along with the frequency of intrinsic resonance of the medium, a new frequency, which depends on the pulse velocity and the spatial modulation period. The case of superluminal motion of excitation, when the Cherenkov effect manifests itself, is also analysed.

  9. A 5 Gb/s Radiation Tolerant Laser Driver

    CERN Document Server

    Amaral, L; Da Silva, S; Mazza, G; Meroli, S; Moreira, P; Rivetti, A; Troska, J; Wyllie, K


    A laser driver for data transmission at 5 Gb/s has been developed as a part of the Giga Bit Transceiver (GBT) project. The Giga Bit Laser Driver (GBLD) targets High Energy Physics (HEP) applications for which radiation tolerance is mandatory. The GBLD ASIC can drive both VCSELs and some types of edge emitting lasers. It is essentially composed of two drivers capable of sinking up to 12 mA each from the load at a maximum data rate of 5 Gb/s, and of a current sink for the laser bias current. The laser driver include also pre-emphasis and duty cycle control capabilities.

  10. A new mode to excite a gas-discharge XeCL laser

    NARCIS (Netherlands)

    Timmermans, J.C.M.; van Goor, F.A.; Witteman, W.J.


    The charge mode is a new mode to excite a discharge XeCl laser based on the dynamics of a spiker-sustainer circuit with a magnetic pulse compressor. The breakdown voltage is higher than in any other mode, due to a very fast rise time. The higher breakdown voltage provides a wider discharge and we

  11. Laser-induced photochemical gas-phase reactions of vibrationally excited triplet molecules (United States)

    Zalesskaya, G. A.; Yakovlev, D. L.; Sambor, E. G.


    Mechanisms and rates of laser-induced gas-phase reactions of vibrationally excited triplet ketones were studied after adding electron and hydrogen donors using time-resolved delayed fluorescence. The influence of various bimolecular competing processes on DF quenching was analyzed.

  12. Excitation of monochromatic and stable electron acoustic wave by two counter-propagating laser beams (United States)

    Xiao, C. Z.; Liu, Z. J.; Zheng, C. Y.; He, X. T.


    The undamped electron acoustic wave is a newly-observed nonlinear electrostatic plasma wave and has potential applications in ion acceleration, laser amplification and diagnostics due to its unique frequency range. We propose to make the first attempt to excite a monochromatic and stable electron acoustic wave (EAW) by two counter-propagating laser beams. The matching conditions relevant to laser frequencies, plasma density, and electron thermal velocity are derived and the harmonic effects of the EAW are excluded. Single-beam instabilities, including stimulated Raman scattering and stimulated Brillouin scattering, on the excitation process are quantified by an interaction quantity, η =γ {τ }B, where γ is the growth rate of each instability and {τ }B is the characteristic time of the undamped EAW. The smaller the interaction quantity, the more successfully the monochromatic and stable EAW can be excited. Using one-dimensional Vlasov-Maxwell simulations, we excite EAW wave trains which are amplitude tunable, have a duration of thousands of laser periods, and are monochromatic and stable, by carefully controlling the parameters under the above conditions.

  13. Impact of laser excitation intensity on deep UV fluorescence detection in microchip electrophoresis. (United States)

    Schulze, Philipp; Ludwig, Martin; Belder, Detlev


    A high intensity 266 nm continuous wave (cw-) laser developed for material processing was utilised as an excitation source for sensitive native fluorescence detection of unlabelled compounds in MCE. This 120 mW laser was attached via an optical fibre into a commercial epifluorescence microscope. With this MCE set-up we evaluated the impact of laser power on the S/N of aromatic compounds as well as of proteins. Compared with a previous work which used a 4 mW pulsed laser for excitation, improved S/N for small aromatics and to a lesser extent for proteins could be attained. The LOD of the system was determined down to 24 ng/mL for serotonin (113 nM), 24 ng/mL for propranolol (81 nM), 80 ng/mL for tryptophan (392 nM) and 80 ng/mL for an aromatic diol (475 nM). Sensitive protein detection was obtained at concentrations of 5 microg/mL for lysocyme, trypsinogen and chymotrypsinogen (340, 208 and 195 nM, respectively). Finally, a comparison of the cw- with a pulsed 266 nm laser, operating at the same average power, showed a higher attainable sensitivity of the cw-laser. This can be attributed to fluorescence saturation and photobleaching effects of the pulsed laser at high pulse energies.

  14. Observation of non-radiative de-excitation processes in silicon nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Milgram, J.N.; Wojcik, J.; Mascher, P. [Department of Engineering Physics, Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario (Canada); Crowe, I.; Sherliker, B.; Halsall, M.P. [School of Electrical and Electronic Engineering, University of Manchester (United Kingdom); Gwilliam, R.M. [Surrey Ion Beam Centre, Advanced Technology Institute, University of Surrey, Guildford (United Kingdom); Knights, A.P.


    We describe the impact of non-radiative de-excitation mechanisms on the optical emission from silicon nanocrystals formed in SiO{sub 2}. Auger excitation via free carriers deliberately introduced through phosphorus ion implantation, shows a monotonic increase with increasing phosphorus concentration which can be modelled adequately using a simple statistical approach. We also report a reduction in nanocrystal luminescence intensity with increasing exposure to UV radiation and suggest this phenomenon results from the introduction of non-radiative defects in the Si/SiO{sub 2} network. The effect of UV radiation varies significantly depending on the sample preparation. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Photo-ionization and photo-excitation of curcumin investigated by laser flash photolysis (United States)

    Qian, Tingting; Kun, Li; Gao, Bo; Zhu, Rongrong; Wu, Xianzheng; Wang, ShiLong


    Curcumin (Cur) has putative antitumor properties. In the current study, we examined photophysical and photochemical properties of Cur using laser flash photolysis. The results demonstrated that Cur could be photo-ionized at 355 nm laser pulse to produce radical cation (Currad +) and solvated electron esol- in 7:3 ethanol-water mixtures. The quantum yield of Cur photo-ionization and the ratio of photo-ionization to photo-excitation were also determined. Currad + could be transferred into neutral radical of Cur (Currad ) via deprotonation with the pKa 4.13. The excited singlet of Cur (1Cur*) could be transferred into excited triplet (3Cur*), which could be quenched by oxygen to produce singlet oxygen 1O2∗. Reaction of 3Cur* with tryptophan was confirmed. The results encourage developing curcumin as a photosensitive antitumor agent.

  16. Coherent Cherenkov radiation and laser oscillation in a photonic crystal

    CERN Document Server

    Denis, T; Lee, J H H; van der Meer, R; Strooisma, A; van der Slot, P J M; Vos, W L; Boller, K J


    We demonstrate that photonic crystals can be used to generate powerful and highly coherent laser radiation when injecting a beam of free electrons. Using theoretical investigations we present the startup dynamics and coherence properties of such laser, in which gain is provided by matching the optical phase velocity in the photonic crystal to the velocity of the electron beam.

  17. Studies of new media radiation induced laser (United States)

    Han, K. S.; Shiu, Y. J.; Raju, S. R.; Hwang, I. H.; Tabibi, B.


    Various lasants were investigated especially, 2-iodohepafluoropropane (i-C3F7I) for the direct solar pumped lasers. Optical pumping of iodine laser was achieved using a small flashlamp. Using i-C3F7I as a laser gain medium, threshold inversion density, small signal gain, and laser performance at the elevated temperature were measured. The experimental results and analysis are presented. The iodine laser kinetics of the C3F7I and IBr system were numerically simulated. The concept of a direct solar-pumped laser amplifier using (i-C3F7I) as the laser material was evaluated and several kinetic coefficients for i-C3F7I laser system were reexamined. The results are discussed.

  18. A 490 W transversely excited atmospheric CO2 spark gap laser with added H2 (United States)

    Zand, M.; Koushki, A. M.; Neshati, R.; Kia, B.; Khorasani, K.


    In this paper we present a new design for a high pulse repetition rate transversely excited atmospheric CO2 laser with ultraviolet pre-ionization. A new method of fast thyristor capacitor charging and discharging by a spark gap is used. The effect of H2 gas addition on the output and stability of a transversely excited atmospheric laser operating with a basic mixture of CO2, N2 and He is investigated. The output power was increased by adding H2 to the gas mixture ratio of CO2:N2:He:H2  =  1:1:8:0.5 at total pressure of 850 mbar. An average power of 490 W at 110 Hz with 4.5 J per pulse was obtained. The laser efficiency was 11.2% and oxygen gas was used in the spark gap for electron capture to reduce the recovery time and increase the repetition rate.

  19. Laser interferometry of radiation driven gas jets (United States)

    Swanson, Kyle James; Ivanov, Vladimir; Mancini, Roberto; Mayes, Daniel C.


    In a series of experiments performed at the 1MA Zebra pulsed power accelerator of the Nevada Terawatt Facility nitrogen gas jets were driven with the broadband x-ray flux produced during the collapse of a wire-array z-pinch implosion. The wire arrays were comprised of 4 and 8, 10μm-thick gold wires and 17μm-thick nickel wires, 2cm and 3cm tall, and 0.3cm in diameter. They radiated 12kJ to 16kJ of x-ray energy, most of it in soft x-ray photons of less than 1keV of energy, in a time interval of 30ns. This x-ray flux was used to drive a nitrogen gas jet located at 0.8cm from the axis of the z-pinch radiation source and produced with a supersonic nozzle. The x-ray flux ionizes the nitrogen gas thus turning it into a photoionized plasma. We used laser interferometry to probe the ionization of the plasma. To this end, a Mach-Zehnder interferometer at the wavelength of 266 nm was set up to extract the atom number density profile of the gas jet just before the Zebra shot, and air-wedge interferometers at 266 and 532 nm were used to determine the electron number density of the plasma right during the Zebra shot. The ratio of electron to atom number densities gives the distribution of average ionization state of the plasma. A python code was developed to perform the image data processing, extract phase shift spatial maps, and obtain the atom and electron number densities via Abel inversion. Preliminary results from the experiment are promising and do show that a plasma has been created in the gas jet driven by the x-ray flux, thus demonstrating the feasibility of a new experimental platform to study photoionized plasmas in the laboratory. These plasmas are found in astrophysical scenarios including x-ray binaries, active galactic nuclei, and the accretion disks surrounding black holes1. This work was sponsored in part by DOE Office of Science Grant DE-SC0014451.1R. C. Mancini et al, Phys. Plasmas 16, 041001 (2009)


    Directory of Open Access Journals (Sweden)

    Pavel Yu. Rogov


    Full Text Available The features of human skin response to the impact of femtosecond laser radiation were researched. The Monte–Carlo method was used for estimation of the radiation penetration depth into the skin cover. We used prevalent wavelength equal to 800 nm (for Ti: sapphire laser femtosecond systems. A mathematical model of heat transfer process was introduced based on the analytical solution of the system of equations describing the dynamics of the electron and phonon subsystems. An experiment was carried out to determine the threshold energy of biological tissue injury (chicken skin was used as a test object. The value of electronic subsystem relaxation time was determined from the experiment and is in keeping with literature data. The results of this work can be used to assess the maximum permissible exposure of laser radiation of different lengths that cause the damage of biological tissues, as well as for the formation of safe operation standards for femtosecond laser systems.

  1. Radiative shocks in gas on the Omega laser (United States)

    Reighard, A.; Drake, R. P.; Keiter, P.; Korreck, K. E.; Perry, T. S.; Robey, H. A.; Remington, B. A.; Wallace, R. J.; Ryutov, D. D.; Knauer, J.; Calder, A.; Rosner, R.; Fryxell, B.; Arnett, D.; Turner, N.; Stone, J.; Koenig, M.; Bouquet, Serge


    A number of astrophysical systems involve radiative shocks that collapse spatially in response to the energy lost through radiation. This is believed to produce thin, dense, unstable shells. We have begun experiments on the Omega laser intended to produce such collapsing shocks and to study their evolution. The experiments use the laser to accelerate a thin slab of Be, which becomes a piston that drives a shock through 1.1 atm of Ar gas at 100 km/s. The shock is predicted to collapse. Experiments are in preparation that will detect the dense layer and also the radiative precursor in front of the shock. We will report their results.

  2. In-situ microscopy of front and rear side ablation processes in alkali aluminosilicate glass using ultra short pulsed laser radiation


    Großmann, D.; Reininghaus, M.; Kalupka, C.; Jenne, M.; Kumkar, M.


    The visualization of the nonlinear absorption, the subsequent relaxation of excited states and the formation of defects enables the investigation of fundamental laser-material-interaction as well as the identification of process windows for micromachining of transparent materials with ultra short pulsed laser radiation. In this work, time resolved pump probe microscopy is applied to analyze the laser-material-interaction and to reduce damage inside the material during front- and rear side abl...

  3. Volumetric graphics in liquid using holographic femtosecond laser pulse excitations (United States)

    Kumagai, Kota; Hayasaki, Yoshio


    Much attention has been paid to the development of three-dimensional volumetric displays in the fields of optics and computer graphics, and it is a dream of we display researchers. However, full-color volumetric displays are challenging because many voxels with different colors have to be formed to render volumetric graphics in real three-dimensional space. Here, we show a new volumetric display in which microbubble voxels are three-dimensionally generated in a liquid by focused femtosecond laser pulses. Use of a high-viscosity liquid, which is the key idea of this system, slows down the movement of the microbubbles, and as a result, volumetric graphics can be displayed. This "volumetric bubble display" has a wide viewing angle and simple refresh and requires no addressing wires because it involves optical access to transparent liquid and achieves full-color graphics composed on light-scattering voxels controlled by illumination light sources. In addition, a bursting of bubble graphics system using an ultrasonic vibrator also has been demonstrated. This technology will open up a wide range of applications in three-dimensional displays, augmented reality and computer graphics.

  4. [Influence of microwave and laser radiation on survivability of organisms]. (United States)

    Ismailov, E Sh; Zakharov, S D; Aminova, E M; Ismailova, G E; Khachirov, D G


    Depending on energy, spatial-temporal, modulation and other characteristics of an electromagnetic field, properties of a subject, exposure settings and possible interaction of other attendant factors microwaves may have either stabilizing, wholesome and even therapeutic or negative (damaging) effects on biological and ecological objects and systems. Therefore, there are two interrelated problems to be addressed. One is electromagnetic safety of and health provisions for humans exposed to EMF and EMR and the other, effective utilization of microwave EMF and EMR for biomedical and other purposes associated with enhancement of viability of organisms. The light-oxygen effect of laser radiation is gaining footing in therapy where it is used to activate or destroy biological systems by optical radiation at a specified light dose. Thus, low-intensity laser radiation can be used to improve viability and high-intensity laser radiation, to treat cancers.

  5. Inertial cavitation in theranostic nanoemulsions with simultaneous pulsed laser and low frequency ultrasound excitation (United States)

    Arnal, Bastien; Wei, Chen-Wei; Xia, Jinjun; Pelivanov, Ivan M.; Lombardo, Michael; Perez, Camilo; Matula, Thomas J.; Pozzo, Danilo; O'Donnell, Matthew


    Ultrasound-induced inertial cavitation is a mechanical process used for site-localized therapies such as non-invasive surgery. Initiating cavitation in tissue requires very high intensity focused ultrasound (HIFU) and low-frequencies. Hence, some applications like thrombolysis require targeted contrast agents to reduce peak intensities and the potential for secondary effects. A new type of theranostic nanoemulsion has been developed as a combined ultrasound (US)/photoacoustic(PA) agent for molecular imaging and therapy. It includes a nanoscale emulsion core encapsulated with a layer of gold nanospheres at the water/ oil interface. Its optical absorption exhibits a spectrum broadened up to 1100 nm, opening the possibility that 1064 nm light can excite cavitation nuclei. If optically-excited nuclei are produced at the same time that a low-frequency US wave is at peak negative pressure, then highly localized therapies based on acoustic cavitation may be enabled at very low US pressures. We have demonstrated this concept using a low-cost, low energy, portable 1064 nm fiber laser in conjunction with a 1.24 MHz US transducer for simultaneous laser/US excitation of nanoemulsions. Active cavitation detection from backscattered signals indicated that cavitation can be initiated at very low acoustic pressures (less than 1 MPa) when laser excitation coincides with the rarefaction phase of the acoustic wave, and that no cavitation is produced when light is delivered during the compressive phase. US can sustain cavitation activity during long acoustic bursts and stimulate diffusion of the emulsion, thus increasing treatment speed. An in vitro clot model has been used to demonstrate combined US and laser excitation of the nanoemulsion for efficient thrombolysis.

  6. Coherent and tunable terahertz radiation from graphene surface plasmon polaritons excited by an electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shenggang, E-mail:; Hu, Min; Chen, Xiaoxing; Zhang, Ping; Gong, Sen; Zhao, Tao; Zhong, Renbin [Terahertz Research Centre, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Cooperative Innovation Centre of Terahertz Science, Chengdu, Sichuan 610054 (China); Zhang, Chao [Terahertz Research Centre, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Cooperative Innovation Centre of Terahertz Science, Chengdu, Sichuan 610054 (China); School of Physics and Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales 2522 (Australia)


    Although surface plasmon polaritons (SPPs) resonance in graphene can be tuned in the terahertz regime, transforming such SPPs into coherent terahertz radiation has not been achieved. Here, we propose a graphene-based coherent terahertz radiation source with greatly enhanced intensity. The radiation works at room temperature, it is tunable and can cover the whole terahertz regime. The radiation intensity generated with this method is 400 times stronger than that from SPPs at a conventional dielectric or semiconducting surface and is comparable to that from the most advanced photonics source such as a quantum cascade laser. The physical mechanism for this strong radiation is presented. The phase diagrams defining the parameters range for the occurrence of radiation is also shown.

  7. Spectromicroscopy of Polymers: Comparison of Radiation Damage with Electron and Photon Core Excitation Spectroscopy Techniques (United States)

    Ade, H.; Smith, A. P.; Rightor, E. G.; Hitchcock, A. P.; Urquhart, S.; Leapman, R.


    Core excitation microspectroscopy has become a powerful tool for the characterization of polymeric materials due to its sensitivity to chemical functionality. However, the excitations utilized in electron energy loss spectroscopy performed in a scanning transmission electron microscope (TEM-EELS) and near edge x-ray absorption fine structure (NEXAFS) spectroscopy can introduce radiation damage and chemically modify the sample. In order to understand the radiation damage associated with TEM-EELS and NEXAFS spectroscopy we have studied the radiation damage of the common polymer poly(ethylene terephthalate) (PET) as exhibited by changes in the acquired C K-edge excitation spectra. By fitting gaussian functions to the spectral intensity changes as a function of dose, we have determined the critical radiation dose of PET for both NEXAFS spectroscopy and TEM-EELS under typical operating conditions. This critical radiation dose for TEM-EELS is found to be 1.7 ± 0.2 x 10^8 grey (1.7 ± 0.2 x 10^4 Mrad) compared to a critical radiation dose for NEXAFS spectroscopy of 1.4 ± 0.7 x 10^9 grey (1.4 ± 0.7 x 10^5 Mrad). By considering the G factors of the two techniques and the critical radiation dose, a rule of thumb was derived that indicates that with typical present operating conditions, NEXAFS spectroscopy can analyze areas 500 times smaller than TEM-EELS given the same amount of radiation damage. Work supported by: NSF Young Investigator Award (DMR-9458060) and Dow Chemical

  8. Radiation of a resonant medium excited by few-cycle optical pulses at superluminal velocity (United States)

    Arkhipov, R. M.; Pakhomov, A. V.; Arkhipov, M. V.; Babushkin, I.; Tolmachev, Yu A.; Rosanov, N. N.


    Recent progress in generation of optical pulses of durations comparable to one optical cycle has presented great opportunities for studies of the fundamental processes in matter as well as time-resolved spectroscopy of ultrafast processes in nonlinear media. It opened up a new area of research in modern ultrafast nonlinear optics and led to appearance of the attosecond science. In parallel, a new research area related to emission from resonant media excited by superluminally propagating ultrashort bursts of electromagnetic radiation has been actively developed over the last few years. In this paper, we review our recent results on theoretical analysis of the Cherenkov-type radiation of a resonant medium excited by few-cycle optical pulses propagating at superluminal velocity. This situation can be realized when an electromagnetic pulse with a plane wavefront incidents on a straight string of resonant atoms or a spot of light rotates at very large angular frequency and excites a distant circular string of resonant dipoles. Theoretical analysis revealed some unusual and remarkable features of the Cherenkov radiation generated in this case. This radiation arises in a transient regime which leads to the occurrence of new frequencies in the radiation spectrum. Analysis of the characteristics of this radiation can be used for the study of the resonant structure properties. In addition, a nonlinear resonant medium excited at superluminal velocity can emit unipolar optical pulses, which can be important in ultrafast control of wave-packet dynamics of matter. Specifics of the few-cycle pulse-driven optical response of a resonant medium composed of linear and nonlinear oscillators is discussed.

  9. Practical Method for engineering Erbium-doped fiber lasers from step-like pulse excitations

    Energy Technology Data Exchange (ETDEWEB)

    Causado-Buelvas, J D; Gomez-Cardona, N D; Torres, P, E-mail: [Escuela de fisica, Universidad Nacional de Colombia-sede Medellin A.A.3840, Medellin (Colombia)


    A simple method, known as 'easy points', has been applied to the characterization of Erbium-doped fibers, aiming for the engineering of fiber lasers. Using low- optical-power flattop pulse excitations it has been possible to determine both the attenuation coefficients and the intrinsic saturation powers of doped single-mode fibers at 980 and 1550 nm. Laser systems have been projected for which the optimal fiber length and output power have been determined as a function of the input power. Ring and linear laser cavities have been set up, and the characteristics of the output laser have been obtained and compared with the theoretical predictions based on the 'easy points' parameters.

  10. Pulse shaping of transversely excited atmospheric CO2 laser using a simple plasma shutter (United States)

    Hurst, Noah; Harilal, S. S.


    The pulse from a transversely excited atmospheric CO2 laser consists of a sharp spike followed by a long, drawn out tail region spanning about 2-5 μs caused by the nitrogen gas in the laser cavity. The nitrogen tail is undesirable in many applications because it decreases the average power of the laser pulse. We employ a pinhole plasma shutter for eliminating the nitrogen tail and shortening the pulse width. The pinhole shutter optically triggers plasma at a certain point in time with respect to the temporal profile of the laser pulse. This way, a good portion of the sharp spike is transmitted, while the energy stored in the nitrogen tail is consumed in heating the plasma. This simplistic plasma shutter is easy to build and inexpensive compared to other existing plasma shutter designs.

  11. Laser cooling and optical detection of excitations in a LC electrical circuit

    DEFF Research Database (Denmark)

    Taylor, J. M.; Sørensen, Anders Søndberg; Marcus, Charles Masamed


    We explore a method for laser cooling and optical detection of excitations in a room temperature LC electrical circuit. Our approach uses a nanomechanical oscillator as a transducer between optical and electronic excitations. An experimentally feasible system with the oscillator capacitively...... coupled to the LC and at the same time interacting with light via an optomechanical force is shown to provide strong electromechanical coupling. Conditions for improved sensitivity and quantum limited readout of electrical signals with such an “optical loud speaker” are outlined....

  12. High-fidelity modelling of an exciplex pumped alkali laser with radiative transport

    Energy Technology Data Exchange (ETDEWEB)

    Palla, Andrew D; Carroll, David L; Verdeyen, Joseph T [CU Aerospace, Champaign, IL 61820 (United States); Heaven, Michael C, E-mail: [Department of Chemistry, Emory University, Atlanta, GA 30322 (United States)


    The exciplex-pumped alkali laser (XPAL) system has been demonstrated in mixtures of Cs vapour, Ar, and ethane by pumping Cs-Ar atomic collision pairs and subsequent dissociation of diatomic, electronically excited CsAr molecules (exciplexes or excimers). Because of the addition of atomic collision pairs and exciplex states, modelling of the XPAL system is far more complicated than the modelling of the classic diode-pumped alkali laser (DPAL). In this paper, we discuss BLAZE-V time-dependent multi-dimensional modelling of this new laser system including radiative transport and parasitic loss effects. A two-dimensional, time-dependent baseline simulation of a pulsed XPAL is presented and compared to data. Good agreement is achieved on a laser pulse full width at half-maximum and laser pulse rise time. Parametric simulations of pulsed XPAL system configurations similar to that of the baseline case, given both four- and five-level laser operation, are presented in which good agreement is obtained with outcoupled laser energy as a function of absorbed pump energy data. The potential impact of parasitic losses on modelled system configurations is discussed.

  13. White light emission from Er2O3 nano-powder excited by infrared radiation (United States)

    Tabanli, Sevcan; Eryurek, Gonul; Di Bartolo, Baldassare


    Phosphors of Er2O3 nano-crystalline powders were synthesized by the thermal decomposition method. The structural properties of the nano-powders were investigated with XRD and HRTEM measurements. The cubic phase with a = 10.540 Å was the only phase observed. The average crystalline sizes and the widths of the grain size distribution curves were determined to be 27.2, 18.7 and 9.7 nm, respectively. The spectroscopic properties of the Er2O3 nano-powder were studied by measuring the luminescence, decay and rise patterns under 808 and 975 nm diode laser excitations. A peculiar effect of the pressure was observed since an optically active ion (Er) is part of the complex and not a dopant. A broad band of the white light emission combined with blue, green and red up-conversion emission bands of Er3+ ions were observed at 0.03 mbar pressure under both excitation wavelengths. Only, an intense broad band white light emission was observed from these nanocrystals at atmospheric pressure. Rising patterns show that the white light intensity reaches its maximum value more rapidly under 975 nm excitation although it decays slower than that of 808 nm excitation. The color quality parameters such as the color coordinate (CRI), correlated color temperature and the color rendering index were found to vary with both the excitation wavelength and the ambient pressure indicating that these nanocrystals could be considered good white light emitting source under the infrared excitations.

  14. Rotationally resolved IR-diode laser studies of ground-state CO2 excited by collisions with vibrationally excited pyridine. (United States)

    Johnson, Jeremy A; Kim, Kilyoung; Mayhew, Maurine; Mitchell, Deborah G; Sevy, Eric T


    Relaxation of highly vibrationally excited pyridine (C5NH5) by collisions with carbon dioxide has been investigated using diode laser transient absorption spectroscopy. Vibrationally hot pyridine (E' = 40,660 cm(-1)) was prepared by 248 nm excimer laser excitation followed by rapid radiationless relaxation to the ground electronic state. Pyridine then collides with CO2, populating the high rotational CO2 states with large amounts of translational energy. The CO2 nascent rotational population distribution of the high-J (J = 58-80) tail of the 00(0)0 state was probed at short times following the excimer laser pulse to measure rate constants and probabilities for collisions populating these CO2 rotational states. Doppler spectroscopy was used to measure the CO2 recoil velocity distribution for J = 58-80 of the 00(0)0 state. The energy-transfer distribution function, P(E,E'), from E' - E approximately 1300-7000 cm(-1) was obtained by re-sorting the state-indexed energy-transfer probabilities as a function of DeltaE. P(E,E') is fit to an exponential or biexponential function to determine the average energy transferred in a single collision between pyridine and CO2. Also obtained are fit parameters that can be compared to previously studied systems (pyrazine, C6F6, methylpyrazine, and pyrimidine/CO2). Although the rotational and translational temperatures that describe pyridine/CO2 energy transfer are similar to previous systems, the energy-transfer probabilities are much smaller. P(E,E') fit parameters for pyridine/CO2 and the four previously studied systems are compared to various donor molecular properties. Finally, P(E,E') is analyzed in the context of two models, one indicating that P(E,E') shape is primarily determined by the low-frequency out-of-plane donor vibrational modes, and the other that indicates that P(E,E') shape can be determined from how the donor molecule final density of states changes with DeltaE.

  15. Counterpropagating Radiative Shock Experiments on the Orion Laser (United States)

    Suzuki-Vidal, F.; Clayson, T.; Stehlé, C.; Swadling, G. F.; Foster, J. M.; Skidmore, J.; Graham, P.; Burdiak, G. C.; Lebedev, S. V.; Chaulagain, U.; Singh, R. L.; Gumbrell, E. T.; Patankar, S.; Spindloe, C.; Larour, J.; Kozlova, M.; Rodriguez, R.; Gil, J. M.; Espinosa, G.; Velarde, P.; Danson, C.


    We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measured via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.

  16. Counterpropagating Radiative Shock Experiments on the Orion Laser. (United States)

    Suzuki-Vidal, F; Clayson, T; Stehlé, C; Swadling, G F; Foster, J M; Skidmore, J; Graham, P; Burdiak, G C; Lebedev, S V; Chaulagain, U; Singh, R L; Gumbrell, E T; Patankar, S; Spindloe, C; Larour, J; Kozlova, M; Rodriguez, R; Gil, J M; Espinosa, G; Velarde, P; Danson, C


    We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measured via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.

  17. A low-cost photoacoustic microscopy system with a laser diode excitation (United States)

    Wang, Tianheng; Nandy, Sreyankar; Salehi, Hassan S.; Kumavor, Patrick D.; Zhu, Quing


    Photoacoustic microscopy (PAM) is capable of mapping microvasculature networks in biological tissue and has demonstrated great potential for biomedical applications. However, the clinical application of the PAM system is limited due to the use of bulky and expensive pulsed laser sources. In this paper, a low-cost optical-resolution PAM system with a pulsed laser diode excitation has been introduced. The lateral resolution of this PAM system was estimated to be 7 µm by imaging a carbon fiber. The phantoms made of polyethylene tubes filled with blood and a mouse ear were imaged to demonstrate the feasibility of this PAM system for imaging biological tissues. PMID:25401019

  18. UV Raman spectroscopy of H2-air flames excited with a narrowband KrF laser (United States)

    Shirley, John A.


    Raman spectra of H2 and H2O in flames excited by a narrowband KrF excimer laser are reported. Observations are made over a porous-plug, flat-flame burner reacting H2 in air, fuel-rich with nitrogen dilution to control the temperature, and with an H2 diffusion flame. Measurements made from UV Raman spectra show good agreement with measurements made by other means, both for gas temperature and relative major species concentrations. Laser-induced fluorescence interferences arising from OH and O2 are observed in emission near the Raman spectra. These interferences do not preclude Raman measurements, however.

  19. Surface treatment of CFRP composites using femtosecond laser radiation (United States)

    Oliveira, V.; Sharma, S. P.; de Moura, M. F. S. F.; Moreira, R. D. F.; Vilar, R.


    In the present work, we investigate the surface treatment of carbon fiber-reinforced polymer (CFRP) composites by laser ablation with femtosecond laser radiation. For this purpose, unidirectional carbon fiber-reinforced epoxy matrix composites were treated with femtosecond laser pulses of 1024 nm wavelength and 550 fs duration. Laser tracks were inscribed on the material surface using pulse energies and scanning speeds in the range 0.1-0.5 mJ and 0.1-5 mm/s, respectively. The morphology of the laser treated surfaces was investigated by field emission scanning electron microscopy. We show that, by using the appropriate processing parameters, a selective removal of the epoxy resin can be achieved, leaving the carbon fibers exposed. In addition, sub-micron laser induced periodic surface structures (LIPSS) are created on the carbon fibers surface, which may be potentially beneficial for the improvement of the fiber to matrix adhesion in adhesive bonds between CFRP parts.

  20. Recollision induced excitation-ionization with counter-rotating two-color circularly polarized laser field (United States)

    Ben, Shuai; Guo, Pei-Ying; Pan, Xue-Fei; Xu, Tong-Tong; Song, Kai-Li; Liu, Xue-Shen


    Nonsequential double ionization of Ar by a counter-rotating two-color circularly polarized laser field is theoretically investigated. At the combined intensity in the "knee" structure range, the double ionization occurs mainly through recollision induced excitation followed by subsequent ionization of Ar+∗ . By tracing the history of the recollision trajectories, we explain how the relative intensity ratio of the two colors controls the correlated electron dynamics and optimizes the ionization yields. The major channels contributing to enhancing the double ionization are through the elliptical trajectories with smaller travel time but not through the triangle shape or the other long cycle trajectories. Furthermore, the correlated electron dynamics could be limited to the attosecond time scale by adjusting the relative intensity ratio. Finally, the double ionization from doubly excited complex at low laser intensity is qualitatively discussed.

  1. Femtosecond laser excitation of dielectric materials: experiments and modeling of optical properties and ablation depths

    DEFF Research Database (Denmark)

    Wædegaard, Kristian Juncher; Frislev, Martin Thomas; Balling, Peter


    Modeling of the interaction between a dielec- tric material and ultrashort laser pulses provides the tem- poral evolution of the electronic excitation and the optical properties of the dielectric. Experimentally determined re- flectances and ablation depths for sapphire are compared...... to the calculations. A decrease in reflectance at high fluences is observed experimentally, which demonstrates the neces- sity of a temperature-dependent electron scattering rate in the model. The comparison thus provides new constraints on the optical parameters of the model....

  2. Application of multi-step excitation schemes for detection of actinides and lanthanides in solutions by luminescence/chemiluminescence laser spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Izosimov, I. [Joint Institute for Nuclear Research, Joliot Curie 6, Dubna 141980 (Russian Federation)


    The use of laser radiation with tunable wavelength allows the selective excitation of actinide/lanthanide species with subsequent registration of luminescence/chemiluminescence for their detection. This work is devoted to applications of the time-resolved laser-induced luminescence spectroscopy and time-resolved laser-induced chemiluminescence spectroscopy for the detection of lanthanides and actinides. Results of the experiments on U, Eu, and Sm detection by TRLIF (Time Resolved Laser Induced Fluorescence) method in blood plasma and urine are presented. Data on luminol chemiluminescence in solutions containing Sm(III), U(IV), and Pu(IV) are analyzed. It is shown that appropriate selectivity of lanthanide/actinide detection can be reached when chemiluminescence is initiated by transitions within 4f- or 5f-electron shell of lanthanide/actinide ions corresponding to the visible spectral range. In this case chemiluminescence of chemiluminogen (luminol) arises when the ion of f element is excited by multi-quantum absorption of visible light. The multi-photon scheme of chemiluminescence excitation makes chemiluminescence not only a highly sensitive but also a highly selective tool for the detection of lanthanide/actinide species in solutions. (author)

  3. Development of laser ablation plasma by anisotropic self-radiation

    Directory of Open Access Journals (Sweden)

    Ohnishi Naofumi


    Full Text Available We have proposed a method for reproducing an accurate solution of low-density ablation plasma by properly treating anisotropic radiation. Monte-Carlo method is employed for estimating Eddington tensor with limited number of photon samples in each fluid time step. Radiation field from ablation plasma is significantly affected by the anisotropic Eddington tensor. Electron temperature around the ablation surface changes with the radiation field and is responsible for the observed emission. An accurate prediction of the light emission from the laser ablation plasma requires a careful estimation of the anisotropic radiation field.

  4. Simultaneous Multicolor Single-Molecule Tracking with Single-Laser Excitation via Spectral Imaging. (United States)

    Huang, Tao; Phelps, Carey; Wang, Jing; Lin, Li-Jung; Bittel, Amy; Scott, Zubenelgenubi; Jacques, Steven; Gibbs, Summer L; Gray, Joe W; Nan, Xiaolin


    Single-molecule tracking (SMT) offers rich information on the dynamics of underlying biological processes, but multicolor SMT has been challenging due to spectral cross talk and a need for multiple laser excitations. Here, we describe a single-molecule spectral imaging approach for live-cell tracking of multiple fluorescent species at once using a single-laser excitation. Fluorescence signals from all the molecules in the field of view are collected using a single objective and split between positional and spectral channels. Images of the same molecule in the two channels are then combined to determine both the location and the identity of the molecule. The single-objective configuration of our approach allows for flexible sample geometry and the use of a live-cell incubation chamber required for live-cell SMT. Despite a lower photon yield, we achieve excellent spatial (20-40 nm) and spectral (10-15 nm) resolutions comparable to those obtained with dual-objective, spectrally resolved Stochastic Optical Reconstruction Microscopy. Furthermore, motions of the fluorescent molecules did not cause loss of spectral resolution owing to the dual-channel spectral calibration. We demonstrate SMT in three (and potentially more) colors using spectrally proximal fluorophores and single-laser excitation, and show that trajectories of each species can be reliably extracted with minimal cross talk. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  5. Effect of plasma formation on the double pulse laser excitation of cubic silicon carbide (United States)

    Otobe, T.; Hayashi, T.; Nishikino, M.


    We calculate the electron excitation in cubic silicon carbide caused by the intense femtosecond laser double pulses using the time-dependent density functional theory (TDDFT). After the first pulse ends, excited electrons should be relaxed by collisional processes. Because TDDFT does not include scattering processes, thermalization is mimicked by following three assumptions. First, we assume no collisions and relaxation processes. Second, we assume the partially thermalized electronic state defined by two quasi-temperatures in the conduction and valence bands individually. Third, we assume the thermalized electron distribution, which is expressed by single electron temperature. Our results indicate that the plasma frequency (ωpl) formed by the first pulse is the key parameter in energy absorption in the second pulse. When the plasma frequency of the plasma formed by the first laser approaches the frequency of the laser, resonant excitation by the second pulse occurs. The lower electron temperature shows higher ωpl and higher efficient energy absorption because the effective mass of the electron becomes smaller.

  6. Laser scattering method in studies of the turbulence excited by a relativistic electron beam in plasma

    Energy Technology Data Exchange (ETDEWEB)

    Vyacheslavov, L.N.; Kandaurov, I.V.; Kruglyakov, E.P.; Losev, M.V.; Meshkov, O.I.; Sanin, A.L.


    Scattering radiation from a CO{sub 2} laser is used to carry out direct observations of Langmuir oscillations associated with the interaction between a high-power relativistic electron beam and a plasma. Experimental data on the frequency spectrum of the turbulence and the first results on studies of the spatial spectra of the oscillations are presented. 4 refs., 2 figs.

  7. Electromagnetic induction and radiation-induced abnormality of wave propagation in excitable media (United States)

    Ma, Jun; Wu, Fuqiang; Hayat, Tasawar; Zhou, Ping; Tang, Jun


    Continuous wave emitting from sinus node of the heart plays an important role in wave propagating among cardiac tissue, while the heart beating can be terminated when the target wave is broken into turbulent states by electromagnetic radiation. In this investigation, local periodical forcing is applied on the media to induce continuous target wave in the improved cardiac model, which the effect of electromagnetic induction is considered by using magnetic flux, then external electromagnetic radiation is imposed on the media. It is found that target wave propagation can be blocked to stand in a local area and the excitability of media is suppressed to approach quiescent but homogeneous state when electromagnetic radiation is imposed on the media. The sampled time series for membrane potentials decrease to quiescent state due to the electromagnetic radiation. It could accounts for the mechanism of abnormality in heart failure exposed to continuous electromagnetic field.

  8. Direct printing of micro/nanostructures by femtosecond laser excitation of nanocrystals (United States)

    Shou, Wan; Pan, Heng


    Direct writing using single or multiple energized beams (e.g. laser, ion or electron beams) provides high feature resolution (materials consisting of additives and effective components. Due to the presence of additive (such as polymer and binders), the effective components are relatively low resulting in high threshold for device operation. In order to direct print functional devices at low cost, there has been extensive research on laser processing of pre-synthesized nanomaterials for non-polymer functional device manufacturing. Pre-synthesized nanocrystals can have better control in the stoichiometry and crystallinity. In addition, pre-synthesis process enjoys the flexibility in material choice since a variety of materials can be synthesized. Femtosecond laser assembly and deposition of nanomaterials can be a feasible 3D micro/nano additive manufacturing approach, although mechanisms leading to assembly and deposition have not been fully understood. In this paper, we propose a mechanism for 2D and 3D deposition of nanocrystals by laser excitation with moderate peak intensities(1011-1012 W/cm2). It is postulated that laser induced charging is responsible for the deposition. The scheme paves the way for laser selective electrophoretic deposition as a micro/nanoscale additive manufacturing approach.

  9. Laser excitation dynamics of argon metastables generated in atmospheric pressure flows by microwave frequency microplasma arrays (United States)

    Rawlins, W. T.; Galbally-Kinney, K. L.; Davis, S. J.; Hoskinson, A. R.; Hopwood, J. A.


    The optically pumped rare-gas metastable laser is a chemically inert analogue to diode-pumped alkali (DPAL) and alkali-exciplex (XPAL) laser systems. Scaling of these devices requires efficient generation of electronically excited metastable atoms in a continuous-wave electric discharge in flowing gas mixtures at atmospheric pressure. This paper describes initial investigations of the use of linear microwave micro-discharge arrays to generate metastable rare-gas atoms at atmospheric pressure in optical pump-and-probe experiments for laser development. Power requirements to ignite and sustain the plasma at 1 atm are low, 2p9 transition at 811.5 nm and the corresponding laser-induced fluorescence on the 2p10-->1s5 transition at 912.3 nm; the 2p10 state is efficiently populated by collisional energy transfer from 2p9. Using tunable diode laser absorption/gain spectroscopy, we observe small-signal gains of ~1 cm-1 over a 1.9 cm path. We also observe stable, continuous-wave laser oscillation at 912.3 nm, with preliminary optical efficiency ~55%. These results are consistent with efficient collisional coupling within the Ar(4s) manifold.

  10. Interaction of laser radiation with metal island films (United States)

    Benditskii, A. A.; Viduta, L. V.; Ostranitsa, A. P.; Tomchuk, P. M.; Iakovlev, V. A.


    The emission phenomena arising during the interaction of pulsed laser emission with island films are examined with reference to experimental results obtained for island films of gold irradiated by a CO2 laser at a wavelength of 10.6 microns. Well reproducible emission pulses that are also accompanied by light pulses are produced at intensities less than 10 to the 5th W/sq cm, with the film structure remaining unchanged. The maximum energy of the electrons emitted under the effect of laser radiation is estimated at 3 eV; the work function is 2.1 eV.

  11. Excitations

    Energy Technology Data Exchange (ETDEWEB)

    Dorner, B. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)


    A short introduction to instrumental resolution is followed by a discussion of visibilities of phonon modes due to their eigenvectors. High precision phonon dispersion curves in GaAs are presented together with `ab initio` calculations. Al{sub 2}O{sub 3} is taken as an example of selected visibility due to group theory. By careful determination of phonon intensities eigenvectors can be determined, such as in Silicon and Diamond. The investigation of magnon modes is shown for the garnet Fe{sub 2}Ca{sub 3}(GeO{sub 4}){sub 3}, where also a quantum gap due to zero point spin fluctuations was observed. The study of the splitting of excitons in CsFeCl{sub 3} in an applied magnetic field demonstrates the possibilities of neutron polarisation analysis, which made it possible to observe a mode crossing. An outlook to inelastic X-ray scattering with very high energy resolution of synchrotron radiation is given with the examples of phonons in Beryllium and in water. (author) 19 figs., 36 refs.

  12. Base-Level Management of Laser Radiation Protection Program (United States)


    gallium-aluminum-arsenide (GaAlAs), or alexandrite. Liquid materials that are used as active mediums include: rhodamine dye and coumarin . Section D...a source of radiation and the dye emits radiation at a longer wavelength. Coumarin dyes are useful as active media for emissions inthe blue to green...plastic, or quartz. Optical fibers have found uses in many areas including: industrial laser welding; medical surgery; dental work; product-code

  13. Electromagnetic diffraction radiation of a subwavelength-hole array excited by an electron beam. (United States)

    Liu, Shenggang; Hu, Min; Zhang, Yaxin; Li, Yuebao; Zhong, Renbin


    This paper explores the physics of the electromagnetic diffraction radiation of a subwavelength holes array excited by a set of evanescent waves generated by a line charge of electron beam moving parallel to the array. Activated by a uniformly moving line charge, numerous physical phenomena occur such as the diffraction radiation on both sides of the array as well as the electromagnetic penetration or transmission below or above the cut-off through the holes. As a result the subwavelength holes array becomes a radiation array. Making use of the integral equation with relevant Green's functions, an analytical theory for such a radiation system is built up. The results of the numerical calculations based on the theory agree well with that obtained by the computer simulation. The relation among the effective surface plasmon wave, the electromagnetic penetration or transmission of the holes and the diffraction radiation is revealed. The energy dependence of and the influence of the hole thickness on the diffraction radiation and the electromagnetic penetration or transmission are investigated in detail. Therefore, a distinct diffraction radiation phenomenon is discovered.

  14. Dependence of optoacoustic transients on exciting laser parameters for real-time monitoring of retinal photocoagulation (United States)

    Langejürgen, J.; Schlott, K.; Bever, M.; Hausmann, K.; Koinzer, S.; Ptaszynski, L.; Roider, J.; Birngruber, R.; Brinkmann, R.


    The extent of retinal laser coagulations depends on the temperature increase at the fundus and the time of irradiation. Due to light scattering within the eye and variable fundus pigmentation the induced temperature increase and therefore the extent of the coagulations cannot be predicted solely from the laser parameters. We use optoacoustics to monitor the temperature rise in real-time in vivo (rabbit) and ex vivo (porcine eye) and to automatically control the coagulation strength. Continuous wave treatment laser radiation and pulsed probe laser light (1-1100 ns) are coupled into the same fibre and are imaged onto the retina by a laser slit lamp. The temperature dependent pressure waves are detected by an ultrasonic transducer embedded in a customary contact lens. Below the coagulation threshold the increase in acoustic amplitude due to thermal tissue expansion is up to 40 %. Best signal to noise ratios > 10 are achieved with probe pulse durations of 1 to 75 ns. Further a time critical algorithm is developed which automatically ceases laser treatment when a certain preset coagulation strength is achieved. Coagulations with similar extent are obtained with this method in vitro and in vivo even when varying the power of the treatment laser by 50 %. These preliminary results are very promising, thus this method might be suitable for an automatic feedback controlled photocoagulation with adjustable coagulation strength.

  15. Microsecond enamel ablation with 10.6μm CO2 laser radiation (United States)

    Góra, W. S.; McDonald, A.; Hand, D. P.; Shephard, J. D.


    Lasers have been previously been used for dental applications, however there remain issues with thermally-induced cracking. In this paper we investigate the impact of pulse length on CO2 laser ablation of human dental enamel. Experiments were carried in vitro on molar teeth without any modification to the enamel surface, such as grinding or polishing. In addition to varying the pulse length, we also varied pulse energy and focal position, to determine the most efficient ablation of dental hard tissue and more importantly to minimize or eradicate cracking. The maximum temperature rise during the multi pulse ablation process was monitored using a set of thermocouples embedded into the pulpal chamber. The application of a laser device in dental surgery allows removal of tissue with higher precision, which results in minimal loss of healthy dental tissue. In this study we use an RF discharge excited CO2 laser operating at 10.6μm. The wavelength of 10.6 μm overlaps with a phosphate band (PO3-4) absorption in dental hard tissue hence the CO2 laser radiation has been selected as a potential source for modification of the tissue. This research describes an in-depth analysis of single pulse laser ablation. To determine the parameters that are best suited for the ablation of hard dental tissue without thermal cracking, a range of pulse lengths (10-200 μs), and fluences (0-100 J/cm2) are tested. In addition, different laser focusing approaches are investigated to select the most beneficial way of delivering laser radiation to the surface (divergent/convergent beam). To ensure that these processes do not increase the temperature above the critical threshold and cause the necrosis of the tissue a set of thermocouples was placed into the pulpal chambers. Intermittent laser radiation was investigated with and without application of a water spray to cool down the ablation site and the adjacent area. Results show that the temperature can be kept below the critical threshold

  16. Dynamics of Radiation and Atoms in Ultrahigh Intensity Laser Fields (United States)


    excitation in strong and ultrastrong optical frequency fields. Advances in laser technology continue to push the boundaries of this interaction in...possible ultrastrong magnetic fields and the electron cyclotron frequency in the bound state can create dynamics, such as is the case for `cycloatoms...promise of increasing the returning rescattering electron energy led to advances in the production of HHG. In addition to (e,2e) and HHG rescattering

  17. Monitored steady-state excitation and recovery (MSSER) radiation force imaging using viscoelastic models. (United States)

    Mauldin, F W; Haider, M A; Loboa, E G; Behler, R H; Euliss, L E; Pfeiler, T W; Gallippi, C M


    Acoustic radiation force imaging methods distinguish tissue structure and composition by monitoring tissue responses to applied radiation force excitations. Although these responses are a complex, multidimensional function of the geometric and viscoelastic nature of tissue, simplified discrete biomechanical models offer meaningful insight to the physical phenomena that govern induced tissue motion. Applying Voigt and standard linear viscoelastic tissue models, we present a new radiation force technique - monitored steady-state excitation and recovery (MSSER) imaging - that tracks both steady-state displacement during prolonged force application and transient response following force cessation to estimate tissue mechanical properties such as elasticity and viscosity. In concert with shear wave elasticity imaging (SWEI) estimates for Young's modulus, MSSER methods are useful for estimating tissue mechanical properties independent of the applied force magnitude. We test our methods in gelatin phantoms and excised pig muscle, with confirmation through mechanical property measurement. Our results measured 10.6 kPa, 14.7 kPa, and 17.1 kPa (gelatin) and 122.4 kPa (pig muscle) with less than 10% error. This work demonstrates the feasibility of MSSER imaging and merits further efforts to incorporate relevant mechanical tissue models into the development of novel radiation force imaging techniques.

  18. Spectral properties and anti-Stokes luminescence of TeO2-BaF2:Ho3+, Ho3+/Yb3+ ceramics and glass excited by 1.9-μm radiation of a Tm:LiYF4 laser (United States)

    Savikin, A. P.; Egorov, A. S.; Budruev, A. V.; Perunin, I. Yu.; Krasheninnikova, O. V.; Grishin, I. A.


    We demonstrate the up-conversion of Tm:LiYF4 infrared (IR) laser radiation with 1908-nm wavelength into visible light with a spectral maximum at 650 nm by ceramics with a composition of (100 - x)TeO2- xBaF2 - 1 wt % HoF3- yYbF3, where x = 20, 30, or 40 mol % and y = 0 or 0.5 wt %. The samples of 60TeO2-40BaF2 - 1 wt % HoF3 - 0.5 wt % YbF3 exhibited anti-Stokes luminescence at a threshold radiation power density of 1.0-1.5 W cm-2.

  19. Laser annealing heals radiation damage in avalanche photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Jin Gyu [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Electrical and Computer Engineering, Waterloo, ON (Canada); Anisimova, Elena; Higgins, Brendon L.; Bourgoin, Jean-Philippe [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada); Jennewein, Thomas [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada); Canadian Institute for Advanced Research, Quantum Information Science Program, Toronto, ON (Canada); Makarov, Vadim [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Electrical and Computer Engineering, Waterloo, ON (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada)


    Avalanche photodiodes (APDs) are a practical option for space-based quantum communications requiring single-photon detection. However, radiation damage to APDs significantly increases their dark count rates and thus reduces their useful lifetimes in orbit. We show that high-power laser annealing of irradiated APDs of three different models (Excelitas C30902SH, Excelitas SLiK, and Laser Components SAP500S2) heals the radiation damage and several APDs are restored to typical pre-radiation dark count rates. Of nine samples we test, six APDs were thermally annealed in a previous experiment as another solution to mitigate the radiation damage. Laser annealing reduces the dark count rates further in all samples with the maximum dark count rate reduction factor varying between 5.3 and 758 when operating at -80 C. This indicates that laser annealing is a more effective method than thermal annealing. The illumination power to reach these reduction factors ranges from 0.8 to 1.6 W. Other photon detection characteristics, such as photon detection efficiency, timing jitter, and afterpulsing probability, fluctuate but the overall performance of quantum communications should be largely unaffected by these variations. These results herald a promising method to extend the lifetime of a quantum satellite equipped with APDs. (orig.)

  20. Effect of Infrared Laser Radiation on Biological Systems. (United States)


    Streptococcus faecium . The deactivation obtained in 60 seconds in the CO2 beam was the equivalent to that produced by a radiation dose of 2.5 M rad...laser pulse of the order of 10-2 seconds duration if all the energy absorbed were taken up by specific vibrational modes of the irradiated molecules

  1. Absorption and generation of femtosecond laser-pulse excited spin currents in noncollinear magnetic bilayers (United States)

    Lalieu, M. L. M.; Helgers, P. L. J.; Koopmans, B.


    Spin currents can be generated on an ultrafast time scale by excitation of a ferromagnetic (FM) thin film with a femtosecond laser pulse. Recently, it has been demonstrated that these ultrafast spin currents can transport angular momentum to neighboring FM layers, being able to change both the magnitude and orientation of the magnetization in the adjacent layer. In this paper, both the generation and absorption of these optically excited spin currents are investigated. This is done using noncollinear magnetic bilayers, i.e., two FM layers separated by a conductive spacer. Spin currents are generated in a Co/Ni multilayer with out-of-plane (OOP) anisotropy, and absorbed by a Co layer with an in-plane (IP) anisotropy. This behavior is confirmed by careful analysis of the laser-pulse induced magnetization dynamics, whereafter it is demonstrated that the transverse spin current is absorbed very locally near the injection interface of the IP layer (90 % within the first ≈2 nm). Moreover, it will also be shown that this local absorption results in the excitation of THz standing spin waves within the IP layer. The dispersion measured for these high-frequency spin waves shows a discrepancy with respect to the theoretical predictions, for which an explanation involving intermixed interface regions is proposed. Lastly, the spin current generation is investigated by using magnetic bilayers with a different number of repeats for the Co/Ni multilayer, which proves to be of great relevance for identifying the optical spin current generation mechanism.

  2. Flow angle dependent photoacoustic Doppler power spectra under intensity-modulated continuous wave laser excitation

    Directory of Open Access Journals (Sweden)

    Yu Tong


    Full Text Available Photoacoustic Doppler (PAD power spectra showing an evident Doppler shift represent the major characteristics of the continuous wave-excited or burst wave-excited versions of PAD flow measurements. In this paper, the flow angle dependences of the PAD power spectra are investigated using an experiment setup that was established based on intensity-modulated continuous wave laser excitation. The setup has an overall configuration that is similar to a previously reported configuration, but is more sophisticated in that it accurately aligns the laser illumination with the ultrasound detection process, and in that it picks up the correct sample position. In the analysis of the power spectra data, we find that the background power spectra can be extracted by combining the output signals from the two channels of the lock-in amplifier, which is very useful for identification of the PAD power spectra. The power spectra are presented and analyzed in opposite flow directions, at different flow speeds, and at different flow angles. The power spectra at a 90° flow angle show the unique properties of symmetrical shapes due to PAD broadening. For the other flow angles, the smoothed power spectra clearly show a flow angle cosine relationship.

  3. The effect of positively chirped laser pulse on energy enhancement of proton acceleration in combinational radiation pressure and bubble regime (United States)

    Vosoughian, H.; Sarri, G.; Borghesi, M.; Hajiesmaeilbaigi, F.; Afarideh, H.


    Proton energy enhancement in a combinational radiation pressure and bubble regime by applying a positively chirped laser pulse has been studied using a series of two-dimensional particle-in-cell simulations. In this regime, the proton injection in the half-first period of an excited plasma wave in an under-dense plasma plays the main role in the acceleration process. Moreover, exciting as high as large-amplitude plasma waves can significantly increase the conversion efficiency of laser energy into kinetic energy of the trapped protons. Here, the utilization of the positively chirped laser pulse is proposed as an effective approach to excite the higher amplitude wake in the combinational regime. Our studies indicate that in the positively chirped combinational regime, the plasma wake with approximately two-fold enhancement is produced that results in the generation of the proton bunch with the narrower energy spread and also the peak enhancement by a factor of two, compared with the un-chirped one. This improvement in proton energy reveals that the chirped laser pulse can be introduced as a tool to tune the energy of generated protons in the combinational radiation pressure and bubble regime.

  4. Control of HOD photodissociation dynamics via bond-selective infrared multiphoton excitation and a femtosecond ultraviolet laser pulse

    DEFF Research Database (Denmark)

    Amstrup, Bjarne; Henriksen, Niels Engholm


    A scheme for controlling the outcome of a photodissociation process is studied. It involves two lasers—one intense laser in the infrared region which is supposed to excite a particular bond in the electronic ground state, and a second short laser pulse in the ultraviolet region which, at the righ...

  5. Laser sources in dentistry and radiation safety regulations (United States)

    De Luca, D.; Gaeta, G. M.; Lepore, M.


    Nowadays laser sources are largely adopted in dentistry due to their unique properties making them good candidates to substitute traditional scalpel and conventional diamond bur in the surgery of the soft and hard oral tissue, respectively. The large use of laser sources outside the research laboratories without the need of highly specialized personnel can ask for a widespread knowledge of safety issues related to this kind of equipment. The main hazard of accidental exposures regards eyes injury but increasing the power of the laser beam also skin can be involved. Safety legislations in Europe and U.S.A. take into account non ionizing radiations and laser radiation for the hazards for the health deriving from physical agents. Laser safety standards introduce 3 useful parameters for hazard characterization: "Accessible Emission Limit" (AEL), "Maximum Permissible Exposure" (MPE) and "Nominal Ocular Hazard Distance" (NOHD). We measured the MPE and NOHD for Er:YAG and other laser sources currently adopted in dentistry and we compared our results with data elaborated from standards in order to single out safe and comfortable working conditions. In fact an experimental assessment of the hazard parameters and the comparison with those of reference from safety standards turns out to be useful in order to estimate the residual hazard that can be still present after applying all the engineering protection and administrative rules.

  6. Nanosecond two-photon excitation fluorescence imaging with a multi color fiber MOPA laser (United States)

    Karpf, Sebastian; Eibl, Matthias; Huber, Robert


    A system is presented that uses a fiber based Master Oscillator Power Amplifier (MOPA) with nanosecond-range pulses for two-photon excitation fluorescence (TPEF) imaging. The robust laser in the extended near infrared is based on an actively modulated electro-optical modulator (EOM), enabling free synchronization of the pulses to any other light source or detection unit. Pulses with a freely programmable duration between 0.4 and 10 ns are generated and then amplified to up to kilowatts of peak power with ytterbium doped fiber amplifiers (YDFA). Since we achieve peak power and duty cycles comparable to standard femto- and picosecond setups, the TPEF signal levels are similar, but realized with a robust and inexpensive fiber-based setup. The delivery fiber is further used as an optional, electronically controllable Raman shifter to effectively shift the 1064 nm light to 1122 nm and to 1186 nm. This allows imaging of a manifold of fluorophores, like e.g. TexasRed, mCherry, mRaspberry and many more. We show TPEF imaging of the autofluorescence of plant leaves of moss and algae, acquired in epi-direction. This modular laser unit can be integrated into existing systems as either a fiber-based, alignment free excitation laser or an extension for multi-modal imaging.

  7. Tunable terahertz radiation from arbitrary profile dielectric grating coated with graphene excited by an electron beam (United States)

    Zhao, Tao; Zhong, Ren-Bin; Hu, Min; Chen, Xiao-Xing; Zhang, Ping; Gong, Sen; Liu, Sheng-Gang


    In this paper, the enhanced terahertz radiation transformed from surface plasmon polaritons, excited by a uniformly moving electron bunch, in a structure consisting of a monolayer graphene supported on a dielectric grating with arbitrary profile is investigated. The results show that the grating profile has significant influence on the dispersion curves and radiation characteristics including radiation frequency and intensity. The dependence of dispersion and radiation characteristics on the grating shape for both the symmetric and asymmetric gratings is studied in detail. Moreover, we find that, for an asymmetric grating with certain profile, there exist two different diffraction types, and one of the two types can provide higher radiation intensity comparing to the other one. These results will definitely facilitate the practical application in developing a room-temperature, tunable, coherent and miniature terahertz radiation source. Project supported by the National Basic Research Program of China (Grant No. 2014CB339801), the National Natural Science Foundation of China (Grant Nos. 61231005, 11305030, and 612111076), the Fundamental Research Funds for the Central Universities of China (Grant No. ZYGX2013J058), and the National High-tech Research and Development Project of China (Grant No. 2011AA010204).

  8. Ovarian response to laser puncture in conditions of ionizing radiation (United States)

    Vylegzhanina, T. A.; Ryzhkovskaya, E. L.


    Experimental results on long-term consequences of laser puncture applied to active points of the projection zones for the reproductive organs in guinea pigs after preliminary exposure to (gamma) -radiation are given. In female guinea pigs, it was shown that combination of external radiation (12.9 mCoul/kg) and incorporated 131I (6.5 mCi/kg) induced morphohistochemical and electron microscopic changes in the ovaries long (6 months) after, which indicated functional tension in the ovarian functioning. Laser biostimulation 3 months after the exposure to (gamma) - radiation induced severe injuries of the ovary, i.e. formation of thin-walled cysts, destruction of interstitial cells of the thecal sheath, by 6 months of the experiment. Functional incompetence of the organ was observed.

  9. Variational Approach for Coupled Backward and Forward Wave Excitation in Free-Electron Lasers

    CERN Document Server

    Yahalom, A; Pinhasi, Y


    In a recent paper [1] we have described a novel variational formulation for the propagation and generation of radiation in wave-guides. The formulation is based on the representation of all the involved quantities in the frequency domain and the decomposition of field and currents in terms of the wave-guide transversal Eigen function. In this work we present the utilization of this formalism to the derivation of a numerical scheme that is used to study the build up of radiation in free electron lasers in the linear approximation.

  10. Efficient enhancement of below-threshold harmonic generation by laser-driven excited states of Cs atom (United States)

    Guo, Qiao-Ling; Li, Peng-Cheng; Zhou, Xiao-Xin; Chu, Shih-I.


    We propose an efficient method for the enhancement of below-threshold harmonic generation (BTHG) by mid-infrared laser-driven excited states of a Cs atom. The BTHG is calculated by solving three-dimensional time-dependent Schrödinger equation accurately and efficiently using the time-dependent generalized pseudospectral method. We adopt an excited state as the initial state of a Cs atom. As a result, the BTHG is significantly enhanced by two orders of magnitude compared with the case of the initial ground state. Furthermore, we find that a single vacuum-ultraviolet pulse can be generated by mid-infrared laser-driven excited states by superposing several below-threshold harmonics of a Cs atom. Our finding suggests that the generation of below-threshold harmonics by laser-driven excited states of an atom can provide a powerful methodology for the production of intense vacuum-ultraviolet pulses.

  11. Multiphoton versus single-photon excitation of photosensitizers for laser-induced fluorescence diagnosis and photodynamic therapy of cancer cells (United States)

    Roelofs, Theo A.; Graschew, Georgi; Schneider, Marc; Rakowsky, Stefan; Sinn, Hanns-joerg; Schlag, Peter M.


    In laser-induced fluorescence diagnosis and photodynamic therapy of cancer the applied photosensitizers (PS) are often covalently derivatized with macromolecules to improve their selective accumulation in the cancerous tissue, while maintaining its single-photon excited photophysical properties. In this contribution methoxy-polyethylene glycol (MPEG, MW ~5 kDa) and human serum albumin (HSA, MW ~60 kDa) are used as PS carriers. Multiphoton (MP) excitation of the PS is favorable as compared to single-photon excitation because the penetration depth of the laser light is improved (>5 mm) due to the longer wavelength of the ~200 fs laser pulses used in this case (700-1050 nm). In this study cotton fibers and silica gel beads (quinone) do not exhibit multiphoton-induced fluorescence. Some derivatized PS (sulforhodamine B, erythrosin B, purpurin) exhibit MP-induced fluorescence, although no single-photon absorption band exists in the spectral region around half the excitation wavelength

  12. Surface plasmon-enhanced two-photon excited whispering-gallery modes ultraviolet laser from Zno microwire

    Directory of Open Access Journals (Sweden)

    Yunpeng Wang


    Full Text Available The two-photon excited UV laser with narrow line width and high Q value was obtained. The total internal reflection from the four side surfaces of the quadrilateral-ZnO microwire offered the whispering gallery mode (WGM resonant cavity. The UV emission, resonant mechanism, and laser mode characteristics were discussed in detail for this special type of micro-cavity. In addition, in order to enhance the power of the two-photon excited UV laser, the surface plasmon enhancement by the Au nanoparticles was also performed and explained well by the theory of the localized surface plasmon.

  13. Surface plasmon-enhanced two-photon excited whispering-gallery modes ultraviolet laser from Zno microwire (United States)

    Wang, Yunpeng; Zhu, Gangbei; Mei, Jingjing; Tian, Cancan; Liu, Hongzhen; Wang, Fei; Zhao, Dongxu


    The two-photon excited UV laser with narrow line width and high Q value was obtained. The total internal reflection from the four side surfaces of the quadrilateral-ZnO microwire offered the whispering gallery mode (WGM) resonant cavity. The UV emission, resonant mechanism, and laser mode characteristics were discussed in detail for this special type of micro-cavity. In addition, in order to enhance the power of the two-photon excited UV laser, the surface plasmon enhancement by the Au nanoparticles was also performed and explained well by the theory of the localized surface plasmon.

  14. Food powder analysis by using transversely excited atmospheric CO2 laser-induced plasma spectroscopy (United States)

    Khumaeni, Ali; Sukra Lie, Zener; Setiabudi, Wahyu; Hendrik Kurniawan, Koo; Kagawa, Kiichiro


    A direct and sensitive analysis of food powder sample has successfully been carried out by utilizing the special characteristics of pulsed transversely excited atmospheric (TEA) CO2 laser. In this study, a food powder was placed in a container made of copper plate and covered by a metal mesh. The container was perpendicularly attached on a metal surface. A high-temperature luminous plasma was induced on a metal surface 5 mm above the mesh. Once the plasma was produced, a strong shock wave was induced, blowing-off of the powder from the container to enter into the plasma to be dissociated and excited. By using this method, a semi-quantitative analysis of food powder was made. The detection limits of Cr in the powdered agar and Cd in the powdered rice were 9 mg/kg and 50 mg/kg, respectively.

  15. Broadband photoluminescence of silicon nanowires excited by near-infrared continuous wave lasers (United States)

    Li, Zongbao; Wang, Xin; Liu, Shaojing; Yang, Jianxin; Shi, KeZhang; Wang, Haiyan; Zhu, Debin; Xing, Xiaobo


    In advanced nanomaterials field, silicon nanowires (SiNWs) play an increasing significant role due to the outstanding optical properties. Although various kinds of investigations for SiNWs in optical characteristic have been proposed, it remained rare study of the photoluminescence (PL) phenomenon. Here, we theoretically and experimentally demonstrate an upconversion PL with broadband spectrum by exciting SiNWs using 980 nm continuous wave laser. PL spectra are efficiently detected and range from 500 nm to 920 nm. An electron can be transferred to higher excitation energy levels by absorbing one photon with the assistance of multi-phonons, producing hot luminescence. The proposed concept of PL phenomenon can be extended to biosensor, fluorescence labeling systems, and miniature broadband optical source emitters.

  16. Modeling classical and quantum radiation from laser-plasma accelerators

    Directory of Open Access Journals (Sweden)

    M. Chen


    Full Text Available The development of models and the “Virtual Detector for Synchrotron Radiation” (vdsr code that accurately describe the production of synchrotron radiation are described. These models and code are valid in the classical and linear (single-scattering quantum regimes and are capable of describing radiation produced from laser-plasma accelerators (LPAs through a variety of mechanisms including betatron radiation, undulator radiation, and Thomson/Compton scattering. Previous models of classical synchrotron radiation, such as those typically used for undulator radiation, are inadequate in describing the radiation spectra from electrons undergoing small numbers of oscillations. This is due to an improper treatment of a mathematical evaluation at the end points of an integration that leads to an unphysical plateau in the radiation spectrum at high frequencies, the magnitude of which increases as the number of oscillation periods decreases. This is important for betatron radiation from LPAs, in which the betatron strength parameter is large but the number of betatron periods is small. The code vdsr allows the radiation to be calculated in this regime by full integration over each electron trajectory, including end-point effects, and this code is used to calculate betatron radiation for cases of experimental interest. Radiation from Thomson scattering and Compton scattering is also studied with vdsr. For Thomson scattering, radiation reaction is included by using the Sokolov method for the calculation of the electron dynamics. For Compton scattering, quantum recoil effects are considered in vdsr by using Monte Carlo methods. The quantum calculation has been benchmarked with the classical calculation in a classical regime.

  17. Counter-propagating radiative shock experiments on the Orion laser and the formation of radiative precursors (United States)

    Clayson, T.; Suzuki-Vidal, F.; Lebedev, S. V.; Swadling, G. F.; Stehlé, C.; Burdiak, G. C.; Foster, J. M.; Skidmore, J.; Graham, P.; Gumbrell, E.; Patankar, S.; Spindloe, C.; Chaulagain, U.; Kozlová, M.; Larour, J.; Singh, R. L.; Rodriguez, R.; Gil, J. M.; Espinosa, G.; Velarde, P.; Danson, C.


    We present results from new experiments to study the dynamics of radiative shocks, reverse shocks and radiative precursors. Laser ablation of a solid piston by the Orion high-power laser at AWE Aldermaston UK was used to drive radiative shocks into a gas cell initially pressurised between 0.1 and 1.0 bar with different noble gases. Shocks propagated at 80 ± 10 km/s and experienced strong radiative cooling resulting in post-shock compressions of ×25 ± 2. A combination of X-ray backlighting, optical self-emission streak imaging and interferometry (multi-frame and streak imaging) were used to simultaneously study both the shock front and the radiative precursor. These experiments present a new configuration to produce counter-propagating radiative shocks, allowing for the study of reverse shocks and providing a unique platform for numerical validation. In addition, the radiative shocks were able to expand freely into a large gas volume without being confined by the walls of the gas cell. This allows for 3-D effects of the shocks to be studied which, in principle, could lead to a more direct comparison to astrophysical phenomena. By maintaining a constant mass density between different gas fills the shocks evolved with similar hydrodynamics but the radiative precursor was found to extend significantly further in higher atomic number gases (∼4 times further in xenon than neon). Finally, 1-D and 2-D radiative-hydrodynamic simulations are presented showing good agreement with the experimental data.

  18. Laser-excited photoemission spectroscopy study of superconducting boron-doped diamond

    Directory of Open Access Journals (Sweden)

    K. Ishizaka, R. Eguchi, S. Tsuda, T. Kiss, T. Shimojima, T. Yokoya, S. Shin, T. Togashi, S. Watanabe, C.-T. Chen, C.Q. Zhang, Y. Takano, M. Nagao, I. Sakaguchi, T. Takenouchi and H. Kawarada


    Full Text Available We have investigated the low-energy electronic state of boron-doped diamond thin film by the laser-excited photoemission spectroscopy. A clear Fermi-edge is observed for samples doped above the semiconductor–metal boundary, together with the characteristic structures at 150×n meV possibly due to the strong electron–lattice coupling effect. In addition, for the superconducting sample, we observed a shift of the leading edge below Tc indicative of a superconducting gap opening. We discuss the electron–lattice coupling and the superconductivity in doped diamond.

  19. Laser-plasma accelerator and femtosecond photon sources-based ultrafast radiation chemistry and biophysics (United States)

    Gauduel, Y. A.


    The initial distribution of energy deposition triggered by the interaction of ionizing radiations (far UV and X rays, electron, proton and accelerated ions) with molecular targets or integrated biological systems is often decisive for the spatio-temporal behavior of radiation effects that take place on several orders of magnitude. This contribution deals with an interdisciplinary approach that concerns cutting-edge advances on primary radiation events, considering the potentialities of innovating strategies based on ultrafast laser science, from femtosecond photon sources to laser-driven relativistic particles acceleration. Recent advances of powerful TW laser sources (~ 1019 Wcm-2) and laser-plasma interactions providing ultrashort relativistic particle beams in the energy domain 2.5-150 MeV open exciting opportunities for the development of high-energy radiation femtochemistry (HERF). Early radiation damages being dependent on the survival probability of secondary electrons and radial distribution of short-lived radicals inside ionization clusters, a thorough knowledge of these processes involves the real-time probing of primary events in the temporal range 10-14-10-11 s. In the framework of a closed synergy between low-energy radiation femtochemistry (LERF) and the emerging domain of HERF, the paper focuses on early phenomena that occur in the prethermal regime of low-energy secondary electrons, considering very short-lived quantum effects in aqueous environments. A high dose-rate delivered by femtosecond electron beam (~ 1011-1013 Gy s-1) can be used to investigate early radiation processes in native ionization tracks, down to 10-12 s and 10-9 m. We explain how this breakthrough favours the innovating development of real-time nanodosimetry in biologically relevant environments and open new perspectives for spatio-temporal radiation biophysics. The emerging domain of HERF would provide guidance for understanding the specific bioeffects of ultrashort particle

  20. Excitation of different chromium centres by synchrotron radiation in MgO:Cr single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Shablonin, E. [Institute of Physics, University of Tartu, Ravila Str. 14c, 50411 Tartu (Estonia); Popov, A.I., E-mail: [Institute of Solid State Physics, University of Latvia, Kengaraga 8, Riga LV-1063 (Latvia); Lushchik, A., E-mail: [Institute of Physics, University of Tartu, Ravila Str. 14c, 50411 Tartu (Estonia); Kotlov, A. [Photon Science at DESY, Notkestrasse 85, 22607 Hamburg (Germany); Dolgov, S. [Institute of Physics, University of Tartu, Ravila Str. 14c, 50411 Tartu (Estonia)


    The excitation spectra for the emissions of chromium-containing centres have been measured at 10 K using synchrotron radiation of 4–32 eV in MgO single crystals with different content of Cr{sup 3+} (5–850 ppm) and Ca{sup 2+} impurity ions. Both virgin crystals and the samples preliminarily irradiated with x-rays at 295 K have been studied. The role of complex chromium centres containing two Cr{sup 3+} and a cation vacancy (sometimes nearby a Ca{sup 2+} ion) on the luminescence processes and the transformation/creation of structural defects has been analysed. Such anharmonic complex centres could serve as the seeds for the creation of 3D defects that facilitate the cracking and brittle destruction of MgO crystals under their irradiation with ∼GeV heavy ions providing extremely high excitation density within cylindrical ion tracks.

  1. Two-photon excited spectroscopies of ex vivo human skin endogenous species irradiated by femtosecond laser pulses (United States)

    Chen, Jianxin; Zhuo, Shuangmu; Luo, Tianshu; Zhao, Jingjun


    Two-photon excited spectroscopies from ex vivo human skin are investigated by using a femtosecond laser and a confocal microscope (Zeiss LSM 510 META). In the dermis, collagen is responsible for second harmonic generation (SHG); elastin, nicotinamide adenine dinucleotide (NADH), melanin and porphyrin are the primary endogenous sources of two-photon excited autofluorescence. In the epidermis, keratin, NADH, melanin and porphyrins contribute to autofluorescence signals. The results also show that the SHG spectra have the ability to shift with the excitation wavelength and the autofluorescence spectra display a red shift of the spectral peaks when increasing the excitation wavelength. These results may have practical implications for diagnosis of skin diseases.

  2. Interaction of Er:YAG laser radiation with ureter tissue (United States)

    Jelínkova, Helena; Koranda, Petr; Němec, Michal; Šulc, Jan; Köhler, Oto; Drlík, Pavel; Miyagi, Mitsunobu; Shi, Yi-Wei; Matsuura, Yuji


    The aim of the work was to investigate the possibility of the ureter wall perforation by Er:YAG laser radiation and to explore the basic interaction characteristics for ureter surface and its deep structures. For these experiments Er:YAG laser system (wavelength 2.94 μm) working in free-running and Q-switched regime was utilized. Laser radiation was delivered to the investigated tissue by a special waveguide system. The basic part was a cyclic olefin polymer-coated silver hollow glass waveguide (inner/outer diameter 700/850 μm or 320/450 μm). Sealed cap of the waveguide was used for contact treatment. Maximum interaction pulse energy and length for free-running Er:YAG I laser with the 700μm waveguide were 100mJ and 200μs, respectively (corresponding intensity was 130 kW/cm2). Similarly the maximum interaction pulse energy and length for free-running Er:YAG II laser with the 320 μm waveguide were 80 mJ and 200 μs , respectively (corresponding intensity was 500 kW/cm2). Maximum interaction pulse energy and length in Q-switched regime were 17 mJ and 70 ns, respectively (corresponding intensity 63 MW/cm2). The number of pulses needed to perforate the ureter wall tissue (thickness ~1 mm) for using long 200 μs Er:YAG pulses (thermal ablation) and short 70 ns Er:YAG pulses (photoablation) was found. From the histological evaluation it follows that the application of Q-switched Er:YAG laser radiation on ureteral tissue resulted in minimum adjacent tissue alteration (up to 50μm from the surface) without any influence on the deeper layers.

  3. TEA HF laser with a high specific radiation energy (United States)

    Puchikin, A. V.; Andreev, M. V.; Losev, V. F.; Panchenko, Yu. N.


    Results of experimental studies of the chemical HF laser with a non-chain reaction are presented. The possibility of the total laser efficiency of 5 % is shown when a traditional C-to-C pumping circuit with the charging voltage of 20-24 kV is used. It is experimentally shown that the specific radiation output energy of 21 J/l is reached at the specific pump energy of 350 J/l in SF6/H2 = 14/1 mixture at the total pressure of 0.27 bar.

  4. A total internal reflection-fluorescence correlation spectroscopy setup with pulsed diode laser excitation (United States)

    Weger, Lukas; Hoffmann-Jacobsen, Kerstin


    Fluorescence correlation spectroscopy (FCS) measures fluctuations in a (sub-)femtoliter volume to analyze the diffusive behavior of fluorescent particles. This highly sensitive method has proven to be useful for the analysis of dynamic biological systems as well as in chemistry, physics, and material sciences. It is routinely performed with commercial fluorescence microscopes, which provide a confined observation volume by the confocal technique. The evanescent wave of total internal reflectance (TIR) is used in home-built systems to permit a surface sensitive FCS analysis. We present a combined confocal and TIR-FCS setup which uses economic low-power pulsed diode lasers for excitation. Excitation and detection are coupled to time-correlated photon counting hardware. This allows simultaneous fluorescence lifetime and FCS measurements in a surface-sensitive mode. Moreover, the setup supports fluorescence lifetime correlation spectroscopy at surfaces. The excitation can be easily switched between TIR and epi-illumination to compare the surface properties with those in liquid bulk. The capabilities of the presented setup are demonstrated by measuring the diffusion coefficients of a free dye molecule, a labeled polyethylene glycol, and a fluorescent nanoparticle in confocal as well as in TIR-FCS.

  5. Two-photon excited whispering-gallery mode ultraviolet laser from an individual ZnO microneedle (United States)

    Zhu, G. P.; Xu, C. X.; Zhu, J.; Lv, C. G.; Cui, Y. P.


    Wurtzite structural ZnO microneedles with hexagonal cross section were fabricated by vapor-phase transport method and an individual microneedle was employed as a lasing microcavity. Under excitation of a femtosecond pulse laser with 800 nm wavelength, the ultraviolet (UV) laser emission was obtained, which presented narrow linewidth and high Q value. The UV emission, resonant mechanism, and laser mode characteristics were discussed in detail. The results demonstrated that the UV laser originated from the whispering-gallery mode induced by two-photon absorption assisted by Rabi oscillation.

  6. Relaxation channels of multi-photon excited xenon clusters. (United States)

    Serdobintsev, P Yu; Rakcheeva, L P; Murashov, S V; Melnikov, A S; Lyubchik, S; Timofeev, N A; Pastor, A A; Khodorkovskii, M A


    The relaxation processes of the xenon clusters subjected to multi-photon excitation by laser radiation with quantum energies significantly lower than the thresholds of excitation of atoms and ionization of clusters were studied. Results obtained by means of the photoelectron spectroscopy method showed that desorption processes of excited atoms play a significant role in the decay of two-photon excited xenon clusters. A number of excited states of xenon atoms formed during this process were discovered and identified.

  7. Tuning excitation laser wavelength for secondary resonance in low-intensity phase-selective laser-induced breakdown spectroscopy for in-situ analytical measurement of nanoaerosols (United States)

    Xiong, Gang; Li, Shuiqing; Tse, Stephen D.


    In recent years, a novel low-intensity phase-selective laser-induced breakdown spectroscopy (PS-LIBS) technique has been developed for unique elemental-composition identification of aerosolized nanoparticles, where only the solid-phase nanoparticles break down, forming nanoplasmas, without any surrounding gas-phase breakdown. Additional work has demonstrated that PS-LIBS emissions can be greatly enhanced with secondary resonant excitation by matching the excitation laser wavelength with an atomic transition line in the formed nanoplasma, thereby achieving low limits of detection. In this work, a tunable dye laser is employed to investigate the effects of excitation wavelength and irradiance on in-situ PS-LIBS measurements of TiO2 nanoaerosols. The enhancement factor by resonant excitation can be 220 times greater than that for non-resonant cases under similar conditions. Moreover, the emitted spectra are unique for the selected resonant transition lines for a given element, suggesting the potential to make precise phase-selective and analyte-selective measurements of nanoparticles in a multicomponent multiphase system. The enhancement factor by resonant excitation is highly sensitive to excitation laser wavelength, with narrow excitation spectral windows, i.e., 0.012 to 0.023 nm (FWHM, full width at half maximum) for Ti (I) neutral atomic lines, and 0.051 to 0.139 nm (FWHM) for Ti (II) single-ionized atomic lines. Boltzmann analysis of the emission intensities, temporal response of emissions, and emission dependence on excitation irradiance are investigated to understand aspects of the generated nanoplasmas such as temperature, local thermodynamic equilibrium (LTE), and excitation mechanism.

  8. Strong and radiative decays of excited vector mesons and predictions for a new ϕ (1930 ) resonance (United States)

    Piotrowska, Milena; Reisinger, Christian; Giacosa, Francesco


    We study the phenomenology of two nonets of excited vector mesons, {ρ (1450 ),K*(1410 ),ω (1420 ),ϕ (1680 )} and {ρ (1700 ),K*(1680 ),ω (1650 ),ϕ (???)} , which (roughly) correspond to radially excited 2 3S1 and to orbitally excited 1 3D1 vector mesons. We evaluate the strong and radiative decays of these mesons into pseudoscalar and ground-state vector mesons by using an effective relativistic QFT model based on flavor symmetry. We compare decay widths and branching ratios with various experimental results listed in the PDG. An overall agreement of theory with experiment reinforces the standard quark-antiquark assignment of the resonances mentioned above. Predictions for not-yet-measured quantities are also made. In particular, we shall also make predictions for the not-yet-discovered s s ¯ state of the 1 3D1 nonet, denoted as ϕ (???) . Its mass can be estimated to be about 1930 MeV; hence we shall call this putative state ϕ (1930 ). Its main decays are into K K*(892 ) (about 200 MeV) and K K (about 100 MeV). Since this state couples also to γ η , it can be searched for in the near future in the photoproduction-based experiments GlueX and CLAS12 at Jefferson Lab.

  9. Excited meson radiative transitions from lattice QCD using variationally optimized operators

    Energy Technology Data Exchange (ETDEWEB)

    Shultz, Christian J. [Old Dominion Univ., Norfolk, VA (United States); Dudek, Jozef J. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Old Dominion Univ., Norfolk, VA (United States); Edwards, Robert G. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)


    We explore the use of 'optimized' operators, designed to interpolate only a single meson eigenstate, in three-point correlation functions with a vector-current insertion. These operators are constructed as linear combinations in a large basis of meson interpolating fields using a variational analysis of matrices of two-point correlation functions. After performing such a determination at both zero and non-zero momentum, we compute three-point functions and are able to study radiative transition matrix elements featuring excited state mesons. The required two- and three-point correlation functions are efficiently computed using the distillation framework in which there is a factorization between quark propagation and operator construction, allowing for a large number of meson operators of definite momentum to be considered. We illustrate the method with a calculation using anisotopic lattices having three flavors of dynamical quark all tuned to the physical strange quark mass, considering form-factors and transitions of pseudoscalar and vector meson excitations. In conclusion, the dependence on photon virtuality for a number of form-factors and transitions is extracted and some discussion of excited-state phenomenology is presented.

  10. Ideal radiation source for plasma spectroscopy generated by laser ablation (United States)

    Hermann, Jörg; Grojo, David; Axente, Emanuel; Gerhard, Christoph; Burger, Miloš; Craciun, Valentin


    Laboratory plasmas inherently exhibit temperature and density gradients leading to complex investigations. We show that plasmas generated by laser ablation can constitute a robust exception to this. Supported by emission features not observed with other sources, we achieve plasmas of various compositions which are both uniform and in local thermodynamic equilibrium. These properties characterize an ideal radiation source opening multiple perspectives in plasma spectroscopy. The finding also constitutes a breakthrough in the analytical field as fast analyses of complex materials become possible.

  11. EUV spectra of Gd and Tb ions excited in laser-produced and vacuum spark plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Churilov, S S; Kildiyarova, R R; Ryabtsev, A N; Sadovsky, S V [Establishment of the Russian Academy of Sciences Institute of Spectroscopy RAS, Troitsk, Moscow region 142190 (Russian Federation)], E-mail:


    Extreme UV spectra of the gadolinium and terbium ions excited in the laser-produced plasma and vacuum spark sources were recorded in the 40-120 A region and investigated on the basis of the Hartree-Fock calculations using Cowan code. The intense peaks in the 65-75 A region of the vacuum spark spectra were interpreted as a manifold of the 4d{sup 10}4f{sup m}-4d{sup 9}4f{sup m+1} transitions in the ions with a partially filled 4f shell. The drastic narrowing of these peaks was observed in the spectra of the laser-produced plasma. It was explained by a change of the 4d{sup 10}4f{sup m}-4d{sup 9}4f{sup m+1} (m>2) transition arrays mostly contributing to the intensity of the peaks in the vacuum spark spectra for the 4-4 transitions in the simplest spectra of the 4p{sup 6}4d{sup k} (k=8-10) and 4d{sup 10}4f{sup m} (m=1-2) ground configuration ions predominantly excited in hotter laser-produced plasma. The most intense lines of the 4d{sup 10}4f{sup 2}-4d{sup 10}4f5d transitions in the Gd XVII and Tb XVIII spectra were classified for the first time.

  12. Radiative Decay Widths of Ground and Excited States of Vector Charmonium and Bottomonium

    Directory of Open Access Journals (Sweden)

    Hluf Negash


    Full Text Available We study the radiative decay widths of vector quarkonia for the process of J/ψ(nS→ηc(nSγ and Υ(nS→ηb(nSγ (for principal quantum numbers n=1,2,3 in the framework of Bethe-Salpeter equation under the covariant instantaneous ansatz using a 4×4 form of BSE. The parameters of the framework were determined by a fit to the mass spectrum of ground states of pseudoscalar and vector quarkonia, such as ηc, ηb, J/ψ, and Υ. These input parameters so fixed were found to give good agreements with data on mass spectra of ground and excited states of pseudoscalar and vector quarkonia, leptonic decay constants of pseudoscalar and vector quarkonia, two-photon decays, and two-gluon decays of pseudoscalar quarkonia in our recent paper. With these input parameters so fixed, the radiative decay widths of ground (1S and excited (2S,3S states of heavy vector quarkonia (J/Ψ and Υ are calculated and found to be in reasonable agreement with data.

  13. Interaction of Repetitively Pulsed High Energy Laser Radiation With Matter (United States)

    Hugenschmidt, Manfred


    The paper is concerned with laser target interaction processes involving new methods of improving the overall energy balance. As expected theoretically, this can be achieved with high repetition rate pulsed lasers even for initially highly reflecting materials, such as metals. Experiments were performed by using a pulsed CO2 laser at mean powers up to 2 kW and repetition rates up to 100 Hz. The rates of temperature rise of aluminium for example were thereby increased by lore than a factor of 3 as compared to cw-radiation of comparable power density. Similar improvements were found for the overall absorptivities that were increased by this method by more than an order of magnitude.

  14. Laser system for testing radiation imaging detector circuits (United States)

    Zubrzycka, Weronika; Kasinski, Krzysztof


    Performance and functionality of radiation imaging detector circuits in charge and position measurement systems need to meet tight requirements. It is therefore necessary to thoroughly test sensors as well as read-out electronics. The major disadvantages of using radioactive sources or particle beams for testing are high financial expenses and limited accessibility. As an alternative short pulses of well-focused laser beam are often used for preliminary tests. There are number of laser-based devices available on the market, but very often their applicability in this field is limited. This paper describes concept, design and validation of laser system for testing silicon sensor based radiation imaging detector circuits. The emphasis is put on keeping overall costs low while achieving all required goals: mobility, flexible parameters, remote control and possibility of carrying out automated tests. The main part of the developed device is an optical pick-up unit (OPU) used in optical disc drives. The hardware includes FPGA-controlled circuits for laser positioning in 2 dimensions (horizontal and vertical), precision timing (frequency and number) and amplitude (diode current) of short ns-scale (3.2 ns) light pulses. The system is controlled via USB interface by a dedicated LabVIEW-based application enabling full manual or semi-automated test procedures.

  15. High resolution laser micro sintering / melting using q-switched and high brilliant laser radiation (United States)

    Exner, H.; Streek, A.


    Since the discovery of selective laser sintering/melting, numerous modifications have been made to upgrade or customize this technology for industrial purposes. Laser micro sintering (LMS) is one of those modifications: Powders with particles in the range of a few micrometers are used to obtain products with highly resolved structures. Pulses of a q-switched laser had been considered necessary in order to generate sinter layers from the micrometer scaled metal powders. LMS has been applied with powders from metals as well as from ceramic and cermet feedstock's to generate micro parts. Recent technological progress and the application of high brilliant continuous laser radiation have now allowed an efficient laser sintering/melting of micrometer scaled metal powders. Thereby it is remarkable that thin sinter layers are generated using high continuous laser power. The principles of the process, the state of the art in LMS concerning its advantages and limitations and furthermore the latest results of the recent development of this technology will be presented. Laser Micro Sintering / Laser Micro Melting (LMM) offer a vision for a new dimension of additive fabrication of miniature and precise parts also with application potential in all engineering fields.

  16. Standing-wave-excited multiplanar fluorescence in a laser scanning microscope reveals 3D information on red blood cells

    CERN Document Server

    Amor, Rumelo; Amos, William Bradshaw; McConnell, Gail


    Standing-wave excitation of fluorescence is highly desirable in optical microscopy because it improves the axial resolution. We demonstrate here that multiplanar excitation of fluorescence by a standing wave can be produced in a single-spot laser scanning microscope by placing a plane reflector close to the specimen. We report that the relative intensities in each plane of excitation depend on the Stokes shift of the fluorochrome. We show by the use of dyes specific for the cell membrane how standing-wave excitation can be exploited to generate precise contour maps of the surface membrane of red blood cells, with an axial resolution of ~90 nm. The method, which requires only the addition of a plane mirror to an existing confocal laser scanning microscope, may well prove useful in studying diseases which involve the red cell membrane, such as malaria.

  17. Single-active-electron analysis of laser-polarization effects on atomic/molecular multiphoton excitation. (United States)

    Kanno, Manabu; Inada, Nobuyoshi; Kono, Hirohiko


    We theoretically explore the effects of optical ellipticity on single-active-electron multiphoton excitation in atoms and (nearly) spherical molecules irradiated by intense polarized laser fields. This work was motivated by the experimental and theoretical studies of Hertel et al. [Phys. Rev. Lett. 102, 023003 (2009) and Phys. Rev. A 79, 053414 (2009)], who reported pronounced changes in the near-infrared-induced ion yields of xenon and C60 as a function of ellipticity (in particular, yield reduction for circular polarization) at low light intensities and derived a perturbative cross section formula to describe such polarization effects by assuming that the excited-state energies and radial transition electric dipole moments of the system are independent of the azimuthal quantum number l. First, by reformulating the N-photon absorption cross section of a single active electron, we prove that their assumptions reduce the network of optically allowed transition pathways into what we call the "Pascal triangle" consisting of (N + 1) (N + 2)/2 states only. Next, nonperturbative analytical and numerical solutions of the time-dependent Schrödinger equation for a simple model of two-photon excitation are presented not only in the low-intensity regime but also in the high-intensity regime. The results show that the determining factor of ellipticity-dependent multiphoton excitation probability is transition moment magnitudes and that the detailed energetic structure of the system also becomes important at high intensities. The experimentally observed flattening of the ion yields of xenon and C60 with increasing intensity can be explained without a saturation effect, which was previously deemed to be responsible for it. We also argue the applicability range of the cross section formula by Hertel et al. and the identity of the "doorway state" for ionization of C60.

  18. Single-active-electron analysis of laser-polarization effects on atomic/molecular multiphoton excitation (United States)

    Kanno, Manabu; Inada, Nobuyoshi; Kono, Hirohiko


    We theoretically explore the effects of optical ellipticity on single-active-electron multiphoton excitation in atoms and (nearly) spherical molecules irradiated by intense polarized laser fields. This work was motivated by the experimental and theoretical studies of Hertel et al. [Phys. Rev. Lett. 102, 023003 (2009) and Phys. Rev. A 79, 053414 (2009)], who reported pronounced changes in the near-infrared-induced ion yields of xenon and C60 as a function of ellipticity (in particular, yield reduction for circular polarization) at low light intensities and derived a perturbative cross section formula to describe such polarization effects by assuming that the excited-state energies and radial transition electric dipole moments of the system are independent of the azimuthal quantum number l. First, by reformulating the N-photon absorption cross section of a single active electron, we prove that their assumptions reduce the network of optically allowed transition pathways into what we call the "Pascal triangle" consisting of (N + 1) (N + 2)/2 states only. Next, nonperturbative analytical and numerical solutions of the time-dependent Schrödinger equation for a simple model of two-photon excitation are presented not only in the low-intensity regime but also in the high-intensity regime. The results show that the determining factor of ellipticity-dependent multiphoton excitation probability is transition moment magnitudes and that the detailed energetic structure of the system also becomes important at high intensities. The experimentally observed flattening of the ion yields of xenon and C60 with increasing intensity can be explained without a saturation effect, which was previously deemed to be responsible for it. We also argue the applicability range of the cross section formula by Hertel et al. and the identity of the "doorway state" for ionization of C60.

  19. Nozzle flow of laser-heated radiating hydrogen with application to a laser-heated rocket (United States)

    Kemp, N. H.; Root, R. G.


    This paper presents a model for the steady heating of flowing hydrogen by a CW 10.6 micron laser, to consider the feasibility of a laser-heated rocket. The hydrogen flow and the laser beam are parallel, and move into a converging-diverging nozzle. The absorption of laser energy is initiated by a laser-supported combustion wave. The hydrogen is in chemical equilibrium, absorbs laser energy by inverse Bremsstrahlung, and loses energy by radiation. The hydrogen flow was calculated from the rear of the LSC wave to the throat. Estimates of convective heat losses were made using a hydrogen boundary layer analysis. Specific impulse, obtained by expanding isentropically from the throat to 1 atm or a vacuum, varies from 1400 to 3000 s. Radiation losses are 5 to 20%, though the energy fluxes to the walls are quite high. Convective loss estimates are high enough to indicate that coupling to the hot gas flow is required for a 10 kW engine, but not for a 5 MW engine.

  20. Measurements of Ionizing Radiation Doses Induced by High Irradiance Laser on Targets in LCLS MEC Instrument

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Liu, J. C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Prinz, A. A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Rokni, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Tran, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Woods, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Xia, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Galter, e. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Lee, H. -J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Milathianaki, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Nagler, B. [SLAC National Accelerator Lab., Menlo Park, CA (United States)


    Comprehensive measurements for photon and neutron radiation doses generated from laser-plasma interaction at SLAC’s MEC laser facility have been conducted. The goals of the measurements were to; determine the radiation dose per laser shot as a function of laser, optic and target parameters that are relevant to the MEC laser operations; validate the RPD-developed analytic model for photon dose calculations; and evaluate the performance of various types of passive and active detectors in the laser-induced radiation fields.

  1. Plasma Dipole Oscillation Excited by Trapped Electrons Leading to Bursts of Coherent Radiation

    CERN Document Server

    Kwon, Kyu Been; Song, Hyung Seon; Kim, Young-Kuk; Ersfeld, Bernhard; Jaroszynski, Dino A; Hur, Min Sup


    Plasma dipole oscillation (PDO) depicted as harmonic motion of a spatially localized block of electrons has, until now, been hypothetical. In practice, the plasma oscillation occurs always as a part of a plasma wave. Studies on radiation burst from plasmas have focused only on coupling of the plasma wave and electromagnetic wave. Here we show that a very-high-field PDO can be generated by the electrons trapped in a moving train of potential wells. The electrons riding on the potential train coherently construct a local dipole moment by charge separation. The subsequent PDO is found to persist stably until its energy is emitted entirely via coherent radiation. In our novel method, the moving potentials are provided by two slightly-detuned laser pulses colliding in a non-magnetized plasma. The radiated energy reaches several millijoules in the terahertz spectral region. The proposed method provides a way of realizing the PDO as a new radiation source in the laboratory. PDO as a mechanism of astrophysical radio-...

  2. Contribution to the beam plasma material interactions during material processing with TEA CO2 laser radiation (United States)

    Jaschek, Rainer; Konrad, Peter E.; Mayerhofer, Roland; Bergmann, Hans W.; Bickel, Peter G.; Kowalewicz, Roland; Kuttenberger, Alfred; Christiansen, Jens


    The TEA-CO2-laser (transversely excited atmospheric pressure) is a tool for the pulsed processing of materials with peak power densities up to 1010 W/cm2 and a FWHM of 70 ns. The interaction between the laser beam, the surface of the work piece and the surrounding atmosphere as well as gas pressure and the formation of an induced plasma influences the response of the target. It was found that depending on the power density and the atmosphere the response can take two forms. (1) No target modification due to optical break through of the atmosphere and therefore shielding of the target (air pressure above 10 mbar, depending on the material). (2) Processing of materials (air pressure below 10 mbar, depending on the material) with melting of metallic surfaces (power density above 0.5 109 W/cm2), hole formation (power density of 5 109 W/cm2) and shock hardening (power density of 3.5 1010 W/cm2). All those phenomena are usually linked with the occurrence of laser supported combustion waves and laser supported detonation waves, respectively for which the mechanism is still not completely understood. The present paper shows how short time photography and spatial and temporal resolved spectroscopy can be used to better understand the various processes that occur during laser beam interaction. The spectra of titanium and aluminum are observed and correlated with the modification of the target. If the power density is high enough and the gas pressure above a material and gas composition specific threshold, the plasma radiation shows only spectral lines of the background atmosphere. If the gas pressure is below this threshold, a modification of the target surface (melting, evaporation and solid state transformation) with TEA-CO2- laser pulses is possible and the material specific spectra is observed. In some cases spatial and temporal resolved spectroscopy of a plasma allows the calculation of electron temperatures by comparison of two spectral lines.

  3. Endoscopic diode laser therapy for chronic radiation proctitis. (United States)

    Polese, Lino; Marini, Lucia; Rizzato, Roberto; Picardi, Edgardo; Merigliano, Stefano


    The purpose of this study is to determine the effectiveness of endoscopic diode laser therapy in patients presenting rectal bleeding due to chronic radiation proctitis (CRP). A retrospective analysis of CRP patients who underwent diode laser therapy in a single institution between 2010 and 2016 was carried out. The patients were treated by non-contact fibers without sedation in an outpatient setting. Fourteen patients (median age 77, range 73-87 years) diagnosed with CRP who had undergone high-dose radiotherapy for prostatic cancer and who presented with rectal bleeding were included. Six required blood transfusions. Antiplatelet (three patients) and anticoagulant (two patients) therapy was not suspended during the treatments. The patients underwent a median of two sessions; overall, a mean of 1684 J of laser energy per session was used. Bleeding was resolved in 10/14 (71%) patients, and other two patients showed improvement (93%). Only one patient, who did not complete the treatment, required blood transfusions after laser therapy; no complications were noted during or after the procedures. Study findings demonstrated that endoscopic non-contact diode laser treatment is safe and effective in CRP patients, even in those receiving antiplatelet and/or anticoagulant therapy.

  4. Use of 3-um laser radiation in middle ear surgery (United States)

    Pratisto, Hans S.; Frenz, Martin; Ith, Michael; Altermatt, Hans J.; Weber, Heinz P.


    An inner ear model was used to demonstrate thermal and mechanical effects occurring during Erbium laser stapedotomy. Results of inverse schlieren optical flash photography and time resolved pressure amplitude measurements indicate the existence of safe laser parameters for stapes foot plate perforation. Due to the high absorption of 3 micrometers radiation in water, efficient bone ablation and precise fenestration with small thermally damaged zones is achieved. Pressure transients caused by the explosive ablation process correlate with the spiking of the laser intensity. The energy of a laser pulse, directly applied into the perilymph through an already existing perforation, creates a vapor channel which afterwards collapses, sending out a strong pressure transient. The maximal amplitude of this pressure transient depends on the geometry and dynamics of the vapor channel and is several times stronger than the pressure amplitudes generated by the bone ablation process. This study shows that no permanent hearing loss or damage of inner ear structures is expected using an Erbium laser fluence of 10 J/cm2.

  5. a Study of Reactive Quenching of Xenon by Chlorides Using Two-Photon Laser Excitation (United States)

    Bruce, Michael Richard


    State-selective two-photon laser excitation is utilized to study inelastic energy transfer in rare gas halide reactions. These studies have helped to understand the energy pathways and reaction processes important to the physics of the excimer laser. Moreover, they have lead to a better fundamental understanding of electronic energy transfer. In particular, reactions of Xe (5p ^5np, np^' n = 6,7) with chlorine molecules are studied. The observed quench rates were surprisingly large; experimental cross sections extended from 400A^2 to 1000A^2. Previous models for the excimer laser used only reaction cross sections of 200A ^2 for the lowest excited states of xenon (5p^56s); they neglected all more highly excited states. Nevertheless, it was shown that the large reactions rates are consistent with current theory; the reaction Rg^{*} + Cl_2 is vibronically coupled onto the Rg^{+} + Cl _sp{2}{-} ionic surface by means of the Cl_2 molecular vibrations. In addition, the neutral termolecular reactive collisions, Rg^{*} + Cl _2 + Rg to RgCl^{*} + Cl + Rg, were observed. The large rates (~10 ^{-28}cm^6 /sec) were understood by means of an orbiting collision complex model; the role of the third body (Rg) was not to take up excess thermal energy as had been assumed in previous calculations, but to enhance the probability for charge transfer between the two neutral species (Rg ^{*} and Cl_2) by altering the effective ionization limit. This process could be important in any high density neutral reaction that proceeds through an ionic intermediary. These results have shown that termolecular reactions are universal to many forms of energy transfer reactions; furthermore, we can no longer hope to understand chemistry at high pressures by a study of binary reactions at low pressures. Also, quenching measurements in pure rare gases were studied. Bimolecular reaction rates were determined for Xe (5p^5np, np^ ' n = 6,7) in xenon and argon buffer gases. In general, the quenching rates

  6. Counter-streaming radiative shock experiments on the Orion laser (United States)

    Suzuki-Vidal, F.; Clayson, T.; Swadling, G. F.; Patankar, S.; Burdiak, G. C.; Lebedev, S. V.; Smith, R. A.; Stehle, C.; Chaulagain, U.; Singh, R. L.; Larour, J.; Kozlova, M.; Spindloe, C.; Foster, J.; Skidmore, J.; Gumbrell, E.; Graham, P.; Danson, C.


    The formation of radiative shocks, shocks in which the structure of density and temperature is affected by radiation from the shock-heated matter, is ubiquitous in many astrophysical scenarios. Experiments were performed at the Orion laser using a new target configuration that allows studying the formation of single and counter-streaming radiative shocks in gas-filled targets (Ne, Ar, Kr, Xe), with initial pressures 0.1-1 bar and a driver intensity of 6x1014 W/cm2 . The shocks propagate at velocities >60 km/s and were diagnosed with optical interferometry (streaked and time-resolved) and point-projection X-ray backlighting allowing to probe simultaneously the pre-shock radiative precursor and the shock front itself. Besides varying the extent of the radiative precursor the results show that different gases seem to have an effect on the shock front as evidenced by a number of spatial features. The results are compared with radiative hydrodynamics simulations in 1-D (HELIOS) and 2-D (NYM/PETRA). Supported by Orion Academic Access, the Royal Society, EPSRC, Labex PLAS@PAR. Currently at (2) LLNL, USA, (3) ELI, CZ, (4) First Light Fusion, UK.

  7. Resonant excitation of ethylene molecules in the combustion flame CVD of diamond using a wavelength tunable CO2 laser (United States)

    Xie, Z. Q.; Park, J. B.; He, X. N.; Gao, Y.; Zhou, Y. S.; Lu, Y. F.


    CO2 laser resonant excitations of precursor molecules were applied in combustion flame synthesis of diamond films. The combustion flame was produced from a mixture of ethylene (C2H4), acetylene (C2H2) and oxygen (O2). A wavelength-tunable CO2 laser with wavelength range from 9.2 to 10.9 μm was used for wavelength-matched excitation of the ethylene molecules. By irradiating the flame using CO2 laser at 10.532 μm, the ethylene molecules were resonantly excited through the CH2 wagging vibrational mode (ν7, 949.3 cm-1). Irradiation of the flame using the common CO2 laser wavelength at 10.591 μm was also carried out for comparison. It was found that diamond synthesis was more obviously enhanced by the CO2 laser resonant excitation at 10.532 μm as compared to that at 10.591 μm. Firstly, the flame was shortened by 50%, indicating a promoted reaction in the process. Secondly, the diamond grain sizes as well as the diamond film thicknesses were increased by 200~300% and 160% respectively, indicating a higher growth rate of diamond films. Finally, Raman spectra of the diamond sample showed a sharp diamond peak at 1334 cm-1 and a suppressed G-band, indicating higher diamond quality.

  8. Laser excited analytical atomic and ionic fluorescence in flames, furnaces and inductively coupled plasmas—I. General considerations (United States)

    Omenetto, N.; Human, H. G. C.

    Several important parameters for the analytical use of laser excited fluorescence spectrometry in flames, graphite furnaces and inductively coupled plasmas are discussed in some detail. These parameters include the laser characteristics such as peak power, pulse duration, spectral bandwidth and repetition rate, the choice of the excitation line, the optical arrangement and the detection system, this last one centred on the widespread use of the boxcar averager. It is shown that, if the ultimate sensitivity is the goal to be achieved, then the choice must be the electrothermal atomization. However, even for flames and inductively coupled plasmas, excellent results are possible provided that: (i) the laser system allows complete spectral coverage in the ultraviolet: (ii) saturation of the fluorescence signal can be approached over a large sample volume; and (iii) the gated detection parameters and the laser repetition frequency are optimized with respect to each other so as to reach the maximum signal-to-noise ratio.

  9. Multi-point scanning two-photon excitation microscopy by utilizing a high-peak-power 1042-nm laser. (United States)

    Otomo, Kohei; Hibi, Terumasa; Murata, Takashi; Watanabe, Hirotaka; Kawakami, Ryosuke; Nakayama, Hiroshi; Hasebe, Mitsuyasu; Nemoto, Tomomi


    The temporal resolution of a two-photon excitation laser scanning microscopy (TPLSM) system is limited by the excitation laser beam's scanning speed. To improve the temporal resolution, the TPLSM system is equipped with a spinning-disk confocal scanning unit. However, the insufficient energy of a conventional Ti:sapphire laser source restricts the field of view (FOV) for TPLSM images to a narrow region. Therefore, we introduced a high-peak-power Yb-based laser in order to enlarge the FOV. This system provided three-dimensional imaging of a sufficiently deep and wide region of fixed mouse brain slices, clear four-dimensional imaging of actin dynamics in live mammalian cells and microtubule dynamics during mitosis and cytokinesis in live plant cells.

  10. Interband electronic excitation-assisted atomic-scale restructuring of metal surfaces by nanosecond pulsed laser light (United States)

    Ernst; Charra; Douillard


    Interaction of high-power laser light with materials often causes irreversible damage of the near-surface region. It is shown that copper single-crystal surfaces can be patterned by laser light. Irradiation with green light produced adatoms and vacancies, which self-organized into nanoscale pyramids. This restructuring can be removed by annealing. In contrast to green light, infrared laser irradiation at equivalent absorbed energy density did not produce any structural change. This, for metallic systems, unforeseen spectral difference in laser light action points to a concerted process as the source for structural modification, which involves long-lived primary excitation of localized d-electrons through interband transition together with phonon excitation.

  11. Resonance radiation and high excitation of neutrals in plasma-gas interactions

    Energy Technology Data Exchange (ETDEWEB)

    Litnovsky, A.M. E-mail:; Khripunov, B.I.; Sholin, G.V.; Petrov, V.B.; Shapkin, V.V.; Antonov, N.V


    Experimental investigation of plasma-gas interaction has been performed in LENTA linear facility in order to model processes expected to occur in the divertor of a fusion tokamak reactor. Steady-state helium plasma with density {approx}(0.2-3)x10{sup 13} cm{sup -3} generated by beam-plasma discharge flowed into the region with high neutral pressure, interacted with neutral helium there and then reached the target plate. An intensive volume recombination and significant decrease in plasma pressure have been observed while the plasma stream interacted with gas target. Electron temperature fell below 1 eV. These processes were accompanied by an intensive emission from highly excited helium atoms and this radiation became even higher with increase in neutral pressure. Microwave emission absorption at high (P{sub gas}=20 mTorr) neutral pressures in the gas target was detected. A model of plasma-gas transition layer was developed to provide physics understanding of these phenomena. Resonance radiation and stimulated radiative recombination play an important role in this model.

  12. Generation and use of high power 213 nm and 266 nm laser radiation and tunable 210-400 nm laser radiation with BBO crystal matrix array (United States)

    Gruen, Dieter M.


    A 213 nm laser beam is capable of single photon ablative photodecomposition for the removal of a polymer or biological material substrate. Breaking the molecular bonds and displacing the molecules away from the substrate in a very short time period results in most of the laser photon energy being carried away by the displaced molecules, thus minimizing thermal damage to the substrate. The incident laser beam may be unfocussed and is preferably produced by quintupling the 1064 nm radiation from a Nd:YAG solid state laser, i.e., at 213 nm. In one application, the 213 nm laser beam is expanded in cross section and directed through a plurality of small beta barium borate (BBO) crystals for increasing the energy per photon of the laser radiation directed onto the substrate. The BBO crystals are arranged in a crystal matrix array to provide a large laser beam transmission area capable of accommodating high energy laser radiation without damaging the BBO crystals. The BBO crystal matrix array may also be used with 266 nm laser radiation for carrying out single or multi photon ablative photodecomposition. The BBO crystal matrix array may also be used in an optical parametric oscillator mode to generate high power tunable laser radiation in the range of 210-400 nm.

  13. Absorption and emission dynamics in concentrated optical ensembles under laser excitation (United States)

    Smirnov, V. A.; Ermolaeva, G. M.; Shilov, V. B.


    A new theoretical model describing the emission and absorption dynamics in an ensemble of molecules under intense coherent pulsed pumping is developed on the basis of the concepts of cooperative light-induced luminescence (CLIL). The CLIL development is described within the framework of formalism of the system density matrix in the space of photon wave functions. It is shown that the fast growth of CLIL relates to the development of coherent states of the quantum field in the area of efficient cooperative interactions of molecules (coherence volume). A system of equations for the calculation of CLIL energy, population of excited states, and optical absorption of the system in dependence on the laser pump energy density is solved. The theoretical results obtained are in good agreement with the experimental data.

  14. Conformal scanning laser Doppler vibrometer measurement of tenor steelpan response to impulse excitation. (United States)

    Ryan, Teresa; O'Malley, Patrick; Glean, Aldo; Vignola, Joseph; Judge, John


    A conformal scanning laser Doppler vibrometer system is used in conjunction with a mechanical pannist to measure the surface normal vibration of the entire playing surface of a C-lead tenor steelpan. The mechanical pannist is a device designed to deliver controlled, repeatable strikes that mimic a mallet during authentic use. A description of the measurement system is followed by select examples of behavior common to the results from three different excitation notes. A summary of observed response shapes and associated frequencies demonstrates the concerted placement of note overtones by the craftsmen who manufacture and tune the instruments. The measurements provide a rich mechanical snapshot of the complex motion that generates the distinctive sound of a steelpan.

  15. RILIS laser room HD

    CERN Multimedia


    Footage of the RILIS laser room at ISOLDE. The Resonance Ionization Laser Ion Source (RILIS) is a chemically selective ion source which relies on resonant excitation of atomic transitions using tunable laser radiation. This video shows you the laser table with the different lenses and optics as well as an overview of the RILIS laser setup. It also shows laser light with different colors and operation by the RILIS laser experts. The last part of the video shows you the laser path from the RILIS laser room into the ISOLDE GPS separator room where it enters the GPS separator magnet.

  16. RILIS laser room

    CERN Multimedia


    Footage of the RILIS laser room at ISOLDE. The Resonance Ionization Laser Ion Source (RILIS) is a chemically selective ion source which relies on resonant excitation of atomic transitions using tunable laser radiation. This video shows you the laser table with the different lenses and optics as well as an overview of the RILIS laser setup. It also shows laser light with different colors and operation by the RILIS laser experts. The last part of the video shows you the laser path from the RILIS laser room into the ISOLDE GPS separator room where it enters the GPS separator magnet.

  17. Simultaneous time-space resolved reflectivity and interferometric measurements of dielectrics excited with femtosecond laser pulses (United States)

    Garcia-Lechuga, M.; Haahr-Lillevang, L.; Siegel, J.; Balling, P.; Guizard, S.; Solis, J.


    Simultaneous time-and-space resolved reflectivity and interferometric measurements over a temporal span of 300 ps have been performed in fused silica and sapphire samples excited with 800 nm, 120 fs laser pulses at energies slightly and well above the ablation threshold. The experimental results have been simulated in the frame of a multiple-rate equation model including light propagation. The comparison of the temporal evolution of the reflectivity and the interferometric measurements at 400 nm clearly shows that the two techniques interrogate different material volumes during the course of the process. While the former is sensitive to the evolution of the plasma density in a very thin ablating layer at the surface, the second yields an averaged plasma density over a larger volume. It is shown that self-trapped excitons do not appreciably contribute to carrier relaxation in fused silica at fluences above the ablation threshold, most likely due to Coulomb screening effects at large excited carrier densities. For both materials, at fluences well above the ablation threshold, the maximum measured plasma reflectivity shows a saturation behavior consistent with a scattering rate proportional to the plasma density in this fluence regime. Moreover, for both materials and for pulse energies above the ablation threshold and delays in the few tens of picoseconds range, a simultaneous "low reflectivity" and "low transmission" behavior is observed. Although this behavior has been identified in the past as a signature of femtosecond laser-induced ablation, its origin is alternatively discussed in terms of the optical properties of a material undergoing strong isochoric heating, before having time to substantially expand or exchange energy with the surrounding media.

  18. Thermomechanical effect of pulse-periodic laser radiation on cartilaginous and eye tissues (United States)

    Baum, O. I.; Zheltov, G. I.; Omelchenko, A. I.; Romanov, G. S.; Romanov, O. G.; Sobol, E. N.


    This paper is devoted to theoretical and experimental studies into the thermomechanical action of laser radiation on biological tissues. The thermal stresses and strains developing in biological tissues under the effect of pulse-periodic laser radiation are theoretically modeled for a wide range of laser pulse durations. The models constructed allow one to calculate the magnitude of pressures developing in cartilaginous and eye tissues exposed to laser radiation and predict the evolution of cavitation phenomena occurring therein. The calculation results agree well with experimental data on the growth of pressure and deformations, as well as the dynamics of formation of gas bubbles, in the laser-affected tissues. Experiments on the effect of laser radiation on the trabecular region of the eye in minipigs demonstrated that there existed optimal laser irradiation regimens causing a substantial increase in the hydraulic permeability of the radiation-exposed tissue, which can be used to develop a novel glaucoma treatment method.

  19. Studies on linear, nonlinear optical and excited state dynamics of silicon nanoparticles prepared by picosecond laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Hamad, Syed; Nageswara Rao, S. V. S.; Pathak, A. P. [School of Physics, University of Hyderabad, Hyderabad 500046, Telangana (India); Krishna Podagatlapalli, G.; Mounika, R.; Venugopal Rao, S., E-mail:, E-mail: [Advanced Center of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046, Telangana (India)


    We report results from our studies on the fabrication and characterization of silicon (Si) nanoparticles (NPs) and nanostructures (NSs) achieved through the ablation of Si target in four different liquids using ∼2 picosecond (ps) pulses. The consequence of using different liquid media on the ablation of Si target was investigated by studying the surface morphology along with material composition of Si based NPs. The recorded mean sizes of these NPs were ∼9.5 nm, ∼37 nm, ∼45 nm and ∼42 nm obtained in acetone, water, dichloromethane (DCM) and chloroform, respectively. The generated NPs were characterized by selected area electron diffraction (SAED), high resolution transmission microscopy (HRTEM), Raman spectroscopic techniques and Photoluminescence (PL) studies. SAED, HRTEM and Raman spectroscopy data confirmed that the material composition was Si NPs in acetone, Si/SiO{sub 2} NPs in water, Si-C NPs in DCM and Si-C NPs in chloroform and all of them were confirmed to be polycrystalline in nature. Surface morphological information of the fabricated Si substrates was obtained using the field emission scanning electron microscopic (FESEM) technique. FESEM data revealed the formation of laser induced periodic surface structures (LIPSS) for the case of ablation in acetone and water while random NSs were observed for the case of ablation in DCM and chloroform. Femtosecond (fs) nonlinear optical properties and excited state dynamics of these colloidal Si NPs were investigated using the Z-scan and pump-probe techniques with ∼150 fs (100 MHz) and ∼70 fs (1 kHz) laser pulses, respectively. The fs pump-probe data obtained at 600 nm consisted of single and double exponential decays which were tentatively assigned to electron-electron collisional relaxation (<1 ps) and non-radiative transitions (>1 ps). Large third order optical nonlinearities (∼10{sup −14} e.s.u.) for these colloids have been estimated from Z-scan data at an excitation wavelength of 680 nm

  20. Study of electron kinetics in nitrogen plasma induced by CO2 laser radiation (United States)

    Nassef, O. Aied; Gamal, Yosr E. E.-D.


    In the present work, a numerical modeling is performed to study the electron kinetics in nitrogen plasma induced by CO2 laser radiation operating at wavelength 9.621 μm, and pulse duration of 60 ns corresponding to the measurements carried out by Camacho et al. (J Phys B At Mol Opt Phys 40:4573, 2007). In this experiment, the breakdown threshold intensity is determined for molecular nitrogen over a pressure range 301-760 torr. A previously developed electron cascade model (Evans and Gamal in J Phys D Appl Phys 13:1447, 1980) is modified and applied. This model is based on numerical solution of a time-dependent energy equation and a set of rate equations that describe the time variation of the formed excited states population. The effect of breakdown mechanism is decided through the calculations of the threshold intensity as a function of gas pressure considering the various physical processes that might take place during the interaction. The individual effect of each loss process on the electron energy distribution function and its parameters is studied. This study is performed at the lowest and highest values of the experimentally tested gas pressure range namely; 301 and 760 torr. The obtained results clarified the exact contribution of each loss process to the breakdown of nitrogen induced by CO2 laser radiation.

  1. Study of electron kinetics in nitrogen plasma induced by CO2 laser radiation (United States)

    Nassef, O. Aied; Gamal, Yosr E. E.-D.


    In the present work, a numerical modeling is performed to study the electron kinetics in nitrogen plasma induced by CO2 laser radiation operating at wavelength 9.621 μm, and pulse duration of 60 ns corresponding to the measurements carried out by Camacho et al. (J Phys B At Mol Opt Phys 40:4573, 2007). In this experiment, the breakdown threshold intensity is determined for molecular nitrogen over a pressure range 301-760 torr. A previously developed electron cascade model (Evans and Gamal in J Phys D Appl Phys 13:1447, 1980) is modified and applied. This model is based on numerical solution of a time-dependent energy equation and a set of rate equations that describe the time variation of the formed excited states population. The effect of breakdown mechanism is decided through the calculations of the threshold intensity as a function of gas pressure considering the various physical processes that might take place during the interaction. The individual effect of each loss process on the electron energy distribution function and its parameters is studied. This study is performed at the lowest and highest values of the experimentally tested gas pressure range namely; 301 and 760 torr. The obtained results clarified the exact contribution of each loss process to the breakdown of nitrogen induced by CO2 laser radiation.

  2. Photoacoustic study of curing time by UV laser radiation of a photoresin with different thickness

    Energy Technology Data Exchange (ETDEWEB)

    Pincel, P. Vieyra [UPIITA IPN, Avenida Instituto Politécnico Nacional, No. 2580, Col. Barrio la Laguna Ticomán, Delegación Gustavo A. Madero, C.P. 07340 México, D.F. (Mexico); Jiménez-Pérez, J.L., E-mail: [UPIITA IPN, Avenida Instituto Politécnico Nacional, No. 2580, Col. Barrio la Laguna Ticomán, Delegación Gustavo A. Madero, C.P. 07340 México, D.F. (Mexico); Cruz-Orea, A. [Departamento de Física, CINVESTAV-IPN, Av. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, C.P. 07360 México, D.F. (Mexico); Correa-Pacheco, Z.N. [Instituto Politécnico Nacional-Centro de Desarrollo de Productos Bióticos (CEPROBI). Carr. Yautepec–Jojutla, km 6. San Isidro, C.P. 62730 Yautepec, Morelos (Mexico); Rosas, J. Hernández [UPIITA IPN, Avenida Instituto Politécnico Nacional, No. 2580, Col. Barrio la Laguna Ticomán, Delegación Gustavo A. Madero, C.P. 07340 México, D.F. (Mexico)


    Highlights: • The curing of a resin in the presence of a UV laser radiation was studied. • Open photoacoustic cell technique was used to characterize the curing of the resin. • The curing of the resin as a function of time was studied. • A parabolic behavior of the resin thickness, as a function of time was observed. • UV–vis and FTIR spectroscopy were employed to characterize the resin. - Abstract: This paper deals with the study of the cure of a resin in the presence of a UV laser radiation used as the excitation source, operated at λ = 405 nm, with an output power of 20 mW. The open photoacoustic cell (OPC) technique was used to study the curing of the resins as a function of time. The curing characteristic time values were τ = 10.43, 20.99, 30.18, 45.84, 67.59 and 89.55 s for the resin thicknesses of 1000, 2000, 3000, 4000, 5000 and 6000 μm, respectively. A parabolic behavior of the resin thickness, as a function of the curing characteristic time, was obtained. UV–vis spectroscopy and infrared Fourier transform spectroscopy (FTIR) techniques were employed to characterize the resin in order to study the optical absorption and the chemical bonds, respectively. Our work has applications in the manufacture of 3D printing parts for applications, among others, in medicine.

  3. Photolysis of tryptophan with 337. 1 nm laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Borkman, R.F.; Hibbard, L.B.; Dillon, J.


    Aqueous solutions of L-tryptophan were photolyzed by exposure to 337.1 nm radiation from a pulsed nitrogen laser. These data were compared with results for the 290 nm conventional-source photolysis of tryptophan. The loss of Trp was observed to be first order for 290 nm photolysis but of mixed order for 337.1 nm photolysis. Five photolysis products including N-formylkynurenine, kynurenine, tryptamine and two unknown products were detected. The tryptophan-containing peptides N-acetyl-tryptophanamide (NATA) and tryptophylglycine (Trp-Gly) were also observed to photolyze upon 337.1 nm laser radiation demonstrating that this phenomenon is not restricted to free tryptophan monomer. A number of experiments were performed in an effort to determine the mechanism of photolysis at this wavelength. It is concluded that this photolysis results either from a very weak absorption tail extending to 337.1 nm in tryptophan itself or from a reaction involving an impurity sensitizer which absorbs the 337.1 nm radiation.

  4. Experimental comparison of laser energy losses in high-quality laser-oxygen cutting of low-carbon steel using radiation from fibre and CO2 lasers (United States)

    Golyshev, A. A.; Malikov, A. G.; Orishich, A. M.; Shulyat'ev, V. B.


    We report a comparative experimental study of laseroxygen cutting of low-carbon steel using a fibre laser with a wavelength of 1.07 μm and a CO2 laser with a wavelength of 10.6 μm at the sheet thickness of 3 - 16 mm. For the two lasers we have measured the dependence of the cutting speed on the radiation power and determined the cutting speed at which the surface roughness is minimal. The coefficient of laser radiation absorption in the laser cutting process is measured for these lasers at different values of the cutting speed and radiation power. It is found that the minimal roughness of the cut surface is reached at the absorbed laser energy per unit volume of the removed material, equal to 11 - 13 J mm-3; this value is the same for the two lasers and does not depend on the sheet thickness.

  5. Excitation of flare-induced waves in coronal loops and the effects of radiative cooling (United States)

    Provornikova, Elena; Ofman, Leon; Wang, Tongjiang


    EUV imaging observations from several space missions (SOHO/EIT, TRACE, and SDO/AIA) have revealed a presence of propagating intensity disturbances in solar coronal loops. These disturbances are typically interpreted as slow magnetoacoustic waves. However, recent spectroscopic observations with Hinode/EIS of active region loops revealed that the propagating intensity disturbances are associated with intermittent plasma upflows (or jets) at the footpoints which are presumably generated by magnetic reconnection. For this reason, whether these disturbances are waves or periodic flows is still being studied. This study is aimed at understanding the physical properties of observed disturbances by investigating the excitation of waves by hot plasma injections from below and the evolution of flows and wave propagation along the loop. We expand our previous studies based on isothermal 3D MHD models of an active region to a more realistic model that includes full energy equation accounting for the effects of radiative losses. Computations are initialized with an equilibrium state of a model active region using potential (dipole) magnetic field, gravitationally stratified density and temperature obtained from the polytropic equation of state. We model an impulsive injection of hot plasma into the steady plasma outflow along the loops of different temperatures, warm (∼1 MK) and hot (∼6 MK). The simulations show that hot jets launched at the coronal base excite slow magnetoacoustic waves that propagate to high altitudes along the loops, while the injected hot flows decelerate rapidly with heights. Our results support that propagating disturbances observed in EUV are mainly the wave features. We also find that the effect of radiative cooling on the damping of slow-mode waves in 1-6 MK coronal loops is small, in agreement with the previous conclusion based on 1D MHD models.

  6. Determination of the radiation axis position of an unstable-cavity laser (United States)

    Agroskin, V. Ya; Bravyi, B. G.; Vasil'ev, G. K.; Gur'ev, V. I.; Karel'skii, V. G.; Kashtanov, S. A.; Makarov, E. F.; Sotnichenko, S. A.; Chernyshev, Yu A.


    Propagation of an alignment laser beam through an unstable cavity laser is numerically simulated. It is shown that the axis of the expanded beam coincides with that of the fundamental laser radiation within an accuracy of no less than 1'' even under cavity misalignment of up to 30''. Experiments on determining the position of the radiation axis of a high-power pulsed unstable cavity chemical laser and various cavity misalignments confirm the calculation results.


    Directory of Open Access Journals (Sweden)

    I. A. Guseva


    Full Text Available Background: Laser fluorescence spectroscopy (LFS is widely used in various medical areas, oncology being the most known of them. In general, the LFS is used for in vivo diagnostics of tumors. Recent studies have shown that this method could be used for diagnostics of local inflammation, induced by thermal or mechanical injury. It is of interest if LFS could be used for assessment of soft biological tissue injury caused by radiation exposure. Aim: To study fluorescence of an exogenous photosensitizer and its changes over time in the radiation injury area by LFS method in vivo. Materials and methods: The experiment was done in 12 outbred SHK mice whose right hind limbs were irradiated using a gamma-therapy device ROKUS-AM (source, 60Co, at dose of 15 Gy. Before irradiation, the photosensitizer Photosens was administered to all animals intraperitoneally at dose of 2.5 mg/kg. For 21 days fluorescence was assessed in vivo with a laser diagnostic system LAKK-M in the “fluorescence” operation mode, with an excitation wavelength of 635 nm. At days 7 and 21, tissue samples from the irradiated areas of the model animals were studied histologically and differential blood cell counts were assessed simultaneously. Results: The LFS method showed an increase in the accumulation of the photosensitizer in the affected area, compared to an intact contralateral area, with higher signal intensity from the irradiated limb. The changes in the fluorescence signal from the affected over time had two characteristic peaks at days 3 and 14, probably reflecting the stage of local radiation injury. Conclusion: The use of LFS with an exogenous photosensitizer has a potential for a personalized assessment of radiation reactions in radiology.


    NARCIS (Netherlands)

    Recent collision experiments are reviewed in which one-electron transfer between laser excited target atoms and (highly charged) keV-ions has been studied. Especially results showing a dependence of the charge exchange on the initial target orbital alignment are discussed. The question to what

  9. Design and construction of prototype transversely excited atmospheric (TEA nitrogen laser energized by a high voltage electrical discharge

    Directory of Open Access Journals (Sweden)

    Mukhtar Hussain


    Full Text Available The present study reports design and construction, of a prototype of Transversely Excited Atmospheric (TEA nitrogen laser, and a high voltage power supply to excite N2 gas in air, while air is used as an active lasing medium. A Blumlein line discharge circuit is used for operation of this laser. The high voltage is generated by a fly back transformer based power supply varying from 10 kV to 20 kV. The wavelength (337.1 nm of TEA nitrogen laser is measured employing a standard commercial spectrometer and the laser output energy of 300 μJ is measured from the constructed system. Different parameters such as beam profile, laser output spectrum, laser efficiency, and variation of E/P (Electrical field/Pressure value with respect to input voltage and electrodes separations are studied in order to optimize the overall operational efficiency of present nitrogen laser. The analysis of the high voltage prototype appeared in this designed source has also been made and described in this paper.

  10. Laser-induced fluorescence with an OPO system. Part II: direct determination of lead content in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF). (United States)

    Le Bihan, A; Lijour, Y; Giamarchi, P; Burel-Deschamps, L; Stephan, L


    Fluorescence was induced by coupling a laser with an optical parametric oscillator (OPO) to develop an analytical method for the direct determination of lead content, at ultra-trace level, in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF). The optimization of atomization conditions, laser pulse energy, and mainly temporal parameters allowed us to reach a 3 fg detection limit (0.3 ng L(-1)) despite the low repetition rate of the device. The expected error on predicted concentrations of lead, at trace levels, in seawater was below 15%.

  11. Investigation of temperature feedback signal parameters during neoplasms treatment by diode laser radiation (United States)

    Belikov, Andrey V.; Gelfond, Mark L.; Shatilova, Ksenia V.; Semyashkina, Yulia V.


    Dynamics of temperature signal in operation area and laser power at nevus, papilloma, and keratoma in vivo removal by a 980+/-10 nm diode laser with "blackened" tip operating in continuous (CW) mode and with temperature feedback (APC) mode are presented. Feedback allows maintaining temperature in the area of laser treatment at a preset level by regulating power of diode laser radiation (automatic power control). Temperature in the area of laser treatment was controlled by measuring the amplitude of thermal radiation, which occurs when tissue is heated by laser radiation. Removal of neoplasm was carried out in CW mode with laser radiation average power of 12.5+/-0.5 W; mean temperature in the area of laser treatment was 900+/-10°C for nevus, 800+/-15°C for papilloma, and 850+/-20°C for keratoma. The same laser radiation maximal power (12.5 W) and targeted temperature (900°C) were set for nevus removal in APC mode. The results of investigation are real time oscillograms of the laser power and temperature in the area of laser treatment at neoplasms removal in two described above modes. Simultaneously with the measurement of laser power and the temperature in the area of laser treatment video recording of surgeon manipulations was carried out. We discuss the correlation between the power of the laser radiation, the temperature in the area of laser treatment and consistency of surgeon manipulation. It is shown that the method of removal (excision with or without traction, scanning) influences the temperature in the area of laser treatment. It was found, that at removal of nevus with temperature feedback (APC) mode to achieve comparable with CW mode temperature in the area of laser treatment (900+/-10°C) 20-50% less laser power is required. Consequently, removing these neoplasms in temperature feedback mode can be less traumatic than the removal in CW mode.

  12. High Energy Ion Acceleration by Extreme Laser Radiation Pressure (United States)


    AFRL-AFOSR-UK-TR-2017-0015 High energy ion acceleration by extreme laser radiation pressure Paul McKenna UNIVERSITY OF STRATHCLYDE VIZ ROYAL COLLEGE...MM-YYYY)   14-03-2017 2. REPORT TYPE  Final 3. DATES COVERED (From - To)  01 May 2013 to 31 Dec 2016 4. TITLE AND SUBTITLE High energy ion acceleration...Prescribed by ANSI Std. Z39.18 Page 1 of 1FORM SF 298 3/15/2017 1 HIGH ENERGY ION ACCELERATION BY

  13. Radiation excited by a charged-particle bunch on a planar periodic wire structure

    Directory of Open Access Journals (Sweden)

    Andrey V. Tyukhtin


    Full Text Available The electromagnetic field of a bunch moving in the presence of a plane grid composed of thin parallel wires is considered by using the averaged boundary conditions method. Two different cases of motion are examined. In the first one, the bunch moves at a constant distance from the grid orthogonally to the wires. The excited surface wave is presented in the form of a spectral integral for a thin bunch with an arbitrary longitudinal profile. The wave propagates along the wires and does not decay with distance (if dissipation is negligible. Energy losses of the bunch over a unit path are obtained. In the second case, the bunch orthogonally crosses the wire grid. The volume and surface waves are separately analyzed. Properties of the spectral angular density of energy of volume radiation in the far-field zone are described. The energy losses due to the volume and surface radiation are determined. It is demonstrated that the structure of the surface waves in both cases allows determination of the length of the bunch.

  14. Electron beam excitation of coherent sub-terahertz radiation in periodic structures manufactured by 3D printing (United States)

    Phipps, A. R.; MacLachlan, A. J.; Robertson, C. W.; Zhang, L.; Konoplev, I. V.; Cross, A. W.; Phelps, A. D. R.


    For the creation of novel coherent sub-THz sources excited by electron beams there is a requirement to manufacture intricate periodic structures to produce and radiate electromagnetic fields. The specification and the measured performance is reported of a periodic structure constructed by additive manufacturing and used successfully in an electron beam driven sub-THz radiation source. Additive manufacturing, or ;3D printing;, is promising to be quick and cost-effective for prototyping these periodic structures.

  15. Laser-induced precession of magnetization in ferrimagnetic GdFe thin films with low power excitation

    Directory of Open Access Journals (Sweden)

    K. Nishibayashi


    Full Text Available We have investigated thermal effects on the dynamics of laser-induced precession of magnetization in ferrimagnetic GdFe thin films under low-excitation conditions (6-60 μJ/cm2. An increase in quasi-equilibrium temperature by laser heating causes a shift in precession frequency, which is explained analytically by the alteration of the magnetic anisotropy field by 2.2 [Oe] at a pulse fluence of 1 μJ/cm2. We have also demonstrated coherent control of the precession amplitude using a sequence of two laser pulses, each with a fluence of 18 μJ/cm2, and point out the importance of low-power excitation for precise control of the dynamic states.

  16. Relationship between sound radiation from sound-induced and force-excited vibration: Analysis using an infinite elastic plate model. (United States)

    Yairi, Motoki; Sakagami, Kimihiro; Nishibara, Kosuke; Okuzono, Takeshi


    Although sound radiation from sound-induced vibration and from force-excited vibration of solid structures are similar phenomena in terms of radiating from vibrating structures, the general relationship between them has not been explicitly studied to date. In particular, airborne sound transmission through walls and sound radiation from structurally vibrating surfaces in buildings are treated as different issues in architectural acoustics. In this paper, a fundamental relationship is elucidated through the use of a simple model. The transmission coefficient for random-incidence sound and the radiated sound power under point force excitation of an infinite elastic plate are both analyzed. Exact and approximate solutions are derived for the two problems, and the relationship between them is theoretically discussed. A conversion function that relates the transmission coefficient and radiated sound power is obtained in a simple closed form through the approximate solutions. The exact solutions are also related by the same conversion function. It is composed of the specific impedance and the wavenumber, and is independent of any elastic plate parameters. The sound radiation due to random-incidence sound and point force excitation are similar phenomena, and the only difference is the gradient of those characteristics with respect to the frequency.

  17. Emission of strong Terahertz pulses from laser wakefields in weakly coupled plasma

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Divya, E-mail: [PWAPA Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110 016 (India); Department of Physics & Electronics, Rajdhani College, University of Delhi, Raja Garden, Ring Road, New Delhi 110015 (India); Malik, Hitendra K. [PWAPA Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110 016 (India)


    The present paper discusses the laser plasma interaction for the wakefield excitation and the role of external magnetic field for the emission of Terahertz radiation in a collisional plasma. Flat top lasers are shown to be more appropriate than the conventional Gaussian lasers for the effective excitation of wakefields and hence, the generation of strong Terahertz radiation through the transverse component of wakefield.

  18. High resolution laser beam induced current images under trichromatic laser radiation: approximation to the solar irradiation. (United States)

    Navas, F J; Alcántara, R; Fernández-Lorenzo, C; Martín-Calleja, J


    A laser beam induced current (LBIC) map of a photoactive surface is a very useful tool when it is necessary to study the spatial variability of properties such as photoconverter efficiency or factors connected with the recombination of carriers. Obtaining high spatial resolution LBIC maps involves irradiating the photoactive surface with a photonic beam with Gaussian power distribution and with a low dispersion coefficient. Laser emission fulfils these characteristics, but against it is the fact that it is highly monochromatic and therefore has a spectral distribution different to solar emissions. This work presents an instrumental system and procedure to obtain high spatial resolution LBIC maps in conditions approximating solar irradiation. The methodology developed consists of a trichromatic irradiation system based on three sources of laser excitation with emission in the red, green, and blue zones of the electromagnetic spectrum. The relative irradiation powers are determined by either solar spectrum distribution or Planck's emission formula which provides information approximate to the behavior of the system if it were under solar irradiation. In turn, an algorithm and a procedure have been developed to be able to form images based on the scans performed by the three lasers, providing information about the photoconverter efficiency of photovoltaic devices under the irradiation conditions used. This system has been checked with three photosensitive devices based on three different technologies: a commercial silicon photodiode, a commercial photoresistor, and a dye-sensitized solar cell. These devices make it possible to check how the superficial quantum efficiency has areas dependent upon the excitation wavelength while it has been possible to measure global incident photon-to-current efficiency values approximating those that would be obtained under irradiation conditions with sunlight.


    Energy Technology Data Exchange (ETDEWEB)

    Murray, Claire E.; Lindner, Robert R.; Stanimirović, Snežana; Pingel, Nickolas M.; Lawrence, Allen; Babler, Brian L. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Goss, W. M.; Jencson, Jacob [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville, Socorro, NM 87801 (United States); Heiles, Carl [Radio Astronomy Laboratory, UC Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States); Dickey, John [University of Tasmania, School of Maths and Physics, Private Bag 37, Hobart, TAS 7001 (Australia); Hennebelle, Patrick, E-mail: [Laboratoire AIM, Paris-Saclay, CEA/IRFU/SAp—CNRS—Université Paris Diderot, F-91191 Gif-sur-Yvette Cedex (France)


    We use the Karl G. Jansky Very Large Array to conduct a high-sensitivity survey of neutral hydrogen (H I) absorption in the Milky Way. In combination with corresponding H I emission spectra obtained mostly with the Arecibo Observatory, we detect a widespread warm neutral medium component with excitation temperature 〈T{sub s}〉=7200{sub −1200}{sup +1800} K (68% confidence). This temperature lies above theoretical predictions based on collisional excitation alone, implying that Lyα scattering, the most probable additional source of excitation, is more important in the interstellar medium (ISM) than previously assumed. Our results demonstrate that H I absorption can be used to constrain the Lyα radiation field, a critical quantity for studying the energy balance in the ISM and intergalactic medium yet notoriously difficult to model because of its complicated radiative transfer, in and around galaxies nearby and at high redshift.

  20. Dynamic-Stark-effect-induced coherent mixture of virtual paths in laser-dressed helium: energetic electron impact excitation (United States)

    Agueny, Hicham; Makhoute, Abdelkader; Dubois, Alain


    We theoretically investigate quantum virtual path interference caused by the dynamic Stark effect in bound-bound electronic transitions. The effect is studied in an intermediate resonant region and in connection with the energetic electron impact excitation of a helium atom embedded in a weak low-frequency laser field. The process under investigation is dealt with via a Born-Floquet approach. Numerical calculations show a resonant feature in laser-assisted cross sections. The latter is found to be sensitive to the intensity of the laser field dressing. We show that this feature is a signature of quantum beats which result from the coherent mixture of different quantum virtual pathways, and that excitation may follow in order to end up with a common final channel. This mixture arises from the dynamic Stark effect, which produces a set of avoided crossings in laser-dressed states. The effect allows one to coherently control quantum virtual path interference by varying the intensity of the laser field dressing. Our findings suggest that the combination of an energetic electron and a weak laser field is a useful tool for the coherent control of nonadiabatic transitions in an intermediate resonant region.

  1. Organic semiconductor distributed feedback laser as excitation source in Raman spectroscopy using free-beam and fibre coupling (United States)

    Liu, Xin; Lebedkin, Sergei; Mappes, Timo; Köber, Sebastian; Koos, Christian; Kappes, Manfred; Lemmer, Uli


    Enabled by the broad spectral gain and the efficient energy conversion in the active material, organic semiconductor lasers are promising for spectroscopic applications and have been recently applied for high resolution absorption and transmission spectroscopy. Here, we present the application of organic semiconductor DFB laser (DFB-OSL) as excitation source in Raman spectroscopy. Utilizing an efficient small molecule blend of tris (8-hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-(dicyano-methylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM), our encapsulated DFB-OSL achieved a high slope efficiency of 7.6%. The organic lasers were tested in the inverted and upright Raman microscope setups, using free-beam and fibre coupling, respectively. In the free-beam configuration, the emission beam was guided directly into an inverted microscope. Employing a spectrally tunable DFBOSL as the excitation source, we measured the Raman spectra of sulfur and improved the Raman signals for a given optical filter configuration. In the fibre coupling configuration, the organic laser was coupled into a 50 μm multi-mode optical fibre with an efficiency of 70 %. We utilized a round-to-line fibre-bundle for an efficient collection and transfer of Raman light to a spectrograph, by keeping a sufficient spectral resolution. Raman tests were performed on cadmium sulfide and cyclohexane. Our novel fibre-coupled organic laser provides a modular laboratory Raman system.

  2. Laser excitation of 8-eV electronic states in Th{sup +}. A first pillar of the electronic bridge toward excitation of the Th-229 nucleus

    Energy Technology Data Exchange (ETDEWEB)

    Herrera-Sancho, Oscar-Andrey


    The possibility to realize a nuclear clock based on the optical magnetic dipole transition from the ground state to the low-energy isomeric state in the {sup 229}Th nucleus has motivated experiments and proposals toward highly accurate clocks with trapped ions and highly stable optical frequency standards with Th-doped solids. These systems hold great promise to open a field of research in the borderland between atomic and nuclear physics, which will enable highly sensitive tests of postulates from fundamental physics and also will allow us to coherently excite and control nuclear states, opening a wonderful and intriguing new field in physics. A major experimental obstacle that has to be overcome before any precision spectroscopy can be performed with this system is however the insufficient knowledge on the exact transition energy. The best experimental result so far is an indirect determination from {gamma}-spectroscopy with a relative uncertainty of about 6%. To facilitate the search for the nuclear transition within a wide uncertainty range around 8 eV, we investigate two-photon excitation in the dense electronic level structure of Th{sup +}, which enables the nuclear excitation via a resonantly enhanced inverse electronic bridge process. Experiments on one- and two-photon laser excitation of buffer gas cooled {sup 232}Th{sup +} ions in a radio-frequency ion trap are reported in this thesis. The strongest resonance line at 402 nm from the (6d{sup 2}7s)J=3/2 ground state to the (6d7s7p)J=5/2 state is driven as the first excitation step. Using nanosecond laser pulses in the 250-nm wavelength range for the second step of a two-photon excitation, we have observed seven previously unknown levels in the unexplored region of the electronic level structure around 8 eV. This investigation shows that the Th{sup +} ion seems to be well suited for the search of the isomer transition because both, theory and experimental results, agree on the density of strong transitions

  3. Nonsequential double ionization of helium in IR+XUV two-color laser fields II: collision-excitation ionization process (United States)

    Jin, Facheng; Chen, Jing; Yang, Yujun; Liu, Xiaojun; Yan, Zong-Chao; Wang, Bingbing


    We recently investigated the collision-ionization mechanism of the nonsequential double-ionization (NSDI) process in IR+XUV two-color laser fields [(2016) Phys. Rev. A 93 043417]. Here, we extend this work to study the collision-excitation-ionization (CEI) mechanism of the NSDI processes in the two-color laser fields with different laser conditions. It is found that the CEI mechanism makes a dominant contribution to the NSDI as the extreme ultraviolet (XUV) photon energy is smaller than the ionization threshold of the He+ ion, and the momentum spectrum shows complex interference patterns and symmetrical structures. By channel analysis, we find that, as the energy carried by the recollision electron is not enough to excite the bound electron, the bound electron will absorb XUV photons during their collision; as a result, both forward and backward collisions make a comparable contribution to the NSDI processes. However, it is found that, as the energy carried by the recollision electron is large enough to excite the bound electron, the bound electron does not absorb any XUV photon and it is excited only by sharing the energy carried by the recollision electron, hence the forward collision plays a dominant role in the NSDI processes. Moreover, we find that the interference patterns of the NSDI spectra can be reconstructed by the spectra of two above-threshold ionization (ATI) processes, which may be used to analyze the structure of the two separate ATI spectra by NSDI processes.

  4. Beam-excited whistler waves at oblique propagation with relation to STEREO radiation belt observations

    Directory of Open Access Journals (Sweden)

    K. Sauer


    Full Text Available Isotropic electron beams are considered to explain the excitation of whistler waves which have been observed by the STEREO satellite in the Earth's radiation belt. Aside from their large amplitudes (~240 mV/m, another main signature is the strongly inclined propagation direction relative to the ambient magnetic field. Electron temperature anisotropy with Te⊥>Te||, which preferentially generates parallel propagating whistler waves, can be excluded as a free energy source. The instability arises due to the interaction of the Doppler-shifted cyclotron mode ω=−Ωe+kVbcosθ with the whistler mode in the wave number range of kc/ωe≤1 (θ is the propagation angle with respect to the background magnetic field direction, ωe is the electron plasma frequency and Ωe the electron cyclotron frequency. Fluid and kinetic dispersion analysis have been used to calculate the growth rate of the beam-excited whistlers including the most important parameter dependencies. One is the beam velocity (Vb which, for instability, has to be larger than about 2VAe, where VAe is the electron Alfvén speed. With increasing VAe the propagation angle (θ of the fastest growing whistler waves shifts from θ~20° for Vb=2VAe to θ~80° for Vb=5VAe. The growth rate is reduced by finite electron temperatures and disappears if the electron plasma beta (βe exceeds βe~0.2. In addition, Gendrin modes (kc/ωe≈1 are analyzed to determine the conditions under which stationary nonlinear waves (whistler oscillitons can exist. The corresponding spatial wave profiles are calculated using the full nonlinear fluid approach. The results are compared with the STEREO satellite observations.

  5. Effects of excitation laser wavelength on Ly-{alpha} and He-{alpha} line emission from nitrogen plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Harilal, S. S.; Miloshevsky, G. V.; Sizyuk, T.; Hassanein, A. [Center for Materials Under Extreme Environment, School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)


    Laser-produced nitrogen plasmas emitting radiation at 2.48 nm (Ly-{alpha}) and 2.88 nm (He-{alpha}) are considered potential efficient sources for water-window (WW) microscopy. The atomic and optical properties of nitrogen plasma and influence of the laser wavelength on the line emission in the WW range are investigated. It is found that the optimal temperatures for maximum emission from Ly-{alpha} and He-{alpha} spectral lines are 40-60 eV and 80-100 eV, respectively. The WW line emission and the conversion efficiency (CE) are estimated for three distinct Nd:YAG laser wavelengths (1064 nm, 532 nm, and 266 nm). The calculated CEs are compared with experimentally observed CE values. It is found that 1064 nm wavelength provides the highest CE from laser to Ly-{alpha} and He-{alpha} radiation.

  6. Effects of excitation laser wavelength on Ly-α and He-α line emission from nitrogen plasmas (United States)

    Harilal, S. S.; Miloshevsky, G. V.; Sizyuk, T.; Hassanein, A.


    Laser-produced nitrogen plasmas emitting radiation at 2.48 nm (Ly-α) and 2.88 nm (He-α) are considered potential efficient sources for water-window (WW) microscopy. The atomic and optical properties of nitrogen plasma and influence of the laser wavelength on the line emission in the WW range are investigated. It is found that the optimal temperatures for maximum emission from Ly-α and He-α spectral lines are 40-60 eV and 80-100 eV, respectively. The WW line emission and the conversion efficiency (CE) are estimated for three distinct Nd:YAG laser wavelengths (1064 nm, 532 nm, and 266 nm). The calculated CEs are compared with experimentally observed CE values. It is found that 1064 nm wavelength provides the highest CE from laser to Ly-α and He-α radiation.

  7. Optimal Spectral Regions For Laser Excited Fluorescence Diagnostics For Point Of Care Application (United States)

    Vaitkuviene, A.; Gėgžna, V.; Varanius, D.; Vaitkus, J.


    The tissue fluorescence gives the response of light emitting molecule signature, and characterizes the cell composition and peculiarities of metabolism. Both are useful for the biomedical diagnostics, as reported in previous our and others works. The present work demonstrates the results of application of laser excited autofluorescence for diagnostics of pathology in genital tissues, and the feasibility for the bedside at "point of care—off lab" application. A portable device using the USB spectrophotometer, micro laser (355 nm Nd:YAG, 0,5 ns pulse, repetition rate 10 kHz, output power 15 mW), three channel optical fiber and computer with diagnostic program was designed and ready for clinical trial to be used for cytology and biopsy specimen on site diagnostics, and for the endoscopy/puncture procedures. The biopsy and cytology samples, as well as intervertebral disc specimen were evaluated by pathology experts and the fluorescence spectra were investigated in the fresh and preserved specimens. The spectra were recorded in the spectral range 350-900 nm. At the initial stage the Gaussian components of spectra were found and the Mann-Whitney test was used for the groups' differentiation and the spectral regions for optimal diagnostics purpose were found. Then a formal dividing of spectra in the components or the definite width bands, where the main difference of the different group spectra was observed, was used to compare these groups. The ROC analysis based diagnostic algorithms were created for medical prognosis. The positive prognostic values and negative prediction values were determined for cervical Liquid PAP smear supernatant sediment diagnosis of being Cervicitis and Norma versus CIN2+. In a case of intervertebral disc the analysis allows to get the additional information about the disc degeneration status. All these results demonstrated an efficiency of the proposed procedure and the designed device could be tested at the point-of-care site or for

  8. New method to measure the angular antispring effect in a Fabry–Perot cavity with remote excitation using radiation pressure

    Energy Technology Data Exchange (ETDEWEB)

    Nagano, Koji, E-mail: [Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa, Chiba 277-8582 (Japan); Enomoto, Yutaro; Nakano, Masayuki [Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa, Chiba 277-8582 (Japan); Furusawa, Akira [Department of Applied Physics, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Kawamura, Seiji [Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa, Chiba 277-8582 (Japan)


    In experiments with Fabry–Perot cavities consisting of suspended mirrors, an angular antispring effect on the mirror of the cavity is caused by radiation pressure from resonant light in the cavity. A new method was invented to measure the effect precisely with remote excitation on the mirror using the radiation pressure. This method was found to be available for the suspended 23 mg mirror and improved the measurement accuracy by a factor of two, compared with the previous method. This result leads to stable control systems to eliminate the angular instability of the mirror caused by the effect. - Highlights: • A method to measure an angular antispring effect on a suspended mirror was proposed. • Remote excitation on the mirror with radiation pressure of resonant light is used. • This method provides better measurement accuracy compared with the previous method.

  9. INTERACTION OF LASER RADIATION WITH MATTER: Investigation of the interaction of laser radiation with composite materials by infrared spectroscopy methods (United States)

    Eremin, V. I.; Kovalenko, I. P.; Levashenko, G. I.; Mazaev, N. V.; Sokol'nikov, A. S.; Shuralev, S. L.


    A description is given of the method and apparatus for determination of the effective temperature and composition of a jet of products of the interaction of laser radiation with a glass-fiber-reinforced plastic and an organic plastic. Measurements are also possible of the temperature and emissivity of a target when it is exposed in atmospheric air to cw CO2 laser radiation with a flux density of 3 × 102 — 103 W/cm2. The products of damage to the glass-fiber-reinforced plastic consisted of particles of metal oxides with a diameter d32 = 2.3-3.5 μm and a volume concentration Cv = (0.06-0.25) × 10 - 4, and of molecular gases CO2, H2O, and HCl; the damage products of the organic plastic were conglomerates of soot particles with the diameter d32 = 1-1.8 μm and a volume concentration Cv = (0.4-0.9) × 10 - 4, and the same molecular gases. The target emissivity increased with time and reached 0.8-0.9.

  10. Temporal structure of X-ray radiation pulses of picosecond laser plasma

    Energy Technology Data Exchange (ETDEWEB)

    Belyaev, V S; Kovkov, D V; Matafonov, A P; Karabadzhak, G F; Raikunov, G G [Central Research Institute of Machine Building, Korolev, Moscow region (Russian Federation); Faenov, A Ya; Pikuz, S A; Skobelev, I Yu; Pikuz, T A; Fokin, D A; Fortov, V E [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation); Ignat' ev, G N; Kapitanov, S V; Krapiva, P S; Korotkov, K E [All-Russian Institute of Automatics, Moscow (Russian Federation)


    The shape of the X-ray pulse generated by picosecond laser plasma is experimentally studied. The unusual phenomenon was experimentally observed for the first time for targets made of moderate-heavy chemical elements, namely, the pulse of hard X-ray radiation generated by laser plasma at the laser radiation flux of ∼10{sup 18} W cm{sup -2} had a longer duration than the pulse of softer X-ray radiation. A simple kinetic model is suggested for explaining this fact. We have suggested a method for controlling the temporal shape of X-ray pulse emitted by laser plasma by varying the contrast of laser pulse. (interaction of laser radiation with matter)

  11. In vivo Diagnosis of Cervical Intraepithelial Neoplasia Using 337-nm- Excited Laser-Induced Fluorescence (United States)

    Ramanujam, N.; Mitchell, M. F.; Mahadevan, A.; Warren, S.; Thomsen, S.; Silva, E.; Richards-Kortum, R.


    Laser-induced fluorescence at 337-nm excitation was used in vivo to differentiate neoplastic [cervical intraepithelial neoplasia (CIN)], nonneoplastic abnormal (inflammation and human papilloma viral infection), and normal cervical tissues. A colposcope (low-magnification microscope used to view the cervix with reflected light) was used to identify 66 normal and 49 abnormal (5 inflammation, 21 human papilloma virus infection, and 23 CIN) sites on the cervix in 28 patients. These sites were then interrogated spectroscopically. A two-stage algorithm was developed to diagnose CIN. The first stage differentiated histologically abnormal tissues from colposcopically normal tissues with a sensitivity, specificity, and positive predictive value of 92%, 90%, and 88%, respectively. The second stage differentiated preneoplastic and neoplastic tissues from nonneoplastic abnormal tissues with a sensitivity, specificity, and positive predictive value of 87%, 73%, and 74%, respectively. Spectroscopic differences were consistent with a decrease in the absolute contribution of collagen fluorescence, an increase in the absolute contribution of oxyhemoglobin attenuation, and an increase in the relative contribution of reduced nicotinamide dinucleotide phosphate [NAD(P)H] fluorescence as tissue progresses from normal to abnormal in the same patient. These results suggest that in vivo fluorescence spectroscopy of the cervix can be used to diagnose CIN at colposcopy.

  12. Photoelectrolysis of water at high current density - Use of ultraviolet laser excitation (United States)

    Bocarsly, A. B.; Bolts, J. M.; Cummins, P. G.; Wrighton, M. S.


    The behavior of TiO2 and SrTiO3 photoanodes in cells for the photoelectrolysis of H2O has been investigated for high-intensity 351-,364-nm excitation from an Ar ion laser. Intensities up to 380 W/sq cm have been used. For TiO2 a small amount of surface decomposition is found after irradiation at high intensity, whereas SrTiO3 undergoes no detectable changes. Current-voltage properties for both electrodes are essentially independent of light intensity up to the level of 380 W/sq cm, and there is little if any change in quantum efficiency for electron flow. Photocurrent densities have been shown to exceed 5 A/sq cm for O2 evolution. Data show that the energy storage rate associated with the SrTiO3 photoelectrolysis can exceed 30 W/sq cm; this represents the highest demonstrated rate of sustained optical-to-chemical energy conversion.

  13. The influence of resonance IR laser radiation on magnetoabsorption in quantum wires (United States)

    Sinyavskii, E. P.; Karapetyan, S. A.; Kostyukevich, N. S.


    The coefficient of interband absorption of a weak electromagnetic wave by quantum wires in a transverse magnetic field and an intense laser radiation field is calculated. It is shown that, if the laser radiation frequency is equal either to the size quantization frequency (dimensional infrared resonance) or to a hybrid frequency (magnetoinfrared resonance), laser illumination can determine the shape of absorption oscillations. In particular, it is shown that the second magnetoabsorption peak is split into two peaks, the half-widths of which and the distance between which depend on the intensity of resonance laser radiation. The influence of the polarization of IR radiation on the interband absorption in quantum wires is discussed. The dynamics of the frequency dependence of the optical absorption coefficient with increasing intensity of resonance laser radiation is studied.

  14. Interaction of laser radiation with a low-density structured absorber

    Czech Academy of Sciences Publication Activity Database

    Rozanov, V. B.; Barishpol’tsev, D.V.; Vergunova, G.A.; Demchenko, N. N.; Ivanov, E.M.; Aristova, E.N.; Zmitrenko, N.V.; Limpouch, I.; Ullschmied, Jiří


    Roč. 122, č. 2 (2016), s. 256-276 ISSN 1063-7761 Institutional support: RVO:61389021 Keywords : laser radiation interaction * laser with low-density Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.196, year: 2016

  15. INTERACTION OF LASER RADIATION WITH MATTER: Influence of surface breakdown on the process of drilling metals with pulsed CO2 laser radiation (United States)

    Arutyunyan, R. V.; Baranov, V. Yu; Bobkov, I. V.; Bol'shov, Leonid A.; Dolgov, V. A.; Kanevskiĭ, M. F.; Malyuta, D. D.; Mezhevov, V. S.


    A report is given of the influence of low-threshold surface optical breakdown, occurring under the action of short (~ 5-μs) radiation pulses from a CO2 laser, on the process of the laser drilling of metals. Data are given on the difference between the interaction of radiation pulses having the same duration but differing in shape. A study was made of the influence of the pressure of the atmosphere surrounding a target on the results of laser drilling of metals. A theoretical explanation is given of the experimental results.

  16. Mobility of Electron in DNA Crystals by Laser Radiation (United States)

    Zhang, Kaixi; Zhao, Qingxun; Cui, Zhiyun; Zhang, Ping; Dong, Lifang


    The mobility of electrons in laser radiated DNA is closed to the energy transfer and energy migration of a biological molecule. Arrhenius has studied the conductivity of the electrons in a biological molecule. But his result is far from the experimental result and meanwhile the relation between some parameters in his theory and the micro-quantities in DNA is not very clear. In this paper, we propose a new phonon model of electron mobility in DNA and use Lippman-Schwinger equation and S-matrix theory to study the mobility of electrons in DNA crystal. The result is relatively close to the experiment result and some parameters in Arrhenius theory are explained in our work.

  17. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Plasma heating near a metal target by nanosecond pulses of the first, second, and fourth Nd-laser harmonics (United States)

    Bufetov, Igor'A.; Bufetova, G. A.; Kravtsov, S. B.; Fyodorov, V. B.; Fomin, V. K.


    Measurements were made of the electron temperature Te of a laser plasma formed on the surface of a metal target by the action of nanosecond pulses of wavelengths λ = 1060, 530, and 265 nm. The laser radiation intensity was I approx 109—1013 W cm-2. The electron temperature was determined from the emf of a double charge layer at the plasma boundary. Within the limits of the scatter of the experimental results, the plasma temperature was independent of the laser radiation wavelength (in the range 1060-265 nm). The dependence of this temperature on the radiation intensity obeyed approximately Te propto I1/3 throughout the investigated range.


    Directory of Open Access Journals (Sweden)

    O. N. Poklonskaya


    Full Text Available Results of measurements of Raman scattering at the room temperature in air in boron doped synthetic diamonds (five with boron concentrations 2·1017; 6·1017; 2·1018; 1,7·1019; 1·1020 cm–3 and one intentionally undoped are presented. The laser with wavelength 532 nm was used for Raman scattering excitation. Dependences of integral intensity and halfwidth of diamond Raman line with respect to the doping level are presented. In the geometrical optics approximation an expression for doped to undoped integral intensity ratio is obtained. Qualitative estimates of conductivity of the studied samples are conducted. The obtained results can be applied for mapping of near-surface laser radiation absorption coefficient of synthetic single crystal diamonds and for their quality control.

  19. Single-photon cesium Rydberg excitation spectroscopy using 3186-nm UV laser and room-temperature vapor cell (United States)

    Wang, Jieying; Bai, Jiandong; He, Jun; Wang, Junmin


    We demonstrate a single-photon Rydberg excitation spectroscopy of cesium (Cs) atoms in a room-temperature vapor cell. Cs atoms are excited directly from 6S1/2 ground state to nP3/2 (n = 70 - 100) Rydberg states with a 318.6 nm ultraviolet (UV) laser,and Rydberg excitation spectra are obtained by transmission enhancement of a probe beam resonant to Cs 6S1/2, F = 4 - 6P3/2, F' = 5 transition as partial population on F = 4 ground state are transferred to Rydberg state .Analysis reveals that the observed spectra are velocity-selective spectroscopy of Rydberg state, from which the amplitude and linewidth influenced by lasers'Rabi frequency have been investigated. Fitting to energies of Cs nP3/2 (n = 70 -100) states, the determined quantum defect is 3.56671(42). The demodulated spectra can also be employed as frequency references to stabilize the UV laser frequency to specific Cs Rydberg transition.

  20. Influence of He-Ne laser radiation of pacemaker on the frog's heart function (United States)

    Porozov, Yury B.; Brill, Gregory E.; Kiritchuk, Vyacheslav F.


    In experiments on isolated amphibian hearts changes in photoreactivity of pacemaker cells under the influence of He-Ne laser radiation in different phases of the heart cycle were studied. The specificity of heart photoreaction, peculiarities of relaxation period after laser light action and laser modification of hypodynamic depression development were revealed. Adaptation of pacemaker cells to the He-Ne laser exposure was observed.

  1. Multidisciplinary approaches to radiation-balanced lasers (MARBLE): a MURI program by AFOSR (Conference Presentation) (United States)

    Sheik-Bahae, Mansoor


    An overview of the diverse research activities under the newly funded MURI project by AFOSR will be presented. The main goal is to advance the science of radiation-balanced lasers, also known as athermal lasers, in order to mitigate the thermal degradation of the high-power laser beams. The MARBLE project involves researchers from four universities and spans research activities in rare-earth doped crystals and fibers to semiconductor disc lasers.

  2. Solid state laser employing diamond having color centers as a laser active material

    Energy Technology Data Exchange (ETDEWEB)

    Rand, S.C.; De Shazer, L.G.


    A laser is described comprising: resonant cavity means for supporting coherent radiation; a diamond containing color centers as a laser active material; means for exciting the color centers to emit coherent radiation; and optical path means for providing an exit path for the radiation from the resonant cavity means.

  3. The Effect of the Laser-Radiation Power on the Characteristics of the Raman Line for Diamond Single Crystals (United States)

    Gusakov, G. A.; Samtsov, M. P.; Voropay, E. S.


    The paper presents the results of the study of the effect exerted by exciting laser radiation on the Raman spectra of synthetic diamond single crystals plates (linear dimensions from 3 × 3 to 5 × 5 mm) having different impurity compositions. It has been found that an increase in laser radiation power from 70 to 480 mW (90-600 kW/cm2) leads to heating of the samples by a few tens of degrees, which results in shifting of the Raman line maxima by 0.5 cm-1 and in increased Raman line half-width up to 0.15 cm-1. As demonstrated by the spectral data, the heating temperature correlates with the optical density and geometry of the samples and also with the conditions of heat extraction from their surface. Based on the independent measurements of the crystal temperature at a certain distance from the excitation beam axis, it is shown that the variations of the characteristics of the principal Raman line are not determined by the local heating of the crystal studied under the effect of laser radiation. An analysis of the characteristics of the Stokes and anti-Stokes spectral components makes it possible to separate the temperature and impurity effects in the variations of the principal Raman line. Using diamond monocrystalline samples as an example, it has been revealed that the increased content of nitrogen as an impurity in the lattice from 3 up to 200 ppm leads to shifting of the Raman line maximum towards lower wave numbers by 0.08 cm-1 and to its broadening by 0.23 cm-1.

  4. Coherent and incoherent radiation from a channel-guided laser wakefield accelerator

    NARCIS (Netherlands)

    Khachatryan, A.G.; van Goor, F.A.; Boller, Klaus J.


    Coherent and incoherent electromagnetic radiation emitted from a channel-guided laser wakefield accelerator (LWFA) is calculated based on the Lienard–Wiechert potentials. It is found that at wavelengths longer than the bunch length, the radiation is coherent. The coherent radiation, which typically

  5. Transurethral coagulation for radiation-induced hemorrhagic cystitis using Greenlight™ potassium-titanyl-phosphate laser. (United States)

    Zhu, Jin; Xue, Boxin; Shan, Yuxi; Yang, Dongrong; Zang, Yachen


    The aim of this study was to to demonstrate the initial treatment outcomes of Greenlight™ potassium-titanyl-phosphate (KTP) laser on radiation-induced hemorrhagic cystitis. Hemorrhagic cystitis is a common complication of radiation therapy for pelvic tumors. From September 2004 to February 2011, 10 patients with radiation-induced intractable hemorrhagic cystitis underwent transurethral Greenlight KTP laser coagulation of the bladder. The power setting was limited to 20-30 W. Bleeding stopped in all cases after one session of laser treatment. Mean follow-up time was 17 months (6-36 months). All patients underwent cystoscopy 3 months postoperatively, and no bleeding or significant scar was found. Recurrence of significant bleeding was seen in one case 7 months post-operation, and was again cured by KTP laser. There were no complications from the procedures. Our experience suggests that transurethral coagulation using KTP laser is a safe and effective strategy for the treatment of hemorrhagic radiation cystitis.

  6. Diagnostics of the efficiency of surface plasmon-polariton excitation by quantum dots via polarization measurements of the output radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kukushkin, V. A., E-mail: [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation); Baidus, N. V. [Lobachevsky State University of Nizhni Novgorod (Russian Federation); Zdoroveishchev, A. V. [Lobachevsky State University of Nizhni Novgorod, Physicotechnical Research Institute (Russian Federation)


    It is demonstrated that the efficiency of surface plasmon-polariton excitation at a metal-semiconductor interface by active quantum dots can be determined from measurements of the polarization characteristics of the output radiation. Experimentally, the proposed diagnostic method is based on finding the ratio of the intensities of the output radiation with polarizations orthogonal and parallel to the nanoheterostructure plane for two different distances between the quantum-dot layer and the metal-semiconductor interface. These data are then used to obtain the unknown parameters in the proposed mathematical model which makes it possible to calculate the rate of surface plasmon-polariton excitation by active quantum dots. As a result, this rate can be determined without complicated expensive equipment for fast time-resolved measurements.

  7. Optical Communication among Oscillatory Reactions and Photo-Excitable Systems: UV and Visible Radiation Can Synchronize Artificial Neuron Models. (United States)

    Gentili, Pier Luigi; Giubila, Maria Sole; Germani, Raimondo; Romani, Aldo; Nicoziani, Andrea; Spalletti, Anna; Heron, B Mark


    Neuromorphic engineering promises to have a revolutionary impact in our societies. A strategy to develop artificial neurons (ANs) is to use oscillatory and excitable chemical systems. Herein, we use UV and visible radiation as both excitatory and inhibitory signals for the communication among oscillatory reactions, such as the Belousov-Zhabotinsky and the chemiluminescent Orban transformations, and photo-excitable photochromic and fluorescent species. We present the experimental results and the simulations regarding pairs of ANs communicating by either one or two optical signals, and triads of ANs arranged in both feed-forward and recurrent networks. We find that the ANs, powered chemically and/or by the energy of electromagnetic radiation, can give rise to the emergent properties of in-phase, out-of-phase, anti-phase synchronizations and phase-locking, dynamically mimicking the communication among real neurons. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Modelling of micromachining of human tooth enamel by erbium laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Belikov, A V; Skrypnik, A V; Shatilova, K V [St. Petersburg National Research University of Information Technologies, Mechanics and Optics, St. Petersburg (Russian Federation)


    We consider a 3D cellular model of human tooth enamel and a photomechanical cellular model of enamel ablation by erbium laser radiation, taking into account the structural peculiarities of enamel, energy distribution in the laser beam cross section and attenuation of laser energy in biological tissue. The surface area of the texture in enamel is calculated after its micromachining by erbium laser radiation. The influence of the surface area on the bond strength of enamel with dental filling materials is discussed. A good correlation between the computer simulation of the total work of adhesion and experimentally measured bond strength between the dental filling material and the tooth enamel after its micromachining by means of YAG : Er laser radiation is attained. (laser biophotonics)

  9. Recycling of laser and plasma radiation energy for enhancement of extreme ultraviolet sources for nanolithography (United States)

    Sizyuk, V.; Sizyuk, T.; Hassanein, A.; Johnson, K.


    We have developed comprehensive integrated models for detailed simulation of laser-produced plasma (LPP) and laser/target interaction, with potential recycling of the escaping laser and out-of-band plasma radiation. Recycling, i.e., returning the escaping laser and plasma radiation to the extreme ultraviolet (EUV) generation region using retroreflective mirrors, has the potential of increasing the EUV conversion efficiency (CE) by up to 60% according to our simulations. This would result in significantly reduced power consumption and/or increased EUV output. Based on our recently developed models, our High Energy Interaction with General Heterogeneous Target Systems (HEIGHTS) computer simulation package was upgraded for LPP devices to include various radiation recycling regimes and to estimate the potential CE enhancement. The upgraded HEIGHTS was used to study recycling of both laser and plasma-generated radiation and to predict possible gains in conversion efficiency compared to no-recycling LPP devices when using droplets of tin target. We considered three versions of the LPP system including a single CO2 laser, a single Nd:YAG laser, and a dual-pulse device combining both laser systems. The gains in generating EUV energy were predicted and compared for these systems. Overall, laser and radiation energy recycling showed the potential for significant enhancement in source efficiency of up to 60% for the dual-pulse system. Significantly higher CE gains might be possible with optimization of the pre-pulse and main pulse parameters and source size.

  10. Excitation and ionic fragmentation of gas-phase biomolecules using electrons and synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Souza, G G B de [Instituto de Quimica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21949-900 (Brazil); Coutinho, L H [Centro Universitario Estadual da Zona Oeste, Rio de Janeiro, RJ, 23070-200 (Brazil); Nunez, C [Instituto Nacional de Pesquisas da Amazonia, INPA, Manaus, AM, 69083-000 (Brazil); Bernini, R [Instituto de Quimica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21949-900 (Brazil); Castilho, R B [Instituto de Quimica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21949-900 (Brazil); Lago, A F [Laboratorio Nacional de Luz SIncrotron (LNLS), Box 6192, Campinas, SP, 13084-971 (Brazil)


    An experimental study of the electronic excitation and ionic dissociation of two important classes of biomolecules-natural products (biogenic volatile organic compounds, VOCs, and volatile components of essential oils) and DNA and RNA constituents (aminoacids and bases) is here exemplified with recent results on the fragmentation of thymine and isoprene as induced by synchrotron radiation and fast electrons. Fragmentation of the thymine molecule was seen to dramatically increase as the photon energy increased from 21 to 300 eV and 450 eV. At the highest photon energy, simply and doubly charged N and O atoms were observed. The parent ion (m/z = 126) could be observed at all photon energies. The fragmentation pattern observed in the 1.0 keV electron impact mass spectrum of thymine resembled more closely the fragmentation observed with 21 eV photons. In isoprene, the dominant fragments observed at 21 eV and 310 eV photon energy as well as in the 1.0 keV electron impact mass spectrum were C{sub 5}H{sub 7}{sup +}(m/z = 67), C{sub 4}H{sub 5}{sup +}(m/z = 53), C{sub 3}H{sub 3}{sup +}(m/z = 39) and C{sub 2}H{sub 3}{sup +}(m/z = 27). Previously unreported fragments, namely H{sup +}, C{sup +}, CH{sup +}, CH{sub 2}{sup +}, and CH{sub 3}{sup +} were observed at the high photon energies and at the electron impact mass spectrum.

  11. A radiative transfer model to treat infrared molecular excitation in cometary atmospheres (United States)

    Debout, V.; Bockelée-Morvan, D.; Zakharov, V.


    The exospheres of small Solar System bodies are now observed with high spatial resolution from space missions. Interpreting infrared spectra of cometary gases obtained with the VIRTIS experiment onboard the Rosetta cometary mission requires detailed modeling of infrared fluorescence emission in optically thick conditions. Efficient computing methods are required since numerous ro-vibrational lines excited by the Sun need to be considered. We propose a new model working in a 3-D environment to compute numerically the local incoming radiation. It uses a new algorithm using pre-defined directions of ray propagation and ray grids to reduce the CPU cost in time with respect to Monte Carlo methods and to treat correctly the sunlight direction. The model is applied to the ν3 bands of CO2 and H2O at 4.3 μ m and 2.7 μ m respectively, and to the CO ∨ (1 → 0) band at 4.7 μ m. The results are compared to the ones obtained by a 1-D algorithm which uses the Escape Probability (EP) method, and by a 3-D ;Coupled Escape Probability; (CEP) model, for different levels of optical thickness. Our results suggest that the total band flux may vary strongly with azimuth for optically thick cases whereas the azimuth average total band flux computed is close to the one obtained with EP. Our model globally predicts less intensity reduction from opacity than the CEP model of Gersch and A'Hearn (Gersch, A.M., A'Hearn, M.F. [2014]. Astrophys. J. 787, 36-56). An application of the model to the observation of CO2, CO and H2O bands in 67/P atmosphere with VIRTIS is presented to predict the evolution of band optical thickness along the mission.

  12. Pulsed infrared radiation excites cultured neonatal spiral and vestibular ganglion neurons by modulating mitochondrial calcium cycling. (United States)

    Lumbreras, Vicente; Bas, Esperanza; Gupta, Chhavi; Rajguru, Suhrud M


    Cochlear implants are currently the most effective solution for profound sensorineural hearing loss, and vestibular prostheses are under development to treat bilateral vestibulopathies. Electrical current spread in these neuroprostheses limits channel independence and, in some cases, may impair their performance. In comparison, optical stimuli that are spatially confined may result in a significant functional improvement. Pulsed infrared radiation (IR) has previously been shown to elicit responses in neurons. This study analyzes the response of neonatal rat spiral and vestibular ganglion neurons in vitro to IR (wavelength = 1,863 nm) using Ca(2+) imaging. Both types of neurons responded consistently with robust intracellular Ca(2+) ([Ca(2+)]i) transients that matched the low-frequency IR pulses applied (4 ms, 0.25-1 pps). Radiant exposures of ∼637 mJ/cm(2) resulted in continual neuronal activation. Temperature or [Ca(2+)] variations in the media did not alter the IR-evoked transients, ruling out extracellular Ca(2+) involvement or primary mediation by thermal effects on the plasma membrane. While blockage of Na(+), K(+), and Ca(2+) plasma membrane channels did not alter the IR-evoked response, blocking of mitochondrial Ca(2+) cycling with CGP-37157 or ruthenium red reversibly inhibited the IR-evoked [Ca(2+)]i transients. Additionally, the magnitude of the IR-evoked transients was dependent on ryanodine and cyclopiazonic acid-dependent Ca(2+) release. These results suggest that IR modulation of intracellular calcium cycling contributes to stimulation of spiral and vestibular ganglion neurons. As a whole, the results suggest selective excitation of neurons in the IR beam path and the potential of IR stimulation in future auditory and vestibular prostheses. Copyright © 2014 the American Physiological Society.

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

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


    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.

  14. Static diode pumped alkali lasers: Model calculations of the effects of heating, ionization, high electronic excitation and chemical reactions (United States)

    Barmashenko, B. D.; Rosenwaks, S.; Heaven, M. C.


    The effects of heating, ionization, high electronic excitation and chemical reactions on the operation of diode pumped alkali lasers (DPALs) with a static, non-flowing gain medium are calculated using a semi-analytical model. Unlike other models, assuming a three-level scheme of the laser and neglecting influence of the temperature on the lasing power, it takes into account the temperature rise and losses of neutral alkali atoms due to ionization and chemical reactions, resulting in decrease of the pump absorption and slope efficiency. Good agreement with measurements in a static DPAL [B.V. Zhdanov, J. Sell, R.J. Knize, Electron. Lett. 44 (2008) 582] is obtained. It is found that the ionization processes have a small effect on the laser operation, whereas the chemical reactions of alkali atoms with hydrocarbons strongly affect the lasing power.

  15. Delay of the excited state lasing of 1310 nm InAs/GaAs quantum dot lasers by facet coating (United States)

    Cao, Yu-Lian; Yang, Tao; Xu, Peng-Fei; Ji, Hai-Ming; Gu, Yong-Xian; Wang, Xiao-Dong; Wang, Qing; Ma, Wen-Quan; Chen, Liang-Hui


    In this letter, we present a facet coating design to delay the excited state (ES) lasing for 1310 nm InAs/GaAs quantum dot lasers. The key point of our design is to ensure that the mirror loss of ES is larger than that of the ground state by decreasing the reflectivity of the ES. In the facet coating design, the central wavelength is at 1480 nm, and the high- and low-index materials are Ta2O5 and SiO2, respectively. Compared with the traditional Si/SiO2 facet coating with a central wavelength of 1310 nm, we have found that with the optimal design the turning temperature of the ES lasing has been delayed from 90 to 100 °C for the laser diodes with cavity length of 1.2 mm. Furthermore, the characteristic temperature (T0) of the laser diodes is also improved.

  16. Area dependence of femtosecond laser-induced periodic surface structures for varying band gap materials after double pulse excitation

    Energy Technology Data Exchange (ETDEWEB)

    Höhm, S., E-mail: [Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Max-Born-Straße 2A, D-12489 Berlin (Germany); Rosenfeld, A. [Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Max-Born-Straße 2A, D-12489 Berlin (Germany); Krüger, J.; Bonse, J. [BAM Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 87, D-12205 Berlin (Germany)


    The formation of laser-induced periodic surface structures upon irradiation of titanium, silicon, and fused silica with multiple irradiation sequences consisting of parallel polarized Ti:sapphire femtosecond laser pulse pairs (pulse duration 50–150 fs, central wavelength ∼800 nm) is studied experimentally. The temporal delay between the individual near-equal energy fs-laser pulses was varied between 0 and 5 ps with a temporal resolution of better than 0.2 ps. The surface morphology of the irradiated surface areas is characterized by means of scanning electron microscopy (SEM). In all materials a decrease of the rippled surface area is observed for increasing delays. The characteristic delay decay scale is quantified and related to material dependent excitation and energy relaxation processes.

  17. Circular polarization of X-ray radiation emitted by longitudinally polarized electron impact excitation: Under a screened Coulomb interaction (United States)

    Chen, Zhan-Bin


    Longitudinally polarized electron impact excitation from the ground state 1s2 to the excited state 1s2l (l =s,p) levels of highly charged He-like Fe24+ ions in weakly coupled hot-dense plasmas is investigated using a fully relativistic distorted-wave method. The Debye-Hückel potential is used to describe the plasma screening. Benchmark results such as the total cross sections, the magnetic sublevels cross sections, and the circular polarizations of corresponding X-ray radiations are presented. For the excitation process, results show that the plasma screening has an effect in reducing both the total and magnetic sublevels cross sections. For the de-excitation process, it is found that while the plasma screening as a slightly effect on the circular polarizations of radiations for the 1 s 2 s 3S1 → 1 s21S0,1 s 2 p 3P2 → 1 s21S0 , and 1 s 2 p 1P1 → 1 s21S0 transition lines, it gives a substantial contribution for the same properties of the 1 s 2 p 3P1 → 1 s21S0 line.

  18. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Laser ablation plume dynamics in nanoparticle synthesis (United States)

    Osipov, V. V.; Platonov, V. V.; Lisenkov, V. V.


    The dynamics of the plume ejected from the surface of solid targets (YSZ, Nd:YAG and graphite) by a CO2 laser pulse with a duration of ~500 μs (at the 0.03 level), energy of 1.0-1.3 J and peak power of 6-7 kW have been studied using high-speed photography of the plume luminescence and shadow. The targets were used to produce nanopowders by laser evaporation. About 200 μs after termination of the pulse, shadowgraph images of the plumes above the YSZ and Nd:YAG targets showed dark straight tracks produced by large particles. The formation of large (~10 μm) particles is tentatively attributed to cracking of the solidified melt at the bottom of the ablation crater. This is supported by the fact that no large particles are ejected from graphite, which sublimes without melting. Further support to this hypothesis is provided by numerical 3D modelling of melt cooling in craters produced by laser pulses of different shapes.

  19. Comparison of the ablation ability of nucleus pulposus after 1,064 nm Nd:YAG laser and 980 nm diode laser radiation. (United States)

    Yin, Jian; Han, Zhengfeng; Guo, Baofeng; Guo, Han; Zhang, Tongtong; Zeng, Yanjun; Ren, Longxi


    To compare the ablation ability of nucleus pulposus after 1,064 nm Nd:YAG laser and 980 nm diode laser radiation. Goat spine specimen (GSS) was radiated using Nd:YAG laser and 980 nm diode laser and then divided into five groups based on the final energy--200, 400, 600, 800 and 1,000 J groups. The ablation quality of nucleus pulposus after radiation was recorded. The ablation quality of GSS was greater at higher radiation energies in both lasers. When compared at the same energy level, the ablation quality of GSS was greater in 980 nm diode laser than in 1,064 nm Nd:YAG laser. Statistical significance was observed in 200 and 400 J groups (P laser showed better ablation ability than 1,064 nm Nd:YAG laser.

  20. Laser-Bioplasma Interaction: Excitation and Suppression of the Brain Waves by the Multi-photon Pulsed-operated Fiber Lasers in the Ultraviolet Range of Frequencies (United States)

    Stefan, V. Alexander; IAPS-team Team


    The novel study of the laser excitation-suppression of the brain waves is proposed. It is based on the pulsed-operated multi-photon fiber-laser interaction with the brain parvalbumin (PV) neurons. The repetition frequency matches the low frequency brain waves (5-100 Hz); enabling the resonance-scanning of the wide range of the PV neurons (the generators of the brain wave activity). The tunable fiber laser frequencies are in the ultraviolet frequency range, thus enabling the monitoring of the PV neuron-DNA, within the 10s of milliseconds. In medicine, the method can be used as an ``instantaneous-on-off anesthetic.'' Supported by Nikola Tesla Labs, Stefan University.

  1. Mechanisms of graphene exfoliation under the action of femtosecond laser radiation in liquid nitrogen (United States)

    Khorkov, K. S.; Kochuev, D. A.; Ilin, V. A.; Chkalov, R. V.; Prokoshev, V. G.; Arakelian, S. M.


    The processes of graphene structures formation under the action of the femtosecond laser radiation on carbon samples in liquid nitrogen are discussed. Mechanisms of graphene sheets exfoliation are proposed depending on the power density of the laser radiation: in the first case, the separation occurs due to the volumetric expansion during heating the region occupied by nitrogen molecules; at a laser radiation energy exceeding the ablation threshold, the surface of graphite begins to breakdown in the region of the action, followed by separation into graphene layers.

  2. Analytical modeling of polarization transformation of laser radiation of various spectral ranges by birefringent structures (United States)

    Motrich, A. V.; Ushenko, O. G.


    The results of statistical dependence and correlation structures of two-dimensional Mueller matrix elements in various spectral regions of laser radiation by changes in the distribution of orientations of optical axes and birefringence of protein crystals. Namely, a two-wave ("red-blue") approach - layer of biological tissues irradiated by He-Ne laser (λ1 = 0,63μm ) and He-Cd laser (λ1 = 0,41μm )was used Conducted analysis of polarimetric sensitivity was made, a state of polarization points that contain volumetric structures of biological objects to spectral region of laser radiation was detected.

  3. Role of laser radiation in activating anodic dissolution under electrochemical machining of metals and alloys

    Directory of Open Access Journals (Sweden)

    Rakhimyanov Kharis


    Full Text Available The specific features of electrochemical dissolution of the 12X18H9T stainless steel, the OT-4 titanium alloy and the BK8 hard alloy in the sodium nitrate water solution exposed to 1.06 micrometer wavelength laser radiation were considered. It is found that depassivation of the anode surface is the main mechanism of laser activation in electrochemical dissolving of materials. It is established that the maximum efficiency of laser electrochemical machining is achieved at a pulse repetition frequency of 10 kHz laser radiation. It is connected with the photoactivation mechanism of electrolyte solution molecules, which increases their reaction capacity.

  4. ARTICLES: Physical laws governing the interaction of pulse-periodic CO2 laser radiation with metals (United States)

    Vedenov, A. A.; Gladush, G. G.; Drobyazko, S. V.; Pavlovich, Yu V.; Senatorov, Yu M.


    It is shown theoretically and experimentally that the efficiency of welding metals with a pulse-periodic CO2 laser beam of low duty ratio, at low velocities, can exceed that of welding with cw lasers and with electron beams. For the first time an investigation was made of the influence of the laser radiation parameters (energy and frequency) and of the welding velocity on the characteristics of the weld and on the shape of the weldpool. The influence of the laser radiation polarization on the efficiency of deep penetration was analyzed.

  5. Ultrafast Desorption by Impulsive Vibrational Excitation (DIVE). Applications in laser surgery, mass spectrometry and towards ultimate limits in biodiagnosis

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Ling


    The prospects for minimally invasive surgery, spatial imaging with mass spectrometry and rapid high throughput biodiagnosis require new means of tissue incision and biomolecule extraction with conserved molecular structure. Towards this aim, a laser ablation process is utilized in this dissertation, which is capable of performing precise tissue incision with minimal collateral damage and extracting intact biological entities with conserved biological functions. The method is based on the recently developed Picosecond Infrared Laser (PIRL) designed to excite selectively the water vibrational modes under the condition of ultrafast Desorption by Impulsive Vibrational Excitation (DIVE). The basic concept is that the selectively excited water molecules act as propellant to ablate whole biological complexes into the plume, faster than any thermal deleterious effect or fragmentation that would mask molecular identities.The PIRL ablation under DIVE condition is applied for the first time to six types of ocular tissues, rendering precise and minimally invasive incisions in a well-controlled and reproducible way. An eminent demonstration is the contact-free and applanation-free corneal trephination with the PIRL. Mass spectrometry and other analytical techniques show that great abundance of proteins with various molecular weights are extracted from the tissue by the PIRL ablation, and that fragmentation or other chemical alternation does not occur to the proteins in the ablation plume. With various microscope imaging and biochemical analysis methods, nano-scale single protein molecules, viruses and cells in the ablation plume are found to be morphologically and functionally identical to their corresponding controls. The PIRL ablation provides a new means to push the frontiers of laser surgery in ophthalmology and can be applied to resolve chemical activities in situ and in vivo. The most important finding is the conserved nature of the extracted biological entities

  6. Development of a fluorescence detection system using optical parametric oscillator (OPO) laser excitation for in vivo diagnosis. (United States)

    Song, J M; Jagannathan, R; Stokes, D L; Kasili, P M; Panjehpour, M; Phan, M N; Overholt, B F; DeNovo, R C; Pan, X; Lee, R J; Vo-Dinh, T


    In this work, the development and applications of a fluorescence detection system using optical parametric oscillator (OPO) laser excitation for in vivo disease diagnosis including oral carcinoma are described. The optical diagnosis system was based on an OPO laser for multi-wavelength excitation and time-resolved detection. The pulsed Nd-YAG-pumped OPO laser system (6 ns, 20 Hz) is compact and has a rapid, broad, and uniform tuning range. Time-gated detection of intensified charge-coupled device (ICCD) making use of external triggering was used to effectively eliminate the laser scattering and contribute to the highly sensitive in vivo measurements. Artificial tissue-simulating phantoms consisting of polystyrene microspheres and tissue fluorophores were tested to optimize the gating parameters. 51-ns gate width and 39-ns gate delays were determined to be the optimal parameters for sensitive detection. In vivo measurements with the optical diagnosis system were applied to esophagus, stomach, and small intestine using an endoscope in canine animal studies. The rapid tuning capability of the optical diagnosis system contributed greatly to the optimization of wavelength for the observation of porphyrin in the small intestine. When the small intestine was thoroughly washed with water, the emission band which corresponds to porphyrin disappeared. Based on this observation, it was concluded that the detected signal was yielded by porphyrin-containing bile secretion. Also, multispectral analyses using multiple excitations from 415 to 480 nm at 5 nm intervals confirmed the porphyrin detection in the small intestine. The optical diagnosis system was also applied to the detection of human xenograft of oral carcinoma in mice using 5-aminolevulinic acid (5-ALA) which is a photodynamic therapy (PDT) drug. Significant differences in protoporphyrin IX fluorescence intensity between normal and tumor tissue could be obtained 2 hours after the injection of 5-ALA into mice due to the

  7. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: The mechanism of the drilling of holes in vertical metallic plates by cw CO2 laser radiation (United States)

    Likhanskii, V. V.; Loboiko, A. I.; Antonova, G. F.; Krasyukov, A. G.; Sayapin, V. P.


    The possibility of making a hole in a vertical plate with the aid of laser radiation at a surface temperature not exceeding the boiling point is analysed neglecting the vapour pressure. The mechanism of the degradation of the liquid layer involving a reduction of its thickness, as a result of the redistribution of the molten mass owing to the operation of the force of gravity and of thermocapillary convection, is examined. The theoretical dependence of the critical size of the molten zone on the plate thickness is obtained and a comparison is made with experimental data.

  8. Brilliant radiation sources by laser-plasma accelerators and optical undulators

    Energy Technology Data Exchange (ETDEWEB)

    Debus, Alexander


    This thesis investigates the use of high-power lasers for synchrotron radiation sources with high brilliance, from the EUV to the hard X-ray spectral range. Hereby lasers accelerate electrons by laser-wakefield acceleration (LWFA), act as optical undulators, or both. Experimental evidence shows for the first time that LWFA electron bunches are shorter than the driving laser and have a length scale comparable to the plasma wavelength. Furthermore, a first proof of principle experiment demonstrates that LWFA electrons can be exploited to generate undulator radiation. Building upon these experimental findings, as well as extensive numerical simulations of Thomson scattering, the theoretical foundations of a novel interaction geometry for laser-matter interaction are developed. This new method is very general and when tailored towards relativistically moving targets not being limited by the focusability (Rayleigh length) of the laser, while it does not require a waveguide. In a theoretical investigation of Thomson scattering, the optical analogue of undulator radiation, the limits of Thomson sources in scaling towards higher peak brilliances are highlighted. This leads to a novel method for generating brilliant, highly tunable X-ray sources, which is highly energy efficient by circumventing the laser Rayleigh limit through a novel traveling-wave Thomson scattering (TWTS) geometry. This new method suggests increases in X-ray photon yields of 2-3 orders of magnitudes using existing lasers and a way towards efficient, optical undulators to drive a free-electron laser. The results presented here extend far beyond the scope of this work. The possibility to use lasers as particle accelerators, as well as optical undulators, leads to very compact and energy efficient synchrotron sources. The resulting monoenergetic radiation of high brilliance in a range from extreme ultraviolet (EUV) to hard X-ray radiation is of fundamental importance for basic research, medical

  9. Research on quasi-cw and pulse interaction of strong laser radiation with the military technical materials (United States)

    Rycyk, Antoni; CzyŻ, Krzysztof; Sarzyński, Antoni; Skrzeczanowski, Wojciech; Ostrowski, Roman; Strzelec, Marek; Jach, Karol; Świerczyński, Robert


    The paper describes work connected to the investigation of the interaction of strong laser radiation with selected metals, constituting typical materials applied in military technology, like aluminum, copper, brass and titanium. A special laser experimental stand was designed and constructed to achieve this objective. The system consisted of two Nd:YAG lasers working in the regime of free generation (quasi-cw) and another Nd:YAG laser, generating short pre-pulses in the Qswitching regime. During the concurrent operation of both quasi-cw systems it was possible to obtain pulse energies amounting to 10 J in a time period (pulses) of 1 ms. The synchronized, serial operation resulted in energy amounting to 5 J over a time period (pulse) of 2 ms. Variations of the target's surface reflection coefficient, caused by the interaction of short pre-pulses with high power density were determined. The experiments were performed using a standard Nd:YAG laser with amplifiers, generating output pulses whose duration amounted to 10 ns and energy to 1 J, with near Gaussian profile. Laser induced breakdown spectroscopy (LIBS) was used to analyze the emission spectra of targets under the conditions of the interaction of destructive strong and weak as well as long and short excitation laser pulses. A decay of the spectra in the UV range from 200 to around 350 nm was observed when irradiating the target with a long, quasi-cw destructive pulse. Moreover, in the case of an Al target, some AlO molecular spectra appeared, suggesting a chemical reaction of the aluminum atoms with oxygen.

  10. Dichromatic and monochromatic laser radiation effects on survival and morphology of Pantoea agglomerans (United States)

    Thomé, A. M. C.; Souza, B. P.; Mendes, J. P. M.; Soares, L. C.; Trajano, E. T. L.; Fonseca, A. S.


    Despite the beneficial effects of low-level lasers on wound healing, their application for treatment of infected injuries is controversial because low-level lasers could stimulate bacterial growth exacerbating the infectious process. Thus, the aim of this work was to evaluate in vitro effects of low-level lasers on survival, morphology and cell aggregation of Pantoea agglomerans. P. agglomerans samples were isolated from human pressure injuries and cultures were exposed to low-level monochromatic and simultaneous dichromatic laser radiation to study the survival, cell aggregation, filamentation and morphology of bacterial cells in exponential and stationary growth phases. Fluence, wavelength and emission mode were those used in therapeutic protocols for wound healing. Data show no changes in morphology and cell aggregation, but dichromatic laser radiation decreased bacterial survival in exponential growth phase and monochromatic red and infrared lasers increased bacterial survival at the same fluence. Simultaneous dichromatic laser radiation induces biological effects that differ from those induced by monochromatic laser radiation and simultaneous dichromatic laser could be the option for treatment of infected pressure injuries by Pantoea agglomerans.

  11. X-ray-excited optical luminescence of protein crystals: a new tool for studying radiation damage during diffraction data collection. (United States)

    Owen, Robin L; Yorke, Briony A; Pearson, Arwen R


    During X-ray irradiation protein crystals radiate energy in the form of small amounts of visible light. This is known as X-ray-excited optical luminescence (XEOL). The XEOL of several proteins and their constituent amino acids has been characterized using the microspectrophotometers at the Swiss Light Source and Diamond Light Source. XEOL arises primarily from aromatic amino acids, but the effects of local environment and quenching within a crystal mean that the XEOL spectrum of a crystal is not the simple sum of the spectra of its constituent parts. Upon repeated exposure to X-rays XEOL spectra decay non-uniformly, suggesting that XEOL is sensitive to site-specific radiation damage. However, rates of XEOL decay were found not to correlate to decays in diffracting power, making XEOL of limited use as a metric for radiation damage to protein crystals. © 2012 International Union of Crystallography

  12. INTERACTION OF LASER RADIATION WITH MATTER: Influence of a target on operation of a pulsed CO2 laser emitting microsecond pulses (United States)

    Baranov, V. Yu; Dolgov, V. A.; Malyuta, D. D.; Mezhevov, V. S.; Semak, V. V.


    The profile of pulses emitted by a TEA CO2 laser with an unstable resonator changed as a result of interaction of laser radiation with the surface of a metal in the presence of a breakdown plasma. This influence of a target on laser operation and its possible applications in laser processing of materials are analyzed.

  13. Comparison of 1064 nm and 266 nm excitation of laser-induced plasmas for several types of plastics and one explosive

    Energy Technology Data Exchange (ETDEWEB)

    Wang Qianqian [Department of Opto-electric Engineering, Beijing Institute of Technology, 100081 Beijing (China)], E-mail:; Jander, Peter [Fraunhofer-Institut fuer Lasertechnik, Steinbachstr. 15, 52074 Aachen (Germany)], E-mail:; Fricke-Begemann, Cord; Noll, Reinhard [Fraunhofer-Institut fuer Lasertechnik, Steinbachstr. 15, 52074 Aachen (Germany)


    Comparative measurements of Laser-Induced Breakdown Spectroscopy (LIBS) for ultraviolet (UV) and near infrared (NIR) excitation wavelengths on a wide range of plastics and one kind of explosive are presented. The focus of work is on the influence of laser wavelength on the Signal-to-peak to peak noise ratio (SPPNR) for selected emission lines as well as the plasma thresholds for NIR and UV excitation wavelengths. The merits of both excitation wavelengths are discussed with respect to the detection of explosives.

  14. Modelling of micromachining of human tooth enamel by erbium laser radiation (United States)

    Belikov, A. V.; Skrypnik, A. V.; Shatilova, K. V.


    We consider a 3D cellular model of human tooth enamel and a photomechanical cellular model of enamel ablation by erbium laser radiation, taking into account the structural peculiarities of enamel, energy distribution in the laser beam cross section and attenuation of laser energy in biological tissue. The surface area of the texture in enamel is calculated after its micromachining by erbium laser radiation. The influence of the surface area on the bond strength of enamel with dental filling materials is discussed. A good correlation between the computer simulation of the total work of adhesion and experimentally measured bond strength between the dental filling material and the tooth enamel after its micromachining by means of YAG : Er laser radiation is attained.

  15. Solar radiation pumped solid state of lasers for Solar Power Satellites

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Ruiyi [New Jersey (United States)


    The Laser Solar Power Satellites (L-SPS) is the most promising way to overcome global energy and environmental and economical problems. The purpose was to use the favorable combination of solar radiation, modern lasers and the extremely promising phenomenon Optical Phase Conjugation (OPC). Direct conversion of solar energy to energy of a high-power laser beam has the advantage of high efficiency and precise energy transportation. In this paper, direct solar radiation pumping of the laser is compared with the pumping using the intermediate stage of the conversion of the solar radiation in electrical energy. Possible solid-state lasers that can be used in L-SPS are also discussed (including optical system and cooling system). [Spanish] Los Satelites de Energia Solar Laser (L-SPS) son la forma mas prometedora para contrarrestar los problemas globales de energia, ambientales y problemas economicos. El proposito fue el de usar la combinacion favorable de radiacion solar, laseres modernos y el fenomeno extremadamente prometedor de conjugacion de fase optica (OPC). La conversion directa de energia solar a energia de un rayo laser de alta potencia tiene la ventaja de la alta eficiencia y precision de la transportacion de la energia. En este documento la radiacion solar directa impulsada por el laser se compara con la impulsion usando el estado intermedio de conversion de la radiacion solar en energia electrica. Tambien se analizan los posibles laseres de estado solido que pueden usarse en L-SPS (incluyendo el sistema optico y el sistema de enfriamiento).

  16. Propagation of the radiation of laser instruments in road telematics systems (United States)

    Palys, Marek


    In this paper I would like to present the necessity of taking into account a deformation of laser radiation in the real atmosphere while conducting measurements providing data for Intelligent Transport Systems.

  17. Mm-Wave Spectroscopy and Determination of the Radiative Branching Ratios of 11BH for Laser Cooling Experiments (United States)

    Truppe, Stefan; Holland, Darren; Hendricks, Richard James; Hinds, Ed; Tarbutt, Michael


    We aim to slow a supersonic, molecular beam of 11BH using a Zeeman slower and subsequently cool the molecules to sub-millikelvin temperatures in a magneto-optical trap. Most molecules are not suitable for direct laser cooling because the presence of rotational and vibrational degrees of freedom means there is no closed-cycle transition which is necessary to scatter a large number of photons. As was pointed out by Di Rosa, there exists a class of molecules for which the excitation of vibrational modes is suppressed due to highly diagonal Franck-Condon factors. Furthermore, Stuhl et al. showed that angular momentum selection rules can be used to suppress leakage to undesired rotational states. Here we present a measurement of the radiative branching ratios of the A^1Π→ X^1Σ transition in 11BH - a necessary step towards subsequent laser cooling experiments. We also perform high-resolution mm-wave spectroscopy of the J'=1← J=0 rotational transition in the X^1Σ (v=0) state near 708 GHz. From this measurement we derive new, accurate hyper fine constants and compare these to theoretical descriptions. The measured branching ratios suggest that it is possible to laser cool 11BH molecules close to the recoil temperature of 4 μK using three laser frequencies only. M. D. Di Rosa, The European Physical Journal D, 31, 395, 2004 B. K. Stuhl et al., Physical Review Letters, 101, 243002, 2008

  18. [Effects of laser radiation on the periodontium. An animal model approach. Effects of usual radiation dosage]. (United States)

    Noguerol Rodriguez, B; Alandez Chamorro, J; Cañizares Garcia, J; Campos Muñoz, A; Sicilia Felechosa, A


    Twenty four albino mice of forty days old were selected. Twelve forty days old albino mice were irradiated with a Helium-Neon laser source, dose of 10.50566 Jul/cm2. They were divided in two groups according to time of animal sacrifice (immediately after irradiation and ten days after). As control were used twelve mice using the same time as the experimental groups, but without radiation. T.E.M. ultrathin sections showed alteration only in the conjunctiva and in the bone tissues, but not in the epithelial tissue. The bone showed two osteocyte population according to their response to irradiation. The first population showed characteristic comparable with the controls, and the second showed alterations suggestive of a degenerative process. The connective tissue also showed two fibroblasts populations, the first showed signs of a big synthesizing activity, and the second, degenerative signs. The first fibroblast population appeared in the animals sacrificed immediately after irradiation.

  19. Effects of radiation reaction in the interaction between cluster media and high intensity lasers in the radiation dominant regime (United States)

    Iwata, Natsumi; Nagatomo, Hideo; Fukuda, Yuji; Matsui, Ryutaro; Kishimoto, Yasuaki


    Interaction between media composed of clusters and high intensity lasers in the radiation dominant regime, i.e., intensity of 10 22 - 23 W / cm 2 , is studied based on the particle-in-cell simulation that includes the radiation reaction. By introducing target materials that have the same total mass but different internal structures, i.e., uniform plasma and cluster media with different cluster radii, we investigate the effect of the internal structure on the interaction dynamics, high energy radiation emission, and its reaction. Intense radiation emission is found in the cluster media where electrons exhibit non-ballistic motions suffering from strong accelerations by both the penetrated laser field and charge separation field of clusters. As a result, the clustered structure increases the energy conversion into high energy radiations significantly at the expense of the conversion into particles, while the total absorption rate into radiation and particles remains unchanged from the absorption rate into particles in the case without radiation reaction. The maximum ion energy achieved in the interaction with cluster media is found to be decreased through the radiation reaction to electrons into the same level with that achieved in the interaction with the uniform plasma. The clustered structure thus enhances high energy radiation emission rather than the ion acceleration in the considered intensity regime.

  20. High-power direct green laser oscillation of 598 mW in Pr(3+)-doped waterproof fluoroaluminate glass fiber excited by two-polarization-combined GaN laser diodes. (United States)

    Nakanishi, Jun; Horiuchi, Yuya; Yamada, Tsuyoshi; Ishii, Osamu; Yamazaki, Masaaki; Yoshida, Minoru; Fujimoto, Yasushi


    We demonstrated a high-power and highly efficient Pr-doped waterproof fluoride glass fiber laser at 522.2 nm excited by two-polarization-combined GaN laser diodes and achieved a subwatt output power of 598 mW and slope efficiency of 43.0%. This system will enable us to make a vivid laser display, a photocoagulation laser for eye surgery, a color confocal scanning laser microscope, and an effective laser for material processing. Direct visible ultrashort pulse generation is also expected. © 2011 Optical Society of America

  1. Therapy of patients with osteoarthritis with low energy laser radiation

    Directory of Open Access Journals (Sweden)

    L. V. Vasiljeva


    Full Text Available Objective. To assess influence oflow energy laser radiation (LELR on glycosaminoglycan (GAG and vitamin С level in pts with osteoarthritis (OA. Material and methods. 82 pts with primary OA and 25 healthy volunteers signed informed consent were included in an open randomized prospective 12-month study. Inclusion criteria: unsatisfactory effect of previous drug therapy (DT, stable NSAID dose 3-5 days before and during LELR course, absence of comorbid hepatic and kidney diseases in stage of functional decompensation, malignant diseases, exclusion therapy influencing microcirculation, exercise therapy, physical therapy. Intra-articular injections were not done during 3 months before the study. Pts were divided into 2 groups. Group 1 received complex DT and LELR, group 2 - DT. clinical and laboratory parameters were used as efficacy measures. Statistical analysis was performed on personal computer IBM PC (OS — Windows EP Home Edition with Microsoft office and STATISTICA 6.0 programs. Results. Analysis of the results showed significant improvement of most measures in comparison with traditional DT. LELR administration allowed to decrease chondroprotector and NSAID doses. Vitamin С decrease in serum of OA pts may be a risk factor of development and progression of this disease.

  2. Intracavity scanning of the radiation of an electric-discharge nonchain DF laser (United States)

    Alekseev, V. N.; Liber, V. I.; Kotylev, V. N.; Fonin, V. M.


    This paper presents the results of a study of the possibility of using an electrically controlled space-time light modulator based on the transparent electrooptic ceramic PLZT for intracavity scanning of the radiation of a chemical nonchain DF laser (lasing-wavelength range 3.5-4.0 μm). The radiation pulses are scanned in space in the pulsed and pulse-frequency operating modes of the laser.

  3. ?erenkov-based radiation from superluminal excitation in microdroplets by ultrashort pulses. (United States)

    Brunel, M; Mess, L; Gouesbet, G; Gréhan, G


    We demonstrate from a generalized Lorenz-Mie theory that ultrashort pulses can induce superluminal excitation in microdroplets. A ?erenkov-like effect can thus be expected for sufficiently intense ultrashort pulses.

  4. Spatial-temporal characteristics of a SPER laser using transitions of the Cd,Zn,In atoms. [Segmented-Plasma-Excitation-Recombination

    Energy Technology Data Exchange (ETDEWEB)

    Apollonov, V.V.; Derzhavin, S.I.; Prokhorov, A.M.; Sirotkin, A.A. (Institut Obshchei Fiziki, Moscow (USSR))


    An experimental study of a SPER (segmented-plasma-excitation-recombination) laser using transitions of Cd,Zn,In atoms shows that the stretching of the pump pulse trailing edge results in a increased energy output. The recombination pump mechanism in the atomic-transition SPER laser is confirmed. The feasibility of the repetitively pulsed operation of the SPER laser is examined, and it is found that the maximum pulse repetition rate can amount to 10 kHz. 9 refs.

  5. Laser-induced resonant excitation of ethylene molecules in C2H4/C2H2/O2 reactions to enhance diamond deposition (United States)

    Ling, H.; Sun, J.; Han, Y. X.; Gebre, T.; Xie, Z. Q.; Zhao, M.; Lu, Y. F.


    Vibrational resonant excitation of ethylene (C2H4) molecules using a carbon dioxide laser was employed to promote reactions in precursors of ethylene, acetylene (C2H2), and oxygen to enhance diamond deposition. One of the vibrational modes (CH2 wag mode, v7) of the C2H4 molecules was selected to achieve the resonant excitation in the reactions. Optical emission spectroscopy was used to study the effects of laser resonant excitation on the reactions for diamond deposition. The optical emissions of CH and C2 species were enhanced with the laser excitation, indicating that there are more active species generated in the reactions. Thicknesses and grain sizes of the deposited films were increased correspondingly. Temperature calculations from the line set in the R-branch of CH emission spectra indicated that a nonthermal process is involved in the enhanced diamond deposition.

  6. Angular distribution of hypersatellite and satellite radiation emitted after resonant and excitation into $U^{91+}$ ions

    CERN Document Server

    Zakowicz, S; Harman, Z; Scheid, W


    In collisions of heavy few-electron projectile ions with light targets, an electron can be transferred from the target with the simultaneous excitation of a projectile electron. We study the angular distribution of de-excitation X rays following the resonant capture process. Our results are compared to experimental values of Ma et al. [Phys. Rev. A (joint to this issue)] for collisions of U91+ ions with a hydrogen gas target.

  7. Low-threshold wavelength-switchable organic nanowire lasers based on excited-state intramolecular proton transfer. (United States)

    Zhang, Wei; Yan, Yongli; Gu, Jianmin; Yao, Jiannian; Zhao, Yong Sheng


    Coherent light signals generated at the nanoscale are crucial to the realization of photonic integrated circuits. Self-assembled nanowires from organic dyes can provide both a gain medium and an effective resonant cavity, which have been utilized for fulfilling miniaturized lasers. Excited-state intramolecular proton transfer (ESIPT), a classical molecular photoisomerization process, can be used to build a typical four-level system, which is more favorable for population inversion. Low-power driven lasing in proton-transfer molecular nanowires with an optimized ESIPT energy-level process has been achieved. With high gain and low loss from the ESIPT, the wires can be applied as effective FP-type resonators, which generated single-mode lasing with a very low threshold. The lasing wavelength can be reversibly switched based on a conformation conversion of the excited keto form in the ESIPT process. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Combining THz laser excitation with resonant soft X-ray scattering at the Linac Coherent Light Source

    Energy Technology Data Exchange (ETDEWEB)

    Turner, Joshua J., E-mail:; Dakovski, Georgi L.; Hoffmann, Matthias C. [Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Hwang, Harold Y. [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Zarem, Alex; Schlotter, William F.; Moeller, Stefan; Minitti, Michael P. [Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Staub, Urs [Swiss Light Source, Paul Scherrer Institut, 5232 Villigen (Switzerland); Johnson, Steven [ETH Zurich, Institute for Quantum Electronics, Wolfgang-Pauli-Strasse 16, 8093 Zurich (Switzerland); Mitra, Ankush; Swiggers, Michele; Noonan, Peter; Curiel, G. Ivan; Holmes, Michael [Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)


    This paper describes new instrumentation developments at the LCLS for materials studies using THz laser excitation and resonant soft X-ray scattering. This paper describes the development of new instrumentation at the Linac Coherent Light Source for conducting THz excitation experiments in an ultra high vacuum environment probed by soft X-ray diffraction. This consists of a cantilevered, fully motorized mirror system which can provide 600 kV cm{sup −1} electric field strengths across the sample and an X-ray detector that can span the full Ewald sphere with in-vacuum motion. The scientific applications motivated by this development, the details of the instrument, and spectra demonstrating the field strengths achieved using this newly developed system are discussed.

  9. Photo-induced changes in optical parameters of silicate glasses multiphoton laser radiation absorption (United States)

    Efimov, Oleg M.; Glebov, Leonid B.; Matveev, Yurii A.; Mekryukov, Andrei M.


    In this paper are the results of investigations of the mechanisms of photo-induced changes of alkali-silicate (crown) and lead-silicate (flint) glasses optical parameters upon the exposure to intense laser radiation, and the basic regularities of these processes are reported. These investigations were performed in Research Center 'S.I. Vavilov State Optical Institute' during the last 15 years. The kinetics of stable and unstable CC formation and decay, the effect of widely spread impurity ions on these processes, the characteristics of fundamental and impure luminescence, the kinetics of refractive index change under conditions of multi-photon glass matrix excitation, and other properties are considered. On the basis of analysis of received regularities it was shown that the nonlinear coloration of alkali-silicate glasses (the fundamental absorption edge is nearly 6 eV) takes place only as a result of two-photon absorption. Important efforts were aimed at the detection of three or more photon matrix ionization of these glasses, but they failed. However it was established that in the lead silicate glasses, the long-wave carriers mobility boundary is placed considerably higher than the fundamental absorption edge of material matrix. This results in that the linear color centers formation in the lead silicate glasses is not observed. The coloration of these glasses arises only from the two- or three-photon matrix ionization, and the excitation occurs through virtual states that are placed in the fundamental absorption region. In the report the available mechanisms of photo-induced changes of glasses optical parameters, and some applied aspects of this problem are discussed.

  10. Study on the electromagnetic radiation characteristics of discharging excimer laser system (United States)

    Zhao, Duliang; Liang, Xu; Fang, Xiaodong; Wang, Qingsheng


    Excimer laser in condition of high voltage, large current and fast discharge will produce strong electromagnetic pulse radiation and electromagnetic interference on the around electrical equipment. The research on characteristics and distribution of excimer laser electromagnetic radiation could provide important basis for electromagnetic shielding and suppressing electromagnetic interference, and further improving the electromagnetic compatibility of system. Firstly, electromagnetic radiation source is analyzed according to the working principle of excimer laser. The key test points of the electromagnetic radiation, hydrogen thyratron, main discharge circuit and laser outlet, are determined by the mechanical structure and the theory of electromagnetic radiation. Secondly, characteristics of electromagnetic field were tested using a near field probe on the key positions of the vertical direction at 20, 50, and 80 cm, respectively. The main radiation frequencies and the radiation field characteristics in the near field are obtained. The experimental results show that the main radiation frequencies distribute in 47, 65, and 130 MHz for electric field and the main radiation frequencies distribute in 34, 100, and 165 MHz for magnetic field. The intensity of electromagnetic field decreases rapidly with the increase of test distance. The higher the frequency increases, the faster the amplitude attenuate. Finally, several electromagnetic interference suppression measurement methods are proposed from the perspective of electromagnetic compatibility according to the test results.

  11. Evolution analysis of EUV radiation from laser-produced tin plasmas based on a radiation hydrodynamics model. (United States)

    Su, M G; Min, Q; Cao, S Q; Sun, D X; Hayden, P; O'Sullivan, G; Dong, C Z


    One of fundamental aims of extreme ultraviolet (EUV) lithography is to maximize brightness or conversion efficiency of laser energy to radiation at specific wavelengths from laser produced plasmas (LPPs) of specific elements for matching to available multilayer optical systems. Tin LPPs have been chosen for operation at a wavelength of 13.5 nm. For an investigation of EUV radiation of laser-produced tin plasmas, it is crucial to study the related atomic processes and their evolution so as to reliably predict the optimum plasma and experimental conditions. Here, we present a simplified radiation hydrodynamic model based on the fluid dynamic equations and the radiative transfer equation to rapidly investigate the evolution of radiation properties and dynamics in laser-produced tin plasmas. The self-absorption features of EUV spectra measured at an angle of 45° to the direction of plasma expansion have been successfully simulated and explained, and the evolution of some parameters, such as the plasma temperature, ion distribution and density, expansion size and velocity, have also been evaluated. Our results should be useful for further understanding of current research on extreme ultraviolet and soft X-ray source development for applications such as lithography, metrology and biological imaging.

  12. Reflection of Carbon Dioxide (CO 2 ) laser radiation from the theatre ...

    African Journals Online (AJOL)

    This work has investigated the power of both specular and diffusely reflected beams of CO2 laser radiation from metallic and non-metallic surfaces of an operating theatre including surgical instruments (specula) and different samples of wall paints in theatre 6 of the Aberdeen Royal Infirmary, U.K. where the CO2 laser ...

  13. Third harmonic generation of CO2 laser radiation in AgGaSe2 crystal

    Indian Academy of Sciences (India)

    September 2000 physics pp. 405–412. Third harmonic generation of CO2 laser radiation in. AgGaSe2 crystal. GOPAL C BHAR, PATHIK KUMBHAKAR. ½. , D V SATYANARAYANA. ¾. ,. N S N BANERJEE. ¾. , U NUNDY. ¾ and C G CHAO. ¿. Laser Laboratory, Physics Department, Burdwan University, Burdwan 713 104, ...

  14. Pulse-periodic iodine photodissociation laser pumped with radiation from magnetoplasma compressors (United States)

    Kashnikov, G. N.; Orlov, V. K.; Panin, A. N.; Piskunov, A. K.; Reznikov, V. A.


    The design and operation of an iodine photodissociation laser, pumped by radiation from magnetoplasma compressors, are described. The laser uses a closed-circulation system with C3F7I as the working gas. Repetitive-pulse operation has been achieved with an interval between pulses of 1 minute, a lasing energy of 110 J, and a pulse duration of 30 microseconds.

  15. Resonantly excited betatron hard X-Rays from Ionization Injected Electron Beam in a Laser Plasma Accelerator

    CERN Document Server

    Huang, K; Li, Y F; Li, D Z; Tao, M Z; Mirzaie, M; Ma, Y; Zhao, J R; Li, M H; Chen, M; Hafz, N; Sokollik, T; Sheng, Z M; Zhang, J


    A new scheme for bright hard x-ray emission from laser wakefield electron accelerator is reported, where pure nitrogen gas is adopted. Intense Betatron x-ray beams are generated from ionization injected K-shell electrons of nitrogen into the accelerating wave bucket. The x-ray radiation shows synchrotron-like spectrum with total photon yield 8$\\times$10$^8$/shot and $10^8$ over 110keV. In particular, the betatron hard x-ray photon yield is 10 times higher compared to the case of helium gas under the same laser parameters. Particle-in-cell simulation suggests that the enhancement of the x-ray yield results from ionization injection, which enables the electrons to be quickly accelerated to the driving laser region for subsequent betatron resonance. Employing the present scheme,the single stage nitrogen gas target could be used to generate stable high brightness betatron hard x-ray beams.

  16. Spectral characterization of biological aerosol particles using two-wavelength excited laser-induced fluorescence and elastic scattering measurements. (United States)

    Sivaprakasam, Vasanthi; Lin, Horn-Bond; Huston, Alan L; Eversole, Jay D


    A two-wavelength laser-induced fluorescence (LIF) instrument has been developed and used to characterize individual biological aerosol particles, including biological warfare (BW) agent surrogates. Fluorescence in discrete spectral bands from widely different species, and also from similar species under different growth conditions were measured and compared. The two-wavelength excitation approach was found to increase discrimination among several biological materials, and especially with respect to diesel exhaust particles, a common interferent for LIF BW detection systems. The spectral characteristics of a variety of biological materials and ambient air components have been studied as a function of aerosol particle size and incident fluence.

  17. Nonlinear delayed symmetry breaking in a solid excited by hard x-ray free electron laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Ferrer, A., E-mail: [Institute for Quantum Electronics, ETH Zurich, CH-8093 Zurich (Switzerland); Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Johnson, J. A., E-mail:; Mariager, S. O.; Grübel, S.; Staub, U. [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Huber, T.; Trant, M.; Johnson, S. L., E-mail: [Institute for Quantum Electronics, ETH Zurich, CH-8093 Zurich (Switzerland); Zhu, D.; Chollet, M.; Robinson, J.; Lemke, H. T. [LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Ingold, G.; Beaud, P. [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Milne, C. [SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)


    We have studied the ultrafast changes of electronic states in bulk ZnO upon intense hard x-ray excitation from a free electron laser. By monitoring the transient anisotropy induced in an optical probe beam, we observe a delayed breaking of the initial c-plane symmetry of the crystal that lasts for several picoseconds. Interaction with the intense x-ray pulses modifies the electronic state filling in a manner inconsistent with a simple increase in electronic temperature. These results may indicate a way to use intense ultrashort x-ray pulses to investigate high-energy carrier dynamics and to control certain properties of solid-state materials.

  18. Combined Impact of Gamma and Laser Radiation on Peripheral Blood of Rats in vivo (United States)

    Zalesskaya, G. A.; Batay, L. E.; Koshlan, I. V.; Nasek, V. M.; Zilberman, R. D.; Milevich, T. I.; Govorun, R. D.; Koshlan, N. A.; Blaga, P.


    The impact of γ radiation of 137Cs (doses of 1 and 3 Gy), low-intensity laser radiation (λ = 670 nm, 5.3 or 10.6 J/cm2) as well as the influence of consecutive laser and γ radiation on peripheral blood and blood cells (erythrocytes, leukocytes, lymphocytes, granulocytes) were studied by analyzing the number of blood cells, blood absorption spectra, and activity of antioxidant defense enzymes. Two series of experiments were performed on four groups of rats. The rats of the control group (group 1) were not exposed to γ or laser radiation. In the experimental groups, single irradiation of the whole body of rats with γ radiation (group 2), three- or four-day over-vein irradiation of blood in the tail vein by low-intensity laser radiation (group 3), and successive three- or four-day irradiation of blood by laser and then a single irradiation of the whole body with γ radiation (group 4) were performed. It was shown that changes of the blood cell content in the experimental groups are accompanied by changes in the spectral characteristics of the blood and the activity of antioxidant defense enzymes. The radioprotective effect of low-intensity laser radiation is manifested as an increase in the average number of leukocytes and lymphocytes in the group as compared with the postradiation, as well as an increase in the activity of antioxidant protection enzymes. The possibility of using low-intensity optical radiation for correction of hematological disorders caused by ionizing radiation is discussed.

  19. Effects of the excitation density on the laser output of two differently doped Yb:YAG ceramics. (United States)

    Pirri, Angela; Toci, Guido; Alderighi, Daniele; Vannini, Matteo


    We report the behavior of two Yb(3+) doped ceramics (i.e. 10% at. and 20% at.) under quasi-continuous wave laser pumping. Two different behaviors are found depending on the density of Yb(3+) in the excited level. Experimental results show that at low population inversion density, the maximum output power and the efficiency are almost independent on the doping concentration. In particular, an output power as high as 8.9 W with a corresponding slope efficiency of 52% with respect to the injected pump power was reached with the 20% at. sample. Conversely, at high population inversion densities, the 20% doped sample shows a sudden decrease of the laser output for increasing pump power, due to the onset of a nonlinear loss mechanism. Finally, we report a comparison of the experimental results with numerical simulations for the evaluation of the inversion density and of the temperature distribution.

  20. Collective excitability, synchronization, and array-enhanced coherence resonance in a population of lasers with a saturable absorber (United States)

    Perego, A. M.; Lamperti, M.


    In this article we present a numerical study of the collective dynamics in a population of coupled semiconductor lasers with a saturable absorber, operating in the excitable regime under the action of additive noise. We demonstrate that temporal and intensity synchronization takes place in a broad region of the parameter space and for various array sizes. The synchronization is robust and occurs even for a set of nonidentical coupled lasers. The cooperative nature of the system results in a self-organization process which enhances the coherence of the single element of the population too and can have broad impact for detection purposes, for building all-optical simulators of neural networks and in the field of photonics-based computation.

  1. Ferroelectric domain structures on BaTiO{sub 3}(100) observed by laser-excited PEEM

    Energy Technology Data Exchange (ETDEWEB)

    Hoefer, Anke; Duncker, Klaus; Foerster, Stefan; Widdra, Wolf [Martin-Luther-Universitaet Halle-Wittenberg, Halle (Germany)


    The ferroelectric domain structure at a single crystal BaTiO{sub 3}(100) surface is imaged by photoelectron emission microscopy (PEEM) using a fully tunable femtosecond laser source. For a BaTiO{sub 3}(100) surface which is prepared under UHV conditions by sputtering and annealing in an oxygen atmosphere, at room temperature a stripe like domain pattern is observed with high contrast aligned in the high symmetry [100] direction of the substrate. The PEEM pattern is explained by sequences of 90 -a-c domains. Wavelength-dependent images with UV excitation in the range of 290 - 330 nm show a varying domain contrast and allow the determination of the local photoemission threshold for one ferroelectric domain. For higher laser pulse energies and for wavelengths below the onset of one-photon photoemission, two-photon PEEM images show the ferroelectric domain structure as well.

  2. Ablation of oral mucosa by erbium:YAG and holmium:YAG laser radiation (United States)

    Nuebler-Moritz, Michael; Gutknecht, Norbert; Sailer, Hermann F.; Hering, Peter; Prettl, Wilhelm


    The in vitro tissue ablation characteristics of two pulsed mid-infrared lasers were studied, especially, with the intent to evaluate photomechanical and photothermal side effects. The Erbium:YAG laser emitted radiation at 2.94 micrometers in a spiking mode. The free-running beam from the laser was focused onto freshly-excised porcine samples via a 108-mm sapphire lens. The spot size was determined by a photosensitive metallic foil. The Holmium:YAG laser emitted radiation at 2.10 micrometers . The radiation was coupled to a 400- micrometers core quartz fiber. Both lasers were operated at 5 Hz, and 6 pulses were delivered to each porcine specimen using 'dry' and 'wet' ablation mode, respectively. After irradiation, the samples were investigated by means of light and scanning electron microscopy. The results of this survey indicate that both laser types ablate porcine oral mucosa efficiently. The Er:YAG laser produces less surrounding mechanical and thermal damage. In contrast to safe and suitable optical fibers available for the Ho:YAG laser, fiber optical delivery systems for the Er:YAG laser are still in the development phase. Nevertheless, current research work in this field seems promising and the near future may hold an adequate optical transmission systems for the delivery of both wavelengths, 2.10 micrometers and 2.94 micrometers , in order to provide on the one hand atraumatic ablation and on the other hand sufficient hemostasis.

  3. Radiation-Reaction Trapping of Electrons in Extreme Laser Fields

    CERN Document Server

    Ji, L L; Kostyukov, I Yu; Shen, B F; Akli, K


    proposed analysis shows that the threshold of laser field amplitude for RRT is approximately the cubic root of laser wavelength over classical electron radius. Because of the pinching effect of the trapped electron bunch, the required laser intensity for RRT can be further reduced.

  4. Using axicons for depth discrimination in excitation-emission laser scanning imaging systems (United States)

    Iglesias, Ignacio


    Besides generating good approximations to zero-order Bessel beams, an axicon lens coupled to a spatial filter can be used to collect light while preserving information on the depth coordinate of the source location. To demonstrate the principle, we describe an experimental excitation-emission fluorescence imaging system that uses an axicon twice: to generate an excitation Bessel beam and to collect the emitted light.

  5. Acoustic waves in transversely excited atmospheric CO2 laser discharges: effect on performance and reduction techniques

    CSIR Research Space (South Africa)

    von Bergmann, HM


    Full Text Available Results are presented on the influence of acoustic waves on the performance of high-repetition-rate TEA CO2 lasers. It is shown that acoustic waves generated inside the laser cavity lead to nonuniform discharges, resulting in a deterioration...

  6. Isotopically selective RIMS of rare radionuclides by double-resonance excitation with cw lasers

    Energy Technology Data Exchange (ETDEWEB)

    Bushaw, B.A.; Munley, J.T.


    Double-resonance, Resonance Ionization Mass Spectroscopy (RIMS) using two single-frequency dye lasers and a CO{sub 2} laser for photoionization has been shown to be both extremely sensitive and highly selective. Measurements on the radioisotope {sup 210}Pb have demonstrated optical selectivity in excess of 10{sup 9} and detection limits of less than 1 femtogram.

  7. Electron correlation effect on radiative decay processes of the core-excited states of Be-like ions

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Cuicui, E-mail: [Department of Physics, Qinghai Normal University, Xining 810001 (China); Li, Kaikai [College of Forensic Science, People' s Public Security University of China, Beijing 100038 (China); Sun, Yan; Hu, Feng [School of Mathematic and Physical Science, Xuzhou Institute of Technology, Xuzhou 221400, Jiangsu (China)


    Highlights: • Radiative rates of the states 1s2s{sup 2}2p and 1s2p{sup 3} with Z = 8–54 are studied. • Electron correlation effect on the radiative transition rates is studied. • Forbidden transitions are explored. - Abstract: Energy levels and the radiative decay processes of the core-excited configurations 1s2s{sup 2}2p and 1s2p{sup 3} of Be-like ions with Z = 8–54 are studied. Electron correlation effect on the energy levels and the radiative transition rates are studied in detail. Except for E1 radiative transition rates, the E2, M1 and M2 forbidden transitions are also explored. Further relativistic corrections from the Breit interaction, quantum electrodynamics and the finite nuclear size are included in the calculations to make the results more precise. Good agreement is found between our results and other theoretical data.

  8. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Dynamics of a plasma formed by a surface optical-discharge in a metal vapour interacting with a cw CO2 laser beam (United States)

    Zaikin, A. E.; Levin, A. V.; Petrov, A. L.


    A surface optical-discharge plasma was formed in a metal vapour under normal conditions by steady-state irradiation with a cw CO2 laser delivering radiation of moderate (2-4.5 MW cm-2) intensity. This plasma strongly screened the irradiated surface. Under the selected experimental conditions the optical discharge was not a continuous (steady-state) process. The plasma cloud was displaced along the beam out of the waist to a region where the laser radiation intensity was almost an order of magnitude less than the threshold for excitation of the optical-discharge plasma in the vapour. A strong screening of the metal surface, which could even completely stop evaporation of the metal, was observed. Self-oscillations of the optical-discharge plasma were observed for the first time in a vapour interacting with cw CO2 radiation: this was attributed to screening of the target surface. Within one period of the self-oscillations there were additional hf plasma pulsations which led to stratification of the plasma cloud. The results obtained were interpreted.

  9. Particularities of interaction of CO sub 2 -laser radiation with oxide materials

    CERN Document Server

    Salikhov, T P


    The results of experimental investigation of vapor phase influence on the interaction parameters of the infrared laser radiation with oxide materials (Al sub 2 O sub 3 , ZrO sub 2 , CeO sub 2) have been presented. A phenomenon of laser radiation by the samples investigated under laser heating has been experimentally discovered for the first time. This phenomenon connected with forming of the stable vapor shell above the irradiated samples was expressed as a sharp drop in temperature on the heating curve and called as an absorption flash. (author)

  10. Investigation of damage to metals by pulsed CO2 laser radiation (United States)

    Vedenov, A. A.; Gladush, G. G.; Drobyazko, S. V.; Senatorov, Yu M.


    A study was made of the physical mechanism involved in piercing holes in metallic plates, using CO2 laser radiation. It was established experimentally that the energy consumed in removing a unit volume of a metal has a minimum, depending on the duration and energy of the laser pulse. An explanation is proposed for the laws governing this behavior, based on ideas of the ejection of liquid from a crater by the vapor pressure of the material. The effect on the interaction efficiency of the absorption of laser radiation in the plasma jet is taken into account.

  11. Formation of luminescent emitters by intense laser radiation in transparent media (United States)

    Martynovich, E. F.; Kuznetsov, A. V.; Kirpichnikov, A. V.; Pestryakov, Efim V.; Bagayev, Sergei N.


    The formation of luminescent colour centres in the LiF crystal under the action of femtosecond pulses of the first harmonic of a Ti : sapphire laser is experimentally studied. The experiments were carried out at low- and high-aperture focusing of radiation. The effect of both single pulses and multi-pulse trains on the crystals was studied. Channelling of laser radiation in the waveguides, induced by the filaments of the first pulses, is found. The multiphoton mechanism of interband absorption is confirmed. The optimal conditions of laser impact for designing luminescent emitters in the LiF crystal are determined.

  12. Low-level red laser therapy alters effects of ultraviolet C radiation on Escherichia coli cells

    Directory of Open Access Journals (Sweden)

    K.S. Canuto


    Full Text Available Low-level lasers are used at low power densities and doses according to clinical protocols supplied with laser devices or based on professional practice. Although use of these lasers is increasing in many countries, the molecular mechanisms involved in effects of low-level lasers, mainly on DNA, are controversial. In this study, we evaluated the effects of low-level red lasers on survival, filamentation, and morphology of Escherichia coli cells that were exposed to ultraviolet C (UVC radiation. Exponential and stationary wild-type and uvrA-deficient E. coli cells were exposed to a low-level red laser and in sequence to UVC radiation. Bacterial survival was evaluated to determine the laser protection factor (ratio between the number of viable cells after exposure to the red laser and UVC and the number of viable cells after exposure to UVC. Bacterial filaments were counted to obtain the percentage of filamentation. Area-perimeter ratios were calculated for evaluation of cellular morphology. Experiments were carried out in duplicate and the results are reported as the means of three independent assays. Pre-exposure to a red laser protected wild-type and uvrA-deficient E. coli cells against the lethal effect of UVC radiation, and increased the percentage of filamentation and the area-perimeter ratio, depending on UVC fluence and physiological conditions in the cells. Therapeutic, low-level red laser radiation can induce DNA lesions at a sub-lethal level. Consequences to cells and tissues should be considered when clinical protocols based on this laser are carried out.

  13. Low-level red laser therapy alters effects of ultraviolet C radiation on Escherichia coli cells

    Energy Technology Data Exchange (ETDEWEB)

    Canuto, K.S.; Guimaraes, O.R.; Geller, M. [Centro Universitario Serra dos Orgaos, Teresopolis, RJ (Brazil). Centro de Ciencias da Saude; Sergio, L.P.S. [Instituto de Biologia Roberto Alcantara Gomes, Rio de Janeiro, RJ (Brazil). Departamento de Biofisica e Biometria; Paoli, F. [Universidade Federal de Juiz de Fora (UFJF), Juiz de Fora, MG (Brazil). Departamento de Morfologia; Fonseca, A.S., E-mail: [Universidade Federal do Estado do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Departamento de Ciencias Fisiologicas


    Low-level lasers are used at low power densities and doses according to clinical protocols supplied with laser devices or based on professional practice. Although use of these lasers is increasing in many countries, the molecular mechanisms involved in effects of low-level lasers, mainly on DNA, are controversial. In this study, we evaluated the effects of low-level red lasers on survival, filamentation, and morphology of Escherichia coli cells that were exposed to ultraviolet C (UVC) radiation. Exponential and stationary wild-type and uvrA-deficient E. coli cells were exposed to a low-level red laser and in sequence to UVC radiation. Bacterial survival was evaluated to determine the laser protection factor (ratio between the number of viable cells after exposure to the red laser and UVC and the number of viable cells after exposure to UVC). Bacterial filaments were counted to obtain the percentage of filamentation. Area-perimeter ratios were calculated for evaluation of cellular morphology. Experiments were carried out in duplicate and the results are reported as the means of three independent assays. Pre-exposure to a red laser protected wild-type and uvrA-deficient E. coli cells against the lethal effect of UVC radiation, and increased the percentage of filamentation and the area-perimeter ratio, depending on UVC fluence and physiological conditions in the cells. Therapeutic, low-level red laser radiation can induce DNA lesions at a sub-lethal level. Consequences to cells and tissues should be considered when clinical protocols based on this laser are carried out. (author)

  14. Higher order mode excitation in eccentric active nano-particles for tailoring of the near-field radiation

    DEFF Research Database (Denmark)

    Thorsen, R. O.; Arslanagic, Samel


    We examine the excitation of resonant modes inside eccentrically layered cylindrical active nano-particles. The nano-particle is a three-layer structure comprised of a silica core, a free-space middle layer, and an outer shell of silver. It is shown that a concentric configuration, initially desi...... of the gain constant, is shown to be controlled by the direction of the core displacement. The present eccentric active nano-particles may provide alternative strategies for directive near-field radiation relative to the existing designs....

  15. Applications of Light Amplification by Stimulated Emission of Radiation (Lasers) for Restorative Dentistry (United States)

    Najeeb, Shariq; Khurshid, Zohaib; Zafar, Muhammad Sohail; Ajlal, Syed


    Light amplification by stimulated emission of radiation (laser) has been used widely in a range of biomedical and dental applications in recent years. In the field of restorative dentistry, various kinds of lasers have been developed for diagnostic (e.g. caries detection) and operative applications (e.g. tooth ablation, cavity preparation, restorations, bleaching). The main benefits for laser applications are patient comfort, pain relief and better results for specific applications. Major concerns for using dental lasers frequently are high cost, need for specialized training and sensitivity of the technique, thereby compromising its usefulness particularly in developing countries. The main aim of this paper is to evaluate and summarize the applications of lasers in restorative dentistry, including a comparison of the applications of lasers for major restorative dental procedures and conventional clinical approaches. A remarkable increase in the use of lasers for dental application is expected in the near future. PMID:26642047

  16. Applications of Light Amplification by Stimulated Emission of Radiation (Lasers) for Restorative Dentistry. (United States)

    Najeeb, Shariq; Khurshid, Zohaib; Zafar, Muhammad Sohail; Ajlal, Syed


    Light amplification by stimulated emission of radiation (laser) has been used widely in a range of biomedical and dental applications in recent years. In the field of restorative dentistry, various kinds of lasers have been developed for diagnostic (e.g. caries detection) and operative applications (e.g. tooth ablation, cavity preparation, restorations, bleaching). The main benefits for laser applications are patient comfort, pain relief and better results for specific applications. Major concerns for using dental lasers frequently are high cost, need for specialized training and sensitivity of the technique, thereby compromising its usefulness particularly in developing countries. The main aim of this paper is to evaluate and summarize the applications of lasers in restorative dentistry, including a comparison of the applications of lasers for major restorative dental procedures and conventional clinical approaches. A remarkable increase in the use of lasers for dental application is expected in the near future. © 2015 S. Karger AG, Basel.

  17. Probing defect states in polycrystalline GaN grown on Si(111) by sub-bandgap laser-excited scanning tunneling spectroscopy (United States)

    Hsiao, F.-M.; Schnedler, M.; Portz, V.; Huang, Y.-C.; Huang, B.-C.; Shih, M.-C.; Chang, C.-W.; Tu, L.-W.; Eisele, H.; Dunin-Borkowski, R. E.; Ebert, Ph.; Chiu, Y.-P.


    We demonstrate the potential of sub-bandgap laser-excited cross-sectional scanning tunneling microscopy and spectroscopy to investigate the presence of defect states in semiconductors. The characterization method is illustrated on GaN layers grown on Si(111) substrates without intentional buffer layers. According to high-resolution transmission electron microscopy and cathodoluminescence spectroscopy, the GaN layers consist of nanoscale wurtzite and zincblende crystallites with varying crystal orientations and hence contain high defect state densities. In order to discriminate between band-to-band excitation and defect state excitations, we use sub-bandgap laser excitation. We probe a clear increase in the tunnel current at positive sample voltages during sub-bandgap laser illumination for the GaN layer with high defect density, but no effect is found for high quality GaN epitaxial layers. This demonstrates the excitation of free charge carriers at defect states. Thus, sub-bandgap laser-excited scanning tunneling spectroscopy is a powerful complimentary characterization tool for defect states.

  18. Radiation Dose Measurement for High-Intensity Laser Interactions with Solid Targets at SLAC

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Taiee [SLAC National Accelerator Lab., Menlo Park, CA (United States)


    A systematic study of photon and neutron radiation doses generated in high-intensity laser-solid interactions is underway at SLAC National Accelerator Laboratory. We found that these laser-solid experiments are being performed using a 25 TW (up to 1 J in 40 fs) femtosecond pulsed Ti:sapphire laser at the Linac Coherent Light Source’s (LCLS) Matter in Extreme Conditions (MEC) facility. Additionally, radiation measurements were performed with passive and active detectors deployed at various locations inside and outside the target chamber. Results from radiation dose measurements for laser-solid experiments at SLAC MEC in 2014 with peak intensity between 1018 to 7.1x1019 W/cm2 are presented.

  19. Two-frequency picosecond laser based on composite vanadate crystals with {sigma}-polarised radiation

    Energy Technology Data Exchange (ETDEWEB)

    Sirotkin, A A; Sadovskiy, S P; Garnov, Sergei V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)


    A two-frequency picosecond laser based on {alpha}-cut Nd:YVO{sub 4}-YVO{sub 4} composite vanadate crystals is experimentally studied for the s-polarised radiation at the {sup 4}F{sub 3/2} - {sup 4}I{sub 11/2} transition with frequency tuning using Fabry-Perot etalons of different thickness. The difference between the radiation wavelengths was tuned within the range of 1.2-4.4 nm. In the mode-locking regime, the two-frequency radiation power was 280 mW at an absorbed pump power of 12 W. (lasers)

  20. Laser pumped light emitting diodes as broad area sources of coherent radiation (United States)

    Rahman, Faiz; Sorel, Marc


    This paper describes the use of large area light emitting diodes, pumped with various laser sources, as extended area emitters of coherent radiation. The photon recycling takes place through the intermediary of electron hole pair formation and subsequent stimulated recombination. It is possible to generate both spontaneous and stimulated emission together and the two channels are then independent of each other. This allows the generation of a mixture of coherent and non-coherent radiation in any desired proportion. The technique described is a broad-band resonant process with diffusive feedback and can be used for generating non-collimated laser radiation for a variety of applications.

  1. Radiation Hardening and Heavy-ion to Laser Correlation in SiGe Devices and Circuits (United States)


    Radiation Hardening and Heavy-ion to Laser Correlation in SiGe Devices and Circuits Zachary E. Fleetwood and John D. Cressler School of...platforms intended for radiation - intense applications and spaceflight hardware considerations. A number of new radio frequency (RF) studies have...extended the knowledge base of applying radiation -hardening-by- design (RHBD) to SiGe Heterojunction Bipolar Transistor (HBT) circuits. Other research

  2. Phased laser diode array permits selective excitation of ultrasonic guided waves in coated bone-mimicking tubes (United States)

    Moilanen, Petro; Salmi, Ari; Kilappa, Vantte; Zhao, Zuomin; Timonen, Jussi; Hæggström, Edward


    This paper validates simulation predictions, which state that specific modes could be enhanced in quantitative ultrasonic bone testing. Tunable selection of ultrasonic guided wave excitation is useful in non-destructive testing since it permits the mediation of energy into diagnostically useful modes while reducing the energy mediated into disturbing contributions. For instance, it is often challenging to distinguish and extract the useful modes from ultrasound signals measured in bone covered by a soft tissue. We show that a laser diode array can selectively excite ultrasound in bone mimicking phantoms. A fiber-coupled diode array (4 elements) illuminated two solid tubes (2-3 mm wall thickness) embraced by an opaque soft-tissue mimicking elastomer coating (5 mm thick). A predetermined time delay matching the selected mode and frequency was employed between the outputs of the elements. The generated ultrasound was detected by a 215 kHz piezo receiver. Our results suggest that this array reduces the disturbances caused by the elastomer cover and so pave way to permit non-contacting in vivo guided wave ultrasound assessment of human bones. The implementation is small, inexpensive, and robust in comparison with the conventional pulsed lasers.

  3. Compact Handheld Probe for Shifted Excitation Raman Difference Spectroscopy with Implemented Dual-Wavelength Diode Laser at 785 Nanometers. (United States)

    Maiwald, Martin; Eppich, Bernd; Ginolas, Arnim; Sumpf, Bernd; Erbert, Götz; Tränkle, Günther


    A compact handheld probe for shifted-excitation Raman difference spectroscopy (SERDS) with an implemented dual-wavelength diode laser with an emission at 785 nm is presented. The probe is milled from aluminum and has dimensions 100 × 28 × 12 mm. The diode laser provides two excitation lines with a spectral distance of 10 cm(-1) (0.62 nm), has a spectral width smaller than 11 pm, and reaches an optical power of 120 mW ex probe. Raman experiments were carried out using polystyrene (PS) as the test sample. During a measurement time of over 1 h, a stable spectral center position of the Raman line at 999 cm(-1) of PS was achieved within a spectral window of 0.1 cm(-1). Here, the Raman intensity of this line was observed with a peak-to-peak variation smaller than ±2%, dominated by shot noise interference. A deviation of the center position of a Raman line with Raman investigations of the quartz glass window of the SERDS probe showed minor interference. The results demonstrate the suitability of the developed handheld probe for Raman investigations and the application of in situ SERDS experiments to fields such as food safety control, medical diagnostics, and process control.

  4. A cesium plasma TELEC device for conversion of laser radiation to electric power (United States)

    Britt, E. J.; Rasor, N. S.; Lee, G.; Billman, K. W.


    Tests of the thermoelectronic laser energy converter (TELEC) concept are reported. This device has been devised as a means to convert high-average-power laser radiation into electrical energy, a crucial element in any space laser power transmission scheme using the available high-power/efficiency infrared lasers. Theoretical calculations, based upon inverse bremsstrahlung absorption in a cesium plasma, indicate internal conversion efficiency up to 50% with an overall system efficiency of 42%. The experiments reported were made with a test cell designed to confirm the theoretical model rather than demonstrate efficiency; 10.6-micron laser-beam absorption was limited to about 0.001 of the incident beam by the short absorption region. Nevertheless, confirmatory results were obtained, and the conversion of absorbed radiation to electric power is estimated to be near 10%.

  5. Forward-backward asymmetry of photoemission in C60 excited by few-cycle laser pulses (United States)

    Gao, C.-Z.; Dinh, P. M.; Reinhard, P.-G.; Suraud, E.; Meier, C.


    We theoretically analyze angle-resolved photoelectron spectra (ARPES) generated by the interaction of C60 with intense, short laser pulses. In particular, we focus on the impact of the carrier-envelope phase (CEP) onto the angular distribution. The electronic dynamics is described by time-dependent density functional theory, and the ionic background of C60 is approximated by a particularly designed jellium model. Our results show a clear dependence of the angular distributions onto the CEP for very short pulses covering only very few laser cycles, which disappears for longer pulses. For the specific laser parameters used in recent experiments, a very good agreement is obtained. Furthermore, the asymmetry is found to depend on the energy of the emitted photoelectrons. The strong influence of the angular asymmetry of electron emission onto the CEP and pulse duration suggests using this sensitivity as a means to analyze the structure of few-cycle laser pulses.

  6. Influence of geomagnetic field for continuous wave (CW) laser excited sodium guide stars backward fluorescence intensity (United States)

    Zhang, Shao-peng; Wang, Hong-yan; Hua, Wei-hong; Ning, Yu; Xu, Xiao-jun


    Recent years, benefited from their greater coverage and smaller focus anisoplanatism, sodium laser guide stars are becoming more attractive in providing artificial beacons for adaptive optical (AO) system in large ground telescopes compared to Rayleigh guide stars. And it had been found that the Sodium laser guide stars backward fluorescence intensity is closely related with the local magnetic field intensity and direction. In this paper, we make use of the World Magnetic Model (WMM) 2010 and by considering the geographical differences in Beijing, Nanjing and Kunming we investigate the effects of the light intensity, line-width, polarization of the CW laser and re-pumping conditions on the photon return flux by numerically solving the Rochester et al. Bloch model. So in theory we can get better Sodium guide star in Beijing. In conclusion, according to the simulation results, we can acquire much bright of Sodium guide stars by optimize the parameter of the launched 589 nm laser.

  7. Acceleration of a ground-state reaction by selective femtosecond-infrared-laser-pulse excitation (United States)

    Stensitzki, Till; Yang, Yang; Kozich, Valeri; Ahmed, Ashour A.; Kössl, Florian; Kühn, Oliver; Heyne, Karsten


    Infrared (IR) excitation of vibrations that participate in the reaction coordinate of an otherwise thermally driven chemical reaction are believed to lead to its acceleration. Attempts at the practical realization of this concept have been hampered so far by competing processes leading to sample heating. Here we demonstrate, using femtosecond IR-pump IR-probe experiments, the acceleration of urethane and polyurethane formation due to vibrational excitation of the reactants for 1:1 mixtures of phenylisocyanate and cyclohexanol, and toluene-2,4-diisocyanate and 2,2,2-trichloroethane-1,1-diol, respectively. We measured reaction rate changes upon selective vibrational excitation with negligible heating of the sample and observed an increase of the reaction rate up to 24%. The observation is rationalized using reactant and transition-state structures obtained from quantum chemical calculations. We subsequently used IR-driven reaction acceleration to write a polyurethane square on sample windows using a femtosecond IR pulse.

  8. Collective excitations of a laser driven atomic condensate in an optical cavity (United States)

    Öztop, B.; Müstecaplıoğlu, Ö. E.; Türeci, H. E.


    We theoretically examine collective excitations of an optically driven atomic Bose-Einstein condensate, coupled to a high-finesse optical cavity. This open system has been recently used for the experimental demonstration of the Dicke superradiance of cavity photons, which is simultaneously and mutually triggered by spontaneous breaking of translational symmetry of the condensate into a crystalline order. We first develop a Hartree-Fock mean field dynamical model of the physical system. Using this model, we compute the dynamics of the cavity photons, the condensate density profile and the Dicke phase transition diagram. Both the imaginary-time and real-time evolution methods are used in the calculations. Collective excitations are determined by the solving Bogoliubov-de Gennes equations. The spectrum, softening of the modes and energetic hierarchy of excitations are determined.

  9. Mode shape reconstruction of an impulse excited structure using continuous scanning laser Doppler vibrometer and empirical mode decomposition. (United States)

    Kyong, Yongsoo; Kim, Daesung; Dayou, Jedol; Park, Kyihwan; Wang, Semyung


    For vibration testing, discrete types of scanning laser Doppler vibrometer (SLDV) have been developed and have proven to be very useful. For complex structures, however, SLDV takes considerable time to scan the surface of structures and require large amounts of data storage. To overcome these problems, a continuous scan was introduced as an alternative. In this continuous method, the Chebyshev demodulation (or polynomial) technique and the Hilbert transform approach have been used for mode shape reconstruction with harmonic excitation. As an alternative, in this paper, the Hilbert-Huang transform approach is applied to impact excitation cases in terms of a numerical approach, where the vibration of the tested structure is modeled using impulse response functions. In order to verify this technique, a clamped-clamped beam was chosen as the test rig in the numerical simulation and real experiment. This paper shows that with additional innovative steps of using ideal bandpass filters and nodal point determination in the postprocessing, the Hilbert-Huang transformation can be used to create a better mode shape reconstruction even in the impact excitation case.

  10. Combination of fiber-guided pulsed erbium and holmium laser radiation for tissue ablation under water. (United States)

    Pratisto, H; Frenz, M; Ith, M; Altermatt, H J; Jansen, E D; Weber, H P


    Because of the high absorption of near-infrared laser radiation in biological tissue, erbium lasers and holmium lasers emitting at 3 and 2 µm, respectively, have been proven to have optimal qualities for cutting or welding and coagulating tissue. To combine the advantages of both wavelengths, we realized a multiwavelength laser system by simultaneously guiding erbium and holmium laser radiation by means of a single zirconium fluoride (ZrF(4)) fiber. Laser-induced channel formation in water and poly(acrylamide) gel was investigated by the use of a time-resolved flash-photography setup, while pressure transients were recorded simultaneously with a needle hydrophone. The shapes and depths of vapor channels produced in water and in a submerged gel after single erbium and after combination erbium-holmium radiation delivered by means of a 400-µm ZrF(4) fiber were measured. Transmission measurements were performed to determine the amount of pulse energy available for tissue ablation. The effects of laser wavelength and the delay time between pulses of different wavelengths on the photomechanical and photothermal responses of meniscal tissue were evaluated in vitro by the use of histology. It was observed that the use of a short (200-µs, 100-mJ) holmium laser pulse as a prepulse to generate a vapor bubble through which the ablating erbium laser pulse can be transmitted (delay time, 100 µs) increases the cutting depth in meniscus from 450 to 1120 µm as compared with the depth following a single erbium pulse. The results indicate that a combination of erbium and holmium laser radiation precisely and efficiently cuts tissue under water with 20-50-µm collateral tissue damage.

  11. Stress relaxation and cartilage shaping under laser radiation (United States)

    Sobol, Emil N.; Sviridov, Alexander P.; Bagratashvili, Victor N.; Omelchenko, Alexander I.; Ovchinnikov, Yuriy M.; Shekhter, Anatoliy B.; Downes, S.; Howdle, Steven; Jones, Nicholas; Lowe, J.


    The problem of a purposeful change of the shape of cartilage is of great importance for otolaryngology, orthopaedics, and plastic surgery. In 1992 we have found a possibility of controlled shaping of cartilage under moderate laser heating. This paper presents new results in studies of that phenomenon. We have measured temperature and stress in a tissue undergoing to irradiation with a Holmium laser. Study of cartilage structure allowed us to find conditions for laser shaping without pronounced alterations in the structure of matrix.

  12. Calculation of laser induced impulse based on the laser supported detonation wave model with dissociation, ionization and radiation

    Energy Technology Data Exchange (ETDEWEB)

    Gan, Li, E-mail:; Mousen, Cheng; Xiaokang, Li [College of Aerospace Science and Engineering, National University of Defense Technology, Changsha (China)


    In the laser intensity range that the laser supported detonation (LSD) wave can be maintained, dissociation, ionization and radiation take a substantial part of the incidence laser energy. There is little treatment on the phenomenon in the existing models, which brings obvious discrepancies between their predictions and the experiment results. Taking into account the impact of dissociation, ionization and radiation in the conservations of mass, momentum and energy, a modified LSD wave model is developed which fits the experimental data more effectively rather than the existing models. Taking into consideration the pressure decay of the normal and the radial rarefaction, the laser induced impulse that is delivered to the target surface is calculated in the air; and the dependencies of impulse performance on laser intensity, pulse width, ambient pressure and spot size are indicated. The results confirm that the dissociation is the pivotal factor of the appearance of the momentum coupling coefficient extremum. This study focuses on a more thorough understanding of LSD and the interaction between laser and matter.

  13. High-efficiency generation of pulsed Lyman-α radiation by resonant laser wave mixing in low pressure Kr-Ar mixture. (United States)

    Saito, Norihito; Oishi, Yu; Miyazaki, Koji; Okamura, Kotaro; Nakamura, Jumpei; Louchev, Oleg A; Iwasaki, Masahiko; Wada, Satoshi


    We report an experimental generation of ns pulsed 121.568 nm Lyman-α radiation by the resonant nonlinear four-wave mixing of 212.556 nm and 845.015 nm radiation pulses providing a high conversion efficiency 1.7x10-3 with the output pulse energy 3.6 μJ achieved using a low pressure Kr-Ar mixture. Theoretical analysis shows that this efficiency is achieved due to the advantage of using (i) the high input laser intensities in combination with (ii) the low gas pressure allowing us to avoid the onset of full-scale discharge in the laser focus. In particular, under our experimental conditions the main mechanism of photoionization caused by the resonant 2-photon 212.556 nm radiation excitation of Kr atoms followed by the 1-photon ionization leads to ≈17% loss of Kr atoms and efficiency loss only by the end of the pulse. The energy of free electrons, generated by 212.556 nm radiation via (2 + 1)-photon ionization and accelerated mainly by 845.015 nm radiation, remains during the pulse below the level sufficient for the onset of full-scale discharge by the electron avalanche. Our analysis also suggests that ≈30-fold increase of 845.015 nm pulse energy can allow one to scale up the L-α radiation pulse energy towards the level of ≈100 μJ.

  14. Regeneration of spine disc and joint cartilages under temporal and space modulated laser radiation (United States)

    Sobol, E.; Shekhter, A.; Baskov, A.; Baskov, V.; Baum, O.; Borchshenko, I.; Golubev, V.; Guller, A.; Kolyshev, I.; Omeltchenko, A.; Sviridov, A.; Zakharkina, O.


    The effect of laser radiation on the generation of hyaline cartilage in spine disc and joints has been demonstrated. The paper considers physical processes and mechanisms of laser regeneration, presents results of investigations aimed to optimize laser settings and to develop feedback control system for laser reconstruction of spine discs. Possible mechanisms of laser-induced regeneration include: (1) Space and temporary modulated laser beam induces nonhomogeneous and pulse repetitive thermal expansion and stress in the irradiated zone of cartilage. Mechanical effect due to controllable thermal expansion of the tissue and micro and nano gas bubbles formation in the course of the moderate (up to 45-50 oC) heating of the NP activate biological cells (chondrocytes) and promote cartilage regeneration. (2) Nondestructive laser radiation leads to the formation of nano and micro-pores in cartilage matrix. That promotes water permeability and increases the feeding of biological cells. Results provide the scientific and engineering basis for the novel low-invasive laser procedures to be used in orthopedics for the treatment cartilages of spine and joints. The technology and equipment for laser reconstruction of spine discs have been tested first on animals, and then in a clinical trial. Since 2001 the laser reconstruction of intervertebral discs have been performed for 340 patients with chronic symptoms of low back or neck pain who failed to improve with non-operative care. Substantial relief of back pain was obtained in 90% of patients treated who returned to their daily activities. The experiments on reparation of the defects in articular cartilage of the porcine joints under temporal and spase modulated laser radiation have shown promising results.

  15. A new method and device of aligning patient setup lasers in radiation therapy. (United States)

    Hwang, Ui-Jung; Jo, Kwanghyun; Lim, Young Kyung; Kwak, Jung Won; Choi, Sang Hyuon; Jeong, Chiyoung; Kim, Mi Young; Jeong, Jong Hwi; Shin, Dongho; Lee, Se Byeong; Park, Jeong-Hoon; Park, Sung Yong; Kim, Siyong


    The aim of this study is to develop a new method to align the patient setup lasers in a radiation therapy treatment room and examine its validity and efficiency. The new laser alignment method is realized by a device composed of both a metallic base plate and a few acrylic transparent plates. Except one, every plate has either a crosshair line (CHL) or a single vertical line that is used for alignment. Two holders for radiochromic film insertion are prepared in the device to find a radiation isocenter. The right laser positions can be found optically by matching the shadows of all the CHLs in the gantry head and the device. The reproducibility, accuracy, and efficiency of laser alignment and the dependency on the position error of the light source were evaluated by comparing the means and the standard deviations of the measured laser positions. After the optical alignment of the lasers, the radiation isocenter was found by the gantry and collimator star shots, and then the lasers were translated parallel to the isocenter. In the laser position reproducibility test, the mean and standard deviation on the wall of treatment room were 32.3 ± 0.93 mm for the new method whereas they were 33.4 ± 1.49 mm for the conventional method. The mean alignment accuracy was 1.4 mm for the new method, and 2.1 mm for the conventional method on the walls. In the test of the dependency on the light source position error, the mean laser position was shifted just by a similar amount of the shift of the light source in the new method, but it was greatly magnified in the conventional method. In this study, a new laser alignment method was devised and evaluated successfully. The new method provided more accurate, more reproducible, and faster alignment of the lasers than the conventional method.

  16. Effect of rippled laser beam on excitation of ion acoustic wave

    Indian Academy of Sciences (India)

    in the plasma which may subsequently dump their energies to particles via Landau damp- ing and heat the plasma to thermonuclear temperature. Excitation of plasma waves through different mechanisms has also been reported in a number of investigations [1–7]. The di- rect and indirect experimental evidences reveal that ...

  17. Cherenkov excited phosphorescence-based pO2 estimation during multi-beam radiation therapy: phantom and simulation studies. (United States)

    Holt, Robert W; Zhang, Rongxiao; Esipova, Tatiana V; Vinogradov, Sergei A; Glaser, Adam K; Gladstone, David J; Pogue, Brian W


    Megavoltage radiation beams used in External Beam Radiotherapy (EBRT) generate Cherenkov light emission in tissues and equivalent phantoms. This optical emission was utilized to excite an oxygen-sensitive phosphorescent probe, PtG4, which has been developed specifically for NIR lifetime-based sensing of the partial pressure of oxygen (pO2). Phosphorescence emission, at different time points with respect to the excitation pulse, was acquired by an intensifier-gated CCD camera synchronized with radiation pulses delivered by a medical linear accelerator. The pO2 distribution was tomographically recovered in a tissue-equivalent phantom during EBRT with multiple beams targeted from different angles at a tumor-like anomaly. The reconstructions were tested in two different phantoms that have fully oxygenated background, to compare a fully oxygenated and a fully deoxygenated inclusion. To simulate a realistic situation of EBRT, where the size and location of the tumor is well known, spatial information of a prescribed region was utilized in the recovery estimation. The phantom results show that region-averaged pO2 values were recovered successfully, differentiating aerated and deoxygenated inclusions. Finally, a simulation study was performed showing that pO2 in human brain tumors can be measured to within 15 mmHg for edge depths less than 10-20 mm using the Cherenkov Excited Phosphorescence Oxygen imaging (CEPhOx) method and PtG4 as a probe. This technique could allow non-invasive monitoring of pO2 in tumors during the normal process of EBRT, where beams are generally delivered from multiple angles or arcs during each treatment fraction.

  18. New Principles of Laser-Based Radiation an Particle Sources

    National Research Council Canada - National Science Library

    Kaplan, Alexander


    .... Continuing pioneering collaborative research on fundamental new phenomenon of multi-mode interference in quantum mechanics, in particular highly regular pattern formation by 8-excited wave functions. 2.iv...

  19. Near-field properties of a gold nanoparticle array on different substrates excited by a femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Nedyalkov, Nikolay N [Department of Electronics and Electrical Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Atanasov, Petar A [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784 (Bulgaria); Obara, Minoru [Department of Electronics and Electrical Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)


    In this paper we present experimental and theoretical results on the properties of the electromagnetic field in the near-field zone of gold nanoparticles excited by an 800 nm ultrashort laser pulse. The near-field properties are studied for the case of a single isolated particle and 2D nanoparticle array case. Particles are deposited on different substrates: metal (Au), semiconductor (Si) and dielectric (SiO{sub 2}). The calculations based on the finite difference time domain (FDTD) simulation technique predict that the field in the vicinity of the particles is enhanced as the magnitude of the field intensity depends on the substrate material and the interparticle distance for 2D array. For closely arrayed nanoparticles on the gold substrate, the maximal field intensity is more than two times lower than that of a single particle. With the increase of the distance between 200 nm diameter gold particles, the value of the field intensity increases up to a distance of about 800 nm. The theoretical prediction of the field enhancement on the substrate is confirmed experimentally. The irradiation of the nanoparticles deposited on the three different substrates with a single laser pulse of a Ti:sapphire laser results in a nanohole formation. Discussion on the observed properties is presented.

  20. Laser excitation and fully non-contact sensing ultrasonic propagation imaging system for damage evaluation (United States)

    Dhital, Dipesh; Lee, Jung Ryul; Park, Chan Yik; Flynn, Eric


    Various types of damages occur in aerospace, mechanical and many other engineering structures, and a reliable nondestructive evaluation technique is essential to detect any possible damage at the initiation phase. Ultrasound has been widely used but the conventional contact ultrasonic inspection techniques are not suitable for mass and couplant sensitive structures and are relatively slow. This study presents a fully non-contact hybrid laser ultrasonic generation and piezoelectric air-coupled transducer (ACT)/laser Doppler vibrometer (LDV) sensing technique combined with ultrasonic wave propagation imaging (UWPI), ultrasonic spectral imaging (USI) and wavelet-transformed ultrasonic propagation imaging (WUPI) algorithms to extract defect-sensitive features aimed at performing a thorough diagnosis of damage. Optimization enables improved performance efficiency of ACT and LDV to be used as receivers for non-contact hybrid laser ultrasonic propagation imaging (UPI) system as shown from the experimental results in this study. Real fatigue closed surface micro crack on metal structure was detected using hybrid laser ultrasonic generation/ACT sensing system, with size detection accuracy as high as 96%. Impact damages on carbon fiber reinforced plastic composite wing-box specimen were detected and localized using hybrid laser ultrasonic generation/LDV sensing system.

  1. Numerical method for calculating sound radiation characteristics of plate structure excited by turbulent boundary layer

    Directory of Open Access Journals (Sweden)

    LI Zuhui


    Full Text Available As the turbulent boundary layer (TBL is one of the most important sources of vibration and noise in underwater vehicles, there is an important significance in studying the numerical method for the calculation of flow-induced noise. In this paper, the methods of Principal Component Analysis (PCA and Vibro-Acoustic Transfer Vectors (VATV based on LMS Virtual Lab software are used to calculate the sound characteristics of a plate structure excited by TBL. The Corcos model of the wave number-frequency spectrum of the wall pressure field beneath the TBL is used to describe random excitation. By comparing the calculating time and sound pressure auto power spectra curves of the two methods, the following conclusions are obtained: both the VATV method and PCA method can be used effectively for the calculation of the flow-induced noise of structures excited by the TBL, and the results of the two methods match; the VATV method can quickly forecast the structure of flow-induced noise and takes up fewer computing resources than the PCA method; the PCA method can also obtain the structure vibration response in comparison with the VATV method. The current work can serve as a reference for the rapid prediction of the flow-induced noise of underwater structures.

  2. Development of Laser Plasma X-ray Microbeam Irradiation System and Radiation Biological Application (United States)

    Sato, Katsutoshi; Nishikino, Masaharu; Numasaki, Hodaka; Kawachi, Tetsuya; Teshima, Teruki; Nishimura, Hiroaki

    Laser plasma x-ray source has the features such as ultra short pulse, high brilliance, monochromaticity, and focusing ability. These features are excellent compared with conventional x-ray source. In order to apply the laser plasma x-ray source to the biomedical study and to more closely research the radiobilogical responce of the cancer cell such as radiation induced bystander effect, we have developed x-ray microbeam system using laser plasma x-ray source. The absorbed dose of laser plasma x-ray was estimated with Gafchromic EBT film and DNA double strand breaks on the cells were detected by immunofluorescence staining. When the cells were irradiated with laser plasma x-ray, the circular regions existing γ-H2AX positive cells were clearly identified. The usefulness of the laser plasma x-ray on the radiobiological study was proved in this research.

  3. Comparison between Accelerometer and Laser Vibrometer to Measure Traffic Excited Vibrations on Bridges

    Directory of Open Access Journals (Sweden)

    G. Rossi


    Full Text Available The use of accelerometer based measurement techniques for evaluating bridge forced vibrations or to perform bridge modal analysis is well established. It is well known to all researchers who have experience in vibration measurements that values of acceleration amplitude can be very low at low frequencies and that a limitation to the use of accelerometer can be due to the threshold parameter of this kind of transducer. Under this conditions the measurement of displacement seems more appropriate. On the other hand laser vibrometer systems detect relative displacements as opposed to the absolute measures of accelerometers. Vibrations have been measured simultaneously by a typical accelerometer for civil structures and by a laser vibrometer equipped with a fringe counter board in terms of velocity and displacements. The accelerations calculated from the laser vibrometer signals and the one directly measured by the accelerometer has been compared.

  4. The use of surface corona discharges to excite high-pressure gas-lasers

    Directory of Open Access Journals (Sweden)

    D. J. Brink


    Full Text Available A stabilization technique for the production of homogeneous gas discharge at high pressures has been developed. The technique is based on photo-pre-ionization from a corona-type surface-discharge. It was possible to develop a number of laser systems based on this stabilization principle, which exceeded the performance of conventional systems in many respects. This paper provides a summary of the most important properties and principles of the surface discharges. Four laser systems utilizing this stabilization method are also discussed.

  5. Parametric waves excitation in relativistic laser-plasma interactions for electron acceleration (United States)

    Shulyapov, S. A.; Ivanov, K. A.; Tsymbalov, I. N.; Krestovskih, D. A.; Savel'ev, A. B.; Ksenofontov, P. A.; Brantov, A. V.; Bychenkov, V. Yu


    Plasma created by femtosecond laser pulse of high intensity can be used as the brilliant source of high energy electrons, ions and x- or γ-rays. In most cases, laser pulses with high contrast are used for particle acceleration. But, it has been shown, that changing parameters of pre-plasma layer on the surface of the target can significantly increase electron energies. In this work we present the results of the experimental and numerical studies of the abnormally hot electron generation mechanisms in the case of long scale pre-plasma layer subcritical density.

  6. Changes in gene expression by 193- and 248-nm excimer laser radiation in cultured human fibroblasts. (United States)

    Rimoldi, D; Flessate, D M; Samid, D


    Tissue ablation by ultraviolet excimer lasers results in exposure of viable cells to subablative doses of radiation. To understand the potential biological consequences better, we have studied changes in gene expression in cultured human skin fibroblasts exposed to either 193- or 248-nm laser light. Northern blot analyses revealed that both treatments up-regulate a common set of genes, including interstitial collagenase, tissue inhibitor of metalloprotease, metallothionein, and the proto-oncogene c-fos. Dose-response and kinetic studies of collagenase induction by 193-nm radiation showed a maximal effect with 60 J/m2 and at approximately 24 h. The induction was still persistent 96 h later. In addition to the commonly affected genes, known to be activated also by conventional UV light (254 nm) and tumor-promoting phorbol esters, other genes were found to be selectively induced by the 193-nm radiation. The heat-shock hsp70 mRNA, undetectable in controls and in cultures irradiated at 248 nm, was transiently induced 8 h after exposure to 193-nm radiation. Furthermore, a selective up-regulation of collagen type I expression was observed. The results indicate that the 193- and 248-nm radiations by excimer lasers elicit specific and different cellular responses, in addition to an overlapping pathway of gene activation common also to UV radiation by germicidal lamps. The laser-induced genes could serve as molecular markers in evaluating cell injury in situ.

  7. LASERS: Characteristics of the radiation of an Nd:YAG laser with an intracavity spatiotemporal modulator based on a PLZT electro-optical ceramic (United States)

    Alekseev, V. N.; Kotylev, V. N.; Liber, V. I.


    The characteristics of the radiation of a laser with intracavity scanning with the aid of electrically controlled spatiotemporal modulators based on a transparent electro-optical PLZT ceramic were investigated. The possibility of the generation of packets of single pulses of scanning laser radiation with a repetition frequency up to 100 kHz, and up to 10 kHz under the conditions of continuous flashlamp pumping with an intracavity spatiotemporal modulator is demonstrated. Possible applications of the laser are discussed.

  8. Enhanced chemical vapor deposition of diamond by wavelength-matched vibrational excitations of ethylene molecules using tunable CO2 laser irradiation (United States)

    Ling, H.; Xie, Z. Q.; Gao, Y.; Gebre, T.; Shen, X. K.; Lu, Y. F.


    Wavelength-matched vibrational excitations of ethylene (C2H4) molecules using a tunable carbon dioxide (CO2) laser were employed to significantly enhance the chemical vapor deposition (CVD) of diamond in open air using a precursor gas mixture of C2H4, acetylene (C2H2), and oxygen (O2). The CH2-wag vibration mode (ν7) of the C2H4 molecules was selected to achieve the resonant excitation in the CVD process. Both laser wavelengths of 10.591 and 10.532 μm were applied to the CVD processes to compare the C2H4 excitations and diamond depositions. Compared with 10.591 μm produced by common CO2 lasers, the laser wavelength of 10.532 μm is much more effective to excite the C2H4 molecules through the CH2-wag mode. Under the laser irradiation with a power of 800 W and a wavelength of 10.532 μm, the grain size in the deposited diamond films was increased by 400% and the film thickness was increased by 300%. The quality of the diamond crystals was also significantly enhanced.

  9. Efficient Excitation of Gain-Saturated Sub-9-nm-Wavelength Tabletop Soft-X-Ray Lasers and Lasing Down to 7.36 nm

    Directory of Open Access Journals (Sweden)

    D. Alessi


    Full Text Available We have demonstrated the efficient generation of sub-9-nm-wavelength picosecond laser pulses of microjoule energy at 1-Hz repetition rate with a tabletop laser. Gain-saturated lasing was obtained at λ=8.85  nm in nickel-like lanthanum ions excited by collisional electron-impact excitation in a precreated plasma column heated by a picosecond optical laser pulse of 4-J energy. Furthermore, isoelectronic scaling along the lanthanide series resulted in lasing at wavelengths as short as λ=7.36  nm. Simulations show that the collisionally broadened atomic transitions in these dense plasmas can support the amplification of subpicosecond soft-x-ray laser pulses.

  10. Laser-plasma SXR/EUV sources: adjustment of radiation parameters for specific applications (United States)

    Bartnik, A.; Fiedorowicz, H.; Fok, T.; Jarocki, R.; Kostecki, J.; Szczurek, A.; Szczurek, M.; Wachulak, P.; Wegrzyński, Ł.


    In this work soft X-ray (SXR) and extreme ultraviolet (EUV) laser-produced plasma (LPP) sources employing Nd:YAG laser systems of different parameters are presented. First of them is a 10-Hz EUV source, based on a double-stream gaspuff target, irradiated with the 3-ns/0.8J laser pulse. In the second one a 10 ns/10 J/10 Hz laser system is employed and the third one utilizes the laser system with the pulse shorten to approximately 1 ns. Using various gases in the gas puff targets it is possible to obtain intense radiation in different wavelength ranges. This way intense continuous radiation in a wide spectral range as well as quasi-monochromatic radiation was produced. To obtain high EUV or SXR fluence the radiation was focused using three types of grazing incidence collectors and a multilayer Mo/Si collector. First of them is a multfoil gold plated collector consisted of two orthogonal stacks of ellipsoidal mirrors forming a double-focusing device. The second one is the ellipsoidal collector being part of the axisymmetrical ellipsoidal surface. Third of the collectors is composed of two aligned axisymmetrical paraboloidal mirrors optimized for focusing of SXR radiation. The last collector is an off-axis ellipsoidal multilayer Mo/Si mirror allowing for efficient focusing of the radiation in the spectral region centered at λ = 13.5 ± 0.5 nm. In this paper spectra of unaltered EUV or SXR radiation produced in different LPP source configurations together with spectra and fluence values of focused radiation are presented. Specific configurations of the sources were assigned to various applications.

  11. Nonlinear excitations of blood flow in large vessels under thermal radiations and uniform magnetic field (United States)

    Tabi, C. B.; Motsumi, T. G.; Bansi Kamdem, C. D.; Mohamadou, A.


    A nonlinear model of blood flow in large vessels is addressed. The influence of radiations, viscosity and uniform magnetic fields on velocity and temperature distribution waveforms is studied. Exact solutions for the studied model are investigated through the F - expansion method. Based on the choice of parameter values, single-, multi-soliton and Jacobi elliptic function solutions are obtained. Viscosity and permanent magnetic field bring about wave spreading and reduce the velocity of blood, while radiations have reversed effects with strong impact on the waveform frequency of both the velocity and temperature distribution.

  12. Electronically driven adsorbate excitation mechanism in femtosecond-pulse laser desorption

    DEFF Research Database (Denmark)

    Brandbyge, Mads; Hedegård, Per; Heinz, T. F.


    Femtosecond-pulse laser desorption is a process in which desorption is driven by a subpicosecond temperature pulse of order 5000 K in the substrate-adsorbate electron system, whose energy is transferred into the adsorbate center-of-mass degrees of freedom by a direct coupling mechanism. We presen...

  13. Designing a Broadband Pump for High-Quality Micro-Lasers via Modified Net Radiation Method

    CERN Document Server

    Nechayev, Sergey; Baldo, Marc A; Rotschild, Carmel


    High-quality micro-lasers are key ingredients in non-linear optics, communication, sensing and low-threshold solar-pumped lasers. However, such micro-lasers exhibit negligible absorption of free-space broadband pump light. Recently, this limitation was lifted by cascade energy transfer, in which the absorption and quality factor are modulated with wavelength, enabling non-resonant pumping of high-quality micro-lasers and solar-pumped laser to operate at record low solar concentration. Here, we present a generic theoretical framework for modeling the absorption, emission and energy transfer of incoherent radiation between cascade sensitizer and laser gain media. Our model is based on linear equations of the modified net radiation method and is therefore robust, fast converging and has low complexity. We apply this formalism to compute the optimal parameters of low-threshold solar-pumped lasers. It is revealed that the interplay between the absorption and self-absorption of such lasers defines the optimal pump ...

  14. Flashlamp excitation of NaF:F2(+) using the fluorescent transformation of pumping radiation (United States)

    Kolerov, A. N.; Arzumanian, Sh. O.; Koliago, S. S.; Chirkina, K. P.; Gritsai, I. I.


    The feasibility of obtaining stimulated emission from an NaF:F2(+) crystal pumped by a xenon lamp is demonstrated. The UV component of the lamp is transformed into the F2(+) color center absorption band using a C-102 solution and a crystalline tube made of Al2O3:Ti(3+). Lasing was obtained in all of the active media, making it possible to use this laser as a multicolor spectrum analyzer.

  15. New frontier of laser particle acceleration: driving protons to 80 MeV by radiation pressure

    CERN Document Server

    Kim, I Jong; Kim, Chul Min; Kim, Hyung Taek; Lee, Chang-Lyoul; Choi, Il Woo; Singhal, Himanshu; Sung, Jae Hee; Lee, Seong Ku; Lee, Hwang Woon; Nickles, Peter V; Jeong, Tae Moon; Nam, Chang Hee


    The radiation pressure acceleration (RPA) of charged particles has been considered a challenging task in laser particle acceleration. Laser-driven proton/ion acceleration has attracted considerable interests due to its underlying physics and potential for applications such as high-energy density physics, ultrafast radiography, and cancer therapy. Among critical issues to overcome the biggest challenge is to produce energetic protons using an efficient acceleration mechanism. The proton acceleration by radiation pressure is considerably more efficient than the conventional target normal sheath acceleration driven by expanding hot electrons. Here we report the generation of 80-MeV proton beams achieved by applying 30-fs circularly polarized laser pulses with an intensity of 6.1 x 1020 W/cm2 to ultrathin targets. The radiation pressure acceleration was confirmed from the obtained optimal target thickness, quadratic energy scaling, polarization dependence, and 3D-PIC simulations. We expect this fast energy scalin...

  16. Quantum mechanical theory of collisional ionization in the presence of intense laser radiation (United States)

    Bellum, J. C.; George, T. F.


    The paper presents a quantum mechanical formalism for treating ionizing collisions occurring in the presence of an intense laser field. Both the intense laser radiation and the internal electronic continuum states associated with the emitted electrons are rigorously taken into account by combining discretization techniques with expansions in terms of electronic-field representations for the quasi-molecule-plus-photon system. The procedure leads to a coupled-channel description of the heavy-particle dynamics which involves effective electronic-field potential surfaces and continua. It is suggested that laser-influenced ionizing collisions can be studied to verify the effects of intense laser radiation on inelastic collisional processes. Calculation procedures for electronic transition dipole matrix elements between discrete and continuum electronic states are outlined.

  17. Reduction of collisional-radiative models for laser-produced argon plasmas (United States)

    Abrantes, Richard June; Karagozian, Ann; Le, Hai


    The formation of a laser-induced plasma involves a variety of physical phenomena stemming from the laser-plasma interaction. A thorough understanding of these processes encourages improvement and innovation for many applications. In this work, we aim to computationally reduce a previously-developed collisional-radiative (CR) model constructed from the LANL database, which includes all of the relevant collisional and radiative processes for all the ionic stages of argon. The laser is coupled to the plasma via multiphoton ionization and inverse Bremsstrahlung, processes important for electron production and heating. The use of the CR model allows us to identify dominant mechanisms responsible for initial breakdown of the gas and thermal equilibriation processes. The results are compared with experimental data from laser-induced breakdown experiments. Research supported by the AFOSR.

  18. Laser-Excited Atomic Fluorescence and Ionization in a Graphite Furnace for the Determination of Metals and Nonmetals (United States)

    Butcher, David James


    Here is reported novel instrumentation for atomic spectrometry that combined the use of a pulsed laser system as the light source and an electrothermal atomizer as the atom cell. The main goal of the research was to develop instrumentation that was more sensitive for elemental analysis than commercially available instruments and could be used to determine elements in real sample matrices. Laser excited atomic fluorescence spectrometry (LEAFS) in an electrothermal atomizer (ETA) was compared to ETA atomic absorption spectrometry (AAS) for the determination of thallium, manganese, and lead in food and agricultural standard reference materials (SRMs). Compared to ETA AAS, ETA LEAFS has a longer linear dynamic range (LDR) (5-7 orders of magnitude compared to 2-3 orders of magnitude) and higher sensitivity (10 ^{-16} to 10^{ -14} g as compared to 10^{ -13} to 10^{-11} g). Consequently, ETA LEAFS allows elemental analysis to be done over a wider range of concentrations with less dilution steps. Thallium was accurately determined in biological samples by ETA LEAFS at amounts five to one hundred times below the ETA AAS detection limit. ETA AAS and ETA LEAFS were compared for the determination of lead and manganese, and in general, the accuracies and precisions of ETA AAS were the same, with typical precisions between 3% and 6%. Fluorine was determined using laser excited molecular fluorescence spectrometry (LEMOFS) in an ETA. Molecular fluorescence from magnesium fluoride was collected, and the detection limit of 0.3 pg fluorine was two to six orders of magnitude more sensitive than other methods commonly used for the determination of fluorine. Significant interferences from ions were observed, but the sensitivity was high enough that fluorine could be determined in freeze dried urine SRMs by diluting the samples by a factor of one hundred to remove the interferences. Laser enhanced ionization (LEI) in an ETA was used for the determination of metals. For thallium, indium

  19. Electromagnetic radiations from laser interaction with gas-filled Hohlraum (United States)

    Yang, Ming; Yang, Yongmei; Li, Tingshuai; Yi, Tao; Wang, Chuanke; Liu, Shenye; Jiang, Shaoen; Ding, Yongkun


    The emission of intensive electromagnetic pulse (EMP) due to laser-target interactions at the ShenGuang-III laser facility has been evaluated by probes. EMP signals measured using the small discone antennas demonstrated two variation trends including a bilateral oscillation wave and a unilateral oscillation wave. The new trend of unilateral oscillation could be attributed to the hohlraum structure and low-Z gas in the hohlraum. The EMP waveform showed multiple peaks when the gas-filled hohlraum was shot by the high-power laser. Comparing the EMP signals with the verification of stimulated Raman scattering energy and hard x-ray energy spectrum, we found that the intensity of EMP signals decreased with the increase of the hohlraum size. The current results are expected to offer preliminary information to study physical processes on laser injecting gas-filled hohlraums in the National Ignition Facility implementation.

  20. Oxygen assisted interconnection of silver nanoparticles with femtosecond laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, H.; Zhou, Y., E-mail: [Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Duley, W. W. [Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)


    Ablation of silver (Ag) nanoparticles in the direction of laser polarization is achieved by utilizing femtosecond laser irradiation in air at laser fluence ranging from ∼2 mJ/cm{sup 2} to ∼14 mJ/cm{sup 2}. This directional ablation is attributed to localized surface plasmon induced localized electric field enhancement. Scanning electron microscopy observations of the irradiated particles in different gases and at different pressures indicate that the ablation is further enhanced by oxygen in the air. This may be due to the external heating via the reactions of its dissociation product, atomic oxygen, with the surface of Ag particles, while the ablated Ag is not oxidized. Further experimental observations show that the ablated material re-deposits near the irradiated particles and results in the extension of the particles in laser polarization direction, facilitating the interconnection of two well-separated nanoparticles.

  1. Laser Refractography

    CERN Document Server

    Rinkevichyus, B.S; Raskovskaya, I.L


    This book describes the basic principles of laser refractography, a flexible new diagnostic tool for measuring optically inhomogeneous media and flows. Laser refractography is based on digital imaging and computer processing of structured laser beam refraction (SLR) in inhomogeneous transparent media. Laser refractograms provide both qualitative and quantitative measurements and can be used for the study of fast and transient processes. In this book, the theoretical basis of refractography is explored in some detail, and experimental setups are described for measurement of transparent media using either 2D (passed radiation) or 3D (scattered radiation) refractograms. Specific examples and applications are discussed, including visualization of the boundary layer near a hot or cold metallic ball in water, and observation of edge effects and microlayers in liquids and gases. As the first book to describe this new and exciting technique, this monograph has broad cross-disciplinary appeal and will be of interest t...

  2. The role of laser radiation therapy in maxillary sinusitis


    Isser, D. K.; Sett, S.; Saha, B.P.


    Efficacy of prescribed noninvasive & invasive types of treatment of maxillary sinusitis has been compared with low-dose LASER therapy (LLT). After going through the observations of different authors on the therapeutic role of LLT (GaA1AS-LASER) in non-ENT infective diseases, its use in ‘sinusitis’ has been adjudged. Such type of study-report has not been found by us in the literatures, available to us.

  3. Influence of laser radiation on acceleration of postextraction wound healing (United States)

    Grzesiak-Janas, Grazyna; Kobos, Jozef


    The investigations included 50 patients who were subjected to extraction of two adjacent teeth because of chronic periodontal ligament inflammation using 2 percent lignocaine as an anaesthetic agent. One postextraction wound was irradiated with laser light, whereas the second one was left to be healed in a natural way. The use of laser beam accelerates postextraction wound healing on the basis of clinical and cytologic evaluation.

  4. Atmospheric propagation of high power laser radiation at different weather conditions


    Pargmann, Carsten; Hall, Thomas; Duschek, Frank; Handke, Jürgen


    Applications based on the propagation of high power laser radiation through the atmosphere are limited in range and effect, due to weather dependent beam wandering, beam deterioration, and scattering processes. Security and defense related application examples are countermeasures against hostile projectiles and the powering of satellites and aircrafts. For an examination of the correlations between weather condition and laser beam characteristics DLR operates at Lampoldshausen a 130 m long fr...

  5. Third harmonic generation of CO2 laser radiation in AgGaSe2 crystal

    Indian Academy of Sciences (India)

    ... for second harmonic and third harmonic generations are 6.3% and 2.4% respectively with the input fundamental pump power density of 5.9 MW/cm2 only. The wavelength of the fundamental CO2 laser radiation used for the generation of harmonics is 10.6 m, (20) line. A compact TEA CO2 laser source has been built in ...

  6. BRIEF COMMUNICATIONS: Pulse-periodic iodine photodissociation laser pumped with radiation from magnetoplasma compressors (United States)

    Kashnikov, G. N.; Orlov, V. K.; Panin, A. N.; Piskunov, A. K.; Reznikov, Vladimir A.


    A study was made of the characteristics of an iodine photodissociation laser pumped by radiation emitted from magnetoplasma compressors. A closed system for circulating the working gas C3F7I was employed in this laser. Pulse-periodic operation with an interval of 1 min between the pulses was achieved; the output energy was 110 J and the pulse duration was 30 μ sec.

  7. The effect of near-infrared MLS laser radiation on cell membrane structure and radical generation. (United States)

    Kujawa, Jolanta; Pasternak, Kamila; Zavodnik, Ilya; Irzmański, Robert; Wróbel, Dominika; Bryszewska, Maria


    The therapeutic effects of low-power laser radiation of different wavelengths and light doses are well known, but the biochemical mechanism of the interaction of laser light with living cells is not fully understood. We have investigated the effect of MLS (Multiwave Locked System) laser near-infrared irradiation on cell membrane structure, functional properties, and free radical generation using human red blood cells and breast cancer MCF-4 cells. The cells were irradiated with low-intensity MLS near-infrared (simultaneously 808 nm, continuous emission and 905 nm, pulse emission, pulse-wave frequency, 1,000 or 2,000 Hz) laser light at light doses from 0 to 15 J (average power density 212.5 mW/cm(2), spot size was 3.18 cm(2)) at 22 °C, the activity membrane bound acetylcholinesterase, cell stability, anti-oxidative activity, and free radical generation were the parameters used in characterizing the structural and functional changes of the cell. Near-infrared low-intensity laser radiation changed the acetylcholinesterase activity of the red blood cell membrane in a dose-dependent manner: There was a considerable increase of maximal enzymatic rate and Michaelis constant due to changes in the membrane structure. Integral parameters such as erythrocyte stability, membrane lipid peroxidation, or methemoglobin levels remained unchanged. Anti-oxidative capacity of the red blood cells increased after MLS laser irradiation. This irradiation induced a time-dependent increase in free radical generation in MCF-4 cells. Low-intensity near-infrared MLS laser radiation induces free radical generation and changes enzymatic and anti-oxidative activities of cellular components. Free radical generation may be the mechanism of the biomodulative effect of laser radiation.

  8. Collisionless dissociation and isotopic enrichment of SF6 using high-powered CO2 laser radiation (United States)

    Gower, M. C.; Billman, K. W.


    Dissociation of S-32F6 and the resultant isotopic enrichment of S-34F6 using high-powered CO2 laser radiation has been studied with higher experimental sensitivity than previously reported. Enrichment factors have been measured as a function of laser pulse number, wavelength, energy and time duration. A geometry independent dissociation cross section is introduced and measured values are presented. Threshold energy densities, below which no dissociation was observed, were also determined.

  9. He-Ne laser radiation in combined therapy of children's bronchial asthma (United States)

    Zhilnikov, Dmitriy V.; Varavva, Andrey S.; Tarasova, Olga N.; Plaksina, Galina V.; Barybin, Vitaliy F.; Khlutkova, Svetlana N.


    In this paper the medical application of He-Ne lasers for the treatment of bronchial asthma is described. Research objective of this work was the development of a treatment method for children with bronchial asthman of heavy and medium-heavy forms, resistant to the base therapy, with the help of low-intensive laser radiation with wave length λ=0,63 μm.

  10. Exposure to laser radiation for creation of metal materials nanoporous structures (United States)

    Murzin, Serguei P.


    Exposure to laser radiation for creation of nanoporous structures in the Cu-Zn alloy was investigated. It was established that exposure to laser pulse-periodic radiation with pulse repetition rate up to 5000 Hz makes it possible to form a nanoporous structure in the near-surface layer. The conditions of increase of area depth of such structures formation up to 40-45 μm were ascertained. The temperature and speed conditions which provide predominant channel-type nanopores formation with width of about 100 nm forming a nanoporous net were determined. This patented technology is a perspective for production of catalysts and microfiltration membranes.

  11. Research on a laser ultrasound method for testing the quality of a nuclear radiation protection structure (United States)

    Zhang, Kuanshuang; Zhou, Zhenggan; Ma, Liyin


    Laser ultrasonics has been investigated for inspecting the quality of a nuclear radiation protection structure. A possibility is proposed to improve the signal to noise ratio (SNR) of a laser ultrasonic inspection system. Then, a nuclear radiation protection structure composed of an AISI 1045 steel sheet connected with a lead alloy sheet by using an epoxy resin adhesive was manufactured with simulated defects. A non-contact laser ultrasonic inspection system, where the measured signals were filtered using a wavelet threshold de-noising method, was established to conduct a series of experiments. The proposed signal processing method can significantly improve the SNR of measured laser ultrasound signals on a rough solid surface. Compared with the SNR of original ultrasonic signals measured in transmission and reflection, the SNR of processed transmitted and reflected signals is improved by 13.8 and 16.6 dB, respectively. Moreover, laser ultrasonic C-scans based on the transmission and pulse-echo method can detect the simulated de-bonding defects, and the relative deviation between the measured sizes and design values is below 9%. Therefore, the laser ultrasonic method combined with effective signal processing can achieve the quantitative characterization of de-bonding defects in nuclear radiation protection structures.

  12. UV and IR laser radiation's interaction with metal film and teflon surfaces (United States)

    Fedenev, A. V.; Alekseev, S. B.; Goncharenko, I. M.; Koval', N. N.; Lipatov, E. I.; Orlovskii, V. M.; Shulepov, M. A.; Tarasenko, V. F.


    The interaction of Xe ([lambda] [similar] 1.73 [mu]m) and XeCl (0.308 [mu]m) laser radiation with surfaces of metal and TiN-ceramic coatings on glass and steel substrates has been studied. Correlation between parameters of surface erosion versus laser-specific energy was investigated. Monitoring of laser-induced erosion on smooth polished surfaces was performed using optical microscopy. The correlation has been revealed between characteristic zones of thin coatings damaged by irradiation and energy distribution over the laser beam cross section allowing evaluation of defects and adhesion of coatings. The interaction of pulsed periodical CO2 ([lambda] [similar] 10.6 [mu]m), and Xe ([lambda] [similar] 1.73 [mu]m) laser radiation with surfaces of teflon (polytetrafluoroethylene—PTFE) has been studied. Monitoring of erosion track on surfaces was performed through optical microscopy. It has been shown that at pulsed periodical CO2-radiation interaction with teflon the sputtering of polymer with formation of submicron-size particles occurs. Dependencies of particle sizes, form, and sputtering velocity on laser pulse duration and target temperature have been obtained.

  13. Enhancement of ultrafast electron photoemission from metallic nano antennas excited by a femtosecond laser pulse

    CERN Document Server

    Gubko, M A; Ionin, A A; Kudryashov, S I; Makarov, S V; Nathala, C S R; Rudenko, A A; Seleznev, L V; Sinitsyn, D V; Treshin, I V


    We have demonstrated for the first time that an array of nanoantennas (central nanotips inside sub-micron pits) on an aluminum surface, fabricated using a specific double-pulse femtosecond laser irradiation scheme, results in a 28-fold enhancement of the non-linear (three-photon) electron photoemission yield, driven by a third intense IR femtosecond laser pulse. The supporting numerical electrodynamic modeling indicates that the electron emission is increased not owing to a larger effective aluminum surface, but due to instant local electromagnetic field enhancement near the nanoantenna, contributed by both the tip's lightning rod effect and the focusing effect of the pit as a microreflector and annular edge as a plasmonic lens.

  14. Noble metal nanoparticles on quartz supports as SERS substrates excited by a diode laser system for SERDS (United States)

    Ossig, Robert; Kwon, Yong-Hyok; Kronfeldt, Heinz-Detlef; Träger, Frank; Hubenthal, Frank


    In this contribution we present surface enhanced Raman scattering (SERS) measurements of pyrene as a function of the surface plasmon resonance position of noble metal nanoparticle ensembles, which served as SERS substrates. The noble metal nanoparticle ensembles were prepared under ultrahigh vacuum (UHV) conditions by Volmer-Weber growth on quartz substrates. For the SERS measurements, the substrates were mounted in a flow-through cell as part of the optical Raman set-up. A diode laser microsystem with an emission wavelength of 488 nm was used. The system generates two slightly different emission wavelengths (Δλ ~ 0.3 nm) with a spectral width of ~ 10 pm and an optical power of ~ 10 mW. With this set-up SERS as well as shifted excitation Raman difference spectroscopy (SERDS) can be carried out. For trace analysis of pyrene in water SERS/SERDS experiments were accomplished as a function of molecule concentration and spectral position of the plasmon resonance. The best results with a limit of detection of 2 nmol of pyrene were obtained with a nanoparticle ensemble with a plasmon resonance in the vicinity of the excitation wavelength of λ = 488 nm. If the plasmon resonance frequency is slightly off-resonance the detection limit is significantly lower. The latter results are discussed in more detail and we will demonstrate that the morphology and the optical properties of the SERS substrates crucially influence the LOD.

  15. Single photon infrared emission spectroscopy: a study of IR emission from UV laser excited PAHs between 3 and 15 micrometers (United States)

    Cook, D. J.; Schlemmer, S.; Balucani, N.; Wagner, D. R.; Harrison, J. A.; Steiner, B.; Saykally, R. J.


    Single-photon infrared emission spectroscopy (SPIRES) has been used to measure emission spectra from polycyclic aromatic hydrocarbons (PAHs). A supersonic free-jet expansion has been used to provide emission spectra of rotationally cold and vibrationally excited naphthalene and benzene. Under these conditions, the observed width of the 3.3-micrometers (C-H stretch) band resembles the bandwidths observed in experiments in which emission is observed from naphthalene with higher rotational energy. To obtain complete coverage of IR wavelengths relevant to the unidentified infrared bands (UIRs), UV laser-induced desorption was used to generate gas-phase highly excited PAHs. Lorentzian band shapes were convoluted with the monochromator-slit function in order to determine the widths of PAH emission bands under astrophysically relevant conditions. Bandwidths were also extracted from bands consisting of multiple normal modes blended together. These parameters are grouped according to the functional groups mostly involved in the vibration, and mean bandwidths are obtained. These bandwidths are larger than the widths of the corresponding UIR bands. However, when the comparison is limited to the largest PAHs studied, the bandwidths are slightly smaller than the corresponding UIR bands. These parameters can be used to model emission spectra from PAH cations and cations of larger PAHs, which are better candidate carriers of the UIRs.

  16. Quantized form factor shift in the presence of free electron laser radiation

    CERN Document Server

    Fratini, F; Hayrapetyan, A G; Jänkälä, K; Amaro, P; Santos, J P


    In electron scattering, the target form factors contribute significantly to the diffraction pattern and carry information on the target electromagnetic charge distribution. Here we show that the presence of electromagnetic radiation, as intense as currently available in Free Electron Lasers, shifts the dependence of the target form factors by a quantity that depends on the number of photons absorbed or emitted by the electron as well as on the parameters of the electromagnetic radiation. As example, we show the impact of intense ultraviolet and soft X-ray radiation on elastic electron scattering by Ne-like Argon ion and by Xenon atom. We find that the shift brought by the radiation to the form factor is in the order of some percent. Our results may open up a new avenue to explore matter with the assistance of laser.

  17. Enhancement of resonant absorption through excitation of SPR (United States)

    Giulietti, Danilo; Calcagno, L.; Curcio, Alessandro; Cutroneo, M.; Galletti, Mario; Skala, J.; Torrisi, L.; Zimbone, M.


    In this experiment the absorption of the laser radiation impinging on polymeric films with Au nanoparticles implanted in surface was studied. By varying the polarization and the incidence angle of the laser radiation on target, the role in the laser absorption of both excitation of surface plasmons and excitation of electronic plasma waves at critical density through resonant absorption was highlighted. In conditions of p-polarized laser irradiations at 1015 W /cm2 intensity, resonant absorption can be induced in films enhancing proton and ion acceleration. Plasma on-line diagnostics is based on SiC detectors. Measurements of kinetic energy of accelerated ions indicate a significant increment using p-polarized laser light with respect to no-polarized light irradiation.

  18. Optical Quantification of Harmonic Acoustic Radiation Force Excitation in a Tissue-Mimicking Phantom. (United States)

    Suomi, Visa; Edwards, David; Cleveland, Robin


    Optical tracking was used to characterize acoustic radiation force-induced displacements in a tissue-mimicking phantom. Amplitude-modulated 3.3-MHz ultrasound was used to induce acoustic radiation force in the phantom, which was embedded with 10-μm microspheres that were tracked using a microscope objective and high-speed camera. For sine and square amplitude modulation, the harmonic components of the fundamental and second and third harmonic frequencies were measured. The displacement amplitudes were found to increase linearly with acoustic radiation force up to 10 μm, with sine modulation having 19.5% lower peak-to-peak amplitude values than square modulation. Square modulation produced almost no second harmonic, but energy was present in the third harmonic. For the sine modulation, energy was present in the second harmonic and low energy in the third harmonic. A finite-element model was used to simulate the deformation and was both qualitatively and quantitatively in agreement with the measurements. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  19. The radiative decays of excited states of transition elements located inside and near core-shell nanoparticles (United States)

    Pukhov, Konstantin K.


    Here we discuss the radiative decays of excited states of transition elements located inside and outside of the subwavelength core-shell nanoparticles embedded in dielectric medium. Based on the quantum mechanics and quantum electrodynamics, the general analytical expressions are derived for the probability of the spontaneous transitions in the luminescent centers (emitter) inside and outside the subwavelength core-shell nanoparticle. Obtained expressions holds for arbitrary orientation of the dipole moment and the principal axes of the quadrupole moment of the emitter with respect to the radius-vector r connecting the center of the emitter with the center of the nanoparticle. They have simple form and show how the spontaneous emission in core-shell NPs can be controlled and engineered due to the dependence of the emission rates on core-shell sizes, radius-vector r and permittivities of the surrounding medium, shell, and core.

  20. Shear bond strength after Er:YAG laser radiation conditioning of enamel and dentin (United States)

    Dostalova, Tatjana; Jelinkova, Helena; Dolezalova, Libuse; Kubelka, Jiri; Prochazka, Stanislav; Hamal, Karel; Krejsa, Otakar


    This study compares bond shear strength between hard dental tissues and composite resin filling material after a classical acid etching treatment procedure and Er:YAG laser surface conditioning. The retention of composite resin was evaluated for three cases: (1) the flat dental substrate without any conditioning, (2) the classical drilling machine prepared surface with acid etching and (3) the Er:YAG laser conditioning of enamel and dentin. None significant differences between bond shear strength of the classical drilling machine prepared surface with acid etching in comparison with the laser radiation conditioning were found.

  1. Influence of laser radiation on the growth and development of seeds of agricultural plants (United States)

    Grishkanich, Alexander; Zhevlakov, Alexander; Polyakov, Vadim; Kascheev, Sergey; Sidorov, Igor; Ruzankina, Julia; Yakovlev, Alexey; Mak, Andrey


    The experimental results presented in this study focused on the study of biological processes caused by exposure to the coating layers of the laser green light seed (λ = 532 nm) range for the larch, violet (λ = 405 nm) and red (λ = 640 nm) for spruce. Spend a series of experiments to study the dependence of crop seed quality (spruce and larch from the pine family) from exposure to laser radiation under different conditions. In all the analyzed groups studied seed germination and growth of seedlings exposed to laser exposure, compared with the control group. The results showed that the higher percentage of germination than seeds of the control group.

  2. Microprocessing of human hard tooth tissues surface by mid-infrared erbium lasers radiation (United States)

    Belikov, Andrey V.; Shatilova, Ksenia V.; Skrypnik, Alexei V.


    A new method of hard tooth tissues laser treatment is described. The method consists in formation of regular microdefects on tissue surface by mid-infrared erbium laser radiation with propagation ratio M2laser microprocessing). Proposed method was used for preparation of hard tooth tissues surface before filling for improvement of bond strength between tissues surface and restorative materials, microleakage reduction between tissues surface and restorative materials, and for caries prevention as a result of increasing microhardness and acid resistance of tooth enamel.

  3. [Photomodification of blood by laser and ultraviolet radiation: a comparative study]. (United States)

    Zalesskaia, G A; Kalosha, I I


    The efficiency of in vivo blood irradiation by a laser light source (λ = 632.8 and 670 nm) and a mercury lamp (UV light, λ = 254 nm) was compared. Absorption spectra, gas content, oxyhemoglobin content, hemoglobin oxygen saturation, concentrations of lactate and glucose were studied for both irradiated and control samples. Hemoglobin was assumed to be the primary photoacceptor of light radiation for the indicated wavelengths. No substantial differences have been found between the effects of laser and non-laser irradiation. We conclude that the biological impact of the procedure is related to photoinduced changes in hemoglobin oxygen saturation.

  4. Acoustic-wave generation in the process of CO2-TEA-laser-radiation interaction with metal targets in air (United States)

    Apostol, Ileana; Teodorescu, G.; Serbanescu-Oasa, Anca; Dragulinescu, Dumitru; Chis, Ioan; Stoian, Razvan


    Laser radiation interaction with materials is a complex process in which creation of acoustic waves or stress waves is a part of it. As a function of the laser radiation energy and intensity incident on steel target surface ultrasound signals were registered and studied. Thermoelastic, ablation and breakdown mechanisms of generation of acoustic waves were analyzed.

  5. The contribution of electronically excited states to the radiation chemistry of organic systems

    Energy Technology Data Exchange (ETDEWEB)

    Lipsky, S.


    The photocurrent from anthracene in 2,2,4-trimethylpentane, 2.2- dimethylbutane, cyclohexane, cyclopentane, and tetramethylsilane has been studied as a function of excitation energy from the ionization threshold to the onset of strong solvent absorption. The fluroescence from solutions of hexafluorobenzene in cyclopentane, 2,2,4-trimethylpentane, 2,2-dimethylbutane and tetramethylsilane irradiated with {beta}-particles has been studied as a function of the hexafluorobenzene concentration from c = 10{sup {minus}3}-10{sup {minus}1} M. The data are analyzed to permit extraction of the geminate ion-pair scavenging probability. The absorption of 160 nm light by cyclohexane in mixtures of cyclohexane, benzene and tetraphenylmethylenediamine results in an emission spectrum consisting of the simultaneous fluorescence from all three components. A mechanism for the development of this spectrum and its dependence on benzene concentration is constructed and shown to be quantitatively consistent with the results of independent measurements on the separate components. 55 refs.

  6. Using radiation intensity dependence on excitation level for the analysis of surface plasmon resonance effect on ZnO luminescence (United States)

    Rumyantsev, S. I.; Tarasov, A. P.; Briskina, C. M.; Ryzhkov, M. V.; Markushev, V. M.; Lotin, A. A.


    For the analysis of ZnO luminescence the system of rate equations (SRE) was proposed. It contains a set of parameters that characterizes processes participating in luminescence: zone-zone excitation, excitons formation and recombination, formation and disappearance of photons and surface plasmons (SP). It is shown that experimental ZnO microstructure radiation intensity dependence on photoexcitation level can be approximated by using SRE. Thus, the values of these parameters can be estimated and used for luminescence analysis. This approach was applied for the analysis of ZnO microfilms radiation with different thickness of Ag island film covering. It was revealed that the increase of cover thickness leads to the increase of losses and decrease of probability of photons to SP conversion. In order to take into account visible emission, rate equations for levels populations in band-gap and for corresponding photons and SP were added to SRE. By using such SRE it is demonstrated that the form of visible luminescence intensity dependence on excitation level (P) like P1/3, as obtained elsewhere [1], is possible only in case of donor-acceptor pairs existence. The proposed approach was applied for consideration of experimental results obtained in [5-8] taking into account their interpretation of these results based on assumption about transfer of electrons from defect level in ZnO band-gap to metal and then to conduction band in ZnO. Results of performed calculations using modified SRE revealed that effects observed in these papers can exist under only low pumping level. This result will be experimentally checked later.

  7. Experimental observation of strong radiation reaction in the field of an ultra-intense laser (United States)

    Sarri, G.; Poder, K.; Tamburini, M.; di Piazza, A.; Keitel, C. H.; Zepf, M.


    Describing radiation reaction in an electromagnetic field is one of the most fundamental outstanding problems in electrodynamics. It consists of determining the dynamics of a charged particle fully taking into account self-forces (loosely referred to as radiation reaction) resulting from the radiation fields generated by the particle whilst it is accelerated. Radiation reaction has only been invoked to explain the radiative properties of powerful astrophysical objects, such as pulsars and quasars. From a theoretical standpoint, this phenomenon is subject of fervent debate and this impasse is worsened by the lack of experimental data, due to extremely high fields required to trigger these effects. Here, we report on the first experimental evidence of strong radiation reaction during the interaction of an ultra-relativistic electron beam with an intense laser field, beyond a purely classical description.

  8. Influence of the dentin surface properties on the laser radiation absorption (United States)

    Chmelickova, Hana; Sebestova, Hana; Hiklova, Helena; Rihakova, Lenka


    Research of the optical radiation interaction with human tooth tissues has started early after the first laser construction. Absorptivity of the particular tissue is dependent on the wavelength, thus CO2, Er:YAG and Nd:YAG lasers were used in many experimental works all over the world. Near infrared radiation of the pulsed Nd:YAG laser was found to be suitable for dentine hypersensitivity treatment by sealing of the open tubules with melted and re-solidified dentin. Series of experiments were performed to find suitable process parameters in the laser laboratory equipped with the industrial pulsed Nd:YAG laser system. Tooth samples were prepared and classified into five groups according to their different degree of the surface grinding and polishing. Two types of antireflective agents, erythrosine and black ink, were applied on the samples surfaces. Coated samples and reference ones without any agents were treated with a set of increasing pulse energy values. Pulse frequency, pulse length, laser beam diameter on the sample surface and relative speed remained constant. Lines of the melted spots were displayed by confocal microscope; surface profiles were scanned by contact profilometer. Dimensions of the dentine melted spots were extracted from the measured data and their dependence on the laser pulse energy, degree of the surface grinding and type of antireflective agent were evaluated.

  9. Cooling and Laser-Induced Fluorescence of Electronically-Excited He2 in a Supersonic Microcavity Plasma Jet (United States)

    Su, Rui; Mironov, Andrey; Houlahan, Thomas, Jr.; Eden, J. Gary; LaboratoryOptical Physics; Engineering Team


    Laser-induced fluorescence (LIF) resulting from transitions between different electronic states of helium dimers generated within a microcavity plasma jet was studied with rotational resolution. In particular, the d3Σu+ , e3Πg and f3Σu+ states, all having electronic energies above 24 eV, are populated by a microplasma in 4 bar of helium gas and rotationally cooled through supersonic expansion. Analysis of two dimensional maps (spectrograms) of dimer emission spectra as a function of distance from the nozzle orifice indicates collisional coupling during the expansion between the lowest rotational levels of the e3Πg , f3Σu+ states and high rotational levels (around N=11) of the d3Σu+ state (all of which are in the v = 0 vibrational state). In an attempt to verify the coupling, a scanning dye laser (centered near 596 nm) pumps the b3Πg -> f3Σu+ transition of the molecule several hundred micrometers downstream of the nozzle. As a result, the emission intensities of relevant rotational lines are observed to be enhanced. This research shows the potential of utilizing microcavity plasma jets as a tool to study and manipulate the collisional dynamics of highly-excited diatomic molecules.

  10. APPLICATIONS OF LASERS AND OTHER TOPICS IN LASER PHYSICS AND TECHNOLOGY: Influence of atmospheric fluctuations of the induced temperature on the characteristics of laser radiation (United States)

    Banakh, Viktor A.; Smalikho, I. N.


    The expression for the function representing the second-order mutual coherence of a laser beam propagating in a turbulent atmosphere under thermal self-interaction conditions is derived in the aberration-free approximation. An analysis is made of the width of a beam, its wind refraction, and the radius of coherence as a function of the initial coherence of the radiation, of conditions of diffraction on the transmitting aperture, and of fluctuations of the wind velocity. It is shown that on increase in the power the coherence radius of cw laser radiation first increases because of thermal defocusing and then decreases due to the appearance (because of fluctuations of the wind velocity) of induced temperature inhomogeneities in air in the beam localization region. The conditions under which fluctuations of the induced temperature have a significant influence on the coherence of the radiation are determined.

  11. Plastic hollow waveguides: properties and possibilities as a flexible radiation delivery system for CO2-laser radiation. (United States)

    Cossmann, P H; Romano, V; Spörri, S; Altermatt, H J; Croitoru, N; Frenz, M; Weber, H P


    One significant inconvenience of the CO2 laser is the lack of flexible fibers essential for endoscopic applications. The goal of this study is to test the feasibility of hollow waveguides in view of a practical use in medicine. Various types of plastic hollow waveguides for flexible delivery of CO2 laser radiation were examined. The transmission losses, divergence angle, damage threshold, and input and output beam profiles were determined. The interaction process between radiation transmitted through these guides with soft as well as hard tissues was studied. Plastic hollow waveguides can transmit high power (up to 50 W) with low losses (straight guide 1 dB/m) even through bendings. The divergence angle is laser beam. The results of this study show good cutting quality and durability of these flexible plastic hollow waveguides, which render possible to deliver CO2 radiation in the power range needed for most surgical applications with affordable transmission losses. Plastic hollow waveguides are, therefore, a real alternative to replace the mirror arms.

  12. Chirality Emergence in Thin Solid Films of Amino Acids by Polarized Light from Synchrotron Radiation and Free Electron Laser

    Directory of Open Access Journals (Sweden)

    Mashahiro Adachi


    Full Text Available One of the most attractive hypothesis for the origin of homochirality in terrestrial bioorganic compounds is that a kind of “chiral impulse” as an asymmetric excitation source induced asymmetric reactions on the surfaces of such materials such as meteorites or interstellar dusts prior to the existence of terrestrial life (Cosmic Scenario. To experimentally introduce chiral structure into racemic films of amino acids (alanine, phenylalanine, isovaline, etc., we irradiated them with linearly polarized light (LPL from synchrotron radiation and circularly polarized light (CPL from a free electron laser. After the irradiation, we evaluated optical anisotropy by measuring the circular dichroism (CD spectra and verified that new Cotton peaks appeared at almost the same peak position as those of the corresponding non-racemic amino acid films. With LPL irradiation, two-dimensional anisotropic structure expressed as linear dichroism and/or linear birefringence was introduced into the racemic films. With CPL irradiation, the signs of the Cotton peaks exhibit symmetrical structure corresponding to the direction of CPL rotation. This indicates that some kinds of chiral structure were introduced into the racemic film. The CD spectra after CPL irradiation suggest the chiral structure should be derived from not only preferential photolysis but also from photolysis-induced molecular structural change. These results suggest that circularly polarized light sources in space could be associated with the origin of terrestrial homochirality; that is, they would be effective asymmetric exciting sources introducing chiral structures into bio-organic molecules or complex organic compounds.

  13. State-selective electron transfer and ionization in collisions of highly charged ions with ground-state Na(3s) and laser-excited Na*(3p)

    NARCIS (Netherlands)

    Blank, I.; Otranto, S.; Meinema, C.; Olson, R. E.; Hoekstra, R.


    Single electron transfer and ionization in collisions of N5+ and Ne8+ with ground state Na(3s) and laser excited Na*(3p) are investigated both experimentally and theoretically at collision energies from 1 to 10 keV/amu, which includes the classical orbital velocity of the valence electron.

  14. Infrared absorption, laser excitation and crystal-field analyses of the C-4v symmetry centre in KY3F10 doped with Pr3+

    NARCIS (Netherlands)

    Wells, J. P. R.; Yamaga, M.; Han, T. P. J.; Gallagher, H. G.


    We report a comprehensive spectroscopic study of KY3F10 doped with trivalent praseodymium. Employing both infrared absorption and laser excited fluorescence spectroscopy, we have constructed an energy level scheme of 39 crystal-field states. A C-4v symmetry, conventional crystal-field analysis can

  15. Effects of femtosecond laser radiation on blood cell suspensions (United States)

    Gening, Tatyana; Sysolyatin, Aleksey; Abakumova, Tatyana; Arslanova, Dinara; Voronova, Olga; Zolotovsky, Igor; Ostatochnikov, Vladimir; Yavtushenko, Marina


    In the present work the effects of high-power femtosecond laser irradiation on a functional condition of red blood cells and neutrophils in vitro have been investigated. The data on parameters of the lipid peroxidation - antioxidants system, hemoglobin level and rigidity of red blood cell membranes testify destabilization of the membranes under the influence of the given laser. The study of phagocytic activity, anaerobic and aerobic metabolism of neutrophils, and rigidity of their membranes allows to suppose the dose-dependent effect to be stimulating.

  16. Formation of pores in Ge single crystal by laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Medvid' , A. [Laboratory of Semiconductor Physics, Riga Technical University, LV-1048, 14 Azenes Street, Riga (Latvia)]. E-mail:; Mychko, A. [Laboratory of Semiconductor Physics, Riga Technical University, LV-1048, 14 Azenes Street, Riga (Latvia); Krivich, A. [Laboratory of Semiconductor Physics, Riga Technical University, LV-1048, 14 Azenes Street, Riga (Latvia); Onufrijevs, P. [Laboratory of Semiconductor Physics, Riga Technical University, LV-1048, 14 Azenes Street, Riga (Latvia)


    Formation of a porous structure on the surface of Ge single crystals by pulsed YAG:Nd laser irradiation at the intensity of {approx}25 MW/cm{sup 2} is reported. An increase of surface recombination velocity on the irradiated surface by a factor of 100 is observed and explained by increase of the geometric area of the surface due to formation of pores. The latter is attributed to inhomogeneous pressure of a pulsed laser beam on the melting irradiated surface of the crystal.

  17. Laser-induced gratings in the gas phase excited via Raman-active transitions

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, D.N. [General Physics Inst., Russian Academy of Sciences, Moscow (Russian Federation); Bombach, R.; Hemmerling, B.; Hubschmid, W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)


    We report on a new time resolved coherent Raman technique that is based on the generation of thermal gratings following a population change among molecular levels induced by stimulated Raman pumping. This is achieved by spatially and temporally overlapping intensity interference patterns generated independently by two lasers. When this technique is used in carbon dioxide, employing transitions which belong to the Q-branches of the {nu}{sub 1}/2{nu}{sub 2} Fermi dyad, it is possible to investigate molecular energy transfer processes. (author) 2 figs., 10 refs.

  18. [Cleavage of DNA fragments induced by UV nanosecond laser excitation at 193 nm]. (United States)

    Vtiurina, N N; Grokhovskiĭ, S L; Filimonov, I V; Medvedkov, O I; Nechipurenko, D Iu; Vasil'ev, S A; Nechipurenko, Iu D


    The cleavage of dsDNA fragments in aqueous solution after irradiation with UV laser pulses at 193 nm has been studied. Samples were investigated using polyacrylamide gel electrophoresis. The intensity of damage of particular phosphodiester bond after hot alkali treatment was shown to depend on the base pair sequence. It was established that the probability of cleavage is twice higher for sites of DNA containing two or more successively running guanine residues. A possible mechanism of damage to the DNA molecule connected with the migration of holes along the helix is discussed.

  19. Generation of quasi-monochromatic beams of accelerated electrons during interaction of weak-contrast intense femtosecond laser radiation with a metal-foil edge

    Energy Technology Data Exchange (ETDEWEB)

    Malkov, Yu A; Stepanov, A N; Yashunin, D A; Pugachev, L P; Levashov, P R; Andreev, N E; Andreev, Aleksandr A


    The formation of monoenergetic beams of accelerated electrons by focusing femtosecond laser radiation with an intensity of 2 Multiplication-Sign 10{sup 17} W cm{sup -2} onto an edge of aluminium foil has been experimentally demonstrated. The electrons had energy distributions peaking in the range from 0.2 to 0.8 MeV and an energy spread less than 20 %. The acceleration mechanism related to the generation of a plasma wave as a result of self-modulation instability of the laser pulse in the subcritical plasma formed the prepulse of the laser system (arriving 10 ns before the main pulse) is considered. Onedimensional PIC simulation of the interaction between the laser radiation and plasma with a concentration of 5 Multiplication-Sign 10{sup 19} cm{sup -3} showed that effective excitation of a plasma wave, as well as the trapping and acceleration of the electron beam with an energy on the order of 1 MeV, may occur in the presence of inhomogeneities in the density at the plasma boundary and in the temporal shape of the beam. (extreme light fields and their applications)

  20. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Characteristics of the evolution of a plasma formed by cw and pulse-periodic CO2 laser radiation in various gases (United States)

    Kanevskiĭ, M. F.; Stepanova, M. A.


    An investigation was made of the interaction between high-power cw and pulse-periodic CO2 laser radiation and a low-threshold optical breakdown plasma near a metal surface. Characteristics of the breakdown plasma were studied as a function of the experimental conditions. A qualitative analysis was made of the results using a simple one-dimensional model for laser combustion waves.

  1. Plasmon excitation and electron emission of a carbon nanotube under a linearly polarized laser: A real-time first-principles study (United States)

    Uchida, Kazuki; Watanabe, Kazuyuki


    We study the properties of electron excitation and emission of a finite carbon nanotube (CNT) under a linearly polarized femtosecond laser using real-time time-dependent density-functional theory. We find a plasmon resonance in the near-infrared region of the optical absorption spectrum that is highly sensitive to the laser polarization direction. The laser polarization direction dependence of the plasmon excitation obtained in the present study is consistent with the properties of polarized optical absorption observed in experiments. In electron emission that occurs subsequent to electronic excitation, the yield of emitted electrons also shows a laser polarization direction dependence, and the kinetic energy spectrum of the emitted electrons is broadened in the high-energy regime due to the electron acceleration caused by plasmon-induced electric-field enhancement. The findings of the present study are of crucial importance for understanding the laser-CNT interaction, which is a prerequisite for applications of CNTs in electron emitters, nanodevices, and optoelectronic components and sensors.

  2. Elastic and magnetic dynamics of nanomagnet-ordered arrays impulsively excited by subpicosecond laser pulses. (United States)

    Comin, A; Giannetti, C; Samoggia, G; Vavassori, P; Grando, D; Colombi, P; Bontempi, E; Depero, L E; Metlushko, V; Ilic, B; Parmigiani, F


    This Letter reports on the first observation of elastic and magnetic dynamics of ordered arrays of permalloy nanodots excited by low-intensity 120 fs light pulses. The first order of the diffraction pattern, generated by the probe beam in a pump-probe configuration, is used for time-resolved reflectivity and time-resolved magneto-optical Kerr effect measurements. The nonadiabatical absorption of the pump triggers an acoustic standing wave, detected by the reflected probe signal, with a frequency related to the array wave vector. Instead, the magneto-optical signal exhibits, on the nanosecond time scale, the signature of the heat-exchange diffusion processes. In addition, a clear oscillation of the magnetic signal, at a frequency close to the frequency of the acoustic wave, is unambiguously detected. Finally, the interplay between the elastic and magnetic dynamics is analyzed and interpreted.

  3. Risks induced by laser radiation; Risques induits par le rayonnement laser

    Energy Technology Data Exchange (ETDEWEB)

    Courant, D. [CEA Fontenay-aux-Roses, 92 (France). Dept. de Radiobiologie et de Radiopathologie


    The use of lasers is often dangerous because of the emitted power, the wave length, the conduction system(optical fiber, wave guide, mirrors) and the use conditions. The safety notion involves the precise knowledge of materials, the biological effects in function of laser emission parameters, the knowledge of protection standards, the observance of use rules and the personnel training. This chapter treats the risks induced by the beam. It gives the different biological effects induced by the laser beam, at the eye and skin levels that are at the origin of exposure limits and the lasers classification recommended by the protection standards. (N.C.)

  4. Testing relativity again, laser, laser, laser, laser

    NARCIS (Netherlands)

    Einstein, A.


    laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser,

  5. Reactions of electronically excited boron atoms. Quenching rate constants and the radiative lifetime of the 4p 2P state (United States)

    Yang, Xuefeng; Dagdigian, Paul J.


    Collisional quenching and radiative decay of the 4p 2P level of the boron atom has been studied in a cell experiment, in which B atoms are prepared by 266 nm multiphoton dissociation of BBr 3 and the 4p 2P level is prepared by sequential 2-photon absorption through the 3s 2S level. A radiative lifetime of 360 ± 50 ns is derived for B (4p 2P) by extrapolation of the measured decay rates versus BBr 3 partial pressure in several Torr helium buffer gas. Bimolecular quenching rate constants were also determined for a number of atomic and molecular species from the dependence of the B (4p 2P) decay rate on the quencher gas partial pressure. The quenching rate constants for the molecular species were quite large (≈(1-2)×10 -9 molecule -1 cm 3 s -1), presumably reflecting the small B (4p 2P) ionization potential and the rapid removal of the excited state by chemical reaction.

  6. The role of radiation transport in the thermal response of semitransparent materials to localized laser heating

    Energy Technology Data Exchange (ETDEWEB)

    Colvin, Jeffrey [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Shestakov, Aleksei [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Stolken, James [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Vignes, Ryan [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)


    Lasers are widely used to modify the internal structure of semitransparent materials for a wide variety of applications, including waveguide fabrication and laser glass damage healing. The gray diffusion approximation used in past models to describe radiation cooling is not adequate for these materials, particularly near the heated surface layer. In this paper we describe a computational model based upon solving the radiation transport equation in 1D by the Pn method with ~500 photon energy bands, and by multi-group radiationdiffusion in 2D with fourteen photon energy bands. The model accounts for the temperature-dependent absorption of infrared laser light and subsequent redistribution of the deposited heat by both radiation and conductive transport. We present representative results for fused silica irradiated with 2–12 W of 4.6 or 10.6 µm laser light for 5–10 s pulse durations in a 1 mm spot, which is small compared to the diameter and thickness of the silica slab. Furthermore, we show that, unlike the case for bulk heating, in localized infrared laser heatingradiation transport plays only a very small role in the thermal response of silica.

  7. Demonstration of the synchrotron-type spectrum of laser-produced Betatron radiation

    CERN Document Server

    Fourmaux, S; Phuoc, K Ta; Leguay, P M; Payeur, S; Lassonde, P; Gnedyuk, S; Lebrun, G; Fourment, C; Malka, V; Sebban, S; Rousse, A; Kieffer, J C


    Betatron X-ray radiation in laser-plasma accelerators is produced when electrons are accelerated and wiggled in the laser-wakefield cavity. This femtosecond source, producing intense X-ray beams in the multi kiloelectronvolt range has been observed at different interaction regime using high power laser from 10 to 100 TW. However, none of the spectral measurement performed were at sufficient resolution, bandwidth and signal to noise ratio to precisely determine the shape of spectra with a single laser shot in order to avoid shot to shot fluctuations. In this letter, the Betatron radiation produced using a 80 TW laser is characterized by using a single photon counting method. We measure in single shot spectra from 8 to 21 keV with a resolution better than 350 eV. The results obtained are in excellent agreement with theoretical predictions and demonstrate the synchrotron type nature of this radiation mechanism. The critical energy is found to be Ec = 5.6 \\pm 1 keV for our experimental conditions. In addition, th...


    Directory of Open Access Journals (Sweden)

    N. V. Kondratyuk


    Full Text Available Describes nonlinear optical frequency converter of laser radiation based on the two LBO type I crystals allowing to receive pulses of radiation at three wavelengths of 1064 nm, 532 nm and 355 nm with an adjustable pulse energy. For fine adjustment of the output pulse energy used two dual phase plates that change the orientation of the plane of polarization of the two waves in cascade third harmonic generation. Measured the efficiency of the generation of harmonics of the intensity of radiation at 1064 nm.

  9. Second harmonic generation of spectrally broadened femtosecond ytterbium laser radiation in a gas-filled capillary

    Energy Technology Data Exchange (ETDEWEB)

    Didenko, N V; Konyashchenko, Aleksandr V; Kostryukov, P V; Losev, Leonid L; Tenyakov, S Yu


    A 300-fs radiation pulse of an ytterbium laser with a wavelength of 1030 nm and energy of 150 {mu}J were converted to a 15-fs pulse with a wavelength of 515 nm by broadening the emission spectrum in a capillary filled with xenon and by generating the second harmonic in a KDP crystal. The energy efficiency of the conversion was 30 %.

  10. Collisional-radiative calculations for the J = 0‑1 lasing line of neon-like germanium under anisotropic excitation conditions (United States)

    Bentotoche, M. S.; Inal, M. K.; Benmouna, M.


    A new asymmetry parameter characterizing the differences between the polarized π and σ gain components of the soft-x-ray J = 0–1 lasing line of neon-like ions is calculated in the case of Ge22+ assuming an electron distribution which is a weighted sum of an isotropic Maxwellian and a monoenergetic beam. Using a quasi steady-state collisional-radiative model, we determine in the weak amplification regime the relative populations of the upper M = 0 and lower M=0,+/- 1 magnetic sublevels of the lasing line as a function of electron density from 1020 to 2× {10}21 cm‑3. This model includes inelastic and elastic collisional transitions, as well as spontaneous radiative decay between all the 337 M-sublevels arising from the 75 lowest-lying Ge22+ J-levels. The computations were performed for a temperature {T}{{e}} of the Maxwellian component between 1.2× {10}6 and 8× {10}6 K, a kinetic energy E 0 and a fraction f of the beam component in the ranges 1.5{--}20 {keV} and 0.1 % {--}10 % , respectively. The basic atomic data, such as level energies, radiative decay probabilities and inelastic collision strengths, were calculated with the flexible atomic code. However, some modifications of this code were made to get the collision strengths for transitions between M-sublevels due to impact with isotropic electrons as well as due to impact with an electron beam in the case of de-excitation. We find that the newly introduced asymmetry parameter may become significant under certain conditions of electron distribution corresponding to relatively low {T}{{e}} (1.2× {10}6{--}2.5× {10}6 K) and E 0 (3–6 keV). The results reported here may be useful in the evaluation of the polarization degree of the J = 0–1 x-ray laser output from a germanium plasma in the presence of fast directional electrons.

  11. Caries inhibition potential of Er:YAG and Er:YSGG laser radiation (United States)

    Fried, Daniel; Featherstone, John D. B.; Visuri, Steven R.; Seka, Wolf D.; Walsh, Joseph T., Jr.


    Dental hard tissues can be ablated efficiency by (lambda) equals 3 micrometers laser irradiation with minimal subsurface thermal damage. However, the potential of lasers operating in the region of the infrared for caries preventive treatments has not been investigated. In this study, the caries inhibition potential of Er:YAG ((lambda) equals 2.94 micrometers ) and Er:YSGG ((lambda) equals 2.79 micrometers ) laser radiation on dental enamel was evaluated at various irradiation intensities. Pulsed IR radiometry and scanning electron microscopy (SEM) were used to measure the time-resolved surface temperatures during laser irradiation and to detect changes in the surface morphology. The magnitude and temporal evolution of the surface temperature during multiple pulse irradiation of the tissue was dependent on the wavelength, irradiation intensity, and the number of laser pulses. Radiometry and SEM micrographs indicated that ablation was initiated at temperatures of approximately 300 degree(s)C for Er:YAG and 800 degree(s)C for Er:YSGG laser irradiation, well below the melting and vaporization temperatures of the carbonated hydroxyapatite mineral component (m.p. equals 1200 degree(s)C). Nevertheless, there was marked caries inhibition for irradiation intensities below those temperature thresholds, notably 60% and 40% inhibition was achieved after Er:YSGG and Er:YAG laser irradiation, respectively. These results indicate that the Er:YSGG laser can be used effectively for both preventive dental treatments and for hard tissue removal.

  12. Optical quantification of harmonic acoustic radiation force excitation in a tissue-mimicking phantom

    CERN Document Server

    Suomi, Visa; Cleveland, Robin


    Optical tracking was used to characterize acoustic radiation force (ARF) induced displacements in a tissue-mimicking phantom. Amplitude modulated (AM) 3.3 MHz ultrasound was used to induce ARF in the phantom which was embedded with 10 {\\mu}m microspheres that were tracked using a microscope objective and high speed camera. For sine and square AM the harmonic components of the fundamental and second and third harmonic frequencies were measured. The displacement amplitudes were found to increase linearly with ARF up to 10 {\\mu}m with sine modulation having 19.5% lower peak-to-peak amplitude values than square modulation. Square modulation produced almost no second harmonic but energy was present in the third harmonic. For the sine modulation energy was present in the second harmonic and low energy in the third harmonic. A finite element model was used to simulate the deformation and was both qualitatively and quantitatively in agreement with the measurements.

  13. Simulation of intense laser-dense matter interactions. X-ray production and laser absorption

    Energy Technology Data Exchange (ETDEWEB)

    Ueshima, Yutaka; Kishimoto, Yasuaki; Sasaki, Akira [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment; Sentoku, Yasuhiko; Tajima, Toshiki


    The development of short-pulse ultra high intensity lasers will enable us to generate short-pulse intense soft and hard X-rays. Acceleration of an electron in laser field generates intense illuminated located radiation, Larmor radiation, around KeV at 10{sup 18} W/cm{sup 2} with 100 TW and 1 {mu}m wave length laser. The Coulomb interaction between rest ions and relativistic electron generates broad energy radiation, bremsstrahlung emission, over MeV at 10{sup 18} W/cm{sup 2} with the same condition. These intense radiations come in short pulses of the same order as that of the irradiated laser. The generated intense X-rays, Larmor and bremsstrahlung radiation, can be applied to sources of short pulse X-ray, excitation source of inner-shell X-ray laser, position production and nuclear excitation, etc. (author)

  14. Characterization of Tin/Ethylene Glycol Solar Nanofluids Synthesized by Femtosecond Laser Radiation. (United States)

    Torres-Mendieta, Rafael; Mondragón, Rosa; Puerto-Belda, Verónica; Mendoza-Yero, Omel; Lancis, Jesús; Juliá, J Enrique; Mínguez-Vega, Gladys


    Solar energy is available over wide geographical areas and its harnessing is becoming an essential tool to satisfy the ever-increasing demand for energy with minimal environmental impact. Solar nanofluids are a novel solar receiver concept for efficient harvesting of solar radiation based on volumetric absorption of directly irradiated nanoparticles in a heat transfer fluid. Herein, the fabrication of a solar nanofluid by pulsed laser ablation in liquids was explored. This study was conducted with the ablation of bulk tin immersed in ethylene glycol with a femtosecond laser. Laser irradiation promotes the formation of tin nanoparticles that are collected in the ethylene glycol as colloids, creating the solar nanofluid. The ability to trap incoming electromagnetic radiation, thermal conductivity, and the stability of the solar nanofluid in comparison with conventional synthesis methods is enhanced. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Propagation of intense laser radiation through a diffusion flame of burning oil

    Energy Technology Data Exchange (ETDEWEB)

    Gvozdev, S V; Glova, A F; Dubrovskii, V Yu; Durmanov, S T; Krasyukov, A G; Lysikov, A Yu; Smirnov, G V; Pleshkov, V M [State Research Center of Russian Federation ' Troitsk Institute for Innovation and Fusion Research' , Troitsk, Moscow Region (Russian Federation)


    We report the results of measuring the absorption coefficient of radiation from a cw ytterbium fibre single-mode laser with the power up to 1.5 kW by a diffusion flame of oil, burning in the atmosphere air at normal pressure on a free surface. For the constant length (30 mm) and width (30 mm) of the flame and the distance 10 mm between the laser beam axis and the oil surface the dependence of the absorption coefficient, averaged over the flame length, on the mean radiation intensity (varied from 4.5 × 10{sup 3} to 1.2 × 10{sup 6} W cm{sup -2}) entering the flame is obtained. The qualitative explanation of nonmonotonic behaviour of the absorption coefficient versus the intensity is presented. (laser applications and other topics in quantum electronics)

  16. Effective extreme ultraviolet radiation source based on laser-produced plasma in supersonic xenon jet (United States)

    Bobashev, S. V.; Domracheva, I. V.; Petrenko, M. V.; Tumakaev, G. K.; Stepanova, Z. A.


    Development of highly effective debris free EUV (extreme ultraviolet) radiation source is an actual problem today. Experimental results on EUV output from the source based on laser-produced plasma in supersonic Xe jet have been obtained. The conversion efficiency is 0.08% at a wavelength of 13.5 nm (Δλ = 0.35 nm, 2π sterrad). The methods of optimization of gas-jet converter have been determined. Measurements of EUV radiation energy dependence on the laser energy and the target material (solid-state Cu, Mo, W, Ta and supersonic Xe jet) have been made. The conversion efficiency of laser-produced plasma (CELPP) has been determined and the experimental values have been obtained for different materials of the target.

  17. Maculopathy following exposure to visible and infrared radiation from a laser pointer: a clinical case study. (United States)

    Hanson, James V M; Sromicki, Julian; Mangold, Mario; Golling, Matthias; Gerth-Kahlert, Christina


    Laser pointer devices have become increasingly available in recent years, and their misuse has caused a number of ocular injuries. Online distribution channels permit trade in devices which may not conform to international standards in terms of their output power and spectral content. We present a case study of ocular injury caused by one such device. The patient was examined approximately 9 months following laser exposure using full-field and multifocal electroretinography (ERG and MF-ERG), electrooculography (EOG), and optical coherence tomography (OCT), in addition to a full ophthalmological examination. MF-ERG, OCT, and the ophthalmological examination were repeated 7 months after the first examination. The output of the laser pointer was measured. Despite severe focal damage to the central retina visible fundoscopically and with OCT, all electrophysiological examinations were quantitatively normal; however, qualitatively the central responses of the MF-ERG appeared slightly reduced. When the MF-ERG was repeated 7 months later, all findings were normal. The laser pointer was found to emit both visible and infrared radiation in dangerous amounts. Loss of retinal function following laser pointer injury may not always be detectable using standard electrophysiological tests. Exposure to non-visible radiation should be considered as a possible aggravating factor when assessing cases of alleged laser pointer injury.

  18. In vitro effects of Nd:YAG laser radiation on blood: a quantitative and morphologic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Borrero, E.; Rosenthal, D.; Otis, J.B.


    Use of the Neodymium: yttrium -aluminum -garnet (Nd:YAG) laser to recanalize stenosed arteries may require delivery of the beam through blood. To assess the degree of hemolysis and debris formation, 54 samples of citrated whole blood were exposed to Nd:YAG laser radiation of varying powers (10, 20 and 30 watts) and duration (1, 2.5 and 5 seconds). Compared to control samples which were not subjected to laser light, there was no significant decrease in hematocrit (41 to 40.5 +/- 5%), hemoglobin concentration (13.8 to 13.8 +/- .06 g/1OO ml), or increase in free hemoglobin concentration. Debris weight (from .45 +/- .002 to .45 +/- .002 mg), as well as the white blood cell count, was also not significantly changed (from 5,400 to 5,200 +/- 240 WBC/cm). Light microscopy examination of debris from samples of whole blood, washed erythrocytes, and platelet-rich plasma subjected to the laser at 30 watts for five seconds failed to demonstrate the presence of membrane denaturation of blood elements, as compared with the morphologic changes observed in whole blood samples exposed to a hot tip rather than Nd:YAG laser radiation. Nd:YAG laser can be used intravascularly without fear of hemolysis or debris micro-embolization up to a power of 30 watts for five seconds.

  19. Application of laser radiation and magnetostimulation in therapy of patients with multiple sclerosis. (United States)

    Kubsik, Anna; Klimkiewicz, Robert; Janczewska, Katarzyna; Klimkiewicz, Paulina; Jankowska, Agnieszka; Woldańska-Okońska, Marta


    Multiple sclerosis is one of the most common neurological disorders. It is a chronic inflammatory demyelinating disease of the CNS, whose etiology is not fully understood. Application of new rehabilitation methods are essential to improve functional status. The material studied consisted of 120 patients of both sexes (82 women and 38 men) aged 21-81 years. The study involved patients with a diagnosis of multiple sclerosis. The aim of the study was to evaluate the effect of laser radiation and other therapies on the functional status of patients with multiple sclerosis. Patients were randomly divided into four treatment groups. The evaluation was performed three times - before the start of rehabilitation, immediately after rehabilitation (21 days of treatment) and subsequent control - 30 days after the patients leave the clinic. The following tests were performed for all patients to assess functional status: Expanded Disability Status Scale (EDSS) of Kurtzke and Barthel Index. Results of all testing procedures show that the treatment methods are improving the functional status of patients with multiple sclerosis, with the significant advantage of the synergistic action of laser and magneto stimulation. The combination of laser and magneto stimulation significantly confirmed beneficial effect on quality of life. The results of these studies present new scientific value and are improved compared to program of rehabilitation of patients with multiple sclerosis by laser radiation which was previously used. This study showed that synergic action of laser radiation and magneto stimulation has a beneficial effect on improving functional status, and thus improves the quality of life of patients with multiple sclerosis. The effects of all methods of rehabilitation are persisted after cessation of treatment applications, with a particular advantage of the synergistic action of laser radiation and magneto stimulation, which indicates the possibility to elicitation in these

  20. Rotatory power of sodium vapour oriented by laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Bicchi, P. (Siena Univ. (Italy). Ist. di Fisica); Moi, L.; Zambon, B. (Consiglio Nazionale delle Ricerche, Pisa (Italy). Lab. di Fisica Atomica e Moleculare)


    In this paper the rotatory power of sodium vapour is studied when laser light is used as pumping as well as analysis light. The possibility of having an analysis light whose frequency may be varied in a range larger than the interval between the D/sub 1/ and D/sub 2/ atomic lines allows us to get for the first time the complete shape of the rotation curve and to measure a rotation different from zero even for frequencies very far from the resonance ones. The complete orientation in the vapour caused by the laser pumping-light power permits to obtain very high rotation values. In a cell containing Na and 200 Torr of Ne, we measured, at 185/sup 0/C, 10/sup 0//cm of specific rotation. The dependence of the optical activity on the buffer gas pressure and on the frequency of the pumping light is also studied.

  1. Photophysical and laser characteristics of pyrromethene 567 dye ...

    Indian Academy of Sciences (India)


    PM567) and rhodamine 6G (RH6G) dye was investigated using a home-made GIG- configured dye laser, excited by the second-harmonic radiation (at 532 nm) of a pulsed Nd:YAG laser. Higher laser efficiency was observed with ...

  2. Two-dimensional modeling of multiply scattered laser radiation in optically dense aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Zardecki, A.; Gerstl, S.A.W.; Embury, J.F.


    The discrete ordinates finite element radiation transport code TWOTRAN is applied to describe the multiple scattering of a laser beam from a reflecting target. For a model scenario involving a 99% relative humidity rural aerosol, we compute the average intensity of the scattered radiation and correction factors to the Lambert-Beer law arising from multiple scattering. As our results indicate, two-dimensional x-y and r-z geometry modeling can reliably describe a realistic three-dimensional scenario. Specific results are presented for the two visual ranges of 1.52 and 0.76 km which show that for sufficiently high aerosol concentrations (e.g., equivalent to V = 0.76 km) the target signature in a distant detector becomes dominated by multiply scattered radiation from interactions of the laser light with the aerosol environment.

  3. Biophotonics of the interaction of low-intensity laser radiation with blood erythrocytes (United States)

    Asimov, M. M.; Asimov, R. M.; Batyan, A. N.; Trusevich, M. O.; Rubinov, A. N.


    We have studied experimentally how optical radiation affects the neutralization of the toxic action of heavy metals and harmful chemical compounds (ecotoxicants) on the oxygen-transport function of blood erythrocytes. It has been found that the optical radiation has a stabilizing effect and prevents lowering the erythrocyte concentration in the presence of phenol and heavy metals in blood. We have studied the neutralization efficiency of the toxic action of ecotoxicants in relation to the laser irradiation time. The obtained data on the effect of the laser radiation on the thermal denaturation of hemoglobin and erythrocytes yield the scientific substantiation to the development of the optical method for the use in medicine upon drawing and conserving donor blood. We have shown that the obtained data can be used in medicine for improving the reliability of conditions of conservation and storage of donor blood, as well as for preventing the toxic action of harmful chemical compounds in the environment.

  4. Systems and methods for imaging using radiation from laser produced plasmas (United States)

    Renard-Le Galloudec, Nathalie; Cowan, Thomas E.; Sentoku, Yasuhiko; Rassuchine, Jennifer


    In particular embodiments, the present disclosure provides systems and methods for imaging a subject using radiation emitted from a laser produced plasma generating by irradiating a target with a laser. In particular examples, the target includes at least one radiation enhancing component, such as a fluor, cap, or wire. In further examples, the target has a metal layer and an internal surface defining an internal apex, the internal apex of less than about 15 .mu.m, such as less than about 1 .mu.m. The targets may take a variety of shapes, including cones, pyramids, and hemispheres. Certain aspects of the present disclosure provide improved imaging of a subject, such as improved medical images of a radiation dose than typical conventional methods and systems.

  5. Radiation reaction induced spiral attractors in ultra-intense colliding laser beams

    Directory of Open Access Journals (Sweden)

    Zheng Gong


    Full Text Available The radiation reaction effects on electron dynamics in counter-propagating circularly polarized laser beams are investigated through the linearization theorem and the results are in great agreement with numeric solutions. For the first time, the properties of fixed points in electron phase-space were analyzed with linear stability theory, showing that center nodes will become attractors if the classical radiation reaction is considered. Electron dynamics are significantly affected by the properties of the fixed points and the electron phase-space densities are found to be increasing exponentially near the attractors. The density growth rates are derived theoretically and further verified by particle-in-cell simulations, which can be detected in experiments to explore the effects of radiation reaction qualitatively. The attractor can also facilitate realizing a series of nanometer-scaled flying electron slices via adjusting the colliding laser frequencies.

  6. Controlled joining of Ag nanoparticles with femtosecond laser radiation (United States)

    Huang, H.; Liu, L.; Peng, P.; Hu, A.; Duley, W. W.; Zhou, Y.


    We show that it is possible to tailor the gap separation and interface geometry between adjacent Ag nanoparticles (NPs) by controlling fluence when irradiating with pulses from a fs laser. Unirradiated samples extracted from aqueous solution consist of networks of Ag NPs coated with polyvinylpyrrolidone (PVP). At low laser fluence, bonding between NPs occurs via the formation of an intervening hydrogenated amorphous carbon (α-C:H) layer resulting from the laser-induced decomposition of PVP. This occurs when electrons are emitted at hot-spots created by the trapping of plasmons. The thickness of the α-C:H layer determines the minimum separation between NPs. Ag NPs with different contact geometries can be produced by irradiation of the networks in solution at fluences exceeding the threshold for the formation of α-C:H. At fluences between 200 and 380 μJ/cm2, the α-C:H interface layer is replaced with a metallic neck. Surface enhanced Raman scattering (SERS) has been used to quantify the electromagnetic field enhancement in joined NP samples. We find that Ag NPs bonded by α-C:H and exhibiting a narrow gap possess the highest SERS enhancement.

  7. Recommendations concerning the prevention of radiation-induced health hazards through the application of soft and MID lasers

    Energy Technology Data Exchange (ETDEWEB)


    The Federal Health Office (BGA) recommends observation of the following practical hints: The application of soft lasers or MID lasers for cosmetic treatment or acupuncture represents a danger to the eye. Instructions for use of laser equipment have to indicate this danger. Appropriate use of the equipment will prevent damage. Any person applying soft lasers or MID lasers for treatment of customers or patients near the eye are required to give proof of a special training assuring appropriate handling, and of instructions in laser radiation protection.

  8. Beam characteristics of a large-bore copper laser with a radiatively cooled plasma

    Energy Technology Data Exchange (ETDEWEB)

    Chang, J.J.; Boley, C.D.; Molander, W.A.; Warner, B.E. [Lawrence Livermore National Lab., CA (United States); Martinez, M.W. [Martin Marietta Energy Systems, Inc., Oak Ridge, TN (United States)


    In a large-bore copper vapor laser (CVL), excessive gas heating at the axial region of the discharge lowers its efficiency by thermally populating the metastable lower laser levels. The associated lower gas density also lengthens the discharge field-diffusion time, leading to weaker axial pumping and undesired beam characteristics. The authors` laboratory has developed a novel approach to circumvent this obstacle by cooling the plasma radiatively via a series of segmented metal plates (septa) placed vertically along the length of the tube. This improved tube design significantly lowers the average gas temperature and shortens the radial delay. A 27% increase in laser power was observed with the addition of septa. The authors have characterized the beam intensity profile, spatial and temporal pulse variation, and beam polarization through extensive laboratory measurements. A detailed computational model of the laser has been used to characterize and interpret the laboratory results.

  9. Observation of Terahertz Radiation via the Two-Color Laser Scheme with Uncommon Frequency Ratios (United States)

    Zhang, Liang-Liang; Wang, Wei-Min; Wu, Tong; Zhang, Rui; Zhang, Shi-Jing; Zhang, Cun-Lin; Zhang, Yan; Sheng, Zheng-Ming; Zhang, Xi-Cheng


    In the widely studied two-color laser scheme for terahertz (THz) radiation from a gas, the frequency ratio of the two lasers is usually fixed at ω2/ω1=1 :2 . We investigate THz generation with uncommon frequency ratios. Our experiments show, for the first time, efficient THz generation with new ratios of ω2/ω1=1 :4 and 2 ∶3 . We observe that the THz polarization can be adjusted by rotating the longer-wavelength laser polarization and the polarization adjustment becomes inefficient by rotating the other laser polarization; the THz energy shows similar scaling laws with different frequency ratios. These observations are inconsistent with multiwave mixing theory, but support the gas-ionization or plasma-current model. This study pushes the development of the two-color scheme and provides a new dimension to explore the long-standing problem of the THz generation mechanism.

  10. Studies on linear, nonlinear optical and excited state dynamics of silicon nanoparticles prepared by picosecond laser ablation

    Directory of Open Access Journals (Sweden)

    Syed Hamad


    Full Text Available We report results from our studies on the fabrication and characterization of silicon (Si nanoparticles (NPs and nanostructures (NSs achieved through the ablation of Si target in four different liquids using ∼2 picosecond (ps pulses. The consequence of using different liquid media on the ablation of Si target was investigated by studying the surface morphology along with material composition of Si based NPs. The recorded mean sizes of these NPs were ∼9.5 nm, ∼37 nm, ∼45 nm and ∼42 nm obtained in acetone, water, dichloromethane (DCM and chloroform, respectively. The generated NPs were characterized by selected area electron diffraction (SAED, high resolution transmission microscopy (HRTEM, Raman spectroscopic techniques and Photoluminescence (PL studies. SAED, HRTEM and Raman spectroscopy data confirmed that the material composition was Si NPs in acetone, Si/SiO2 NPs in water, Si-C NPs in DCM and Si-C NPs in chloroform and all of them were confirmed to be polycrystalline in nature. Surface morphological information of the fabricated Si substrates was obtained using the field emission scanning electron microscopic (FESEM technique. FESEM data revealed the formation of laser induced periodic surface structures (LIPSS for the case of ablation in acetone and water while random NSs were observed for the case of ablation in DCM and chloroform. Femtosecond (fs nonlinear optical properties and excited state dynamics of these colloidal Si NPs were investigated using the Z-scan and pump-probe techniques with ∼150 fs (100 MHz and ∼70 fs (1 kHz laser pulses, respectively. The fs pump-probe data obtained at 600 nm consisted of single and double exponential decays which were tentatively assigned to electron-electron collisional relaxation (1 ps. Large third order optical nonlinearities (∼10−14 e.s.u. for these colloids have been estimated from Z-scan data at an excitation wavelength of 680 nm suggesting that the colloidal Si NPs find

  11. Studies on the optogalvanic effect and isotope-selective excitation of ytterbium in a hollow cathode discharge lamp using a pulsed dye laser. (United States)

    Kumar, Pankaj; Kumar, Jitendra; Prakash, Om; Saini, Vinod K; Dixit, Sudhir K; Nakhe, Shankar V


    This paper presents studies on the pulsed optogalvanic effect and isotope-selective excitation of Yb 555.648 nm (0 cm(-1) → 17 992.007 cm(-1)) and 581.067 nm (17 992.007 cm(-1) → 35 196.98 cm(-1)) transitions, in a Yb/Ne hollow cathode lamp. The Yb atoms were excited by narrow linewidth (500-1000 MHz) Rh110 and Rh6G dye based pulsed lasers. Optogalvanic signal inversion for ground state transition at 555.648 nm was observed beyond a hollow cathode discharge current of 8.5 mA, in contrast to normal optogalvanic signal at 581.067 nm up to maximum current of 14 mA. The isotope-selective excitation studies of Yb were carried out by recording Doppler limited optogalvanic signals as a function of dye laser wavelength. For the 581.067 nm transition, three even isotopes, (172)Yb, (174)Yb, and (176)Yb, and one odd isotope, (171)Yb, were clearly resolved. These data were compared with selective isotope excitation by 10 MHz linewidth continuous-wave dye laser. For 555.648 nm transition, isotopes were not clearly resolved, although isotope peaks of low modulation were observed.

  12. Laser-induced narrowband coherent synchrotron radiation: Efficiency versus frequency and laser power

    Directory of Open Access Journals (Sweden)

    C. Evain


    Full Text Available We analyze the narrowband terahertz emission process occurring from electron bunches passing in a bending magnet, after a laser-induced sinusoidal modulation has been performed. In particular, we focus on experimental tunability curves, and power scalings with current and laser power. Theoretically, we simplify the problem formulation using the slowly varying envelope approximation. At low powers, the scaling with laser power appears to be quadratic, and analytical expressions for the tuning curves are obtained. Emission at first passage in the bending magnet, and after one full turn in the storage ring, are considered both experimentally and theoretically. The experiments are performed on the UVSOR-II storage ring.

  13. Two-photon excitation of rubidium atoms inside porous glass (United States)

    Amy, L.; Lenci, L.; Villalba, S.; Failache, H.; Lezama, A.


    We study the two-photon laser excitation to the 5 D5 /2 energy level of 85Rb atoms contained in the interstices of a porous material made from sintered ground glass with typical pore dimensions in the 10-100 μ m range. The excitation spectra show unusual flat-top line shapes, which are shown to be the consequence of wave-vector randomization of the laser light in the porous material. For large atomic densities, the spectra are affected by radiation trapping around the D2 transitions. The effect of the transient atomic response limited by the time of flight between pores walls appears to have a minor influence in the excitation spectra. It is however revealed by the shortening of the temporal evolution of the emitted blue light following a sudden switch-off of the laser excitation.

  14. Apparatus and method for generating continuous wave 16 .mu.m laser radiation using gaseous CF.sub.4 (United States)

    Telle, John M.


    Apparatus and method for generating continuous wave 16 .mu.m laser radiation using gaseous CF.sub.4. Laser radiation at 16 .mu.m has been observed in a cooled static cell containing low pressure CF.sub.4 optically pumped by an approximately 3 W output power cw CO.sub.2 laser. The laser cavity employed was a multiple-pass off-axis-path two spherical mirror ring resonator. Unidirectional CF.sub.4 laser output power at 615 cm.sup.-1 exceeded 2 mW. Computer calculations indicate that for modest pump powers of about 40 W, approximately 1 W of emitted laser radiation at 16 .mu.m might be obtained.

  15. Apparatus and method for generating continuous wave 16. mu. m laser radiation using gaseous CF/sub 4/ (United States)

    Telle, J.M.


    Apparatus and method for generating continuous wave 16 laser radiation using gaseous CF/sub 4/. Laser radiation at 16 has been observed in a cooled static cell containing low pressure CF/sub 4/ optically pumped by an approximately 3 W output power c-w CO/sub 2/ laser. The laser cavity employed was a multiple-pass off-axis-path two spherical mirror ring resonator. Unidirectional CF/sub 4/ laser output power at 615 cm/sup -1/ exceeded 2 mW. Computer calculations indicate that for modest pump powers of about 40 W, approximately 1 W of emitted laser radiation at 16 might be obtained.

  16. Investigations of the potential functions of weakly bound diatomic molecules and laser-assisted excitive Penning ionization

    Energy Technology Data Exchange (ETDEWEB)

    Goble, J.H. Jr.


    Three variations on the Dunham series expansion function of the potential of a diatomic molecule are compared. The differences among these expansions lie in the choice of the expansion variable, lambda. The functional form of these variables are lambda/sub s/ = l-r/sub e//r for the Simon-Parr-Finlan version, lambda/sub T/ - 1-(r/sub e//r)/sup p/ for that of Thakkar, and lambda/sub H/ = 1-exp(-rho(r/r/sub e/-1) for that of Huffaker. A wide selection of molecular systems are examined. It is found that, for potentials in excess of thirty kcal/mole, the Huffaker expansion provides the best description of the three, extrapolating at large internuclear separation to a value within 10% of the true dissociation energy. For potentials that result from the interaction of excited states, all series expansions show poor behavior away from the equilibrium internuclear separation of the molecule. The series representation of the potentials of weakly bound molecules are examined in more detail. The ground states of BeAr/sup +/, HeNe/sup +/, NaAr, and Ar/sub 2/ and the excited states of HeNe+, NaNe, and NaAr are best described by the Thakkar expansion. Finally, the observation of laser-assisted excitive Penning ionization in a flowing afterglow is reported. The reaction Ar(/sup 3/P/sub 2/) + Ca + h nu ..-->.. Ar + Ca/sup +/(5p /sup 2/P/sub J/) + e/sup -/ occurs when the photon energy, h nu, is approximately equal to the energy difference between the metastable argon and one of the fine structure levels of the ion's doublet. By monitoring the cascade fluorescence of the above reaction and comparing it to the flourescence from the field-free process Ar(/sup 3/P/sub 2/) + Ca ..-->.. Ar + Ca/sup +/(4p /sup 2/P/sub J/) + e/sup -/ a surprisingly large cross section of 6.7 x 10/sup 3/ A/sup 2/ is estimated.

  17. 3D Finite Element Model for Writing Long-Period Fiber Gratings by CO2 Laser Radiation

    Directory of Open Access Journals (Sweden)

    José Rebordão


    Full Text Available In the last years, mid-infrared radiation emitted by CO2 lasers has become increasing popular as a tool in the development of long-period fiber gratings. However, although the development and characterization of the resulting sensing devices have progressed quickly, further research is still necessary to consolidate functional models, especially regarding the interaction between laser radiation and the fiber’s material. In this paper, a 3D finite element model is presented to simulate the interaction between laser radiation and an optical fiber and to determine the resulting refractive index change. Dependence with temperature of the main parameters of the optical fiber materials (with special focus on the absorption of incident laser radiation is considered, as well as convection and radiation losses. Thermal and residual stress analyses are made for a standard single mode fiber, and experimental results are presented.

  18. 3D finite element model for writing long-period fiber gratings by CO2 laser radiation. (United States)

    Coelho, João M P; Nespereira, Marta; Abreu, Manuel; Rebordão, José


    In the last years, mid-infrared radiation emitted by CO2 lasers has become increasing popular as a tool in the development of long-period fiber gratings. However, although the development and characterization of the resulting sensing devices have progressed quickly, further research is still necessary to consolidate functional models, especially regarding the interaction between laser radiation and the fiber's material. In this paper, a 3D finite element model is presented to simulate the interaction between laser radiation and an optical fiber and to determine the resulting refractive index change. Dependence with temperature of the main parameters of the optical fiber materials (with special focus on the absorption of incident laser radiation) is considered, as well as convection and radiation losses. Thermal and residual stress analyses are made for a standard single mode fiber, and experimental results are presented.

  19. An assessment of techniques for dehydrating root canals using infrared laser radiation. (United States)

    Amyra, T; Walsh, L T; Walsh, L J


    Infrared lasers have been used for debridement and sterilisation of both soft and hard tissues, but there have been few studies of such laser applications in endodontics. The present laboratory study was undertaken to examine the feasibility of using pulsed infrared laser radiation to remove moisture from root canals (with an adjunctive sterilising effect). Canals were prepared in extracted teeth and a standardised technique used to fill the apical half of the root canal with saline. Pulses of CO2 or Nd:YAG laser energy were delivered into the root canal system via miniature applicators and residual fluid determined, as well as temperature changes on the root surface. With the CO2 laser, long pulse durations were effective at dehydrating the canals, but elicited deleterious thermal changes both locally within the canal as well as on the root surface. With Nd:YAG laser treatment, large temperature increases on the root surface occurred even with low powers and low pulse frequencies, and extended times were necessary for dehydration. With higher powers and pulse frequencies, complete dehydration could be achieved in less than 60 seconds, however root surface temperatures increased approximately 25 degrees, and the radicular dentine was damaged by the production of plasma. Dehydration of root canals could not be achieved safely with these two infrared lasers, and damage to both radicular dentine and the periodontal ligament would occur if these techniques were to be applied clinically. Alternative methods which do not exert significant thermal effects should be investigated.

  20. Evaluating the use of laser radiation in cleaning of copper embroidery threads on archaeological Egyptian textiles

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Kareem, Omar [Conservation Department, Faculty of Archaeology, Cairo University, El-Gamaa Street, El-Giza (Egypt)], E-mail:; Harith, M.A. [National Institute of Laser Enhanced Science, Cairo University (Egypt)], E-mail:


    Cleaning of copper embroidery threads on archaeological textiles is still a complicated conservation process, as most textile conservators believe that the advantages of using traditional cleaning techniques are less than their disadvantages. In this study, the uses of laser cleaning method and two modified recipes of wet cleaning methods were evaluated for cleaning of the corroded archaeological Egyptian copper embroidery threads on an archaeological Egyptian textile fabric. Some corroded copper thread samples were cleaned using modified recipes of wet cleaning method; other corroded copper thread samples were cleaned with Q-switched Nd:YAG laser radiation of wavelength 532 nm. All tested metal thread samples before and after cleaning were investigated using a light microscope and a scanning electron microscope with an energy dispersive X-ray analysis unit. Also the laser-induced breakdown spectroscopy (LIBS) technique was used for the elemental analysis of laser-cleaned samples to follow up the laser cleaning procedure. The results show that laser cleaning is the most effective method among all tested methods in the cleaning of corroded copper threads. It can be used safely in removing the corrosion products without any damage to both metal strips and fibrous core. The tested laser cleaning technique has solved the problems caused by other traditional cleaning techniques that are commonly used in the cleaning of metal threads on museum textiles.

  1. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Generation of magnetic fields as a result of interaction of pairs of radiation pulses with solid barriers (United States)

    Zakharov, N. S.; Shaĭnoga, I. S.; Shentsev, N. I.


    An analysis is made of the problem of generation of magnetic fields in a laser plasma jet formed as a result of the interaction of two consecutive radiation pulses of moderate intensity with a dielectric barrier. It is assumed that the source of an emf is the thermo-emf of the inhomogeneous plasma. The structure of gasdynamic streams and the parameters of magnetic fields in the plasma jet are found by numerical solution of a known system of equations considered in a two-dimensional cylindrical configuration. The profiles of the plasma parameters and the temporal and spatial distributions of the magnetic fields are presented. It is shown that the results of numerical calculations can be useful, for example, in the diagnostics of laser jets.

  2. Effect of uv laser radiation on copper-proteins (United States)

    Bacci, M.; Fabeni, P.; Linari, R.; Pazzi, G. P.

    The results of irradiation studies of human ceruloplasmin, mushroom tyrosinase and Limuluspolyphemus hemocyanin with a nitrogen laser (Λ = 337.1 nm) are presented. In all the proteins we have considered the absorption band at 330 nm, characteristic of dimer Type 3 copper centres, decreases, while an increase of the absorbance at 280 nm is observed. Moreover a new band at about 400 nm appears in irradiated ceruloplasmin. Finally sharp oscillations of the absorbance at 610 and 794 nm are recorded in ceruloplasmin, when the irradiation is switched off.

  3. Biological Effects of Laser Radiation. Volume II. Review of Our Studies on Biological Effects of Laser Radiation-1965-1971. (United States)


    produces dermal and nasal irritation.5 Boron systems. Bromine, chlorine and ucine are irntants to the trifluoride (TLV I ppm) in air, can cause pneumonitis...bromine, chlorine , iodine. General. Dept. of the Army. VASA Grant .VGR 011-07.I7 hydrolluoric acid. -141- from LASER OC~US/CC7t0SER !;68 The rare tarths...the system may crack and release the enclosed vapors. Examples of these gases are chlorine , bromine, lead, mercury, carbon monoxide, and hydro- gen

  4. Generation of nano-voids inside polylactide using femtosecond laser radiation (United States)

    Viertel, Tina; Pabst, Linda; Olbrich, Markus; Ebert, Robby; Horn, Alexander; Exner, Horst


    The arrangement of nanometer-sized voids, induced by focusing intense laser radiation within transparent material can allow the generation of transparent components with dimensions in the micrometer to nanometre range due to internal contour cut and thus satisfy the progressive miniaturization of products in micro-optics and medical technologies. For further improvements in the precision of those components, a deep understanding of the involved processes during the interaction of laser radiation within the material is necessary. In this work, voids inside bulk polylactide (PLA), a bioabsorbable polymer, were generated using a femtosecond laser ( λ = 1030 nm, τH = 180 fs) with single and multiple pulse irradiation. The dependence of the spot size was examined by the use of four microscope objectives with focus radii of 4.9, 3.3, 2 and 1.2 µm. For the experiments, the pulse energy and focusing depth into the material were varied. The dimensions of the voids were experimentally determined as function of the intensity. Differences in the lateral and axial extents of the voids were obtained for different focus radii and focusing depths at same intensities. Furthermore, the intensity distribution of the laser radiation inside the material for the different focus radii and focusing depths, and their dependence on the lateral and axial sizes of the voids was simulated and compared with the experimental results.

  5. [Enhancing effect of sample additive on laser-induced plasma radiation]. (United States)

    Zhang, Lin-Jing; Chen, Jin-Zhong; Yang, Shao-Peng; Wei, Yan-Hong; Guo, Qing-Lin


    In order to improve the radiation characteristic of laser-induced plasma, with the national standard soil taken as the target sample, a laser spectrum analytical system which composed of a high-energy neodymium glass laser, a multifunctional and compact integrated spectrometer, and a CCD detector was used to detect the influence of the NaCl sample additive on the laser plasma radiation intensity. The electron temperature and the electron density of the plasmas were also calculated from the lines intensity and stark broadening of emission spectral line respectively. The experimental results indicated that with the increase in the NaCl additive, the spectral intensity, signal-to-background ratio, the electron temperature, and the electron density all went up firstly and then down. When 15% NaCl was added, the radiation intensity of the plasma reached the maximum value, the spectral lines intensity of element Mn, K, Fe, and Ti increased by 39.2%, 42.5%, 53.9% and 33.8% compared to that without additive respectively, the spectral signal-to-background ratio increased by 64.4%, 84.39, 44.55% and 58.2% respectively, while the electron temperature and the electron density of the plasmas were heightened by 0.17 times and 0.36 times respectively.

  6. Eczematous Dermatitis Occurring on a Café-au-Lait Spot Long after Laser Radiation. (United States)

    Mihara, Motoyuki


    A 40-year-old woman presented with an itchy erythematosquamous change of a café-au-lait spot in her face. The onset of this change occurred just after her relocation. The café-au-lait spot had been irradiated by laser approximately 20 years ago. Clinically, there was a coin-sized erythema with a slight scale on the pigmented lesion in the left lateral orbital region. Histopathologically, the lesion demonstrated both spongiotic dermatitis and interface dermatitis together with lymphohistiocytic cell infiltration, in addition to moderate acanthosis and elongation of rete ridges with slight basal hyperpigmentation. From these clinical and histopathological findings, the lesion was diagnosed as eczematous dermatitis occurring on the café-au-lait spot after laser radiation. Another interesting histopathological finding was that some parts of a lobule of the sebaceous gland were occupied exclusively by degenerative atrophic sebocytes. From the viewpoint of pathogenesis, the eczematous dermatitis of this patient could have been an accompanying feature of a neurogenic inflammation occurring on the café-au-lait spot after laser radiation, and the atrophic change of a part of the sebaceous lobule might have been induced by a morphogenetic alteration of certain germinative cells of the sebaceous lobule due to laser radiation.

  7. Coatings of metal substrates assisted by laser radiation

    Directory of Open Access Journals (Sweden)

    Caudevilla, H.


    Full Text Available In this contribution, a new way of obtaining ceramic coatings is presented. This method uses precursor suspensions, settled on substrates and in-situ pyrolised with a laser. Different deposition techniques of the ceramic precursors have been tested in order to obtain a homogeneous distribution on the metal substrate before the laser treatment.

    La combinación de recubrimientos utilizando disoluciones de precursores metálicos con la pirólisis asistida por láser, permite obtener una gran diversidad de recubrimientos sobre sustratos de muy distinta naturaleza. Se han realizado estudios, tanto con disoluciones poliméricas, como con disoluciones de tipo sol-gel y pastas obtenidas con técnicas similares, depositadas utilizando métodos convencionales de inmersión y atomización previa a la pirólisis asistida por láser, así como simultánea. En este trabajo se presenta un resumen de los resultados más significativos obtenidos en la realización de recubrimientos sobre sustratos metálicos y cerámicos.

  8. Measurement of heat pump processes induced by laser radiation (United States)

    Garbuny, M.; Henningsen, T.


    A series of experiments was performed in which a suitably tuned CO2 laser, frequency doubled by a Tl3AsSe37 crystal, was brought into resonance with a P-line or two R-lines in the fundamental vibration spectrum of CO. Cooling or heating produced by absorption in CO was measured in a gas-thermometer arrangement. P-line cooling and R-line heating could be demonstrated, measured, and compared. The experiments were continued with CO mixed with N2 added in partial pressures from 9 to 200 Torr. It was found that an efficient collisional resonance energy transfer from CO to N2 existed which increased the cooling effects by one to two orders of magnitude over those in pure CO. Temperature reductions in the order of tens of degrees Kelvin were obtained by a single pulse in the core of the irradiated volume. These measurements followed predicted values rather closely, and it is expected that increase of pulse energies and durations will enhance the heat pump effects. The experiments confirm the feasibility of quasi-isentropic engines which convert laser power into work without the need for heat rejection. Of more immediate potential interest is the possibility of remotely powered heat pumps for cryogenic use, such applications are discussed to the extent possible at the present stage.

  9. Antibacterial effects of pulsed Nd:YAG laser radiation at different energy settings in root canals. (United States)

    Folwaczny, Matthias; Mehl, Albert; Jordan, Christian; Hickel, Reinhard


    The in vitro study aimed at the determination of the bacterial reduction in root canals used pulsed Nd:YAG laser radiation without a photosensitizing dye. In addition the temperature change in the root canals was determined during laser irradiation. The study sample was 114 root canals of extracted single-rooted human teeth that have been enlarged mechanically, sterilized, and randomly assigned to two experimental units. The source of radiation was a Nd:YAG laser device emitting pulsed infrared radiation at a wavelength of 1.064 microm, a pulse duration of 100 micros, and a pulse repetition rate of 20 pps. Samples of each experimental unit were inoculated with Escherichia coli (ATCC 25922) or Staphylococcus aureus (ATCC 25923), respectively, and divided into subgroups of 13 teeth each for irradiation for 20 s at 100 mJ or 200 mJ. One subgroup was left untreated as positive control and one subgroup was rinsed with 0.5 ml of sodium hypochloride. After laser treatment or rinsing with sodium hypochloride the number of bacteria in each root canal was determined using the surface spread plate technique. Statistical analysis of the results was performed with ANOVA and Scheffé test at a level of significance of 5% (p temperature increase at 100 mJ was 24.3 degrees C (+/-3.9) and that at 200 mJ was 61.8 degrees C (+/-4.2). The Nd:YAG laser radiation has antimicrobial effects in root canals even in the absence of photosensitizing dyes but also causes considerable temperature increase.

  10. Two-stage model of nanocone formation on a surface of elementary semiconductors by laser radiation (United States)


    In this work, we study the mechanism of nanocone formation on a surface of elementary semiconductors by Nd:YAG laser radiation. Our previous investigations of SiGe and CdZnTe solid solutions have shown that nanocone formation mechanism is characterized by two stages. The first stage is characterized by formation of heterostructure, for example, Ge/Si heterostructure from SiGe solid solutions, and the second stage is characterized by formation of nanocones by mechanical plastic deformation of the compressed Ge layer on Si due to mismatch of Si and Ge crystalline lattices. The mechanism of nanocone formation for elementary semiconductors is not clear until now. Therefore, the main goal of our investigations is to study the stages of nanocone formation in elementary semiconductors. A new mechanism of p-n junction formation by laser radiation in the elementary semiconductor as a first stage of nanocone formation is proposed. We explain this effect by the following way: p-n junction is formed by generation and redistribution of intrinsic point defects in temperature gradient field – the thermogradient effect, which is caused by strongly absorbed laser radiation. According to the thermogradient effect, interstitial atoms drift towards the irradiated surface, but vacancies drift to the opposite direction – in the bulk of semiconductor. Since interstitials in Ge crystal are of n-type and vacancies are known to be of p-type, a n-p junction is formed. The mechanism is confirmed by the appearance of diode-like current–voltage characteristics after i-Ge irradiation crystal by laser radiation. The mechanism in Si is confirmed by conductivity type inversion and increased microhardness of Si crystal. The second stage of nanocone formation is laser heating up of top layer enriched by interstitial atoms with its further plastic deformation due to compressive stress caused by interstitials in the top layer and vacancies in the buried layer. PMID:22849869

  11. In vitro effects of argon laser radiation on blood: quantitative and morphologic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Abela, G.S.; Crea, F.; Smith, W.; Pepine, C.J.; Conti, C.R.


    Use of the argon laser to recanalize stenosed arteries may require delivery of the beam through blood. To assess the degree of hemolysis and debris formation, 84 samples of citrated whole blood were exposed to argon laser radiation with varying power (1, 2 and 3 watts) and duration (5, 10, 20 and 40 seconds). Compared with control samples, only blood samples exposed to a power of 3 watts for 40 seconds showed a marked decrease in hematocrit (from 37 +/- 1.3 to 33 +/- 1.4%, p less than 0.01) and a marked increase in both free hemoglobin concentration (from 0.2 +/- 0.2 to 1.3 +/- 0.5 g/100 ml, p less than 0.01) and debris weight (from 0.9 +/- 0.3 to 2.8 +/- 0.5 mg, p less than 0.01). Scanning electron microscopy of debris from samples of whole blood, washed erythrocytes and platelet-rich plasma lased at 3 watts for 40 seconds documented the presence of membrane denaturation of blood elements, resulting in their fusion to form complex mesh-like conglomerates. Similar morphologic changes were observed in whole blood samples exposed to a ''hot tip'' rather than laser radiation. These data indicate that: 1) argon laser radiation with a power of 3 watts does not produce apparent hemolysis or debris formation for exposure periods up to 20 seconds, and 2) the effects of laser radiation on blood are probably mediated by thermal denaturation of cell membranes, as suggested by the same morphologic changes produced by thermal injury from a ''hot tip.''

  12. Influence of Welding Current and Focal Position on the Resonant Absorption of Laser Radiation in a TIG Welding Arc (United States)

    Emde, B.; Huse, M.; Hermsdorf, J.; Kaierle, S.; Wesling, V.; Overmeyer, L.

    The work presents the influence of welding current and focal position on the resonant absorption of diode laser radiation in a TIG welding arc. The laser beam is guided perpendicular to the electrical arc to avoid an interaction with the electrodes. Laser power measurements have shown a reduction of the measured laser power up to 18% after passing the electrical arc. This reduction results from the interaction of argon shielding gas atoms and laser radiation at 810.4 nm and 811.5 nm. The interaction is strongly affected by the adjusted welding current and the adjustment of the laser beam and the electrical arc. Lowering the welding current or shifting the laser beam out of the centerline of the electrical arc reduces the ionization probability. An increased ionization is necessary to decrease the resistance of the electrical arc.

  13. Development of short pulse laser driven micro-hohlraums as a source of EUV radiation (United States)

    Krushelnick, Karl; Batson, Thomas; McKelvey, Andrew; Raymond, Anthony; Thomas, Alec; Yanovsky, Victor; Nees, John; Maksimchuk, Anatoly


    Experiments at large scale laser facilities such as NIF allow the radiativ properties of dens, high-temperature matter to be studied at previously unreachable regime, but are limited by cost and system availability. A scaled system using a short laser pulses and delivering energy to much smaller hohlraum could be capable of reaching comparable energy densities by depositing the energy in a much smaller volume before ablation of the wall material closes the cavit. The laser is tightl focused through the cavity and then expands to illuminate the wall. Experiments were performe using the Hercules Ti:Sapphire laser system at Michiga. Targets include cavities machined in bulk material using low laser power, and then shot in situ with a single full power pulse as well as micron scale pre-fabricate target. Spectral characteristics were measured using a soft X-ray spectromete, K-alpha x-ray imaging system and a filtered photo cathode array. Scalings of the radiation temperature were made for variations in the hohlraum cavit, the pulse duration as well as the focusing conditions. Proof of principle time resolved absorption spectroscopy experiments were also performe. These sources may allow opacity and atomic physics measurements with plasma an radiation temperatures comparable to much larger hohlraums, but with much higher repetition rate and in a university scale laboratory. We acknowledge funding from DTRA grant HDTRA1-11-1-0066.

  14. Scattering effect in radiative heat transfer during selective laser sintering of polymers (United States)

    Liu, Xin; Boutaous, M'hamed; Xin, Shihe


    The aim of this work is to develop an accurate model to simulate the selective laser sintering (SLS) process, in order to understand the multiple phenomena occurring in the material and to study the influence of each parameter on the quality of the sintered parts. A numerical model, coupling radiative and conductive heat transfers in a polymer powder bed providing a local temperature field, is proposed. To simulate the polymer sintering by laser heating as in additive manufacturing, a double-lines scanning of a laser beam over a thin layer of polymer powder is studied. An effective volumetric heat source, using a modified Monte Carlo method, is estimated from laser radiation scattering and absorption in a semi-transparent polymer powder bed. In order to quantify the laser-polymer interaction, the heating and cooling of the material is modeled and simulated with different types heat sources by both finite elements method (FEM) and discrete elements method (DEM). To highlight the importance of introducing a semi-transparent behavior of such materials and in order to validate our model, the results are compared with works taken from the literature.

  15. Response of a semiconducting infinite medium under two temperature theory with photothermal excitation due to laser pulses (United States)

    Lotfy, Kh.; Gabr, M. E.


    A novel model of two-dimensional deformations for two-temperature theory at the free surface under the excitation of thermoelastic wave by pulsed laser for a semi-infinite semiconducting medium is studied. The effect of mechanical force during a photothermal process is investigated. The mathematical methods of the Lord-Shulman (LS includes one relaxation time) and Green-Lindsay (GL with two relaxation times) theories as well as the classical dynamical coupled theory (CD) are used. An exact expression for displacement components, force stresses, carrier density and distribution of temperature are obtained using the harmonic wave analysis. Combinations of two-temperature and photothermal theories are obtained analytically. Comparisons of the results are made between the three theories also. The effects of thermoelectric coupling parameter, two-temperature parameter on the displacement component, force stress, carrier density, and distribution of temperature for silicon (Si) medium have been illustrated graphically. The variations of the considered variables with the horizontal distance have been discussed.

  16. Distinguishing the laser-induced spin precession excitation mechanism in Fe/MgO(001) through field orientation dependent measurements (United States)

    Ma, T. P.; Zhang, S. F.; Yang, Y.; Chen, Z. H.; Zhao, H. B.; Wu, Y. Z.


    Rotational field dependence of laser-induced magnetization precession in a single-crystal Fe/MgO(001) sample was studied by the time resolved magneto-optical Kerr effect. Polar and longitudinal magnetization components were separated by measuring precession dynamics under opposite fields. When the applied field is weaker than the anisotropy field of an Fe film, the precession amplitude is small for the field direction near the easy axis and becomes larger as the field rotates towards the hard axis, showing a four-fold symmetry in agreement with the in-plane magnetic anisotropy; whereas at higher fields, the amplitude displays a drop near the hard axis. Such precession behavior can be well reproduced using an excitation model with rapidly modified but slowly recovered magnetic anisotropy and considering the elliptical precession trajectory. Our results indicate that the dominant mechanism for triggering Fe spin precession is the anisotropy modulation correlating with the lattice thermalization, rather than the transient anisotropy modulation due to the high electron temperature within 1 ps.

  17. Echo-enabled tunable terahertz radiation generation with a laser-modulated relativistic electron beam

    Directory of Open Access Journals (Sweden)

    Zhen Wang


    Full Text Available A new scheme to generate narrow-band tunable terahertz (THz radiation using a variant of the echo-enabled harmonic generation is analyzed. We show that by using an energy chirped beam, THz density modulation in the beam phase space can be produced with two lasers having the same wavelength. This removes the need for an optical parametric amplifier system to provide a wavelength-tunable laser to vary the central frequency of the THz radiation. The practical feasibility and applications of this scheme are demonstrated numerically with a start-to-end simulation using the beam parameters at the Shanghai Deep Ultraviolet Free-Electron Laser facility (SDUV. The central frequency of the density modulation can be continuously tuned by either varying the chirp of the beam or the momentum compactions of the chicanes. The influence of nonlinear rf chirp and longitudinal space charge effect have also been studied in our article. The methods to generate the THz radiation in SDUV with the new scheme and the estimation of the radiation power are also discussed briefly.

  18. Effects of Soft-Core Potentials and Coulombic Potentials on Bremsstrahlung Radiation during Laser Matter Interaction (United States)

    Pandit, Rishi; Sentoku, Yasuhiko; Sawada, Hiroshi; Ramunno, Lora; Ackad, Edward


    An intense, short laser pulse incident on rare-gas clusters can produce nano-plasmas containing energetic electrons. As these electrons undergo scattering, both from phonons and ions, they emit bremsstrahlung radiation. Here we compare a theory of Bremsstrahlung emission appropriate for the interaction of intense lasers with matter using soft-core potentials and coulombic potential. A new scaling for the radiation cross-section and Emissivity via bremsstrahlung are derived for soft-core potential which depends on the potential depth, used to avoid coulomb singularity and for coulombic potential and implemented in a particle in cell code (PICLS). The radiation cross-section and emissivity via bremsstrahlung is found to increase rapidly with increases in potential depth up to 100 eV and then becomes mostly saturated for larger depths of a soft-core potential. For both cases, the radiation cross-section and emissivity of Bremsstrahlung increases with increases in laser wavelength. The bremsstrahlung emission may provide a broadband light source for diagnostics. This work was supported by Air Force Office of Scientific Research under AFOSR Award No. FA9550-14-1-0247.

  19. Modification in oxidative processes in muscle tissues exposed to laser- and light-emitting diode radiation. (United States)

    Monich, Victor A; Bavrina, Anna P; Malinovskaya, Svetlana L


    Exposure of living tissues to high-intensity red or near-infrared light can produce the oxidative stress effects both in the target zone and adjacent ones. The protein oxidative modification (POM) products can be used as reliable and early markers of oxidative stress. The contents of modified proteins in the investigated specimens can be evaluated by the 2,4-dinitrophenylhydrazine assay (the DNPH assay). Low-intensity red light is able to decrease the activity of oxidative processes and the DNPH assay data about the POM products in the biological tissues could show both an oxidative stress level and an efficiency of physical agent protection against the oxidative processes. Two control groups of white rats were irradiated by laser light, the first control group by red light and the second one by near-infrared radiation (NIR).Two experimental groups were consequently treated with laser and red low-level light-emitting diode radiation (LED). One of them was exposed to red laser light + LED and the other to NIR + LED. The fifth group was intact. Each group included ten animals. The effect of laser light was studied by methods of protein oxidative modifications. We measured levels of both induced and spontaneous POM products by the DNPH assay. The dramatic increase in levels of POM products in the control group samples when compared with the intact group data as well as the sharp decrease in the POM products in the experimental groups treated with LED low-level light were statistically significant (p ≤ 0.05). Exposure of skeletal muscles to high-intensity red and near-infrared laser light causes oxidative stress that continues not less than 3 days. The method of measurement of POM product contents by the DNPH assay is a reliable test of an oxidative process rate. Red low-intensity LED radiation can provide rehabilitation of skeletal muscle tissues treated with high-intensity laser light.

  20. Investigation of Doppler spectra of laser radiation scattered inside hand skin during occlusion test (United States)

    Kozlov, I. O.; Zherebtsov, E. A.; Zherebtsova, A. I.; Dremin, V. V.; Dunaev, A. V.


    Laser Doppler flowmetry (LDF) is a method widely used in diagnosis of microcirculation diseases. It is well known that information about frequency distribution of Doppler spectrum of the laser radiation scattered by moving red blood cells (RBC) usually disappears after signal processing procedure. Photocurrent’s spectrum distribution contains valuable diagnostic information about velocity distribution of the RBC. In this research it is proposed to compute the indexes of microcirculation in the sub-ranges of the Doppler spectrum as well as investigate the frequency distribution of the computed indexes.