High-power CW and long-pulse lasers in the green wavelength regime for copper welding
Pricking, Sebastian; Huber, Rudolf; Klausmann, Konrad; Kaiser, Elke; Stolzenburg, Christian; Killi, Alexander
2016-03-01
We report on industrial high-power lasers in the green wavelength regime. By means of a thin disk oscillator and a resonator-internal nonlinear crystal for second harmonic generation we are able to extract up to 8 kW pulse power in the few-millisecond range at a wavelength of 515 nm with a duty cycle of 10%. Careful shaping and stabilization of the polarization and spectral properties leads to a high optical-to-optical efficiency larger than 55%. The beam parameter product is designed and measured to be below 5 mm·mrad which allows the transport by a fiber with a 100 μm core diameter. The fiber and beam guidance optics are adapted to the green wavelength, enabling low transmission losses and stable operation. Application tests show that this laser is perfectly suited for copper welding due to the superior absorption of the green wavelength compared to IR, which allows us to produce weld spots with an unprecedented reproducibility in diameter and welding depth. With an optimized set of parameters we could achieve a splatter-free welding process of copper, which is crucial for welding electronic components. Furthermore, the surface condition does not influence the welding process when the green wavelength is used, which allows to skip any expensive preprocessing steps like tin-coating. With minor changes we could operate the laser in cw mode and achieved up to 1.7 kW of cw power at 515 nm with a beam parameter product of 2.5 mm·mrad. These parameters make the laser perfectly suitable for additional applications such as selective laser melting of copper.
International Nuclear Information System (INIS)
Santhanagopalan, Dhamodaran; Schreiber, Daniel K.; Perea, Daniel E.; Martens, Richard L.; Janssen, Yuri; Khalifah, Peter; Meng, Ying Shirley
2015-01-01
The effects of laser wavelength (355 nm and 532 nm) and laser pulse energy on the quantitative analysis of LiFePO 4 by atom probe tomography are considered. A systematic investigation of ultraviolet (UV, 355 nm) and green (532 nm) laser assisted field evaporation has revealed distinctly different behaviors. With the use of a UV laser, the major issue was identified as the preferential loss of oxygen (up to 10 at%) while other elements (Li, Fe and P) were observed to be close to nominal ratios. Lowering the laser energy per pulse to 1 pJ/pulse from 50 pJ/pulse increased the observed oxygen concentration to nearer its correct stoichiometry, which was also well correlated with systematically higher concentrations of 16 O 2 + ions. Green laser assisted field evaporation led to the selective loss of Li (∼33% deficiency) and a relatively minor O deficiency. The loss of Li is likely a result of selective dc evaporation of Li between or after laser pulses. Comparison of the UV and green laser data suggests that the green wavelength energy was absorbed less efficiently than the UV wavelength because of differences in absorption at 355 and 532 nm for LiFePO 4 . Plotting of multihit events on Saxey plots also revealed a strong neutral O 2 loss from molecular dissociation, but quantification of this loss was insufficient to account for the observed oxygen deficiency. - Highlights: • Laser wavelength and pulse energy affect accuracy of APT analysis of LiFePO 4 . • Oxygen deficiency observed for UV laser; stronger at higher laser energies. • Selective loss of Li with green laser due to dc evaporation. • Saxey plots reveal prevalent formation of O 2 neutrals. • Quantification of molecular dissociations cannot account for O deficiency
Komori, Yuichi; Ishii, Yukihiro
2010-08-01
A doubly-doped LiNbO3 (LN) crystal has been well used as a nonvolatile two-wavelength recording material. By using two levels of the crystal, two-kind holograms can be recorded on one crystal; a hologram is recorded with a 405-nm blue laser diode (LD) for a deep Mn level, and another hologram is with a 532-nm green laser for a shallow Fe level. The recording capacity doubles. A 780-nm LD is non-volatile reconstructing source since the LD line is insensitive to both levels. Multiplexed reconstructed images are demonstrated by using a sharp angular selectivity of a volume LN crystal keeping Bragg condition with spherical reconstructions.
Mudgil, A V; To, K W; Balachandran, R M; Janigian, R H; Tsiaras, W G
1999-01-01
To determine the optimal wavelength for subconjunctival laser suture lysis. 130 black monofilament 10-0 nylon sutures were sewn subconjunctivally into the bare sclera of enucleated rabbit globes. The lowest energy levels facilitating laser suture lysis were determined for the argon green (514.5 NM), argon blue-green (488.0 NM, 514.5 NM), and krypton red (647.1 NM) wavelengths. In addition, absorption spectroscopy was performed on the suture material and conjunctiva using the Perkin Elmer W/VIS Lambda 2 spectrometer. Krypton red produced the fewest buttonhole defects, and it was also the most efficient energy source for suture lysis (P = 0.0001) under nontenectomized conjunctiva. Absorbance spectra studies revealed peak absorbance at 628 NM for the 10-0 nylon suture material. Based on animal and absorption spectroscopy studies, krypton red may be a safer and more efficient wavelength for subconjunctival laser suture lysis.
Continuous-wave Optically Pumped Lasing of Hybrid Perovskite VCSEL at Green Wavelength
Alias, Mohd Sharizal
2017-05-08
We demonstrate the lasing of a perovskite vertical-cavity surface-emitting laser at green wavelengths, which operates under continuous-wave optical pumping at room-temperature by embedding hybrid perovskite between dielectric mirrors deposited at low-temperature.
Continuous-wave Optically Pumped Lasing of Hybrid Perovskite VCSEL at Green Wavelength
Alias, Mohd Sharizal; Liu, Zhixiong; Alatawi, Abdullah; Ng, Tien Khee; Wu, Tao; Ooi, Boon S.
2017-01-01
We demonstrate the lasing of a perovskite vertical-cavity surface-emitting laser at green wavelengths, which operates under continuous-wave optical pumping at room-temperature by embedding hybrid perovskite between dielectric mirrors deposited at low-temperature.
Maestre, H; Torregrosa, A J; Fernández-Pousa, C R; Rico, M L; Capmany, J
2008-05-01
We report a dual-wavelength continuous-wave laser at 542.4 and 546.8 nm based on an Nd(3+)-doped aperiodically poled lithium niobate crystal. Two fundamental infrared (IR) wavelengths at 1084.8 and 1093.6 nm are simultaneously oscillated and self-frequency-doubled to green. The aperiodic domain distribution patterned in the crystal allows for quasi-phase matched self-frequency-doubling of both IR fundamentals while avoiding their sum-frequency mixing.
Highly efficient 400 W near-fundamental-mode green thin-disk laser.
Piehler, Stefan; Dietrich, Tom; Rumpel, Martin; Graf, Thomas; Ahmed, Marwan Abdou
2016-01-01
We report on the efficient generation of continuous-wave, high-brightness green laser radiation. Green lasers are particularly interesting for reliable and reproducible deep-penetration welding of copper or for pumping Ti:Sa oscillators. By intracavity second-harmonic generation in a thin-disk laser resonator designed for fundamental-mode operation, an output power of up to 403 W is demonstrated at a wavelength of 515 nm with almost diffraction-limited beam quality. The unprecedented optical efficiency of 40.7% of green output power with respect to the pump power of the thin-disk laser is enabled by the intracavity use of a highly efficient grating waveguide mirror, which combines the functions of wavelength stabilization and spectral narrowing, as well as polarization selection in a single element.
Ubbink, D. T.; Tulevski, I. I.; Jacobs, M. J.
2000-01-01
The recently developed green laser (GL; wavelength 543 nm) is thought to measure perfusion derived from a more superficial skin layer than does the standard near-infrared laser (RL; wavelength 780 nm). These lasers were used to investigate the disturbances in the different layers of skin perfusion
International Nuclear Information System (INIS)
Kennedy, Craig J.; Vest, Marie; Cooper, Martin; Wess, Tim J.
2004-01-01
Laser cleaning of parchment is a novel technique that has the potential to provide contactless, chemical-free cleaning of historically important documents. However, the effect of laser cleaning on the collagenous structure of parchment is still poorly understood, as is the effect of the wavelength or the energy density (fluence level) used to clean parchment. In this study, small angle X-ray scattering (SAXS), shrinkage temperature (Ts) measurements by the micro hot table technique and SDS-polyacrylamide gel electrophoresis (SDS-PAGE) of parchment samples after laser cleaning reveal the effect of cleaning to the structural, thermal and molecular characteristics of parchment, respectively. The effect of cleaning at infrared (1064 nm), green (532 nm) and ultraviolet (266 nm) wavelengths at a range of fluence levels is investigated. SAXS is used to investigate the removal of dirt from parchment. Laser cleaning at IR or green wavelengths appears not to alter the collagen diffraction pattern from SAXS, the shrinkage activity or shrinkage temperature from Ts measurements or the molecular integrity of parchment as shown by SDS-PAGE. However, parchments cleaned at the ultraviolet wavelength display structural damage and a reduction in hydrothermal stability and molecular integrity
Process Studies on Laser Welding of Copper with Brilliant Green and Infrared Lasers
Engler, Sebastian; Ramsayer, Reiner; Poprawe, Reinhart
Copper materials are classified as difficult to weld with state-of-the-art lasers. High thermal conductivity in combination with low absorption at room temperature require high intensities for reaching a deep penetration welding process. The low absorption also causes high sensitivity to variations in surface conditions. Green laser radiation shows a considerable higher absorption at room temperature. This reduces the threshold intensity for deep penetration welding significantly. The influence of the green wavelength on energy coupling during heat conduction welding and deep penetration welding as well as the influence on the weld shape has been investigated.
Wavelength sweepable laser source
DEFF Research Database (Denmark)
2014-01-01
Wavelength sweepable laser source is disclosed, wherein the laser source is a semiconductor laser source adapted for generating laser light at a lasing wavelength. The laser source comprises a substrate, a first reflector, and a second reflector. The first and second reflector together defines...... and having a rest position, the second reflector and suspension together defining a microelectromechanical MEMS oscillator. The MEMS oscillator has a resonance frequency and is adapted for oscillating the second reflector on either side of the rest position.; The laser source further comprises electrical...... connections adapted for applying an electric field to the MEMS oscillator. Furthermore, a laser source system and a method of use of the laser source are disclosed....
Influence of ablation wavelength and time on optical properties of laser ablated carbon dots
Isnaeni, Hanna, M. Yusrul; Pambudi, A. A.; Murdaka, F. H.
2017-01-01
Carbon dots, which are unique and applicable materials, have been produced using many techniques. In this work, we have fabricated carbon dots made of coconut fiber using laser ablation technique. The purpose of this work is to evaluate two ablation parameters, which are ablation wavelength and ablation time. We used pulsed laser from Nd:YAG laser with emit wavelength at 355 nm, 532 nm and 1064 nm. We varied ablation time one hour and two hours. Photoluminescence and time-resolved photoluminescence setup were used to study the optical properties of fabricated carbon dots. In general, fabricated carbon dots emit bluish green color emission upon excitation by blue laser. We found that carbon dots fabricated using 1064 nm laser produced the highest carbon dots emission among other samples. The peak wavelength of carbon dots emission is between 495 nm until 505 nm, which gives bluish green color emission. Two hours fabricated carbon dots gave four times higher emission than one hour fabricated carbon dot. More emission intensity of carbon dots means more carbon dots nanoparticles were fabricated during laser ablation process. In addition, we also measured electron dynamics of carbon dots using time-resolved photoluminescence. We found that sample with higher emission has longer electron decay time. Our finding gives optimum condition of carbon dots fabrication from coconut fiber using laser ablation technique. Moreover, fabricated carbon dots are non-toxic nanoparticles that can be applied for health, bio-tagging and medical applications.
1 CW green self-frequency-doubled Yb:YAl3(BO3)4 laser
International Nuclear Information System (INIS)
Dekker, P.; Dawes, J.; Wang, P.; Piper, J.
2000-01-01
Full text: We report 1.1 W continuous wave (CW) green output from a 977nm diode-end-pumped self-frequency-doubled Yb:YAB laser, with a diode-to-green optical conversion efficiency of 10%. Wavelength tunability from 513-546nm has been demonstrated
Li, Q.; Jia, Z. X.; Weng, H. Z.; Li, Z. R.; Yang, Y. D.; Xiao, J. L.; Chen, S. W.; Huang, Y. Z.; Qin, W. P.; Qin, G. S.
2018-05-01
We demonstrate broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm and a frequency separation of ~9.28 GHz generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity. By using one continuous-wave laser as the pump source, multi-wavelength Brillouin lasers with an operating wavelength range of 1554–1574 nm were generated via cascaded Brillouin scattering and four-wave mixing. Interestingly, when pumped by two continuous-wave lasers with an appropriate frequency separation, the operating wavelength range of the multi-wavelength Brillouin lasers was increased to 1500–1600 nm due to cavity-enhanced cascaded four-wave mixing among the frequency components generated by two pump lasers in the dual wavelength Brillouin laser cavity.
Stefan, V. Alexander
2015-11-01
The interaction of ultrashort wavelength multi laser beams with the flowing blood thin films leads to the transmutation of the blood types A, B, and AB into O type. This is a novel mechanism of importance for the transfusion medicine. Laser radiation is in resonance with the eigen-frequency modes of the antigen proteins and forces the proteins to parametrically oscillate until they get kicked out from the surface. The stripping away of antigens is done by the scanning-multiple-lasers of a high repetition rate in the blue-purple frequency domain. The guiding-lasers are in the red-green frequency domain. The laser force, (parametric interaction with the antigen eigen-oscillation), upon the antigen protein molecule must exceed its weight. The scanning laser beam is partially reflected as long as the antigen(s) is not eliminated. The process of the protein detachment can last a few minutes. Supported by Nikola Tesla Labs., Stefan University.
A 12 GHz wavelength spacing multi-wavelength laser source for wireless communication systems
Peng, P. C.; Shiu, R. K.; Bitew, M. A.; Chang, T. L.; Lai, C. H.; Junior, J. I.
2017-08-01
This paper presents a multi-wavelength laser source with 12 GHz wavelength spacing based on a single distributed feedback laser. A light wave generated from the distributed feedback laser is fed into a frequency shifter loop consisting of 50:50 coupler, dual-parallel Mach-Zehnder modulator, optical amplifier, optical filter, and polarization controller. The frequency of the input wavelength is shifted and then re-injected into the frequency shifter loop. By re-injecting the shifted wavelengths multiple times, we have generated 84 optical carriers with 12 GHz wavelength spacing and stable output power. For each channel, two wavelengths are modulated by a wireless data using the phase modulator and transmitted through a 25 km single mode fiber. In contrast to previously developed schemes, the proposed laser source does not incur DC bias drift problem. Moreover, it is a good candidate for radio-over-fiber systems to support multiple users using a single distributed feedback laser.
A Multi-Wavelength IR Laser for Space Applications
Li, Steven X.; Yu, Anthony W.; Sun, Xiaoli; Fahey, Molly E.; Numata, Kenji; Krainak, Michael A.
2017-01-01
We present a laser technology development with space flight heritage to generate laser wavelengths in the near- to mid-infrared (NIR to MIR) for space lidar applications. Integrating an optical parametric crystal to the LOLA (Lunar Orbiter Laser Altimeter) laser transmitter design affords selective laser wavelengths from NIR to MIR that are not easily obtainable from traditional diode pumped solid-state lasers. By replacing the output coupler of the LOLA laser with a properly designed parametric crystal, we successfully demonstrated a monolithic intra-cavity optical parametric oscillator (iOPO) laser based on all high technology readiness level (TRL) subsystems and components. Several desired wavelengths have been generated including 2.1 microns, 2.7 microns and 3.4 microns. This laser can also be used in trace-gas remote sensing, as many molecules possess their unique vibrational transitions in NIR to MIR wavelength region, as well as in time-of-flight mass spectrometer where desorption of samples using MIR laser wavelengths have been successfully demonstrated.
DEFF Research Database (Denmark)
Jensen, Ole Bjarlin
2010-01-01
Well over a dozen papers at this year's Photonics West meeting in San Francisco boasted improvements in harmonic generation to produce visible laser beams, most of them in the green spectral range......Well over a dozen papers at this year's Photonics West meeting in San Francisco boasted improvements in harmonic generation to produce visible laser beams, most of them in the green spectral range...
Wavelength stabilized multi-kW diode laser systems
Köhler, Bernd; Unger, Andreas; Kindervater, Tobias; Drovs, Simon; Wolf, Paul; Hubrich, Ralf; Beczkowiak, Anna; Auch, Stefan; Müntz, Holger; Biesenbach, Jens
2015-03-01
We report on wavelength stabilized high-power diode laser systems with enhanced spectral brightness by means of Volume Holographic Gratings. High-power diode laser modules typically have a relatively broad spectral width of about 3 to 6 nm. In addition the center wavelength shifts by changing the temperature and the driving current, which is obstructive for pumping applications with small absorption bandwidths. Wavelength stabilization of high-power diode laser systems is an important method to increase the efficiency of diode pumped solid-state lasers. It also enables power scaling by dense wavelength multiplexing. To ensure a wide locking range and efficient wavelength stabilization the parameters of the Volume Holographic Grating and the parameters of the diode laser bar have to be adapted carefully. Important parameters are the reflectivity of the Volume Holographic Grating, the reflectivity of the diode laser bar as well as its angular and spectral emission characteristics. In this paper we present detailed data on wavelength stabilized diode laser systems with and without fiber coupling in the spectral range from 634 nm up to 1533 nm. The maximum output power of 2.7 kW was measured for a fiber coupled system (1000 μm, NA 0.22), which was stabilized at a wavelength of 969 nm with a spectral width of only 0.6 nm (90% value). Another example is a narrow line-width diode laser stack, which was stabilized at a wavelength of 1533 nm with a spectral bandwidth below 1 nm and an output power of 835 W.
Speckle noise reduction on a laser projection display via a broadband green light source.
Yu, Nan Ei; Choi, Ju Won; Kang, Heejong; Ko, Do-Kyeong; Fu, Shih-Hao; Liou, Jiun-Wei; Kung, Andy H; Choi, Hee Joo; Kim, Byoung Joo; Cha, Myoungsik; Peng, Lung-Han
2014-02-10
A broadband green light source was demonstrated using a tandem-poled lithium niobate (TPLN) crystal. The measured wavelength and temperature bandwidth were 6.5 nm and 100 °C, respectively, spectral bandwidth was 36 times broader than the periodically poled case. Although the conversion efficiency was smaller than in the periodic case, the TPLN device had a good figure of merit owing to the extremely large bandwidth for wavelength and temperature. The developed broadband green light source exhibited speckle noise approximately one-seventh of that in the conventional approach for a laser projection display.
Multi-wavelength lasers using AWGs
Besten, den J.H.
2003-01-01
Multiwavelength lasers using AWGs can be used as digitally tunable lasers with simple channel selection, and for generating multiple wavelengths simultanously. In this paper a number of different configurations is reviewed.
Lee, Eunjoo; Kim, Byoung Yoon
2017-12-01
We propose a new scheme for an actively mode-locked wavelength-swept fiber laser that produces a train of discretely wavelength-stepped pulses from a short fiber cavity. Pulses with different wavelengths are split and combined by standard wavelength division multiplexers with fiber delay lines. As a proof of concept, we demonstrate a laser using an erbium doped fiber amplifier and commercially available wavelength-division multiplexers with wavelength spacing of 0.8 nm. The results show simultaneous mode-locking at three different wavelengths. Laser output parameters in time domain, optical and radio frequency spectral domain, and the noise characteristics are presented. Suggestions for the improved design are discussed.
Wright, E J; Poppas, D P
1997-01-01
Successful tissue approximation can be performed using low power laser energy combined with human albumin solder. In vitro studies were undertaken to investigate the acute repair strengths achieved using different laser wavelengths. Furthermore, we evaluated the change in repair strength with that resulted from changes in protein solder concentration. Intraluminal bursting pressure following ureterotomy repair was measured for the following laser wavelengths: 532, 808, 1,320, 2,100, and 10,600 nm. The tissue absorption characteristics of the 808-nm diode and the KTP-532-nm lasers required the addition of the exogenous chromophores indocyanine green and fluorescein, respectively. A 40% human albumin solder was incorporated in the repair of a 1.0-cm longitudinal defect in the canine ureter. Following determination of an optimal welding wavelength, human albumin solder of varying concentrations (25%, 38%, 45%, and 50%) were prepared and tested. The 1,320-nm YAG laser achieved the highest acute bursting pressure and was the most effective in this model. Of the concentrations of albumin tested, 50% human albumin yielded the greatest bursting pressures. We conclude that of the laser wavelengths evaluated, the 1,320-nm YAG achieves the strongest tissue weld in the acute ex vivo dog ureter model. In addition, when this laser system is used, the acute strength of a photothermal weld appears to be directly proportional to the concentration of human albumin solder in the range of 25 to 50%.
Improvement of a triple-wavelength erbium-doped fiber laser using a Fabry–Perot laser diode
International Nuclear Information System (INIS)
Peng, P C; Hu, H L; Wang, J B
2013-01-01
This work demonstrates the feasibility of a simple construct of a tunable triple-wavelength fiber ring laser using a Fabry–Perot laser diode (FP-LD) and an optical tunable bandpass filter. An optical tunable bandpass filter is used within the cavity of an erbium-doped fiber laser to select the lasing wavelength. Because the Fabry–Perot laser diode is in combination with the tunable bandpass filter, the erbium-doped fiber laser can stably lase three wavelengths simultaneously. Moreover, this laser is easily tuned dynamically. This triple-wavelength output performs satisfactorily, with its optical side-mode-suppression-ratio (SMSR) exceeding 40 dB. Furthermore, the wavelength tuning range of this triple-wavelength erbium-doped fiber laser is greater than 27 nm. (paper)
Research with high-power short-wavelength lasers
International Nuclear Information System (INIS)
Holzrichter, J.F.; Campbell, E.M.; Lindl, J.D.; Storm, E.
1985-01-01
Three important high-temperature, high-density experiments were conducted recently using the 10-TW, short-wavelength Novette laser system at the Lawrence Livermore National Laboratory. These experiments demonstrated successful solutions to problems that arose during previous experiments with long wavelength lasers (lambda greater than or equal to 1μm) in which inertial confinement fusion (ICF), x-ray laser, and other high-temperature physics concepts were being tested. The demonstrations were: (1) large-scale plasmas (typical dimensions of up to 1000 laser wavelengths) were produced in which potentially deleterious laser-plasma instabilities were collisionally damped. (2) Deuterium-tritium fuel was imploded to a density of 20 g/cm 3 and a pressure of 10 10 atm. (3) A 700-fold amplification of soft x rays by stimulated emission at 206 and 209 A (62 eV) from Se +24 ions was observed in a laser-generated plasma. Isoelectronic scaling to 155 A (87 eV) in Y +29 was also demonstrated
International Nuclear Information System (INIS)
Sun, G C; Li, Y D; Zhao, M; Chen, X Y; Wang, J B; Chen, G B
2013-01-01
A diode-end-pumped Yb:YAG dual-wavelength continuous-wave (cw) laser that generates simultaneous laser action at wavelengths of 1024 and 1030 nm is demonstrated for the first time. A total output power of 897 mW for the dual-wavelength was achieved at an incident pump power of 17.8 W. Furthermore, intracavity sum-frequency mixing at 1024 and 1030 nm was then realized in an LBO crystal to reach the green range. We obtained a total cw output power of 85 mW at 513.5 nm. (paper)
Review of short wavelength lasers
International Nuclear Information System (INIS)
Hagelstein, P.L.
1985-01-01
There has recently been a substantial amount of research devoted to the development of short wavelength amplifiers and lasers. A number of experimental results have been published wherein the observation of significant gain has been claimed on transitions in the EUV and soft x-ray regimes. The present review is intended to discuss the main approaches to the creation of population inversions and laser media in the short wavelength regime, and hopefully aid workers in the field by helping to provide access to a growing literature. The approaches to pumping EUV and soft x-ray lasers are discussed according to inversion mechanism. The approaches may be divided into roughly seven categories, including collisional excitation pumping, recombination pumping, direct photoionization and photoexcitation pumping, metastable state storage plus optical pumping, charge exchange pumping, and finally, the extension of free electron laser techniques into the EUV and soft x-ray regimes. 250 references
Review of short wavelength lasers
Energy Technology Data Exchange (ETDEWEB)
Hagelstein, P.L.
1985-03-18
There has recently been a substantial amount of research devoted to the development of short wavelength amplifiers and lasers. A number of experimental results have been published wherein the observation of significant gain has been claimed on transitions in the EUV and soft x-ray regimes. The present review is intended to discuss the main approaches to the creation of population inversions and laser media in the short wavelength regime, and hopefully aid workers in the field by helping to provide access to a growing literature. The approaches to pumping EUV and soft x-ray lasers are discussed according to inversion mechanism. The approaches may be divided into roughly seven categories, including collisional excitation pumping, recombination pumping, direct photoionization and photoexcitation pumping, metastable state storage plus optical pumping, charge exchange pumping, and finally, the extension of free electron laser techniques into the EUV and soft x-ray regimes. 250 references.
Eitel, J.; Magney, T. S.; Vierling, L. A.; Brown, T. T.; Huggins, D. R.
2012-12-01
Reducing fertilizer inputs while maintaining yield would increase farmer's profits and similarly lessen the adverse environmental effects of production agriculture. The development of technologies that allow precise, site-specific application of Nitrogen (N) fertilizer has thus been an important research goal over the past decades. Remote sensing of foliar crop properties and function with tractor-mountable optical sensors has thought to be useful to optimize N fertilizer applications. However, on-the-go sensing of foliar crop properties and function has proven difficult, particularly during early crop growth stages when fertilizer decisions are often made. This difficulty arises from the fact that the spectral signal measured by on-the-go sensors is dominated by soil reflectance during early crop growth stages. Here, we present the basic principles behind a novel, dual-wavelength, tractor mountable laser altimetry system that measures the laser return intensity of the reflected green and red laser light. The green (532 nm) and the red (660 nm) wavelength combination allows calculation of a modified Photochemical Reflectance Index (mPRI) that have shown to be sensitive to both crop function and foliar chemistry. The small field of view of the laser points (diameter: 4 mm) combined with its high sampling rate (1000 points sec-1) allows vegetation returns to be isolated from ground returns by using simple thresholds. First tests relating foliar N of winter wheat (Triticum aestivum L.) with laser derived mPRI are promising (r2 = 0.72). Further research is needed to test the relationship between laser derived spectral indices and crop function.
Laser warning receiver to identify the wavelength and angle of arrival of incident laser light
Sinclair; Michael B.; Sweatt, William C.
2010-03-23
A laser warning receiver is disclosed which has up to hundreds of individual optical channels each optically oriented to receive laser light from a different angle of arrival. Each optical channel has an optical wedge to define the angle of arrival, and a lens to focus the laser light onto a multi-wavelength photodetector for that channel. Each multi-wavelength photodetector has a number of semiconductor layers which are located in a multi-dielectric stack that concentrates the laser light into one of the semiconductor layers according to wavelength. An electrical signal from the multi-wavelength photodetector can be processed to determine both the angle of arrival and the wavelength of the laser light.
Bora, Mihail; Bond, Tiziana C.
2016-04-19
A plasmonic laser device has resonant nanocavities filled with a gain medium containing an organic dye. The resonant plasmon frequencies of the nanocavities are tuned to align with both the absorption and emission spectra of the dye. Variables in the system include the nature of the dye and the wavelength of its absorption and emission, the wavelength of the pumping radiation, and the resonance frequencies of the nanocavities. In addition the pumping frequency of the dye is selected to be close to the absorption maximum.
5W intracavity frequency-doubled green laser for laser projection
Yan, Boxia; Bi, Yong; Li, Shu; Wang, Dongdong; Wang, Dongzhou; Qi, Yan; Fang, Tao
2014-11-01
High power green laser has many applications such as high brightness laser projection and large screen laser theater. A compact and high power green-light source has been developed in diode-pumped solid-state laser based on MgO doped periodically poled LiNbO3 (MgO:PPLN). 5W fiber coupled green laser is achieved by dual path Nd:YVO4/MgO:PPLN intra-cacity frequency-doubled. Single green laser maximum power 2.8W at 532nm is obtained by a 5.5W LD pumped, MgO:PPLN dimensions is 5mm(width)×1mm(thickness)×2mm(length), and the optical to optical conversion efficiency is 51%. The second LD series connected with the one LD, the second path green laser is obtained using the same method. Then the second path light overlap with the first path by the reflection mirrors, then couple into the fiber with a focus mirror. Dual of LD, Nd:YVO4, MgO:PPLN are placed on the same heat sink using a TEC cooling, the operating temperature bandwidth is about 12°C and the stablity is 5% in 96h. A 50×50×17mm3 laser module which generated continuous-wave 5 W green light with high efficiency and width temperature range is demonstrated.
Wavelength scaling of laser plasma coupling
International Nuclear Information System (INIS)
Kruer, W.L.
1983-01-01
The use of shorter wavelength laser light both enhances collisional absorption and reduces deleterious collective plasma effects. Coupling processes which can be important in reactor-size targets are briefly reviewed. Simple estimates are presented for the intensity-wavelength regime in which collisional absorption is high and collective effects are minimized
Method of stabilizing a laser apparatus with wavelength converter
DEFF Research Database (Denmark)
2013-01-01
and to output the frequency-converted radiation (213), the frequency-converted radiation having at least a second wavelength different from the first wavelength, the diode laser (10) comprising at least a first and a second section (222,223), a first contact (220) for injecting a first current (I1......) into the first section (222), a second contact (221) for injecting a second current (I2) into the second section (223), and means for controlling a temperature of the diode laser; wherein the method comprises monitoring a first parameter indicative of the power content of a dominant lobe of the first radiation......A method of controlling beam quality and stability of a laser apparatus, the laser apparatus comprising, a diode laser (10) providing first radiation of at least a first wavelength, and a frequency conversion unit (12) configured to frequency-convert the first radiation from the diode laser...
Generation of single-frequency tunable green light in a coupled ring tapered diode laser cavity
DEFF Research Database (Denmark)
Jensen, Ole Bjarlin; Petersen, Paul Michael
2013-01-01
in the broad wavelength range from 1049 nm to 1093 nm and the beam propagation factor is improved from M2 = 2.8 to below 1.1. The laser frequency is automatically locked to the cavity resonance frequency using optical feedback. Furthermore, we show that this adaptive external cavity approach leads to efficient......We report the realization of a tapered diode laser operated in a coupled ring cavity that significantly improves the coherence properties of the tapered laser and efficiently generates tunable light at the second harmonic frequency. The tapered diode laser is tunable with single-frequency output...... frequency doubling. More than 500 mW green output power is obtained by placing a periodically poled LiNbO3 crystal in the external cavity. The single frequency green output from the laser system is tunable in the 530 nm to 533 nm range limited by the LiNbO3 crystal. The optical to optical conversion...
Three wavelength optical alignment of the Nova laser
International Nuclear Information System (INIS)
Swift, C.D.; Bliss, E.S.; Jones, W.A.; Seppala, L.G.
1983-01-01
The Nova laser, presently under construction at Lawrence Livermore National Laboratory, will be capable of delivering more than 100 kJ of focused energy to an Inertial Confinement Fusion (ICF) target. Operation at the fundamental wavelength of the laser (1.05 μm) and at the second and third harmonic will be possible. This paper will discuss the optical alignment systems and techniques being implemented to align the laser output to the target at these wavelengths prior to each target irradiation. When experiments require conversion of the laser light to wavelengths of 0.53 μm and 0.35 μm prior to target irradiation, this will be accomplished in harmonic conversion crystals located at the beam entrances to the target chamber. The harmonic alignment system will be capable of introducing colinear alignment beams of all three wavelengths into the laser chains at the final spatial filter. The alignment beam at 1.05 μm will be about three cm in diameter and intense enough to align the conversion crystals. Beams at 0.53 μm and 0.35 μm will be expanded by the spatial filter to full aperture (74 cm) and used to illuminate the target and other alignment aids at the target chamber focus. This harmonic illumination system will include viewing capability as well. A final alignment sensor will be located at the target chamber. It will view images of the chamber focal plane at all three wavelengths. In this way, each beam can be aligned at the desired wavelength to produce the focal pattern required for each target irradiation. The design of the major components in the harmonic alignment system will be described, and a typical alignment sequence for alignment to a target will be presented
Optical power calibrator based on a stabilized green He-Ne laser and a cryogenic absolute radiometer
International Nuclear Information System (INIS)
Varpula, T.; Seppa, H.; Saari, J.M.
1989-01-01
This paper describes an optical power calibrator whose overall calibration uncertainty is less than 10 -4 for an optical power of 0.13 mW. The laser light source of the system operates at a wavelength of 543.5 nm, being close to the wavelength at which the candela is defined, 555 nm. A stable optical power is achieved by stabilizing the intensity and the frequency of a green He-Ne laser. The optical power is detected by a cryogenic absolute radiometer based on the principle of electrical substitution radiometry. It can be employed to measure optical power up to 0.5 mW in the visible and near infrared region
Wavelength and ambient luminance dependence of laser eye dazzle.
Williamson, Craig A; McLin, Leon N; Rickman, J Michael; Manka, Michael A; Garcia, Paul V; Kinerk, Wesley T; Smith, Peter A
2017-10-10
A series of experiments has been conducted to quantify the effects of laser wavelength and ambient luminance on the severity of laser eye dazzle experienced by human subjects. Eight laser wavelengths in the visible spectrum were used (458-647 nm) across a wide range of ambient luminance conditions (0.1-10,000 cd·m -2 ). Subjects were exposed to laser irradiance levels up to 600 μW·cm -2 and were asked to recognize the orientation of optotypes at varying eccentricities up to 31.6 deg of visual angle from the laser axis. More than 40,000 data points were collected from 14 subjects (ages 23-64), and these were consolidated into a series of obscuration angles for comparison to a theoretical model of laser eye dazzle. Scaling functions were derived to allow the model to predict the effects of laser dazzle on vision more accurately by including the effects of ambient luminance and laser wavelength. The updated model provides an improved match to observed laser eye dazzle effects across the full range of conditions assessed. The resulting model will find use in a variety of laser safety applications, including the estimation of maximum dazzle exposure and nominal ocular dazzle distance values.
Vertical integration of dual wavelength index guided lasers
Karouta, F.; Tan, H.H.; Jagadish, C.; Roy, van B.H.
1999-01-01
The vertical integration of two GaAs-based lasers operating at different wavelengths has been achieved with the use of re-growth technology. A V-channel substrate inner stripe structure was used for the bottom laser and a ridge waveguide for the top laser. Both lasers shared a common electrode and
Bai, Xueshi; Syvilay, Delphine; Wilkie-Chancellier, Nicolas; Texier, Annick; Martinez, Loic; Serfaty, Stéphane; Martos-Levif, Dominique; Detalle, Vincent
2017-08-01
The influence of ns-laser wavelength to discriminate ancient painting techniques such as are fresco, casein, animal glue, egg yolk and oil was investigated in this work. This study was carried out with a single shot laser on samples covered by a layer made of a mixture of the cinnabar pigment and different binders. Three wavelengths based on Nd: YAG laser were investigated (1064, 532 and 266 nm). The plasma is controlled at the same electron temperature after an adjustment of pulse energy for these three wavelengths on a fresco sample without organic binder. This approach allows to eliminate the effects of laser pulse energy and the material laser absorption. Afterwards, the emission spectra were compared to separate different techniques. The organic binding media has been separated based on the relative emission intensity of the present CN or C2 rovibrational emissions. In order to test the capability of separating or identifying, the chemometric approach (PCA) was applied to the different matrix. The different solutions in term of wavelength range to optimise the identification was investigated. We focused on the evaluation for the laser wavelength to insure a better separation. The different capacity was interpreted by differentiating the binders by the altered interaction mechanisms between the laser photon and the binders. Also, the electron temperature in the plasma was estimated, which provided the evidences to our findings.
Characterization of FBG sensor interrogation based on a FDML wavelength swept laser
Jung, Eun Joo; Kim, Chang-Seok; Jeong, Myung Yung; Kim, Moon Ki; Jeon, Min Yong; Jung, Woonggyu; Chen, Zhongping
2012-01-01
In this study, we develop an ultra-fast fiber Bragg grating sensor system that is based on the Fourier domain mode-locked (FDML) swept laser. A FDML wavelength swept laser has many advantages compared to the conventional wavelength swept laser source, such as high-speed interrogation, narrow spectral sensitivity, and high phase stability. The newly developed FDML wavelength swept laser shows a superior performance of a high scan rate of 31.3 kHz and a broad scan range of over 70 nm simultaneously. The performance of the grating sensor interrogating system using a FDML wavelength swept laser is characterized in both static and dynamic strain responses. PMID:18852764
Metallic nano-cavity lasers at near infrared wavelengths
Hill, M.T.; Stockman, M.I.
2009-01-01
There has been considerable interest in nano-cavity lasers, both from a scientific perspective for investigating fundamental properties of lasers and cavities, and also to produce smaller and better lasers for low-power applications. Light confinement on a wavelength scale has been reported in
MoS2-wrapped microfiber-based multi-wavelength soliton fiber laser
Lu, Feifei
2017-11-01
The single-, dual- and triple-wavelength passively mode-locked erbium-doped fiber lasers are demonstrated with MoS2 and polarization-dependent isolator (PD-ISO). The saturable absorber is fabricated by wrapping an MoS2 around a microfiber. The intracavity PD-ISO acts as a wavelength-tunable filter with a polarization controller (PC) by adjusting the linear birefringence. Single-wavelength mode-locked fiber laser can self-start with suitable pump power. With appropriate PC state, dual- and triple-wavelength operations can be observed when gains at different wavelengths reach a balance. It is noteworthy that dual-wavelength pulses exhibiting peak and dip sidebands, respectively, are demonstrated in the experiment. The proposed simple and multi-wavelength all-fiber conventional soliton lasers could possess potential applications in numerous fields, such as sensors, THz generations and optical communications.
Maxwell, Eric J; Tong, William G
2016-05-01
An ultrasensitive label-free antibody-free detection method for malachite green and crystal violet is presented using nonlinear laser wave-mixing spectroscopy and capillary zone electrophoresis. Wave-mixing spectroscopy provides a sensitive absorption-based detection method for trace analytes. This is accomplished by forming dynamic gratings within a sample cell, which diffracts light to create a coherent laser-like signal beam with high optical efficiency and high signal-to-noise ratio. A cubic dependence on laser power and square dependence on analyte concentration make wave mixing sensitive enough to detect molecules in their native form without the use of fluorescent labels for signal enhancement. A 532 nm laser and a 635 nm laser were used for malachite green and crystal violet sample excitation. The use of two lasers of different wavelengths allows the method to simultaneously detect both analytes. Selectivity is obtained through the capillary zone electrophoresis separation, which results in characteristic migration times. Measurement in capillary zone electrophoresis resulted in a limit of detection of 6.9 × 10(-10)M (2.5 × 10(-19) mol) for crystal violet and 8.3 × 10(-11)M (3.0 × 10(-20) mol) for malachite green at S/N of 2. Copyright © 2016. Published by Elsevier B.V.
DEFF Research Database (Denmark)
Jensen, Ole Bjarlin; Andersen, Peter E.; Sumpf, Bernd
2009-01-01
More than 1.5 W of green light at 531 nm is generated by singlepass second harmonic generation in periodically poled MgO:LiNbO3. The pump laser is a high power tapered laser with a distributed Bragg reflector etched in the ridge section of the laser to provide wavelength selectivity. The output...... power of the single-frequency tapered laser is 9.3 W in continuous wave operation. A conversion efficiency of 18.5 % was achieved in the experiments....
Laser surface modification of polyethersulfone films: effect of laser wavelength on biocompatibility
International Nuclear Information System (INIS)
Pazokian, H; Jelvani, S; Mollabashi, M; Barzin, J
2013-01-01
In this paper laser ablation of polyethersulfone (PES) films regarding to the change in biocompatibility of the surface is investigated at 3 different wavelengths of 193nm (ArF), 248 nm (KrF) and 308 nm (XeCl). The optimum laser fluence and number of pulses for the improvement of the surface biocompatibility is found by examination of the surface behavior in contact with platelets and fibroblasts cells at 3 wavelengths. These biological modifications are explained by alteration of the surface morphology and chemistry following irradiation. The results show that the KrF laser is the best choice for treatment of PES in biological applications.
Cluster dynamics at different cluster size and incident laser wavelengths
International Nuclear Information System (INIS)
Desai, Tara; Bernardinello, Andrea
2002-01-01
X-ray emission spectra from aluminum clusters of diameter -0.4 μm and gold clusters of dia. ∼1.25 μm are experimentally studied by irradiating the cluster foil targets with 1.06 μm laser, 10 ns (FWHM) at an intensity ∼10 12 W/cm 2 . Aluminum clusters show a different spectra compared to bulk material whereas gold cluster evolve towards bulk gold. Experimental data are analyzed on the basis of cluster dimension, laser wavelength and pulse duration. PIC simulations are performed to study the behavior of clusters at higher intensity I≥10 17 W/cm 2 for different size of the clusters irradiated at different laser wavelengths. Results indicate the dependence of cluster dynamics on cluster size and incident laser wavelength
Emission wavelength of multilayer distributed feedback dye lasers
DEFF Research Database (Denmark)
Vannahme, Christoph; Smith, Cameron L. C.; Brøkner Christiansen, Mads
2012-01-01
Precise emission wavelength modeling is essential for understanding and optimization of distributed feedback (DFB) lasers. An analytical approach for determining the emission wavelength based on setting the propagation constant of the Bragg condition and solving for the resulting slab waveguide m...
2μm all fiber multi-wavelength Tm/Ho co-doped fiber laser
Zhang, Junhong; Jiang, Qiuxia; Wang, Xiaofa
2017-10-01
A 2 μm all fiber multi-wavelength Tm/Ho co-doped fiber laser based on a simple ring cavity is experimentally demonstrated. Compared with other 2 μm multi-wavelength Tm/Ho co-doped fiber lasers, the multi-wavelength fiber laser is obtained by the gain saturation effect and inhomogeneous broadening effect without any frequency selector component, filter component or polarization-dependent component. When the pump power is about 304 mW, the fiber laser enters into single-wavelength working state around 1967.76 nm. Further increasing the pump power to 455 mW, a stable dual-wavelength laser is obtained at room temperature. The bimodal power difference between λ1 and λ2 is 5.528 dB. The fluctuations of wavelength and power are less than 0.03 nm and 0.264 dB in an hour, which demonstrates that the multi-wavelength fiber laser works at a stable state. Furthermore, a research about the relationship between the pump power and the output spectra has been made.
Choice of the laser wavelength for a herpetic keratitis treatment
Razhev, Alexander M.; Bagayev, Sergei N.; Chernikh, Valery V.; Kargapoltsev, Evgeny S.; Trunov, Alexander; Zhupikov, Andrey A.
2002-06-01
For the first time the effect of the UV laser radiation to human eye cornea with herpetic keratitis was experimentally investigated. In experiments the UV radiation of ArF (193 nm), KrCl (223 nm), KrF (248 nm) excimer lasers were used. Optimal laser radiation parameters for the treatment of the herpetic keratitis were determined. The immuno-biochemical investigations were carried out and the results of clinical trials are presented. The maximum ablation rate was obtained for the 248 nm radiation wavelength. The process of healing was successful but in some cases the haze on the surface of the cornea was observed. When used the 193 nm radiation wavelength the corneal surface was clear without any hazes but the epithelization process was slower than for 248 nm wavelength and in some cases the relapse was occurred. The best results for herpetic keratitis treatment have been achieved by utilizing the 223 nm radiation wavelength of the KrCl excimer laser. The use of the 223 nm radiation wavelength allows treating the herpetic keratitis with low traumatic process of ablation and provides high quality of corneal surface.
Sun, K.; Chao, X.; Sur, R.; Goldenstein, C. S.; Jeffries, J. B.; Hanson, R. K.
2013-12-01
A novel strategy has been developed for analysis of wavelength-scanned, wavelength modulation spectroscopy (WMS) with tunable diode lasers (TDLs). The method simulates WMS signals to compare with measurements to determine gas properties (e.g., temperature, pressure and concentration of the absorbing species). Injection-current-tuned TDLs have simultaneous wavelength and intensity variation, which severely complicates the Fourier expansion of the simulated WMS signal into harmonics of the modulation frequency (fm). The new method differs from previous WMS analysis strategies in two significant ways: (1) the measured laser intensity is used to simulate the transmitted laser intensity and (2) digital lock-in and low-pass filter software is used to expand both simulated and measured transmitted laser intensities into harmonics of the modulation frequency, WMS-nfm (n = 1, 2, 3,…), avoiding the need for an analytic model of intensity modulation or Fourier expansion of the simulated WMS harmonics. This analysis scheme is valid at any optical depth, modulation index, and at all values of scanned-laser wavelength. The method is demonstrated and validated with WMS of H2O dilute in air (1 atm, 296 K, near 1392 nm). WMS-nfm harmonics for n = 1 to 6 are extracted and the simulation and measurements are found in good agreement for the entire WMS lineshape. The use of 1f-normalization strategies to realize calibration-free wavelength-scanned WMS is also discussed.
Free-space QKD system hacking by wavelength control using an external laser.
Lee, Min Soo; Woo, Min Ki; Jung, Jisung; Kim, Yong-Su; Han, Sang-Wook; Moon, Sung
2017-05-15
We develop a way to hack free-space quantum key distribution (QKD) systems by changing the wavelength of the quantum signal laser using an external laser. Most free-space QKD systems use four distinct lasers for each polarization, thereby making the characteristics of each laser indistinguishable. We also discover a side-channel that can distinguish the lasers by using an external laser. Our hacking scheme identifies the lasers by automatically applying the external laser to each signal laser at different intensities and detecting the wavelength variation according to the amount of incident external laser power. We conduct a proof-of-principle experiment to verify the proposed hacking structure and confirm that the wavelength varies by several gigahertzes to several nanometers, depending on the intensity of the external laser. The risk of hacking is successfully proven through the experimental results. Methods for prevention are also suggested.
Wavelength-tunable colloidal quantum dot laser on ultra-thin flexible glass
Energy Technology Data Exchange (ETDEWEB)
Foucher, C.; Guilhabert, B.; Laurand, N.; Dawson, M. D. [Institute of Photonics, SUPA, University of Strathclyde, Glasgow (United Kingdom)
2014-04-07
A mechanically flexible and wavelength-tunable laser with an ultra-thin glass membrane as substrate is demonstrated. The optically pumped hybrid device has a distributed feedback cavity that combines a colloidal quantum dot gain film with a grating-patterned polymeric underlayer, all on a 30-μm thick glass sheet. The total thickness of the structure is only 75 μm. The hybrid laser has an average threshold fluence of 450 ± 80 μJ/cm{sup 2} (for 5-ns excitation pulses) at an emitting wavelength of 607 nm. Mechanically bending the thin-glass substrate enables continuous tuning of the laser emission wavelength over an 18-nm range, from 600 nm to 618 nm. The correlation between the wavelength tunability and the mechanical properties of the thin laser structure is verified theoretically and experimentally.
High power multiple wavelength diode laser stack for DPSSL application without temperature control
Hou, Dong; Yin, Xia; Wang, Jingwei; Chen, Shi; Zhan, Yun; Li, Xiaoning; Fan, Yingmin; Liu, Xingsheng
2018-02-01
High power diode laser stack is widely used in pumping solid-state laser for years. Normally an integrated temperature control module is required for stabilizing the output power of solid-state laser, as the output power of the solid-state laser highly depends on the emission wavelength and the wavelength shift of diode lasers according to the temperature changes. However the temperature control module is inconvenient for this application, due to its large dimension, high electric power consumption and extra adding a complicated controlling system. Furthermore, it takes dozens of seconds to stabilize the output power when the laser system is turned on. In this work, a compact hard soldered high power conduction cooled diode laser stack with multiple wavelengths is developed for stabilizing the output power of solid-state laser in a certain temperature range. The stack consists of 5 laser bars with the pitch of 0.43mm. The peak output power of each bar in the diode laser stack reaches as much as 557W and the combined lasing wavelength spectrum profile spans 15nm. The solidstate laser, structured with multiple wavelength diode laser stacks, allows the ambient temperature change of 65°C without suddenly degrading the optical performance.
OMEGA: a short-wavelength laser for fusion experiments
International Nuclear Information System (INIS)
Soures, J.M.; Hutchison, R.J.; Jacobs, S.D.; Lund, L.D.; McCrory, R.L.; Richardson, M.C.
1983-01-01
The OMEGA, Nd:glass laser facility was constructed for the purpose of investigating the feasibility of direct-drive laser fusion. With 24 beams producing a total energy of 4 kJ or a peak power of 12 TW, OMEGA is capable of nearly uniform illumination of spherical targets. Six of the OMEGA beams have recently been converted to short-wavelength operation (351 nm). In this paper, we discuss details of the system design and performance, with particular emphasis on the frequency-conversion system and multi-wavelength diagnostic system
Controlling the emission wavelength in group III-V semiconductor laser diodes
Ooi, Boon S.; Majid, Mohammed Abdul; Afandy, Rami; Aljabr, Ahmad
2016-01-01
Methods are provided for modifying the emission wavelength of a semiconductor quantum well laser diode, e.g. by blue shifting the emission wavelength. The methods can be applied to a variety of semiconductor quantum well laser diodes, e.g. group III
Intra-laser-cavity microparticle sensing with a dual-wavelength distributed-feedback laser
Bernhardi, Edward H.; van der Werf, Kees O; Hollink, Anton J F; Wörhoff, Kerstin; de Ridder, René M; Subramaniam, Vinod; Pollnau, Markus
An integrated intra-laser-cavity microparticle sensor based on a dual-wavelength distributed-feedback channel waveguide laser in ytterbium-doped amorphous aluminum oxide on a silicon substrate is demonstrated. Real-time detection and accurate size measurement of single micro-particles with diameters
DEFF Research Database (Denmark)
2015-01-01
The present invention relates to a method and a wavelength tunable laser comprising a first laser source configured to emit a first optical pulse having a pump wavelength, the first optical pulse being emitted in a first longitudinal direction. Furthermore, the wavelength tunable laser comprises...... a waveguide extending in the first longitudinal direction, the waveguide having longitudinally varying phase matching conditions, the waveguide being configured to generate a second optical pulse with a centre wavelength upon receiving the first optical pulse, wherein the wavelength tunable laser...... is configured to tune the centre wavelength of the second optical pulse by varying at least one pulse property of the first optical pulse....
Excision of oral mucocele by different wavelength lasers
Directory of Open Access Journals (Sweden)
Umberto Romeo
2013-01-01
Full Text Available Background: Mucocele is a common benign neoplasm of oral soft tissues and the most common after fibroma. It generally occurs in the lower lip and its treatment includes excision of cyst and the responsible salivary gland, in order to prevent recurrences. Aims: To evaluate the capability of three different lasers in performing the excision of labial mucocele with two different techniques. Materials and Methods: In the presented cases, excision was performed using two different techniques (circumferential incision technique and mucosal preservation technique and three different laser wavelengths (Er,Cr:YSGG 2780 nm, diode 808 nm, and KTP 532 nm. Results: All the tested lasers, regardless of wavelength, showed many advantages (bloodless surgical field, no postoperative pain, relative speed, and easy execution. The most useful surgical technique depends on clinical features of the lesion. Conclusion: Tested lasers, with both techniques, are helpful in the management of labial mucocele.
Multi-wavelength copper vapour lasers for novel materials processing application
International Nuclear Information System (INIS)
Knowles, M.; Foster-Turner, R.; Kearsley, A.; Evans, J.
1995-01-01
The copper vapour laser (CVL) is a high average power, short pulse laser with a multi-kilohertz pulse repetition rate. The CVL laser lines (511 nm and 578 nm) combined with the good beam quality and high peak power available from these lasers allow it to operate in a unique parameter space. Consequently, it has demonstrated many unique and advantageous machining characteristics. We have also demonstrated efficient conversion of CVL radiation to other wavelengths using non-linear frequency conversion, dye lasers and Ti:AL 2 O 3 . Output powers of up to 4 W at 255 nm have been achieved by frequency doubling. The frequency doubled CVL is inherently narrow linewidth and frequency locked making it a suitable source for UV photolithography. Slope efficiencies in excess of 25 % have been achieved with CVL pumped Ti:Al 2 O 3 and dye lasers. These laser extend the wavelengths options into the red and infrared regions of the spectrum. The near diffraction limited beams from these tunable lasers can be efficiently frequency doubled into the blue and near UV. The wide range of wavelength options from the CVL enable a wide variety of materials processing and material interactions to be explored. A European consortium for Copper Laser Applications in Manufacture and Production (CLAMP) has been set up under the EUREKA scheme to coordinate the commercial and technical expertise currently available in Europe. (author)
Dual-wavelength external cavity laser device for fluorescence suppression in Raman spectroscopy
Zhang, Xuting; Cai, Zhijian; Wu, Jianhong
2017-10-01
Raman spectroscopy has been widely used in the detection of drugs, pesticides, explosives, food additives and environmental pollutants, for its characteristics of fast measurement, easy sample preparation, and molecular structure analyzing capability. However, fluorescence disturbance brings a big trouble to these applications, with strong fluorescence background covering up the weak Raman signals. Recently shifted excitation Raman difference spectroscopy (SERDS) not only can completely remove the fluorescence background, but also can be easily integrated into portable Raman spectrometers. Usually, SERDS uses two lasers with small wavelength gap to excite the sample, then acquires two spectra, and subtracts one to the other to get the difference spectrum, where the fluorescence background will be rejected. So, one key aspects of successfully applying SERDS method is to obtain a dual-wavelength laser source. In this paper, a dual-wavelength laser device design based on the principles of external cavity diode laser (ECDL) is proposed, which is low-cost and compact. In addition, it has good mechanical stability because of no moving parts. These features make it an ideal laser source for SERDS technique. The experiment results showed that the device can emit narrow-spectral-width lasers of two wavelengths, with the gap smaller than 2 nanometers. The laser power corresponding to each wavelength can be up to 100mW.
Multi-wavelength study of PPDs using an OPO tunable pulse laser microscope system
International Nuclear Information System (INIS)
Yoshimura, Koji; Nakamura, Isamu
2012-01-01
We have developed a new pulsed laser microscope system whose wavelength is continuously tunable from 410 nm to 2200 nm by using an optical parametric oscillator (OPO) laser system. The laser spot can be focused to ∼2μm diameter, small enough to measure pixel-by-pixel performance of PPDs (pixelated photon detectors). Using multi-wavelength laser light, we plan to probe PPDs at various depths, thanks to their different penetration lengths in the silicon layer. In this paper, details of the commissioning of the laser microscope system and pilot measurements on a PPD at several wavelengths will be presented.
Multi-wavelength study of PPDs using an OPO tunable pulse laser microscope system
Energy Technology Data Exchange (ETDEWEB)
Yoshimura, Koji, E-mail: koji.yoshimura@kek.jp [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Nakamura, Isamu [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)
2012-12-11
We have developed a new pulsed laser microscope system whose wavelength is continuously tunable from 410 nm to 2200 nm by using an optical parametric oscillator (OPO) laser system. The laser spot can be focused to {approx}2{mu}m diameter, small enough to measure pixel-by-pixel performance of PPDs (pixelated photon detectors). Using multi-wavelength laser light, we plan to probe PPDs at various depths, thanks to their different penetration lengths in the silicon layer. In this paper, details of the commissioning of the laser microscope system and pilot measurements on a PPD at several wavelengths will be presented.
Hybrid integrated single-wavelength laser with silicon micro-ring reflector
Ren, Min; Pu, Jing; Krishnamurthy, Vivek; Xu, Zhengji; Lee, Chee-Wei; Li, Dongdong; Gonzaga, Leonard; Toh, Yeow T.; Tjiptoharsono, Febi; Wang, Qian
2018-02-01
A hybrid integrated single-wavelength laser with silicon micro-ring reflector is demonstrated theoretically and experimentally. It consists of a heterogeneously integrated III-V section for optical gain, an adiabatic taper for light coupling, and a silicon micro-ring reflector for both wavelength selection and light reflection. Heterogeneous integration processes for multiple III-V chips bonded to an 8-inch Si wafer have been developed, which is promising for massive production of hybrid lasers on Si. The III-V layer is introduced on top of a 220-nm thick SOI layer through low-temperature wafer-boning technology. The optical coupling efficiency of >85% between III-V and Si waveguide has been achieved. The silicon micro-ring reflector, as the key element of the hybrid laser, is studied, with its maximized reflectivity of 85.6% demonstrated experimentally. The compact single-wavelength laser enables fully monolithic integration on silicon wafer for optical communication and optical sensing application.
International Nuclear Information System (INIS)
Masuda, Shin; Kanoh, Eiji; Irisawa, Akiyoshi; Niki, Shoji
2009-01-01
We investigated the accuracy limitation of a wavelength meter installed in a vacuum chamber to enable us to develop a highly accurate meter based on a Michelson interferometer in 1550 nm optical communication bands. We found that an error of parts per million order could not be avoided using famous wavelength compensation equations. Chromatic dispersion of the refractive index in air can almost be disregarded when a 1560 nm wavelength produced by a rubidium (Rb) stabilized distributed feedback (DFB) diode laser is used as a reference wavelength. We describe a novel dual-wavelength self-calibration scheme that maintains high accuracy of the wavelength meter. The method uses the fundamental and second-harmonic wavelengths of an Rb-stabilized DFB diode laser. Consequently, a highly accurate Michelson type wavelength meter with an absolute accuracy of 5x10 -8 (10 MHz, 0.08 pm) over a wide wavelength range including optical communication bands was achieved without the need for a vacuum chamber.
Recent advances in long wavelength quantum dot lasers and amplifiers
Nötzel, R.; Bente, E.A.J.M.; Smit, M.K.; Dorren, H.J.S.
2009-01-01
We demonstrate 1.55-µm InAs/InGaAsP/InP (100) quantum dot (QD) shallow and deep etched Fabry-Pérot and ring lasers, micro-ring lasers, mode-locked lasers, Butt-joint integrated lasers, polarization control of gain, and wavelength conversion in QD amplifiers.
Wavelength dependency in high power laser cutting and welding
Havrilla, David; Ziermann, Stephan; Holzer, Marco
2012-03-01
Laser cutting and welding have been around for more than 30 years. Within those three decades there has never been a greater variety of high power laser types and wavelengths to choose from than there is today. There are many considerations when choosing the right laser for any given application - capital investment, cost of ownership, footprint, serviceability, along with a myriad of other commercial & economic considerations. However, one of the most fundamental questions that must be asked and answered is this - "what type of laser is best suited for the application?". Manufacturers and users alike are realizing what, in retrospect, may seem obvious - there is no such thing as a universal laser. In many cases there is one laser type and wavelength that clearly provides the highest quality application results. This paper will examine the application fields of high power, high brightness 10.6 & 1 micron laser welding & cutting and will provide guidelines for selecting the laser that is best suited for the application. Processing speed & edge quality serve as key criteria for cutting. Whereas speed, seam quality & spatter ejection provide the paradigm for welding.
Wavelength tunable ultrafast fiber laser via reflective mirror with taper structure.
Fang, Li; Huang, Chuyun; Liu, Ting; Gogneau, Noelle; Bourhis, Eric; Gierak, Jacques; Oudar, Jean-Louis
2016-12-20
Laser sources with a controllable flexible wavelength have found widespread applications in optical fiber communication, optical sensing, and microscopy. Here, we report a tunable mode-locked fiber laser using a graphene-based saturable absorber and a tapered mirror as an end mirror in the cavity. The phase layer in the mirror is precisely etched by focused ion beam (FIB) milling technology, and the resonant wavelength of the mirror shifts correspond to the different etch depths. By scanning the tapered mirror mechanically, the center wavelength of a mode-locked fiber laser can be continuously tuned from 1562 to 1532 nm, with a pulse width in the sub-ps level and repetition rate of 27 MHz.
Efficient green lasers for high-resolution scanning micro-projector displays
Bhatia, Vikram; Bauco, Anthony S.; Oubei, Hassan M.; Loeber, David A. S.
2010-02-01
Laser-based projectors are gaining increased acceptance in mobile device market due to their low power consumption, superior image quality and small size. The basic configuration of such micro-projectors is a miniature mirror that creates an image by raster scanning the collinear red, blue and green laser beams that are individually modulated on a pixel-bypixel basis. The image resolution of these displays can be limited by the modulation bandwidth of the laser sources, and the modulation speed of the green laser has been one of the key limitations in the development of these displays. We will discuss how this limitation is fundamental to the architecture of many laser designs and then present a green laser configuration which overcomes these difficulties. In this green laser architecture infra-red light from a distributed Bragg-reflector (DBR) laser diode undergoes conversion to green light in a waveguided second harmonic generator (SHG) crystal. The direct doubling in a single pass through the SHG crystal allows the device to operate at the large modulation bandwidth of the DBR laser. We demonstrate that the resultant product has a small footprint (9% electrical-to-optical conversion) and large modulation bandwidth (>100 MHz).
Light Wavelength Correlation on the Effect of Hair Growth
International Nuclear Information System (INIS)
Wan Saffiey Wan Abdullah
2010-01-01
The use of laser light as a bio stimulator at certain wavelength is a new development in laser photonics and become an acceptable tool in medical therapy. It based on low power and low energy laser light. The effect of biological cells behaviour to low power laser light stimulates various studies in many areas such as for medical and cosmetic applications. This paper discusses some results of low power laser light that is used for stimulating the hair growth of skinned mouse by using an optically expanded low power laser light. The study indicates that the red light laser provide a significant growth of mouse hair with exposure duration of two hours daily for 24 consecutive days. Apart from that the green laser light is also used in this study; however result shows no significant influence to the growth of mouse hair in this light wavelength. (author)
Infrared presensitization photography at deuterium fluoride laser wavelengths
International Nuclear Information System (INIS)
Geary, J.M.; Ross, K.; Suter, K.
1989-01-01
Near-field irradiance distributions of a deuterium flouride laser system are obtained using infrared presensitization photography. This represents the shortest wavelength region to employ this technique thus far
Multicolor pattern scan laser for diabetic retinopathy with cataract
Institute of Scientific and Technical Information of China (English)
Takao; Hirano; Yasuhiro; Iesato; Toshinori; Murata
2014-01-01
· AIM: To evaluate the ability of various laser wavelengths in delivering sufficient burns to the retina in eyes with cataract using a new multicolor pattern scan laser with green(532 nm), yellow(577 nm), and red(647 nm)lasers.·METHODS: The relationship between the Emery-Little(EL) degree of cataract severity and the laser wavelength required to deliver adequate burns was investigated in102 diabetic eyes. Treatment time, total number of laser shots, and intra-operative pain were assessed as well.·RESULTS: All EL-1 grade eyes and 50% of EL-2 eyes were successfully treated with the green laser, while 50%of EL-2 eyes, 96% of EL-3 eyes, and 50% of EL-4 eyes required the yellow laser. The red laser was effective in the remaining 4% of EL-3 and 50% of EL-4 eyes.·CONCLUSION: Longer wavelength lasers are more effective in delivering laser burns through cataract when we use a multicolor pattern scan laser system.
Jin, Xiaoxi; Du, Xueyuan; Wang, Xiong; Zhou, Pu; Zhang, Hanwei; Wang, Xiaolin; Liu, Zejin
2016-07-15
We demonstrated a high-power ultralong-wavelength Tm-doped silica fiber laser operating at 2153 nm with the output power exceeding 18 W and the slope efficiency of 25.5%. A random distributed feedback fiber laser with the center wavelength of 1173 nm was employed as pump source of Tm-doped fiber laser for the first time. No amplified spontaneous emissions or parasitic oscillations were observed when the maximum output power reached, which indicates that employing 1173 nm random distributed feedback fiber laser as pump laser is a feasible and promising scheme to achieve high-power emission of long-wavelength Tm-doped fiber laser. The output power of this Tm-doped fiber laser could be further improved by optimizing the length of active fiber, reflectivity of FBGs, increasing optical efficiency of pump laser and using better temperature management. We also compared the operation of 2153 nm Tm-doped fiber lasers pumped with 793 nm laser diodes, and the maximum output powers were limited to ~2 W by strong amplified spontaneous emission and parasitic oscillation in the range of 1900-2000 nm.
Wide and Fast Wavelength-Swept Fiber Laser Based on Dispersion Tuning for Dynamic Sensing
Directory of Open Access Journals (Sweden)
Shinji Yamashita
2009-01-01
Full Text Available We have developed a unique wide and fast wavelength-swept fiber laser for dynamic and accurate fiber sensing. The wavelength tuning is based on the dispersion tuning technique, which simply modulates the loss/gain in the dispersive laser cavity. By using wideband semiconductor optical amplifiers (SOAs, the sweep range could be as wide as ∼180 nm. Since the cavity contains no mechanical components, such as tunable filters, we could achieve very high sweep rate, as high as ∼200 kHz. We have realized the swept lasers at three wavelength bands, 1550 nm, 1300 nm, and 800 nm, using SOAs along with erbium-doped fiber amplifiers (EDFAs, and in two laser configurations, ring and linear ones. We also succeeded in applying the swept laser for a dynamic fiber-Bragg grating (FBG sensor system. In this paper, we review our researches on the wide and fast wavelength-swept fiber lasers.
Laser frequency stabilization using a commercial wavelength meter
Couturier, Luc; Nosske, Ingo; Hu, Fachao; Tan, Canzhu; Qiao, Chang; Jiang, Y. H.; Chen, Peng; Weidemüller, Matthias
2018-04-01
We present the characterization of a laser frequency stabilization scheme using a state-of-the-art wavelength meter based on solid Fizeau interferometers. For a frequency-doubled Ti-sapphire laser operated at 461 nm, an absolute Allan deviation below 10-9 with a standard deviation of 1 MHz over 10 h is achieved. Using this laser for cooling and trapping of strontium atoms, the wavemeter scheme provides excellent stability in single-channel operation. Multi-channel operation with a multimode fiber switch results in fluctuations of the atomic fluorescence correlated to residual frequency excursions of the laser. The wavemeter-based frequency stabilization scheme can be applied to a wide range of atoms and molecules for laser spectroscopy, cooling, and trapping.
Short wavelength laser-plasma interaction experiments in a spherical geometry
International Nuclear Information System (INIS)
Keck, R.L.
1984-01-01
Short wavelength (250 to 500 nm) lasers should provide reduced fast electron preheat and increased laser-pellet coupling efficiency when used as laser fusion drivers. As part of an ongoing effort to study short wavelength laser plasm interaction, six beams of the 24 beam OMEGA Nd-glass laser system have been converted to operation at the third harmonic. This system is capable of providing in excess of 250 Joules of 351 nm light on spherical targets at intensities up to 2 x 10/sup 15/ W/cm/sup 2/. To date, experiments have been performed to study the uniformity of irradiation, laser absorption, fast electron production and preheat, energy transport within the target and underdense plasma instabilities. Both x-ray continuum measurements and Kα line measurements indicate that the absorption is dominated by inverse bremsstrahlung. Electron energy transport has been studied using x-ray burn-through and charge collector measurements. The results show that with 351 nm irradiation ablation pressures of order 100 Mbars are generated at intensities of 10/sup 15/ W/cm/sup 2/
Energy Technology Data Exchange (ETDEWEB)
Susumu, Kato; Eiichi, Takahashi; Tatsuya, Aota; Yuji, Matsumoto; Isao, Okuda; Yoshiro, Owadano [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki (Japan)
2004-07-01
The interaction of intense laser pulses with overdense plasmas has attracted much interest for the fast igniter concept in inertial fusion energy. Hot electron temperatures and electron energy spectra in the course of interaction between intense laser pulse and overdense plasmas are reexamined from a viewpoint of the difference in laser wavelength. The hot electron temperature measured by a particle-in-cell simulation is scaled by I rather than I{lambda}{sup 2} at the interaction with overdense plasmas with fixed ions, where I and {lambda} are the laser intensity and wavelength, respectively. (authors)
Operational characteristics of the OMEGA short-wavelength laser fusion facility
International Nuclear Information System (INIS)
Soures, J.M.; Hutchison, R.; Jacobs, S.; McCrory, R.L.; Peck, R.; Seka, W.
1984-01-01
Twelve beams of the OMEGA, 24 beam direct-drive laser facility have been converted to 351-nm wavelength operation. The performance characteristics of this short-wavelength facility will be discussed. Beam-to-beam energy balance of +-2.3% and on-target energy, at 351-nm, in excess of 70 J per beam have been demonstrated. Long-term performance (>600 shots) of the system has been optimized by appropriate choice of index matching liquid, optical materials and coatings. The application of this system in direct-drive laser fusion experiments will be discussed
Tunable high-power narrow-linewidth green external-cavity GaN diode laser
DEFF Research Database (Denmark)
Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael
2016-01-01
A tunable high-power green external-cavity diode laser is demonstrated. Up to 290 mW output power and a 9.2 nm tuning is achieve. This constitutes the highest output power from a tunable green diode laser system.......A tunable high-power green external-cavity diode laser is demonstrated. Up to 290 mW output power and a 9.2 nm tuning is achieve. This constitutes the highest output power from a tunable green diode laser system....
Discrete multi-wavelength tuning of a continuous wave diode-pumped Nd:GdVO4 laser
Nadimi, Mohammad; Waritanant, Tanant; Major, Arkady
2018-05-01
Discrete multi-wavelength operation of a diode-pumped Nd:GdVO4 laser at four different wavelengths was demonstrated using a single birefringent filter plate. The laser achieved maximum output powers of 5.92 W, 5.66 W, 5.56 W and 3.98 W at 1063.2 nm, 1070.8 nm, 1082.5 nm and 1086.2 nm wavelengths, respectively. To the best of our knowledge, apart from achieving the maximum output powers at ~1071 nm and ~1086 nm and best efficiencies at ~1071 nm, ~1083 nm and ~1086 nm wavelengths for a Nd:GdVO4 laser, this is also the largest number of wavelengths from the 4F3/2 → 4I11/2 transition that was ever obtained in a controlled manner from a single laser setup based on any of the Nd-doped laser crystals.
International Nuclear Information System (INIS)
Khoder, Mulham; Verschaffelt, Guy; Nguimdo, Romain Modeste; Danckaert, Jan; Leijtens, Xaveer; Bolk, Jeroen
2013-01-01
We report on a novel integrated approach to obtain dual wavelength emission from a semiconductor laser based on on-chip filtered optical feedback. Using this approach, we show experiments and numerical simulations of dual wavelength emission of a semiconductor ring laser. The filtered optical feedback is realized on-chip by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifiers are placed in the feedback loop in order to control the feedback strength of each wavelength channel independently. By tuning the current injected into each of the amplifiers, we can effectively cancel the gain difference between the wavelength channels due to fabrication and material dichroism, thus resulting in stable dual wavelength emission. We also explore the accuracy needed in the operational parameters to maintain this dual wavelength emission. (letter)
Direct writing of sub-wavelength ripples on silicon using femtosecond laser at high repetition rate
International Nuclear Information System (INIS)
Xie, Changxin; Li, Xiaohong; Liu, Kaijun; Zhu, Min; Qiu, Rong; Zhou, Qiang
2016-01-01
Graphical abstract: - Highlights: • The NSRs and DSRs are obtained on silicon surface. • With increasing direct writing speed, the NSRs suddenly changes and becomes the DSRs. • We develop a Sipe–Drude interference theory by considering the thermal excitation. - Abstract: The near sub-wavelength and deep sub-wavelength ripples on monocrystalline silicon were formed in air by using linearly polarized and high repetition rate femtosecond laser pulses (f = 76 MHz, λ = 800 nm, τ = 50 fs). The effects of laser pulse energy, direct writing speed and laser polarization on silicon surface morphology are studied. When the laser pulse energy is 2 nJ/pulse and the direct writing speed varies from 10 to 25 mm/s, the near sub-wavelength ripples (NSRs) with orientation perpendicular to the laser polarization are generated. While the direct writing speed reaches 30 mm/s, the direction of the obtained deep sub-wavelength ripples (DSRs) suddenly changes and becomes parallel to the laser polarization, rarely reported so far for femtosecond laser irradiation of silicon. Meanwhile, we extend the Sipe–Drude interference theory by considering the thermal excitation, and numerically calculate the efficacy factor for silicon irradiated by femtosecond laser pulses. The revised Sipe–Drude interference theoretical results show good agreement with the periods and orientations of sub-wavelength ripples.
Dual-wavelength erbium-doped fiber laser with asymmetric fiber Bragg grating Fabry-Perot cavity
Chen, Cong; Xu, Zhi-wei; Wang, Meng; Chen, Hai-yan
2014-11-01
A novel dual-wavelength fiber laser with asymmetric fiber Bragg grating (FBG) Fabry-Perot (FP) cavity is proposed and experimentally demonstrated. A couple of uniform FBGs are used as the cavity mirrors, and the third FBG is used as intracavity wavelength selector by changing its operation temperature. Experimental results show that by adjusting the operation temperature of the intracavity wavelength selector, a tunable dual-wavelength laser emission can be achieved. The results demonstrate the new concept of dual-wavelength lasing with asymmetric FBG FP resonator and its technical feasibility.
Experimental tests of induced spatial incoherence using short laser wavelength
International Nuclear Information System (INIS)
Obenschain, S.P.; Grun, J.; Herbst, M.J.
1986-01-01
The authors have developed a laser beam smoothing technique called induced spatial incoherence (ISI), which can produce the highly uniform focal profiles required for direct-drive laser fusion. Uniform well-controlled focal profiles are required to obtain the highly symmetric pellet implosions needed for high-energy gain. In recent experiments, the authors' tested the effects of ISI on high-power laser-target interaction. With short laser wavelength, the coupling physics dramatically improved over that obtained with an ordinary laser beam
International Nuclear Information System (INIS)
Gochelashvili, K S; Zemskov, M E; Evdokimova, O N; Mikhkel'soo, V T; Prokhorov, A M
1999-01-01
An excimer laser spectrometer was designed and constructed. It consists of a high-vacuum interaction chamber, a short-wavelength (λ = 193 nm) excimer ArF laser used for evaporation, a probe dye laser pumped by an XeCl excimer laser, and a system for recording a laser-induced fluorescence signal. This spectrometer was used to investigate nonthermal mechanisms of photoevaporation of a number of wide-gap dielectrics. (laser applications and other topics in quantum electronics)
Controlling the emission wavelength in group III-V semiconductor laser diodes
Ooi, Boon S.
2016-12-29
Methods are provided for modifying the emission wavelength of a semiconductor quantum well laser diode, e.g. by blue shifting the emission wavelength. The methods can be applied to a variety of semiconductor quantum well laser diodes, e.g. group III-V semiconductor quantum wells. The group III-V semiconductor can include AlSb, AlAs, Aln, AlP, BN, GaSb, GaAs, GaN, GaP, InSb, InAs, InN, and InP, and group III-V ternary semiconductors alloys such as AlxGai.xAs. The methods can results in a blue shifting of about 20 meV to 350 meV, which can be used for example to make group III-V semiconductor quantum well laser diodes with an emission that is orange or yellow. Methods of making semiconductor quantum well laser diodes and semiconductor quantum well laser diodes made therefrom are also provided.
Wavelength selectivity of on-axis surface plasmon laser filters
International Nuclear Information System (INIS)
Harmer, S W; Townsend, P D
2002-01-01
Excitation of surface plasmons on a metal substrate, via the attenuated total reflection method can theoretically offer preferential absorption of light at one particular wavelength, whilst reflecting the nearby spectrum. Normally this 'filtering' action is limited to removal of p-polarized light, and the acceptance angle of such a filtering device is very narrow, which limits practical applications, such as separation of fundamental and laser harmonics. The possibility of avoiding this angular precision is explored by considering the complex permittivity of metal composites. By using a two or more layer structure, as opposed to a single metal substrate, the acceptance angle of the device can be broadened, by a factor of about 15 times. An example is discussed for separation of the fundamental and harmonics from a Nd : YAG laser. Variants of the structure allow the design of an in-line transmission filter for the various wavelengths with sufficient angular tolerance to include focusing lenses. Avoidance of laser ablation of the metal is discussed
Dual-wavelength DFB quantum cascade lasers: sources for multi-species trace gas spectroscopy
Kapsalidis, Filippos; Shahmohammadi, Mehran; Süess, Martin J.; Wolf, Johanna M.; Gini, Emilio; Beck, Mattias; Hundt, Morten; Tuzson, Béla; Emmenegger, Lukas; Faist, Jérôme
2018-06-01
We report on the design, fabrication, and performance of dual-wavelength distributed-feedback (DFB) quantum cascade lasers (QCLs) emitting at several wavelengths in the mid-infrared (mid-IR) spectrum. In this work, two new designs are presented: for the first one, called "Neighbour" DFB, two single-mode DFB QCLs are fabricated next to each other, with minimal lateral distance, to allow efficient beam-coupling into multi-pass gas cells. In addition, the minimal distance allows either laser to be used as an integrated heater for the other, allowing to extend the tuning range of its neighbour without any electrical cross-talk. For the second design, the Vernier effect was used to realize a switchable DFB laser, with two target wavelengths which are distant by about 300 cm^{-1}. These devices are promising laser sources for Tunable Diode Laser Absorption Spectroscopy applications targeting simultaneous detection of multiple gasses, with distant spectral features, in compact and mobile setups.
Advanced excimer laser technologies enable green semiconductor manufacturing
Fukuda, Hitomi; Yoo, Youngsun; Minegishi, Yuji; Hisanaga, Naoto; Enami, Tatsuo
2014-03-01
"Green" has fast become an important and pervasive topic throughout many industries worldwide. Many companies, especially in the manufacturing industries, have taken steps to integrate green initiatives into their high-level corporate strategies. Governments have also been active in implementing various initiatives designed to increase corporate responsibility and accountability towards environmental issues. In the semiconductor manufacturing industry, there are growing concerns over future environmental impact as enormous fabs expand and new generation of equipments become larger and more powerful. To address these concerns, Gigaphoton has implemented various green initiatives for many years under the EcoPhoton™ program. The objective of this program is to drive innovations in technology and services that enable manufacturers to significantly reduce both the financial and environmental "green cost" of laser operations in high-volume manufacturing environment (HVM) - primarily focusing on electricity, gas and heat management costs. One example of such innovation is Gigaphoton's Injection-Lock system, which reduces electricity and gas utilization costs of the laser by up to 50%. Furthermore, to support the industry's transition from 300mm to the next generation 450mm wafers, technologies are being developed to create lasers that offer double the output power from 60W to 120W, but reducing electricity and gas consumption by another 50%. This means that the efficiency of lasers can be improve by up to 4 times in 450mm wafer production environments. Other future innovations include the introduction of totally Heliumfree Excimer lasers that utilize Nitrogen gas as its replacement for optical module purging. This paper discusses these and other innovations by Gigaphoton to enable green manufacturing.
Wavelength and pulse duration tunable ultrafast fiber laser mode-locked with carbon nanotubes
Li, Diao; Jussila, Henri; Wang, Yadong; Hu, Guohua; Albrow-Owen, Tom; C. T. Howe, Richard; Ren, Zhaoyu; Bai, Jintao; Hasan, Tawfique; Sun, Zhipei
2018-01-01
Ultrafast lasers with tunable parameters in wavelength and time domains are the choice of light source for various applications such as spectroscopy and communication. Here, we report a wavelength and pulse-duration tunable mode-locked Erbium doped fiber laser with single wall carbon nanotube-based saturable absorber. An intra-cavity tunable filter is employed to continuously tune the output wavelength for 34 nm (from 1525 nm to 1559 nm) and pulse duration from 545 fs to 6.1 ps, respectively....
A dual-wavelength tunable laser with superimposed fiber Bragg gratings
International Nuclear Information System (INIS)
Álvarez-Tamayo, R I; Durán-Sánchez, M; Pottiez, O; Ibarra-Escamilla, B; Kuzin, E A; Cruz, J L; Andrés, M V
2013-01-01
We report a dual-wavelength tunable fiber laser. The cavity is formed by two superimposed fiber Bragg gratings (FBGs) and a temperature tunable high-birefringence fiber optical loop mirror (FOLM). FBGs with wavelengths of 1548.5 and 1538.5 nm were printed in the same section of a fiber using two different masks. The superimposed FBGs were placed on a mechanical mount that allows stretch or compression of the FBGs. As a result of the FBG strain both lines are shifted simultaneously. Dual-wavelength generation requires a fine adjustment of the cavity loss for both wavelengths. (paper)
Wavelength stabilized high pulse power laser diodes for automotive LiDAR
Knigge, A.; Klehr, A.; Wenzel, H.; Zeghuzi, A.; Fricke, J.; Maaßdorf, A.; Liero, A.; Tränkle, G.
2018-03-01
Diode lasers generating optical pulses with high peak power and lengths in the nanosecond range are key components of systems for free-space communication, metrology, material processing, spectroscopy, and light detection and ranging (LiDAR) as needed for object detection and autonomous driving. Automotive LiDAR systems demand additionally a good beam quality and low wavelength shift with temperature due to the wide operating temperature span. We present here internally wavelength stabilized lasers emitting ns optical pulses from an emission aperture between 30 μm and 100 μm with peak powers of tens of Watts at wavelengths around 905 nm. The vertical structure based on AlGaAs (confinement and cladding layers) and InGaAs (active quantum well) is especially optimized for pulsed operation with respect to the implementation of a surface Bragg grating with a high reflectivity. The fabricated 6 mm long distributed Bragg reflector (DBR) broad area (BA) lasers are electrically driven by an in-house developed high-speed unit generating 3 to 10 ns long nearly rectangular shaped current pulses with amplitudes of up to 250 A. Such lasers emit optical pulses with a peak power of more than 30 W at 95 A pulse current up to a temperature of 85°C with a wavelength shift as low as 65 pm/K and a lateral beam propagation factor less than 10. The influence of the lateral aperture width and the pulse length on the beam quality will be shown. A monolithic integration of 3 DBR BA lasers on a single chip whose emission can be combined into a single beam raises the output power to more than 100 W.
High-precision measurement of the wavelength of a nickel-like silver X-ray laser
International Nuclear Information System (INIS)
Hasegawa, Noboru; Kawachi, Tetsuya; Utsumi, Takayuki
2004-01-01
We conducted high-precision measurements of the wavelength of a 4d 1 S 0 →4p 1 P 1 line of a nickel-like silver X-ray laser. The Lyman series lines of hydrogen-like helium ions emitted from low-density plasmas were used as wavelength references, and the wavelength of the X-ray laser line was determined to be 13.887 nm (±0.002 nm). The experimental results were compared with Multiconfiguration Dirac-Fock calculations and were found to agree with theoretical wavelengths. (author)
Efficiencies of laser dyes for atomic vapor laser isotope separation
International Nuclear Information System (INIS)
Maeda, Mitsuo; Oki, Yuji; Uchiumi, Michihiro; Takao, Takayuki; Igarashi, Kaoru; Shimamoto, Kojiro.
1995-01-01
Efficiencies of 30 laser dyes for the atomic vapor laser isotope separation (AVLIS) are experimentally evaluated with a dye laser pumped by a frequency-doubled Nd:YAG laser. On the other hand, a simulation code is developed to describe the laser action of Rhodamine 6G, and the dependence of the laser efficiency on the pump wavelength is calculated. Following conclusions are obtained by these considerations:space: 1) Pyrromethene 567 showed 16% higher laser efficiency than Rhodamine 6G by 532 nm pumping, and Pyrromethene 556 has an ability to provide better efficiency by green light pumping with a Cu vapor laser; 2) Kiton red 620 and Rhodamine 640, whose efficiencies were almost the same as Rhodamine 6G by 532 nm pumping, will show better efficiencies by two-wavelength pumping with a Cu vapor laser. (author)
International Nuclear Information System (INIS)
Kim, Chan Kyu; In, Jung Hwan; Lee, Seok Hee; Jeong, Sungho
2013-01-01
Laser induced breakdown spectroscopy (LIBS) measurement of thin CuIn x Ga 1−x Se 2 (CIGS) films (1.2–1.9 μm) with varying Ga to In ratios was carried out using the fundamental (1064 nm) and second harmonic (532 nm) wavelength Nd:YAG lasers (τ = 5 ns, spot diameter = 150 μm, top-hat profile) in air. The concentration ratios of Ga to In, x Ga ≡ Ga/(Ga + In), of the CIGS samples ranged from 0.027 to 0.74 for which the band gap varied nearly proportionally to x Ga from 0.96 to 1.42. It was found that the LIBS signal of 1064 nm (1.17 eV) wavelength laser was significantly influenced by x Ga , whereas that of the 532 nm (2.34 eV) laser was consistent for all values of x Ga . The observed dependency of the LIBS signal intensity on the laser wavelength was attributed to the large difference of photon energy of the two wavelengths that changed the absorption of incident laser energy by the film. The 532 nm wavelength was found to be advantageous for multi-shot analysis that enabled depth profile analysis of the thin CIGS films and for improving measurement precision by averaging the multi-shot LIBS spectra. - Highlights: • The ablation characteristics of CIGS solar cell films change drastically with laser wavelength. • The LIBS signal intensity of 1064 nm wavelength laser depends strongly on Ga concentration. • Multi-shot LIBS analysis using a 532 nm laser is more advantageous for accuracy and consistency
Dual-wavelength laser transmission photoscanner for breast cancer detection
International Nuclear Information System (INIS)
Kaneko, M.; He, P.; Tanaka, H.; Takahashi, M.; Takai, M.; Baba, K.; Yamashita, Y.; Ohta, K.
1989-01-01
This paper reports on the prototype of a laser transmission photoscanner (LTPS) constructed and used for the detection of breast cancer and compared with x-ray mammography. LTPS has been improved to enable spectroanalysis and application in breast cancer screening. The new type is introduced. In order to obtain higher sensitivity, the output of lasers was increased in intensity. The signal integration time was increased 10-fold, and the width of the detector area was doubled. The gated operation of the detector enables the good throughput. Simultaneous scanning in the dual wavelengths of 630 and 830 nm makes it possible to differentiate hemoglobin (Hb) and oxyhemoglobin (HbO 2 ) in spectroanalysis by means of Lambert--Beer's law. Clinical application of dual-wavelength LTPS shows good correlation with pathology
Wavelengths of the Ni-like 4d to 4p X-ray laser lines
International Nuclear Information System (INIS)
Utsumi, Takayuki; Sasaki, Akira
2000-01-01
The wavelengths of the Ni-like 4d to 4p X-ray laser lines for elements ranging from Pd(Z=46) to U(Z=92) calculated using the relativistic multi-configuration Dirac-Fock code, i.e. grasp92, are presented. These optimal level calculations agree well with measurements and previous calculations. To obtain accurate lasing wavelengths is important to grasp the energy level structure of the complicated Ni-like ions, and especially for the development of collisionally pumped X-ray lasers. The lasing wavelengths are also essential to identify the lines and when the X-ray laser is utilized for imaging and interferometry. (author)
International Nuclear Information System (INIS)
Li, D.; Chen, B.; Wu, W.J.; Ying, Z.X.
2017-01-01
Highlights: • Laser surgery for port wine stain (PWS) was studied by local non-equilibrium theory. • Wavelength selection in laser surgery under various skin pigmentation was explored. • High pigmented skin prefers to 585 nm rather then 595 nm. • Dual-wavelength laser (585/595 + 1064 nm) has better clinic effect than single one. • Deep buried blood vessels can be damaged by 595/1064 nm dual-wavelength laser. - Abstract: Pulsed dye laser (PDL) in visible band (e.g. 585 or 595 nm) together with cryogen spray cooling has become the golden standard for treatment of vascular malformation such as port wine stain (PWS). However, due to the limited energy penetration depth of the PDL, deeply buried blood vessels are likely to survive from the laser irradiation. Nd:YAG laser in near infrared (1064 nm) has great potential in the laser treatment of PWS due to its deeper penetration depth. In this study, the influence of laser wavelength in treating PWS lesions with various melanin concentrations in epidermis was theoretically investigated by a two-temperature model following the local thermal non-equilibrium theory of porous media. The results showed that deeply buried blood vessels can be coagulated by dual-wavelength laser combing 585 or 595 nm with 1064 nm laser. Furthermore, the therapeutic results by dual-wavelength laser were highly related to the melanin concentration in epidermis. In the light and moderate pigmented skin, the 595/1064 nm dual-wavelength laser showed better treatment effect in treating PWS with deeply-buried blood vessels than of 585/1064 nm dual-wavelength laser. For a high pigmented skin, the 585/1064 nm dual-wavelength laser showed better treatment effect than 595/1064 nm dual-wavelength laser.
Optogalvanic wavelength calibration for laser monitoring of reactive atmospheric species
Webster, C. R.
1982-01-01
Laser-based techniques have been successfully employed for monitoring atmospheric species of importance to stratospheric ozone chemistry or tropospheric air quality control. When spectroscopic methods using tunable lasers are used, a simultaneously recorded reference spectrum is required for wavelength calibration. For stable species this is readily achieved by incorporating into the sensing instrument a reference cell containing the species to be monitored. However, when the species of interest is short-lived, this approach is unsuitable. It is proposed that wavelength calibration for short-lived species may be achieved by generating the species of interest in an electrical or RF discharge and using optogalvanic detection as a simple, sensitive, and reliable means of recording calibration spectra. The wide applicability of this method is emphasized. Ultraviolet, visible, or infrared lasers, either CW or pulsed, may be used in aircraft, balloon, or shuttle experiments for sensing atoms, molecules, radicals, or ions.
Zhu, Xinming; Nur, Abdullahi H.; Misra, Prabhakar
1994-01-01
351 optogalvanic transitions have been observed in the 337 - 598 nm wavelength region using an iron - neon hollow cathode discharge lamp and a pulsed tunable dye laser. 223 of these have been identified as transitions associated with neon energy levels. These optogalvanic transitions have allowed, in conjunction with interference fringes recorded concomitantly with an etalon, the calibration of the dye laser wavelength with 0.3/cm accuracy.
Elsherbiny, Nany; Aied Nassef, O
2015-07-01
The fast and nearly non-destructive criteria of laser induced breakdown spectroscopy (LIBS) technique has been exploited for forensic purposes, specifically, document investigation. The dependence of the optical emission spectra of different black gel ink samples on the excitation laser wavelength, namely the visible wavelength at λ=532 nm and the IR wavelength at λ=1064 nm, was studied. The inks of thirty black gel-ink pens comprising ten brands were analyzed to determine the variation of the chemical composition of ink and to discriminate among them with minimum mass removal and minimum damage to the document's paper. Under the adopted experimental conditions, the ability of the visible LIBS to differentiate among the different ink samples was successful compared to IR LIBS at the same laser pulse energy (~25 mJ/pulse, laser fluence is ~1400J·cm(-2) for visible laser and ~1100J·cm(-2) for IR laser) which could be attributed to the IR absorption effects by the black ink. However, the visible LIBS produces deeper crater with respect to that produced by IR LIBS. Applying IR LIBS with higher pulse energy of ~87mJ (laser fluence is ~4100J·cm(-2)), identification and differentiation of the adopted samples was performed with producing a larger-diameter but superficial crater. The plasma parameters are discussed at the adopted experimental conditions. The results support the potential of LIBS technique using both the visible and IR lasers to be commercially developed for forensic document examination. Copyright © 2015 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.
Towards shorter wavelength x-ray lasers using a high power, short pulse pump laser
International Nuclear Information System (INIS)
Tighe, W.; Krushelnick, K.; Valeo, E.; Suckewer, S.
1991-05-01
A near-terawatt, KrF* laser system, focussable to power densities >10 18 W/cm 2 has been constructed for use as a pump laser in various schemes aimed at the development of x-ray lasing below 5nm. The laser system along with output characteristics such as the pulse duration, the focal spot size, and the percentage of amplified spontaneous emission (ASE) emitted along with the laser pulse will be presented. Schemes intended to lead to shorter wavelength x-ray emission will be described. The resultant requirements on the pump laser characteristics and the target design will be outlined. Results from recent solid target experiments and two-laser experiments, showing the interaction of a high-power, short pulse laser with a preformed plasma, will be presented. 13 refs., 5 figs
Diode-side-pumped 131 W, 1319 nm single-wavelength cw Nd:YAG laser.
Haiyong, Zhu; Ge, Zhang; Chenghui, Huang; Yong, Wei; Lingxiong, Huang; Jing, Chen; Weidong, Chen; Zhenqiang, Chen
2007-01-20
A diode-side-pumped high-power 1319 nm single-wavelength Nd:YAG continuous wave (cw) laser is described. Through reasonable coating design of the cavity mirrors, the 1064 nm strongest line as well as the 1338 nm one have been successfully suppressed. The laser output powers corresponding to four groups of different output couplers operating at 1319 nm single wavelength have been compared. The output coupler with the transmission T=5.3% has the highest output power, and a 131 W cw output power was achieved at the pumping power of 555 W. The optical-optical conversion efficiency is 23.6%, and the slope efficiency is 46%. The output power is higher than the total output power of the dual-wavelength laser operating at 1319 nm and 1338 nm in the experiment.
Wavelength Tunable Flip-Flop Operation of a Modulated Grating Y-branch Laser
DEFF Research Database (Denmark)
An, Yi; Lorences Riesgo, Abel; Peucheret, Christophe
2012-01-01
Wavelength tunable flip-flop operation is experimentally demonstrated in a single modulated grating Y-branch laser for the first time. The control pulses have energies of 0.16-0.34 pJ and the switching time is about 200 ps.......Wavelength tunable flip-flop operation is experimentally demonstrated in a single modulated grating Y-branch laser for the first time. The control pulses have energies of 0.16-0.34 pJ and the switching time is about 200 ps....
Energy Technology Data Exchange (ETDEWEB)
Lutsenko, E V; Voinilovich, A G; Rzheutskii, N V; Pavlovskii, V N; Yablonskii, G P; Sorokin, S V; Gronin, S V; Sedova, I V; Kop' ev, Petr S; Ivanov, Sergei V; Alanzi, M; Hamidalddin, A; Alyamani, A
2013-05-31
The room temperature laser generation in the yellow-green ({lambda} = 558.5-566.7 nm) spectral range has been demonstrated under optical pumping by a pulsed nitrogen laser of Cd(Zn)Se/ZnSe quantum dot heterostructures. The maximum achieved laser wavelength was as high as {lambda} = 566.7 nm at a laser cavity length of 945 {mu}m. High values of both the output pulsed power (up to 50 W) and the external differential quantum efficiency ({approx}60%) were obtained at a cavity length of 435 {mu}m. Both a high quality of the laser heterostructure and a low lasing threshold ({approx}2 kW cm{sup -2}) make it possible to use a pulsed InGaN laser diode as a pump source. A laser microchip converter based on this heterostructure has demonstrated a maximum output pulse power of {approx}90 mW at {lambda} = 560 nm. The microchip converter was placed in a standard TO-18 (5.6 mm in diameter) laser diode package. (semiconductor lasers. physics and technology)
Directory of Open Access Journals (Sweden)
V. B. Neimash
2018-01-01
Full Text Available This work describes tin-induced crystallization of amorphous silicon studied with Raman spectroscopy in thin-film structures Si-Sn-Si irradiated with pulsed laser light. We have found and analyzed dependencies of the nanocrystals’ size and concentration on the laser pulse intensity for 10 ns and 150 μm duration laser pulses at the wavelengths of 535 nm and 1070 nm. Efficient transformation of the amorphous silicon into a crystalline phase during the 10 ns time interval of the acting laser pulse in the 200 nm thickness films of the amorphous silicon was demonstrated. The results were analyzed theoretically by modeling the spatial and temporal distribution of temperature in the amorphous silicon sample within the laser spot location. Simulations confirmed importance of light absorption depth (irradiation wavelength in formation and evolution of the temperature profile that affects the crystallization processes in irradiated structures.
DEFF Research Database (Denmark)
Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael
2012-01-01
knowledge, this is the broadest tuning range of the frequency difference from a dual-wavelength diode laser system. The spectrum, output power, and beam quality of the diode laser system are characterized. The power stability of each wavelength is measured, and the power fluctuations of the two wavelengths......A dual-wavelength high-power semiconductor laser system based on a tapered amplifier with double-Littrow external cavity is demonstrated around 800 nm. The two wavelengths can be tuned individually, and the frequency difference of the two wavelengths is tunable from 0.5 to 10.0 THz. To our...
Analysis of a wavelength selectable cascaded DFB laser based on the transfer matrix method
International Nuclear Information System (INIS)
Xie Hongyun; Chen Liang; Shen Pei; Sun Botao; Wang Renqing; Xiao Ying; You Yunxia; Zhang Wanrong
2010-01-01
A novel cascaded DFB laser, which consists of two serial gratings to provide selectable wavelengths, is presented and analyzed by the transfer matrix method. In this method, efficient facet reflectivity is derived from the transfer matrix built for each serial section and is then used to simulate the performance of the novel cascaded DFB laser through self-consistently solving the gain equation, the coupled wave equation and the current continuity equations. The simulations prove the feasibility of this kind of wavelength selectable laser and a corresponding designed device with two selectable wavelengths of 1.51 μm and 1.53 μm is realized by experiments on InP-based multiple quantum well structure. (semiconductor devices)
Scaling of laser-plasma interactions with laser wavelength and plasma size
International Nuclear Information System (INIS)
Max, C.E.; Campbell, E.M.; Mead, W.C.; Kruer, W.L.; Phillion, D.W.; Turner, R.E.; Lasinski, B.F.; Estabrook, K.G.
1983-01-01
Plasma size is an important parameter in wavelength-scaling experiments because it determines both the threshold and potential gain for a variety of laser-plasma instabilities. Most experiments to date have of necessity produced relatively small plasmas, due to laser energy and pulse-length limitations. We have discussed in detail three recent Livermore experiments which had large enough plasmas that some instability thresholds were exceeded or approached. Our evidence for Raman scatter, filamentation, and the two-plasmon decay instability needs to be confirmed in experiments which measure several instability signatures simultaneously, and which produce more quantitative information about the local density and temperature profiles than we have today
Scaling of laser-plasma interactions with laser wavelength and plasma size
Energy Technology Data Exchange (ETDEWEB)
Max, C.E.; Campbell, E.M.; Mead, W.C.; Kruer, W.L.; Phillion, D.W.; Turner, R.E.; Lasinski, B.F.; Estabrook, K.G.
1983-01-25
Plasma size is an important parameter in wavelength-scaling experiments because it determines both the threshold and potential gain for a variety of laser-plasma instabilities. Most experiments to date have of necessity produced relatively small plasmas, due to laser energy and pulse-length limitations. We have discussed in detail three recent Livermore experiments which had large enough plasmas that some instability thresholds were exceeded or approached. Our evidence for Raman scatter, filamentation, and the two-plasmon decay instability needs to be confirmed in experiments which measure several instability signatures simultaneously, and which produce more quantitative information about the local density and temperature profiles than we have today.
Green high-power tunable external-cavity GaN diode laser at 515 nm
DEFF Research Database (Denmark)
Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael
2016-01-01
A 480 mW green tunable diode laser system is demonstrated for the first time to our knowledge. The laser system is based on a GaN broad-area diode laser and Littrow external-cavity feedback. The green laser system is operated in two modes by switching the polarization direction of the laser beam...... incident on the grating. When the laser beam is p-polarized, an output power of 50 mW with a tunable range of 9.2 nm is achieved. When the laser beam is s-polarized, an output power of 480 mW with a tunable range of 2.1 nm is obtained. This constitutes the highest output power from a tunable green diode...... laser system....
Jung, Seo Jin; Kim, Na Na; Choi, Young Jae; Choi, Ji Yong; Choi, Young-Ung; Heo, Youn Seong; Choi, Cheol Young
2016-10-01
This study investigated the effects of increasing water temperature (22-30 °C) on the physiological stress response and immunity of goldfish, Carassius auratus, and the ability of green light-emitting diode (LED) irradiation or melatonin injections to mitigate this temperature-induced stress. To evaluate the effects of either green-wavelength LED light or melatonin on stress in goldfish, we measured plasma triiodothyronine (T3), thyroxine (T4), and thyroid hormone receptor (TR) mRNA expression; plasma cortisol and glucose; and immunoglobulin M (IgM) and lysozyme mRNA expression. The thyroid hormone activities, TR mRNA expression, and plasma cortisol and glucose were higher in goldfish exposed to high-temperature water, but were lower after exposure to melatonin or green-wavelength LED light. Lysozyme mRNA expression and plasma IgM activity and protein expression were lower after exposure to high water temperatures and higher after melatonin or green-wavelength LED light treatments. Therefore, high water temperature induced stress and decreased immunity; however, green-wavelength LED light and melatonin treatments mitigated the effects of stress and enhanced immunity. The benefits of melatonin decreased with time, whereas those of green-wavelength LED treatment did not.
Laser-assisted decontamination—A wavelength dependent study
Nilaya, J. Padma; Raote, Pallavi; Kumar, Aniruddha; Biswas, Dhruba J.
2008-09-01
We present here the experimental results on cleaning of radioactive dielectric particulates, loosely deposited on stainless steel, by coherent light of 1064 nm wavelength and its three harmonics occurring at 532 nm, 355 nm and 266 nm, derived from an Nd-YAG laser. For the initial few exposures, the decontamination factor has been found to be highest when exposed to 1064 nm radiation. With increasing number of exposures, however, the radiation with reducing wavelength assumes a more important role as a cleaning agent. The observation of almost no cleaning with 1064 nm and much reduced cleaning with its harmonics when the contamination is deposited on a transparent substrate confirms the dominant role played by metal substrate towards expelling the loose particulates from its surface.
Tunable multi-wavelength polymer laser based on a triangular-lattice photonic crystal structure
International Nuclear Information System (INIS)
Huang, Wenbin; Pu, Donglin; Qiao, Wen; Wan, Wenqiang; Liu, Yanhua; Ye, Yan; Wu, Shaolong; Chen, Linsen
2016-01-01
A continuously tunable multi-wavelength polymer laser based on a triangular-lattice photonic crystal cavity is demonstrated. The triangular-lattice resonator was initially fabricated through multiple interference exposure and was then replicated into a low refractive index polymer via UV-nanoimprinting. The blend of a blue-emitting conjugated polymer and a red-emitting one was used as the gain medium. Three periods in the scalene triangular-lattice structure yield stable tri-wavelength laser emission (625.5 nm, 617.4 nm and 614.3 nm) in six different directions. A uniformly aligned liquid crystal (LC) layer was incorporated into the cavity as the top cladding layer. Upon heating, the orientation of LC molecules and thus the effective refractive index of the lasing mode changes which continuously shifts the lasing wavelength. A maximum tuning range of 12.2 nm was observed for the lasing mode at 625.5 nm. This tunable tri-wavelength polymer laser is simple constructed and cost-effective. It may find application in the fields of biosensors and photonic integrated circuits. (paper)
Mode-locked Ti:sapphire laser oscillators pumped by wavelength-multiplexed laser diodes
Sugiyama, Naoto; Tanaka, Hiroki; Kannari, Fumihiko
2018-05-01
We directly pumped a Ti:sapphire laser by combining 478 and 520 nm laser diodes to prevent the effect of absorption loss induced by the pump laser of shorter wavelengths (∼450 nm). We obtain a continuous-wave output power of 660 mW at a total incident pump power of 3.15 W. We demonstrate mode locking using a semiconductor saturable absorber mirror, and 126 fs pulses were obtained at a repetition rate of 192 MHz. At the maximum pump power, the average output power is 315 mW. Shorter mode-locked pulses of 42 and 48 fs were respectively achieved by Kerr-lens mode locking with average output powers of 280 and 360 mW at a repetition rate of 117 MHz.
Power blue and green laser diodes and their applications
Hager, Thomas; Strauß, Uwe; Eichler, Christoph; Vierheilig, Clemens; Tautz, Sönke; Brüderl, Georg; Stojetz, Bernhard; Wurm, Teresa; Avramescu, Adrian; Somers, André; Ristic, Jelena; Gerhard, Sven; Lell, Alfred; Morgott, Stefan; Mehl, Oliver
2013-03-01
InGaN based green laser diodes with output powers up to 50mW are now well established for variety of applications ranging from leveling to special lighting effects and mobile projection of 12lm brightness. In future the highest market potential for visible single mode profile lasers might be laser projection of 20lm. Therefore direct green single-mode laser diodes with higher power are required. We found that self heating was the limiting factor for higher current operation. We present power-current characteristics of improved R and D samples with up to 200mW in cw-operation. An optical output power of 100mW is reached at 215mA, a current level which is suitable for long term operation. Blue InGaN laser diodes are also the ideal source for phosphor based generation of green light sources of high luminance. We present a light engine based on LARP (Laser Activated Remote Phosphor) which can be used in business projectors of several thousand lumens on screen. We discuss the advantages of a laser based systems in comparison with LED light engines. LARP requires highly efficient blue power laser diodes with output power above 1W. Future market penetration of LARP will require lower costs. Therefore we studied new designs for higher powers levels. R and D chips with power-current characteristics up to 4W in continuous wave operation on C-mount at 25°C are presented.
Wavelength switchable high-power diode-side-pumped rod Tm:YAG Laser around 2µm.
Wang, Caili; Du, Shifeng; Niu, Yanxiong; Wang, Zhichao; Zhang, Chao; Bian, Qi; Guo, Chuan; Xu, Jialin; Bo, Yong; Peng, Qinjun; Cui, Dafu; Zhang, Jingyuan; Lei, Wenqiang; Xu, Zuyan
2013-03-25
We report a high-power diode-side-pumped rod Tm:YAG laser operated at either 2.07 or 2.02 µm depending on the transmission of pumped output coupler. The laser yields 115W of continuous-wave output power at 2.07 µm with 5% output coupling, which is the highest output power for all solid-state 2.07 μm cw rod Tm:YAG laser reported so far. With an output coupler of 10% transmission, the center wavelength of the laser is switched to 2.02 μm with an output power of 77.1 W. This is the first observation of high-power wavelength switchable diode-side-pumped rod Tm:YAG laser around 2 µm.
International Nuclear Information System (INIS)
Miller, B.I.; Young, M.G.; Oron, M.; Koren, U.; Kisker, D.
1990-01-01
High quality long-wavelength InGaAsP/InP lasers were grown by atmospheric organometallic vapor phase epitaxy using tertiarybutylarsine (TBA) as a substitute for AsH 3 . Electrical and photoluminescence measurements on InGaAs and InGaAsP showed that TBA-grown material was at least as good as AsH 3 material in terms of suitability for lasers. From two wafers grown by TBA, current thresholds I th as low as 11 mA were obtained for a 2-μm-wide semi-insulating blocking planar buried heterostructure laser lasing near 1.3 μm wavelength. The differential quantum efficiencies η D were as high as 21%/facet with a low internal loss α=21 cm -1 . In addition I th as low as 18 mA and η D as high as 18% have been obtained for multiplequantum well lasers at 1.54 μm wavelength. These results show that TBA might be used to replace AsH 3 without compromising on laser performance
Diode-pumped Alexandrite laser with passive SESAM Q-switching and wavelength tunability
Parali, Ufuk; Sheng, Xin; Minassian, Ara; Tawy, Goronwy; Sathian, Juna; Thomas, Gabrielle M.; Damzen, Michael J.
2018-03-01
We report the first experimental demonstration of a wavelength tunable passively Q-switched red-diode-end pumped Alexandrite laser using a semiconductor saturable absorber mirror (SESAM). We present the results of the study of passive SESAM Q-switching and wavelength-tuning in continuous diode-pumped Alexandrite lasers in both linear cavity and X-cavity configurations. In the linear cavity configuration, pulsed operation up to 27 kHz repetition rate in fundamental TEM00 mode was achieved and maximum average power was 41 mW. The shortest pulse generated was 550 ns (FWHM) and the Q-switched wavelength tuning band spanned was between 740 nm and 755 nm. In the X-cavity configuration, a higher average power up to 73 mW, and obtained with higher pulse energy 6 . 5 μJ at 11.2 kHz repetition rate, in fundamental TEM00 mode with excellent spatial quality M2 < 1 . 1. The Q-switched wavelength tuning band spanned was between 775 nm and 781 nm.
Energy Technology Data Exchange (ETDEWEB)
Kumar Kuntumalla, Mohan; Srikanth, Vadali V. S. S., E-mail: vvsssse@uohyd.ernet.in [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad 500046 (India); Rajamudili, Kuladeep; Rao Desai, Narayana [School of Physics, University of Hyderabad, Hyderabad 500046 (India)
2014-04-21
Deep sub-wavelength (Λ/λ = ∼0.22) periodic features are induced uniformly on a nanodiamond (ND) thin film surface using femtosecond (fs) laser irradiation (pulse duration = ∼110 fs and central wavelength of ∼800 nm). The topography of the surface features is controlled by the laser polarization. Orientation of features is perpendicular to laser polarization. Periodicity (spatial periodicity of < λ/4) of the surface features is less than the laser wavelength. This work gives an experimental proof of polarization controlled surface plasmon-fs laser coupling mechanism prompting the interaction between fs laser and solid matter (here ND thin film) which in turn is resulting in the periodic surface features. Scanning electron microscopy in conjunction with micro Raman scattering, X-ray diffraction, and atomic force microscopy are carried out to extract surface morphology and phase information of the laser irradiated regions. This work demonstrates an easy and efficient surface fabrication technique.
International Nuclear Information System (INIS)
Yeh, C H; Shih, F Y; Wang, C H; Chow, C W; Chi, S
2008-01-01
In this investigation, we propose and investigate a stable and tunable dual-wavelength erbium-doped fiber (EDF) ring laser with self-injected Fabry-Perot laser diode (FP-LD) scheme. By using an FP-LD incorporated with a tunable bandpass filter (TBF) within the gain cavity, the fiber laser can lase at two single-longitudinal-mode (SLM) wavelengths simultaneously due to the self-injected operation. The proposed dual-wavelength laser has a good performance of the output power and optical side-mode suppression ratio (SMSR). The laser also shows a wide tuning range from 1523.08 to 1562.26 nm. Besides, the output stabilities of the fiber laser are also discussed
On-chip microparticle detection and sizing using a dual-wavelength waveguide laser
Bernhardi, Edward; van der Werf, Kees; Hollink, Anton; Worhoff, Kerstin; de Ridder, R.M.; Subramaniam, Vinod; Pollnau, Markus
An integrated intra-laser-cavity microparticle sensor based on a dual-phase-shift, dual-wavelength distributed-feedback channel waveguide laser in ytterbium-doped aluminium oxide is presented. Single micro-particles with diameters ranging between 1 μm and 20 μm are detected.
DEFF Research Database (Denmark)
Gersborg-Hansen, Morten; Balslev, Søren; Mortensen, Niels Asger
2006-01-01
We demonstrate wavelength tuning of a micro-fluidic dye ring laser. Wavelength tunability is obtained by controlling the liquid dye concentration. The device performance is modelled by FEM simulations supporting a ray-tracing view.......We demonstrate wavelength tuning of a micro-fluidic dye ring laser. Wavelength tunability is obtained by controlling the liquid dye concentration. The device performance is modelled by FEM simulations supporting a ray-tracing view....
AlGaN-based laser diodes for the short-wavelength ultraviolet region
International Nuclear Information System (INIS)
Yoshida, Harumasa; Kuwabara, Masakazu; Yamashita, Yoji; Takagi, Yasufumi; Uchiyama, Kazuya; Kan, Hirofumi
2009-01-01
We have demonstrated the room-temperature operation of GaN/AlGaN and indium-free AlGaN multiple-quantum-well (MQW) laser diodes under the pulsed-current mode. We have successfully grown low-dislocation-density AlGaN films with AlN mole fractions of 20 and 30% on sapphire substrates using the hetero-facet-controlled epitaxial lateral overgrowth (hetero-FACELO) method. GaN/AlGaN and AlGaN MQW laser diodes have been fabricated on the low-dislocation-density Al 0.2 Ga 0.8 N and Al 0.3 Ga 0.7 N films, respectively. The GaN/AlGaN MQW laser diodes lased at a peak wavelength ranging between 359.6 and 354.4 nm. A threshold current density of 8 kA cm -2 , an output power as high as 80 mW and a differential external quantum efficiency (DEQE) of 17.4% have been achieved. The AlGaN MQW laser diodes lased at a peak wavelength down to 336.0 nm far beyond the GaN band gap. For the GaN/AlGaN MQW laser diodes, the modal gain coefficient and the optical internal loss are estimated to be 4.7±0.6 cm kA -1 and 10.6±2.7 cm -1 , respectively. We have observed that the characteristic temperature T 0 ranges from 132 to 89 K and DEQE shows an almost stable tendency with increase of temperature. A temperature coefficient of 0.049 nm K -1 is also found for the GaN/AlGaN MQW laser diode. The results for the AlGaN-based laser diodes grown on high-quality AlGaN films presented here will be essential for the future development of laser diodes emitting much shorter wavelengths.
Wavelength prediction of laser incident on amorphous silicon detector by neural network
International Nuclear Information System (INIS)
Esmaeili Sani, V.; Moussavi-Zarandi, A.; Kafaee, M.
2011-01-01
In this paper we present a method based on artificial neural networks (ANN) and the use of only one amorphous semiconductor detector to predict the wavelength of incident laser. Amorphous semiconductors and especially amorphous hydrogenated silicon, a-Si:H, are now widely used in many electronic devices, such as solar cells, many types of position sensitive detectors and X-ray imagers for medical applications. In order to study the electrical properties and detection characteristics of thin films of a-Si:H, n-i-p structures have been simulated by SILVACO software. The basic electronic properties of most of the materials used are known, but device modeling depends on a large number of parameters that are not all well known. In addition, the relationship between the shape of the induced anode current and the wavelength of the incident laser leads to complicated calculations. Soft data-based computational methods can model multidimensional non-linear processes and represent the complex input-output relation between the form of the output signal and the wavelength of incident laser.
Wavelength prediction of laser incident on amorphous silicon detector by neural network
Energy Technology Data Exchange (ETDEWEB)
Esmaeili Sani, V., E-mail: vaheed_esmaeely80@yahoo.com [Amirkabir University of Technology, Faculty of Physics, P.O. Box 4155-4494, Tehran (Iran, Islamic Republic of); Moussavi-Zarandi, A.; Kafaee, M. [Amirkabir University of Technology, Faculty of Physics, P.O. Box 4155-4494, Tehran (Iran, Islamic Republic of)
2011-10-21
In this paper we present a method based on artificial neural networks (ANN) and the use of only one amorphous semiconductor detector to predict the wavelength of incident laser. Amorphous semiconductors and especially amorphous hydrogenated silicon, a-Si:H, are now widely used in many electronic devices, such as solar cells, many types of position sensitive detectors and X-ray imagers for medical applications. In order to study the electrical properties and detection characteristics of thin films of a-Si:H, n-i-p structures have been simulated by SILVACO software. The basic electronic properties of most of the materials used are known, but device modeling depends on a large number of parameters that are not all well known. In addition, the relationship between the shape of the induced anode current and the wavelength of the incident laser leads to complicated calculations. Soft data-based computational methods can model multidimensional non-linear processes and represent the complex input-output relation between the form of the output signal and the wavelength of incident laser.
Liu, He Liang
Wavelength division multiplexing (WDM) optical fibre system is an important enabling technology to fulfill the demands for bandwidth in the modern information age. The main objective of this project is to study novel devices with the potential to enhance the performance of WDM systems. In particular, a novel reflective variable optical attenuator (RVOA) used for dynamic gain equalization (DGE) and fibre lasers based on an entirely new type of erbium-doped fibres with ultrawide tuning range were investigated theoretically and experimentally. We proposed a new type of RVOA device which could be potentially integrated with arrayed waveguide grating (AWG) to reduce the cost of DGE substantially. Initially, fibre-based RVOAs, fabricated with optical fibre components such as fibre coupler and Faraday rotator mirror, were investigated theoretically and experimentally. Larger attenuation range up to 22 dB was realized for fibre coupler-based ROVA with a Faraday rotator mirror and its polarization-dependent loss is about 0.5 dB. Then polymeric waveguide-based RVOAs were investigated theoretically and experimentally. Using an epoxy Novolak resin as core material and an UV-cured resin (Norland's NOA61) as cladding material, a polymeric waveguide RVOA was successfully fabricated. The dynamic 15 dB attenuation range was achieved and the PDL was less than 0.2 dB. The measured insertion loss of the polymeric waveguide RVOA was too large (about 18 dB) and was mainly induced by coupling loss, material loss and poor alignment. In the second part of the study, fibre ring lasers with continuous wavelength tuning over wide wavelength range and fibre ring lasers with discrete wavelength tuning were investigated. Tunable lasers are important devices in WDM systems because they could be employed as reserved sources and therefore avoiding the need to stock large inventory of lasers to cover the ITU-wavelength grid. In this project, erbium ions doped bismuth oxide glass fibres instead of
Studies of multi-wavelength laser-induced damage on KDP crystals in the nanosecond regime
International Nuclear Information System (INIS)
Reyne, Stephane
2011-01-01
This thesis interests in the laser-induced damage mechanisms of KDP and DKDP crystals in the nanosecond regime. KDP is a non-linear material particularly used in the frequency converters of the Laser MegaJoule, which is under construction at the CEA-Cesta in France. For this facility, the KDP laser damage resistance is one of the keystones and is still under investigations to fix this problem. This is why this manuscript presents different studies which highlight the two main aspects of the nanosecond laser-induced damage of KDP frequency converters: the precursor defects and the mechanisms to initiate damage. First, we propose a study based on the analysis of several photos obtained by DIC microscopy of damage initiated by different wavelengths. A comparison with a code coupling the energy deposition and hydrodynamic is also done. Then, we interest in the influence of the defects geometry through a study based on the laser polarization effect on the laser damage resistance. By the comparison with a CEA home-made code, this study particularly underlines the possibility to define a new geometry for the precursor defects. This geometry proposed has the shape of an ellipsoid and is supposed to keep the crystal structure properties. Finally, we enlarge on the physical mechanisms initiating laser damage with pump-pump experiments. These tests consist in combining two radiations of different wavelengths which impacting the crystal simultaneously or are delayed one by the other. We then observe the influence of this wavelengths mixing on the KDP laser damage resistance. In particular, a coupling effect between the wavelengths of the mixture may occur as a function of the fluences combination. Finally, the goal of these specific studies is to accumulate new data in order to improve the understanding in the initiation of the laser damage in KDP and DKDP crystals in the nanosecond regime. In the end, these data will allow us to develop predictive models to simulate the laser
Louyer, Yann; Wallerand, Jean-Pierre; Himbert, Marc; Deneva, Margarita; Nenchev, Marin
2003-09-20
We demonstrate and investigate a peculiar mode of cw Yb3+-doped crystal laser operation when two emissions, at two independently tunable wavelengths, are simultaneously produced. Both emissions are generated from a single pumped volume and take place in either a single beam or spatially separated beams. The laser employs original two-channel cavities that use a passive self-injection-locking (PSIL) control to reduce intracavity loss. The advantages of the application of the PSIL technique and some limitations are shown. The conditions for two-wavelength multimode operation of the cw quasi-three-level diode-pumped Yb3+ lasers and the peculiarity of such an operation are carried out both theoretically and experimentally. The results reported are based on the example of a Yb3+:GGG laser but similar results are also obtained with a Yb3+:YAG laser. The laser operates in the 1023-1033-nm (1030-1040-nm) range with a total output power of 0.4 W. A two-wavelength, single longitudinal mode generation is also obtained.
Krypton red laser photocoagulation of the ocular fundus. 1982.
Yannuzzi, Lawrence A; Shakin, Jeffrey L
2012-02-01
The theoretical rationale, the histopathologic evidence, and the preliminary clinical studies related to krypton red laser (KRL) photocoagulation of the ocular fundus are reviewed. The authors report on their experience with currently available laser systems using this wavelength (647.1 nm) for photocoagulation of retinal vascular proliferative diseases and chorioretinal diseases associated with exudative manifestations. A histopathologic and clinical comparison of argon blue-green laser (ABGL), the pure argon green laser (AGL), and the krypton yellow laser (KYL), with reference to photocoagulation treatment of the ocular fundus is also discussed.
Yamanoi, Kohei; Hori, Tatsuhiro; Minami, Yuki; Empizo, Melvin John F.; Luong, Mui Viet; Shiro, Atsushi; Watanabe, Jun; Iwano, Keisuke; Iwasa, Yuki; Cadatal-Raduban, Marilou; Gabayno, Jacque Lynn; Shimizu, Toshihiko; Sarukura, Nobuhiko; Norimatsu, Takayoshi
2018-01-01
We report the fluorescence spectra of ZrO2 and trivalent Ho-doped ZrO2 ceramics under ultraviolet (UV) excitation at 213, 266, and 355 nm wavelengths. The Ho3+-doped ZrO2 ceramics exhibited varying fluorescence color tones depending on the excitation wavelength used. The different color tones match the fluorescence spectrum characteristics at each excitation wavelength. Our results demonstrate that Ho3+-doped ZrO2 ceramics can discriminate between UV light, specifically the third, fourth, and fifth harmonics of a Nd:YAG laser. It can potentially be used for developing UV laser beam viewers to aid laser alignment.
DEFF Research Database (Denmark)
Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael
2011-01-01
Tunable dual-wavelength operation of a diode laser system based on a tapered diode amplifier with double-Littrow external-cavity feedback is demonstrated around 800nm. The two wavelengths can be tuned individually, and the frequency difference of the two wavelengths is tunable from 0.5 to 5:0 THz......, this is the highest output power from a dual-wavelength diode laser system operating with tunable terahertz frequency difference. © 2011 Optical Society of America....
International Nuclear Information System (INIS)
Detalle, Vincent; Sabsabi, Mohamad; St-Onge, Louis; Hamel, Andre; Heon, Rene
2003-01-01
Laser-induced breakdown spectroscopy (LIBS) is widely dependent on the conditions of its implementation in terms of laser characteristics (wavelength, energy, and pulse duration), focusing conditions, and surrounding gas. In this study two wavelengths, 1.06 and 2.94 μm, obtained with Nd:YAG and Er:YAG lasers, respectively, were used for LIBS analysis of aluminum alloy samples in two conditions of surrounding gas. The influence of the laser wavelength on the laser-produced plasma was studied for the same irradiance by use of air or helium as a buffer gas at atmospheric pressure. We used measurements of light emission to determine the temporally resolved space-averaged electron density and plasma temperature in the laser-induced plasma. We also examined the effect of laser wavelength in two different ambient conditions in terms of spectrochemical analysis by LIBS. The results indicate that the effect of the surrounding gas depends on the laser wavelength and the use of an Er:YAG laser could increase linearity by limiting the leveling in the calibration curve for some elements in aluminum alloys. There is also a significant difference between the plasma induced by the two lasers in terms of electron density and plasma temperature
International Nuclear Information System (INIS)
Ushakov, S N; Lis, Denis A; Subbotin, Kirill A; Romanyuk, V A; Shestakov, A V; Ryabochkina, P A; Shestakova, I A; Zharikov, Evgeny V
2010-01-01
Lasing in Nd:NaLa(MoO 4 ) 2 crystals is obtained without stabilisation of the diode pump wavelength. A dependence of the cw laser power (at a wavelength of 1059 nm) on the pump diode temperature is found within a range of 10-458C. It is shown that the variations in the diode temperature within this region change the lasing efficiency no more than by 30%. In the passive Q-switching regime, the experiments were performed under both pulsed and cw pumping. Upon pulsed pumping, the laser energy was 16 μJ at the output pulse duration of 11 ns. The laser wavelength was 1059 nm, as well as in the case of cw operation. Upon cw pumping with a power of 1.5 W, laser pulses were obtained with an energy of 15 μJ. (lasers)
Soltwisch, Jens; Jaskolla, Thorsten W; Dreisewerd, Klaus
2013-10-01
The success of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) as a widely employed analytical tool in the biomolecular sciences builds strongly on an effective laser-material interaction that is resulting in a soft co-desorption and ionization of matrix and imbedded biomolecules. To obtain a maximized ion yield for the analyte(s) of interest, in general both wavelength and fluence need to be tuned to match the specific optical absorption profile of the used matrix. However, commonly only lasers with fixed emission wavelengths of either 337 or 355 nm are used for MALDI-MS. Here, we employed a wavelength-tunable dye laser and recorded both the neutral material ejection and the MS ion data in a wide wavelength and fluence range between 280 and 377.5 nm. α-Cyano-4-hydroxycinnamic acid (HCCA), 4-chloro-α-cyanocinnamic acid (ClCCA), α-cyano-2,4-difluorocinnamic acid (DiFCCA), and 2,5-dihydroxybenzoic acid (DHB) were investigated as matrices, and several peptides as analytes. Recording of the material ejection was achieved by adopting a photoacoustic approach. Relative ion yields were derived by division of photoacoustic and ion signals. In this way, distinct wavelength/fluence regions can be identified for which maximum ion yields were obtained. For the tested matrices, optimal results were achieved for wavelengths corresponding to areas of high optical absorption of the respective matrix and at fluences about a factor of 2-3 above the matrix- and wavelength-dependent ion detection threshold fluences. The material ejection as probed by the photoacoustic method is excellently fitted by the quasithermal model, while a sigmoidal function allows for an empirical description of the ion signal-fluence relationship.
Alignment control of columnar liquid crystals with wavelength tunable CO2 laser irradiation
International Nuclear Information System (INIS)
Monobe, Hirosato; Awazu, Kunio; Shimizu, Yo
2008-01-01
Infrared-induced alignment change with wavelength tunable CO 2 laser irradiation for columnar liquid crystal domains was investigated for a liquid crystalline triphenylene derivative. A uniformly aligned alignment change of domains was observed when a chopped linearly polarized infrared laser light corresponding to the wavelength of the aromatic C-O-C stretching vibration band (9.65 μm) was irradiated. The results strongly imply that the infrared irradiation is a possible technique for device fabrication by use of columnar mesophase as a liquid crystalline semiconductor
Wavelength comparison for laser induced breakdown spectroscopy caries detection
Amaral, Marcello M.; Raele, Marcus P.; Ana, Patrícia A.; Núñez, Sílvia C.; Zamataro, Claudia B.; Zezell, Denise M.
2018-02-01
Laser Induced Breakdown Spectroscopy (LIBS) is a technique capable to perform elemental analyses of a variety of samples, independent of matter state. Other spectroscopy techniques may require a destructive and time-consuming sample preparation. On the other hand, LIBS is a less destructive technique with no (or considerably less) sample preparation, using a relatively simple experimental setup. LIBS also provides a multielement analysis into one single spectrum acquisition, applying a Nd:YAG short-pulsed laser to ensure the stoichiometry between the sample and the generated plasma. LIBS have been applied on the study of carious lesions using a Nd:YAG into its fundamental emission at 1064 nm. It was shown that ratio of P/Ca and Zn/Ca can be used to monitor the cariogenic process. Another minor elements, e.g. C and Cu, associated with bacteria biofilm were also measured with the Nd:YAG laser. The fundamental wavelength emission (1064 nm) of Nd:YAG is coincident with a hydroxyapatite transmission window and it may affect the result. In order to address this issue a study used the second harmonic of the Nd:YAG laser at 532 nm. It was show that it is also possible perform LIBS on carious lesion using the Nd:YAG at 532 nm. However, there is not a work direct comparing the LIBS at 532 nm and 1064 nm for carious lesion detection. So, the aim of this work was to investigate the influence of laser wavelength on the LIBS performance for carious lesion detection. In both cases the carious lesion was detected with the advantage of no interference with hydroxyapatite at 532 nm.
Inhibited-coupling HC-PCF based beam-delivery-system for high power green industrial lasers
Chafer, M.; Gorse, A.; Beaudou, B.; Lekiefs, Q.; Maurel, M.; Debord, B.; Gérôme, F.; Benabid, F.
2018-02-01
We report on an ultra-low loss Hollow-Core Photonic Crystal Fiber (HC-PCF) beam delivery system (GLO-GreenBDS) for high power ultra-short pulse lasers operating in the green spectral range (including 515 nm and 532 nm). The GLOBDS- Green combines ease-of-use, high laser-coupling efficiency, robustness and industrial compatible cabling. It comprises a pre-aligned laser-injection head, a sheath-cable protected HC-PCF and a modular fiber-output head. It enables fiber-core gas loading and evacuation in a hermetic fashion. A 5 m long GLO-BDS were demonstrated for a green short pulse laser with a transmission coefficient larger than 80%, and a laser output profile close to single-mode (M2 <1.3).
Wavelength switching dynamics of two-colour semiconductor lasers with optical injection and feedback
International Nuclear Information System (INIS)
Osborne, S; Heinricht, P; Brandonisio, N; Amann, A; O’Brien, S
2012-01-01
The wavelength switching dynamics of two-colour semiconductor lasers with optical injection and feedback are presented. These devices incorporate slotted regions etched into the laser ridge waveguide for tailoring the output spectrum. Experimental measurements are presented demonstrating that optical injection in one or both modes of these devices can induce wavelength bistability. Measured switching dynamics with modulated optical injection are shown to be in excellent agreement with numerical simulations based on a simple rate equation model. We also demonstrate experimentally that time-delayed optical feedback can induce wavelength bistability for short external cavity lengths. Numerical simulations indicate that this two-colour optical feedback system can provide fast optical memory functionality based on injected optical pulses without the need for an external holding beam. (paper)
Wavelength-dependent Faraday–Tyndall effect on laser-induced microbubble in gold colloid
International Nuclear Information System (INIS)
Liaw, Jiunn-Woei; Tsai, Shiao-Wen; Lin, Hung-Hsun; Yen, Tzu-Chen; Chen, Bae-Renn
2012-01-01
The cavitation microbubbles in dilute gold colloids of different concentrations (2–10 ppm) induced by a focused nanosecond-pulsed laser beam were measured and characterized at different wavelengths by using the passive and active ultrasound measurements. Three colloids with gold nanoparticles (GNPs) of different sizes (10, 45, and 75 nm) were used for experiment. The results show that the lifespan of the microbubble is reduced as the concentration of GNP increases, particularly at the wavelength of 532 nm, the surface plasmon resonance (SPR) of GNP. In contrast, at the off-resonant wavelength (e.g. 700 nm), the lifespan reduction is relatively small. This wavelength-dependent cavitation is attributed to the Faraday–Tyndall effect, a strong light scattering by GNPs. A slight defocusing of the Gaussian beam in gold colloid was proposed. Hence, the waist of the focused beam increases to reduce the optical breakdown in gold colloid. For simplicity, a linear relation between the incremental waist radius of Gaussian beam and the concentration of GNP was assumed. According to this formulation, the theoretical results are consistent with the experimental ones. In addition, the dynamics of the microbubble in gold colloid measured by the active ultrasound method agree with the Rayleigh–Plesset model. -- Highlights: ► The Faraday–Tyndall effect of gold colloid on laser induced microbubble is studied. ► Faraday–Tyndall effect of gold colloid causes the defocusing of laser beam. ► Lifespan of the microbubble is reduced as the concentration of GNP increases. ► Light scattering of laser beam at the surface plasmon resonance of GNP is the maximum.
Enhanced vacuum laser-impulse coupling by volume absorption at infrared wavelengths
Phipps, C. R., Jr.; Harrison, R. F.; Shimada, T.; York, G. W.; Turner, R. F.
1990-03-01
This paper reports measurements of vacuum laser impulse coupling coefficients as large as 90 dyne/W, obtained with single microsec-duration CO2 laser pulses incident on a volume-absorbing, cellulose-nitrate-based plastic. This result is the largest coupling coefficient yet reported at any wavelength for a simple, planar target in vacuum, and partly results from expenditure of internal chemical energy in this material. Enhanced coupling was also observed in several other target materials that are chemically passive, but absorb light in depth at 10- and 3-micron wavelengths. The physical distinctions are discussed between this important case and that of simple, planar surface absorbers (such as metals) which were studied in the same experimental series, in light of the predictions of a simple theoretical model.
On-chip microparticle detection and sizing using a dual-wavelength waveguide laser
Bernhardi, Edward H.; van der Werf, Kees O; Hollink, Anton J F; Worhoff, Kerstin; De Ridder, Rene M.; Subramaniam, Vinod; Pollnau, Markus
2013-01-01
An integrated intra-laser-cavity microparticle sensor based on a dual-phase-shift, dual-wavelength distributed-feedback channel waveguide laser in Al2O3:Yb3+ is presented. Real-time detection and accurate size measurement of single microparticles with diameters ranging between 1 μm and 20 μm are
International Nuclear Information System (INIS)
Feng, T; Yan, F P; Li, Q; Peng, W J; Tan, S Y; Feng, S C; Wen, X D; Liu, P
2013-01-01
We report the configuration and operation of a wavelength-tunable single frequency and single polarization erbium-doped fiber laser (EDFL) with a stable and high optical signal to noise ratio (OSNR) laser output. A narrow-band fiber Bragg grating (NBFBG), a FBG-based Fabry–Perot (FP) filter, a polarization controller (PC) and an unpumped erbium-doped fiber (EDF) as a saturable absorber (SA) are employed to realize stable single frequency lasing operation. An all-fiber polarizer (AFP) is introduced to suppress mode hopping and ensure the single polarization mode operation. By adjusting the length of the NBFBG using a stress adjustment module (SAM), four stable single frequency and single polarization laser outputs at wavelengths of 1544.946, 1545.038, 1545.118 and 1545.182 nm are obtained. At room temperature, performance with an OSNR of larger than 60 dB, power fluctuation of less than 0.04 dB, wavelength variation of less than 0.01 nm for about 5 h measurement, and degree of polarization (DOP) of close to 100% has been experimentally demonstrated for the fiber laser operating at these four wavelengths. (paper)
International Nuclear Information System (INIS)
Camas, J.; Anzueto, G.; Mendoza, S.; Hernandez, H.; Garcia, C.; Vazquez, R.
2009-01-01
In this work, we present a novel electronic design of a DC source, which automatically controls the temperature of a tunable laser. The temperature change in the laser is carried out by the control of DC that circulates through a cooling stage where the laser is set. The laser can be tuned in a wavelength around 1550 nm. Its application is in Erbium Doped Fiber Amplifier (EDFA) in reflective configuration. (Author)
Optical frequency-domain reflectometry using multiple wavelength-swept elements of a DFB laser array
DiLazaro, Tom; Nehmetallah, Georges
2017-02-01
Coherent optical frequency-domain reflectometry (C-OFDR) is a distance measurement technique with significant sensitivity and detector bandwidth advantages over normal time-of-flight methods. Although several swept-wavelength laser sources exist, many exhibit short coherence lengths, or require precision mechanical tuning components. Semiconductor distributed feedback lasers (DFBs) are advantageous as a mid-to-long range OFDR source because they exhibit a narrow linewidth and can be rapidly tuned simply via injection current. However, the sweep range of an individual DFB is thermally limited. Here, we present a novel high-resolution OFDR system that uses a compact, monolithic 12-element DFB array to create a continuous, gap-free sweep over a wide wavelength range. Wavelength registration is provided by the incorporation of a HCN gas cell and reference interferometer. The wavelength-swept spectra of the 12 DFBs are combined in post-processing to achieve a continuous total wavelength sweep of more than 40 nm (5.4 THz) in the telecommunications C-Band range.
PicoGreen dye as an active medium for plastic lasers
Pradeep, C.; Vallabhan, C. P. G.; Radhakrishnan, P.; Nampoori, V. P. N.
2015-08-01
Deoxyribonucleic acid lipid complex thin films are used as a host material for laser dyes. We tested PicoGreen dye, which is commonly used for the quantification of single and double stranded DNA, for its applicability as lasing medium. PicoGreen dye exhibits enhanced fluorescence on intercalation with DNA. This enormous fluorescence emission is amplified in a planar microcavity to achieve yellow lasing. Here the role of DNA is not only a host medium, but also as a fluorescence dequencher. With the obtained results we have ample reasons to propose PicoGreen dye as a lasing medium, which can lead to the development of DNA based bio-lasers.
International Nuclear Information System (INIS)
Brittelle, Mack S; Simms, Jean M; Sanders, Scott T; Gord, James R; Roy, Sukesh
2016-01-01
We describe a system designed to perform fixed-wavelength absorption spectroscopy of H 2 O vapor in practical combustion devices. The system includes seven wavelength-stabilized distributed feedback (WSDFB) lasers, each with a spectral accuracy of ±1 MHz. An on-board external cavity diode laser (ECDL) that tunes 1320–1365 nm extends the capabilities of the system. Five system operation modes are described. In one mode, a sweep of the ECDL is used to monitor each WSDFB laser wavelength with an accuracy of ±30 MHz. Demonstrations of fixed-wavelength thermometry at 10 kHz bandwidth in near-room-temperature gases are presented; one test reveals a temperature measurement error of ∼0.43%. (paper)
Quantum interference metrology at deep-UV wavelengths using phase-controlled ultrashort laser pulses
Zinkstok, R. Th; Witte, S.; Ubachs, W.; Hogervorst, W.; Eikema, K. S E
2005-01-01
High-resolution metrology at wavelengths shorter than ultraviolet is in general hampered by a limited availability of appropriate laser sources. It is demonstrated that this limitation can be overcome by quantum-interference metrology with frequency up-converted ultrafast laser pulses. The required
Ultra-high brightness wavelength-stabilized kW-class fiber coupled diode laser
Huang, Robin K.; Chann, Bien; Glenn, John D.
2011-03-01
TeraDiode has produced a fiber-coupled direct diode laser with a power level of 1,040 W from a 200 μm core diameter, 0.18 numerical aperture (NA) output fiber at a single center wavelength. This was achieved with a novel beam combining and shaping technique using COTS diode lasers. The fiber-coupled output corresponds to a Beam Parameter Product (BPP) of 18 mm-mrad and is the lowest BPP kW-class direct diode laser yet reported. The laser has been used to demonstrate laser cutting and welding of steel sheet metal up to 6.65 mm thick. Further advances of these ultra-bright lasers are also projected.
Lin, Gong-Ru; Chi, Yu-Chieh; Liao, Yu-Sheng; Kuo, Hao-Chung; Liao, Zhi-Wang; Wang, Hai-Lin; Lin, Gong-Cheng
2012-06-18
By spectrally slicing a single longitudinal-mode from a master weak-resonant-cavity Fabry-Perot laser diode with transient wavelength scanning and tracking functions, the broadened self-injection-locking of a slave weak-resonant-cavity Fabry-Perot laser diode is demonstrated to achieve bi-directional transmission in a 200-GHz array-waveguide-grating channelized dense-wavelength-division-multiplexing passive optical network system. Both the down- and up-stream slave weak-resonant-cavity Fabry-Perot laser diodes are non-return-to-zero modulated below threshold and coherently injection-locked to deliver the pulsed carrier for 25-km bi-directional 2.5 Gbits/s return-to-zero transmission. The master weak-resonant-cavity Fabry-Perot laser diode is gain-switched at near threshold condition and delivers an optical coherent pulse-train with its mode linewidth broadened from 0.2 to 0.8 nm by transient wavelength scanning, which facilitates the broadband injection-locking of the slave weak-resonant-cavity Fabry-Perot laser diodes with a threshold current reducing by 10 mA. Such a transient wavelength scanning induced spectral broadening greatly releases the limitation on wavelength injection-locking range required for the slave weak-resonant-cavity Fabry-Perot laser diode. The theoretical modeling and numerical simulation on the wavelength scanning and tracking effects of the master and slave weak-resonant-cavity Fabry-Perot laser diodes are performed. The receiving power sensitivity for back-to-back transmission at bit-error-rate transmission is less than 2 dB for all 16 channels.
Zhilin, K. M.; Minaev, V. P.; Sokolov, Aleksandr L.
2009-08-01
This work examines laser radiation absorption in water and blood at the wavelengths that are used in endovenous laser treatment (EVLT): 0.81-1.06, 1.32, 1.47, 1.5 and 1.56 μm. It is shown that the best EVLT conditions are ensured by 1.56-μm radiation. Analysis of published data suggests that even higher EVLT efficacy may be achieved at wavelengths of 1.68 and 1.7 μm.
Study on the ablation threshold induced by pulsed lasers at different wavelengths
International Nuclear Information System (INIS)
Torrisi, L.; Borrielli, A.; Margarone, D.
2007-01-01
A study of the effects induced by pulsed laser ablation on different materials as a function of the laser wavelength is presented. In particular the ablation at low laser fluence, of the order of 10 8 -10 10 W/cm 2 with ns pulse width, is investigated experimentally on different metals, semiconductors and polymers. Two theoretical models, explain the experimental results about the fluence threshold value measurements, as depending on the laser wavelength are discussed. The photothermal process is valid for the estimation of the threshold fluence for IR and visible radiation, both inducing thermal heating in metals and semiconductors through the photon-free electron energy transfer. This model is not valid for polymers. The photochemical process is valid for the estimation of the threshold fluence for UV radiation, which photon energy is higher with respect to the chemical binding energy. This radiation induces chemical bond breaking in insulators and scission and cross linking effects can be produced. This last model is not valid for metals and semiconductors
Effects of laser wavelengths and pulse energy ratio on the emission enhancement in dual pulse LIBS
International Nuclear Information System (INIS)
Ahmed, Rizwan; Iqbal, Javed; Baig, M Aslam
2015-01-01
We present new studies on the effects of laser wavelengths, pulse energy ratio and interpulse delay between two laser pulses in the collinear dual pulse configuration of laser-induced breakdown spectroscopy (LIBS) on an iron sample in air using the fundamental (1064 nm) and the second harmonics (532 nm) of Nd:YAG lasers. In the dual pulse LIBS, an optimum value of interpulse delay with an appropriate combination of laser wavelengths, and laser pulse energy ratio, yields a 30 times signal intensity enhancement in the neutral iron lines as compared with single pulse LIBS. A comparison in the spatial variations of electron temperature along the axis of the plume expansion in single and double pulse LIBS has also been studied. (letter)
Isterling, William M; Dally, Bassam B; Alwahabi, Zeyad T; Dubovinsky, Miro; Wright, Daniel
2012-01-01
Narrow laser beams directed from aircraft may at times pass through the exhaust plume of the engines and potentially degrade some of the laser beam characteristics. This paper reports on controlled studies of laser beam deviation arising from propagation through turbulent hot gases, in a well-characterized laboratory burner, with conditions of relevance to aircraft engine exhaust plumes. The impact of the temperature, laser wavelength, and turbulence length scale on the beam deviation has been investigated. It was found that the laser beam displacement increases with the turbulent integral length scale. The effect of temperature on the laser beam angular deviation, σ, using two different laser wavelengths, namely 4.67 μm and 632.8 nm, was recorded. It was found that the beam deviation for both wavelengths may be semiempirically modeled using a single function of the form, σ=a(b+(1/T)(2))(-1), with two parameters only, a and b, where σ is in microradians and T is the temperature in °C. © 2012 Optical Society of America
Energy Technology Data Exchange (ETDEWEB)
Kaplan, Alexander F.H., E-mail: alexander.kaplan@ltu.se
2015-02-15
Highlights: • The absorption distribution of 1 μm wavelength lasers compared to 10 μm CO{sub 2}-lasers across a wavy molten steel surface is calculated, at grazing angle of incidence. • For a wide range of surface waviness parameters the CO{sub 2}-laser shows a much more homogenizing absorption behaviour than 1 μm-lasers. • Although the interaction is very complex and non-linear, it is fundamental and very distinct between CO{sub 2}-lasers and 1 μm-lasers, due to their very different Fresnel-absorption characteristics. • The strong local absorption peaks for 1 μm-lasers can cause very strong local boiling and amplification of surface waves, in good correlation to empirical experimental trends. • Such differences can in turn have strong consequences during laser materials processing like laser keyhole welding, laser drilling or laser remote fusion cutting. - Abstract: For wavy metal melts, across a wide range of their topology parameters, lasers with about 1 μm wavelength experience the highest Fresnel absorption around the shoulders of the waves. Calculations show that this induces a strong peak of the absorbed power density of the laser beam. The high temperature gradients have the potential to cause very local boiling and growth of the valleys. In contrast, for a certain parameter category the small Brewster angle for the CO{sub 2}-laser partially homogenizes the temperatures by elevated absorption at domains of grazing incidence. This has the potential to cause opposite consequences on the process, like wave smoothing.
Harvey, E.; Pochet, M.; Schmidt, J.; Locke, T.; Naderi, N.; Usechak, N. G.
2013-03-01
This work investigates the implementation of all-optical logic gates based on optical injection locking (OIL). All-optical inverting, NOR, and NAND gates are experimentally demonstrated using two distributed feedback (DFB) lasers, a multi-mode Fabry-Perot laser diode, and an optical band-pass filter. The DFB lasers are externally modulated to represent logic inputs into the cavity of the multi-mode Fabry-Perot slave laser. The input DFB (master) lasers' wavelengths are aligned with the longitudinal modes of the Fabry-Perot slave laser and their optical power is used to modulate the injection conditions in the Fabry-Perot slave laser. The optical band-pass filter is used to select a Fabry- Perot mode that is either suppressed or transmitted given the logic state of the injecting master laser signals. When the input signal(s) is (are) in the on state, injection locking, and thus the suppression of the non-injected Fabry-Perot modes, is induced, yielding a dynamic system that can be used to implement photonic logic functions. Additionally, all-optical photonic processing is achieved using the cavity-mode shift produced in the injected slave laser under external optical injection. The inverting logic case can also be used as a wavelength converter — a key component in advanced wavelength-division multiplexing networks. As a result of this experimental investigation, a more comprehensive understanding of the locking parameters involved in injecting multiple lasers into a multi-mode cavity and the logic transition time is achieved. The performance of optical logic computations and wavelength conversion has the potential for ultrafast operation, limited primarily by the photon decay rate in the slave laser.
Single- and dual-wavelength laser pulses induced modification in 10×(Al/Ti)/Si multilayer system
Energy Technology Data Exchange (ETDEWEB)
Salatić, B. [University of Belgrade, Institute of Physics Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Petrović, S., E-mail: spetro@vinca.rs [University of Belgrade, Institute of Nuclear Science-Vinča, POB 522, 11001 Belgrade (Serbia); Peruško, D. [University of Belgrade, Institute of Nuclear Science-Vinča, POB 522, 11001 Belgrade (Serbia); Čekada, M.; Panjan, P. [Jožef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Pantelić, D.; Jelenković, B. [University of Belgrade, Institute of Physics Belgrade, Pregrevica 118, 11080 Belgrade (Serbia)
2016-01-01
Graphical abstract: - Highlights: • Experimental and numerical study of laser-induced ablation and micro-sized crater formation. • Dual-wavelength pulses induce creation of wider and deeper craters due to synergies of two processes. • Sunflower-like structure formed by dual-wavelength pulses at low irradiance. • Numerical model of nanosecond pulsed laser ablation for complex (Al/Ti)/Si system has been developed. - Abstract: The surface morphology of the ablation craters created in the multilayer 10×(Al/Ti)/Si system by nanosecond laser pulses at single- and dual wavelength has been studied experimentally and numerically. A complex multilayer thin film including ten (Al/Ti) bilayers deposited by ion sputtering on Si(1 0 0) substrate to a total thickness of 260 nm were illuminated at different laser irradiance in the range 0.25–3.5 × 10{sup 9} W cm{sup −2}. Single pulse laser irradiation was done at normal incidence in air, with the single wavelength, either at 532 nm or 1064 nm or with both laser light simultaneously in the ratio of 1:10 for energy per pulse between second harmonic and 1064 nm. Most of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the sample surface. The results show an increase in surface roughness, formation of specific nanostructures, appearance of hydrodynamic features and ablation of surface material with crater formation. Applying a small fraction (10%) of the second harmonic in dual-wavelength pulses, a modification of the 10×(Al/Ti)/Si system by a single laser pulse was reflected in the formation of wider and/or deeper craters. Numerical calculations show that the main physical mechanism in ablation process is normal evaporation without phase explosion. The calculated and experimental results agree relatively well for the whole irradiance range, what makes the model applicable to complex Al/Ti multilayer systems.
Kwon, Yong Seok; Ko, Myeong Ock; Jung, Mi Sun; Park, Ik Gon; Kim, Namje; Han, Sang-Pil; Ryu, Han-Cheol; Park, Kyung Hyun; Jeon, Min Yong
2013-01-01
We report a high-speed (∼2 kHz) dynamic multiplexed fiber Bragg grating (FBG) sensor interrogation using a wavelength-swept laser (WSL) with a polygon-scanner-based wavelength filter. The scanning frequency of the WSL is 18 kHz, and the 10 dB scanning bandwidth is more than 90 nm around a center wavelength of 1,540 nm. The output from the WSL is coupled into the multiplexed FBG array, which consists of five FBGs. The reflected Bragg wavelengths of the FBGs are 1,532.02 nm, 1,537.84 nm, 1,543.48 nm, 1,547.98 nm, and 1,553.06 nm, respectively. A dynamic periodic strain ranging from 500 Hz to 2 kHz is applied to one of the multiplexed FBGs, which is fixed on the stage of the piezoelectric transducer stack. Good dynamic performance of the FBGs and recording of their fast Fourier transform spectra have been successfully achieved with a measuring speed of 18 kHz. The signal-to-noise ratio and the bandwidth over the whole frequency span are determined to be more than 30 dB and around 10 Hz, respectively. We successfully obtained a real-time measurement of the abrupt change of the periodic strain. The dynamic FBG sensor interrogation system can be read out with a WSL for high-speed and high-sensitivity real-time measurement. PMID:23899934
International Nuclear Information System (INIS)
Kaplan, A. F. H.
2012-01-01
The modulation of the angle-dependent Fresnel absorptivity across wavy molten steel surfaces during laser materials processing, like drilling, cutting, or welding, has been calculated. The absorptivity is strongly altered by the grazing angle of incidence of the laser beam on the processing front. Owing to its specific Brewster-peak characteristics, the 10.64 μm wavelength CO 2 -laser shows an opposite trend with respect to roughness and angle-of-incidence compared to lasers in the wavelength range of 532-1070 nm. Plateaus or rings of Brewster-peak absorptivity can lead to hot spots on a wavy surface, often in close proximity to cold spots caused by shadow domains.
Diode-pumped orthogonally polarized dual-wavelength Nd3+:LaBO2MoO4 laser
Chen, Y. J.; Gong, X. H.; Lin, Y. F.; Huang, J. H.; Luo, Z. D.; Huang, Y. D.
2013-08-01
Polarized spectroscopic properties related to 1.07 μm laser operation of a 1.8 at.% Nd3+:LaBO2MoO4 crystal grown by the Czochralski method were investigated at room temperature. Using a 2.2-mm-thick, Z-cut Nd3+:LaBO2MoO4 crystal as gain medium, orthogonally polarized dual-wavelength laser at 1,068 and 1,074 nm was first realized in a plano-concave resonator end-pumped by a quasi-continuous-wave 795 nm diode laser. A total output peak power of 1.2 W with slope efficiency of 26 % around 1.07 μm was obtained. The influences of resonator length and pump power on output laser wavelength were also investigated.
Thermal and infrared-diode laser effects on indocyanine-green-treated corneal collagen
Timberlake, George T.; Patmore, Ann; Shallal, Assaad; McHugh, Dominic; Marshall, John
1993-07-01
It has been suggested that laser welds of collagenous tissues form by interdigitation and chemical bonding of thermally 'unraveled' collagen fibrils. We investigated this proposal by attempting to weld highly collagenous, avascular corneal tissue with an infrared (IR) diode laser as follows. First, the temperature at which corneal collagen shrinks and collagen fibrils 'split' into subfibrillary components was determined. Second, since use of a near-IR laser wavelength necessitated addition of an absorbing dye (indocyanine green (ICG) to the cornea, we measured absorption spectra of ICG-treated tissue to ensure that peak ICG absorbance did not change markedly when ICG was present in the cornea. Third, using gel electrophoresis of thermally altered corneal collagen, we searched for covalently crosslinked compounds predicted by the proposed welding mechanism. Finally, we attempted to weld partial thickness corneal incisions infused with ICG. Principal experimental findings were as follows: (1) Human corneal (type I) collagen splits into subfibrillary components at approximately 63 degree(s)C, the same temperature that produces collagen shrinkage. (2) Peak ICG absorption does not change significantly in corneal stroma or with laser heating. (3) No evidence was found for the formation of novel compounds or the loss of proteins as a result of tissue heating. All tissue treated with ICG, however, exhibited a novel 244 kD protein band indicating chemical activity between collagen and corneal stromal components. (4) Laser welding corneal incisions was unsuccessful possibly due to shrinkage of the sides of the incision, lack of incision compression during heating, or a less than optimal combination of ICG concentration and radiant exposure. In summary, these experiments demonstrate the biochemical and morphological complexity of ICG-enhanced IR laser-tissue welding and the need for further investigation of laser welding mechanisms.
Wavelength-tunable prism-coupled external cavity passively mode-locked quantum-dot laser
International Nuclear Information System (INIS)
Wu Yan-Hua; Jian Wu; Jin Peng; Wang Fei-Fei; Hu Fa-Jie; Wei Heng; Wang Zhan-Guo
2015-01-01
A wavelength-tunable mode-locked quantum dot laser using an InAs/GaAs quantum-dot gain medium and a discrete semiconductor saturable absorber mirror is demonstrated. A dispersion prism, which has lower optical loss and less spectral narrowing than a blazed grating, is used for wavelength selection and tuning. A wavelength tuning range of 45.5 nm (from 1137.3 nm to 1182.8 nm) under 140-mA injection current in the passive mode-locked regime is achieved. The maximum average power of 19 mW is obtained at the 1170.3-nm wavelength, corresponding to the single pulse energy of 36.5 pJ. (paper)
Smartphone snapshot mapping of skin chromophores under triple-wavelength laser illumination
Spigulis, Janis; Oshina, Ilze; Berzina, Anna; Bykov, Alexander
2017-09-01
Chromophore distribution maps are useful tools for skin malformation severity assessment and for monitoring of skin recovery after burns, surgeries, and other interactions. The chromophore maps can be obtained by processing several spectral images of skin, e.g., captured by hyperspectral or multispectral cameras during seconds or even minutes. To avoid motion artifacts and simplify the procedure, a single-snapshot technique for mapping melanin, oxyhemoglobin, and deoxyhemoglobin of in-vivo skin by a smartphone under simultaneous three-wavelength (448-532-659 nm) laser illumination is proposed and examined. Three monochromatic spectral images related to the illumination wavelengths were extracted from the smartphone camera RGB image data set with respect to crosstalk between the RGB detection bands. Spectral images were further processed accordingly to Beer's law in a three chromophore approximation. Photon absorption path lengths in skin at the exploited wavelengths were estimated by means of Monte Carlo simulations. The technique was validated clinically on three kinds of skin lesions: nevi, hemangiomas, and seborrheic keratosis. Design of the developed add-on laser illumination system, image-processing details, and the results of clinical measurements are presented and discussed.
Yang, Zi-Qing; Huang, Tzu-Jung; Chang, Yao-Jen; Yeh, Chien-Hung; Chow, Chi-Wai; Chen, Jing-Heng; Chen, Kun-Huang
2018-06-01
In this work, we propose and demonstrate a switchable dual-wavelength erbium-doped fiber (EDF) ring laser with stable single-longitudinal-mode (SLM) output. Here, a dual-ring (DR) structure with an unpumped EDF of 2 m is designed to achieve SLM oscillation. Five fiber Bragg gratings (FBGs) are applied in the laser cavity serving as the reflective element to generate different dual-wavelength outputs. In the measurement, six sets of generated dual-wavelengths with various mode-spacing (Δλ) can be achieved via the five FBGs. Additionally, the stability performance of the proposed EDF DR laser is also demonstrated.
Energy Technology Data Exchange (ETDEWEB)
Patra, Nandini, E-mail: nandinipatra2007@gmail.com [Centre for Material Science and Engineering, Indian Institute of Technology, Indore, Madhya Pradesh, Pin-453441 (India); Akash, K.; Shiva, S.; Gagrani, Rohit; Rao, H. Sai Pranesh; Anirudh, V.R. [Mechatronics and Instrumentation lab, Discipline of Mechanical Engineering, Indian Institute of Technology, Indore, Madhya Pradesh, Pin-453441 (India); Palani, I.A., E-mail: palaniia@iiti.ac.in [Centre for Material Science and Engineering, Indian Institute of Technology, Indore, Madhya Pradesh, Pin-453441 (India); Mechatronics and Instrumentation lab, Discipline of Mechanical Engineering, Indian Institute of Technology, Indore, Madhya Pradesh, Pin-453441 (India); Singh, Vipul [Centre for Material Science and Engineering, Indian Institute of Technology, Indore, Madhya Pradesh, Pin-453441 (India)
2016-03-15
Graphical abstract: - Highlights: • Influence of laser wavelengths (1064 nm, 532 nm and 355 nm) and fluences (40 J/cm{sup 2}, 30 J/cm{sup 2} and 20 J/cm{sup 2}) on generation of underwater laser ablated NiTi nanoparticles. • Particle size range of 140–10 nm was generated at varying laser wavelengths. • The alloy formation of NiTi nanoparticles was confirmed from XRD and TEM analysis where the crystalline peaks of NiTi, Ni{sub 4}Ti{sub 3} and Ni{sub 3}Ti were observed from XRD. • Formation efficiency of NiTi nanoparticles was maximum at 1064 nm wavelength and 40 J/cm{sup 2} fluence. - Abstract: This paper investigates the influence of laser wavelengths and laser fluences on the size and quality of the NiTi nanoparticles, generated through underwater solid state Nd:YAG laser ablation technique. The experiments were performed on Ni55%–Ti45% sheet to synthesize NiTi nano-particles at three different wavelengths (1064 nm, 532 nm and 355 nm) with varying laser fluences ranging from 20 to 40 J/cm{sup 2}. Synthesized NiTi nano-particles were characterized through SEM, DLS, XRD, FT-IR, TEM and UV–vis spectrum. It was observed that, maximum particle size of 140 nm and minimum particle size of 10 nm were generated at varying laser wavelengths. The crystallinity and lattice spacing of NiTi alloy nanoparticles were confirmed from the XRD analysis and TEM images, respectively.
Laser spectroscopy on atoms and ions using short-wavelength radiation
International Nuclear Information System (INIS)
Larsson, Joergen.
1994-05-01
Radiative properties and energy structures in atoms and ions have been investigated using UV/VUV radiation. In order to obtain radiation at short wavelengths, frequency mixing of pulsed laser radiation in crystals and gases has been performed using recently developed frequency-mixing schemes. To allow the study of radiative lifetimes shorter than the pulses from standard Q-switched lasers, different techniques have been used to obtain sufficiently short pulses. The Hanle effect has been employed following pulsed laser excitation for the same purpose. High-resolution spectroscopic techniques have been adapted for use with the broad-band, pulsed laser sources which are readily available in the UV/VUV spectral region. In order to investigate sources of radiation in the XUV and soft X-ray spectral regions, harmonic generation in rare gases has been studied. The generation of coherent radiation by the interaction between laser radiation and relativistic electrons in a synchrotron storage ring has also been investigated. 60 refs
5.5nm wavelength-tunable high-power MOPA diode laser system at 971 nm
Tawfieq, Mahmoud; Müller, André; Fricke, Jörg; Della Casa, Pietro; Ressel, Peter; Ginolas, Arnim; Feise, David; Sumpf, Bernd; Tränkle, Günther
2018-02-01
In this work, a widely tunable hybrid master oscillator power amplifier (MOPA) diode laser with 6.2 W of output power at 971.8 nm will be presented. The MO is a DBR laser, with a micro heater embedded on top of the DBR grating for wavelength tunability. The emitted light of the MO is collimated and coupled into a tapered amplifier using micro cylindrical lenses, all constructed on a compact 25 mm × 25 mm conduction cooled laser package. The MOPA system emits light with a measured spectral width smaller than 17 pm, limited by the spectrometer, and with a beam propagation factor of M2 1/e2 = 1.3 in the slow axis. The emission is thus nearly diffraction limited with 79% of the total power within the central lobe (4.9 W diffraction limited). The electrically controlled micro-heater provides up to 5.5 nm of wavelength tunability, up to a wavelength of 977.3 nm, while maintaining an output power variation of only +/- 0.16 % for the entire tuning range.
A compact O-plus C-band switchable quad-wavelength fiber laser using arrayed waveguide grating
International Nuclear Information System (INIS)
Latif, A A; Zulkifli, M Z; Hassan, N A; Ahmad, H; Harun, S W; Ghani, Z A
2010-01-01
In this paper, a design of a quad-wavelength fiber laser (QWFL) operating in two different regions namely the O-band covering from 1302 nm to1317.4 nm and C-band from 1530.5 nm to 1548.0 nm is presented. Two different ASE sources from semiconductor optical amplifiers (SOAs) are used, one at 1310 nm and the other at1550 nm. By using a 1×24 channels arrayed waveguide grating (AWG) with 100 GHz interchannel spacing, the system is capable of generating 24 different wavelengths in more than 24 ways of quad-wavelength fiber laser with 0.6 nm and 0.8 nm of interval channel for O-band and C-band regions, respectively
Wezel, Felix; Wendt-Nordahl, Gunnar; Huck, Nina; Bach, Thorsten; Weiss, Christel; Michel, Maurice Stephan; Häcker, Axel
2010-04-01
Several diode laser systems were introduced in recent years for the minimal-invasive surgical therapy of benign prostate enlargement. We investigated the ablation capacities, hemostatic properties and extend of tissue necrosis of different diode lasers at wavelengths of 980, 1,318 and 1,470 nm and compared the results to the 120 W GreenLight HPS laser. The laser devices were evaluated in an ex vivo model using isolated porcine kidneys. The weight difference of the porcine kidneys after 10 min of laser vaporization defined the amount of ablated tissue. Blood loss was measured in blood-perfused kidneys following laser vaporization. Histological examination was performed to assess the tissue effects. The side-firing 980 and 1,470 nm diode lasers displayed similar ablative capacities compared to the GreenLight HPS laser (n.s.). The 1,318-nm laser, equipped with a bare-ended fiber, reached a higher ablation rate compared to the other laser devices (each P laser with a bare-ended fiber reached the highest rate compared to the side-firing devices (each P diode lasers showed superior hemostatic properties compared to the GreenLight HPS laser (each P laser), respectively. The diode lasers offered similar ablative capacities and improved hemostatic properties compared to the 120 W GreenLight HPS laser in this experimental ex vivo setting. The higher tissue penetration of the diode lasers compared to the GreenLight HPS laser may explain improved hemostasis.
Directory of Open Access Journals (Sweden)
Jianhu Zhao
2017-04-01
Full Text Available To reduce the size and cost of an integrated infrared (IR and green airborne LiDAR bathymetry (ALB system, and improve the accuracy of the green ALB system, this study proposes a method to accurately determine water surface and water bottom heights using a single green laser corrected by the near water surface penetration (NWSP model. The factors that influence the NWSP of green laser are likewise analyzed. In addition, an NWSP modeling method is proposed to determine the relationship between NWSP and the suspended sediment concentration (SSC of the surface layer, scanning angle of a laser beam and sensor height. The water surface and water bottom height models are deduced by considering NWSP and using only green laser based on the measurement principle of the IR laser and green laser, as well as employing the relationship between NWSP and the time delay of the surface return of the green laser. Lastly, these methods and models are applied to a practical ALB measurement. Standard deviations of 3.0, 5.3, and 1.3 cm are obtained by the NWSP, water-surface height, and water-bottom height models, respectively. Several beneficial conclusions and recommendations are drawn through the experiments and discussions.
Lee, Hyung-Seok; Lee, Hwi Don; Kim, Hyo Jin; Cho, Jae Du; Jeong, Myung Yung; Kim, Chang-Seok
2014-01-01
A linearized wavelength-swept thermo-optic laser chip was applied to demonstrate a fiber Bragg grating (FBG) sensor interrogation system. A broad tuning range of 11.8 nm was periodically obtained from the laser chip for a sweep rate of 16 Hz. To measure the linear time response of the reflection signal from the FBG sensor, a programmed driving signal was directly applied to the wavelength-swept laser chip. The linear wavelength response of the applied strain was clearly extracted with an R-squared value of 0.99994. To test the feasibility of the system for dynamic measurements, the dynamic strain was successfully interrogated with a repetition rate of 0.2 Hz by using this FBG sensor interrogation system. PMID:25177803
Jia, Xiu-jie; Liu, Yan-ge; Si, Li-bin; Guo, Zhan-cheng; Fu, Sheng-gui; Kai, Gui-yun; Dong, Xiao-yi
2008-01-01
A novel multi-wavelength erbium-doped fiber laser operating in C-band is proposed and successfully demonstrated. The wavelength interval between the wavelengths is about 0.22 nm. The 3 dB bandwidth of the laser is about 0.012 nm, and the output power reaches 4.8 mW. By using a high birefringence fiber ring mirror (HiBi-FLM) and a tunable FBG, the laser realizes switchable and tunable characteristic. The mode hopping can be effectively prevented. Moreover, this laser can improve wavelength stability significantly by taking advantage of an un-pumped Er3+-doped fiber at the standing-wave section. The laser can operate in stable narrow-line-width with single-, dual-wavelength, and unstable triple-wavelength output at room temperature.
Deep modulation of second-harmonic light by wavelength detuning of a laser diode
DEFF Research Database (Denmark)
Christensen, Mathias; Hansen, Anders Kragh; Noordegraaf, Danny
2017-01-01
) master oscillator power amplifier (MOPA) laser diode with separate electrical contacts for the MO and the PA. A modulation depth in excess of 97% from 0.1 Hz to 10 kHz is demonstrated. This is done by wavelength tuning of the laser diode using only a 40 mA adjustment of the current through the MO...
Energy Technology Data Exchange (ETDEWEB)
Guo, Bo; Yao, Yong, E-mail: yaoyong@hit.edu.cn; Yang, Yan-Fu; Yuan, Yi-Jun; Wang, Rui-Lai [Department of Electronic and Information Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China); Wang, Shu-Guang; Ren, Zhong-Hua [Department of Materials Science and Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055 (China); Yan, Bo [College of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450052 (China)
2015-02-14
We experimentally demonstrate a multi-wavelength ultrafast erbium-doped fiber laser incorporating a μm-scale topological insulator: Bi{sub 2}Se{sub 3}/Polyvinyl Alcohol film as both an excellent saturable absorber for mode-locking and a high-nonlinear medium to induce a giant third order optical nonlinear effect for mitigating the mode competition of erbium-doped fiber laser and stabilizing the multi-wavelength oscillation. By properly adjusting the pump power and the polarization state, the single-, dual-, triple-, four-wavelength mode-locking pulse could be stably initiated. For the four-wavelength operation, we obtain its pulse width of ∼22 ps and a fundamental repetition rate of 8.83 MHz. The fiber laser exhibits the maximum output power of 9.7 mW with the pulse energy of 1.1 nJ and peak power of 50 W at the pump power of 155 mW. Our study shows that the simple, stable, low-cost multi-wavelength ultrafast fiber laser could be applied in various potential fields, such as optical communication, biomedical research, and radar system.
International Nuclear Information System (INIS)
Georges, Patrick
1989-01-01
We present the study and the realization of a passively mode-locked dye laser producing pulses shorter than 100 femto-seconds (10 -13 s). In a ring cavity with an amplifier medium (Rhodamine 60) and a saturable absorber (DODCI), a sequence of four prisms controls the group velocity dispersion and allows the generation of very short pulses. Then we have studied the production of femtosecond pulses at other wavelengths directly from the femtosecond dye laser. For the first rime, 60 fs pulses at 685 nm and pulses shorter than 50 fs between 775 nm and 800 nm have been produced by passive mode locking. These near infrared pulses have been used to study the absorption saturation kinetics in semiconductors multiple quantum wells GaAs/GaAlAs. We have observed a singular behavior of the laser operating at 685 nm and analyzed the produced pulses in terms of optical solitons. To perform time resolved spectroscopy with shortest pulses, we have studied a pulse compressor and a multipass amplifier to increase the pulses energy. Pulses of 20 fs and 10 micro-joules (peak power: 0.5 GW) have been obtained at low repetition rate (10 Hz) and pulses of 16 fs and 0.6 micro-joules pulses have been generated at high repetition rate (11 kHz) using a copper vapor laser. These pulses have been used to study the absorption saturation kinetics of an organic dye (the Malachite Green). (author) [fr
High Power OPO Laser and wavelength-controlled system for 1.6μm CO2-DIAL
Abo, M.; Nagasawa, C.; Shibata, Y.
2009-12-01
Unlike the existing 2.0μm CO2-DIAL, a high-energy pulse laser operating in the 1.6μm absorption band of CO2 has not been realized. Quasi phase matching (QPM) devices have high conversion efficiency and high beam quality due to their higher nonlinear optical coefficient. We adapt the PPMgLT crystal as the QPM device. The PPMgLT crystal had 3mm × 3mm apertures, and the periodically poled period was 30.9 μm, with the duty ratio close to the ideal value of 0.5. The beam quality of the pumping laser was exceed M2 ≥1.2. The repetition rate was 400 Hz and the energy was 35 mJ. The pumping laser pulse was injection-seeded by the continuous-wave (CW) fiber laser, which had a narrow spectrum. The pulse pumped the PPMgLT crystal in the ring cavity with a single pass through the dielectric mirror. The PPMgLT crystal was mounted on a copper holder, and the temperature was maintained at 40 °C using a Peltier module. The holder’s temperature was stabilized to within 0.01 °C when the copper holder was covered with a plastic case. The OPO ring cavity was a singly resonant oscillator optimized for the signal wave. Single-frequency oscillation of the PPMgLT OPO was achieved by injection seeding, as described in the following. The injection seeder was a DFB laser having a power of 30mW with a 1MHz oscillation spectrum. Their oscillation wavelength was coarse tuned by temperature and fine tuned by adjusting injection currents. The partial power of the online wavelength was split in the wavelength control unit. We locked the DFB laser as an injection seeder of the online wavelength onto the line center by referencing the fiber coupled multipath gas cell (path length 800mm) containing pure CO2 at a pressure of 700 Torr. Stabilization was estimated to within 1.8MHz rms of the line center of the CO2 absorption line by monitoring the feedback signal of a wavelength-controlled unit. Injection seeding of the PPMgLT OPO was performed by matching the cavity length to the seeder
International Nuclear Information System (INIS)
Feng, Ting; Yan, Fengping; Peng, Wanjing; Liu, Shuo; Tan, Siyu; Liang, Xiao; Wen, Xiaodong
2014-01-01
A high stability wavelength-tunable narrow-linewidth and single-polarization erbium-doped fiber laser using a compound-cavity structure is proposed and demonstrated experimentally. The compound-cavity is composed of a main-linear-cavity and a subring-cavity. Using a pump power of 150 mW, the optical signal to noise ratio of the laser output is as high as ∼67 dB; the wavelength and output power fluctuation are 0.7 pm and 0.07 dBm respectively in an experimental period of 1 h; the linewidth of the laser output is as narrow as 650 Hz; the degree of polarization of the laser output is stable at a value of 100.8% in 15 min and the polarization extinction ratio is as high as 30.57 dB; the wavelength-tunable range is as wide as ∼8.1 nm. The proposed fiber laser can be used in areas where high stability, narrow-linewidth, single-polarization and wide wavelength-tunable range are needed. (letter)
Process Studies on Laser Welding of Copper with Brilliant Green and Infrared Lasers
Engler, Sebastian; Ramsayer, Reiner; Poprawe, Reinhart
2011-01-01
Copper materials are classified as difficult to weld with state-of-the-art lasers. High thermal conductivity in combination with low absorption at room temperature require high intensities for reaching a deep penetration welding process. The low absorption also causes high sensitivity to variations in surface conditions. Green laser radiation shows a considerable higher absorption at room temperature. This reduces the threshold intensity for deep penetration welding significantly. The influen...
Litscher, Daniela; Wang, Junying; Li, Guangzong; Bosch, Peggy; Wang, Lu
2018-01-01
Background: One of the most commonly used auricular acupuncture points selected for different pain treatment regimens is Shenmen. This point on the ear has been recognized as having a wide number of applications, as found by scientific investigation. Methods: Within this crossover study, the ear acupoint Shenmen was stimulated with two different kinds of laser (green, 532 nm and yellow, 589 nm) in 22 healthy volunteers (13 female, 9 male; mean age ± SD = 25.3 ± 4.1 years; range 21–36 years). Both green and yellow lasers were used for 15 min in the same volunteers in two different sessions. Results: The most prominent finding was that systolic blood pressure decreased significantly (p = 0.048) after yellow laser stimulation. Heart rate also decreased significantly (p laser acupuncture. However, a comparison with other publications was impossible because this is the first study using green and yellow laser stimulation on the ear. PMID:29543742
International Nuclear Information System (INIS)
Anzueto-Sánchez, G; Martínez-Rios, A
2014-01-01
A stable multiwavelength all-fiber erbium-doped fiber ring laser (EDFRL) based on a broadband long-period fiber grating (LPFG) inscribed in a fiber taper transition is presented. The LPFG’s characteristics were engineered to provide a higher loss at the natural lasing wavelength of the laser cavity. The LPFG inscribed on a taper transition provided a depth greater than 25 dB, and posterior chemical etching provided a broad notch band to inhibit laser generation on the long-wavelength side of the EDF gain. Up to four simultaneous laser wavelengths are generated in the range of 1530–1535 nm. (paper)
Highly efficient dual-wavelength mid-infrared CW Laser in diode end-pumped Er:SrF2 single crystals
Ma, Weiwei; Qian, Xiaobo; Wang, Jingya; Liu, Jingjing; Fan, Xiuwei; Liu, Jie; Su, Liangbi; Xu, Jun
2016-11-01
The spectral properties and laser performance of Er:SrF2 single crystals were investigated and compared with Er:CaF2. Er:SrF2 crystals have larger absorption cross-sections at the pumping wavelength, larger mid-infrared stimulated emission cross-sections and much longer fluorescence lifetimes of the upper laser level (Er3+:4I11/2 level) than those of Er:CaF2 crystals. Dual-wavelength continuous-wave (CW) lasers around 2.8 μm were demonstrated in both 4at.% and 10at.% Er:SrF2 single crystals under 972 nm laser diode (LD) end pumping. The laser wavelengths are 2789.3 nm and 2791.8 nm in the former, and 2786.4 nm and 2790.7 nm in the latter, respectively. The best laser performance has been demonstrated in lightly doped 4at.% Er:SrF2 with a low threshold of 0.100 W, a high slope efficiency of 22.0%, an maximum output power of 0.483 W.
New long-wavelength Nd:YAG laser at 1.44 micron: effect on brain.
Martiniuk, R; Bauer, J A; McKean, J D; Tulip, J; Mielke, B W
1989-02-01
A wavelength-shifted Nd:YAG laser, tuned to coincide with the infrared absorption peak of water at 1.44 microns, was used to make lesions in normal rabbit brain. A total of 48 lesions were made with power up to 20 W, with energy up to 40 joules, and with two different spot sizes. These lesions were compared to lesions made with 1.06 microns radiation from an Nd:YAG laser under identical operating conditions. Measurements of blood-brain barrier damage and width, depth, and volume of tissue affected were obtained 30 minutes after placement of the lesions. It was found that 1.44-microns lesions produced photoevaporative tissue loss at the highest intensities used. The layer of coagulated tissue remaining after photovaporization had a mean thickness of 0.6 mm irrespective of the volume of tissue removed. There was no photovaporization in the 1.06-microns lesions. In addition, the amount of peripheral edema per unit volume of tissue coagulated was approximately half at the 1.44-microns wavelength. These findings suggest that the 1.44-microns Nd:YAG laser may be a useful surgical instrument since it combines the photoevaporative effect of the CO2 laser while maintaining the advantages of the conventional Nd:YAG laser (quartz fiber delivery and effective hemostasis).
The Effects of Slippage and Diffraction in Long-Wavelength Operation of a Free-Electron Laser
Zhulin, V. I.; Haselhoff, E. H.; van Amersfoort, P. W.
1995-01-01
The Free-Electron Laser user facility FELIX produces picosecond optical pulses in the wavelength range of 5-110 mu m. The proposed installation of a new undulator with a larger magnetic period would allow extension towards considerably longer wavelengths. This would result in the production of
Progress in metal-insulator-metal waveguide lasers at near-infrared wavelengths
Marell, M.J.H.; Hill, M.T.
2009-01-01
Strong light con¯nement can be achieved in metallic cavities which can con¯ne light to volumes with dimensions considerably smaller than the wavelength of light. It was commonly believed, however, that the high losses in metals are prohibitive for laser peration in metallic nano-cavities. Recently
Hole transport in c-plane InGaN-based green laser diodes
Energy Technology Data Exchange (ETDEWEB)
Cheng, Yang; Liu, Jianping, E-mail: jpliu2010@sinano.ac.cn; Tian, Aiqin; Zhang, Feng; Feng, Meixin; Hu, Weiwei; Zhang, Shuming; Ikeda, Masao; Li, Deyao; Zhang, Liqun; Yang, Hui [Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); School of Nano Technology and Nano Bionics, University of Science and Technology of China, Suzhou 215123 (China)
2016-08-29
Hole transport in c-plane InGaN-based green laser diodes (LDs) has been investigated by both simulations and experiments. It is found that holes can overflow from the green double quantum wells (DQWs) at high current density, which reduces carrier injection efficiency of c-plane InGaN-based green LDs. A heavily silicon-doped layer right below the green DQWs can effectively suppress hole overflow from the green DQWs.
GaAsSb/InGaAs type-II quantum wells for long-wavelength lasers on GaAs substrates
International Nuclear Information System (INIS)
Klem, J. F.; Blum, O.; Kurtz, S. R.; Fritz, I. J.; Choquette, K. D.
2000-01-01
We have investigated the properties of GaAsSb/InGaAs type-II bilayer quantum-well structures grown by molecular-beam epitaxy for use in long-wavelength lasers on GaAs substrates. Structures with layer strains and thicknesses designed to be thermodynamically stable against dislocation formation exhibit room-temperature photoluminescence at wavelengths as long as 1.43 μm. The photoluminescence emission wavelength is significantly affected by growth temperature and the sequence of layer growth (InGaAs/GaAsSb versus GaAsSb/InGaAs), suggesting that Sb and/or In segregation results in nonideal interfaces under certain growth conditions. At low-injection currents, double-heterostructure lasers with GaAsSb/InGaAs bilayer quantum-well active regions display electroluminescence at wavelengths comparable to those obtained in photoluminescence, but at higher currents the electroluminescence shifts to shorter wavelengths. Lasers have been obtained with threshold current densities of 120 A/cm2 at 1.17 μm, and 2.1 kA/cm2 at 1.21 μm. (c) 2000 American Vacuum Society
Wavelength-tunable thulium-doped fiber laser by employing a self-made Fabry-Perot filter
Wang, Y. P.; Ju, Y. L.; Wu, C. T.; Liu, W.; Yang, C.
2017-06-01
In this demonstration, we proposed a novel wavelength-tunable thulium-doped fiber laser (TDFL) with a self-made Fabry-Perot (F-P) filter. When the F-P filter was not inserted, the maximum output power of 11.1 W was achieved when the pump power was 70.2 W. The corresponding optical-to-optical conversion efficiency was 15.8% and the slope efficiency was 22.1%. When the F-P filter was inserted, the output wavelength could be tuned from 1952.9 to 1934.9 nm with the change of cavity length of F-P filter which was fixed on a piezoelectric ceramic transducer (PZT) controlled by the voltage applied to it. The full width at half maximum (FWHM) was no more than 0.19 nm. Furthermore, the wavelength fluctuations of the tunable fiber laser were kept within ±0.2 nm.
A wavelength-tunable fiber laser using a novel filter based on a compound interference effect
Zou, Hui; Lou, Shuqin; Su, Wei; Han, Bolin; Shen, Xiao
2015-01-01
A wavelength-tunable erbium-doped fiber laser is proposed and experimentally demonstrated by using a novel filter which is formed from a 2 × 2 3 dB multimode coupler incorporating a segment of polarization maintaining fiber (PMF). By using the filter with 2.1 m lengths of PMF in a ring fiber laser, a stable single wavelength lasing is obtained experimentally. Its 3 dB bandwidth is less than 0.0147 nm and the side mode suppression ratio (SMSR) is higher than 58.91 dB. Experimental results demonstrate that mode competition can be effectively suppressed and the SMSR can be improved due to the compound interference effect aroused by the novel filter. Meanwhile the stability of the output lasing can be enhanced. By appropriately adjusting the polarization controllers (PCs), the output lasing wavelength can be tuned from 1563.51 to 1568.21 nm. This fiber laser has the advantage of a simple structure and stable operation at room temperature.
Huang, Haizhou; Huang, Jianhong; Liu, Huagang; Li, Jinhui; Lin, Zixiong; Ge, Yan; Dai, Shutao; Deng, Jing; Lin, Wenxiong
2018-03-05
We demonstrate an enhancement mechanism and thermal model for intra-cavity pumped lasers, where resonance enhancement in intra-cavity pumped Ho laser was achieved by manipulating the wavelength-drift nature of the Tm laser for the first time. Optical conversion efficiency of 37.5% from an absorbed 785 nm diode laser to a Ho laser was obtained with a maximum output power of 7.51 W at 2122 nm, which is comparable to the conversion efficiency in 1.9 μm LD pumped Ho lasers. Meanwhile, more severe thermal effects in the Ho-doped gain medium than the Tm-doped one at high power operation were verified based on the built thermal model. This work benefits the design or evaluation of intra-cavity pumped lasers, and the resonance enhancement originated from the difference in reabsorption loss between stark levels at the lasing manifolds of quasi-three-level rare-earth ions has great interest to improve the existing intra-cavity pumped lasers or explore novel lasers.
All-fiber femtosecond Cherenkov laser at visible wavelengths
DEFF Research Database (Denmark)
Liu, Xiaomin; Lægsgaard, Jesper; Møller, Uffe Visbech
2013-01-01
-matching condition [1]. The resonant ultrafast wave conversion via the fiber-optic CR mechanism is instrumental for applications in biophotonics such as bio-imaging and microscopy [2]. In this work, we demonstrate a highly-stable all-fiber, fully monolithic CR system based on an Yb-fiber femtosecond laser, producing...... to be as low as -103 dBc/Hz. This is 2 orders of magnitudes lower noise as compared to spectrally-sliced supercontinuum, which is the current standard of ultrafast fiber-optic generation at visible wavelength. The layout of the laser system is shown in Fig. 1(a). The system consists of two parts: an all-fiber......Fiber-optic Cherenkov radiation (CR), also known as dispersive wave generation or non-solitonic radiation, is produced in small-core photonic crystal fibers (PCF) when a soliton perturbed by fiber higher-order dispersion co-propagates with a dispersive wave fulfilling a certain phase...
Ahmad, H.; Jasim, A. A.
2017-07-01
A compact coupled microfiber Mach-Zehnder interferometer (CM-MZI) is proposed and experimentally demonstrated for C-band region multi-wavelength tuning and switching in a fiber laser. The CM-MZI is fabricated using a 9 μm single tapered silica optical microfiber fabricated by flame-drawing technique and exploits multi-mode interference to produce spatial mode beating and suppress mode competition of the homogeneous gain medium. The output wavelength spacing is immune to changes in the external environment, but can be changed from 1.5 nm to 1.4 nm by slightly modifying the path-length difference of the CM-MZI. The proposed laser is capable of generating single, dual, triple, quintuple, and sextuple stabilize wavelengths outputs over a range of more than 32 nm using polarization rotation (PR) and macro-bending. The lasers having a 3 dB line-width of less than ∼30 pm and peak-to-floor of about 55 dB at a pump power of 38 mW.
Lin, Hong; Wang, Xinming; Liang, Kun
2010-10-01
For monitoring and forecasting of the ocean red tide in real time, a marine environment monitoring technology based on the double-wavelength airborne lidar system is proposed. An airborne lidar is father more efficient than the traditional measure technology by the boat. At the same time, this technology can detect multi-parameter about the ocean red tide by using the double-wavelength lidar.It not only can use the infrared laser to detect the scattering signal under the water and gain the information about the red tise's density and size, but also can use the blue-green laser to detect the Brillouin scattering signal and deduce the temperature and salinity of the seawater.The red tide's density detecting model is firstly established by introducing the concept about the red tide scattering coefficient based on the Mie scattering theory. From the Brillouin scattering theory, the relationship about the blue-green laser's Brillouin scattering frequency shift value and power value with the seawater temperature and salinity is found. Then, the detecting mode1 of the saewater temperature and salinity can be established. The value of the red tide infrared scattering signal is evaluated by the simulation, and therefore the red tide particles' density can be known. At the same time, the blue-green laser's Brillouin scattering frequency shift value and power value are evaluated by simulating, and the temperature and salinity of the seawater can be known. Baed on the multi-parameters, the ocean red tide's growth can be monitored and forecasted.
Yin, Bin; Feng, Suchun; Liu, Zhibo; Bai, Yunlong; Jian, Shuisheng
2014-09-22
A tunable and switchable dual-wavelength single polarization narrow linewidth single-longitudinal-mode (SLM) erbium-doped fiber (EDF) ring laser based on polarization-maintaining chirped moiré fiber Bragg grating (PM-CMFBG) filter is proposed and demonstrated. For the first time as we know, the CMFBG inscribed on the PM fiber is applied for the wavelength-tunable and-switchable dual-wavelength laser. The PM-CMFBG filter with ultra-narrow transmission band (0.1 pm) and a uniform polarization-maintaining fiber Bragg grating (PM-FBG) are used to select the laser longitudinal mode. The stable single polarization SLM operation is guaranteed by the PM-CMFBG filter and polarization controller. A tuning range of about 0.25 nm with about 0.075 nm step is achieved by stretching the uniform PM-FBG. Meanwhile, the linewidth of the fiber laser for each wavelength is approximate 6.5 and 7.1 kHz with a 20 dB linewidth, which indicates the laser linewidth is approximate 325 Hz and 355 Hz FWHM.
A multi-wavelength (u.v. to visible) laser system for early detection of oral cancer
Najda, S. P.; Perlin, P.; Leszczyński, M.; Slight, T. J.; Meredith, W.; Schemmann, M.; Moseley, H.; Woods, J. A.; Valentine, R.; Kalra, S.; Mossey, P.; Theaker, E.; Macluskey, M.; Mimnagh, G.; Mimnagh, W.
2015-03-01
A multi-wavelength (360nm - 440nm), real-time Photonic Cancer Detector (PCD) optical system based on GaN semiconductor laser technology is outlined. A proof of concept using blue laser technology for early detection of cancer has already been tested and proven for esophageal cancer. This concept is expanded to consider a wider range of wavelengths and the PCD will initially be used for early diagnosis of oral cancers. The PCD creates an image of the oral cavity (broad field white light detection) and maps within the oral cavity any suspicious lesions with high sensitivity using a narrow field tunable detector.
4.5 μm wavelength vertical external cavity surface emitting laser operating above room temperature
Rahim, M.; Khiar, A.; Felder, F.; Fill, M.; Zogg, H.
2009-05-01
A midinfrared vertical external cavity surface emitting laser with 4.5 μm emission wavelength and operating above room temperature has been realized. The active part consists of a single 850 nm thick epitaxial PbSe gain layer. It is followed by a 2 1/2 pair Pb1-yEuyTe/BaF2 Bragg mirror. No microstructural processing is needed. Excitation is done optically with a 1.5 μm wavelength laser. The device operates up to 45 °C with 100 ns pulses and delivers 6 mW output power at 27 °C heat-sink temperature.
Hu, Guoqing; Pan, Yingling; Zhao, Xin; Yin, Siyao; Zhang, Meng; Zheng, Zheng
2017-12-01
The evolution from asynchronous to synchronous dual-wavelength pulse generation in a passively mode-locked fiber laser is experimentally investigated by tailoring the intracavity dispersion. Through tuning the intracavity-loss-dependent gain profile and the birefringence-induced filter effect, asynchronous dual-wavelength soliton pulses can be generated until the intracavity anomalous dispersion is reduced to ∼8 fs/nm. The transition from asynchronous to synchronous pulse generation is then observed at an elevated pump power in the presence of residual anomalous dispersion, and it is shown that pulses are temporally synchronized at the mode-locker in the cavity. Spectral sidelobes are observed and could be attributed to the four-wave-mixing effect between dual-wavelength pulses at the carbon nanotube mode-locker. These results could provide further insight into the design and realization of such dual-wavelength ultrafast lasers for different applications such as dual-comb metrology as well as better understanding of the inter-pulse interactions in such dual-comb lasers.
Red to green emitters from InGaP/InAlGaP laser structure by strain-induced quantum-well intermixing
Al-Jabr, Ahmad
2016-04-28
We increased the Al content in the single quantum well InGaP/InAlGaP laser by strain-induced quantum well intermixing, and obtained a considerable enhancement (close to ten-fold increase) in the photoluminescence (PL) intensity. Among the annealing process investigated, we achieved lasing at 638 nm in conjunction with reduction in the lasing threshold current by close to 500 mA in a moderately intermixed laser. Lasing in orange color, as well as spontaneous emission in the yellow and green color regime, were also achieved by extending the annealing conditions. The significance of the current work became apparent when one considers that achieving these tunable wavelengths by increasing the Al content in quantum wells during epitaxy growth leads to severe lattice-mismatch and poor material quality. Hence, our Al "drive-in" intermixing process is a viable approach for forming Al-rich InAlGaP quantum well, which is essential for realizing efficient optoelectronic devices in the "green-yellow-orange gap". © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Wavelength dependent deformation in a laser peened Ti-2.5Cu alloy
Energy Technology Data Exchange (ETDEWEB)
Umapathi, A., E-mail: umapathi.arimakula@gmail.com; Swaroop, S., E-mail: n.r.sathya.swaroop@gmail.com
2017-01-27
Laser peening without coating (LPwC) was performed on a Ti-2.5Cu alloy at wavelengths of 1064 and 532 nm and at a constant power density of approximately 7 GW cm{sup −2} with overlap rates of 53%, 63% and 73%. Surface softening due to thermal interaction of laser beam with material was observed till a depth of 500 µm (at 532 nm) and 200 µm (at 1064 nm), based on hardness data. This was corroborated (rather weakly) by residual stress analysis. In addition, softening due to mechanical effects (adiabatic heating) was observed in the bulk. Although there was an increase in mechanical softening with increase in overlap rates at 532 nm, it was observed, upon comparison with peened samples at 1064 nm, that the mechanical softening is a function of wavelength of radiation used for peening. It was observed that the onset of softening was earlier if the wavelength was shorter. Further, evidence of hardening in the form of twinning was found for the 1064 nm case while it was absent for the 532 nm case, for 73% overlap. The workhardened depth was more than 1000 µm, not observed in earlier studies based on residual stress analysis. The direct consequence of softening effect was found in the fatigue results. The fatigue life extended by a factor of 1.4 and 2.3 for the samples peened at 532 nm and 1064 nm respectively, consistent with the observed wavelength dependent onset of softening.
Wavelength-controlled external-cavity laser with a silicon photonic crystal resonant reflector
Gonzalez-Fernandez, A. A.; Liles, Alexandros A.; Persheyev, Saydulla; Debnath, Kapil; O'Faolain, Liam
2016-03-01
We report the experimental demonstration of an alternative design of external-cavity hybrid lasers consisting of a III-V Semiconductor Optical Amplifier with fiber reflector and a Photonic Crystal (PhC) based resonant reflector on SOI. The Silicon reflector comprises a polymer (SU8) bus waveguide vertically coupled to a PhC cavity and provides a wavelength-selective optical feedback to the laser cavity. This device exhibits milliwatt-level output power and sidemode suppression ratio of more than 25 dB.
Dual-wavelength mid-infrared CW and Q-switched laser in diode end-pumped Tm,Ho:GdYTaO4 crystal
Wang, Beibei; Gao, Congcong; Dou, Renqin; Nie, Hongkun; Sun, Guihua; Liu, Wenpeng; Yu, Haijuan; Wang, Guoju; Zhang, Qingli; Lin, Xuechun; He, Jingliang; Wang, Wenjun; Zhang, Bingyuan
2018-02-01
Dual-wavelength continuous-wave and Q-switched lasers are demonstrated in a Tm,Ho:GdYTaO4 crystal under 790 nm laser diode end pumping for the first time to the best of our knowledge. The laser operates with a dual wavelength at 1949.677 nm and 2070 nm for continuous-wave with a spacing of about 120 nm. The maximum output power is 0.332 W with a pump power of 3 W. By using graphene as the saturable absorber, a passively Q-switched operation is performed with a dual-wavelength at 1950.323 nm and 2068.064 nm with a wavelength interval of about 118 nm. The maximum average output power of the Q-switched laser goes up to 200 mW with a minimum pulse duration of 1.2 µs and a maximum repetition rate of 34.72 kHz.
Extremely high-brightness kW-class fiber coupled diode lasers with wavelength stabilization
Huang, Robin K.; Chann, Bien; Glenn, John D.
2011-06-01
TeraDiode has produced ultra-high brightness fiber-coupled direct diode lasers. A fiber-coupled direct diode laser with a power level of 1,040 W from a 200 μm core diameter, 0.18 numerical aperture (NA) output fiber at a single center wavelength was demonstrated. This was achieved with a novel beam combining and shaping technique using COTS diode lasers. The fiber-coupled output corresponds to a Beam Parameter Product (BPP) of 18 mm-mrad and is the lowest BPP kW-class direct diode laser yet reported. The laser has been used to demonstrate laser cutting and welding of steel sheet metal up to 6.65 mm thick. Higher brightness fiber-coupled diode lasers, including a module with 418 W of power coupled to a 100 μm, 0.15 NA fiber, have also been demonstrated.
Wiegelmann, Marcel; Soltwisch, Jens; Jaskolla, Thorsten W; Dreisewerd, Klaus
2013-09-01
A high analytical sensitivity in ultraviolet matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is only achieved if the laser wavelength corresponds to a high optical absorption of the matrix. Laser fluence and the physicochemical properties of the compounds, e.g., the proton affinity, also influence analytical sensitivity significantly. In combination, these parameters determine the amount of material ejected per laser pulse and the ion yield, i.e., the fraction of ionized biomolecules. Here, we recorded peptide ion signal intensities as a function of these parameters. Three cinnamic acid matrices were investigated: α-cyano-4-hydroxycinnamic acid, α-cyano-4-chlorocinnamic acid, and α-cyano-2,4-difluorocinnamic acid. In addition, 2,5-dihydroxybenzoic acid was used in comparison experiments. Ion signal intensities "per laser shot" and integrated ion signal intensities were acquired over 900 consecutive laser pulses applied on distinct positions on the dried-droplet sample preparations. With respect to laser wavelength, the two standard MALDI wavelengths of 337/355 nm were investigated. Also, 305 or 320 nm was selected to account for the blue-shifted absorption profiles of the halogenated derivatives. Maximal peptide ion intensities were obtained if the laser wavelength fell within the peak of the absorption profile of the compound and for fluences two to three times the corresponding ion detection threshold. The results indicate ways for improving the analytical sensitivity in MALDI-MS, and in particular for MALDI-MS imaging applications where a limited amount of material is available per irradiated pixel.
Directory of Open Access Journals (Sweden)
Keisuke Hashimura
2014-05-01
Full Text Available Molecules such as water, proteins and lipids that are contained in biological tissue absorb mid-infrared (MIR light, which allows such light to be used in laser surgical treatment. Esters, amides and water exhibit strong absorption bands in the 5–7 μm wavelength range, but at present there are no lasers in clinical use that can emit in this range. Therefore, the present study focused on the quantum cascade laser (QCL, which is a new type of semiconductor laser that can emit at MIR wavelengths and has recently achieved high output power. A high-power QCL with a peak wavelength of 5.7 μm was evaluated for use as a laser scalpel for ablating biological soft tissue. The interaction of the laser beam with chicken breast tissue was compared to a conventional CO2 laser, based on surface and cross-sectional images. The QCL was found to have sufficient power to ablate soft tissue, and its coagulation, carbonization and ablation effects were similar to those for the CO2 laser. The QCL also induced comparable photothermal effects because it acted as a pseudo-continuous wave laser due to its low peak power. A QCL can therefore be used as an effective laser scalpel, and also offers the possibility of less invasive treatment by targeting specific absorption bands in the MIR region.
Short-wavelength soft-x-ray laser pumped in double-pulse single-beam non-normal incidence
International Nuclear Information System (INIS)
Zimmer, D.; Ros, D.; Guilbaud, O.; Habib, J.; Kazamias, S.; Zielbauer, B.; Bagnoud, V.; Ecker, B.; Aurand, B.; Kuehl, T.; Hochhaus, D. C.; Neumayer, P.
2010-01-01
We demonstrated a 7.36 nm Ni-like samarium soft-x-ray laser, pumped by 36 J of a neodymium:glass chirped-pulse amplification laser. Double-pulse single-beam non-normal-incidence pumping was applied for efficient soft-x-ray laser generation. In this case, the applied technique included a single-optic focusing geometry for large beam diameters, a single-pass grating compressor, traveling-wave tuning capability, and an optimized high-energy laser double pulse. This scheme has the potential for even shorter-wavelength soft-x-ray laser pumping.
Comparison of SHG Power Modulation by Wavelength Detuning of DFB- and DBR-Tapered Laser Diodes
DEFF Research Database (Denmark)
Christensen, Mathias; Hansen, Anders Kragh; Noordegraaf, Danny
2016-01-01
of the response of the second harmonic light to perturbations of the infrared laser diode and compare how the response differs for DFB- and DBR-Tapered laser diodes. We show that the visible light can be modulated from CW to kHz with modulation depths above 90% by wavelength detuning the laser diode.......Pulsed visible lasers are used for a number of applications such as laser displays and medical treatments. Generating this visible light by direct frequency doubling of high power diode lasers opens new possibilities on how the power modulation can be performed. We present an investigation...
Energy Technology Data Exchange (ETDEWEB)
Ebrahim, N A; Mouris, J F; Davis, R W
1994-12-01
In this report we describe the Chalk River dual-wavelength, short-pulse, single-mode, high-power CO{sub 2} laser facility for research in laser particle acceleration and CANDU materials modifications. The facility is designed and built around UV-preionized transversely-excited atmospheric-pressure (TEA) Lumonics CO{sub 2} laser discharge modules. Peak focussed power densities of up to 2 x 10{sup 14} W/cm{sup 2} in 500 ps pulses have been obtained. (author). 10 refs., 9 figs.
Picosecond pulses from wavelength-swept continuous-wave Fourier domain mode-locked lasers.
Eigenwillig, Christoph M; Wieser, Wolfgang; Todor, Sebastian; Biedermann, Benjamin R; Klein, Thomas; Jirauschek, Christian; Huber, Robert
2013-01-01
Ultrafast lasers have a crucial function in many fields of science; however, up to now, high-energy pulses directly from compact, efficient and low-power semiconductor lasers are not available. Therefore, we introduce a new approach based on temporal compression of the continuous-wave, wavelength-swept output of Fourier domain mode-locked lasers, where a narrowband optical filter is tuned synchronously to the round-trip time of light in a kilometre-long laser cavity. So far, these rapidly swept lasers enabled orders-of-magnitude speed increase in optical coherence tomography. Here we report on the generation of ~60-70 ps pulses at 390 kHz repetition rate. As energy is stored optically in the long-fibre delay line and not as population inversion in the laser-gain medium, high-energy pulses can now be generated directly from a low-power, compact semiconductor-based oscillator. Our theory predicts subpicosecond pulses with this new technique in the future.
Iodine-stabilized single-frequency green InGaN diode laser.
Chen, Yi-Hsi; Lin, Wei-Chen; Shy, Jow-Tsong; Chui, Hsiang-Chen
2018-01-01
A 520-nm InGaN diode laser can emit a milliwatt-level, single-frequency laser beam when the applied current slightly exceeds the lasing threshold. The laser frequency was less sensitive to diode temperature and could be finely tuned by adjusting the applied current. Laser frequency was stabilized onto a hyperfine component in an iodine transition through the saturated absorption spectroscopy. The uncertainty of frequency stabilization was approximately 8×10 -9 at a 10-s integration time. This compact laser system can replace the conventional green diode-pumped solid-state laser and applied as a frequency reference. A single longitudinal mode operational region with diode temperature, current, and output power was investigated.
Growth and development of Arabidopsis thaliana under single-wavelength red and blue laser light
Ooi, Amanda Siok Lee
2016-09-23
Indoor horticulture offers a sensible solution for sustainable food production and is becoming increasingly widespread. However, it incurs high energy and cost due to the use of artificial lighting such as high-pressure sodium lamps, fluorescent light or increasingly, the light-emitting diodes (LEDs). The energy efficiency and light quality of currently available horticultural lighting is suboptimal, and therefore less than ideal for sustainable and cost-effective large-scale plant production. Here, we demonstrate the use of high-powered single-wavelength lasers for indoor horticulture. They are highly energy-efficient and can be remotely guided to the site of plant growth, thus reducing on-site heat accumulation. Furthermore, laser beams can be tailored to match the absorption profiles of different plant species. We have developed a prototype laser growth chamber and demonstrate that plants grown under laser illumination can complete a full growth cycle from seed to seed with phenotypes resembling those of plants grown under LEDs reported previously. Importantly, the plants have lower expression of proteins diagnostic for light and radiation stress. The phenotypical, biochemical and proteome data show that the single-wavelength laser light is suitable for plant growth and therefore, potentially able to unlock the advantages of this next generation lighting technology for highly energy-efficient horticulture.
Finesse of transparent tissue cutting by ultrafast lasers at various wavelengths
Wang, Jenny; Schuele, Georg; Palanker, Daniel
2015-12-01
Transparent ocular tissues, such as the cornea and crystalline lens, can be ablated or dissected using short-pulse lasers. In refractive and cataract surgeries, the cornea, lens, and lens capsule can be cut by producing dielectric breakdown in the focus of a near-infrared (IR) femtosecond laser, which results in explosive vaporization of the interstitial water, causing mechanical rupture of the surrounding tissue. Here, we compare the texture of edges of lens capsule cut by femtosecond lasers with IR and ultraviolet (UV) wavelengths and explore differences in interactions of these lasers with biological molecules. Scanning electron microscopy indicates that a 400-nm laser is capable of producing very smooth cut edges compared to 800 or 1030 nm at a similar focusing angle. Using gel electrophoresis and liquid chromatography/mass spectrometry, we observe laser-induced nonlinear breakdown of proteins and polypeptides by 400-nm femtosecond pulses above and below the dielectric breakdown threshold. On the other hand, 800-nm femtosecond lasers do not produce significant dissociation even above the threshold of dielectric breakdown. However, despite this additional interaction of UV femtosecond laser with proteins, we determine that efficient cutting requires plasma-mediated bubble formation and that remarkably smooth edges are the result of reduced thresholds and smaller focal volume.
Lee, Changmin
2017-07-12
Data communication based on white light generated using a near-ultraviolet (NUV) laser diode (LD) pumping red-, green-, and blue-emitting (RGB) phosphors was demonstrated for the first time. A III-nitride laser diode (LD) on a semipolar (2021) substrate emitting at 410 nm was used for the transmitter. The measured modulation bandwidth of the LD was 1 GHz, which was limited by the avalanche photodetector. The emission from the NUV LD and the RGB phosphor combination measured a color rendering index (CRI) of 79 and correlated color temperature (CCT) of 4050 K, indicating promise of this approach for creating high quality white lighting. Using this configuration, data was successfully transmitted at a rate of more than 1 Gbps. This NUV laser-based system is expected to have lower background noise from sunlight at the LD emission wavelength than a system that uses a blue LD due to the rapid fall off in intensity of the solar spectrum in the NUV spectral region.
Lee, Changmin; Shen, Chao; Cozzan, Clayton; Farrell, Robert M; Speck, James S; Nakamura, Shuji; Ooi, Boon S; DenBaars, Steven P
2017-07-24
Data communication based on white light generated using a near-ultraviolet (NUV) laser diode (LD) pumping red-, green-, and blue-emitting (RGB) phosphors was demonstrated for the first time. A III-nitride laser diode (LD) on a semipolar (2021¯) substrate emitting at 410 nm was used for the transmitter. The measured modulation bandwidth of the LD was 1 GHz, which was limited by the avalanche photodetector. The emission from the NUV LD and the RGB phosphor combination measured a color rendering index (CRI) of 79 and correlated color temperature (CCT) of 4050 K, indicating promise of this approach for creating high quality white lighting. Using this configuration, data was successfully transmitted at a rate of more than 1 Gbps. This NUV laser-based system is expected to have lower background noise from sunlight at the LD emission wavelength than a system that uses a blue LD due to the rapid fall off in intensity of the solar spectrum in the NUV spectral region.
Energy Technology Data Exchange (ETDEWEB)
Binetti, Simona [Department of Materials Science and Milano-Bicocca Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milano (Italy); Le Donne, Alessia, E-mail: alessia.ledonne@mater.unimib.it [Department of Materials Science and Milano-Bicocca Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milano (Italy); Rolfi, Andrea [Department of Materials Science and Milano-Bicocca Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milano (Italy); Jäggi, Beat; Neuenschwander, Beat [Bern University of Applied Sciences, Engineering and Information Technology, Institute for Applied Laser, Photonics and Surface Technologies ALPS, Pestalozzistrasse 20, CH-3400 Burgdorf (Switzerland); Busto, Chiara [ENI Spa, Via Giacomo Fauser, 4, 28100 Novara (Italy); Frigeri, Cesare [CNR-IMEM Institute, Parco Area Delle Scienze 37/A, Fontanini, 43010 Parma (Italy); Scorticati, Davide; Longoni, Luca; Pellegrino, Sergio [Laserpoint Srl, Via Della Burrona 51, 20090 Vimodrone, Milano (Italy)
2016-05-15
Highlights: • Self-organized surface structures were produced by picosecond laser pulses on mc-Si. • Three laser wavelengths were used which effectively reduce Si reflectivity up to 8%. • The subsurface damage induced by the three lasers was studied in detail. • μ-Raman, PL and TEM proved that UV laser provides the lowest subsurface damage. • UV laser induced damage is located above the depletion region of the p–n junction. - Abstract: Self-organized surface structures were produced by picosecond laser pulses on multi-crystalline silicon for photovoltaic applications. Three different laser wavelengths were employed (i.e. 1064 nm, 532 nm and 355 nm) and the resulting morphologies were observed to effectively reduce the reflectivity of the samples after laser irradiation. Besides, a comparative study of the laser induced subsurface damage generated by the three different wavelengths was performed by confocal micro-Raman, photoluminescence and transmission electron microscopy. The results of both the structural and optical characterization showed that the mc-Si texturing performed with the laser at 355 nm provides surface reflectivity between 11% and 8% over the spectral range from 400 nm to 1 μm, while inducing the lowest subsurface damage, located above the depletion region of the p–n junction.
Investigation of damage threshold to TiO2 coatings at different laser wavelength and pulse duration
International Nuclear Information System (INIS)
Yao Jianke; Fan Zhengxiu; Jin Yunxia; Zhao Yuanan; He Hongbo; Shao Jianda
2008-01-01
Laser-induced damages to TiO 2 single layers and TiO 2 /SiO 2 high reflectors at laser wavelength of 1064 nm, 800 nm, 532 nm, and pulse width of 12 ns, 220 ps, 50 fs, 8 ns are investigated. All films are prepared by electron beam evaporation. The relations among microstructure, chemical composition, optical properties and laser-induced damage threshold (LIDT), have been researched. The dependence of damage mechanism on laser wavelength and pulse width is discussed. It is found that from 1064 nm to 532 nm, LIDT is mainly absorption related, which is determined by film's extinction coefficient and stoichiometric defects. The rapid decrease of LIDT at 800 nm is due to the pulse width factor. TiO 2 coatings are mainly thermally by damaged at long pulse (τ ≥ 220 ps). The damage shows ablation feature at 50 fs
Xu, Jiangmin; Chen, Chao; Zhang, Tengfei; Han, Zhenchun
2017-03-03
Based on PVDF (piezoelectric sensing techniques), this paper attempts to study the propagation law of shock waves in brittle materials during the process of three-wavelength laser irradiation of polysilicon, and discusses the formation mechanism of thermal shock failure. The experimental results show that the vapor pressure effect and the plasma pressure effect in the process of pulsed laser irradiation lead to the splashing of high temperature and high density melt. With the decrease of the laser wavelength, the laser breakdown threshold decreases and the shock wave is weakened. Because of the pressure effect of the laser shock, the brittle fracture zone is at the edge of the irradiated area. The surface tension gradient and surface shear wave caused by the surface wave are the result of coherent coupling between optical and thermodynamics. The average propagation velocity of laser shock wave in polysilicon is 8.47 × 103 m/s, and the experiment has reached the conclusion that the laser shock wave pressure peak exponentially distributes attenuation in the polysilicon.
Directory of Open Access Journals (Sweden)
Jiangmin Xu
2017-03-01
Full Text Available Based on PVDF (piezoelectric sensing techniques, this paper attempts to study the propagation law of shock waves in brittle materials during the process of three-wavelength laser irradiation of polysilicon, and discusses the formation mechanism of thermal shock failure. The experimental results show that the vapor pressure effect and the plasma pressure effect in the process of pulsed laser irradiation lead to the splashing of high temperature and high density melt. With the decrease of the laser wavelength, the laser breakdown threshold decreases and the shock wave is weakened. Because of the pressure effect of the laser shock, the brittle fracture zone is at the edge of the irradiated area. The surface tension gradient and surface shear wave caused by the surface wave are the result of coherent coupling between optical and thermodynamics. The average propagation velocity of laser shock wave in polysilicon is 8.47 × 103 m/s, and the experiment has reached the conclusion that the laser shock wave pressure peak exponentially distributes attenuation in the polysilicon.
Saiki, Masayuki; Ishii, Katsunori; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio
2011-03-01
Optical technologies have good potential for caries detection, prevention, excavation, and the realization of minimal intervention dentistry. This study aimed to develop a selective excavation technique of carious tissue using the specific absorption in 6 μm wavelength range. Bovine dentin demineralized with lactic acid solution was used as a carious dentin model. A mid-infrared tunable pulsed laser was obtained by difference-frequency generation technique. The wavelength was tuned to 6.02 and 6.42 μm which correspond to absorption bands called amide I and amide II, respectively. The laser delivers 5 ns pulse width at a repetition rate of 10 Hz. The morphological change after irradiation was observed with a scanning electron microscope, and the measurement of ablation depth was performed with a confocal laser microscope. At λ = 6.02 μm and the average power density of 15 W/cm2, demineralized dentin was removed selectively with less-invasive effect on sound dentin. The wavelength of 6.42 μm also showed the possibility of selective removal. High ablation efficiency and low thermal side effect were observed using the nanosecond pulsed laser with λ = 6.02 μm. In the near future, development of compact laser device will open the minimal invasive laser treatment to the dental clinic.
Laser wavelength dependent properties of YBa2Cu3O7-δ thin films deposited by laser ablation
International Nuclear Information System (INIS)
Koren, G.; Gupta, A.; Baseman, R.J.; Lutwyche, M.I.; Laibowitz, R.B.
1989-01-01
YBa 2 Cu 3 O 7-δ thin films were deposited onto (100) SrTiO 3 substrates using 1064, 532, 355, 248, and 193 nm laser ablation. Transport measurements show lower normal-state resistivities and higher critical currents in films deposited by the shorter wavelength lasers. The surface morphology of the films was rough with large particulates when the 1064 nm laser was used whereas much smoother surfaces with fewer and smaller particulates were obtained with the UV lasers. It is suggested that the better film quality obtained when the UV lasers are used is due to a small absorption depth of the UV photons in the ceramic target and to higher absorption by the ablated fragments. This leads to smaller ablated species and further fragmentation in the hotter plume and, therefore, to smoother and denser films
Thomas, J; Buzzini, P; Massonnet, G; Reedy, B; Roux, C
2005-09-10
Raman spectroscopy was investigated to determine the optimal conditions, mainly laser wavelength/s, for the analysis of the commonly encountered black/grey and blue cotton fibres dyed with reactive dyes. In this first part, a single blue cotton fibre, its three dye components, and an undyed cotton fibre were analysed with five different laser wavelengths from two different Raman microprobe spectrometers. The quality of the spectra, fibre degradation and speed of acquisition were used to determine that, under the conditions used, the 785 and 830 nm lasers gave superior results. The 632.8 nm laser wavelengths provided good results with little acquisition time and no spectral degradation. Results indicate that, at least, the major dye component could be identified using Raman spectroscopy.
Development of a two-wavelength IR laser absorption diagnostic for propene and ethylene
Parise, T. C.; Davidson, D. F.; Hanson, R. K.
2018-05-01
A two-wavelength infrared laser absorption diagnostic for non-intrusive, simultaneous quantitative measurement of propene and ethylene was developed. To this end, measurements of absorption cross sections of propene and potential interfering species at 10.958 µm were acquired at high-temperatures. When used in conjunction with existing absorption cross-section measurements of ethylene and other species at 10.532 µm, a two-wavelength diagnostic was developed to simultaneously measure propene and ethylene, the two small alkenes found to generally dominate the final decomposition products of many fuel hydrocarbon pyrolysis systems. Measurements of these two species is demonstrated using this two-wavelength diagnostic scheme for propene decomposition between 1360 and 1710 K.
International Nuclear Information System (INIS)
Fuente, G.F. de la; Diez, J.C.; Angurel, L.A.; Pena, J.I.; Sotelo, A.; Navarro, R.
1995-01-01
Laser floating zone processing methods are particularly suitable for studying crystal growth and the development of texture from the melt in many materials used in electrooptics, for example. A system is described that allows different laser wavelengths to be used, and first results on BSCCO superconducting fibers processed using different lasers are presented. (orig.)
Laser Treatment of Professional Tattoos With a 1064/532-nm Dual-Wavelength Picosecond Laser.
Kauvar, Arielle N B; Keaney, Terrence C; Alster, Tina
2017-12-01
Picosecond-domain laser pulses improve the photomechanical disruption of tattoos. This study evaluates the efficacy and safety of a novel, dual-wavelength, 1,064/532-nm, picosecond-domain laser for tattoo clearance. This was a prospective, self-controlled, clinical study of 34 subjects with 39 tattoos treated at 2 sites with an interval of 4.8 ± 1.6 weeks and up to 10 treatments (mean, 7.5). Blinded evaluation and investigator assessment of serial digital images was performed to evaluate treatment efficacy in the 36 tattoos that received at least 3 treatments. Investigators also assessed efficacy before each treatment visit up to 10 treatments. Safety and tolerability was evaluated for all 39 tattoos that underwent at least 1 treatment. Blinded evaluation demonstrated that lightening of tattoos was achieved in all subjects, with 86% (31 of 36 tattoos) showing at least a 50% clearance after 3 treatments. Adverse events were few and transient in nature. Patient satisfaction and treatment tolerability were high. Treatment of single-colored and multicolored tattoos with this novel 1,064/532-nm picosecond laser is highly safe and effective.
Zhou, Yuxin; Wang, Xin; Tang, Zijuan; Lou, Shuqin
2018-05-01
In this paper, a switchable multi-wavelength erbium-doped fiber ring laser based on a tapered in-line Mach–Zehnder interferometer is proposed. The in-line Mach–Zehnder interferometer is fabricated by splicing a large-core fiber between two segments of single mode fibers, in which the first splicing point is tapered and the second splicing point is connected directly. By carefully rotating the polarization controller, switchable single-, dual-, triple- and quad-wavelength lasing outputs can be obtained with a side mode suppression ratio higher than 50 dB. The maximal peak power difference of multi-wavelength lasing is 3.67 dB, demonstrating a good power equalization performance. Furthermore, the proposed laser is proven to be very stable at room temperature. The wavelength shifts and peak power fluctuations are less than 0.02 nm and 1.3 dB over half an hour. In addition, stable quintuple-wavelength lasing with a side mode suppression ratio higher than 50 dB can also be realized when the filter length is changed.
Modeling the DBR laser used as wavelength conversion device
DEFF Research Database (Denmark)
Braagaard, Carsten; Mikkelsen, Benny; Durhuus, Terji
1994-01-01
In this paper, a novel and efficient way to model the dynamic field in optical DBR-type semiconductor devices is presented. The model accounts for the longitudinal carrier, photon, and refractive index distribution. Furthermore, the model handles both active and passive sections that may include...... gratings. Thus, simulations of components containing, e.g., gain sections, absorptive sections, phase sections, and gratings, placed arbitrarily along the longitudinal direction of the cavity, are possible. Here, the model has been used for studying the DBR laser as a wavelength converter. Particularly...
International Nuclear Information System (INIS)
Pal, Atasi; Chen, Shu Ying; Sun, Tong; Grattan, K T V; Sen, Ranjan
2013-01-01
A high-Q and low threshold laser resonator, operating in the 2 μm wavelength region, has been demonstrated by coupling a thulium-doped silica microsphere to a tapered fibre. Microspheres with diameters ranging from fifty to a few hundred micrometres were carefully fabricated for this purpose by melting an etched-clad thulium-doped silica fibre tip using a focused beam from a CO 2 laser, while the tapered fibre with waist diameter in the desired range of 2 μm was fabricated by using heating and stretching of standard single-mode telecommunication fibre. The tapered fibre served the dual purpose of transporting pump power into the sphere and allowing the extraction of the resulting laser emission. Under excitation at a wavelength of ∼1.6 μm, lasing occurred at wavelengths over the range from 1.9 to 2.0 μm. Single-mode laser operation was obtained by exciting the fundamental whispering gallery mode resonance of the microsphere, while multi-mode lasing occurred for non-fundamental mode excitation. The threshold power of the laser was measured to be about 50 μW delivered pump power, and a maximum laser power of 0.8 mW at around 1.94 μm was observed for a 6 mW pump power, operating at wavelengths around 1.6 μm. The laser was designed as a low threshold and compact source for miniaturized gas sensing devices operating over this important wavelength region. (letter)
Jasim, A. A.; Ahmad, H.
2017-12-01
The generation and switching of dual-wavelength laser based on compact coupled microfiber Mach-Zehnder interferometer (CM-MZI) is reported. The CM-MZI is constructed by overlapping two portions of a single tapered optical fiber which has a diameter of 9 μm as to create multi-mode interference and also to produce spatial mode beating as to suppress mode competition in the homogeneous gain medium. The system is able to generate a dual-wavelength laser output that can be switched with the aid of the polarization rotation technique. Four dual-wavelength oscillation pairs are obtained from the interference fringe peaks of the CM-MZI comb filter with a switched channel spacing of 1.5 nm, 3.0 nm, and 6.0 nm. The wavelength spacing is stable at different pump powers. The lasing wavelength has a 3-dB linewidth of about 30 pm and peak-to-floor ration of about 55 dB at a pump power of 38 mW.
1-kilowatt CW all-fiber laser oscillator pumped with wavelength-beam-combined diode stacks.
Xiao, Y; Brunet, F; Kanskar, M; Faucher, M; Wetter, A; Holehouse, N
2012-01-30
We have demonstrated a monolithic cladding-pumped ytterbium-doped single all-fiber laser oscillator generating 1 kW of CW signal power at 1080 nm with 71% slope efficiency and near diffraction-limited beam quality. Fiber components were highly integrated on "spliceless" passive fibers to promote laser efficiency and alleviate non-linear effects. The laser was pumped through a 7:1 pump combiner with seven 200-W 91x nm fiber-pigtailed wavelength-beam-combined diode-stack modules. The signal power of such a single all-fiber laser oscillator showed no evidence of roll-over, and the highest output was limited only by available pump power.
International Nuclear Information System (INIS)
Qi Lanying; Jiang Xiaohua; Zhao Xuewei; Li Sanwei; Zhang Wenhai; Li Chaoguang; Zheng Zhijian; Ding Yongkun
1999-12-01
The experiments on gold-disk and hohlraum and plastic hydrocarbon (CH) film targets irradiated by laser beams with wavelength 0.35 μm (Xingguang-II) and 0.53 μm (Shenguang-I) are performed. The characteristics of hot electrons are commonly deduced from spectrum of hard X-ray. Associated with the measurement of backward SRS and 3/2ω 0 , the production mechanism of hot electrons for different target type is analyzed in laser plasma with shorter wavelength. A effective way to suppress hot electrons has been found
Ji, Wei; Chang, Jun
2013-07-01
In this paper, we design a WDM-RoF-PON based on linearly-polarized dual-wavelength fiber laser and CSRZ-DPSK, which can achieve wire-line and wireless access synchronously. With the CSRZ-DPSK modulation, the wireless access in ONU can save RF source and the frequency of radio carrier can be controlled by OLT. The dual-wavelength fiber laser is the union light source of WDM-PON with polarization multiplexing. By the RSOA and downstream light source reusing, the ONU can save omit laser source and makes the WDM-PON to be colorless. The networking has the credible transmission property, including wireless access and fiber transmission. The networking also has excellent covering range.
International Nuclear Information System (INIS)
Stober, F.; Lichtenthaler, H.K.
1992-01-01
The UV-laser-induced blue, green and red fluorescence-emission spectra were used to characterize the pigment status of etiolated leaves of wheat (Triticum aestivum L.) during a 48 h greening period under white light conditions. Upon UV-light excitation (337 nm) leaves not only show a fluorescence emission in the red spectral region between 650 and 800nm (chlorophyll fluorescence with maxima near 690nm and 735 nm), but also in the blue and green regions between 400 to 570 nm with maxima or shoulders near 450 nm (blue) and 530 nm (green). During greening of etiolated leaves the chlorophyll-fluorescence ratio F690/F735 strongly correlated with the total chlorophyll content and the ratio of the chlorophylls to the carotenoids (a+b/x+c). The ratio of the blue to the green fluorescence F450/F530 was also correlated with the total chlorophyll content and the ratio of chlorophylls to total carotenoids (a+b/x+c). Consequently, there also existed a correlation between the chlorophyll-fluorescence ratio F690/F735 and the ratio of the blue to green fluorescence F450/F530. In contrast, the ratios of the blue to red fluorescences F450/F690 and F450/F735 did not show clear relations to the pigment content of the investigated plants. The particular shape of the UV-laser-induced-fluorescence emission spectra of wheat leaves as well as the dependencies of the fluorescence ratios on the pigment content are due to a partial and differential reabsorption of the emitted fluorescences by the photosynthetic pigments
Endoluminal laser delivery mode and wavelength effects on varicose veins in an ex vivo model.
Massaki, Ane B M N; Kiripolsky, Monika G; Detwiler, Susan P; Goldman, Mitchel P
2013-02-01
Endovenous laser ablation (EVLA) has been shown to be effective for the elimination of saphenous veins and associated reflux. Mechanism is known to be heat related, but precise way in which heat causes vein ablation is not completely known. This study aimed to determine the effects of various endovenous laser wavelengths and delivery modes on ex vivo human vein both macroscopically and microscopically. We also evaluated whether protected-tip fibers, consisting of prototype silica fibers with a metal tube over the distal end, reduced vein wall perforations compared with non-protected-tip fibers. An ex vivo EVLA model with human veins harvested during ambulatory phlebectomy procedures was used. Six laser fiber combinations were tested: 810 nm continuous wave (CW) diode laser with a flat tip fiber, 810 CW diode laser with a protected tip fiber, 1,320 nm pulsed Nd:YAG laser, 1,310 nm CW diode laser, 1,470 nm CW diode laser, and 2,100 nm pulsed Ho:YAG laser. Perforation or full thickness necrosis of a portion of the vein wall was observed in 5/11 (45%), 0/11 (0%), 3/22 (14%), 7/11 (64%), 4/6 (67%), and 5/10 (50%) of cross-sections of veins treated with the 810 nm CW diode laser with a flat tip fiber, the 810 CW diode laser with a protected tip fiber, the 1,320 nm pulsed Nd:YAG laser, the 1,310 nm CW diode laser, the 1,470 nm CW diode laser, and the 2,100 nm pulsed Ho:YAG laser, respectively. Our results have shown that the delivery mode, pulsed Nd:YAG versus CW, may be just as important as the wavelength. Therefore, the 1,310 nm CW laser may not be equivalent to the 1,320 nm pulsed laser. In addition, protected 810 nm fibers may be less likely to yield wall perforations than their non-protected counterparts. Copyright © 2012 Wiley Periodicals, Inc.
Evaluation of Wavelength Detuning to Mitigate Cross-Beam Energy Transfer Using the Nike Laser
McKenty, P. W.; Marozas, J. A.; Weaver, J.; Obenschain, S. P.; Schmitt, A. J.
2015-11-01
Cross-beam energy transfer (CBET) has become a serious threat to the overall success of direct-drive experiments, and especially for polar-direct-drive (PDD) ignition experiments. CBET redirects incident laser light before it can be absorbed into the target, thereby degrading overall target performance. CBET is particularly detrimental over the equator of the target, which is hydrodynamically very sensitive to such losses in the PDD configuration. A promising solution uses laser wavelength detuning between beams to shift the resonance, thereby reducing the interaction cross section between them. Testing this process for direct drive is now underway at the Nike laser at the Naval Research Laboratory. Calculations evaluating the effect CBET has on the scattered-light signals indicate such an experiment will demonstrate the benefits of wavelength detuning for direct-drive implosions. Two-dimensional simulation results will be presented, predicting the effect for both spherical and cylindrical experiments. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.
International Nuclear Information System (INIS)
Lin, Wang; Feng-Ping, Yan; Xiang-Qiao, Mao; Shui-Sheng, Jian
2008-01-01
A new polarization-independent dual-wavelength fibre laser by fabricating a uniform FBG and a chirped FBG in a polarization-maintaining erbium-doped fibre (PM-EDF) is proposed and demonstrated. The wavelength spacing is 0.18nm and the optical signal-to-noise ratio is greater than 50dB with pump power of 246mW. Chirped FBG is used to make the reflectivity wavelengths of two PM-FBGs match easier. Since both EDF and FBGs are polarization-maintaining without splices and the two wavelengths are polarization-independent, the maximum amplitude variation and wavelength shifts for both lasing wavelength with 3-min intervals over a period of six hours are less than 0.2 dB and 0.005 nm, respectively, which shows stable dual-wavelength output
Directory of Open Access Journals (Sweden)
Daniela Litscher
2018-03-01
Full Text Available Background: One of the most commonly used auricular acupuncture points selected for different pain treatment regimens is Shenmen. This point on the ear has been recognized as having a wide number of applications, as found by scientific investigation. Methods: Within this crossover study, the ear acupoint Shenmen was stimulated with two different kinds of laser (green, 532 nm and yellow, 589 nm in 22 healthy volunteers (13 female, 9 male; mean age ± SD = 25.3 ± 4.1 years; range 21–36 years. Both green and yellow lasers were used for 15 min in the same volunteers in two different sessions. Results: The most prominent finding was that systolic blood pressure decreased significantly (p = 0.048 after yellow laser stimulation. Heart rate also decreased significantly (p < 0.001, whereas heart rate variability ratio low frequency (LF/high frequency (HF (p < 0.001 increased. The effects were significantly more pronounced in females than in males. In addition, the temperature was measured, and temperature increases were demonstrated at different locations on the ear using imaging methods. Conclusions: This study shows evidence of the effect of auricular laser acupuncture. However, a comparison with other publications was impossible because this is the first study using green and yellow laser stimulation on the ear.
Monitoring tree health with a dual-wavelength terrestrial laser scanner
Hancock, S.
2013-12-01
Steven Hancock1, Rachel Gaulton1, Mark Danson2 1School of Civil Engineering and Geosciences, Newcastle University, UK, steven.hancock@ncl.ac.uk, rachel.gaulton@ncl.ac.uk 2 School of Environment and Life Sciences, University of Salford, UK, F.M.Danson@salford.ac.uk Forests are a vital part of the Earth's carbon cycle and drive interactions between the land and atmosphere. Accurate and repeatable measurement of forests is essential for understanding the Earth system. Terrestrial laser scanning can be a powerful tool for characterising forests. However, there are a number of issues that have yet to be resolved. Commercial laser scanners are optimised for measuring buildings and other hard targets. Vegetation canopies are complex and porous, confounding standard interpretation techniques. Commercial systems struggle with partial hits and cannot distinguish leaf from wood (Danson et al 2007). A new generation of terrestrial laser scanners, optimised for vegetation measurement, are in development. The Salford Advanced Laser Canopy Analyser (SALCA, Gaulton et al 2013) aims to overcome these issues using full-waveform analysis and two wavelengths (1064 nm and 1545 nm), allowing the characterisation of a porous canopy, the identification of leaf and wood and derivation of information on leaf biochemistry. Gaulton et al (2013) showed that SALCA is capable of measuring the Equivalent Water Thickness (EWT) of individual leaves in laboratory conditions. In this study, the method was applied to complete tree canopies. A controlled experiment simulating a small 'forest' of potted broadleaved (Tilia cordata) and coniferous trees (Pinus nigra) was established and groups subjected to different moisture stresses over a one month period. Trees were repeatedly scanned by SALCA and regular measurements were made of leaf EWT, stomatal conductance, chlorophyll content, spectral properties (using an ASD field spectroradiometer) and, for a limited number of trees, leaf area (by destructive
Periodically poled self-frequency-doubling green laser fabricated from Nd:Mg:LiNbO₃ single crystal.
Wang, Dong Zhou; Sun, De Hui; Kang, Xue Liang; Sang, Yuan Hua; Yan, Bo Xia; Liu, Hong; Bi, Yong
2015-07-13
Although a breakthrough in the fabrication of green laser diodes has occurred, the high costs associated with the difficulty of manufacture still present a great obstacle for its practical application. Another approach for producing a green laser, by combining a laser device and a nonlinear crystal, entails the fabrication of complex structures and exhibits unstable performance due to interface contact defects, thus limiting its application. In this work, we report the fabrication by domain engineering of high quality periodically poled LiNbO₃, co-doped with Nd³⁺ and Mg²⁺, which combines a laser medium and a high efficiency second harmonic conversion crystal into a single system that is designed to overcome the above problems. An 80 mW self-frequency doubling green laser was constructed for the first time from a periodically poled Nd:Mg:LiNbO₃ crystal of 16 mm in length. This crystal can be used for developing compact, stable, highly efficient mini-solid-state-lasers, which promise to have many applications in portable laser-based spectroscopy, photo-communications, terahertz wave generation, and laser displays.
Diffraction-limited 577 nm true-yellow laser by frequency doubling of a tapered diode laser
Christensen, Mathias; Vilera, Mariafernanda; Noordegraaf, Danny; Hansen, Anders K.; Buß, Thomas; Jensen, Ole B.; Skovgaard, Peter M. W.
2018-02-01
A wide range of laser medical treatments are based on coagulation of blood by absorption of the laser radiation. It has, therefore, always been a goal of these treatments to maximize the ratio of absorption in the blood to that in the surrounding tissue. For this purpose lasers at 577 nm are ideal since this wavelength is at the peak of the absorption in oxygenated hemoglobin. Furthermore, 577 nm has a lower absorption in melanin when compared to green wavelengths (515 - 532 nm), giving it an advantage when treating at greater penetration depth. Here we present a laser system based on frequency doubling of an 1154 nm Distributed Bragg Reflector (DBR) tapered diode laser, emitting 1.1 W of single frequency and diffraction limited yellow light at 577 nm, corresponding to a conversion efficiency of 30.5%. The frequency doubling is performed in a single pass configuration using a cascade of two bulk non-linear crystals. The system is power stabilized over 10 hours with a standard deviation of 0.13% and the relative intensity noise is measured to be 0.064 % rms.
Jung, Seo Jin; Choi, Young Jae; Kim, Na Na; Choi, Ji Yong; Kim, Bong-Seok; Choi, Cheol Young
2016-05-01
We tested the mitigating effects of melatonin injections or irradiation from green-wavelength light-emitting diodes (LEDs) on goldfish (Carassius auratus) exposed to thermal stress (high water temperature, 30 °C). The effects of the two treatments were assessed by measuring the expression and activity levels of the antioxidant enzymes, superoxide dismutase and catalase, plasma hydrogen peroxide, lipid hydroperoxide, and lysozyme. In addition, a comet assay was conducted to confirm that high water temperature damaged nuclear DNA. The expression and activity of the antioxidant enzymes, plasma hydrogen peroxide, and lipid hydroperoxide were significantly higher after exposure to high temperature and were significantly lower in fish that received melatonin or LED light than in those that received no mitigating treatment. Plasma lysozyme was significantly lower after exposure to high temperature and was significantly higher after exposure to melatonin or LED light. The comet assay revealed that thermal stress caused a great deal of damage to nuclear DNA; however, treatment with melatonin or green-wavelength LED light prevented a significant portion of this damage from occurring. These results indicate that, although high temperatures induce oxidative stress and reduce immune system strength in goldfish, both melatonin and green-wavelength LED light inhibit oxidative stress and boost the immune system. LED treatment increased the antioxidant and immune system activity more significantly than did melatonin treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.
Short-wavelength free-electron laser sources and science: a review
Seddon, E. A.; Clarke, J. A.; Dunning, D. J.; Masciovecchio, C.; Milne, C. J.; Parmigiani, F.; Rugg, D.; Spence, J. C. H.; Thompson, N. R.; Ueda, K.; Vinko, S. M.; Wark, J. S.; Wurth, W.
2017-11-01
This review is focused on free-electron lasers (FELs) in the hard to soft x-ray regime. The aim is to provide newcomers to the area with insights into: the basic physics of FELs, the qualities of the radiation they produce, the challenges of transmitting that radiation to end users and the diversity of current scientific applications. Initial consideration is given to FEL theory in order to provide the foundation for discussion of FEL output properties and the technical challenges of short-wavelength FELs. This is followed by an overview of existing x-ray FEL facilities, future facilities and FEL frontiers. To provide a context for information in the above sections, a detailed comparison of the photon pulse characteristics of FEL sources with those of other sources of high brightness x-rays is made. A brief summary of FEL beamline design and photon diagnostics then precedes an overview of FEL scientific applications. Recent highlights are covered in sections on structural biology, atomic and molecular physics, photochemistry, non-linear spectroscopy, shock physics, solid density plasmas. A short industrial perspective is also included to emphasise potential in this area. Dedicated to John M J Madey (1943-2016) and Rodolfo Bonifacio (1940-2016) whose perception, drive and perseverance paved the way for the realisation and development of short-wavelength free-electron lasers.
Polarimetric, Two-Color, Photon-Counting Laser Altimeter Measurements of Forest Canopy Structure
Harding, David J.; Dabney, Philip W.; Valett, Susan
2011-01-01
Laser altimeter measurements of forest stands with distinct structures and compositions have been acquired at 532 nm (green) and 1064 nm (near-infrared) wavelengths and parallel and perpendicular polarization states using the Slope Imaging Multi-polarization Photon Counting Lidar (SIMPL). The micropulse, single photon ranging measurement approach employed by SIMPL provides canopy structure measurements with high vertical and spatial resolution. Using a height distribution analysis method adapted from conventional, 1064 nm, full-waveform lidar remote sensing, the sensitivity of two parameters commonly used for above-ground biomass estimation are compared as a function of wavelength. The results for the height of median energy (HOME) and canopy cover are for the most part very similar, indicating biomass estimations using lidars operating at green and near-infrared wavelengths will yield comparable estimates. The expected detection of increasing depolarization with depth into the canopies due to volume multiple-scattering was not observed, possibly due to the small laser footprint and the small detector field of view used in the SIMPL instrument. The results of this work provide pathfinder information for NASA's ICESat-2 mission that will employ a 532 nm, micropulse, photon counting laser altimeter.
The use of an intermediate wavelength laser for alignment to inertial confinement fusion targets
International Nuclear Information System (INIS)
English, R.E. Jr.; Seppala, L.G.; Vann, C.S.; Bliss, E.S.
1995-01-01
The conceptual design of the National Ignition Facility (NIF) 192 beam laser incorporates a low-power alignment beam injected in the pinhole plane of the final spatial filter with a wave length intermediate between the 1053 mn laser output and the 351 mn frequency-converted beam that illuminates the target Choosing the specific wavelength for which the spatial filter plane is reimaged in the same target chamber plane as the frequency-converted main laser pulse, achieves optimum accuracy without the need for additional means to insure precise overlap between the two beams. Insertion of the alignment beam after the last laser amplifier also allows alignment to the target while the amplifiers are still cooling from a previous shot
Molecular Iodine Fluorescence Using a Green Helium-Neon Laser
Williamson, J. Charles
2011-01-01
Excitation of molecular iodine vapor with a green (543.4 nm) helium-neon laser produces a fluorescence spectrum that is well suited for the upper-level undergraduate physical chemistry laboratory. Application of standard evaluation techniques to the spectrum yields ground electronic-state molecular parameters in good agreement with literature…
Tattoo removal with the alexandrite laser: a clinical and histologic study
Fitzpatrick, Richard E.; Goldman, Mitchel P.
1993-07-01
The incident of tattoos in the United States is estimated to be in the range of 9 to 11% of the adult population. Various studies have shown that of these persons having tattoos, as many as 50 to 80% regret having gotten the tattoo and may desire tattoo removal. Previous treatment modalities have all used methods which require tissue destruction in order to remove the tattoo ink. The primary problems with use of these modalities has been the unpredictability of scarring. Also, residual tattoo pigment remaining after completion of the treatment process has been a problem. In response to these problems, the Q-switched lasers have been developed which target the tattoo pigments specifically rather than the tissue containing the tattoo pigment. The alexandrite laser (made by Candela Laser Corporation) has a wavelength of 755 nm and a pulse width of 100 nsec plus or minus 10 nsec. Reflectance studies have indicated that black, blue and green ink should absorb this wavelength relatively well, while red ink would not be expected to absorb this wavelength well. The mechanism of action of this laser is selective absorption of the laser energy by the tattoo pigment resulting in fragmentation of the pigment and then engulfment by tissue macrophages which remove the fragmented tattoo pigment. Preliminary studies using a Yucatan mini pig confirmed these expectations with black ink being easier to remove than blue and green, and red ink being minimally responsive. Higher fluences were more effective.
Temperature Characteristics of Monolithically Integrated Wavelength-Selectable Light Sources
International Nuclear Information System (INIS)
Han Liang-Shun; Zhu Hong-Liang; Zhang Can; Ma Li; Liang Song; Wang Wei
2013-01-01
The temperature characteristics of monolithically integrated wavelength-selectable light sources are experimentally investigated. The wavelength-selectable light sources consist of four distributed feedback (DFB) lasers, a multimode interferometer coupler, and a semiconductor optical amplifier. The oscillating wavelength of the DFB laser could be modulated by adjusting the device operating temperature. A wavelength range covering over 8.0nm is obtained with stable single-mode operation by selecting the appropriate laser and chip temperature. The thermal crosstalk caused by the lateral heat spreading between lasers operating simultaneously is evaluated by oscillating-wavelength shift. The thermal crosstalk approximately decreases exponentially as the increasing distance between lasers
International Nuclear Information System (INIS)
Blecker, Carlo R.; Hermann, Gerd M.
2009-01-01
Atomic absorption and coherent forward scattering spectrometry by using a near-infrared diode laser with and without Zeeman and wavelength modulation were carried out with graphite furnace electrothermal atomization. Analytical curves and limits of detection were compared. The magnetic field was modulated with 50 Hz, and the wavelength of the diode laser with 10 kHz. Coherent forward scattering was measured with crossed and slightly uncrossed polarizers. The results show that the detection limits of atomic absorption spectrometry are roughly the same as those of coherent forward scattering spectrometry with crossed polarizers. According to the theory with bright flicker noise limited laser sources the detection limits and linear ranges obtained with coherent forward scattering spectrometry with slightly uncrossed polarizers are significantly better than those obtained with crossed polarizers and with atomic absorption spectrometry. This is due to the fact that employing approaches of polarization spectroscopy reduce laser intensity fluctuations to their signal carried fractions
Bass, L S; Oz, M C; Libutti, S K; Treat, M R
1992-06-01
Attempts to improve the speed and patency of microvascular anastomosis with laser-assisted techniques have provided a modest reduction in operative time and comparable success rates. Using sutureless microvascular anastomoses, 30 end-to-end anastomoses were created in the rat carotid artery using the gallium-aluminum-arsenide diode laser (808 nm). Indocyanine green and fibrinogen were applied to enhance tissue absorption of the laser energy and strengthen the bond created. These were compared with previously reported welds using the THC:YAG laser (2150 nm). Mean welding times were 140 and 288 s, and mean bursting pressures immediately after welding were 515 and 400 mmHg for the diode and THC:YAG laser groups, respectively. Histologically, both lateral and vertical spread of thermal damage was limited. Since both lasers create welds of adequate initial strength without stay sutures and are faster and easier to use than existing systems, evaluation of long-term patency would be worthwhile.
Zhao, Gang; Tan, Wei; Hou, Jiajia; Qiu, Xiaodong; Ma, Weiguang; Li, Zhixin; Dong, Lei; Zhang, Lei; Yin, Wangbao; Xiao, Liantuan; Axner, Ove; Jia, Suotang
2016-01-25
A methodology for calibration-free wavelength modulation spectroscopy (CF-WMS) that is based upon an extensive empirical description of the wavelength-modulation frequency response (WMFR) of DFB laser is presented. An assessment of the WMFR of a DFB laser by the use of an etalon confirms that it consists of two parts: a 1st harmonic component with an amplitude that is linear with the sweep and a nonlinear 2nd harmonic component with a constant amplitude. Simulations show that, among the various factors that affect the line shape of a background-subtracted peak-normalized 2f signal, such as concentration, phase shifts between intensity modulation and frequency modulation, and WMFR, only the last factor has a decisive impact. Based on this and to avoid the impractical use of an etalon, a novel method to pre-determine the parameters of the WMFR by fitting to a background-subtracted peak-normalized 2f signal has been developed. The accuracy of the new scheme to determine the WMFR is demonstrated and compared with that of conventional methods in CF-WMS by detection of trace acetylene. The results show that the new method provides a four times smaller fitting error than the conventional methods and retrieves concentration more accurately.
International Nuclear Information System (INIS)
Yeh, Chien-Hung; Chow, Chi-Wai; Lu, Shao-Sheng
2014-01-01
In this work, we propose and demonstrate a multi-wavelength laser source produced by utilizing a C-band reflective semiconductor optical amplifier (RSOA) with a dual-ring fiber cavity. Here, the laser cavity consists of an RSOA, a 1 × 2 optical coupler, a 2 × 2 optical coupler and a polarization controller. As a result, thirteen to eighteen wavelengths around the L band could be generated simultaneously when the bias current of the C-band RSOA was driven at 30–70 mA. In addition, the output stabilities of the power and wavelength are also discussed. (paper)
Yeh, Chien-Hung; Chow, Chi-Wai; Lu, Shao-Sheng
2014-05-01
In this work, we propose and demonstrate a multi-wavelength laser source produced by utilizing a C-band reflective semiconductor optical amplifier (RSOA) with a dual-ring fiber cavity. Here, the laser cavity consists of an RSOA, a 1 × 2 optical coupler, a 2 × 2 optical coupler and a polarization controller. As a result, thirteen to eighteen wavelengths around the L band could be generated simultaneously when the bias current of the C-band RSOA was driven at 30-70 mA. In addition, the output stabilities of the power and wavelength are also discussed.
A Fabry-Pérot electro-optic sensing system using a drive-current-tuned wavelength laser diode.
Kuo, Wen-Kai; Wu, Pei-Yu; Lee, Chang-Ching
2010-05-01
A Fabry-Pérot enhanced electro-optic sensing system that utilizes a drive-current-tuned wavelength laser diode is presented. An electro-optic prober made of LiNbO(3) crystal with an asymmetric Fabry-Pérot cavity is used in this system. To lock the wavelength of the laser diode at resonant condition, a closed-loop power control scheme is proposed. Experiment results show that the system can keep the electro-optic prober at high sensitivity for a long working time when the closed-loop control function is on. If this function is off, the sensitivity may be fluctuated and only one-third of the best level in the worst case.
International Nuclear Information System (INIS)
Darwiche, S.; Benmansour, M.; Eliezer, N.; Morvan, D.
2010-01-01
The quantification of boron and other impurities in photovoltaic grade silicon was investigated using the LIBS technique with attention to the laser wavelength employed, temporal parameters, and the nature of the ambient gas. The laser wavelength was found to have a moderate effect on the performance of the process, while the type of purge gas and temporal parameters had a strong effect on the signal-to-background ratio (SBR) of the boron spectral emission, which was used to determine the boron concentration in silicon. The three parameters are not independent, meaning that for each different purge gas, different optimal temporal parameters are observed. Electron density was also calculated from Stark broadening of the 390.5 nm silicon emission line in order to better understand the different performances observed when using different gases and gating parameters. Calibration curves were made for boron measurement in silicon using certified standards with different purge gases while using the temporal parameters which had been optimized for that gas. By comparing the calibration curves, it was determined that argon is superior to helium or air for use as the analysis chamber purge gas with an UV laser.
CBET Experiments with Wavelength Shifting at the Nike Laser
Weaver, James; McKenty, P.; Bates, J.; Myatt, J.; Shaw, J.; Obenschain, K.; Oh, J.; Kehne, D.; Obenschain, S.; Lehmberg, R. H.; Tsung, F.; Schmitt, A. J.; Serlin, V.
2016-10-01
Studies conducted at NRL during 2015 searched for cross-beam energy transport (CBET) in small-scale plastic targets with strong gradients in planar, cylindrical, and spherical geometries. The targets were irradiated by two widely separated beam arrays in a geometry similar to polar direct drive. Data from these shots will be presented that show a lack of a clear CBET signature even with wavelength shifting of one set of beams. This poster will discuss the next campaign being planned, in part, with modelling codes developed at LLE. The next experiments will use a target configuration optimized to create stronger SBS growth. The primary path under consideration is to increase scale lengths 5-10x over the previous study by using exploding foils or low density foams. In addition to simulations, the presentation will also discuss improvements to the diagnostic suite and laser operations; for example, a new set of etalons will be available for the next campaign that should double the range of wavelength shifting between the two beam arrays. Work supported by DoE/NNSA.
Zhang, Yuxia; Yu, Haohai; Zhang, Huaijin; Di Lieto, Alberto; Tonelli, Mauro; Wang, Jiyang
2016-06-15
We demonstrate efficient laser-diode pumped multi-gigahertz (GHz) self-mode-locked praseodymium (Pr3+) visible lasers with broadband spectra from green to deep red for the first time to our knowledge. With a Pr3+-doped GdLiF4 crystal, stable self-mode-locked visible pulsed lasers at the wavelengths of 522 nm, 607 nm, 639 nm, and 720 nm have been obtained with the repetition rates of 2.8 GHz, 3.1 GHz, 3.1 GHz, and 3.0 GHz, respectively. The maximum output power was 612 mW with the slope efficiency of 46.9% at 639 nm. The mode-locking mechanism was theoretically analyzed. The stable second-harmonic mode-locking with doubled repetition frequency was also realized based on the Fabry-Perot effect formed in the laser cavity. In addition, we find that the polarization directions were turned with lasing wavelengths. This work may provide a new way for generating efficient ultrafast pulses with high- and changeable-repetition rates in the visible range.
Directory of Open Access Journals (Sweden)
Tai-Chieh Huang
2015-09-01
Full Text Available The laser-initiated thermal (optothermal switching of cholesteric liquid crystals (CLCs is characterized by using different azobenzene (Azo derivatives and laser wavelengths. Under 405-nm laser irradiation, Azo-doped CLCs undergo phase transition from cholesteric to isotropic. No cis-to-trans photoisomerization occurs when the 405-nm laser irradiation is blocked because only a single laser is used. The fast response of Azo-doped CLCs under the on–off switching of the 405-nm laser occurs because of the optothermal effect of the system. The 660-nm laser, which cannot be used as irradiation to generate the trans–cis photoisomerization of Azo, is used in Anthraquinone (AQ-Azo-doped CLCs to examine the optothermal effect of doped Azo. The results show that the LC-like Azo derivative bearing two methyl groups ortho to the Azo moiety (A4 can greatly lower the clearing temperature and generate large amount of heat in AQ-A4-doped CLCs.
A novel dual-wavelength laser stimulator to elicit transient and tonic nociceptive stimulation.
Dong, Xiaoxi; Liu, Tianjun; Wang, Han; Yang, Jichun; Chen, Zhuying; Hu, Yong; Li, Yingxin
2017-07-01
This study aimed to develop a new laser stimulator to elicit both transient and sustained heat stimulation with a dual-wavelength laser system as a tool for the investigation of both transient and tonic experimental models of pain. The laser stimulator used a 980-nm pulsed laser to generate transient heat stimulation and a 1940-nm continuous-wave (CW) laser to provide sustained heat stimulation. The laser with 980-nm wavelength can elicit transient pain with less thermal injury, while the 1940-nm CW laser can effectively stimulate both superficial and deep nociceptors to elicit tonic pain. A proportional integral-derivative (PID) temperature feedback control system was implemented to ensure constancy of temperature during heat stimulation. The performance of this stimulator was evaluated by in vitro and in vivo animal experiments. In vitro experiments on totally 120 specimens fresh pig skin included transient heat stimulation by 980-nm laser (1.5 J, 10 ms), sustained heat stimulation by 1940-nm laser (50-55 °C temperature control mode or 1.5 W, 5 min continuous power supply), and the combination of transient/sustained heat stimulation by dual lasers (1.5 J, 10 ms, 980-nm pulse laser, and 1940-nm laser with 50-55 °C temperature control mode). Hemoglobin brushing and wind-cooling methods were tested to find better stimulation model. A classic tail-flick latency (TFL) experiment with 20 Wistar rats was used to evaluate the in vivo efficacy of transient and tonic pain stimulation with 15 J, 100 ms 980-nm single laser pulse, and 1.5 W constant 1940-nm laser power. Ideal stimulation parameters to generate transient pain were found to be a 26.6 °C peak temperature rise and 0.67 s pain duration. In our model of tonic pain, 5 min of tonic stimulation produced a temperature change of 53.7 ± 1.3 °C with 1.6 ± 0.2% variation. When the transient and tonic stimulation protocols were combined, no significant difference was observed depending on the order
Wavelength beam combining of a 980-nm tapered diode laser bar in an external cavity
DEFF Research Database (Denmark)
Vijayakumar, Deepak; Jensen, Ole Bjarlin; Thestrup Nielsen, Birgitte
2010-01-01
solution for preserving the beam quality of the bar in the range of that of a single emitter and at the same time, enabling the power scaling. We report spectral beam combining applied to a 12 emitter tapered laser bar at 980 nm. The external cavity has been designed for a wavelength separation of 4.0 nm......High power diode lasers are used in a large number of applications. A limiting factor for more widespread use of broad area lasers is the poor beam quality. Gain guided tapered diode lasers are ideal candidates for industrial applications that demands watt level output power with good beam quality...
Stefan, V. Alexander
2014-03-01
A novel mechanism of importance for the transfusion medicine[2] is proposed. The interaction of ultrashort wavelength multilaser beams with the flowing blood thin films can lead to a conversion of blood types A, B, and AB into O type.[3] The stripping away of antigens is done by the scanning-multiple-lasers of a high repetition rate in the blue-purple frequency domain. The guiding-lasers are in the red-green frequency domain. The laser force, (parametric interaction with the antigen eigen-oscillation),[4] upon the antigen protein molecule must exceed its weight. Supported by Nikola Tesla Labs, La Jolla, CA.
International Nuclear Information System (INIS)
McConnell, Gail; Riis, Erling
2004-01-01
We report on a novel and compact reliable laser source capable of short-wavelength two-photon laser scanning fluorescence microscopy based on soliton self-frequency shift effects in photonic crystal fibre. We demonstrate the function of the system by performing two-photon microscopy of smooth muscle cells and cardiac myocytes from the rat pulmonary vein and Chinese hamster ovary cells loaded with the fluorescent calcium indicator fura-2/AM
Guo, Sanwei; Müller, Georg; Bonkat, Gernot; Püschel, Heike; Gasser, Thomas; Bachmann, Alexander; Rieken, Malte
2015-04-01
Laser vaporization of the prostate is one of the alternatives to transurethral resection of the prostate. Short-term studies report a comparable outcome after laser vaporization with the 532 nm 120-W GreenLight high-performance system (HPS) laser and the 980 nm 200 W high-intensity diode (diode) laser. In this study, we analyzed the intermediate-term results of both techniques. From January 2007 to January 2008, 112 consecutive patients with symptomatic benign prostate enlargement were nonrandomly assigned to treatment with the GreenLight laser or the diode laser. Perioperative parameters, postoperative functional outcome, complications, and the reoperation rate at 3 years were analyzed. Improvement of voiding symptoms (International Prostate Symptom Score, quality-of-life) and micturition parameters (maximum flow rate, postvoid residual volume) showed no significant difference between the HPS group and the diode group. A significantly higher reoperation rate was observed in the diode group in comparison to the HPS group (37.5% vs 8.9%, p=0.0003) due to obstructive necrotic tissue (16.1% vs 0%, p=0.0018), bladder neck stricture (16.1% vs 1.8%, p=0.008), and persisting or recurrent adenoma (5.4% vs 7.1%, p=0.70), respectively. Both lasers lead to comparable improvement of voiding parameters and micturition symptoms. Treatment with the 200 W diode laser led to a significantly higher reoperation rate, which might be attributed to a higher degree of coagulation necrosis. Thus, a careful clinical application of this diode laser type is warranted.
International Nuclear Information System (INIS)
Chambonneau, Maxime
2014-01-01
In this thesis, laser-induced damage phenomenon on the surface of fused silica components is investigated in the nanosecond regime. This phenomenon consists in an irreversible modification of the material. In the nanosecond regime, laser damage is tightly correlated to the presence of non-detectable precursor defects which are a consequence of the synthesis and the polishing of the components. In this thesis, we investigate laser damage in a multiple wavelengths configuration. In order to better understand this phenomenon in these conditions of irradiation, three studies are conducted. The first one focuses on damage initiation. The results obtained in the single wavelength configurations highlight a coupling in the multiple wavelengths one. A comparison between the experiments and a model developed during this thesis enables us to improve the knowledge of the fundamental processes involved during this damage phase. Then, we show that post mortem characterizations of damage morphology coupled to an accurate metrology allow us to understand both the nature and also the chronology of the physical mechanisms involved during damage formation. The proposed theoretical scenario is confirmed through various experiments. Finally, we study damage growth in both the single and the multiple wavelengths cases. Once again, this last configuration highlights a coupling between the wavelengths. We show the necessity to account for the spatial characteristics of the laser beams during a growth session. (author) [fr
Directory of Open Access Journals (Sweden)
M. L. Belov
2017-01-01
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
Muñoz, P.; García-Olcina, R.; Doménech, J.D.; Rius, M.; Capmany, J.; Chen, L.R.; Habib, C.; Leijtens, X.J.M.; Vries, de T.; Heck, M.J.R.; Augustin, L.M.; Nötzel, R.; Robbins, D.J.
2010-01-01
In this paper, a multi-wavelength laser monolithically integrated on InP is presented. A linear laser cavity is built between two integrated Sagnac loop reflectors, with an Arrayed Waveguide Grating (AWG) as frequency selective device, and Semiconductor Optical Amplifiers (SOA) as gain sections. The
International Nuclear Information System (INIS)
Tuchina, E S; Tuchin, Valerii V; Khlebtsov, B N; Khlebtsov, Nikolai G
2011-01-01
The effect of IR laser radiation (λ = 805 - 808 nm) on the bacteria of the strain Staphylococcus aureus 209 P, incubated in indocyanine green solutions, is studied, as well as that of colloid gold nanoshells, nanocages and their conjugates with indocyanine green. It is found that the S. aureus 209 P cells are equally subjected to the IR laser radiation (λ = 805 nm) after preliminary sensitisation with indocyanine green and gold nanoparticles separately and with conjugates of nanoparticles and indocyanine green. The enhancement of photodynamic and photothermal effects by 5 % is observed after 30 min of laser illumination (λ = 808 nm) of bacteria, treated with conjugates of indocyanine green and nanocages. (optical technologies in biophysics and medicine)
DEFF Research Database (Denmark)
Sumpf, Bernd; Maiwald, Martin; Müller, André
2012-01-01
Reliability tests for wavelength-stabilized compact diode laser systems emitting at 671 nm are presented. The devices were mounted on microoptical benches with the dimensions of 13 mm $\\times\\,$4 mm. Reflecting Bragg gratings were used for wavelength stabilization and emission width narrowing...
Simple approach to three-color two-photon microscopy by a fiber-optic wavelength convertor.
Li, Kuen-Che; Huang, Lynn L H; Liang, Jhih-Hao; Chan, Ming-Che
2016-11-01
A simple approach to multi-color two-photon microscopy of the red, green, and blue fluorescent indicators was reported based on an ultra-compact 1.03-μm femtosecond laser and a nonlinear fiber. Inside the nonlinear fiber, the 1.03-μm laser pulses were simultaneously blue-shifted to 0.6~0.8 μm and red-shifted to 1.2~1.4 μm region by the Cherenkov radiation and fiber Raman gain effects. The wavelength-shifted 0.6~0.8 μm and 1.2~1.4 μm radiations were co-propagated with the residual non-converted 1.03-μm pulses inside the same nonlinear fiber to form a fiber-output three-color femtosecond source. The application of the multi-wavelength sources on multi-color two-photon fluorescence microscopy were also demonstrated. Overall, due to simple system configuration, convenient wavelength conversion, easy wavelength tunability within the entire 0.7~1.35 μm bio-penetration window and less requirement for high power and bulky light sources, the simple approach to multi-color two-photon microscopy could be widely applicable as an easily implemented and excellent research tool for future biomedical and possibly even clinical applications.
International Nuclear Information System (INIS)
Fabro, R.; Faral, B.; Virmont, J.; Pepin, H.; Cottet, F.; Romain, J.P.
1986-01-01
A 9 μm thick aluminium foil is accelerated to a velocity of about 160 km/s by a laser of 0.26 μm wavelength and intensity of 10 15 W/cm 2 and collides with an aluminium impact foil. The measurement of the velocity of the induced shock wave in the impact foil, using a step method at the rear of the impact foil, gives pressures in the multi-hundred megabar range. The dynamics and constraints of this shock wave are presented and the effect of X-ray preheating, which can be important at this laser wavelength, is discussed. (author)
Energy Technology Data Exchange (ETDEWEB)
Fabro, R.; Faral, B.; Virmont, J.; Pepin, H.; Cottet, F.; Romain, J.P.
A 9 ..mu..m thick aluminium foil is accelerated to a velocity of about 160 km/s by a laser of 0.26 ..mu..m wavelength and intensity of 10/sup 15/ W/cm/sup 2/ and collides with an aluminium impact foil. The measurement of the velocity of the induced shock wave in the impact foil, using a step method at the rear of the impact foil, gives pressures in the multi-hundred megabar range. The dynamics and constraints of this shock wave are presented and the effect of X-ray preheating, which can be important at this laser wavelength, is discussed.
Theoretical modelling of dual-wavelength pumped Yb3+–Tm3+ co-doped silica fibre laser
International Nuclear Information System (INIS)
Fu, Yuqing; Chen, Jianguo
2010-01-01
Numerical simulations have, for the first time to our knowledge, been carried out to characterize the Yb 3+ –Tm 3+ co-doped silica fibre laser (YTFL), defined by a fibre grating and an end mirror, by using the rate equations, which take into consideration both the energy transfer processes from Yb 3+ to Tm 3+ ions and the cross-relaxation processes among different Tm 3+ ions. A dual-wavelength pumping scheme with one at 805 nm and the other at 975 nm is used to pump the YTFL. We have investigated the wavelength-dependent output power of the YTFL, from 1750 to 2200 nm, which takes its maximum output power at ∼ 1800 nm. The effect of the cross-relaxation processes in the Tm 3+ -doped silica fibre laser has been studied. The results indicate that these processes are beneficial to the laser and should be considered in the theoretical modelling. The influence of the Yb 3+ concentration on the characteristics of the YTFL has also been analysed and the results show that Yb 3+ dopants can improve the output power and slope efficiency of the laser
Laser Shock Processing of 6061-T6 Al alloy with 1064 nm and 532 nm wavelengths
International Nuclear Information System (INIS)
Gomez-Rosas, G.; Rubio-Gonzalez, C.; Ocana, J.L.; Molpeceres, C.; Porro, J.A.; Morales, M.; Casillas, F.J.
2010-01-01
Laser Shock Processing (LSP) has been proposed as a competitive alternative technology to classical treatments for improving fatigue and wear resistance of metals. We present a configuration and results in the LSP concept for metal surface treatments in underwater laser irradiation at 532 nm and 1064 nm. The purpose of the work is to compare the effect of both wavelengths on the same material. A convergent lens is used to deliver 1.2 J/pulse (1064 nm) and 0.9 J/pulse (532 nm) in a 8 ns laser FWHM pulse produced by 10 Hz Q-switched Nd:YAG laser with spots of a 1.5 mm in diameter moving forward along the work piece. A LSP configuration with experimental results using a pulse density of 2500 pulses/cm 2 and 5000 pulses/cm 2 in 6061-T6 aluminum samples are presented. High level compressive residual stresses are produced using both wavelengths. It has been shown that surface residual stress level is comparable to that achieved by conventional shot peening, but with greater depths. This method can be applied to surface treatment of final metal products.
Xiong, Gang; Li, Shuiqing; Tse, Stephen D.
2018-02-01
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.
Directory of Open Access Journals (Sweden)
Ashish Sharma
2013-01-01
Full Text Available Background: Neodymium: YAG (Nd: YAG laser and argon laser has been used to treat premacular hemorrhage either alone or rarely in combination. Materials and Methods: We describe a new technique of treating premacular hemorrhage by performing hyaloidotomy using a combination of argon green-Nd: YAG laser. We utilized subthreshold energy levels of Nd: YAG laser of 2.0 mJ as compared to the normal recommendation of 3.6-50 mJ. Results and Conclusions: This technique is easy, effective, and safe to manage premacular hemorrhage. The principle behind this combined laser treatment was to make the internal limiting membrane (ILM taut by initial exposure to argon green laser, which allowed us to employ the subthreshold energy levels of Nd: YAG laser. We would like to assess the role of this combined treatment modality in comparison to other modalities, including solitary laser therapy in the management of premacular hemorrhage by performing a prospective, randomized long-term study.
International Nuclear Information System (INIS)
Liu, X M; Lin, A; Zhao, W; Lu, K Q; Wang, Y S; Zhang, T Y; Chung, Y
2008-01-01
We have proposed a novel multi-wavelength erbium-doped fiber laser by using two polarization controllers and a sampled chirped fiber Bragg grating(SC-FBG). On the assistance of SC-FBG, the proposed fiber lasers with excellent stability and uniformity are tunable and switchable by adjusting the polarization controllers. Our laser can stably lase two waves and up to eight waves simultaneously at room temperature
Wavelength Selection For Laser Raman Spectroscopy of Putative Martian Habitats and Biomolecules
Wynn-Williams, D. D.; Newton, E. M. G.; Edwards, H. G. M.
Pigments are key potential biomarkers for any former life on Mars because of the selective pressure of solar radiation on any biological system that could have evolved at its surface. We have found that the near -Infrared laser Raman spectrometer available to use was eminently suitable for diagnostic analysis of pigments because of their minimal autofluorescence at its 1064 nm excitation wav elength. However, we have now evaluated a diverse range of excitation wavelengths to confirm this choice, to ensure that we have the best technique to seek for pigments and their derivatives from any former surface life on Mars. The Raman is weak relative to fluorescence, which results in elevated baseline and concurrent swamping of Raman bands. We confirm the molecular information available from near-IR FT Raman spectra for two highly pigmented UV-tolerant epilithic Antarctic lichens (Acarospora chlorop hana and Caloplaca saxicola) from Victoria Land, a whole endolithic microbial community and endolithic cyanobacterium Chroococcidiopsis from within translucent sandstone of the Trans -Antarctic Mountains, and the free- living cyanobacterium Nostoc commune from Alexander Island, Antarctic Peninsula region. We also show that much of the information we require on biomolecules is not evident from lasers of shorter wavelengths. A miniature 1064 nm Raman spectrometer with an In-Ga-As detector sensitive to IR is being developed by Montana State University (now existing as a prototype) as the prime instrument for a proposed UK-led Mars rover mission (Vanguard). Preliminary spectra from this system confirm the suitability of the near-IR laser.
Internal structure of laser supported detonation waves by two-wavelength Mach-Zehnder interferometer
International Nuclear Information System (INIS)
Shimamura, Kohei; Kawamura, Koichi; Fukuda, Akio; Wang Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya; Hatai, Keigo; Fukui, Akihiro; Arakawa, Yoshihiro
2011-01-01
Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density n e and the electron temperature T e profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO 2 laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of n e and T e were, respectively, about 2 x 10 24 m -3 and 30 000 K, during the LSD regime. The temporal variation of the laser absorption coefficient profile estimated from the measured properties reveals that the laser energy was absorbed perfectly in a thin layer behind the shock wave during the LSD regime, as predicted by Raizer's LSD model. However, the absorption layer was much thinner than a plasma layer, the situation of which was not considered in Raizer's model. The measured n e at the shock front was not zero while the LSD was supported, which implies that the precursor electrons exist ahead of the shock wave.
International Nuclear Information System (INIS)
Downer, M.C.
1996-01-01
The Laser Sources working group concerned itself with recent advances in and future requirements for the development of laser sources relevant to high-energy physics (HEP) colliders, small scale accelerators, and the generation of short wave-length radiation. We heavily emphasized pulsed terawatt peak power laser sources for several reasons. First, their development over the past five years has been rapid and multi-faceted, and has made relativistic light intensity available to the advanced accelerator community, as well as the wider physics community, for the first time. Secondly, they have strongly impacted plasma-based accelerator research over the past two years, producing the first experimental demonstrations of the laser wakefield accelerator (LWFA) in both its resonantly-driven and self-modulated forms. Thirdly, their average power and wall-plug efficiency currently fall well short of projected requirements for future accelerators and other high average power applications, but show considerable promise for improving substantially over the next few years. A review of this rapidly emerging laser technology in the context of advanced accelerator research is therefore timely
Castellano, A.; Cerutti, L.; Rodriguez, J. B.; Narcy, G.; Garreau, A.; Lelarge, F.; Tournié, E.
2017-06-01
We report on electrically pumped GaSb-based laser diodes monolithically grown on Si and operating in a continuous wave (cw) in the telecom wavelength range. The laser structures were grown by molecular-beam epitaxy on 6°-off (001) substrates. The devices were processed in coplanar contact geometry. 100 μm × 1 mm laser diodes exhibited a threshold current density of 1 kA/cm-2 measured under pulsed operation at 20 °C. CW operation was achieved up to 35 °C with 10 μm × 1 mm diodes. The output power at 20 °C was around 3 mW/uncoated facet, and the cw emission wavelength 1.59 μm, in the C/L-band of telecom systems.
Directory of Open Access Journals (Sweden)
A. Castellano
2017-06-01
Full Text Available We report on electrically pumped GaSb-based laser diodes monolithically grown on Si and operating in a continuous wave (cw in the telecom wavelength range. The laser structures were grown by molecular-beam epitaxy on 6°-off (001 substrates. The devices were processed in coplanar contact geometry. 100 μm × 1 mm laser diodes exhibited a threshold current density of 1 kA/cm−2 measured under pulsed operation at 20 °C. CW operation was achieved up to 35 °C with 10 μm × 1 mm diodes. The output power at 20 °C was around 3 mW/uncoated facet, and the cw emission wavelength 1.59 μm, in the C/L-band of telecom systems.
Zheng, Yujin; Sekine, Takashi; Kurita, Takashi; Kato, Yoshinori; Kawashima, Toshiyuki
2018-03-01
We demonstrate continuous-wave dual-wavelength operation of a broad-area distributed feedback (DFB) laser diode with a single external-cavity configuration. This high-power DFB laser has a narrow bandwidth (current and temperature ranges.
Continuous-wave single-frequency laser with dual wavelength at 1064 and 532 nm.
Zhang, Chenwei; Lu, Huadong; Yin, Qiwei; Su, Jing
2014-10-01
A continuous-wave high-power single-frequency laser with dual-wavelength output at 1064 and 532 nm is presented. The dependencies of the output power on the transmission of the output coupler and the phase-matching temperature of the LiB(3)O(5) (LBO) crystal are studied. An output coupler with transmission of 19% is used, and the temperature of LBO is controlled to the optimal phase-matching temperature of 422 K; measured maximal output powers of 33.7 W at 1064 nm and of 1.13 W at 532 nm are obtained with optical-optical conversion efficiency of 45.6%. The laser can be single-frequency operated stably and mode-hop-free, and the measured frequency drift is less than 15 MHz in 1 min. The measured Mx2 and My2 for the 1064 nm laser are 1.06 and 1.09, respectively. The measured Mx2 and My2 for the 532 nm laser are 1.12 and 1.11, respectively.
International Nuclear Information System (INIS)
Luo, A-P; Luo, Z-C; Xu, W-C; Dvoyrin, V V; Mashinsky, V M; Dianov, E M
2011-01-01
We demonstrate a tunable and switchable dual-wavelength passively mode-locked Bi-doped all-fiber ring laser by using nonlinear polarization rotation (NPR) technique. Exploiting the spectral filtering effect caused by the combination of the polarizer and intracavity birefringence, the wavelength separation of dual-wavelength mode-locked pulses can be flexibly tuned between 2.38 and 20.45 nm. Taking the advantage of NPR-induced intensity-dependent loss to suppress the mode competition, the stable dual-wavelength pulses output is obtained at room temperature. Moreover, the dual-wavelength switchable operation is achieved by simply rotating the polarization controllers (PCs)
Sub-wavelength patterning of organic monolayers via nonlinear processing with continuous-wave lasers
Energy Technology Data Exchange (ETDEWEB)
Mathieu, Mareike; Hartmann, Nils, E-mail: nils.hartmann@uni-due.de [Fakultaet fuer Chemie, Universitaet Duisburg-Essen, 45117 Essen (Germany); CeNIDE-Center for Nanointegration Duisburg-Essen, 47048 Duisburg (Germany); NETZ-NanoEnergieTechnikZentrum, 47048 Duisburg (Germany)
2010-12-15
In recent years, nonlinear processing with continuous-wave lasers has been demonstrated to be a facile means of rapid nanopatterning of organic monolayers down to the sub-100 nm range. In this study, we report on laser patterning of thiol-based organic monolayers with sub-wavelength resolution. Au-coated silicon substrates are functionalized with 1-hexadecanethiol. Irradiation with a focused beam of an Ar{sup +} laser operating at {lambda}=514 nm allows one to locally remove the monolayer. Subsequently, the patterns are transferred into the Au film via selective etching in a ferri-/ferrocyanide solution. Despite a 1/e{sup 2} spot diameter of about 2.8 {mu}m, structures with lateral dimensions down to 250 nm are fabricated. The underlying nonlinear dependence of the patterning process on laser intensity is traced back to the interplay between the laser-induced transient local temperature rise and the thermally activated desorption of the thiol molecules. A simple thermokinetic analysis of the data allows us to determine the effective kinetic parameters. These results complement our previous work on photothermal laser patterning of ultrathin organic coatings, such as silane-based organic monolayers, organo/silicon interfaces and supported membranes. A general introduction to nonlinear laser processing of organic monolayers is presented.
Energy Technology Data Exchange (ETDEWEB)
Torrent, F.; Lavisse, L. [Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université de Bourgogne, 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex (France); Berger, P. [CEA/DSM/IRAMIS/SIS2M, CEA-Saclay, F-91191 Gif sur Yvette (France); SIS2M, UMR CEA-CNRS 3299, CEA-Saclay, F-91191 Gif sur Yvette (France); Jouvard, J.-M.; Andrzejewski, H.; Pillon, G.; Bourgeois, S.; Marco de Lucas, M.C. [Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université de Bourgogne, 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex (France)
2013-08-01
We studied in this work the influence of the wavelength (532 vs. 1064 nm) on the insertion of nitrogen in titanium targets by surface laser treatments in air. The laser pulses were of 5 ns and the irradiance was lower than 25 × 10{sup 12} W/m{sup 2}. Results obtained using a frequency-doubled Nd:YAG laser at 532 nm were compared with those previously reported for laser treatments at 1064 nm. Nuclear reaction analysis and micro-Raman spectroscopy were used for determining the composition and the structure of the surface layers, respectively. Results showed the lower efficiency of irradiation at 532 nm for nitrogen insertion, which is possible only above threshold conditions depending on both the laser irradiance and the number of cumulated impacts per point. This was explained as being due to a higher ablative effect in the visible range. The insertion of oxygen giving rise to the growth of titanium oxynitrides was also discussed.
Short wavelength FELs using the SLAC linac
International Nuclear Information System (INIS)
Winick, H.; Bane, K.; Boyce, R.
1993-08-01
Recent technological developments have opened the possibility to construct a device which we call a Linac Coherent Light Source (LCLS); a fourth generation light source, with brightness, coherence, and peak power far exceeding other sources. Operating on the principle of the free electron laser (FEL), the LCLS would extend the range of FEL operation to much aborter wavelength than the 240 mn that has so far been reached. We report the results of studies of the use of the SLAC linac to drive an LCLS at wavelengths from about 3-100 nm initially and possibly even shorter wavelengths in the future. Lasing would be achieved in a single pass of a low emittance, high peak current, high energy electron beam through a long undulator. Most present FELs use an optical cavity to build up the intensity of the light to achieve lasing action in a low gain oscillator configuration. By eliminating the optical cavity, which is difficult to make at short wavelengths, laser action can be extended to shorter wavelengths by Self-Amplified-Spontaneous-Emission (SASE), or by harmonic generation from a longer wavelength seed laser. Short wavelength, single pass lasers have been extensively studied at several laboratories and at recent workshops
Packaging and testing of multi-wavelength DFB laser array using REC technology
Ni, Yi; Kong, Xuan; Gu, Xiaofeng; Chen, Xiangfei; Zheng, Guanghui; Luan, Jia
2014-02-01
Packaging of distributed feedback (DFB) laser array based on reconstruction-equivalent-chirp (REC) technology is a bridge from chip to system, and influences the practical process of REC chip. In this paper, DFB laser arrays of 4-channel @1310 nm and 8-channel @1550 nm are packaged. Our experimental results show that both these laser arrays have uniform wavelength spacing and larger than 35 dB average Side Mode Suppression Ratio (SMSR). When I=35 mA, we obtain the total output power of 1 mW for 4-channel @1310 nm, and 227 μw for 8-channel @1550 nm respectively. The high frequency characteristics of the packaged chips are also obtained, and the requirements for 4×10 G or even 8×10 G systems can be reached. Our results demonstrate the practical and low cost performance of REC technology and indicate its potential in the future fiber-to-the-home (FTTH) application.
Witte, U.; Traub, M.; Di Meo, A.; Hamann, M.; Rubel, D.; Hengesbach, S.; Hoffmann, D.
2016-03-01
We present a compact, modular and cross talk free approach for dense wavelength division multiplexing of high power diode lasers based on ultra-steep dielectric filters. The mini bars consist of 5 narrow stripe broad area emitters with a beam parameter product in the range of 2 mm mrad and a wavelength spacing of 2.5 nm between 2 adjacent emitters. Experimental results for fiber coupling (35 μm core diameter, NA < 0.2) of internally and externally stabilized diode lasers are presented. Optical losses are analyzed and alternative optical designs to overcome the current limitations of the setup are discussed.
Laser ultrasonics for bulk-density distribution measurement on green ceramic tiles
Revel, G. M.; Cavuto, A.; Pandarese, G.
2016-10-01
In this paper a Laser Ultrasonics (LUT) system is developed and applied to measure bulk density distribution of green ceramic tiles, which are porous materials with low heat conductivity. Bulk density of green ceramic bodies is a fundamental parameter to be kept under control in the industrial production of ceramic tiles. The LUT system proposed is based on a Nd:YAG pulsed laser for excitation and an air-coupled electro-capacitive transducer for detection. The paper reports experimental apparent bulk-density measurements on white ceramic bodies after a calibration procedures. The performances observed are better than those previously achieved by authors using air-coupled ultrasonic probes for both emission and detection, allowing to reduce average uncertainty down to about ±6 kg/m3 (±0.3%), thanks to the increase in excitation efficiency and lateral resolution, while maintaining potential flexibility for on-line application. The laser ultrasonic procedure proposed is available for both on-line and off-line application. In this last case it is possible to obtain bulk density maps with high spatial resolution by a 2D scan without interrupting the production process.
International Nuclear Information System (INIS)
Cantrell, C.D.; Carbone, R.J.
1977-01-01
An infrared laser system and method for isotope separation may comprise a molecular gas laser oscillator to produce a laser beam at a first wavelength, Raman spin flip means for shifting the laser to a second wavelength, a molecular gas laser amplifier to amplify said second wavelength laser beam to high power, and optical means for directing the second wavelength, high power laser beam against a desired isotope for selective excitation thereof in a mixture with other isotopes. The optical means may include a medium which shifts the second wavelength high power laser beam to a third wavelength, high power laser beam at a wavelength coincidental with a corresponding vibrational state of said isotope and which is different from vibrational states of other isotopes in the gas mixture
De Jesus, Joel
The ZnCdMgSe family of II-VI materials has unique and promising characteristics that may be useful in practical applications. For example they can be grown lattice matched to InP substrates with lattice matched bandgaps that span from 2.1 to 3.5 eV, they can be successfully doped n-type, have a large conduction band offset (CBO) with no intervalley scattering present when strained, they have lower average phonon energies, and the InP lattice constant lies in the middle of the ZnSe and CdSe binaries compounds giving room to experiment with tensile and compressive stress. However they have not been studied in detail for use in practical devices. Here we have identified two types of devices that are being currently developed that benefit from the ZnCdMgSe-based material properties. These are the intersubband (ISB) quantum cascade (QC) detectors and optically pumped semiconductor lasers that emit in the visible range. The paucity for semiconductor lasers operating in the green-orange portion of the visible spectrum can be easily overcome with the ZnCdMgSe materials system developed in our research. The non-strain limited, large CBO available allows to expand the operating wavelength of ISB devices providing shorter and longer wavelengths than the currently commercially available devices. This property can also be exploited to develop broadband room temperature operation ISB detectors. The work presented here focused first on using the ZnCdMgSe-based material properties and parameter to understand and predict the interband and intersubband transitions of its heterostructures. We did this by studying an active region of a QC device by contactless electroreflectance, photoluminescence, FTIR transmittance and correlating the measurements to the quantum well structure by transfer matrix modeling. Then we worked on optimizing the ZnCdMgSe material heterostructures quality by studying the effects of growth interruptions on their optical and optoelectronic properties of
Wavelengths of the Ni-like 4d1S0 - 4p1P1 x-ray laser line
International Nuclear Information System (INIS)
Li, Y.; Nilsen, J.; Dunn, J.; Osterheld, A.L.; Ryabtsev, A.; Churilov, S.
1998-01-01
We measure the wavelengths of the Ni-like 3d 9 4d 1 S 0 - 3d 9 4p 1 P 1 x-ray laser line in several low-Z Ni-like ions ranging from Y (Z=39) to Cd (Z=48). These wavelengths are compared with optimized level calculations using a multiconfiguration Dirac-Fock code. With the help of these results, we identify this line to very high accuracy in nonlasing plasmas from As (Z=33) to Mo (Z=42). Accurate values of these wavelengths are essential for performing plasma imaging and interferometry experiments with multilayer optics that use the x-ray laser to backlight other plasmas. These results also provide important atomic data that are currently missing about the energy of the 4d 1 S 0 level in the NiI sequence. copyright 1998 The American Physical Society
Interference with a quantum dot single-photon source and a laser at telecom wavelength
Energy Technology Data Exchange (ETDEWEB)
Felle, M. [Toshiba Research Europe Limited, Cambridge Research Laboratory, 208 Cambridge Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Centre for Advanced Photonics and Electronics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Huwer, J., E-mail: jan.huwer@crl.toshiba.co.uk; Stevenson, R. M.; Skiba-Szymanska, J.; Ward, M. B.; Shields, A. J. [Toshiba Research Europe Limited, Cambridge Research Laboratory, 208 Cambridge Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Farrer, I.; Ritchie, D. A. [Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Penty, R. V. [Centre for Advanced Photonics and Electronics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0FA (United Kingdom)
2015-09-28
The interference of photons emitted by dissimilar sources is an essential requirement for a wide range of photonic quantum information applications. Many of these applications are in quantum communications and need to operate at standard telecommunication wavelengths to minimize the impact of photon losses and be compatible with existing infrastructure. Here, we demonstrate for the first time the quantum interference of telecom-wavelength photons from an InAs/GaAs quantum dot single-photon source and a laser; an important step towards such applications. The results are in good agreement with a theoretical model, indicating a high degree of indistinguishability for the interfering photons.
Interference with a quantum dot single-photon source and a laser at telecom wavelength
International Nuclear Information System (INIS)
Felle, M.; Huwer, J.; Stevenson, R. M.; Skiba-Szymanska, J.; Ward, M. B.; Shields, A. J.; Farrer, I.; Ritchie, D. A.; Penty, R. V.
2015-01-01
The interference of photons emitted by dissimilar sources is an essential requirement for a wide range of photonic quantum information applications. Many of these applications are in quantum communications and need to operate at standard telecommunication wavelengths to minimize the impact of photon losses and be compatible with existing infrastructure. Here, we demonstrate for the first time the quantum interference of telecom-wavelength photons from an InAs/GaAs quantum dot single-photon source and a laser; an important step towards such applications. The results are in good agreement with a theoretical model, indicating a high degree of indistinguishability for the interfering photons
Laser inactivation of periodontal bacteria using photosensitizing dyes
Golding, Paul S.; Maddocks, L.; King, Terence A.; Drucker, D. B.
1996-12-01
We demonstrate the killing of the oral bacteria Prevotella nigrescens using a photosensitizer and light from a 10 Hz, frequency doubled, Q-switched Nd:YAG pumped dye laser, with modified oscillator to increase output power. This system produced light at wavelengths close to 620 nm, the absorption maximum of the photosensitizing agent, malachite green isothiocyanate, a wavelength that is not significantly absorbed by tissue. A bacterial reduction of 97.5 percent was achieved at an energy density of 0.67 J/cm2 and exposure times of 300 seconds.
Liu, Wei; Li, Chen; Zhang, Zhigang; Kärtner, Franz X; Chang, Guoqing
2016-07-11
We propose and demonstrate a new approach to implement a wavelength-tunable ultrafast fiber laser source suitable for multiphoton microscopy. We employ fiber-optic nonlinearities to broaden a narrowband optical spectrum generated by an Yb-fiber laser system and then use optical bandpass filters to select the leftmost or rightmost spectral lobes from the broadened spectrum. Detailed numerical modeling shows that self-phase modulation dominates the spectral broadening, self-steepening tends to blue shift the broadened spectrum, and stimulated Raman scattering is minimal. We also find that optical wave breaking caused by fiber dispersion slows down the shift of the leftmost/rightmost spectral lobes and therefore limits the wavelength tuning range of the filtered spectra. We show both numerically and experimentally that shortening the fiber used for spectral broadening while increasing the input pulse energy can overcome this dispersion-induced limitation; as a result, the filtered spectral lobes have higher power, constituting a powerful and practical approach for energy scaling the resulting femtosecond sources. We use two commercially available photonic crystal fibers to verify the simulation results. More specific, use of 20-mm fiber NL-1050-ZERO-2 enables us to implement an Yb-fiber laser based ultrafast source, delivering femtosecond (70-120 fs) pulses tunable from 825 nm to 1210 nm with >1 nJ pulse energy.
Directory of Open Access Journals (Sweden)
Rodrigo Pessoa Cavalcanti Lira
2008-02-01
Full Text Available PURPOSE: To report the efficacy and safety of green laser photocoagulation for threshold retinopathy of prematurity (ROP. METHODS: We reviewed the clinical records of the neonates who had undergone green laser photocoagulation for threshold ROP at the Federal University of Pernambuco in Brazil between January 2004 and January 2006. All procedures were conducted with local anesthetic drops. The neonates were monitored throughout the procedure by a neonatologist. A frequency-doubled solid state laser, diode-pumped, with 532 nm wavelength was used. The presence of tunica vasculosa lentis or cataract were excluded before laser treatment. The following preoperative data were obtained for each patient: age, birth weight and the grade of ROP. Postoperative data included complications associated with the laser treatment, grade of ROP and evaluation whether further surgery was necessary due to failure of laser photocoagulation. RESULTS: Twenty-two neonates underwent photocoagulation with green laser for threshold ROP. A total of 31 eyes were included in the study. The mean gestational age was 30 ± 3 weeks and the mean birth weight was 1120 ± 490 g. Regression of the disease after laser therapy was observed in 30 eyes (96.7%. Despite treatment one eye presented stage 4A. Only 7 eyes required repetitive laser therapy. No adverse effects such as burning anterior segment tissues or bleeding in the anterior chamber occurred. No posterior segment side-effects were observed. Cataract formation was not observed at the last follow-up examination. CONCLUSIONS: Green laser photocoagulation remains an effective and safe alternative to red laser photocoagulation and to cryotherapy in the treatment of threshold ROP.OBJETIVOS: Avaliar a eficácia e segurança da fotocoagulação com laser verde na retinopatia da prematuridade (ROP limiar. MÉTODOS: Foram revisados prontuários dos neonatos submetidos à fotocoagulação com laser verde para ROP limiar, na
High energy, high average power solid state green or UV laser
Hackel, Lloyd A.; Norton, Mary; Dane, C. Brent
2004-03-02
A system for producing a green or UV output beam for illuminating a large area with relatively high beam fluence. A Nd:glass laser produces a near-infrared output by means of an oscillator that generates a high quality but low power output and then multi-pass through and amplification in a zig-zag slab amplifier and wavefront correction in a phase conjugator at the midway point of the multi-pass amplification. The green or UV output is generated by means of conversion crystals that follow final propagation through the zig-zag slab amplifier.
Efficient soft x-ray generation in short wavelength laser produced plasmas
International Nuclear Information System (INIS)
Mochizuki, T.; Yamanaka, C.
1987-01-01
Intense x-ray generation in 1.053, 0.53, 0.26 μm laser-produced plasma has been investigated in the photon energy range of 0.1 to 3keV. The x-ray spectrum is found to have several humps which move to the higher energy side as the atomic number of the target increases. This atomic dependence is explained by a semi-Moseley's law and allows us to predict a target material most suitable for generating the photons of desired energies. Conversion efficiencies of 1.5 -- 3keV x-rays are obtained also as a function of laser wavelength at the intensity of 10/sup 13/W/cm/sup 2/. The conversion efficiency of keV x rays has been enhanced by a factor of 2 -- 3 with a controlled prepulse laser. From the semi-Moseley's law we find that cryogenic targets using either Xe or Kr in a liquid or solid phase may be most useful for a number of applications because they radiate 1 -- 3 keV x rays efficiently and never deposit on the x-ray optical components and the objects to be exposed
High-resolution smile measurement and control of wavelength-locked QCW and CW laser diode bars
Rosenkrantz, Etai; Yanson, Dan; Klumel, Genady; Blonder, Moshe; Rappaport, Noam; Peleg, Ophir
2018-02-01
High-power linewidth-narrowed applications of laser diode arrays demand high beam quality in the fast, or vertical, axis. This requires very high fast-axis collimation (FAC) quality with sub-mrad angular errors, especially where laser diode bars are wavelength-locked by a volume Bragg grating (VBG) to achieve high pumping efficiency in solid-state and fiber lasers. The micron-scale height deviation of emitters in a bar against the FAC lens causes the so-called smile effect with variable beam pointing errors and wavelength locking degradation. We report a bar smile imaging setup allowing FAC-free smile measurement in both QCW and CW modes. By Gaussian beam simulation, we establish optimum smile imaging conditions to obtain high resolution and accuracy with well-resolved emitter images. We then investigate the changes in the smile shape and magnitude under thermal stresses such as variable duty cycles in QCW mode and, ultimately, CW operation. Our smile measurement setup provides useful insights into the smile behavior and correlation between the bar collimation in QCW mode and operating conditions under CW pumping. With relaxed alignment tolerances afforded by our measurement setup, we can screen bars for smile compliance and potential VBG lockability prior to assembly, with benefits in both lower manufacturing costs and higher yield.
He, Xiaoying; Fang, Xia; Liao, Changrui; Wang, D N; Sun, Junqiang
2009-11-23
A simple linear cavity erbium-doped fiber laser based on a Fabry-Perot filter which consists of a pair of fiber Bragg gratings is proposed for tunable and switchable single-longitudinal-mode dual-wavelength operation. The single-longitudinal-mode is obtained by the saturable absorption of an unpumed erbium-doped fiber together with a narrow-band fiber Bragg grating. Under the high pump power (>166 mW) condition, the stable dual-wavelength oscillation with uniform amplitude can be realized by carefully adjusting the polarization controller in the cavity. Wavelength selection and switching are achieved by tuning the narrow-band fiber Bragg grating in the system. The spacing of the dual-wavelength can be selected at 0.20 nm (approximately 25.62 GHz), 0.22 nm (approximately 28.19 GHz) and 0.54 nm (approximately 69.19 GHz).
IR-FEL-induced green fluorescence protein (GFP) gene transfer into plant cell
Awazu, K; Tamiya, E
2002-01-01
A Free Electron Laser (FEL) holds potential for various biotechnological applications due to its characteristics such as flexible wavelength tunability, short pulse and high peak power. We could successfully introduce the Green Fluorescent Protein (GFP) gene into tobacco BY2 cells by IR-FEL laser irradiation. The irradiated area of the solution containing BY2 cells and plasmid was about 0.1 mm sup 2. FEL irradiation at a wavelength of 5.75 and 6.1 mu m, targeting absorption by the ester bond of the lipid and the amide I bond of the protein, respectively, was shown to cause the introduction of the fluorescent dye into the cell. On the other hand, transient expression of the GFP fluorescence was only observed after irradiation at 5.75 mu m. The maximum transfer efficiency was about 0.5%.
International Nuclear Information System (INIS)
Popov, A K; Kimberg, V V
1998-01-01
A study is reported of the combined influence of laser-induced resonances in the energy continuum, of splitting of discrete resonances in the field of several strong radiations, and of absorption of the initial and generated radiations on totally resonant parametric conversion to the short-wavelength range. It is shown that the radiation power can be increased considerably by interference processes involving quantum transitions. (nonlinear optical phenomena and devices)
Energy Technology Data Exchange (ETDEWEB)
Aid, Siti Rahmah; Matsumoto, Satoru [Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8522 (Japan); Fuse, Genshu [SEN Corporation, SBS Tower 9F, 4-10-1 Yoga, Setagaya-ku, Tokyo 158-0097 (Japan); Sakuragi, Susumu [Sumitomo Heavy Industries Ltd., 19 Natsushima-cho, Yokosuka, Kanagawa 237-8555 (Japan)
2011-12-15
The combination of Ge pre-amorphization implantation, low-energy boron implantation, and non-melt laser annealing is a promising method for forming ultrashallow p{sup +}/n junctions in silicon. In this study, shallow p{sup +}/n junctions were formed by non-melt annealing implanted samples using a green laser (visible laser). The dopant diffusion, activation, and recrystallization of an amorphous silicon layer were compared with those obtained in our previous study in which non-melt annealing was performed using a KrF excimer laser (UV laser). The experimental results reveal that only slight diffusion of boron in the tail region occurred in green-laser-annealed samples. In contrast, remarkable boron diffusion occurred in KrF-laser-annealed samples for very short annealing times. Recrystallization of the amorphous silicon layer was slower in green-laser-annealed samples than in KrF-laser-annealed samples. We consider the penetration depth and the pulse duration are important factors that may affect boron diffusion. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
DEFF Research Database (Denmark)
Jensen, Ole Bjarlin; Hansen, Anders Kragh; Müller, André
2017-01-01
Multi-Watt efficient compact green laser sources are required for a number of applications e.g. within biophotonics, laser pumping and laser displays. We present generation of 3.5 W of diffraction-limited green light at 515 nm by second harmonic generation (SHG) of a tapered diode laser, itself...... yielding more than 9 W at 1030 nm. SHG is performed in single pass through a cascade of two nonlinear crystals with re-focusing and dispersion compensating optics between the two nonlinear crystals. The laser is single-frequency and the output power is stabilized to better than ±0.4%....
Laser Spot Welding of Copper-aluminum Joints Using a Pulsed Dual Wavelength Laser at 532 and 1064 nm
Stritt, Peter; Hagenlocher, Christian; Kizler, Christine; Weber, Rudolf; Rüttimann, Christoph; Graf, Thomas
A modulated pulsed laser source emitting green and infrared laser light is used to join the dissimilar metals copper and aluminum. The resultant dynamic welding process is analyzed using the back reflected laser light and high speed video observations of the interaction zone. Different pulse shapes are applied to influence the melt pool dynamics and thereby the forming grain structure and intermetallic phases. The results of high-speed images and back-reflections prove that a modulation of the pulse shape is transferred to oscillations of the melt pool at the applied frequency. The outcome of the melt pool oscillation is shown by the metallurgically prepared cross-section, which indicates different solidification lines and grain shapes. An energy-dispersivex-ray analysis shows the mixture and the resultant distribution of the two metals, copper and aluminum, within the spot weld. It can be seen that the mixture is homogenized the observed melt pool oscillations.
Green laser induced foveal cyst sustained in a recreational laser light show
Directory of Open Access Journals (Sweden)
Rukiye Aydin
2017-04-01
Full Text Available We report the case of a 9-year-old boy complained of visual loss in his right eye after watching green laser light show being hit by a ray of a laser at shopping center before five days ago. The laser had a maximum power rating of 30 mW (US Food and Drug Administration class IIIB. Best-corrected visual acuity in his right eye was 0.2 with Snellen at 5 days after the injury. Dilated fundoscopic examination demonstrated a macular hole appearance in the right eye. Spectral domain optical coherence tomography (OCT, Spectralis, Heidelberg Engineering, Heidelberg, Germany demonstrates a steep fovea contour, a thickening of the macular edges, intraretinal cysts, disruption of the photoreceptor inner segment/outer segment layer and macular pseudohole formation. Central foveal thickness (515 µm was increased. Two months after the injury, the patient's visual acuity improved to 0.9 in the right eye without any ocular treatment. Spectral domain OCT revealed the closure of the macular hole with the resolution of the cystic spaces. At 6-months follow-up, visual function had fully recovered and macular assessment was normal.
Room-temperature operation of quantum cascade lasers at a wavelength of 5.8 μm
Energy Technology Data Exchange (ETDEWEB)
Babichev, A. V. [Connector Optics LLC (Russian Federation); Bousseksou, A. [University Paris Saclay, Institut d’Electronique Fondamentale, UMR 8622 CNRS (France); Pikhtin, N. A.; Tarasov, I. S. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Nikitina, E. V. [Russian Academy of Sciences, Saint Petersburg Academic University—Nanotechnology Research and Education Center (Russian Federation); Sofronov, A. N.; Firsov, D. A.; Vorobjev, L. E. [Peter-the-Great Saint-Petersburg Polytechnic University (Russian Federation); Novikov, I. I.; Karachinsky, L. Ya.; Egorov, A. Yu., E-mail: anton.egorov@connector-optics.com [Connector Optics LLC (Russian Federation)
2016-10-15
The room-temperature generation of multiperiod quantum-cascade lasers (QCL) at a wavelength of 5.8 μm in the pulsed mode is demonstrated. The heterostructure of a quantum-cascade laser based on a heterojunction of InGaAs/InAlAs alloys is grown by molecular-beam epitaxy and incorporates 60 identical cascades. The threshold current density of the stripe laser 1.4 mm long and 22 μm wide is ~4.8 kA/cm{sup 2} at a temperature of 303 K. The maximum power of the optical-radiation output from one QCL face, recorded by a detector, is 88 mW. The actual optical-power output from one QCL face is no less than 150 mW. The results obtained and possible ways of optimizing the structure of the developed quantum-cascade lasers are discussed.
DEFF Research Database (Denmark)
Helbo, Bjarne; Kragh, Søren; Kjeldsen, B.G.
2003-01-01
We investigate a micro-fluidic dye laser, which can be integrated with polymer-based lab-on-a-chip microsystems without further processing steps. A simple rate-equation model is used to predict the lasing threshold. The laser device is characterised using the laser dye Rhodamine 6G dissolved...... in ethanol, and the influence of dye concentration on the lasing wavelength and threshold is investigated. The experiments confirm the predictions of the rate-equation model, that lasing can be achieved in the 10 mum long laser cavity with moderate concentrations of Rhodamine 6G in ethanol, starting from 5 x...
Neuroscience imaging enabled by new highly tunable and high peak power femtosecond lasers
Hakulinen, T.; Klein, J.
2017-02-01
Neuroscience applications benefit from recent developments in industrial femtosecond laser technology. New laser sources provide several megawatts of peak power at wavelength of 1040 nm, which enables simultaneous optogenetics photoactivation of tens or even hundreds of neurons using red shifted opsins. Another recent imaging trend is to move towards longer wavelengths, which would enable access to deeper layers of tissue due to lower scattering and lower absorption in the tissue. Femtosecond lasers pumping a non-collinear optical parametric amplifier (NOPA) enable the access to longer wavelengths with high peak powers. High peak powers of >10 MW at 1300 nm and 1700 nm allow effective 3-photon excitation of green and red shifted calcium indicators respectively and access to deeper, sub-cortex layers of the brain. Early results include in vivo detection of spontaneous activity in hippocampus within an intact mouse brain, where neurons express GCaMP6 activated in a 3-photon process at 1320 nm.
Wavelength tunable CW red laser generated based on an intracavity-SFG composite cavity
Zhang, Z. N.; Bai, Y.; Lei, G. Z.; Bai, B.; Sun, Y. X.; Hu, M. X.; Wang, C.; Bai, J. T.
2016-12-01
We report a wavelength-tunable watt-level continuous wave (CW) red laser that uses a composite cavity based on an intracavity sum-frequency generation (SFG). The composite cavity is composed of a LD side-pumped Nd: GdVO4 p-polarized 1062.9 nm resonant cavity and a resonant optical parametric oscillator (SRO) of s-polarized signal light using a periodically poled crystal MgO: PPLN. Based on the temperature tuning from 30 °C to 200 °C, the CW red laser beams are obtained in a tunable waveband from 634.4 nm to 649.1 nm, corresponding to a tunable output waveband from 3278.0 nm to 2940.2 nm of the mid-infrared idler lights. The maximum CW output power of the red laser at 634.4 nm and the idler light at 3278.0 nm reach 3.03 W and 4.13 W under 30 °C, respectively.
Passively synchronized dual-wavelength Q-switched lasers
DEFF Research Database (Denmark)
Janousek, Jiri; Tidemand-Lichtenberg, Peter; Mortensen, Jesper Liltorp
We present a simple and efficient way of generating synchronized Q-switched pulses at wavelengths hundreds of nanometers apart. This principle can result in new pulsed all-solid-state light sources at new wavelengths based on SFG.......We present a simple and efficient way of generating synchronized Q-switched pulses at wavelengths hundreds of nanometers apart. This principle can result in new pulsed all-solid-state light sources at new wavelengths based on SFG....
Beckett, Douglas J. S.; Hickey, Ryan; Logan, Dylan F.; Knights, Andrew P.; Chen, Rong; Cao, Bin; Wheeldon, Jeffery F.
2018-02-01
Quantum dot comb sources integrated with silicon photonic ring-resonator filters and modulators enable the realization of optical sub-components and modules for both inter- and intra-data-center applications. Low-noise, multi-wavelength, single-chip, laser sources, PAM4 modulation and direct detection allow a practical, scalable, architecture for applications beyond 400 Gb/s. Multi-wavelength, single-chip light sources are essential for reducing power dissipation, space and cost, while silicon photonic ring resonators offer high-performance with space and power efficiency.
International Nuclear Information System (INIS)
Deladurantaye, P; Roy, V; Desbiens, L; Drolet, M; Taillon, Y; Galarneau, P
2011-01-01
We report on a novel pulsed fiber laser platform providing pulse shaping agility at high repetition rates and at a wavelength of 532 nm. The oscillator is based on the direct modulation of a seed laser diode followed by a chain of fiber amplifiers. Advanced Large Mode Area (LMA) fiber designs as well as proprietary techniques to mitigate non-linear effects enable output energy per pulse up to 100 μJ at 1064 nm with diffraction-limited beam quality and narrow line widths suitable for efficient frequency conversion. Ultra stable pulses with tailored pulse shapes were demonstrated in the green region of the spectrum at repetition rates higher than 200 kHz. Pulse durations between 2.5 ns and 640 ns are available, as well as pulse to pulse dynamic shape selection at repetition rates up to 1 MHz. The pulse energy stability at 532 nm is better than ± 1.5%, 3σ, over 10 000 pulses. Excellent beam characteristics were obtained. The M 2 parameter is lower than 1.05, the beam waist astigmatism and beam waist asymmetry are below 10% and below 8% respectively, with high stability over time. We foresee that the small spot size, high repetition rate and pulse tailoring capability of this platform will provide advantages to practitioners who are developing novel, advanced processes in many industrially important applications.
Sun, Chunran; Dong, Yue; Wang, Muguang; Jian, Shuisheng
2018-03-01
The detection of liquid level and temperature based on a fiber ring cavity laser sensing configuration is presented and demonstrated experimentally. The sensing head contains a fiber Bragg grating (FBG) and a single-mode-cladding-less-single-mode multimode interferometer, which also functions as wavelength-selective components of the fiber laser. When the liquid level or temperature is applied on the sensing head, the pass-band peaks of both multimode interference (MMI) filter and FBG filter vary and the two output wavelengths of the laser shift correspondingly. In the experiment, the corresponding sensitivities of the liquid level with four different refractive indices (RI) in the deep range from 0 mm to 40 mm are obtained and the sensitivity enhances with the RI of the liquid being measured. The maximum sensitivity of interferometer is 106.3 pm/mm with the RI of 1.391. For the temperature measurement, a sensitivity of 10.3 pm/°C and 13.8 pm/°C are achieved with the temperature ranging from 0 °C to 90 °C corresponding to the two lasing wavelengths selective by the MMI filter and FBG, respectively. In addition, the average RI sensitivity of 155.77 pm/mm/RIU is also obtained in the RI range of 1.333-1.391.
High contrast laser marking of alumina
International Nuclear Information System (INIS)
Penide, J.; Quintero, F.; Riveiro, A.; Fernández, A.; Val, J. del; Comesaña, R.; Lusquiños, F.; Pou, J.
2015-01-01
Highlights: • Laser marking of alumina using near infrared (NIR) lasers was experimentally analyzed. • Color change produced by NIR lasers is due to thermally induced oxygen vacancies. • Laser marking results obtained using NIR lasers and green laser are compared. • High contrast marks on alumina were achieved. - Abstract: Alumina serves as raw material for a broad range of advanced ceramic products. These elements should usually be identified by some characters or symbols printed directly on them. In this sense, laser marking is an efficient, reliable and widely implemented process in industry. However, laser marking of alumina still leads to poor results since the process is not able to produce a dark mark, yielding bad contrast. In this paper, we present an experimental study on the process of marking alumina by three different lasers working in two wavelengths: 1064 nm (Near-infrared) and 532 nm (visible, green radiation). A colorimetric analysis has been carried out in order to compare the resulting marks and its contrast. The most suitable laser operating conditions were also defined and are reported here. Moreover, the physical process of marking by NIR lasers is discussed in detail. Field Emission Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy were also employed to analyze the results. Finally, we propose an explanation for the differences of the coloration induced under different atmospheres and laser parameters. We concluded that the atmosphere is the key parameter, being the inert one the best choice to produce the darkest marks
Free-space wavelength-multiplexed optical scanner.
Yaqoob, Z; Rizvi, A A; Riza, N A
2001-12-10
A wavelength-multiplexed optical scanning scheme is proposed for deflecting a free-space optical beam by selection of the wavelength of the light incident on a wavelength-dispersive optical element. With fast tunable lasers or optical filters, this scanner features microsecond domain scan setting speeds and large- diameter apertures of several centimeters or more for subdegree angular scans. Analysis performed indicates an optimum scan range for a given diffraction order and grating period. Limitations include beam-spreading effects based on the varying scanner aperture sizes and the instantaneous information bandwidth of the data-carrying laser beam.
International Nuclear Information System (INIS)
Piper, L.G.; Krech, R.H.; Pugh, E.R.; Taylor, R.L.
1978-01-01
A concept for the development of an efficient short wavelength laser based on a class of endoergic molecules-azides is being studied. One of these two laser-device experiments involves generating high concentrations of azide radicals in the thermal pyrolysis of solid, ionic azides, with the subsequent excitation of the N 2 (B 3 pi/sub g/) state from azide-radical recombination. Laser action would then take place upon the N 2 (B 3 pi/sub g/ - A 3 Sigma + /sub u/), first-postive transition. The second laser-demonstration experiment involves creating a high density of NCl(b 1 Sigma + ) state by uv photolysis of ClN 3 . In this case laser emission is expected on the NCl(b 1 Sigma + → X 3 Sigma - ) transition at 665 nm
Frequency-doubled green picosecond laser based on K3B6O10Br nonlinear optical crystal
Meng, Luping; Zhang, Ling; Hou, Zhanyu; Wang, Lirong; Xu, Hui; Shi, Meng; Wang, Lingwu; Yang, Yingying; Qi, Yaoyao; He, Chaojian; Yu, Haijuan; Lin, Xuechun; Su, Fufang; Xia, Mingjun; Li, Rukang
2018-05-01
We report a frequency-doubled green picosecond (ps) laser based on K3B6O10Br (KBB) nonlinear optical crystal with cutting angle of θ = 34.7° and φ = 30°. Through intracavity frequency doubling using a type I phase-matched KBB crystal with dimensions of 4 mm × 4 mm × 13.2 mm, the average output power of 185.00 mW green ps laser was obtained with a repetition rate of 80 MHz and pulse width of 25.0 ps. In addition, we present external frequency doubling using KBB crystal. The average output power of 3.00 W green ps laser was generated with a repetition rate of 10 kHz and pulse width of 38.1 ps, which corresponds to a pulse energy of 0.30 mJ and a peak power 7.89 MW, respectively. The experimental results show that KBB crystal is a promising nonlinear optical material.
Xu, Jiangmin; Chen, Chao; Zhang, Tengfei; Han, Zhenchun
2017-01-01
Based on PVDF (piezoelectric sensing techniques), this paper attempts to study the propagation law of shock waves in brittle materials during the process of three-wavelength laser irradiation of polysilicon, and discusses the formation mechanism of thermal shock failure. The experimental results show that the vapor pressure effect and the plasma pressure effect in the process of pulsed laser irradiation lead to the splashing of high temperature and high density melt. With the decrease of the ...
Ramm, Daniel
2018-02-01
Three dimensional dosimetry by optical CT readout of radiosensitive gels or solids has previously been indicated as a solution for measurement of radiotherapy 3D dose distributions. The clinical uptake of these dosimetry methods has been limited, partly due to impracticalities of the optical readout such as the expertise and labour required for refractive index fluid matching. In this work a fast laser beam optical CT scanner is described, featuring fluid-less and dual wavelength operation. A second laser with a different wavelength is used to provide an alternative reference scan to the commonly used pre-irradiation scan. Transmission data for both wavelengths is effectively acquired simultaneously, giving a single scan process. Together with the elimination of refractive index fluid matching issues, scanning practicality is substantially improved. Image quality and quantitative accuracy were assessed for both dual and single wavelength methods. The dual wavelength scan technique gave improvements in uniformity of reconstructed optical attenuation coefficients in the sample 3D volume. This was due to a reduction of artefacts caused by scan to scan changes. Optical attenuation measurement accuracy was similar for both dual and single wavelength modes of operation. These results established the basis for further work on dosimetric performance.
Wang, Ya-fei; Huang, Qun-xing; Wang, Fei; Chi, Yong; Yan, Jian-hua
2018-01-01
A novel method to evaluate the quantitative effects of soot morphology and incident wavelength on the measurement accuracy of soot volume fraction, by the laser extinction (LE) technique is proposed in this paper. The results indicate that the traditional LE technique would overestimate soot volume fraction if the effects of morphology and wavelength are not considered. Before the agglomeration of isolated soot primary particles, the overestimation of the LE technique is in the range of 2-20%, and rises with increasing primary particle diameter and with decreasing incident wavelength. When isolated primary particles are agglomerated into fractal soot aggregates, the overestimation would exceed 30%, and rise with increasing primary particle number per soot aggregate, fractal dimension and fractal prefactor and with decreasing incident wavelength to a maximum value of 55%. Finally, based on these results above, the existing formula of the LE technique gets modified, and the modification factor is 0.65-0.77.
DEFF Research Database (Denmark)
Omar, Ghada Said Mohammed; Wilson, Michael; Nair, Sean P.
2008-01-01
Background: The increase in resistance to antibiotics among disease-causing bacteria necessitates the development of alternative antimicrobial approaches such as the use of light-activated antimicrobial agents (LAAAs). Light of an appropriate wavelength activates the LAAA to produce cytotoxic...... of the bacteria. Conclusion: These findings imply that indocyanine green in combination with light from a nearinfrared laser may be an effective means of eradicating bacteria from wounds and burns....
Multi-wavelength Brillouin Raman erbium-doped fiber laser generation in a linear cavity
International Nuclear Information System (INIS)
Shirazi, M R; Harun, S W; Ahmad, H
2014-01-01
A multi-wavelength Brillouin Raman erbium-doped fiber laser is proposed and demonstrated. The setup uses a 7.7 km dispersion compensating fiber simultaneously as the Brillouin and Raman nonlinear gain media and operates in conjunction with a 3 m erbium-doped fiber as the linear gain medium. At a Brillouin pump (BP) wavelength of 1530 nm, where Raman and erbium gains overlap each other, 34 Brillouin Stokes lines having line spacing of 0.075 nm are created by using a Raman pump power of only 24.1 dBm, an erbium pump power of about 22.1 dBm, and a BP power of 6.5 dBm in the proposed linear cavity. The system is highly efficient and is able to generate many comparable peak-power lines at a low pump power. (paper)
Wang, J.-K.; Siegal, Y.; Lü, C.; Mazur, E.
1992-07-01
We use self-phase modulation in a single-mode fiber to produce broadband femtosecond laser pulses. Subsequent amplification through two Bethune cells yields high-energy, tunable, pulses synchronized with the output of an amplified colliding-pulse-modelocked (CPM) laser. We routinely obtain tunable 200 μJ pulses of 42 fs (fwhm) duration with a nearly perfect gaussian spatial profile. Although self-phase modulation in a single-mode fiber is widely used in femtosecond laser systems, amplification of a fiber-generated supercontinuum in a Bethune cell amplifier is a new feature which maintains the high-quality spatial profile while providing high gain. This laser system is particularly well suited for high energy dual-wavelength pump=probe experiments and time-resolved four-wave mixing spectroscopy.
Energy Technology Data Exchange (ETDEWEB)
Piper, L.G.; Krech, R.H.; Taylor, R.L.
1978-05-01
Under this program PSI is investigating the photolytic decomposition of a class of endoergic molecules - azides. Because these compounds contain substantial chemical energy, they offer a potentially more efficient approach for the production of electronically excited fragments. The goal of the present program was to acquire sufficient data and understanding of certain fundamental processes to permit the critical evaluation of this approach for laser development. An apparatus was built to study the wavelength-selected photolysis of gaseous, covalent azides. The photolysis source is a frequency doubled, tuneable dye laser. Detection of fragment species is accomplished by observation of primary fluorescence, or by laser-induced fluorescence (LIF) using a second tuneable dye laser. The design of the apparatus is discussed in detail.
Directory of Open Access Journals (Sweden)
José Santiago Pozo-Antonio
2018-03-01
Full Text Available Currently, removal of graffiti from stone monuments is a particularly challenging task. Lasers, being highly controllable and precise tools with minimal chemical waste, offer a key solution in this respect and a significant amount of research has been dedicated to this subject. Studies related to the laser cleaning of carbonate stones (such as limestone and marble reported the extraction of the graffiti layer, although minimal damage to the substrate can be also detected. Recently, research efforts have been focused on the cleaning of granite, which is a complex stone due to its grained and polymineralic texture. Tests involving different wavelengths indicated that the effectiveness of the cleaning procedure is highly dependent on two components: The composition of the binding medium of the graffiti and the fissure system of the granite. In that direction, the aim of this paper is to investigate and to compare the cleaning effectiveness of two wavelengths emitted from a nanosecond (ns Q-Switched Nd:YAG laser system (IR at 1064 nm and UV at 355 nm, as well as their simultaneous application at different energy density ratios FIR/FUV. The effectiveness of this combined methodology has been shown in several other cases; i.e., for the removal of pollution crusts from carbonate stones (marble. For this study, three different in composition graffiti paints (blue, black, and silver were applied on a fine-grained granite originating from the NW Iberian Peninsula. Prior to the irradiation tests, the damage thresholds of the granite, as well as the extraction thresholds of the graffiti, were determined. Then, several tests involving a variety of parameters (fluence value, number of pulses, etc. were performed and the most satisfactory irradiation conditions from each individual wavelength as well as their combination were compared, based on graffiti extraction level and any damage induced on the granite forming minerals. The analytical techniques used for
Liu, Jie; Zeng, Duoduo; Guo, Changjian; Xu, Lei; He, Sailing
2010-10-25
We propose and demonstrate an OCDMA-PON scheme with optical network unit (ONU) internetworking capability, which utilizes low-cost gain-switched Fabry-Pérot (GS-FP) lasers with external dual-wavelength injection as the pulse sources on the ONU side. The injection-generated optical pulses in two wavelengths from the same GS-FP laser are used separately for the PON uplink transmission and ONU internetworking. Experimental results based on a two-user OCDMA system confirm the feasibility of the proposed scheme. With OCDMA technologies, separate ONU-internetworking groups can be established using different optical codes. We also give experiment results to analyze the performance of the ONU-ONU transmission at different power of interference signals when two ONU-internetworking groups are present in the OCDMA-PON.
Lopez-Espiricueta, Dunia; Fearon, Eamonn; Edwardson, Stuart; Dearden, Geoffrey
The Laser Assisted Direct Write (LA-DW) method has been implemented in the development of different markets and material processing, recently also used for creating Printed Circuit Boards (PCB) or electrical circuitry. The process consists in the deposition of metallic nano-particle (NP) inks, which are afterwards cured or sintered by laser irradiation, thus creating conductive pathways; advantages are speed, accuracy and the protection of the heat affected zone (HAZ). This research will study the behaviour of the heat dissipation relatively within the Nano-particle Copper paste after being irradiated with 1064 nm and 532 nm wavelengths, research will be developed on different widths and depths deposited onto flat surfaces such as flexible PET. Comparisons to be made between resistivity results obtained from different wavelengths.
Energy Technology Data Exchange (ETDEWEB)
Piper, L.G.; Krech, R.H.; Pugh, E.R.; Taylor, R.L.
1978-12-01
A concept for the development of an efficient short wavelength laser based on a class of endoergic molecules-azides is being studied. One of these two laser-device experiments involves generating high concentrations of azide radicals in the thermal pyrolysis of solid, ionic azides, with the subsequent excitation of the N/sub 2/(B/sup 3/pi/sub g/) state from azide-radical recombination. Laser action would then take place upon the N/sub 2/(B/sup 3/pi/sub g/ - A/sup 3/Sigma/sup +//sub u/), first-postive transition. The second laser-demonstration experiment involves creating a high density of NCl(b/sup 1/Sigma/sup +/) state by uv photolysis of ClN/sub 3/. In this case laser emission is expected on the NCl(b/sup 1/Sigma/sup +/ ..-->.. X/sup 3/Sigma/sup -/) transition at 665 nm.
Energy Technology Data Exchange (ETDEWEB)
Krech, R.H.; Piper, L.G.; Pugh, E.R.; Taylor, R.L.
1979-03-01
A concept for the development of an efficient short wavelength laser based on a class of endoergic molecules-azides is being investigated. The first of two laser-device experiments involves generating high concentrations of azide radicals in the thermal pyrolysis of solid, ionic azides, with the subsequent excitation of the N/sub 2/(B/sup 3/..pi../sub g/) state from azide-radical recombination. Laser action would then take place upon the N/sub 2/(B/sup 3/..pi../sub g/-A/sup 3/..sigma../sup +//sub u/), first-positive transition. The second laser-demonstration experiment involves creating a high density of NCl(b/sup 1/..sigma../sup +/) state by uv photolysis of ClN/sub 3/. In this case laser emission is expected on the NCl(b/sup 1/..sigma../sup +/..-->..X/sup 3/..sigma../sup -/) transition at 665 nm.
Dual wavelength Mode-Locking of InAs/InP quantum dot laser diodes at 1.5µm
Tahvili, M.S.; Heck, M.J.R.; Nötzel, R.; Smit, M.K.; Bente, E.A.J.M.
2011-01-01
We report on stable dual-wavelength mode-locking of 3.1GHz and 10GHz two-section InAs/InP(100) quantum dot laser diodes. Evaluation of relative time delay between different spectral components indicates opposite sign of chirp over the two spectral lobes
Integrated Wavelength-Tunable Light Source for Optical Gas Sensing Systems
Directory of Open Access Journals (Sweden)
Bin Li
2015-01-01
Full Text Available A compact instrument consisting of a distributed feedback laser (DFB at 1.65 μm was developed as a light source for gas sensing systems using tunable diode laser absorption spectroscopy (TDLAS technique. The wavelength of laser is tuned by adjusting the laser working temperature and injection current, which are performed by self-developed temperature controller and current modulator respectively. Stability test shows the fluctuation of the laser temperature is within the range of ±0.02°C. For gas detection experiments, the wavelength is tuned around the gas absorption line by adjusting laser temperature and is then shifted periodically to scan across the absorption line by the laser current modulator, which generates a 10 Hz saw wave signal. In addition, the current modulator is able to generate sine wave signal for gas sensing systems using wavelength modulation spectroscopy (WMS technique involving extraction of harmonic signals. The spectrum test proves good stability that the spectrum was measured 6 times every 10 minutes at the constant temperature and current condition. This standalone instrument can be applied as a light source for detection systems of different gases by integrating lasers at corresponding wavelength.
Thermal damage control of dye-assisted laser tissue welding: effect of dye concentration
Xie, Hua; Buckley, Lisa A.; Prahl, Scott A.; Shaffer, Brian S.; Gregory, Kenton W.
2001-05-01
Successful laser-assisted tissue welding was implemented to provide proper weld strength with minimized tissue thermal injury. We investigated and compared the weld strengths and morphologic changes in porcine small intestinal submucose (SIS) and porcine ureteral tissues with various concentration of indocyanine green (ICG) and with a solid albumin sheet. The study showed that the tissues were welded at lower ICG concentration (0.05 mM) with minimized tissue thermal damage using an 800-nm wavelength diode laser.
Soltwisch, Jens; Jaskolla, Thorsten W; Hillenkamp, Franz; Karas, Michael; Dreisewerd, Klaus
2012-08-07
The laser wavelength constitutes a key parameter in ultraviolet-matrix-assisted laser desorption ionization-mass spectrometry (UV-MALDI-MS). Optimal analytical results are only achieved at laser wavelengths that correspond to a high optical absorption of the matrix. In the presented work, the wavelength dependence and the contribution of matrix proton affinity to the MALDI process were investigated. A tunable dye laser was used to examine the wavelength range between 280 and 355 nm. The peptide and matrix ion signals recorded as a function of these irradiation parameters are displayed in the form of heat maps, a data representation that furnishes multidimensional data interpretation. Matrixes with a range of proton affinities from 809 to 866 kJ/mol were investigated. Among those selected are the standard matrixes 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (HCCA) as well as five halogen-substituted cinnamic acid derivatives, including the recently introduced 4-chloro-α-cyanocinnamic acid (ClCCA) and α-cyano-2,4-difluorocinnamic acid (DiFCCA) matrixes. With the exception of DHB, the highest analyte ion signals were obtained toward the red side of the peak optical absorption in the solid state. A stronger decline of the molecular analyte ion signals generated from the matrixes was consistently observed at the low wavelength side of the peak absorption. This effect is mainly the result of increased fragmentation of both analyte and matrix ions. Optimal use of multiply halogenated matrixes requires adjustment of the excitation wavelength to values below that of the standard MALDI lasers emitting at 355 (Nd:YAG) or 337 nm (N(2) laser). The combined data provide new insights into the UV-MALDI desorption/ionization processes and indicate ways to improve the analytical sensitivity.
Wang, M.; Huang, Y. J.; Ruan, S. C.
2018-04-01
In this paper, we have demonstrated a theta cavity passively Q-switched dual-wavelength fiber laser based on a multimode interference filter and a semiconductor saturable absorber. Relying on the properties of the fiber theta cavity, the laser can operate unidirectionally without an optical isolator. A semiconductor saturable absorber played the role of passive Q-switch while a section of single-mode-multimode-single-mode fiber structure served as an multimode interference filter and was used for selecting the lasing wavelengths. By suitably manipulating the polarization controller, stable dual-wavelength Q-switched operation was obtained at ~1946.8 nm and ~1983.8 nm with maximum output power and minimum pulse duration of ~47 mW and ~762.5 ns, respectively. The pulse repetition rate can be tuned from ~20.2 kHz to ~79.7 kHz by increasing the pump power from ~2.12 W to ~5.4 W.
Wavelength dependence of femtosecond laser-induced damage threshold of optical materials
Energy Technology Data Exchange (ETDEWEB)
Gallais, L., E-mail: laurent.gallais@fresnel.fr; Douti, D.-B.; Commandré, M. [Aix-Marseille Université, CNRS, Centrale Marseille, Institut Fresnel UMR 7249, 13013 Marseille (France); Batavičiūtė, G.; Pupka, E.; Ščiuka, M.; Smalakys, L.; Sirutkaitis, V.; Melninkaitis, A. [Laser Research Center, Vilnius University, Saulétekio aléja 10, LT-10223 Vilnius (Lithuania)
2015-06-14
An experimental and numerical study of the laser-induced damage of the surface of optical material in the femtosecond regime is presented. The objective of this work is to investigate the different processes involved as a function of the ratio of photon to bandgap energies and compare the results to models based on nonlinear ionization processes. Experimentally, the laser-induced damage threshold of optical materials has been studied in a range of wavelengths from 1030 nm (1.2 eV) to 310 nm (4 eV) with pulse durations of 100 fs with the use of an optical parametric amplifier system. Semi-conductors and dielectrics materials, in bulk or thin film forms, in a range of bandgap from 1 to 10 eV have been tested in order to investigate the scaling of the femtosecond laser damage threshold with the bandgap and photon energy. A model based on the Keldysh photo-ionization theory and the description of impact ionization by a multiple-rate-equation system is used to explain the dependence of laser-breakdown with the photon energy. The calculated damage fluence threshold is found to be consistent with experimental results. From these results, the relative importance of the ionization processes can be derived depending on material properties and irradiation conditions. Moreover, the observed damage morphologies can be described within the framework of the model by taking into account the dynamics of energy deposition with one dimensional propagation simulations in the excited material and thermodynamical considerations.
Li, Guang; Sun, Jianfang; Shao, Xuebao; Sang, Honggui; Zhou, Zhanchao
2011-10-01
After laser irradiation, hemoglobin can transform into methemoglobin and coagulum, which have high absorptivity of near-infrared light. Sequential irradiation with 595 nm and 1,064 nm may be more effective than single wavelength to decrease residual vessel number in rooster combs. Six protocols (single pulse with 595 nm, double pulse with 595 nm, single pulse with 1,064 nm, double pulse with 1,064 nm, sequential irradiation with 595 nm and 1,064 nm (multiplex), and a blank control group) were used to compare the effects of sequential and single-wavelength irradiation on reducing residual vessel number, as well as the epidermal side effects, in the rooster comb. Different treatment techniques were applied to the same comb, at the same time. The treated areas of the epidermis and the residual vessels were observed using an optical microscope. All five techniques were effective in decreasing the number of residual vessels in the comb, and the side effects on the epidermis were similar for all. Considering the selectivity of the 595-nm laser and the rich melanin in the human epidermis, the dual-wavelength laser has a distinct advantage in treating vascular lesions. The authors have indicated no significant interest with commercial supporters. © 2011 by the American Society for Dermatologic Surgery, Inc.
International Nuclear Information System (INIS)
Lasagni, Andres F.; Shao, Peng; Hendricks, Jeffrey L.; Shaw, Charles M.; Martin, David C.; Das, Suman
2010-01-01
A simple optical interference method for the fabrication of simply periodic and periodic with a substructure on poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) using femtosecond laser interference patterns is demonstrated. The femtosecond laser pulse was split by a diffractive beam splitter and overlapped with two lenses. Homogeneous periodic arrays could be fabricated even using a single laser pulse. In addition, multipulse irradiation resulted in reproducible sub-wavelength ripples oriented perpendicularly to the laser polarization with spatial period from 170 to 220 nm (around one-fourth of the laser wavelength). In addition, the observed size of the spatial period was not affected by the number of incident laser pulses or accumulated energy density. Using high energy pulses it was possible to completely remove the PEDOT:PSS layer without inducing damage to the underneath substrate.
Liles, Alexandros A; Debnath, Kapil; O'Faolain, Liam
2016-03-01
We report the experimental demonstration of a new design for external cavity hybrid lasers consisting of a III-V semiconductor optical amplifier (SOA) with fiber reflector and a photonic crystal (PhC)-based resonant reflector on SOI. The silicon reflector is composed of an SU8 polymer bus waveguide vertically coupled to a PhC cavity and provides a wavelength-selective optical feedback to the laser cavity. This device exhibits milliwatt-level output power and side-mode suppression ratios of more than 25 dB.
DEFF Research Database (Denmark)
Hansen, Anders Kragh; Jensen, Ole Bjarlin; Sumpf, Bernd
2014-01-01
Many applications, e.g., within biomedicine stand to benefit greatly from the development of diode laser-based multi- Watt efficient compact green laser sources. The low power of existing diode lasers in the green area (about 100 mW) means that the most promising approach remains nonlinear...... frequency conversion of infrared tapered diode lasers. Here, we describe the generation of 3.5 W of diffraction-limited green light from SHG of a single tapered diode laser, itself yielding 10 W at 1063 nm. This SHG is performed in single pass through a cascade of two PPMgO:LN crystals with re...... power of 3.5 W corresponds to a power enhancement greater than 2 compared to SHG in each of the crystals individually and is the highest visible output power generated by frequency conversion of a single diode laser. Such laser sources provide the necessary pump power for biophotonics applications...
Ahmad, H.; Samion, M. Z.; Sharbirin, A. S.; Norizan, S. F.; Aidit, S. N.; Ismail, M. F.
2018-05-01
Graphene, a 2D material, has been used for generation of pulse lasers due to the presence of its various fascinating optical properties compared to other materials. Hence in this paper, we report the first demonstration of a thulium doped fiber laser with a wavelength-tunable, passive Q-switched output using a graphene-polyvinyl-alcohol composite film for operation in the 2.0 µm region. The proposed laser has a wavelength-tunable output spanning from 1932.0 nm to 1946.0 nm, giving a total tuning range of 14.0 nm. The generated pulse has a maximum repetition rate and average output power of 36.29 kHz and 0.394 mW at the maximum pump power of 130.87 mW, as well as a pulse width of 6.8 µs at this pump power. The generated pulses have a stable output, having a signal-to-noise ratio of 31.75 dB, and the laser output is stable when tested over a period of 60 min. The proposed laser would have multiple applications for operation near the 2.0 micron region, especially for bio-medical applications and range-finding.
Tahvili, M S; Du, L; Heck, M J R; Nötzel, R; Smit, M K; Bente, E A J M
2012-03-26
We present an investigation of passive and hybrid mode-locking in Fabry-Pérot type two-section InAs/InP(100) quantum dot lasers that show dual wavelength operation. Over the whole current and voltage range for mode-locking of these lasers, the optical output spectra show two distinct lobes. The two lobes provide a coherent bandwidth and are verified to lead to two synchronized optical pulses. The generated optical pulses are elongated in time due to a chirp which shows opposite signs over the two spectral lobes. Self-induced mode-locking in the single-section laser shows that the dual-wavelength spectra correspond to emission from ground state. In the hybrid mode-locking regime, a map of locking range is presented by measuring the values of timing jitter for several values of power and frequency of the external electrical modulating signal. An overview of the systematic behavior of InAs/InP(100) quantum dot mode-locked lasers is presented as conclusion.
Physics of short-wavelength-laser design
Energy Technology Data Exchange (ETDEWEB)
Hagelstein, P.L.
1981-01-01
The physics and design of vuv and soft x-ray lasers pumped by ICF class high intensity infrared laser drivers are described (for example, the SHIVA laser facility at LLNL). Laser design and physics issues are discussed in the case of a photoionization pumping scheme involving Ne II and line pumping schemes involving H-like and He-like neon.
Dual-wavelength vortex beam with high stability in a diode-pumped Yb:CaGdAlO4 laser
Shen, Yijie; Meng, Yuan; Fu, Xing; Gong, Mali
2018-05-01
We present a stable dual-wavelength vortex beam carrying orbital angular momentum (OAM) with two spectral peaks separated by a few terahertz in a diode-pumped Yb:CaGdAlO4 (CALGO) laser. The dual-wavelength spectrum is controlled by the pump power and off-axis loss in a laser resonator, arising from the broad emission bandwidth of Yb:CALGO. The OAM beam is obtained by a pair of cylindrical lenses serving as a π/2 convertor for high-order Hermite–Gaussian modes. The stability is verified by the fact that a 1\\hbar OAM beam with two spectral peaks at 1046.1 nm and 1057.2 nm (3.01 THz interval) can steadily operate for more than 3 h. It has great potential for scaling the application of OAM beams in terahertz spectroscopy, high-resolution interferometry, and so on.
Changes in type I collagen following laser welding.
Bass, L S; Moazami, N; Pocsidio, J; Oz, M C; LoGerfo, P; Treat, M R
1992-01-01
Selection of ideal laser parameters for tissue welding is inhibited by poor understanding of the mechanism. We investigated structural changes in collagen molecules extracted from rat tail tendon (> 90% type I collagen) after tissue welding using an 808 nm diode laser and indocyanine green dye applied to the weld site. Mobility patterns on SDS-PAGE were identical in the lasered and untreated tendon extracts with urea or acetic acid. Pepsin incubation after acetic acid extraction revealed a reduction of collagen alpha and beta bands in lasered compared with untreated specimens. Circular dichroism studies of rat tail tendon showed absence of helical structure in collagen from lasered tendon. No evidence for covalent bonding was present in laser-treated tissues. Collagen molecules are denatured by the laser wavelength and parameters used in this study. No significant amount of helical structure is regenerated on cooling. We conclude that non-covalent interactions between denatured collagen molecules may be responsible for the creation of tissue welding.
Bhatta, Krishna M.
1995-05-01
Lasers have been used for symptomatic Benign Prostatic Hyperplasia (BPH) in both contact and non-contact modes with reported success rates equivalent to that of Transurethral Resection of Prostate (TURP). A new high power diode laser (Phototome), capable of delivering up to 50 watts of 1000 nm wavelength laser power via a 1 mm quartz fiber, was used to treat 15 patients with symptomatic BPH. Five patients had acute retention, 3 had long term catheter (7 - 48 months), and 8 had severe prostatism. Spinal anesthesia was used in 11 patients, and 4 patients had local anesthesia and intravenous sedation. Four quadrant coagulation with an angle firing probe delivering 50 watts of laser power for 60 seconds in one quadrant was used as the core of the treatment in 11 patients, contact vaporization of BPH tissue was performed in one patient using a 4.5 mm ball tip was used in one patient and three patients with bladder neck stenosis had bladder neck incision performed using a 1 mm quartz fiber delivering 30 watts of laser power. A foley catheter was left indwelling and removed after 5 - 7 days. All patients except one were catheter free after a mean of 8 days. One patient continued to have severe prostatism and had a TURP performed with good results after 3 months of his laser prostatectomy procedure. AUA symptom scores available in 11 patients was found to be 4 after 1 - 3 months of the initial procedure.
Ishida, Keisuke; Ohta, Takeshi; Miyamoto, Hirotaka; Kumazaki, Takahito; Tsushima, Hiroaki; Kurosu, Akihiko; Matsunaga, Takashi; Mizoguchi, Hakaru
2016-03-01
Multiple patterning ArF immersion lithography has been expected as the promising technology to satisfy tighter leading edge device requirements. One of the most important features of the next generation lasers will be the ability to support green operations while further improving cost of ownership and performance. Especially, the dependence on rare gases, such as Neon and Helium, is becoming a critical issue for high volume manufacturing process. The new ArF excimer laser, GT64A has been developed to cope with the reduction of operational costs, the prevention against rare resource shortage and the improvement of device yield in multiple-patterning lithography. GT64A has advantages in efficiency and stability based on the field-proven injection-lock twin-chamber platform (GigaTwin platform). By the combination of GigaTwin platform and the advanced gas control algorithm, the consumption of rare gases such as Neon is reduced to a half. And newly designed Line Narrowing Module can realize completely Helium free operation. For the device yield improvement, spectral bandwidth stability is important to increase image contrast and contribute to the further reduction of CD variation. The new spectral bandwidth control algorithm and high response actuator has been developed to compensate the offset due to thermal change during the interval such as the period of wafer exchange operation. And REDeeM Cloud™, new monitoring system for managing light source performance and operations, is on-board and provides detailed light source information such as wavelength, energy, E95, etc.
Jang, Hun-jae; Park, Mi-ae; Sirotkin, Fedir V.; Yoh, Jack J.
2013-12-01
The expansion of the laser-induced bubble is the main mechanism in the developed microjet injector. In this study, Nd:YAG and Er:YAG lasers are used as triggers of the bubble formation. The impact of the laser parameters on the bubble dynamics is studied and the performance of the injector is evaluated. We found that the main cause of the differences in the bubble behavior comes from the pulse duration and wavelength. For Nd:YAG laser, the pulse duration is very short relative to the bubble lifetime making the behavior of the bubble close to that of the cavitation bubble, while in Er:YAG case, the high absorption in the water and long pulse duration change the initial behavior of the bubble making it close to a vapor bubble. The contraction and subsequent rebound are typical for cavitation bubbles in both cases. The results show that the laser-induced microjet injector generates velocity which is sufficient for the drug delivery for both laser beams of different pulse duration. We estimate the typical velocity within 30-80 m/s range and the breakup length to be larger than 1 mm suitable for trans-dermal drug injection.
Chaitanya Kumar, S; Parsa, S; Ebrahim-Zadeh, M
2016-01-01
We report a stable, Yb-fiber-laser-based, green-pumped, picosecond optical parametric oscillator (OPO) for the near-infrared based on periodically poled potassium titanyl phosphate (PPKTP) nonlinear crystal, using fan-out grating design and operating near room temperature. The OPO is continuously tunable across 726-955 nm in the signal and 1201-1998 nm in the idler, resulting in a total signal plus idler wavelength coverage of 1026 nm by grating tuning at a fixed temperature. The device generates up to 580 mW of average power in the signal at 765 nm and 300 mW in the idler at 1338 nm, with an overall extraction efficiency of up to 52% and a pump depletion >76%. The extracted signal at 765 nm and idler at 1746 nm exhibit excellent passive power stability better than 0.5% and 0.8% rms, respectively, over 1 h with good beam quality in TEM00 mode profile. The output signal pulses have a Gaussian temporal duration of 13.2 ps, with a FWHM spectral bandwidth of 3.4 nm at 79.5 MHz repetition rate. Power scaling limitations of the OPO due to the material properties of PPKTP are studied.
Lu, Wei; Sun, Jianfeng; Hou, Peipei; Xu, Qian; Xi, Yueli; Zhou, Yu; Zhu, Funan; Liu, Liren
2017-08-01
Performance of satellite laser communications between GEO and LEO satellites can be influenced by background light noise appeared in the field of view due to sunlight or planets and some comets. Such influences should be studied on the ground testing platform before the space application. In this paper, we introduce a simulator that can simulate the real case of background light noise in space environment during the data talking via laser beam between two lonely satellites. This simulator can not only simulate the effect of multi-wavelength spectrum, but also the effects of adjustable angles of field-of-view, large range of adjustable optical power and adjustable deflection speeds of light noise in space environment. We integrate these functions into a device with small and compact size for easily mobile use. Software control function is also achieved via personal computer to adjust these functions arbitrarily. Keywords:
Endoscopic laser treatment for rectosigmoid villous adenoma: factors effecting the results
Brunetaud, Jean Marc; Maunoury, Vincent; Cochelard, Dominique; Boniface, Brigitte
1994-12-01
This present work reports the long term results after endoscopic laser treatment in 474 patients with benign rectosigmoid villous adenomas revealed by biopsy. Two types of wavelength were used: The 1.06 micrometers infrared light from the Nd:YAG laser and the green light from the argon laser or the Nd:YAG frequency doubled laser. In some patients, both wavelengths were used. Treatment was completed in 415 patients. Total tumor destruction was obtained in 92.8% of them, a carcinoma was detected in 6.5% on biopsy specimens obtained during laser treatment, and benign villous tissue persisted in 0.7%. During the average 30 mo. follow up period of the patients with total tumor destruction, 18% had a tumor recurrence. Treatment was well tolerated with a 1.8% complication rate (one perforation, one hemorrhage, and 7 stenosis requiring dilatation). Because treatment is long and difficult and cancer rate is high, endoscopic laser should be limited in patients with a circumferential villous adenoma to nonsurgical candidates. The risk of complication after surgery (some being fatal) has to be balanced against the risk of undetected carcinoma in the other patients and the indication for endoscopic laser treatment should be discussed case by case.
International Nuclear Information System (INIS)
Borowiec, A.; Tiedje, H.F.; Haugen, H.K.
2005-01-01
We present single pulse femtosecond laser ablation threshold measurements of InP obtained by optical, scanning electron, and atomic force microscopy. The experiments were conducted with laser pulses 65-175 fs in duration, in the wavelength range from 400 to 2050 nm, covering the photon energy region above and below the bandgap of InP. The ablation thresholds determined from depth and volume measurements varied from 87 mJ/cm 2 at 400 nm to 250 mJ/cm 2 at 2050 nm. In addition, crater depths and volumes were measured over a range of laser fluences extending well above the ablation threshold
Micro-Welding of Copper Plate by Frequency Doubled Diode Pumped Pulsed Nd:YAG Laser
Nakashiba, Shin-Ichi; Okamoto, Yasuhiro; Sakagawa, Tomokazu; Takai, Sunao; Okada, Akira
A pulsed laser of 532 nm wavelength with ms range pulse duration was newly developed by second harmonic generation of diode pumped pulsed Nd:YAG laser. High electro-optical conversion efficiency more than 13% could be achieved, and 1.5 kW peak power green laser pulse was put in optical fiber of 100 μm in diameter. In micro- welding of 1.0 mm thickness copper plate, a keyhole welding was successfully performed by 1.0 kW peak power at spot diameter less than 200 μm. The frequency doubled pulsed laser improved the processing efficiency of copper welding, and narrow and deep weld bead was stably obtained.
Green-diode-pumped femtosecond Ti:Sapphire laser with up to 450 mW average power.
Gürel, K; Wittwer, V J; Hoffmann, M; Saraceno, C J; Hakobyan, S; Resan, B; Rohrbacher, A; Weingarten, K; Schilt, S; Südmeyer, T
2015-11-16
We investigate power-scaling of green-diode-pumped Ti:Sapphire lasers in continuous-wave (CW) and mode-locked operation. In a first configuration with a total pump power of up to 2 W incident onto the crystal, we achieved a CW power of up to 440 mW and self-starting mode-locking with up to 200 mW average power in 68-fs pulses using semiconductor saturable absorber mirror (SESAM) as saturable absorber. In a second configuration with up to 3 W of pump power incident onto the crystal, we achieved up to 650 mW in CW operation and up to 450 mW in 58-fs pulses using Kerr-lens mode-locking (KLM). The shortest pulse duration was 39 fs, which was achieved at 350 mW average power using KLM. The mode-locked laser generates a pulse train at repetition rates around 400 MHz. No complex cooling system is required: neither the SESAM nor the Ti:Sapphire crystal is actively cooled, only air cooling is applied to the pump diodes using a small fan. Because of mass production for laser displays, we expect that prices for green laser diodes will become very favorable in the near future, opening the door for low-cost Ti:Sapphire lasers. This will be highly attractive for potential mass applications such as biomedical imaging and sensing.
Tahvili, M.S.; Du, L.; Heck, M.J.R.; Nötzel, R.; Smit, M.K.; Bente, E.A.J.M.
2012-01-01
We present an investigation of passive and hybrid mode-locking in Fabry-Pérot type two-section InAs/InP(100) quantum dot lasers that show dual wavelength operation. Over the whole current and voltage range for mode-locking of these lasers, the optical output spectra show two distinct lobes. The two
González-Saldivar, Gerardo; Rojas-Juárez, Sergio; Espinosa-Soto, Itzel; Sánchez-Ramos, Jorge; Jaurieta-Hinojosa, Noel; Ramírez-Estudillo, Abel
2017-11-01
Panretinal photocoagulation (PRP) is the mainstay therapy for proliferative diabetic retinopathy. Pain during and after its application is a complication that affects patients' therapeutic adherence. This study aimed to compare pain perception and patient preference for the 577-nm yellow laser (YL-577) (LIGHTL as 577; LIGHTMED, San Clemente, CA) and the conventional 532-nm green laser (GL-532) (Purepoint Laser; Alcon, Fort Worth, TX) with PRP. A total of 92 patient eyes with proliferative diabetic retinopathy treated with PRP were randomly assigned to receive both GL-532 and YL-577 (184 eyes) - one on each eye, with the order of application randomized, as well. Afterward, verbal rapid answer and visual analogue scale (VAS) scores for pain perception and patient preference were evaluated. VAS score was 7 ± 2 for the GL-532 group compared to 5 ± 3 in the YL-577 group (P = .001). Overall, 75% of the patients preferred YL-577 therapy if they were to receive a second PRP session. The use of YL-577 as an alternative approach for PRP reduces pain perception and is preferred by patients. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:902-905.]. Copyright 2017, SLACK Incorporated.
High-contrast gratings for long-wavelength laser integration on silicon
Sciancalepore, Corrado; Descos, Antoine; Bordel, Damien; Duprez, Hélène; Letartre, Xavier; Menezo, Sylvie; Ben Bakir, Badhise
2014-02-01
Silicon photonics is increasingly considered as the most promising way-out to the relentless growth of data traffic in today's telecommunications infrastructures, driving an increase in transmission rates and computing capabilities. This is in fact challenging the intrinsic limit of copper-based, short-reach interconnects and microelectronic circuits in data centers and server architectures to offer enough modulation bandwidth at reasonable power dissipation. In the context of the heterogeneous integration of III-V direct-bandgap materials on silicon, optics with high-contrast metastructures enables the efficient implementation of optical functions such as laser feedback, input/output (I/O) to active/passive components, and optical filtering, while heterogeneous integration of III-V layers provides sufficient optical gain, resulting in silicon-integrated laser sources. The latest ensure reduced packaging costs and reduced footprint for the optical transceivers, a key point for the short reach communications. The invited talk will introduce the audience to the latest breakthroughs concerning the use of high-contrast gratings (HCGs) for the integration of III-V-on-Si verticalcavity surface-emitting lasers (VCSELs) as well as Fabry-Perot edge-emitters (EELs) in the main telecom band around 1.55 μm. The strong near-field mode overlap within HCG mirrors can be exploited to implement unique optical functions such as dense wavelength division multiplexing (DWDM): a 16-λ100-GHz-spaced channels VCSEL array is demonstrated. On the other hand, high fabrication yields obtained via molecular wafer bonding of III-V alloys on silicon-on-insulator (SOI) conjugate excellent device performances with cost-effective high-throughput production, supporting industrial needs for a rapid research-to-market transfer.
Growth of GaAs “nano ice cream cones” by dual wavelength pulsed laser ablation
Schamp, C. T.; Jesser, W. A.; Shivaram, B. S.
2007-05-01
Harmonic generation crystals inherently offer the possibility of using multiple wavelengths of light in a single laser pulse. In the present experiment, the fundamental (1064 nm) and second harmonic (532 nm) wavelengths from an Nd:YAG laser are focused together on GaAs and GaSb targets for ablation. Incident energy densities up to about 45 J/cm 2 at 10 Hz with substrate temperatures between 25 and 600 °C for durations of about 60 s have been used in an ambient gas pressure of about 10 -6 Torr. The ablated material was collected on electron-transparent amorphous carbon films for TEM analysis. Apart from a high density of isolated nanocrystals, the most common morphology observed consists of a crystalline GaAs cone-like structure in contact with a sphere of liquid Ga, resembling an "ice cream cone", typically 50-100 nm in length. For all of the heterostuctures of this type, the liquid/solid/vacuum triple junction is found to correspond to the widest point on the cone. These heterostructures likely form by preferential evaporation of As from molten GaAs drops ablated from the target. The resulting morphology minimizes the interfacial and surface energies of the liquid Ga and solid GaAs.
Jelger, P; Wang, P; Sahu, J K; Laurell, F; Clarkson, W A
2008-06-23
In this work a volume Bragg grating is used as a wavelength selective element in a high-power cladding-pumped Yb-doped silica fiber laser. The laser produced 138 W of linearly-polarized single-spatial-mode output at 1066 nm with a relatively narrow linewidth of 0.2 nm for approximately 202 W of launched pump power at 976 nm. The beam propagation factor (M(2)) for the output beam was determined to be 1.07. Thermal limitations of volume Bragg gratings are discussed in the context of power scaling for fiber lasers.
Energy Technology Data Exchange (ETDEWEB)
Fabbro, R.; Faral, B.; Virmont, J.; Cottet, F.; Romain, J.P.; Pepin, H.
1985-11-01
In 0.26 ..mu..m wavelength laser experiments that were performed in planar geometry with irradiances between 10/sup 13/ and 10/sup 15/ W/cm/sup 2/, the ablation pressure and the target velocity have been measured using a shock-velocity measurement and the double foil technique, respectively. The conditions are discussed that must be satisfied if the double-foil technique is to give an accurate measurement of the velocity of the dense part of the target. The rocket model has also been improved using a time-dependent applied pressure pulse, in order to accurately describe the relation between ablation pressure, target velocity, and ablated fraction. Pressures up to 50 Mbar have been easily generated since lateral energy transport is rather low with a 0.26 ..mu..m wavelength laser.
Büttner, Lars; Czarske, Jürgen
2003-07-01
We report a method for passive optical directional discrimination in laser-Doppler anemometers. For this purpose frequency-shift elements such as acousto-optic modulators, which are bulky and difficult to align during assembly, have traditionally been employed. We propose to use a quadrature homodyne technique to achieve directional discrimination of the fluid flow without any frequency-shift elements. It is based on the employment of two laser wavelengths, which generate two interference fringe systems with a phase shift of a quarter of the common fringe spacing. Measurement signal pairs with a direction-dependent phase shift of +/- pi/2 are generated. As a robust signal-processing technique, the cross-correlation technique is used. The principles of quadrature homodyne laser-Doppler anemometry are investigated. A setup that provides a constant phase shift of pi/2 throughout the entire measurement volume was achieved with both single-mode and multimode radiation. The directional discrimination was successfully verified with wind tunnel measurements. The complete passive technique offers the potential of building miniaturized measurement heads that can be integrated, e.g., into wind tunnel models.
Short wavelength sources and atoms and ions
International Nuclear Information System (INIS)
Kennedy, E.T.
2008-01-01
The interaction of ionizing radiation with atoms and ions is a key fundamental process. Experimental progress has depended in particular on the development of short wavelength light sources. Laser-plasma and synchrotron sources have been exploited for several decades and most recently the development of short wavelength Free Electron Laser (FEL) sources is revolutionizing the field. This paper introduces laser plasma and synchrotron sources through examples of their use in studies of the interaction of ionizing radiation with atoms and ions, ranging from few-electron atomic and ionic systems to the many-electron high atomic number actinides. The new FEL source (FLASH) at DESY is introduced. (author)
Short-wavelength out-of-band EUV emission from Sn laser-produced plasma
Torretti, F.; Schupp, R.; Kurilovich, D.; Bayerle, A.; Scheers, J.; Ubachs, W.; Hoekstra, R.; Versolato, O. O.
2018-02-01
We present the results of spectroscopic measurements in the extreme ultraviolet regime (7-17 nm) of molten tin microdroplets illuminated by a high-intensity 3 J, 60 ns Nd:YAG laser pulse. The strong 13.5 nm emission from this laser-produced plasma (LPP) is of relevance for next-generation nanolithography machines. Here, we focus on the shorter wavelength features between 7 and 12 nm which have so far remained poorly investigated despite their diagnostic relevance. Using flexible atomic code calculations and local thermodynamic equilibrium arguments, we show that the line features in this region of the spectrum can be explained by transitions from high-lying configurations within the Sn{}8+-Sn{}15+ ions. The dominant transitions for all ions but Sn{}8+ are found to be electric-dipole transitions towards the n = 4 ground state from the core-excited configuration in which a 4p electron is promoted to the 5s subshell. Our results resolve some long-standing spectroscopic issues and provide reliable charge state identification for Sn LPP, which could be employed as a useful tool for diagnostic purposes.
Discovery of new Praseodymium I energy levels with help of green laser light
Energy Technology Data Exchange (ETDEWEB)
Khan, Shamim; Siddiqui, Imran; Tanweer Iqbal, Syed; Windholz, Laurentius [Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A 8010 Graz (Austria)
2012-07-01
The hyperfine structure (hfs) of Praseodymium I spectral lines were experimentally investigated using LIF technique in a hollow cathode discharge lamp. We report here the investigation of 100 spectral lines which resulted in a discovery of 20 new energy levels of even and odd parity. The excitation source is a tunable ring-dye laser system, operated with Coumarin 102. The laser wavelength is tuned to a strong hyperfine component of the investigated spectral line, and fluorescence signals from excited levels are searched. The hfs of the investigated line is recorded by scanning the laser frequency across the investigated region. Magnetic hf interaction constant ''A'' and angular momentum ''J'' of the combining lower and upper levels involved in the formation of the line are evaluated. If one of the combining levels is not known (in most cases upper level), the determined angular momentum ''J'' and hyperfine constant ''A'' are used to identify one of the involved levels (in most cases the lower level) and the energy of the unknown level is determined by using center of mass wave number of line and the energy of the identified level. The level found in this way must explain most of the observed fluorescence wavelengths and the hyperfine structure of the fluorescence lines appearing in FT spectrum.
DEFF Research Database (Denmark)
Duller, G.A.T.; Bøtter-Jensen, L.; Murray, A.S.
2003-01-01
A system designed for measurement of the optically stimulated luminescence (OSL) from individual sand-sized mineral grains has been constructed. Previously, this system was equipped only with a green laser emitting at 532 run, but now an infrared (IR) laser at 830 run has been added. It is now...... possible to interchangeably use the two laser sources for optical stimulation. This is especially valuable for the measurement of feldspars. The power density using the IR laser at the grain is similar to500 W cm(-2), and stimulation for 1 s reduces the OSL signal to near background level. Initial results...
Chakraborty, Arup Lal; Ruxton, Keith; Johnstone, Walter; Lengden, Michael; Duffin, Kevin
2009-06-08
A new fiber-optic technique to eliminate residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy is presented. The modulated laser output is split to pass in parallel through the gas measurement cell and an optical fiber delay line, with the modulation frequency / delay chosen to introduce a relative phase shift of pi between them. The two signals are balanced using a variable attenuator and recombined through a fiber coupler. In the absence of gas, the direct laser intensity modulation cancels, thereby eliminating the high background. The presence of gas induces a concentration-dependent imbalance at the coupler's output from which the absolute absorption profile is directly recovered with high accuracy using 1f detection.
Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE)
Energy Technology Data Exchange (ETDEWEB)
Dobler, Jeremy [Exelis Inc., Fort Wayne, IN (United States); Zaccheo, T. Scott [Exelis Inc., Fort Wayne, IN (United States); Blume, Nathan [Exelis Inc., Fort Wayne, IN (United States); Pernini, Timothy [Exelis Inc., Fort Wayne, IN (United States); Braun, Michael [Exelis Inc., Fort Wayne, IN (United States); Botos, Christopher [Exelis Inc., Fort Wayne, IN (United States)
2016-03-31
This report describes the development and testing of a novel system, the Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE), for Monitoring, Reporting and Verification (MRV) of CO2 at Geological Carbon Storage (GCS) sites. The system consists of a pair of laser based transceivers, a number of retroreflectors, and a set of cloud based data processing, storage and dissemination tools, which enable 2-D mapping of the CO2 in near real time. A system was built, tested locally in New Haven, Indiana, and then deployed to the Zero Emissions Research and Technology (ZERT) facility in Bozeman, MT. Testing at ZERT demonstrated the ability of the GreenLITE system to identify and map small underground leaks, in the presence of other biological sources and with widely varying background concentrations. The system was then ruggedized and tested at the Harris test site in New Haven, IN, during winter time while exposed to temperatures as low as -15 °CºC. Additional testing was conducted using simulated concentration enhancements to validate the 2-D retrieval accuracy. This test resulted in a high confidence in the reconstruction ability to identify sources to tens of meters resolution in this configuration. Finally, the system was deployed for a period of approximately 6 months to an active industrial site, Illinois Basin – Decatur Project (IBDP), where >1M metric tons of CO2 had been injected into an underground sandstone basin. The main objective of this final deployment was to demonstrate autonomous operation over a wide range of environmental conditions with very little human interaction, and to demonstrate the feasibility of the system for long term deployment in a GCS environment.
Spectroscopic Study of Green Tea (Camellia sinensis) Leaves Extraction
Marzuki, A.; Suryanti, V.; Virgynia, A.
2017-04-01
This paper reports the analysis of UV-VIS-NIR absorption spectra of different concentrations of green tea (Camellia sinensis) leaf extract in two different solvent systems (chloroform and ethyl acetate). In those solvents, two different peaks characterizing green tea are observed at different wavelengths, namely 296 nm and 329 nm (extracted in chloroform) and 391 nm and 534 nm (extracted in ethyl acetate). We then investigated the absorption spectra change as function of green tea concentration in both solvents. We found that light absorption increases linearly with the increase of green tea concentration. Different wavelengths, however, respond this change differently. However, the way it changes is wavelength dependence.
A InGaN/GaN quantum dot green (λ=524 nm) laser
Zhang, Meng
2011-01-01
The characteristics of self-organized InGaN/GaN quantum dot lasers are reported. The laser heterostructures were grown on c-plane GaN substrates by plasma-assisted molecular beam epitaxy and the laser facets were formed by focused ion beam etching with gallium. Emission above threshold is characterized by a peak at 524 nm (green) and linewidth of 0.7 nm. The lowest measured threshold current density is 1.2 kA/ cm2 at 278 K. The slope and wall plug efficiencies are 0.74 W/A and ∼1.1%, respectively, at 1.3 kA/ cm 2. The value of T0 =233 K in the temperature range of 260-300 K. © 2011 American Institute of Physics.
Wilmink, Gerald J.; Opalenik, Susan R.; Beckham, Joshua T.; Mackanos, Mark A.; Nanney, Lillian B.; Contag, Christopher H.; Davidson, Jeffrey M.; Jansen, E. Duco
2013-01-01
Laser surgical ablation is achieved by selecting laser parameters that remove confined volumes of target tissue and cause minimal collateral damage. Previous studies have measured the effects of wavelength on ablation, but neglected to measure the cellular impact of ablation on cells outside the lethal zone. In this study, we use optical imaging in addition to conventional assessment techniques to evaluate lethal and sublethal collateral damage after ablative surgery with a free-electron laser (FEL). Heat shock protein (HSP) expression is used as a sensitive quantitative marker of sublethal damage in a transgenic mouse strain, with the hsp70 promoter driving luciferase and green fluorescent protein (GFP) expression (hsp70A1-L2G). To examine the wavelength dependence in the mid-IR, laser surgery is conducted on the hsp70A1-L2G mouse using wavelengths targeting water (OH stretch mode, 2.94 μm), protein (amide-II band, 6.45 μm), and both water and protein (amide-I band, 6.10 μm). For all wavelengths tested, the magnitude of hsp70 expression is dose-dependent and maximal 5 to 12 h after surgery. Tissues treated at 6.45 μm have approximately 4× higher hsp70 expression than 6.10 μm. Histology shows that under comparable fluences, tissue injury at the 2.94-μm wavelength was 2× and 3× deeper than 6.45 and 6.10 μm, respectively. The 6.10-μm wavelength generates the least amount of epidermal hyperplasia. Taken together, this data suggests that the 6.10-μm wavelength is a superior wavelength for laser ablation of skin. PMID:19021444
Borges, Caroline Cristina; Estrela, Carlos; Lopes, Fabiane Carneiro; Palma-Dibb, Regina Guenka; Pecora, Jesus Djalma; De Araújo Estrela, Cyntia Rodrigues; Sousa-Neto, Manoel Damião de
2017-11-01
The objective of this study was to evaluate the antibacterial effect and the ultrastructural alterations of diode laser with different wavelengths (808nm and 970nm) and its association with irrigating solutions (2.5% sodium hypochlorite and 2% chlorhexidine) in root dentin contaminated by a five days biofilm. Thirteen uniradicular teeth were sectioned into 100 dentin intraradicular blocks. Initially, the blocks were immersed for 5min in 17% EDTA and washed with distilled water for 5min, then samples were sterilized for 30min at 120°C. The dentin samples were inoculated with 0.1mL of E. faecalis suspension in 5mL BHI (Brain Heart Infusion) and incubated at 37°C for 5days. After contamination, the specimens were distributed into ten groups (n=10) according to surface treatment: GI - 5mL NaOCl 2.5%, GII - 5mL NaOCl 2.5%+808nm diode (0.1W for 20s), GIII - 5mL NaOCl 2.5%+970nm diode (0.5W for 4s), GIV - 808nm diode (0.1W for 20s), GV - 970nm diode (0.5W for 4s), GVI - CHX 2%, GVII - CHX 2%+808nm diode (0.1W for 20s), GVIII - CHX 2%+970nm diode (0.5W for 4s), GIX - positive control and GX - negative control. Bacterial growth was analyzed by turbidity and optical density of the growth medium by spectrophotometry (nm). Then, the specimens were processed for analysis ultrastructural changes of the dentin surface by SEM. The data was subject to the One-way ANOVA test. GI (77.5±12.1), GII (72.5±12.2), GIII (68.7±8.7), GV (68.3±8.7), GVI (62.0±5.5) and GVII (67.5±3.3) were statistically similar and statistically different from GIV (58.8±25.0), GVIII (59.2±4.0) and control groups (pdiode laser; erosion of the intertubular dentin in blocks submitted to 808nm diode laser irradiation; and an increased erosion of the intertubular dentin when 2.5% NaOCl was associated to the different wavelengths lasers. All the therapeutic protocols were able to reduce the bacterial contingent in dentin blocks, and the association of diode laser and solutions did not significantly improve
Free-space wavelength-multiplexed optical scanner demonstration.
Yaqoob, Zahid; Riza, Nabeel A
2002-09-10
Experimental demonstration of a no-moving-parts free-space wavelength-multiplexed optical scanner (W-MOS) is presented. With fast tunable lasers or optical filters and planar wavelength dispersive elements such as diffraction gratings, this microsecond-speed scanner enables large several-centimeter apertures for subdegree angular scans. The proposed W-MOS design incorporates a unique optical amplifier and variable optical attenuator combination that enables the calibration and modulation of the scanner response, leading to any desired scanned laser beam power shaping. The experimental setup uses a tunable laser centered at 1560 nm and a 600-grooves/mm blazed reflection grating to accomplish an angular scan of 12.92 degrees as the source is tuned over an 80-nm bandwidth. The values for calculated maximum optical beam divergance, required wavelength resolution, beam-pointing accuracy, and measured scanner insertion loss are 1.076 mrad, 0.172 nm, 0.06 mrad, and 4.88 dB, respectively.
Luminescent properties of Tb3+- doped TeO2-WO3-GeO2 glasses for green laser applications
Subrahmanyam, T.; Rama Gopal, K.; Padma Suvarna, R.; Jamalaiah, B. C.; Vijaya Kumar, M. V.
2018-06-01
Different concentrations of Tb3+ -doped oxyfluoro tellurite (TWGTb) glasses were prepared by conventional melt quenching technique and characterized for green laser applications. The Judd-Ofelt theory was applied to evaluate various spectroscopic and radiative parameters. The TWGTb glasses exhibit 5D3 → 7F5-3 and 5D4 → 7F6-0 transitions when excited at 316 nm radiation. The variation of intensity of 5D4 → 7F5 (Green) and 5D3 → 7F4 (Blue) transitions and the green to blue (IG/IB) intensity ratios were studied as a function of Tb3+ ions concentration. The laser characteristic parameters such as effective bandwidth (Δλeff), stimulated emission cross-section (σe), gain bandwidth (σe × Δλeff) and optical gain (σe × τR) were determined using the three phenomenological Judd-Ofelt intensity parameters. The fluorescence decay profiles of 5D4 metastable level exhibit single-exponential nature for all the samples. Based on the experimental results we suggest that the 1.0 mol% of Tb3+ -doped TWGTb glass could be a suitable laser host material to emit intense green luminescence at 545 nm.
DEFF Research Database (Denmark)
Müller, André; Jensen, Ole Bjarlin; Hasler, Karl-Heinz
2012-01-01
In order to increase the power of visible diode laser systems in an efficient manner, we propose spectral beam combining with subsequent sum-frequency generation. We show that this approach, in comparison with second harmonic generation of single emitters, can enhance the available power signific......In order to increase the power of visible diode laser systems in an efficient manner, we propose spectral beam combining with subsequent sum-frequency generation. We show that this approach, in comparison with second harmonic generation of single emitters, can enhance the available power...... significantly. By combining two distributed Bragg reflector tapered diode lasers we achieve a 2.5–3.2 fold increase in power and a maximum of 3.9 W of diffraction-limited green light. At this power level, green diode laser systems have a high application potential, e.g., within the biomedical field. Our concept...
Random laser emission at dual wavelengths in a donor-acceptor dye mixture solution
Directory of Open Access Journals (Sweden)
Sunita Kedia
Full Text Available The work was aimed to generate random laser emissions simultaneously at two wavelengths in a weakly scattering system containing mixture of binary dyes, rhodamine-B (Rh-B and oxazine-170 (O-170 dispersed with ZnO nano-particles serving as scattering centres. Random lasing performances for individual Rh-B dye were extensively studied for varying small signal gain/scatterer density and we found lasing threshold to significantly depend upon number density of dispersed nano-particles. In spite of inefficient pumping, we demonstrated possibility of random lasing in O-170 dye solution on account of resonance energy transfer from Rh-B dye which served as donor. At optimum concentrations of fluorophores and scatterer in dye mixture solution, incoherent random lasing was effectively attained simultaneously at two wavelengths centered 90 nm apart. Dual-emission intensities, lasing thresholds and rate of amplifications could be controlled and made equivalent for both donor and acceptor in dye mixture solution by appropriate choice of concentrations of dyes and scatterers. Keywords: Random lasing, Energy transfer, Rhodamine-B, Oxazine-170, Zinc oxide
Lee, Eun-Gu; Mun, Sil-Gu; Lee, Sang Soo; Lee, Jyung Chan; Lee, Jong Hyun
2015-01-12
We report a cost-effective transmitter optical sub-assembly using a monolithic four-wavelength vertical-cavity surface-emitting laser (VCSEL) array with 100-GHz wavelength spacing for future-proof mobile fronthaul transport using the data rate of common public radio interface option 6. The wavelength spacing is achieved using selectively etched cavity control layers and fine current adjustment. The differences in operating current and output power for maintaining the wavelength spacing of four VCSELs are fiber without any dispersion-compensation techniques.
International Nuclear Information System (INIS)
Rakhman, A.; Hafez, M.; Nanda, S.; Benmokhtar, F.; Camsonne, A.; Cates, G.D.; Dalton, M.M.; Franklin, G.B.; Friend, M.; Michaels, R.W.; Nelyubin, V.; Parno, D.S.; Paschke, K.D.; Quinn, B.P.
2016-01-01
A high-finesse Fabry–Perot cavity with a frequency-doubled continuous wave green laser (532 nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064 nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO_3 crystal. The maximum achieved green power at 5 W infrared pump power is 1.74 W with a total conversion efficiency of 34.8%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7 kW with a corresponding enhancement of 3800. The polarization transfer function has been measured in order to determine the intra-cavity circular laser polarization within a measurement uncertainty of 0.7%. The PREx experiment at Jefferson Lab used this system for the first time and achieved 1.0% precision in polarization measurements of an electron beam with energy and current of 1.06 GeV and 50 μA.
Energy Technology Data Exchange (ETDEWEB)
Rakhman, A., E-mail: rahim@ornl.gov [Syracuse University, Department of Physics, Syracuse, NY 13244 (United States); Research Accelerator Division, Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Hafez, M. [Old Dominion University, Applied Research Center, Norfolk, VA 23529 (United States); Nanda, S. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Benmokhtar, F. [Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213 (United States); Duquesne University, Pittsburgh, PA 15282 (United States); Camsonne, A. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Cates, G.D. [University of Virginia, Department of Physics, Charlottesville, VA 22904 (United States); Dalton, M.M. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); University of Virginia, Department of Physics, Charlottesville, VA 22904 (United States); Franklin, G.B. [Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213 (United States); Friend, M. [Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213 (United States); High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki (Japan); Michaels, R.W. [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States); Nelyubin, V. [University of Virginia, Department of Physics, Charlottesville, VA 22904 (United States); Parno, D.S. [Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213 (United States); University of Washington, Center for Experimental Nuclear Physics and Astrophysics and Department of Physics, Seattle, WA 98195 (United States); Paschke, K.D. [University of Virginia, Department of Physics, Charlottesville, VA 22904 (United States); Quinn, B.P. [Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213 (United States); and others
2016-06-21
A high-finesse Fabry–Perot cavity with a frequency-doubled continuous wave green laser (532 nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064 nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO{sub 3} crystal. The maximum achieved green power at 5 W infrared pump power is 1.74 W with a total conversion efficiency of 34.8%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7 kW with a corresponding enhancement of 3800. The polarization transfer function has been measured in order to determine the intra-cavity circular laser polarization within a measurement uncertainty of 0.7%. The PREx experiment at Jefferson Lab used this system for the first time and achieved 1.0% precision in polarization measurements of an electron beam with energy and current of 1.06 GeV and 50 μA.
Intense green emission from Tb3+- doped Teo2-Wo3-Geo2 glasses
Subrahmanyam, Tallam; Gopal, Kotalo Rama; Suvarna, Reniguntla Padma; Jamalaiah, Bungala Chinna
2018-04-01
Tb3+ -doped oxyfluoro tellurite (TWGTb) glasses were prepared by conventional melt quenching technique. The Judd-Ofelt theory has been applied to evaluate the Ωλ (λ=2,4,6) intensity parameters. The TWGTb glasses exhibit 5D3 → 7F5-3 and 5D4 → 7F6-0 transitions when excited at 316 nm wavelength. The variation of intensity of 5D4 → 7F5 (Green) and 5D3 → 7F4 (Blue) transitions and the green to blue (IG/IB) intensity ratios were studied as a function of Tb3+ ions concentration. The laser characteristic parameters such as effective bandwidth (Δλeff), stimulated emission cross-section (σe), gain bandwidth (σe×Δλeff) and optical gain (σe×τR) were determined using the emission spectra and radiative parameters. The luminescence decay profiles exhibit single-exponential nature for all the samples. Based on the experimental results we suggest that the 1.0 mol% of Tb3+-doped TWGTb glass could be the suitable laser host materials to emit intense green luminescence at 545 nm.
International Nuclear Information System (INIS)
Setser, D.W.
1987-01-01
There are several potential schemes for efficiently generating high concentrations of the first electronically excited state of nitrogen, N 2 (A 3 Σ/sub u/ + , 6.2 eV) by either chemical or electrical pumping. The goal of this proposal is to study ways of utilizing the energy of the N 2 (A) molecules for developing efficient, short wavelength gas lasers. Such lasers are of potential interest for laser fusion. The authors report both excitation-transfer and dissociative excitation-transfer reactions of N 2 (A) that yield electronically-excited diatomic molecules as products. 25 refs
Experimental study of laser acceleration of planar targets at the wavelength 0.26 μm
International Nuclear Information System (INIS)
Fabbro, R.; Faral, B.; Cottet, F.; Romain, J.P.
1984-01-01
The main characteristics of accelerated aluminum targets, which are the target velocity, the uniformity of the acceleration and the backside temperature have been studied in laser experiments performed at wavelength 0.26 μm with an absorbed flux of a few 10 13 W/cm 2 , in 400-ps pulse duration by using the double-foil technique and an optical pyrometry diagnostic: The ablation pressure was inferred from the velocity measurements. The uniformity of the acceleration was shown to be controlled by the hot spots in the focal spot, and the importance of studying the smoothing of laser inhomogeneities for accelerated targets with large ablated fractions was emphasized. The observed dependence of the backside temperature as a function of the initial foil thickness is discussed in the light of shock wave heating and radiative heating
Batishche, Sergei; Englezis, Apostolis; Gorovets, Tatiana; Kouzmouk, Andrei; Pilipenka, Uladzimir; Pouli, Paraskevi; Tatur, Hennady; Totou, Garyfallia; Ukhau, Viktar
2005-07-01
In the present study, a newly developed one-beam IR-UV laser cleaning system is presented. This system may be used for different applications in diverse fields, such as outdoors stonework conservation and canvas paintings restoration. The simultaneous use of the fundamental radiation of a Q-switched Nd:YAG laser at 1064 nm and its third harmonic at 355 nm was found appropriate to clean pollution crusts, while ensuring that no discoloration ("yellowing") would occur. The optimum ratio of UV to IR wavelengths in the final cleaning beam was investigated. In parallel, the same system was tested in diverse applications, such as the removal of bonding glues from duplicated canvases. The optimum laser parameters were investigated both on technical samples as well as on original paintings.
Wavelength mismatch effect in electromagnetically induced absorption
International Nuclear Information System (INIS)
Bharti, Vineet; Wasan, Ajay; Natarajan, Vasant
2016-01-01
We present a theoretical investigation of the phenomenon of electromagnetically induced absorption (EIA) in a 4-level system consisting of vee and ladder subsystems. The four levels are coupled using one weak probe field, and two strong control fields. We consider an experimental realization using energy levels of Rb. This necessitates dealing with different conditions of wavelength mismatch—near-perfect match where all three wavelengths are approximately equal; partial mismatch where the wavelength of one control field is less than the other fields; and complete mismatch where all three wavelengths are unequal. We present probe absorption profiles with Doppler averaging at room temperature to account for experiments in a room temperature Rb vapor cell. Our analysis shows that EIA resonances can be studied using Rydberg states excited with diode lasers. - Highlights: • Wavelength mismatch effect is investigated in electromagnetically induced absorption (EIA). • An experimental realization of 4-level vee + ladder system using energy levels of rubidium atom is presented. • EIA resonances are studied under different conditions of wavelength mismatch. • Possibility of observation of EIA using Rydberg states excited with diode lasers.
Wavelength mismatch effect in electromagnetically induced absorption
Energy Technology Data Exchange (ETDEWEB)
Bharti, Vineet [Department of Physics, Indian Institute of Science, Bangalore 560012 (India); Wasan, Ajay [Department of Physics, Indian Institute of Technology, Roorkee 247667 (India); Natarajan, Vasant [Department of Physics, Indian Institute of Science, Bangalore 560012 (India)
2016-07-15
We present a theoretical investigation of the phenomenon of electromagnetically induced absorption (EIA) in a 4-level system consisting of vee and ladder subsystems. The four levels are coupled using one weak probe field, and two strong control fields. We consider an experimental realization using energy levels of Rb. This necessitates dealing with different conditions of wavelength mismatch—near-perfect match where all three wavelengths are approximately equal; partial mismatch where the wavelength of one control field is less than the other fields; and complete mismatch where all three wavelengths are unequal. We present probe absorption profiles with Doppler averaging at room temperature to account for experiments in a room temperature Rb vapor cell. Our analysis shows that EIA resonances can be studied using Rydberg states excited with diode lasers. - Highlights: • Wavelength mismatch effect is investigated in electromagnetically induced absorption (EIA). • An experimental realization of 4-level vee + ladder system using energy levels of rubidium atom is presented. • EIA resonances are studied under different conditions of wavelength mismatch. • Possibility of observation of EIA using Rydberg states excited with diode lasers.
Efficient phase locking of two dual-wavelength fiber amplifiers by an all-optical self-feedback loop
Lei, Bing; Chen, Keshan; Yao, Tianfu; Shi, Jianhua; Hu, Haojun
2017-10-01
Efficient phase locking of two dual-wavelength fiber amplifiers has been demonstrated by using a self-feedback coupling and intracavity filtering configuration, and the effect of bandwidth and wavelength spacing on their phase locking performances have been investigated in experiment. Two independent fiber lasers with different operating wavelength were combined incoherently by a 3 dB fiber coupler to form a dual-wavelength seed source laser, which was injected into the fiber amplifiers' coupling array through the self-feedback loop. The effect of bandwidth and wavelength spacing was researched by altering the seed laser's pump power and operating wavelengths respectively. As long as the feedback loop and the single-mode fiber filtering configuration were well constructed in the unidirectional ring laser cavity, stable phase locking states and high fringe visibility interference patterns could always be obtained in our experiment. When the spacing of two operating wavelength was varied from 1.6 nm to 19.6 nm, the fringe visibility decreased slightly with the increase of wavelength spacing, and the corresponding fringe visibility was always larger than 0.6. In conclusion, we believe that efficient phase locking of several multi-wavelength laser sources is also feasible by passive self-adjusting methods, and keeping the component laser beams' phase relationship stable and fixed is more important than controlling their operating wavelengths.
Jung, E.
1984-05-01
A color recording unit was designed for output and control of digitized picture data within computer controlled reproduction and picture processing systems. In order to get a color proof picture of high quality similar to a color print, together with reduced time and material consumption, a photographic color film material was exposed pixelwise by modulated laser beams of three wavelengths for red, green and blue light. Components of different manufacturers for lasers, acousto-optic modulators and polygon mirrors were tested, also different recording methods as (continuous tone mode or screened mode and with a drum or flatbed recording principle). Besides the application for the graphic arts - the proof recorder CPR 403 with continuous tone color recording with a drum scanner - such a color hardcopy peripheral unit with large picture formats and high resolution can be used in medicine, communication, and satellite picture processing.
International Nuclear Information System (INIS)
Nicolli Filho, Walter Domingos; Picon, Luciana Christofolini; Okamoto, Tetuo; Cardenuto, Ney
1993-01-01
A histological study on healing of extraction wounds following laser irradiation, using a green He-Ne laser, was carried out in rats. The results suggest that this kind of treatment has no significant beneficial effect on bony wound healing. Proliferation of fibroblasts and formation of trabecular osteoid were found to be not more pro eminent within the irradiated group. (author)
Auteri, Joseph S.; Jeevanandam, Valluvan; Oz, Mehmet C.; Libutti, Steven K.; Kirby, Thomas J.; Smith, Craig R.; Treat, Michael R.
1990-06-01
A major obstacle to lung transplantation and combined heart- lung transplantation is dehiscence of the tracheobronchial anastomosis. We explored the possibility of laser welded anastomoses in canine tracheas in vivo. Laser anastomoses were performed on three-quarter circumferential anterior tracheotomies. A continous wave diode laser (808 +1 nm) at a power density of 9.6 watts/cm was used. Human fibrinogen was mixed with indocyanine green dye (ICG, max absorbance 805 nm) and applied to the anastomosis site prior to laser exposure. Animals were sacrificed at 0, 21 and 28 days post-operatively. At sacrifice weld bursting pressures were measured by raising intratracheal pressure using forced ventilation via an endotracheal tube. Sutured and laser welded anastomoses had similar bursting pressures, and exhibited satisfactory histologic evidence of healing. However, compared to polypropylene sutured controls, the laser welded anastomoses exhibited less peritracheal inflammatory reaction and showed visibly smoother luminal surfaces at 21 and 28 days post- operatively. Tracheal anastomosis using ICG dye enhanced fibrinogen combined with the near-infrared diode laser is a promising extension of the technology of laser tissue fusion and deserves further study.
International Nuclear Information System (INIS)
Zheng Yu; Tian Jin-Rong; Dong Zi-Kai; Xu Run-Qin; Li Ke-Xuan; Song Yan-Rong
2017-01-01
A phase-locked bound state soliton with dual-wavelength is observed experimentally in a passively mode-locked Er-doped fiber (EDF) laser with a fiber loop mirror (FLM). The pulse duration of the soliton is 15 ps and the peak-to-peak separation is 125 ps. The repetition rate of the pulse sequence is 3.47 MHz. The output power is 11.8 mW at the pump power of 128 mW, corresponding to the pulse energy of 1.52 nJ. The FLM with a polarization controller can produce a comb spectrum, which acts as a filter. By adjusting the polarization controller or varying the pump power, the central wavelength of the comb spectrum can be tuned. When it combines with the reflective spectrum of the fiber Bragg grating, the total spectrum of the cavity can be cleaved into two parts, then the bound state soliton with dual-wavelength at 1549.7 nm and 1550.4 nm is obtained. (paper)
International Nuclear Information System (INIS)
Mukhopadhyay, P. K.; Ranganathan, K.; George, J.; Nathan, T. P. S.; Alsous, M. B.
2007-01-01
We report intracavity second harmonic (at 532 nm) generation in passively Q-switched mode-locked Nd: YVO4 laser. The width of a typical Q-switched envelope of the mode locked pulses for the green laser was around 65 ± 5 ns and the repetition rate for the mode locked pulses was 400 MHz. The intracavity frequency doubling significantly improves the depth of modulation of the mode locked pulses. The peak power of a single mode locked green pulse near the center of the Q-switched envelope was estimated to be more than 2kw and the average green power was 6 times higher than the CW green power at an incident diode pump power of 6W. (author)
Energy Technology Data Exchange (ETDEWEB)
Voitovich, A.P.; Kalinov, V.S.; Mikhnov, S.A.; Ovseichuk, S.I.
1987-06-01
The spectral and energy characteristics of lasers utilizing lithium fluoride with F2 and F3(+) color centers in transverse and longitudinal pumping schemes are studied. The feasibility of obtaining stable narrow-band radiation in the 510-570 nm range using a selective resonator is demonstrated. Consideration is given to the effect of lithium-fluoride crystal processing by excimer laser radiation at a wavelength of 308 nm on the spectroscopic and lasing characteristics of the F3(+) color center. After this processing, the laser efficiency in the green spectral region increases by more than a factor of two (reaching an efficiency of 14 percent). 7 references.
Reactions of N2(A3Σ/sub u/+) and candidates for short wavelength lasers
International Nuclear Information System (INIS)
Setser, D.W.
1987-01-01
This proposal is a request for a one year renewal of a contract with the Univ. of California (Lawrence Livermore Laboratory). The proposed experiments are directed towards investigation of possible short-wavelength laser candidate molecules that can be pumped via excitation-transfer reactions with N 2 (A 3 Σ/sub u/ + ) molecules. We will continue our flowing-afterglow experiments to characterize the excitation-transfer collisions between N 2 (A) and promising acceptor diatomic molecules (radicals). We also will extend the studies to include excitation-transfer to Cd and to S atoms. For some chemical systems, a pulsed N 2 (A) source would be very convenient for kinetic measurements and we propose to develop a pulsed N 2 (A) source. During the first year, we have shown that the excitation-transfer reaction between N 2 (A) and SO(X) provides a possible laser candidate. Therefore, we propose to start a program to study the quenching and relaxation kinetics of the SO(A 3 PI) molecule, using pulsed laser excitation techniques to generate specific levels of SO(A 3 PI)
International Nuclear Information System (INIS)
Levermore, C.D.; Caflisch, R.E.; Wood, L.L.
1977-10-01
Longer wavelength (e.g., lambda = 10.5 μm) laser radiation generates relatively large fluxes of superthermal electrons that penetrate and preheat the cores of such pellets at early times in their implosion history, precluding their efficient subsequent compression. It has been proposed to separate the outermost shell of such pellets (onto which the laser light is directed) from its inner regions by a vacuum layer, thereby ''insulating'' these inner portions from superthermal electron degradation. We consider this proposal analytically and computationally, and find it to be questionable, due to the rapid penetration of the vacuum insulation layer by plasma streamers from the laser heated shells, which are accelerated to velocities of the order of those of the superthermal electrons by an electrostatic analog of the Rayleigh-Taylor instability. Results of such considerations are presented. The results developed also apply to a variety of formally similar phenomena, ranging from the relativistic edge of supernova photospheres to diode breakdown in REB machines
Directory of Open Access Journals (Sweden)
Salwa Yammine
2018-01-01
Full Text Available Objective. Diode lasers have multiple indications in everyday dental practice. They allow carrying out incisions, coagulation of soft tissue, and Low-Level Laser Therapy. The goal of this study is to compare histologically the tissue interaction zones and edges of an induced laser incision on rabbits’ tongues with three different wavelengths of 810, 940, and 980 nm in continuous mode. Methods. Fourteen male rabbits were divided into six groups. Each animal underwent three incisions of 10 mm length on the right ventral face of the tongue, carried out in continuous mode with three diode lasers with different wavelengths of 810, 940, and 980 nm. Rabbits were sacrificed at 0, 1, 2, 6, and 15 hours and 14 days. Five rabbits were sacrificed at 0 hours and 2 hours and one rabbit was sacrificed at 1, 6, and 15 hours and at 14 days. The appearance of neutrophils marked the onset time of the inflammatory reaction. Histological study of the incisions was chosen to evaluate the edges and to measure the depth and width of carbonization and necrotic and inflammatory zones. Healing was evaluated at 14 days. Friedman test was used to assess statistical differences between groups. Results. In the experimental adopted conditions, the carbonization zone was marked by degradation of vacuoles and an elongation of nuclei and was observed on the edges of incisions. Carbonization and necrotic and inflammatory zones were measured for rabbits sacrificed at 0, 1, 2, 6, and 15 hours but the onset of inflammation zone marked by the infiltration of neutrophils did not appear before 6 hours. The neutrophils infiltration was higher at 15 hours than at 6 hours. Complete healing was shown at 14 days. According to the time for the regularity of the edges, the interpretation was qualitative without a statistical test. The statistical analysis of the three different diode lasers in this study showed nonsignificant difference between the different groups for the depth (p=0
DEFF Research Database (Denmark)
Clausen, Anders; Hu, Hao; Ye, Feihong
2015-01-01
Increasing the capacity of optical networks while have the objective of lowering the total consumed energy per bit is challenging. By exploiting several dimensions, i.e. wavelength, space, time, polarisation and multilevel modulation simultaneously, a single laser can offer formidable capacity pe...... performance with potentially reduced energy consumption per bit. Up to 43 Tbit/s has been demonstrated....
Estimates of SASE power in the short wavelength region
International Nuclear Information System (INIS)
Kim, Kwang-Je.
1992-03-01
Given a sufficiently bright electron beam, the self-amplified-spontaneous emission (SASE) can provide gigawatts of short wavelength coherent radiation. The advantages of SASE approach are that is requires neither optical cavity nor an imput seed laser. In this note, we estimate the peak power performance of SASE for wavelengths shorter than 1000 Angstrom. At each wavelength, we calculate the saturated power from a uniform parameter undulator and the enhanced power from a tapered undulator. The method described here is an adaptation of that discussed by L.H. Yu, who discussed the harmonic generation scheme with seeded laser, to the case of SASE
Carrier transport in THz quantum cascade lasers: Are Green's functions necessary?
International Nuclear Information System (INIS)
Matyas, A; Jirauschek, C; Kubis, T; Lugli, P
2009-01-01
We have applied two different simulation models for the stationary carrier transport and optical gain analysis in resonant phonon depopulation THz Quantum Cascade Lasers (QCLs), based on the semiclassical ensemble Monte Carlo (EMC) and fully quantum mechanical non-equilibrium Green's functions (NEGF) method, respectively. We find in the incoherent regime near and above the threshold current a qualitative and quantitative agreement of both methods. Therefore, we show that THz-QCLs can be successfully optimized utilizing the numerically efficient EMC method.
Vu, Thi N.; Klehr, Andreas; Sumpf, Bernd; Hoffmann, Thomas; Liero, Armin; Tränkle, Günther
2016-03-01
A master oscillator power amplifier system emitting alternatingly at two neighbored wavelengths around 965 nm is presented. As master oscillator (MO) a Y-branch DFB-laser is used. The two branches, which can be individually controlled, deliver the two wavelengths needed for a differential absorption measurement of water vapor. Adjusting the current through the DFB sections, the wavelength can be adjusted with respect to the targeted either "on" or "off" resonance, respectively wavelength λon or wavelength λoff. The emission of this laser is amplified in a tapered amplifier (TA). The ridge waveguide section of the TA acts as optical gate to generate short pulses with duration of 8 ns at a repetition rate of 25 kHz, the flared section is used for further amplification to reach peak powers up to 16 W suitable for micro-LIDAR (Light Detection and Ranging). The necessary pulse current supply user a GaN-transistor based driver electronics placed close to the power amplifier (PA). The spectral properties of the emission of the MO are preserved by the PA. A spectral line width smaller than 10 pm and a side mode suppression ratio (SMSR) of 37 dB are measured. These values meet the demands for water vapor absorption measurements under atmospheric conditions.
Breaks in plasmid DNA strand induced by laser radiation at a wavelength of 193 nm
International Nuclear Information System (INIS)
Gurzadyan, G.G.; Shul'te Frolinde, D.
1996-01-01
DNA of plasmid pB322 irradiated with laser at a wavelength of 193 nm was treated with an extract containing proteins from E.coli K12 AB1157 (wild-type). The enzymes were found to produce single- and double-strand DNA breaks, which was interpreted as a transformation of a portion of cyclobutane pyrimidine dimers and (6-4) photoproducts into nonrepairable single-strand DNA breaks. The products resulted from ionization of DNA, in particular, single-strand breaks, transform to double-strand breaks. A comparison of these data with the data on survival of plasmid upon transformation of E.coli K12 AB1157 enables one to assess the biological significance of single- and double-strand breaks. The inactivation of the plasmid is mainly determined by the number of directly formed laser-induced single-strand breaks. 26 refs.; 2 figs
Experimental study of laser acceleration of planar targets at the wavelength 0. 26. mu. m
Energy Technology Data Exchange (ETDEWEB)
Fabbro, R.; Faral, B.; Cottet, F.; Romain, J.P.
1984-12-01
The main characteristics of accelerated aluminum targets, which are the target velocity, the uniformity of the acceleration and the backside temperature have been studied in laser experiments performed at wavelength 0.26 ..mu..m with an absorbed flux of a few 10/sup 13/ W/cm/sup 2/, in 400-ps pulse duration by using the double-foil technique and an optical pyrometry diagnostic: The ablation pressure was inferred from the velocity measurements. The uniformity of the acceleration was shown to be controlled by the hot spots in the focal spot, and the importance of studying the smoothing of laser inhomogeneities for accelerated targets with large ablated fractions was emphasized. The observed dependence of the backside temperature as a function of the initial foil thickness is discussed in the light of shock wave heating and radiative heating.
X-ray spectrum emitted by a laser-produced cerium plasma in the 7.5 to 12 A wavelength range
International Nuclear Information System (INIS)
Doron, R.; Behar, E.; Fraenkel, M.; Mandelbaum, P.; Schwob, J.L.; Zigler, A.
2001-01-01
A highly stripped cerium (Z = 58) plasma is produced by irradiating a solid cerium target with an intense short laser pulse. The X-ray spectrum emitted from the plasma is recorded in the 7.5-12 A wavelength range using a flat RAP crystal spectrometer. Ab-initio calculations using the RELAC relativistic computer code, as well as isoelectronic trends deduced from previous works, together with spectra obtained under different laser beam focusing conditions, are all employed for the identification of the spectral lines and features emitted by various ions from Fe-like Ce 32+ to As-like Ce 25+ . The technique of comparing spectra obtained using different laser intensities is also employed to confirm or to resolve some ambiguous identifications of spectral features in the spectrum of a laser-produced lanthanum plasma studied in a previous work. (orig.)
X-ray spectrum emitted by a laser-produced cerium plasma in the 7.5 to 12 A wavelength range
Energy Technology Data Exchange (ETDEWEB)
Doron, R.; Behar, E.; Fraenkel, M.; Mandelbaum, P.; Schwob, J.L.; Zigler, A. [Hebrew Univ., Jerusalem (Israel). Racah Inst. of Physics; Faenov, A.Ya.; Pikuz, T.A. [Multicharged Ion Spectra Data Center, VNIIFTRI, Mendeleevo (Russian Federation)
2001-01-01
A highly stripped cerium (Z = 58) plasma is produced by irradiating a solid cerium target with an intense short laser pulse. The X-ray spectrum emitted from the plasma is recorded in the 7.5-12 A wavelength range using a flat RAP crystal spectrometer. Ab-initio calculations using the RELAC relativistic computer code, as well as isoelectronic trends deduced from previous works, together with spectra obtained under different laser beam focusing conditions, are all employed for the identification of the spectral lines and features emitted by various ions from Fe-like Ce{sup 32+} to As-like Ce{sup 25+}. The technique of comparing spectra obtained using different laser intensities is also employed to confirm or to resolve some ambiguous identifications of spectral features in the spectrum of a laser-produced lanthanum plasma studied in a previous work. (orig.)
Stephens, Michelle S.; Simonds, Brian J.; Yung, Christopher S.; Conklin, Davis; Livigni, David J.; Oliva, Alberto Remesal; Lehman, John H.
2018-05-01
Multi-wall carbon nanotube coatings are used as broadband, low-reflectance absorbers for bolometric applications and for stray light control. They are also used as high emittance blackbody radiators. Irradiation of single wall carbon nanotubes with ultraviolet (UV) laser light has been shown to remove amorphous carbon debris, but there have been few investigations of the interaction of UV light with the more complex physics of multi-wall carbon nanotubes. We present measurements of reflectance and surface morphology before and after exposure of multi-wall carbon nanotube coatings to 248 nm UV laser light. We show that UV exposure reduces the reflectivity at wavelengths below 600 nm and present modeling of the thermal cycling the UV exposure causes at the surface of the carbon nanotubes. This effect can be used to flatten the spectral shape of the reflectivity curve of carbon nanotube absorber coatings used for broadband applications. Finally, we find that the effect of UV exposure depends on the nanotube growth process.
Energy Technology Data Exchange (ETDEWEB)
McConnell, Gail [Centre for Biophotonics, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow, G4 0NR (United Kingdom)
2005-08-07
Intensity correlations of a Ti : sapphire, Kr/Ar and a white-light supercontinuum were performed to quantify the typical signal amplitude fluctuations and hence ascertain the comparative output stability of the white-light supercontinuum source for confocal laser scanning microscopy (CLSM). Intensity correlations across a two-pixel sample (n = 1000) of up to 98%, 95% and 94% were measured for the Ti : sapphire, Kr/Ar and white-light supercontinuum source, respectively. The white-light supercontinuum noise level is therefore acceptable for CLSM, with the added advantage of wider wavelength flexibility over traditional CLSM excitation sources. The relatively low-noise white-light supercontinuum was then used to perform multiple wavelength sequential CLSM of guinea pig detrusor to confirm the reliability of the system and to demonstrate system flexibility.
Multi-wavelength speckle reduction for laser pico-projectors using diffractive optics
Thomas, Weston H.
Personal electronic devices, such as cell phones and tablets, continue to decrease in size while the number of features and add-ons keep increasing. One particular feature of great interest is an integrated projector system. Laser pico-projectors have been considered, but the technology has not been developed enough to warrant integration. With new advancements in diode technology and MEMS devices, laser-based projection is currently being advanced for pico-projectors. A primary problem encountered when using a pico-projector is coherent interference known as speckle. Laser speckle can lead to eye irritation and headaches after prolonged viewing. Diffractive optical elements known as diffusers have been examined as a means to lower speckle contrast. Diffusers are often rotated to achieve temporal averaging of the spatial phase pattern provided by diffuser surface. While diffusers are unable to completely eliminate speckle, they can be utilized to decrease the resultant contrast to provide a more visually acceptable image. This dissertation measures the reduction in speckle contrast achievable through the use of diffractive diffusers. A theoretical Fourier optics model is used to provide the diffuser's stationary and in-motion performance in terms of the resultant contrast level. Contrast measurements of two diffractive diffusers are calculated theoretically and compared with experimental results. In addition, a novel binary diffuser design based on Hadamard matrices will be presented. Using two static in-line Hadamard diffusers eliminates the need for rotation or vibration of the diffuser for temporal averaging. Two Hadamard diffusers were fabricated and contrast values were subsequently measured, showing good agreement with theory and simulated values. Monochromatic speckle contrast values of 0.40 were achieved using the Hadamard diffusers. Finally, color laser projection devices require the use of red, green, and blue laser sources; therefore, using a
International Nuclear Information System (INIS)
Lu Jun; Liu Yan-Hua; Zhao Gang; Hu Xiao-Peng; Zhu Shi-Ning
2012-01-01
High-power cw green laser radiation is generated by intra-cavity frequency doubling of a diode-pumped Nd:GdVO 4 laser with a MgO-doped periodically-poled LiNbO 3 (MgO:PPLN) crystal at room temperature. An average power of 2.4 W at 0.53 μm is obtained under the pump 15 W at 808 nm, corresponding to an overall optical-to-optical conversion efficiency of 16%. The M 2 factor of the green beam is 3.90 and 1.34 for the horizontal and vertical direction, respectively. In addition, the power fluctuation is measured to be about ±5%
Laser systems configured to output a spectrally-consolidated laser beam and related methods
Koplow, Jeffrey P [San Ramon, CA
2012-01-10
A laser apparatus includes a plurality of pumps each of which is configured to emit a corresponding pump laser beam having a unique peak wavelength. The laser apparatus includes a spectral beam combiner configured to combine the corresponding pump laser beams into a substantially spatially-coherent pump laser beam having a pump spectrum that includes the unique peak wavelengths, and first and second selectively reflective elements spaced from each other to define a lasing cavity including a lasing medium therein. The lasing medium generates a plurality of gain spectra responsive to absorbing the pump laser beam. Each gain spectrum corresponds to a respective one of the unique peak wavelengths of the substantially spatially-coherent pump laser beam and partially overlaps with all other ones of the gain spectra. The reflective elements are configured to promote emission of a laser beam from the lasing medium with a peak wavelength common to each gain spectrum.
Lee, Changmin; Shen, Chao; Cozzan, Clayton; Farrell, Robert M.; Speck, James S.; Nakamura, Shuji; Ooi, Boon S.; DenBaars, Steven P.
2017-01-01
Data communication based on white light generated using a near-ultraviolet (NUV) laser diode (LD) pumping red-, green-, and blue-emitting (RGB) phosphors was demonstrated for the first time. A III-nitride laser diode (LD) on a semipolar (2021
Svaasand, Lars O; Nelson, J Stuart
2004-01-01
The physical basis for optimization of wavelength, pulse duration, and cooling for laser-induced selective photothermolysis of hair follicles in human skin is discussed. The results indicate that the most important optimization parameter is the cooling efficiency of the technique utilized for epidermal protection. The optical penetration is approximately the same for lasers at 694, 755, and 800 nm. The penetration of radiation from Nd:yttrium-aluminum-garnet lasers at 1064 nm is, however, somewhat larger. Photothermal damage to the follicle is shown to be almost independent of laser pulse duration up to 100 ms. The results reveal that epidermal cooling by a 30-80-ms-long cryogen spurt immediately before laser exposure is the only efficient technique for laser pulse durations less than 10 ms. For longer pulse durations in the 30-100 ms range, protection can be done efficiently by skin cooling during laser exposure. For laser pulses of 100 ms, an extended precooling period, e.g., by bringing a cold object into good thermal contact with the skin for about 1 s, can be of value. Thermal quenching of laser induced epidermal temperature rise after pulsed exposure can most efficiently be done with a 20 ms cryogen spurt applied immediately after irradiation. (c) 2004 Society of Photo-Optical Instrumentation Engineers.
Paulis, Evgeniya; Pacher, Ulrich; Weimerskirch, Morris J. J.; Nagy, Tristan O.; Kautek, Wolfgang
2017-12-01
In this study, galvanic coatings of Cu and Ni, typically applied in industrial standard routines, were investigated. Ablation experiments were carried out using the first two harmonic wavelengths of a pulsed Nd:YAG laser and the resulting plasma spectra were analysed using a linear Pearson correlation method. For both wavelengths the absorption/ablation behaviour as well as laser-induced breakdown spectroscopy (LIBS) depth profiles were studied varying laser fluences between 4.3-17.2 J/cm^2 at 532 nm and 2.9-11.7 J/cm^2 at 1064 nm. The LIBS-stratigrams were compared with energy-dispersive X-ray spectroscopy of cross-sections. The ablation rates were calculated and compared to theoretical values originating from a thermal ablation model. Generally, higher ablation rates were obtained with 532 nm light for both materials. The light-plasma interaction is suggested as possible cause of the lower ablation rates in the infrared regime. Neither clear evidence of the pure thermal ablation, nor correlation with optical properties of investigated materials was obtained.
Furumaki, Shu
2012-12-06
We report results on circular dichroism (CD) measured on single immobilized chlorosomes of a triple mutant of green sulfur bacterium Chlorobaculum tepidum. The CD signal is measured by monitoring chlorosomal bacteriochlorphyll c fluorescence excited by alternate left and right circularly polarized laser light with a fixed wavelength of 733 nm. The excitation wavelength is close to a maximum of the negative CD signal of a bulk solution of the same chlorosomes. The average CD dissymmetry parameter obtained from an ensemble of individual chlorosomes was gs = -0.025, with an intrinsic standard deviation (due to variations between individual chlorosomes) of 0.006. The dissymmetry value is about 2.5 times larger than that obtained at the same wavelength in the bulk solution. The difference can be satisfactorily explained by taking into account the orientation factor in the single-chlorosome experiments. The observed distribution of the dissymmetry parameter reflects the well-ordered nature of the mutant chlorosomes. © 2012 American Chemical Society.
Furumaki, Shu; Yabiku, Yu; Habuchi, Satoshi; Tsukatani, Yusuke; Bryant, Donald A.; Vá cha, Martin
2012-01-01
We report results on circular dichroism (CD) measured on single immobilized chlorosomes of a triple mutant of green sulfur bacterium Chlorobaculum tepidum. The CD signal is measured by monitoring chlorosomal bacteriochlorphyll c fluorescence excited by alternate left and right circularly polarized laser light with a fixed wavelength of 733 nm. The excitation wavelength is close to a maximum of the negative CD signal of a bulk solution of the same chlorosomes. The average CD dissymmetry parameter obtained from an ensemble of individual chlorosomes was gs = -0.025, with an intrinsic standard deviation (due to variations between individual chlorosomes) of 0.006. The dissymmetry value is about 2.5 times larger than that obtained at the same wavelength in the bulk solution. The difference can be satisfactorily explained by taking into account the orientation factor in the single-chlorosome experiments. The observed distribution of the dissymmetry parameter reflects the well-ordered nature of the mutant chlorosomes. © 2012 American Chemical Society.
Optical extinction dependence on wavelength and size distribution of airborne dust
Pangle, Garrett E.; Hook, D. A.; Long, Brandon J. N.; Philbrick, C. R.; Hallen, Hans D.
2013-05-01
The optical scattering from laser beams propagating through atmospheric aerosols has been shown to be very useful in describing air pollution aerosol properties. This research explores and extends that capability to particulate matter. The optical properties of Arizona Road Dust (ARD) samples are measured in a chamber that simulates the particle dispersal of dust aerosols in the atmospheric environment. Visible, near infrared, and long wave infrared lasers are used. Optical scattering measurements show the expected dependence of laser wavelength and particle size on the extinction of laser beams. The extinction at long wavelengths demonstrates reduced scattering, but chemical absorption of dust species must be considered. The extinction and depolarization of laser wavelengths interacting with several size cuts of ARD are examined. The measurements include studies of different size distributions, and their evolution over time is recorded by an Aerodynamic Particle Sizer. We analyze the size-dependent extinction and depolarization of ARD. We present a method of predicting extinction for an arbitrary ARD size distribution. These studies provide new insights for understanding the optical propagation of laser beams through airborne particulate matter.
International Nuclear Information System (INIS)
Zulkifli, M Z; Ahmad, H; Hassan, N A; Jemangin, M H; Harun, S W
2011-01-01
A multi-wavelength Brillouin fibre laser (MBFL) with an ultra-wideband tuning range from 1420 nm to 1620 nm is demonstrated. The MBFL uses an ultra-wideband semiconductor optical amplifier (SOA) and a dispersion compensating fibre (DCF) as the linear gain medium and nonlinear gain medium, respectively. The proposed MBFL has a wide tuning range covering the short (S-), conventional (C-) and long (L-) bands with a wavelength spacing of 0.08 nm, making it highly suitable for DWDM system applications. The output power of the observed Brillouin Stokes ranges approximately from -5.94 dBm to -0.41 dBm for the S-band, from -4.34 dBm to 0.02 dBm for the C-band and from -2.19 dBm to 0.39 dBm for the L-band. The spacing between each adjacent wavelengths of all the three bands is about 0.08 nm, which is approximately 10.7 GHz for the frequency domain. (lasers)
Impact of beacon wavelength on phase-compensation performance
Enterline, Allison A.; Spencer, Mark F.; Burrell, Derek J.; Brennan, Terry J.
2017-09-01
This study evaluates the effects of beacon-wavelength mismatch on phase-compensation performance. In general, beacon-wavelength mismatch occurs at the system level because the beacon-illuminator laser (BIL) and high-energy laser (HEL) are often at different wavelengths. Such is the case, for example, when using an aperture sharing element to isolate the beam-control sensor suite from the blinding nature of the HEL. With that said, this study uses the WavePlex Toolbox in MATLAB® to model ideal spherical wave propagation through various atmospheric-turbulence conditions. To quantify phase-compensation performance, we also model a nominal adaptive-optics (AO) system. We achieve correction from a Shack-Hartmann wavefront sensor and continuous-face-sheet deformable mirror using a least-squares phase reconstruction algorithm in the Fried geometry and a leaky integrator control law. To this end, we plot the power in the bucket metric as a function of BIL-HEL wavelength difference. Our initial results show that positive BIL-HEL wavelength differences achieve better phase compensation performance compared to negative BIL-HEL wavelength differences (i.e., red BILs outperform blue BILs). This outcome is consistent with past results.
The Laser MicroJet (LMJ): a multi-solution technology for high quality micro-machining
Mai, Tuan Anh; Richerzhagen, Bernold; Snowdon, Paul C.; Wood, David; Maropoulos, Paul G.
2007-02-01
The field of laser micromachining is highly diverse. There are many different types of lasers available in the market. Due to their differences in irradiating wavelength, output power and pulse characteristic they can be selected for different applications depending on material and feature size [1]. The main issues by using these lasers are heat damages, contamination and low ablation rates. This report examines on the application of the Laser MicroJet(R) (LMJ), a unique combination of a laser beam with a hair-thin water jet as a universal tool for micro-machining of MEMS substrates, as well as ferrous and non-ferrous materials. The materials include gallium arsenide (GaAs) & silicon wafers, steel, tantalum and alumina ceramic. A Nd:YAG laser operating at 1064 nm (infra red) and frequency doubled 532 nm (green) were employed for the micro-machining of these materials.
Diode laser-pumped Ho:YLF laser
International Nuclear Information System (INIS)
Hemmati, H.
1987-01-01
The author reports laser action in Ho:YLF at 2.06 μm following optical pumping with a cw diode laser array. Diode laser-pumped Nd-YAG and Ho:YAG have been reported recently. Lasers with a wavelength of 2 μm have medical and optical communication applications. The diode laser light is focused with a 60-mm focal length lens onto the YLF crystal. A high-reflectivity mirror with 100-mm radius of curvature was used as the output coupler. The lasing threshold was at 5 mWof incident power. This is higher than expected considering that a high reflector was used as the output coupler. However, a more uniform cooling of the crystal is expected to lower the lasing threshold. With 100 mW of pump power coupled into the crystal, --20 mW of 2-μm radiation was observed from this unoptimized setup. The 2-μm laser output is highly sensitive to output coupler alignment, YLF crystal temperature, and pump laser wavelength. The 20% optical conversion efficiency achieved in his preliminary measurements is expected to be improved by better crystal cooling, proper matching of laser wavelength to crystal absorption, variations in the concentration of Ho and sensitizers and use of a proper output coupler. A study of the parameters mentioned above and the effect of crystal temperature on the laser output is under way
Yan, Liping; Chen, Benyong; Zhang, Enzheng; Zhang, Shihua; Yang, Ye
2015-08-01
A novel method for the precision measurement of refractive index of air (n(air)) based on the combining of the laser synthetic wavelength interferometry with the Edlén equation estimation is proposed. First, a n(air_e) is calculated from the modified Edlén equation according to environmental parameters measured by low precision sensors with an uncertainty of 10(-6). Second, a unique integral fringe number N corresponding to n(air) is determined based on the calculated n(air_e). Then, a fractional fringe ε corresponding to n(air) with high accuracy can be obtained according to the principle of fringe subdivision of laser synthetic wavelength interferometry. Finally, high accurate measurement of n(air) is achieved according to the determined fringes N and ε. The merit of the proposed method is that it not only solves the problem of the measurement accuracy of n(air) being limited by the accuracies of environmental sensors, but also avoids adopting complicated vacuum pumping to measure the integral fringe N in the method of conventional laser interferometry. To verify the feasibility of the proposed method, comparison experiments with Edlén equations in short time and in long time were performed. Experimental results show that the measurement accuracy of n(air) is better than 2.5 × 10(-8) in short time tests and 6.2 × 10(-8) in long time tests.
Development of SAC-OCDMA in FSO with multi-wavelength laser source
Moghaddasi, Majid; Mamdoohi, Ghazaleh; Muhammad Noor, Ahmad Shukri; Mahdi, Mohd Adzir; Ahmad Anas, Siti Barirah
2015-12-01
We propose and demonstrate a free space optical network, based on spectral amplitude coding optical code division multiple access (SAC-OCDMA) with a multi-wavelength laser source. A detailed theoretical analysis that represents the characteristics of SAC-OCDMA system was developed. In addition to the impact of turbulence, influences of several system noises such as optical beat interference (OBI), relative intensity noise, and receiver noises, have been studied. From the numerical results, it was found that the influence of OBI is more dominant, especially at higher received power. Two different codes, namely, modified quadratic congruence and modified double weight, are then compared with the latter which provides better performance. A transmission distance of 2.6 km with 10 users and an 8 cm aperture diameter is advisable whenever the turbulence is moderate. These results can be improved when a beam divergence smaller than 1 mrad is utilized.
Blue laser diode (LD) and light emitting diode (LED) applications
International Nuclear Information System (INIS)
Bergh, Arpad A.
2004-01-01
The family of blue LEDs, edge emitting and surface emitting lasers, enable a number of applications. Blue lasers are used in digital applications such as optical storage in high density DVDs. The resolution of the spot size and hence the storage density is diffraction limited and is inversely proportional to the square of the wavelength of the laser. Other applications include printing, optical scanners, and high-resolution photo-lithography. As light emitters, blue LEDs are used for signaling and in direct view large area emissive displays. They are also making inroads into signage and LCD back-lighting, mobile platforms, and decorative accent lighting in curtains, furniture, etc. Blue LEDs produce white light either with phosphor wavelength converters or in combination with red and green LEDs. The full potential of LED light sources will require three devices to enable complete control over color and intensity. Sensing and medical/bio applications have a major impact on home security, on monitoring the environment, and on health care. New emerging diagnostic and therapeutic applications will improve the quality and reduce the cost of health care. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Blue laser diode (LD) and light emitting diode (LED) applications
Energy Technology Data Exchange (ETDEWEB)
Bergh, Arpad A [Optoelectronics Industry Development Association (OIDA), 1133 Connecticut Avenue, NW, Suite 600, Washington, DC 20036-4329 (United States)
2004-09-01
The family of blue LEDs, edge emitting and surface emitting lasers, enable a number of applications. Blue lasers are used in digital applications such as optical storage in high density DVDs. The resolution of the spot size and hence the storage density is diffraction limited and is inversely proportional to the square of the wavelength of the laser. Other applications include printing, optical scanners, and high-resolution photo-lithography. As light emitters, blue LEDs are used for signaling and in direct view large area emissive displays. They are also making inroads into signage and LCD back-lighting, mobile platforms, and decorative accent lighting in curtains, furniture, etc. Blue LEDs produce white light either with phosphor wavelength converters or in combination with red and green LEDs. The full potential of LED light sources will require three devices to enable complete control over color and intensity. Sensing and medical/bio applications have a major impact on home security, on monitoring the environment, and on health care. New emerging diagnostic and therapeutic applications will improve the quality and reduce the cost of health care. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Surfaces in the interaction of intense long wavelength laser light with plasmas
International Nuclear Information System (INIS)
Jones, R.D.
1985-01-01
The role of surface in the interaction of intense CO 2 laser light with plasmas is reviewed. The collisionless absorption of long wavelength light is discussed. Specific comments on the role of ponderomotive forces and profile steepening on resonant absorption are made. It is shown that at intensities above 10 15 W/cm 2 the absorption is determined by ion acoustic-like surface modes. It is demonstrated experimentally that harmonics up to the forty-sixth can be generated in steep density profiles. Computer simulations and theoretical mechanisms for this phenomena are presented. The self generation of magnetic fields on surfaces is discussed. The role these fields play in the lateral transport of energy, the insulation of the target from hot electrons, and the acceleration of fast ions is discussed
Directory of Open Access Journals (Sweden)
Yongning Liu
2015-07-01
Full Text Available A time difference method to conveniently measure the phase shift between output wavelength and intensity of distributed feedback laser diodes (DFB-LDs was proposed. This approach takes advantage of asymmetric absorption positions at the same wavelength during wavelength increase and decrease tuning processes in the intensity-time curve by current modulation. For its practical implementation, a measurement example of phase shift was demonstrated by measuring a time difference between the first time and the second time attendances of the same gas absorption line in the intensity-time curve during one sine or triangle modulation circle. The phase shifts at modulation frequencies ranging from 50 Hz to 50 kHz were measured with a resolution of 0.001π. As the modulation frequency increased the shift value increased with a slowed growth rate.
Al-Jabr, Ahmad Ali
2016-08-01
Laser Diodes (LD) have numerous applications for industry, military, medicine and communications. The first visible LD was invented in 1962 by Nick Holonyak, emitted at 710 nm (red). In 1990s, Shuji Nakamura invented the blue and green Light Emitting Diodes (LED) and later LDs. The production of LDs emitting between 532- 632 nm has been severely lagging behind the rest of the visible spectrum. Yellow and orange LDs are still not accessible due to the lack of successfully grown material with high optical efficiency. AlGaInP is the quaternary compound semiconductor used to grow green to red LEDs and red LDs. At a material composition that is supposed to lase below 630 nm, the optical efficiency becomes low due to the oxygen-related defects associated with high Al content. The quantum well intermixing (QWI) is a post-growth process that is applied to laser structure to tune the wavelength of laser. Until now, there are limited reports on successful intermixing of InGaP/InAlGaP laser structures while maintaining the crystal quality. In this work, we introduced a novel intermixing process that utilizes the high strain induced by the dielectric film during annealing to initiate the intermixing. We deposited SiO2 capping by plasma-enhanced chemical vapor deposition (PECVD) onto the InGaP/InAlGaP laser structure emitting at 635 nm, and then annealed the structure up to 950 Celsius for different periods of time, resulting in an astonishing 100 nm blueshift. This blueshift allowed us to produce an unprecedented shorter wavelength orange lasers emitting at 608 nm. For low degree of intermixing, we have noticed an increase in the intensity of the photoluminescence (PL) signal. The improvement in the PL signal was translated to a reduction in threshold current. We implemented the technique on an LED structure with Al-rich QWs emitting at 590 nm. Significant increase in the PL intensity (20 folds) was observed. By analyzing the improved structure, we observed reduction in oxygen
Green Light for Nocturnally Migrating Birds
Directory of Open Access Journals (Sweden)
Hanneke Poot
2008-12-01
Laboratory experiments have shown the magnetic compass to be wavelength dependent: migratory birds require light from the blue-green part of the spectrum for magnetic compass orientation, whereas red light (visible long-wavelength disrupts magnetic orientation. We designed a field study to test if and how changing light color influenced migrating birds under field conditions. We found that nocturnally migrating birds were disoriented and attracted by red and white light (containing visible long-wavelength radiation, whereas they were clearly less disoriented by blue and green light (containing less or no visible long-wavelength radiation. This was especially the case on overcast nights. Our results clearly open perspective for the development of bird-friendly artificial lighting by manipulating wavelength characteristics. Preliminary results with an experimentally developed bird-friendly light source on an offshore platform are promising. What needs to be investigated is the impact of bird-friendly light on other organisms than birds.
Two-wavelength HeNe laser interferometer
International Nuclear Information System (INIS)
Granneman, E.H.A.
1981-01-01
This paper presents an interferometer set-up in which two wavelengths are used simultaneously. This enables one to determine separately the phase shifts caused by changes in plasma density and by mechanical vibrations of the interferometer structure
Long-wavelength photonic integrated circuits and avalanche photodetectors
Tsou, Yi-Jen D.; Zaytsev, Sergey; Pauchard, Alexandre; Hummel, Steve; Lo, Yu-Hwa
2001-10-01
Fast-growing internet traffic volume require high data communication bandwidth over longer distances. Access network bottlenecks put pressure on short-range (SR) telecommunication systems. To effectively address these datacom and telecom market needs, low-cost, high-speed laser modules at 1310 to 1550 nm wavelengths and avalanche photodetectors are required. The great success of GaAs 850nm VCSEls for Gb/s Ethernet has motivated efforts to extend VCSEL technology to longer wavelengths in the 1310 and 1550 nm regimes. However, the technological challenges associated with materials for long wavelength VCSELs are tremendous. Even with recent advances in this area, it is believed that significant additional development is necessary before long wavelength VCSELs that meet commercial specifications will be widely available. In addition, the more stringent OC192 and OC768 specifications for single-mode fiber (SMF) datacom may require more than just a long wavelength laser diode, VCSEL or not, to address numerous cost and performance issues. We believe that photonic integrated circuits (PICs), which compactly integrate surface-emitting lasers with additional active and passive optical components with extended functionality, will provide the best solutions to today's problems. Photonic integrated circuits have been investigated for more than a decade. However, they have produced limited commercial impact to date primarily because the highly complicated fabrication processes produce significant yield and device performance issues. In this presentation, we will discuss a new technology platform of InP-based PICs compatible with surface-emitting laser technology, as well as a high data rate externally modulated laser module. Avalanche photodetectors (APDs) are the key component in the receiver to achieve high data rate over long transmission distance because of their high sensitivity and large gain- bandwidth product. We have used wafer fusion technology to achieve In
Thermal tuning On narrow linewidth fiber laser
Han, Peiqi; Liu, Tianshan; Gao, Xincun; Ren, Shiwei
2010-10-01
At present, people have been dedicated to high-speed and large-capacity optical fiber communication system. Studies have been shown that optical wavelength division multiplexing (WDM) technology is an effective means of communication to increase the channel capacity. Tunable lasers have very important applications in high-speed, largecapacity optical communications, and distributed sensing, it can provide narrow linewidth and tunable laser for highspeed optical communication. As the erbium-doped fiber amplifier has a large gain bandwidth, the erbium-doped fiber laser can be achieved lasing wavelength tunable by adding a tunable filter components, so tunable filter device is the key components in tunable fiber laser.At present, fiber laser wavelength is tuned by PZT, if thermal wavelength tuning is combined with PZT, a broader range of wavelength tuning is appearance . Erbium-doped fiber laser is used in the experiments,the main research is the physical characteristics of fiber grating temperature-dependent relationship and the fiber grating laser wavelength effects. It is found that the fiber laser wavelength changes continuously with temperature, tracking several temperature points observed the self-heterodyne spectrum and found that the changes in spectra of the 3dB bandwidth of less than 1kHz, and therefore the fiber laser with election-mode fiber Bragg grating shows excellent spectral properties and wavelength stability.
Single-shot dual-wavelength in-line and off-axis hybrid digital holography
Wang, Fengpeng; Wang, Dayong; Rong, Lu; Wang, Yunxin; Zhao, Jie
2018-02-01
We propose an in-line and off-axis hybrid holographic real-time imaging technique. The in-line and off-axis digital holograms are generated simultaneously by two lasers with different wavelengths, and they are recorded using a color camera with a single shot. The reconstruction is carried using an iterative algorithm in which the initial input is designed to include the intensity of the in-line hologram and the approximate phase distributions obtained from the off-axis hologram. In this way, the complex field in the object plane and the output by the iterative procedure can produce higher quality amplitude and phase images compared to traditional iterative phase retrieval. The performance of the technique has been demonstrated by acquiring the amplitude and phase images of a green lacewing's wing and a living moon jellyfish.
DEFF Research Database (Denmark)
Müller, André; Jensen, Ole Bjarlin; Andersen, Peter E.
We propose an efficient concept increasing the power of diode laser systems in the visible spectral range. In comparison with second harmonic generation of single emitters, spectral beam combining with subsequent sum-frequency generation enhances the available power significantly. Combining two...... 1060 nm tapered diode lasers, we achieve a 2.5-3.2 fold increase of green light with a maximum power of 3.9 Watts in a diffraction-limited beam. At this level, diode lasers have a high application potential, for example, within the biomedical field. In order to enhance the power even further, our...
DEFF Research Database (Denmark)
Zubov, F.; Semenova, Elizaveta; Kulkova, Irina
2017-01-01
We report on a study of lasers with an emission wavelength of about 1.5 μm and high temperature stability, synthesized on an InP (001) substrate. Self-organized InAs quantum dots capped with a thin GaAs layer are used as the active region of the laser. A quaternary InGaAsP solid solution with a b......We report on a study of lasers with an emission wavelength of about 1.5 μm and high temperature stability, synthesized on an InP (001) substrate. Self-organized InAs quantum dots capped with a thin GaAs layer are used as the active region of the laser. A quaternary InGaAsP solid solution...
Goswami, Sumita
2017-12-11
This study reports on the qualitative analysis of photoluminescence effect generated from waste carbon of cooking oven by facile cost-effective material engineering. The waste carbon product as a form of carbon nanoparticles (CNPs) is incorporated within a conjugate polymer, namely, polyaniline (PANI) to produce CNP-PANI composites that have shown excitation-wavelength-independent triple-band photoluminescence emission effect and highly sensitive Fe+3 ion detection ability. Herein the waste carbon material, while functionalized within the conjugated polymer, needs no further acid treatment or surface modification thus making the process cheaper, environmentally benign, and useful for green nanotechnology. The excitation-wavelength-independent unique triple-band photoluminescence spectrum is the direct consequence of carbon–polyaniline synergy in π–π transition and the surface passivation of CNPs by the [BOND]NH2 group rich aniline during in-situ polymerization. The current scenario has been studied for the samples prepared with different CNP concentrations for different reaction times and discussed in details with supportive physico-chemical characterizations. Moreover, the present study has demonstrated that the current material can be used as a fluorescent sensing platform for Fe+3 ions with high sensitivity and selectivity criteria where the detection limit of the sensing probe has a value as low as 12 × 10−9 nM.
Spectrally high performing quantum cascade lasers
Toor, Fatima
Quantum cascade (QC) lasers are versatile semiconductor light sources that can be engineered to emit light of almost any wavelength in the mid- to far-infrared (IR) and terahertz region from 3 to 300 mum [1-5]. Furthermore QC laser technology in the mid-IR range has great potential for applications in environmental, medical and industrial trace gas sensing [6-10] since several chemical vapors have strong rovibrational frequencies in this range and are uniquely identifiable by their absorption spectra through optical probing of absorption and transmission. Therefore, having a wide range of mid-IR wavelengths in a single QC laser source would greatly increase the specificity of QC laser-based spectroscopic systems, and also make them more compact and field deployable. This thesis presents work on several different approaches to multi-wavelength QC laser sources that take advantage of band-structure engineering and the uni-polar nature of QC lasers. Also, since for chemical sensing, lasers with narrow linewidth are needed, work is presented on a single mode distributed feedback (DFB) QC laser. First, a compact four-wavelength QC laser source, which is based on a 2-by-2 module design, with two waveguides having QC laser stacks for two different emission wavelengths each, one with 7.0 mum/11.2 mum, and the other with 8.7 mum/12.0 mum is presented. This is the first design of a four-wavelength QC laser source with widely different emission wavelengths that uses minimal optics and electronics. Second, since there are still several unknown factors that affect QC laser performance, results on a first ever study conducted to determine the effects of waveguide side-wall roughness on QC laser performance using the two-wavelength waveguides is presented. The results are consistent with Rayleigh scattering effects in the waveguides, with roughness effecting shorter wavelengths more than longer wavelengths. Third, a versatile time-multiplexed multi-wavelength QC laser system that
Energy Technology Data Exchange (ETDEWEB)
Cahoon, Erica M.; Almirall, Jose R.
2010-05-01
Laser induced breakdown spectroscopy can be used for the chemical characterization of glass to provide evidence of an association between a fragment found at a crime scene to a source of glass of known origin. Two different laser irradiances, 266 nm and 1064 nm, were used to conduct qualitative and quantitative analysis of glass standards. Single-pulse and double-pulse configurations and lens-to-sample-distance settings were optimized to yield the best laser-glass coupling. Laser energy and acquisition timing delays were also optimized to result in the highest signal-to-noise ratio corresponding to the highest precision and accuracy. The crater morphology was examined and the mass removed was calculated for both the 266 nm and 1064 nm irradiations. The analytical figures of merit suggest that the 266 nm and 1064 nm wavelengths are capable of good performance for the forensic chemical characterization of glass. The results presented here suggest that the 266 nm laser produces a better laser-glass matrix coupling, resulting in a better stoichiometric representation of the glass sample. The 266 nm irradiance is therefore recommended for the forensic analysis and comparison of glass samples.
International Nuclear Information System (INIS)
Cahoon, Erica M.; Almirall, Jose R.
2010-01-01
Laser induced breakdown spectroscopy can be used for the chemical characterization of glass to provide evidence of an association between a fragment found at a crime scene to a source of glass of known origin. Two different laser irradiances, 266 nm and 1064 nm, were used to conduct qualitative and quantitative analysis of glass standards. Single-pulse and double-pulse configurations and lens-to-sample-distance settings were optimized to yield the best laser-glass coupling. Laser energy and acquisition timing delays were also optimized to result in the highest signal-to-noise ratio corresponding to the highest precision and accuracy. The crater morphology was examined and the mass removed was calculated for both the 266 nm and 1064 nm irradiations. The analytical figures of merit suggest that the 266 nm and 1064 nm wavelengths are capable of good performance for the forensic chemical characterization of glass. The results presented here suggest that the 266 nm laser produces a better laser-glass matrix coupling, resulting in a better stoichiometric representation of the glass sample. The 266 nm irradiance is therefore recommended for the forensic analysis and comparison of glass samples.
Menzies, R. T.; Shumate, M. S.
1976-01-01
Measurements of water vapor absorption were taken with a resonant optoacoustical detector (cylindrical pyrex detector, two BaF2 windows fitted into end plates at slight tilt to suppress Fabry-Perot resonances), for lack of confidence in existing spectral tabular data for the 5-7 micron region, as line shapes in the wing regions of water vapor lines are difficult to characterize. The measurements are required for air pollution studies using a CO laser, to find the differential absorption at the wavelengths in question due to atmospheric constituents other than water vapor. The design and performance of the optoacoustical detector are presented. Effects of absorption by ambient NO are considered, and the fixed-frequency discretely tunable CO laser is found suitable for monitoring urban NO concentrations in a fairly dry climate, using the water vapor absorption data obtained in the study.
International Nuclear Information System (INIS)
Gevargez, A.; Groenemeyer, D.W.H.; Czerwinski, F.
2000-01-01
The aim of this study was to evaluate the compact, portable Ceralas-D diode laser (CeramOptec; 980+30 nm wavelength, 200-μm optical fiber) concerning clinical usefulness, handling, and clinical results in the CT-guided treatment of herniated lumbar discs. The positioning of the canula in intradiscal space, the placement of the laser fiber into the disc through the lying canula, and the vaporization itself were carried out under CT-guidance. Due to the thin fiber optic, it was possible to use a thin 23-gauge canula. The laser procedure was performed in 0.1- to 1-s shots with 1-s pulse pause and 4-W power output. A total of 1650-2300 J was applied on each percutaneous laser disc decompression (PLDD). Results in 26 patients were established with a visual-analogue scale (VAS). On the follow-up examinations, 46% of the patients were absolutely pain free (>85% VAS) and fully active in everyday life after 4 postoperative weeks. Thirty-one percent of patients were relieved of the leg pain but had occasional back pain without sensorimotor impairment. Fifteen percent sensed a slight alleviation (>50% VAS) of the radiate pain. Eight percent did not experience radicular or pseudo-radicular pain alleviation (<25% VAS). Cerales-D proves to be an efficient tool for CT-guided PLDD on non-sequestered herniated lumbar discs. (orig.)
Esnal, I; Duran-Sampedro, G; Agarrabeitia, A R; Bañuelos, J; García-Moreno, I; Macías, M A; Peña-Cabrera, E; López-Arbeloa, I; de la Moya, S; Ortiz, M J
2015-03-28
Linking amino and hydroxycoumarins to BODIPYs through the amino or hydroxyl group lets the easy construction of unprecedented photostable coumarin-BODIPY hybrids with broadened and enhanced absorption in the UV spectral region, and outstanding wavelength-tunable laser action within the green-to-red spectral region (∼520-680 nm). These laser dyes allow the generation of a valuable tunable UV (∼260-350 nm) laser source by frequency doubling, which is essential to study accurately the photochemistry of biological molecules under solar irradiation. The tunability is achieved by selecting the substitution pattern of the hybrid. Key factors are the linking heteroatom (nitrogen vs. oxygen), the number of coumarin units joined to the BODIPY framework and the involved linking positions.
Energy Technology Data Exchange (ETDEWEB)
Qiu, Weicheng [College of Photoelectric Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073 (China); National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China); Hu, Weida, E-mail: wdhu@mail.sitp.ac.cn; Lin, Tie; Yin, Fei; Zhang, Bo; Chen, Xiaoshuang; Lu, Wei [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083 (China); Cheng, Xiang' ai, E-mail: xiang-ai-cheng@126.com; Wang, Rui [College of Photoelectric Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073 (China)
2014-11-10
In this paper, we report on the disappearance of the photosensitive area extension effect and the unusual temperature dependence of junction transformation for mid-wavelength, n-on-p HgCdTe photovoltaic infrared detector arrays. The n-type region is formed by B{sup +} ion implantation on Hg-vacancy-doped p-type HgCdTe. Junction transformations under different temperatures are visually captured by a laser beam induced current microscope. A physical model of temperature dependence on junction transformation is proposed and demonstrated by using numerical simulations. It is shown that Hg-interstitial diffusion and temperature activated defects jointly lead to the p-n junction transformation dependence on temperature, and the weaker mixed conduction compared with long-wavelength HgCdTe photodiode contributes to the disappearance of the photosensitive area extension effect in mid-wavelength HgCdTe infrared detector arrays.
Matys, Jacek; Flieger, Rafał; Dominiak, Marzena
2017-07-01
Many surgical procedures in soft tissue are performed using diode lasers. Recently, a novel diode laser operating at 445 nm wavelength was introduced in dentistry. The aim of our study was to evaluate the time of surgery and an increase in temperature of titanium implants during its uncovering using 445 and 980 nm wavelengths. The research included 45 pig mandibles (n = 45). The specimens were randomly divided into 3 groups (n = 15) according to the laser irradiation mode and wavelength; G1 - 445 nm laser, power: 3 W, continuous wave (CW), distance: 2 mm, power density: 7460 W/cm2, fiber: 320 μm, noncontact mode; G2 - 445 nm laser (power: 2 W, CW, power density: 4970 W/cm2, fiber: 320 μm, contact mode; G3 (control) - 980 nm laser, power: 2.5 W, CW, power density: 15920 W/cm2, fiber: 200 μm, contact mode. The temperature was measured with a 2 K-type thermocouples (a P1 at collar and a P2 at mid height of the implant). The mean temperature rises measured by the P1 thermocouple were 16.9°C, 36.1°C and 21.6°C in the G1, G2 and G3 group, respectively. Significant differences in temperature rise were found between the G1 and G2 group (p = 0.0007) and the G2 and G3 group (p = 0.01). The mean temperature rises measured by the P2 thermocouple were 1.8°C, 1.4°C and 5.6°C in the G1, G2 and G3 group, respectively. Significant differences in temperature rise were found between the G1 and the G2 or G3 group (p = 0.0001). The significant differences among the study groups in average time necessary for uncovering the implants amounted to 69.7, 54.4 and 83.6 s, respectively (p diode laser in non-contact mode reduced the temperature rise of the implants. The additional pulse intervals during laser irradiation with wavelength of 445 nm when operating in contact mode are needed.
Rossel, Ralf Erik; Wendt, K; Rothe, S
In the context of this work the foundation for the commissioning of a comprehensive environmental and operational data acquisition system was established. This development was performed for the Resonance Ionization Laser Ion Source (RILIS) at the ISOLDE radioactive ion beam facility within the European Organization for Nuclear Research CERN. As an essential step towards long-term automated operation, a remote control and wavelength stabilization system for the RILIS titanium:sapphire lasers was put into operation. This required the installation of a data recording infrastructure to work with a distributed sensor network. After operational data within the CERN technical computing network was collected and analyzed, the required wavelength adjustment was automatically performed by a stepper motor-driven correction system. The configuration of the hardware for acquisition and control and the integration of the dedicated system modules was performed using the graphical and data flow oriented programming language ...
Priante, D.; Dursun, I.; Alias, M. S.; Shi, D.; Melnikov, V. A.; Ng, T. K.; Mohammed, O. F.; Bakr, O. M.; Ooi, B. S.
2015-02-01
We investigated the mechanisms of radiative recombination in a CH3NH3PbBr3 hybrid perovskite material using low-temperature, power-dependent (77 K), and temperature-dependent photoluminescence (PL) measurements. Two bound-excitonic radiative transitions related to grain size inhomogeneity were identified. Both transitions led to PL spectra broadening as a result of concurrent blue and red shifts of these excitonic peaks. The red-shifted bound-excitonic peak dominated at high PL excitation led to a true-green wavelength of 553 nm for CH3NH3PbBr3 powders that are encapsulated in polydimethylsiloxane. Amplified spontaneous emission was eventually achieved for an excitation threshold energy of approximately 350 μJ/cm2. Our results provide a platform for potential extension towards a true-green light-emitting device for solid-state lighting and display applications.
Priante, Davide
2015-02-23
We investigated the mechanisms of radiative recombination in a CH3NH3PbBr3 hybrid perovskite material using low-temperature, power-dependent (77K), and temperature-dependent photoluminescence (PL) measurements. Two bound-excitonic radiative transitions related to grain size inhomogeneity were identified. Both transitions led to PL spectra broadening as a result of concurrent blue and red shifts of these excitonic peaks. The red-shifted bound-excitonic peak dominated at high PL excitation led to a true-green wavelength of 553nm for CH3NH3PbBr3 powders that are encapsulated in polydimethylsiloxane. Amplified spontaneous emission was eventually achieved for an excitation threshold energy of approximately 350μJ/cm2. Our results provide a platform for potential extension towards a true-green light-emitting device for solid-state lighting and display applications.
Single-wavelength functional photoacoustic microscopy in biological tissue.
Danielli, Amos; Favazza, Christopher P; Maslov, Konstantin; Wang, Lihong V
2011-03-01
Recently, we developed a reflection-mode relaxation photoacoustic microscope, based on saturation intensity, to measure picosecond relaxation times using a nanosecond laser. Here, using the different relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, the oxygen saturation was quantified in vivo with single-wavelength photoacoustic microscopy. All previous functional photoacoustic microscopy measurements required imaging with multiple-laser-wavelength measurements to quantify oxygen saturation. Eliminating the need for multiwavelength measurements removes the influence of spectral properties on oxygenation calculations and improves the portability and cost-effectiveness of functional or molecular photoacoustic microscopy.
Chhabra, Kanika; Kaur, Prempal; Singh, Karamjit; Aggarwal, Anand; Chalia, Dharamvir
2018-02-01
The purpose of this study was to analyse the outcome of solid-state green laser in high-risk retinopathy of prematurity (ROP) at a tertiary centre in India. Fifty-nine eyes of 30 infants with high-risk ROP were recruited in this prospective, interventional study. High-risk ROP included prethreshold type 1 ROP and APROP. Laser photocoagulation was performed with 532 nm solid-state green laser (Novus Spectra, Lumenis, GmbH, Germany). Of the 30 infants, 18 were males (60%) and 12 were females (40%). The mean birth weight was 1102.83 ± 196.27 g. The mean gestational age was 29.5 ± 1.47 weeks. Zone 1 disease was present in 10 eyes (16.95%) and zone 2 disease in 49 (83.05%) eyes. Out of 57 eyes with prethreshold type 1 ROP, 39 eyes (68.42%) had stage 2 and 18 eyes (31.58%) had stage 3. The postconceptional age at the time of treatment was 36.03 ± 2.32 weeks. The infants received mean 2710.24 ± 747.97 laser spots. Fifty (84.8%) eyes underwent laser in a single sitting and 9 eyes (15.2%) required 2 laser sittings. Mean time for regression of ROP was 5.8 ± 3.8 weeks (range 3-11 weeks). Total ROP regression was seen in 55 eyes (93.22%). Despite laser treatment, 4 (6.78%) eyes of three infants had unfavourable outcome. One infant developed intra-procedural bradycardia. Vitreous haemorrhage was seen in five eyes (8.4%). Solid-state 532 nm green laser is a safe and effective treatment for high-risk retinopathy of prematurity.
The ARGOS laser system: green light for ground layer adaptive optics at the LBT
Raab, Walfried; Rabien, Sebastian; Gässler, Wolfgang; Esposito, Simone; Barl, Lothar; Borelli, Jose; Daysenroth, Matthias; Gemperlein, Hans; Kulas, Martin; Ziegleder, Julian
2014-07-01
We report on the development of the laser system of ARGOS, the multiple laser guide star adaptive optics system for the Large Binocular Telescope (LBT). The system uses a total of six high powered, pulsed Nd:YAG lasers frequency-doubled to a wavelength of 532 nm to generate a set of three guide stars above each of the LBT telescopes. The position of each of the LGS constellations on sky as well as the relative position of the individual laser guide stars within this constellation is controlled by a set of steerable mirrors and a fast tip-tilt mirror within the laser system. The entire opto-mechanical system is housed in two hermetically sealed and thermally controlled enclosures on the SX and DX side of the LBT telescope. The laser beams are propagated through two refractive launch telescopes which focus the beams at an altitude of 12 km, creating a constellation of laser guide stars around a 4 arcminute diameter circle by means of Rayleigh scattering. In addition to the GLAO Rayleigh beacon system, ARGOS has also been designed for a possible future upgrade with a hybrid sodium laser - Rayleigh beacon combination, enabling diffraction limited operation. The ARGOS laser system was successfully installed at the LBT in April 2013. Extensive functional tests have been carried out and have verified the operation of the systems according to specifications. The alignment of the laser system with respect to the launch telescope was carried out during two more runs in June and October 2013, followed by the first propagation of laser light on sky in November 2013.
International Nuclear Information System (INIS)
Omran, M.F.; El-Ahdal, M.A.; El-Kady, M.H.; Yousri, R.M.
2004-01-01
The presence of glutamate in the visual cortex and mitochondria could be used as a measure for the argon laser effect having wavelengths 488 and 515 nm, on the mitochondria. A comparative response for the bound and free glutamate was found. Irradiation with different energies 0.2, 0.5 and 1.0 J for both wavelengths were accomplished. This study makes us to recommend the advantage of using argon laser having wavelength 515 nm to enhance the blocking of glutamate and hence the reduction of brain toxicity. Most of the energy required for cellular functions comes from mitochondria (Shepherd, 1994). Glutamate, which is present in central nervous system at very high level is essential for brain intermediary metabolism (Frazer et al., 1994; Meldrum et al., 2000 and Blumcke et al., 2000). Glutamate is enriched in synaptic vesicles, the subcellular organelles, which are associated with the storage and release of neurotransmitters. Also, biochemical evidence for glutamate as neurotransmitter in fibers from the visual cortex to the subcortical visual relay nuclei has been indicated (Fose and Fonnum, 1987 and George, 1998)
High contrast laser marking of alumina
Penide, J.; Quintero, F.; Riveiro, A.; Fernández, A.; del Val, J.; Comesaña, R.; Lusquiños, F.; Pou, J.
2015-05-01
Alumina serves as raw material for a broad range of advanced ceramic products. These elements should usually be identified by some characters or symbols printed directly on them. In this sense, laser marking is an efficient, reliable and widely implemented process in industry. However, laser marking of alumina still leads to poor results since the process is not able to produce a dark mark, yielding bad contrast. In this paper, we present an experimental study on the process of marking alumina by three different lasers working in two wavelengths: 1064 nm (Near-infrared) and 532 nm (visible, green radiation). A colorimetric analysis has been carried out in order to compare the resulting marks and its contrast. The most suitable laser operating conditions were also defined and are reported here. Moreover, the physical process of marking by NIR lasers is discussed in detail. Field Emission Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy were also employed to analyze the results. Finally, we propose an explanation for the differences of the coloration induced under different atmospheres and laser parameters. We concluded that the atmosphere is the key parameter, being the inert one the best choice to produce the darkest marks.
Poggialini, F.; Campanella, B.; Giannarelli, S.; Grifoni, E.; Legnaioli, S.; Lorenzetti, G.; Pagnotta, S.; Safi, A.; Palleschi, V.
2018-03-01
When compared to other analytical techniques, LIBS shows relatively low precision and, generally, high Limits of Detection (LODs). Until recently, the attempts in improving the LIBS performances have been based on the use of more stable/powerful lasers, high sensitivity detectors or controlled environmental parameters. This can hinder the competitiveness of LIBS by increasing the instrumental setup cost and the difficulty of operation. Sample treatment has proved to be a viable and simple way to increase the LIBS signal; in particular, the Nanoparticle-Enhanced Laser Induced Breakdown Spectroscopy (NELIBS) methodology uses a deposition of metal nanoparticles on the sample to greatly increase the emission of the LIBS plasma. In this work, we used a simple, fast, "green" and low-cost method to synthetize silver nanoparticles by using coffee extract as reducing agents for a silver nitrate solution. This allowed us to obtain nanoparticles of about 25 nm in diameter. We then explored the application of such nanoparticles to the NELIBS analysis of metallic samples with a mobile LIBS instrument. By adjusting the laser parameters and optimizing the sample preparation procedure, we obtained a NELIBS signal that is 4 times the LIBS one. This showed the potential of green-synthetized nanoparticle for NELIBS applications and suggests the possibility of an in-situ application of the technique.
Laser processing for bevel termination of high voltage pn junction in SiC
International Nuclear Information System (INIS)
Kubiak, A; Ruta, Ł; Rosowski, A; French, P
2016-01-01
Proper edge termination of the p-n junction in silicon carbide is a key requirement in the fabrication of discrete devices able to withstand high voltages in reverse polarization. Due to the hardness of SiC the creation of the bevel termination remains difficult using mechanical machining. The use of laser beam sources with medium wavelength (532 nm) gives new possibilities in the machining of the silicon carbide. The paper presents the fabrication of the bevel termination structure in SiC using a green DPSS laser equipped with scanner and dedicated rotating sample holder. Characterization of the resulting structures proves the high potential of the proposed approach. (paper)
Vertical cavity surface emitting lasers from all-inorganic perovskite quantum dots
Sun, Handong; Wang, Yue; Li, Xiaoming; Zeng, Haibo
We report the breakthrough in realizing the challenging while practically desirable vertical cavity surface emitting lasers (VCSELs) based on the CsPbX3 inorganic perovskite nanocrystals (IPNCs). These laser devices feature record low threshold (9 µJ/cm2), unidirectional output (beam divergence of 3.6º) and superb stability. We show that both single-mode and multimode lasing operation are achievable in the device. In contrast to traditional metal chacogenide colloidal quantum dots based lasers where the pump thresholds for the green and blue wavelengths are typically much higher than that of the red, these CsPbX3 IPNC-VCSEL devices are able to lase with comparable thresholds across the whole visible spectral range, which is appealing for achieving single source-pumped full-color lasers. We further reveal that these lasers can operate in quasi-steady state regime, which is very practical and cost-effective. Given the facile solution processibility, our CsPbX3 IPNC-VCSEL devices may hold great potential in developing low-cost yet high-performance lasers, promising in revolutionizing the vacuum-based epitaxial semiconductor lasers.
Directory of Open Access Journals (Sweden)
Masato Takiguchi
2017-04-01
Full Text Available We demonstrated sub-wavelength (∼111 nm diameter single nanowire (NW continuous wave (CW lasers on silicon photonic crystal in the telecom-band with direct modulation at 10 Gb/s by optical pumping at cryogenic temperatures. To estimate the small signal response and pseudo-random bit sequence (PRBS modulation of our CW lasers, we employed a new signal detection technique that employs a superconducting single photon detector and a time-correlated single photon counting module. The results showed that our NW laser was unambiguously modulated at above 10 Gb/s and an open eye pattern was obtained. This is the first demonstration of a telecom-band CW NW laser with high-speed PRBS modulation.
Broadening the applications of the atom probe technique by ultraviolet femtosecond laser
Energy Technology Data Exchange (ETDEWEB)
Hono, K., E-mail: kazuhiro.hono@nims.go.jp [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); CREST, Japan Science and Technology Agency (Japan); Ohkubo, T. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); CREST, Japan Science and Technology Agency (Japan); Chen, Y.M.; Kodzuka, M. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); Oh-ishi, K. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); CREST, Japan Science and Technology Agency (Japan); Sepehri-Amin, H. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); Li, F. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); CREST, Japan Science and Technology Agency (Japan); Kinno, T. [Corporate R and D Center, Toshiba Corporation, Saiwai-ku, Kawasaki 212-8582 (Japan); CREST, Japan Science and Technology Agency (Japan); Tomiya, S.; Kanitani, Y. [Advanced Materials Laboratory, Sony Corporation, Atsugi, Kanagawa 243-0021 (Japan)
2011-05-15
Laser assisted field evaporation using ultraviolet (UV) wavelength gives rise to better mass resolution and signal-to-noise ratio in atom probe mass spectra of metals, semiconductors and insulators compared to infrared and green lasers. Combined with the site specific specimen preparation techniques using the lift-out and annular Ga ion milling in a focused ion beam machine, a wide variety of materials including insulating oxides can be quantitatively analyzed by the three-dimensional atom probe using UV laser assisted field evaporation. After discussing laser irradiation conditions for optimized atom probe analyses, recent atom probe tomography results on oxides, semiconductor devices and grain boundaries of sintered magnets are presented. -- Research highlights: {yields} Application of ultraviolet (UV) femtosecond pulsed laser in a three dimensional atom probe (3DAP). {yields} Improved mass resolution and signal-to-noise ratio in atom probe mass spectra using UV laser. {yields} UV laser facilitates 3DAP analysis of insulating oxides. {yields} Quantitative analysis of wide variety of materials including insulating oxides using UV femotosecond laser.
Wavelength encoding technique for particle analyses in hematology analyzer
Rongeat, Nelly; Brunel, Patrick; Gineys, Jean-Philippe; Cremien, Didier; Couderc, Vincent; Nérin, Philippe
2011-07-01
The aim of this study is to combine multiple excitation wavelengths in order to improve accuracy of fluorescence characterization of labeled cells. The experimental demonstration is realized with a hematology analyzer based on flow cytometry and a CW laser source emitting two visible wavelengths. A given optical encoding associated to each wavelength allows fluorescence identification coming from specific fluorochromes and avoiding the use of noisy compensation method.
Effects of near ultraviolet and green radiations on plant growth
Energy Technology Data Exchange (ETDEWEB)
Klein, R.M.; Edsall, P.C.; Gentile, A.C.
1965-01-01
Selective removal of near ultraviolet and green wavelengths from white light permitted enhanced growth of marigold, tomato, corn, and Impatiens plants, Chlamydomonas cells and the mycelium of Sordaria. Additions of near ultraviolet and green radiations caused repressions in the growth of marigold and Sordaria. These wavelengths do not alter the oxidative mechanisms of mitochondria, intact algal cells or marigold leaf tissues. The capacity for chlorophyll and carotenoid synthesis by Euglena cells was unaffected by these wavelengths. 23 references, 2 figures, 4 tables.
Full aperture backscatter signal analysis of laser with hohlraum on Shenguang II laser facility
International Nuclear Information System (INIS)
Jiao Chunye; Wang Feng; Liu Shenye; Jiang Xiaohua; Li Sanwei; Liu Yonggang; Yang Jiamin; Gu Yuqiu; Wang Chuanke
2010-01-01
Full aperture backscatter system and experimental measurement of hohlraum with 351 nm wavelength laser on Shenguang II laser facility is reported. FABS optical path has been analyzed and the backscattering light completely entered FABS collecting optical path. FABS existed the background light when the eight beams symmetrically acted on hohlraum. The background light is composed of 526.5 nm and 1053 nm wavelength remains while the 1053 nm wavelength changes into 351 nm wavelength, according to records of laser sensitive paper and optical filter. The background light accounts for 15% of FABS energy from experimental measurement result. (authors)
Laser-activated protein solder for peripheral nerve repair
Trickett, Rodney I.; Lauto, Antonio; Dawes, Judith M.; Owen, Earl R.
1995-05-01
A 100 micrometers core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the albumin based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 +/- 5 min. (n equals 20) compared to 23 +/- 9 min. (n equals 10) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 +/- 5 g, while microsutured nerves had a tensile strength of 40 +/- 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study is under way comparing laser solder repaired tibial nerves to conventional microsuture repair. At the time of submission 15 laser soldered nerves and 7 sutured nerves were characterized at 3 months and showed successful regeneration with compound muscle action potentials of 27 +/- 8 mV and 29 +/- 8 mW respectively. A faster, less damaging and long lasting laser based anastomotic technique is presented.
Choice of Eye-Safe Radiation Wavelength in UV and Near IR Spectral Bands for Remote Sensing
Directory of Open Access Journals (Sweden)
M. L. Belov
2016-01-01
Full Text Available The introduction of laser remote sensing systems carries a particular risk to the human’s sense of vision. A structure of the eye, and especially the retina, is the main critical organ as related to the laser radiation.The work uses the optical models of the atmosphere, correctly working in both the UV and the near-IR band, to select the eye-safe radiation wavelengths in the UV (0.355 m and near-IR (~ 1.54 and ~ 2 m spectral bands from the point of view of recorded lidar signal value to fulfill the tasks of laser sensing the natural formations and laser aerosol sensing in the atmosphere.It is shown that the remote sensing lasers with appropriate characteristics can be selected both in the UV band (at a wavelength of 0.355 μm and in the near-IR band (at wavelengths of 1.54 ~ or ~ 2 μm.Molecular scattering has its maximum (for the selected wavelength at a wavelength of 0.355 μm in the UV band, and the minimum at the wavelengths of 1.54 and 2.09 μm in the near -IR band. The main contribution to the molecular absorption at a wavelength of 0.355 μm is made by ozone. In the near-IR spectral band the radiation is absorbed due to water vapor and carbon dioxide.Calculations show that the total effect of the molecular absorption and scattering has no influence on radiation transmission for both the wavelength of 0.355 μm in the UV band, and the wavelengths of 1.54 and 2.09 μm in the near-IR band for sensing trails ~ 1 km.One of the main factors of laser radiation attenuation in the Earth's atmosphere is radiation scattering by aerosol particles.The results of calculations at wavelengths of 0.355 μm, 1.54 μm and 2.09 μm for the several models of the atmosphere show that a choice of the most effective (in terms of the recorded signal of lidar and eye-safe radiation wavelength depends strongly on the task of sensing.To fulfill the task of laser sensing the natural formations, among the eye-safe wavelengths there is one significantly advantageous
Safety and Efficacy of a 1550nm/1927nm Dual Wavelength Laser for the Treatment of Photodamaged Skin.
Narurkar, Vic A; Alster, Tina S; Bernstein, Eric F; Lin, Tina J; Loncaric, Anya
2018-01-01
BACKGROUND: Fractional photothermolysis (FP) is a popular treatment option for photodamaged skin and addresses shortcomings of ablative skin resurfacing and nonablative dermal remodeling. Previous studies have demonstrated that FP using the 1550nm wavelength has led to improvement of ultrastructural changes and clinical effects associated with photodamaged skin in the deeper dermal structures, while treatment with the 1927nm wavelength has shown clinical effects in the superficial dermis. Both wavelengths produce precise microscopic treatment zones (MTZs) in the skin. The two wavelengths used in combination may optimize the delivery of fractional nonablative resurfacing intended for dermal and epidermal coagulation of photodamage skin. OBJECTIVES: To evaluate the safety and efficacy of a 1550/1927 Laser System (Fraxel Dual, Solta), using both 1550nm and 1927nm wavelengths in combination for treatment of facial and non-facial photodamage. METHODS: Prospective, multi-center, post-market study in subjects with clinically identifiable photodamage (N=35) (Fitzpatrick skin types I-IV). Both 1550nm and 1927nm wavelengths were used at each treatment visit. Investigator assessment of the affected area(s) occurred at one week, one month and 3 months after a series of up to four treatments. Severity of adverse events (AEs) were assessed using a 4-point scale (where 0=none and 3=marked). Assessments included erythema, edema, hyperkeratosis, hyper- and hypo-pigmentation, scarring, itchiness, dryness, and flaking. Severity of photoaging, fine and coarse wrinkling, mottled hyperpigmentation, sallowness, and tactile roughness at baseline was assessed using the same scale. Investigators and subjects assessed overall appearance of photodamage and pigmentation based on a 5-point quartile improvement scale at all follow-up visits (where 0=no improvement and 4=very significant improvement [76%-100%]). RESULTS: There was a positive treatment effect at all study visits, with moderate
Narusawa, Shin-ya; Aota, Tatusya; Kishimoto, Ryo
2018-04-01
In the case of radio SETI, there are predicted frequencies which extraterrestrial beings select to send messages to other civilizations. Those are called ;magic frequencies. Considering the optical region, terrestrial technologies can not transmit arbitrary wavelengths of high-power optical lasers, easily. In this article, we discuss communications among civilizations with the same level of technology as us to enhance the persuasive power. It might be possible to make a reasonable assumption about the laser wavelengths transmitted by extraterrestrial intelligences to benefit optical SETI (OSETI) methods. Therefore, we propose some ;magic wavelengths; for spectroscopic OSETI observations in this article. From the senders point of view, we argue that the most favorable wavelength used for interstellar communication would be the one of YAG lasers, at 1.064 μm or its Second Harmonic Generation (532.1 nm). On the contrary, there are basic absorption lines in the optical spectra, which are frequently observed by astrophysicists on Earth. It is possible that the extraterrestrials used lasers, which wavelengths are tuned to such absorption lines for sending messages. In that case, there is a possibility that SHG and/or Sum Frequency Generation of YAG and YLF lasers are used. We propose three lines at, 393.8 nm (near the Ca K line), 656.5 nm (near the Hα line) and 589.1 nm (Na D2 line) as the magic wavelengths.
Improved photochemotherapy of malignant cells with daunomycin and the KTP laser.
Paiva, M B; Saxton, R E; Graeber, I P; Jongewaard, N; Eshraghi, A A; Suh, M J; Paek, W H; Castro, D J
1998-01-01
Laser photochemotherapy of malignancies may become an effective palliative treatment for advanced had and neck cancer using light-sensitive, chemotherapeutic drugs activated in tumors via interstitial laser fiberoptics. Previously, it was reported that cultured human P3 squamous cells incubated 2 hours with daunomycin (Dn) exhibited tenfold enhanced cytotoxicity after exposure to argon laser light at 514 nm. This short-term uptake leads to drug localization in cytoplasmic and membrane sites prior to nuclear accumulation and daunomycin topoisomerase inhibition. In the current study phototoxicity of Dn-sensitized human cancer cells was tested using broad-spectrum white light compared to monochromatic green-wavelength light. Drug uptake and laser energy levels were optimized for maximum synergy. To test light-enhanced chemotherapy in vitro, the kinetics of cell uptake and toxicity of daunomycin was measured at 1, 2, and 5 microg/ml in three human tumor cell lines: P3 squamous-cell carcinoma, M26 melanoma, and TE671 fibrosarcoma. After 2 hr Dn uptake, all cell lines were tested for phototherapy response by exposure to 300- to 900-nm visible light from a xenon lamp or monochromatic 532-nm green light from a KTP laser. When the KTP laser output was varied from 0 to 120 Joules in Dn-sensitized tumor cells, a linear phototherapy response was seen with energy as low as 12 J inducing drug phototoxicity. These results provide evidence that daunomycin cytotoxicity is enhanced when exposed to 532-nm laser illumination in the three tumor types tested and confirm that the response is related to both energy level and drug dose.
Orange fiber laser for ophthalmology
Adachi, M.; Kojima, K.; Hayashi, K.
2007-02-01
For the light source of photocoagulators for ophthalmology, orange laser is more suitable than green laser because of low scattering loss by the crystalline lens, and low absorption by xanthophylls in the retina. We developed two orange fiber lasers (580 nm and 590 nm) to investigate the effect depending on the difference in the range of orange. The 580nm laser is composed of a 1160 nm fiber laser and a Periodically Polled Lithium Niobate (PPLN) crystal for second harmonic generation. The 1160 nm fiber laser beam is focused into the MgO-doped PPLN crystal whose length is 30 mm with 3-pass configuration. Continuous-wave 1.3 W output power of 580 nm was obtained with 5.8 W input power of 1160nm for the first time. The conversion efficiency was 22%. The band width of the second harmonic was 0.006 nm (FWHM). The 590 nm laser is almost the same as 580 nm laser source. In this case we used a Raman shift fiber to generate 1180 nm, and the output power of 590 nm was 1.4 W. We developed an evaluation model of photocoagulator system using these two laser sources. A 700 mW coagulation output power was obtained with this orange fiber laser photocoagulator system. This is enough power for the eye surgery. We have the prospect of the maintenance-free, long-life system that is completely air-cooled. We are planning to evaluate this photocoagulator system in order to investigate the difference between the two wavelengths at the field test.
Osticioli, I.; Mascalchi, M.; Pinna, D.; Siano, S.
2015-03-01
The periodical removal of biodeteriogens is a fundamental need for the preservation of outdoor stone cultural heritage, which is stimulating significant efforts toward the development of low-impact conservation strategies. In the present work, the potential of laser removal of Verrucaria nigrescens Pers. from Carrara marble and the evaluation of the associated biocide effect on the organism residues embedded in the surface texture and through the outer porosities of the stone substrate were investigated. The fundamental wavelength of Nd:YAG laser (1,064 nm), commonly used in stone cleaning, and its second harmonic (532 nm) were comparatively tested. The phenomenology of laser treatments carried out in different irradiation conditions was characterized using optical, epifluorescence, and electron microscopes along with chlorophyll fluorescence with pulsed amplitude-modulated imaging. The results achieved show that 532 nm can provide significant advantages with respect to 1,064 nm. The potential of the latter against the biodeteriogens appears rather limited because of the low optical absorption, whereas the former can allow effective and practicable laser treatments, which disclose a significant application perspective.
Liu, Yang; Zhong, Kai; Mei, Jialin; Jin, Shuo; Ge, Meng; Xu, Degang; Yao, Jianquan
2018-02-01
A compact and flexible dual-wavelength laser with combined two laser crystals (a-cut and c-cut Nd:YLF) as the gain media under coaxially laser-diode (LD) end-pumping configuration was demonstrated and μW-level THz wave was generated based on difference frequency generation (DFG) in a GaSe crystal. The dynamics of coaxial pumping dualwavelength laser was theoretically investigated, showing that the power ratio and pulse interval for both wavelengths could be tuned by balancing the gains at both wavelengths via tuning pump focal position. Synchronized orthogonal 1047/1053 nm laser pulses were obtained and optimal power ratio was realized with the total output power of 2.92W at 5 kHz pumped by 10-W LD power. With an 8-mm-long GaSe crystal, 0.93 μW THz wave at 1.64 THz (182 μm) was generated. Such coaxially LD end-pumped lasers can be extended to various combinations of neodymium doped laser media to produce different THz wavelengths for costless and portable applications.
International Nuclear Information System (INIS)
Mandelbaum, P.; Seely, J.F.; Kania, D.R.; Kauffman, R.L.
1992-01-01
This work extends a previous analysis of the x-ray spectrum of a laser-produced uranium plasma [P. Mandelbaum et al., Phys. Rev. A 44, 5752 (1991)] to the longer-wavelength range (3.8 +65 ) through As-like (U +59 ) isoelectronic sequences are identified in the spectrum, in good agreement with the previous analysis of the spectrum emitted at shorter wavelengths
CO2 laser and plasma microjet process for improving laser optics
Brusasco, Raymond M.; Penetrante, Bernardino M.; Butler, James A.; Grundler, Walter; Governo, George K.
2003-09-16
A optic is produced for operation at the fundamental Nd:YAG laser wavelength of 1.06 micrometers through the tripled Nd:YAG laser wavelength of 355 nanometers by the method of reducing or eliminating the growth of laser damage sites in the optics by processing the optics to stop damage in the optics from growing to a predetermined critical size. A system is provided of mitigating the growth of laser-induced damage in optics by virtue of very localized removal of glass and absorbing material.
Carrier transport in THz quantum cascade lasers: Are Green's functions necessary?
Energy Technology Data Exchange (ETDEWEB)
Matyas, A; Jirauschek, C [Emmy Noether Research Group ' Modeling of Quantum Cascade Devices' , TU Muenchen, D-80333 Muenchen (Germany); Kubis, T [Walter Schottky Institute, TU Muenchen, D-85748 Garching (Germany); Lugli, P, E-mail: alparmat@mytum.d [Institute of Nanoelectronics, TU Muenchen, D-80333 Muenchen (Germany)
2009-11-15
We have applied two different simulation models for the stationary carrier transport and optical gain analysis in resonant phonon depopulation THz Quantum Cascade Lasers (QCLs), based on the semiclassical ensemble Monte Carlo (EMC) and fully quantum mechanical non-equilibrium Green's functions (NEGF) method, respectively. We find in the incoherent regime near and above the threshold current a qualitative and quantitative agreement of both methods. Therefore, we show that THz-QCLs can be successfully optimized utilizing the numerically efficient EMC method.
Observation of Rayleigh - Taylor growth to short wavelengths on Nike
International Nuclear Information System (INIS)
Pawley, C.J.; Bodner, S.E.; Dahlburg, J.P.; Obenschain, S.P.; Schmitt, A.J.; Sethian, J.D.; Sullivan, C.A.; Gardner, J.H.; Aglitskiy, Y.; Chan, Y.; Lehecka, T.
1999-01-01
The uniform and smooth focal profile of the Nike KrF laser [S. Obenschain et al., Phys. Plasmas 3, 2098 (1996)] was used to ablatively accelerate 40 μm thick polystyrene planar targets with pulse shaping to minimize shock heating of the compressed material. The foils had imposed small-amplitude sinusoidal wave perturbations of 60, 30, 20, and 12.5 μm wavelength. The shortest wavelength is near the ablative stabilization cutoff for Rayleigh - Taylor growth. Modification of the saturated wave structure due to random laser imprint was observed. Excellent agreement was found between the two-dimensional simulations and experimental data for most cases where the laser imprint was not dominant. copyright 1999 American Institute of Physics
Macdougal, Michael; Geske, Jon; Wang, Chad; Follman, David
2011-06-01
We describe the factors that go into the component choices for a short wavelength IR (SWIR) imager, which include the SWIR sensor, the lens, and the illuminator. We have shown the factors for reducing dark current, and shown that we can achieve well below 1.5 nA/cm2 for 15 μm devices at 7 °C. In addition, we have mated our InGaAs detector arrays to 640×512 readout integrated integrated circuits to make focal plane arrays (FPAs). The resulting FPAs are capable of imaging photon fluxes with wavelengths between 1 and 1.6 μm at low light levels. The dark current associated with these FPAs is extremely low, exhibiting a mean dark current density of 0.26 nA/cm2 at 0 °C. Noise due to the readout can be reduced from 95 to 57 electrons by using off-chip correlated double sampling. In addition, Aerius has developed laser arrays that provide flat illumination in scenes that are normally light-starved. The illuminators have 40% wall-plug efficiency and provide low-speckle illumination, and provide artifact-free imagery versus conventional laser illuminators.
Progress in Cherenkov femtosecond fiber lasers
DEFF Research Database (Denmark)
Liu, Xiaomin; Svane, Ask Sebastian; Lægsgaard, Jesper
2016-01-01
systems are highlighted—dependent on the realization scheme, the Cherenkov lasers can generate the femtosecond output tunable across the entire visible and even the UV range, and for certain designs more than 40% conversion efficiency from the pump to Cherenkov signal can be achieved. The femtosecond......We review the recent developments in the field of ultrafast Cherenkov fiber lasers. Two essential properties of such laser systems—broad wavelength tunability and high efficiency of Cherenkov radiation wavelength conversion are discussed. The exceptional performance of the Cherenkov fiber laser...... Cherenkov laser with all-fiber architecture is presented and discussed. Operating in the visible range, it delivers 100–200 fs wavelength-tunable pulses with multimilliwatt output power and exceptionally low noise figure an order of magnitude lower than the traditional wavelength tunable supercontinuumbased...
Temperature stabilization of injection lasers
International Nuclear Information System (INIS)
Albanese, A.
1987-01-01
Apparatus which stabilizes the temperature, and thereby the output wavelength, of an injection laser. Means monitor the laser terminal voltage across a laser and derive a voltage therefrom which is proportional to the junction voltage of the laser. Means compares the voltage to a reference value from source and a temperature controller adjusts the laser temperature in response to the results of the comparison. Further embodiments of the present invention vary the output wavelength of the laser by varying the reference value from source against which the laser junction voltage is compared. (author)
Scaling model for high-aspect-ratio microballoon direct-drive implosions at short laser wavelengths
International Nuclear Information System (INIS)
Schirmann, D.; Juraszek, D.; Lane, S.M.; Campbell, E.M.
1992-01-01
A scaling model for hot spherical ablative implosions in direct-drive mode is presented. The model results have been compared with experiments from LLE, ILE, and LLNL. Reduction of the neutron yield due to illumination nonuniformities is taken into account by the assumption that the neutron emission is cut off when the gas shock wave reflected off the center meets the incoming pusher, i.e., at a time when the probability of shell breakup is greatly enhanced. The main advantage of this semiempirical scaling model is that it elucidates the principal features of these simple implosions and permits one to estimate very quickly the performance of a high-aspect-ratio direct-drive target illuminated by short-wavelength laser light. (Author)
Double wavelength differential absorption as a technique for early diagnosis of breast cancer
Liger, Vladimir V.; Zybin, Alexander V.; Niemax, Kay; Kuritsyn, Yuri A.; Bolshov, Mikhail A.
2005-08-01
The double-wavelength differential molecular absorption technique with diode lasers is proposed for sensitive detection of functional status of breast tissues. The method is based on the measurement of the transmitted intensity differences of the two beams of diode lasers tuned to selected wavelengths within a broad absorption band of a human breast tissue within 700 - 800 nm spectral range. The strategy for the optimum selection of the diode laser wavelengths and initial adjustment of the detection scheme is developed. The method is demonstrated by the detection of the relative concentrations of two dyes, the optical properties of which are similar to those of a mixture of oxy- and deoxy- hemoglobin. The results of the first clinical tests of the proposed technique are briefly described.
International Nuclear Information System (INIS)
Wrobel, W.G.
1981-02-01
The electron-beam-pumped argon eximer laser is investigated and tuned for the first time. The electron beam is generated by means of an improved coaxial field emmision diode in which argon gas is excited with power densities of 0.3 GW/cm 3 for 18 ns. The processes in the excited gas of 20 to 65 bar are described in the context of a kinetic model as a sequence of stationary states. Investigations of the amplified spontaneous emission (superfluorescence) confirm the predictions of this model. Only the absorption due to the excited Ar atoms is anomalously high. Reproducible operation of the argon eximer laser was achieved in a wide pressure range with various resonator arrangements. The wavelength of this shortest wavelength of this shortest wavelength excimer laser is 126 nm, the laser line width approx. 1.7 nm, the pulse length 7 to 13 ns, and the laser power 250 kW. The laser emission is tuned from 123.2 nm to 128.4 nm by two different methods (diffraction grating and prism). This tunable laser is thus the one with the shortest wavelength at present. Its line width is 0.25 to 0.4 nm, and the power ue 1.7 kW. (orig.)
Rivera-Ortega, Uriel; Dirckx, Joris
2016-09-01
A low-cost and fully automated process for phase-shifting interferometry by continuously changing and turning on-off the input voltage of a laser diode under the scheme of an unbalanced Twyman-Green interferometer setup is presented. The input signal of a laser diode is controlled by a Data Acquisition (NI-DAQ) device which permits to change its wavelength according to its tunability features. The automation and data analysis will be done using LabVIEW in combination with MATLAB. By using Carré algorithm the phase map is obtained. Measurements of visibility and phase-shift to verify the PSI requirements are also shown.
Wavelength stabilisation during current pulsing of tapered laser
DEFF Research Database (Denmark)
Jensen, Ole Bjarlin
2009-01-01
The use of external feedback to stabilise the frequency of a tapered laser during current pulsing is reported. Using this technique more than 20 W of peak power in 60 ns pulses from the tapered laser is obtained and owing to the external feedback, the laser is tunable in the 778-808 nm range...
Experimental study of laser-plasma interaction physics with short laser wavelength
International Nuclear Information System (INIS)
Labaune, C.; Amiranoff, F.; Fabre, E.; Matthieussent, G.; Rousseaux, C.; Baton, S.
1989-01-01
Many non-linear processes can affect laser-plasma coupling in fusion experiments. The interaction processes of interest involve three or more waves, including the incident electromagnetic wave and various selections of electromagnetic, electrostatic and accoustic waves. Whenever plasma waves are involved (stimulated Raman scattering, two-plasmon decay instability, parametric decay instability and others), energetic electrons are created through the various damping processes of these waves: these energetic electrons in turn deleteriously affect the compression phase in laser fusion experiments through pre-heating of the fuel core. Some parametric processes lead primarily to loss of incident laser energy (stimulated Brillouin scattering) while others, such as filamentation, lead to strongly enhanced local laser intensities through the focusing of part (or all) of the laser beam into filaments of very small dimensions with a concomitant expulsion of the plasma out of these regions. So filamentation destroys the uniformity of energy deposition in the plasma and prevents high compression efficiency of the target. These interaction effects are typically of parametric nature, with their thresholds and growth rates depending critically on plasma scale lengths. Since these scale lengths increase with available laser energy and since millimeter sized plasmas are expected from reactor targets which will be used in direct drive implosion experiments, a good understanding of these processes and their saturation mechanisms becomes imperative. We report here the results on absolute energy measurements and time-resolved spectra of SRS and SBS obtained in various types of plasmas where the major changes were the inhomogeneity scale lengths. (author) 7 refs., 7 figs
Stutzki, Fabian; Gaida, Christian; Gebhardt, Martin; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas; Pupeza, Ioachim
2017-02-01
Ultrashort-pulse laser systems are an enabling technology for numerous applications. The stability of such systems is especially crucial for frequency metrology and high precision spectroscopy. Thulium-based fiber lasers are an ideal starting point as a reliable and yet powerful source for the nonlinear conversion towards the mid-IR region. Recently, we have demonstrated that nonlinear self-compression in a fused silica solid-core fiber allows for few-cycle pulse duration with up to 24 MW peak power using a high-repetition rate thulium-based fiber laser system operating at around 2 μm wavelength [1]. This experiment operates near the self-focusing limit of about 24 MW for circular polarization, which increases the requirements for the system stability due to the risk of a fiber damage. Here, we present a self-protecting nonlinear compression regime allowing for long-term operation and high output-pulse stability with very similar output performance.
Directory of Open Access Journals (Sweden)
Pukhraj Rishi
2012-01-01
Full Text Available A 69-year-old lady presented with complaints of decreased vision in left eye since one month. Best Corrected Visual Acuity (BCVA was 6/18 in that eye. Fundus examination revealed non-central geographic atrophy and soft drusens at macula in both eyes. Temporal periphery of left eye revealed subretinal exudates with altered sub-RPE hemorrhage mimicking peripheral exudative hemorrhagic chorioretinopathy (PEHCR. Fundus Fluorescein Angiogram showed window defects at macula and blocked fluorescence at temporal periphery in left eye. However, Indocyanine green angiography (ICGA revealed active peripheral choroidal polyps. The patient was successfully treated with intravitreal bevacizumab and ICGA-guided laser photocoagulation. 27 months after laser treatment, BCVA improved to 6/9. Rationale of consecutive anti-vascular endothelial growth factor (VEGF treatment followed by more definitive laser photocoagulation is that anti-VEGF aids in resolution of subretinal fluid, thus making the polyp more amenable to focal laser photocoagulation which stabilizes the choroidal vasculature and prevents further leakage.
Auger coefficient in GaInN-based laser structures
Energy Technology Data Exchange (ETDEWEB)
Draeger, Alexander Daniel; Netzel, Carsten; Brendel, Moritz; Joenen, Holger; Rossow, Uwe; Hangleiter, Andreas [Institut fuer Angewandte Physik, TU Braunschweig (Germany)
2010-07-01
Todays GaInN-based light emitting devices such as LEDs and laser diodes show excellent properties in terms of quantum efficiency or threshold current in the violet-blue spectral region. With increasing wavelength towards the green this performance decreases strongly. In particular at longer wavelengths, the quantum efficiency decreases for higher current densities, called the efficiency droop. This phenomenon is still subject to intensive research and different mechanisms such as Auger recombination, losses due to dislocations and carrier escape have been named as possible explanations. We combine optical gain measurements using the variable stripe length technique with model calculations of the optical gain spectra to derive the carrier lifetime. From the dependence of the inverse effective lifetime on carrier density we determine the recombination coefficients for radiative, nonradiative and Auger recombination. The Auger coefficients we obtained are about 1-2 x 10{sup -31} cm{sup 6}/s for GaInN quantum wells with 2.5eV
International Nuclear Information System (INIS)
De Jesus, Joel; Gayen, Swapan K.; Garcia, Thor A.; Tamargo, Maria C.; Kartazaev, Vladimir; Jones, Brynmor E.; Schlosser, Peter J.; Hastie, Jennifer E.
2015-01-01
We report the structural and optical properties of molecular beam epitaxy grown II-VI semiconductor multiple quantum well (MQW) structures and distributed Bragg reflector (DBR) on InP substrates for application in developing optically-pumped semiconductor disk lasers (SDLs) operating in the green spectral range. One sample was grown directly on an InP substrate with an InGaAs buffer layer, while another had a 5-period ZnCdMgSe-based DBR grown on the InGaAs/InP substrate. X-ray diffraction and scanning electron microscopy measurements revealed sharp superlattice peaks and abrupt layer interfaces, while steady-state photoluminescence measurements demonstrated surface emission between 540-570 nm. Under pulsed excitation both samples exhibited features of amplified spontaneous emission (ASE) or stimulated emission, accompanied by luminescence lifetime shortening. The sample with the DBR showed higher surface luminescence and the onset of ASE at lower pump power. To further explore the design and performance of a ZnCdMgSe-based DBR, a 20-period DBR was grown and a reflectivity of 83% was obtained at ∝560 nm. We estimate that a DBR with ∝40 periods would be needed for optimal performance in a SDL using these materials. These results show the potential of II-VI MQW structures on InP substrates for the development of SDLs operational in the green-yellow wavelength range. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
21 CFR 1040.10 - Laser products.
2010-04-01
... radiation means laser radiation having a time-varying direction, origin or pattern of propagation with... this paragraph. (2) Beam of multiple wavelengths in same range. Laser or collateral radiation having... results in the maximum sum. (3) Beam with multiple wavelengths in different ranges. Laser or collateral...
Improvement in QEPAS system utilizing a second harmonic based wavelength calibration technique
Zhang, Qinduan; Chang, Jun; Wang, Fupeng; Wang, Zongliang; Xie, Yulei; Gong, Weihua
2018-05-01
A simple laser wavelength calibration technique, based on second harmonic signal, is demonstrated in this paper to improve the performance of quartz enhanced photoacoustic spectroscopy (QEPAS) gas sensing system, e.g. improving the signal to noise ratio (SNR), detection limit and long-term stability. Constant current, corresponding to the gas absorption line, combining f/2 frequency sinusoidal signal are used to drive the laser (constant driving mode), a software based real-time wavelength calibration technique is developed to eliminate the wavelength drift due to ambient fluctuations. Compared to conventional wavelength modulation spectroscopy (WMS), this method allows lower filtering bandwidth and averaging algorithm applied to QEPAS system, improving SNR and detection limit. In addition, the real-time wavelength calibration technique guarantees the laser output is modulated steadily at gas absorption line. Water vapor is chosen as an objective gas to evaluate its performance compared to constant driving mode and conventional WMS system. The water vapor sensor was designed insensitive to the incoherent external acoustic noise by the numerical averaging technique. As a result, the SNR increases 12.87 times in wavelength calibration technique based system compared to conventional WMS system. The new system achieved a better linear response (R2 = 0 . 9995) in concentration range from 300 to 2000 ppmv, and achieved a minimum detection limit (MDL) of 630 ppbv.
Five Wavelength DFB Fibre Laser Source for WDM Systems
DEFF Research Database (Denmark)
Hübner, Jörg; Varming, Poul; Kristensen, Martin
1997-01-01
Singlemode UV-induced distributed feedback (DFB) fibre lasers with a linewidth of lasers is verified by a 10 Gbit/s transmission experiment. Five DFB fibre lasers are cascaded and pumped by a single...... semiconductor laser, thereby forming a multiwavelength source for WDM systems...
Development of short pulse laser pumped x-ray lasers
International Nuclear Information System (INIS)
Dunn, J; Osterheld, A L; Hunter, J R; Shlyaptsev, V N
2000-01-01
X-ray lasers have been extensively studied around the world since the first laboratory demonstration on the Novette laser at LLNL in 1984 [l]. The characteristic properties of short wavelength, high monochromaticity, collimation and coherence make x-ray lasers useful for various applications. These include demonstrations of biological imaging within the water window, interferometry of laser plasmas and radiography of laser-heated surfaces. One of the critical issues has been the high power pump required to produce the inversion. The power scaling as a function of x-ray laser wavelength follows a -k4 to law. The shortest x-ray laser wavelength of ∼ 35 (angstrom) demonstrated for Ni-like All was at the limit of Nova laser capabilities. By requiring large, high power lasers such as Nova, the shot rate and total number of shots available have limited the rapid development of x-ray lasers and applications. In fact over the last fifteen years the main thrust has been to develop more efficient, higher repetition rate x-ray lasers that can be readily scaled to shorter wavelengths. The recent state of progress in the field can be found in references. The objective of the project was to develop a soft x-ray laser (XRL) pumped by a short pulse laser of a few joules. In effect to demonstrate a robust, worlung tabletop x-ray laser at LLNL for the first time. The transient collisional scheme as proposed by Shlyaptsev et al [8, 9] was the candidate x-ray laser for study. The successful endeavour of any scientific investigation is often based upon prudent early decisions and the choice of this scheme was both sound and fruitful. It had been demonstrated very recently for Ne-like Ti at 326 A using a small tabletop laser [10] but had not yet reached its full potential. We chose this scheme for several reasons: (a) it was a collisional-type x-ray laser which has been historically the most robust; (b) it had the promise of high efficiency and low energy threshold for lasing; (c) the
International Nuclear Information System (INIS)
Fowler, W. Craig; Rose, John G.; Chang, Daniel H.; Proia, Alan D.
1999-01-01
Introduction. In laser vision correction surgery, lasers are generally utilized based on their beam-tissue interactions and corneal absorption characteristics. Therefore, the free electron laser, with its ability to provide broad wavelength tunability, is a unique research tool for investigating wavelengths of possible corneal ablation. Methods. Mark III free electron laser wavelengths between 2.94 and 6.7 μm were delivered in serial 0.1 μm intervals to corneas of freshly enucleated porcine globes. Collateral damage, ablation depth, and ablation diameter were measured in histologic sections. Results. The least collateral damage (12-13 μm) was demonstrated at three wavelengths: 6.0, 6.1 (amide I), and 6.3 μm. Minimal collateral damage (15 μm) was noted at 2.94 μm (OH-stretch) and at 6.2 μm. Slightly greater collateral damage was noted at 6.45 μm (amide II), as well as at the 5.5-5.7 μm range, but this was still substantially less than the collateral damage noted at the other wavelengths tested. Conclusions. Our results suggest that select mid-infrared wavelengths have potential for keratorefractive surgery and warrant additional study. Further, the free electron laser's ability to allow parameter adjustment in the far-ultraviolet spectrum may provide unprecedented insights toward establishing the gold-standard parameters for laser vision correction surgery
Polarization methods for diode laser excitation of solid state lasers
Holtom, Gary R.
2008-11-25
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. A Yb-doped gain medium can be used that absorbs light having a first polarization and emits light having a second polarization. Using such pumping with laser cavity dispersion control, pulse durations of less than 100 fs can be achieved.
International Nuclear Information System (INIS)
Menon, P.S.; Kandiah, K.; Burhanuddin Yeop Majlis; Shaari, S.
2011-01-01
Long-wavelength vertical-cavity surface-emitting lasers (LW-VCSELs) have profound advantages compared to traditional edge-emitting lasers offering improved properties with respect to mode selectivity, fibre coupling, threshold currents and integration into 2D arrays or with other electronic devices. Its commercialization is gaining momentum as the local and access network in optical communication system expand. Numerical modeling of LW-VCSEL utilizing wafer-fused InP-based multi-quantum wells (MQW) and GaAs-based distributed Bragg reflectors (DBRs) is presented in this paper. Emphasis is on the device and mesa/pillar diameter design parameter comparison and its effect on the device characteristics. (author)
Corneal tissue welding with infrared laser irradiation after clear corneal incision.
Rasier, Rfat; Ozeren, Mediha; Artunay, Ozgür; Bahçecioğlu, Halil; Seçkin, Ismail; Kalaycoğlu, Hamit; Kurt, Adnan; Sennaroğlu, Alphan; Gülsoy, Murat
2010-09-01
The aim of this study was to investigate the potential of infrared lasers for corneal welding to seal corneal cuts done in an experimental animal model. Full-thickness corneal cuts on freshly enucleated bovine eyes were irradiated with infrared (809-nm diode, 980-nm diode, 1070-nm YLF, and 1980-nm Tm:YAP) lasers to get immediate laser welding. An 809-nm laser was used with the topical application of indocyanine green to enhance the photothermal interaction at the weld site. In total, 60 bovine eyes were used in this study; 40 eyes were used in the first part of the study for the determination of optimal welding parameters (15 eyes were excluded because of macroscopic carbonization, opacification, or corneal shrinkage; 2 eyes were used for control), and 20 eyes were used for further investigation of more promising lasers (YLF and Tm:YAP). Laser wavelength, irradiating power, exposure time, and spot size were the dose parameters, and optimal dose for immediate closure with minimal thermal damage was estimated through histological examination of welded samples. In the first part of the study, results showed that none of the applications was satisfactory. Full-thickness success rates were 28% (2 of 7) for 809-nm and for 980-nm diode lasers and 67% (2 of 3) for 1070-nm YLF and (4 of 6) for 1980-nm Tm:YAP lasers. In the second part of the study, YLF and Tm:YAP lasers were investigated with bigger sample size. Results were not conclusive but promising again. Five corneal incisions were full-thickness welded out of 10 corneas with 1070-nm laser, and 4 corneal incisions were partially welded out of 10 corneas with 1980-nm laser in the second part of the study. Results showed that noteworthy corneal welding could be obtained with 1070-nm YLF laser and 1980-nm Tm:YAP laser wavelengths. Furthermore, in vitro and in vivo studies will shed light on the potential usage of corneal laser welding technique.
Differential tissue expression of enhanced green fluorescent protein in ‘Green mice’
Ma, De-Fu; Tezuka, Hideo; Kondo, Tetsuo; Sudo, Katsuko; Niu, Dong-Feng; Nakazawa, Tadao; Kawasaki, Tomonori; Yamane, Tetsu; Nakamura, Nobuki; Katoh, Ryohei
2010-01-01
In order to clarify tissue expression of enhanced green fluorescent protein (EGFP) in ‘green mice’ from a transgenic line having an EGFP cDNA under the control of a chicken beta-actin promoter and cytomegalovirus enhancer, we studied the expression of EGFP in various organs and tissues from these ‘green mice’ by immunohistochemistry with anti- EGFP antibody in conjunction with direct observation for EGFP fluorescence using confocal laser scanning microscopy. On i...
Bathymetry from fusion of airborne hyperspectral and laser data
Kappus, Mary E.; Davis, Curtiss O.; Rhea, W. Joseph
1998-10-01
Airborne hyperspectral and nadir-viewing laser data can be combined to ascertain shallow water bathymetry. The combination emphasizes the advances and overcomes the disadvantages of each method used alone. For laser systems, both the hardware and software for obtaining off-nadir measurement are complicated and expensive, while for the nadir view the conversion of laser pulse travel time to depth is straightforward. The hyperspectral systems can easily collect data in a full swath, but interpretation for water depth requires careful calibration and correction for transmittance through the atmosphere and water. Relative depths are apparent in displays of several subsets of hyperspectral data, for example, single blue-green wavelengths, endmembers that represent the pure water component of the data, or ratios of deep to shallow water endmembers. A relationship between one of these values and the depth measured by the aligned nadir laser can be determined, and then applied to the rest of the swath to obtain depth in physical units for the entire area covered. We demonstrate this technique using bathymetric charts as a proxy for laser data, and hyperspectral data taken by AVIRIS over Lake Tahoe and Key West.
Zwick, Harry; Zuclich, Joseph A.; Stuck, Bruce E.; Gagliano, Donald A.; Lund, David J.; Glickman, Randolph D.
1995-01-01
We have evaluated acute laser retinal exposure in non-human primates using a Rodenstock scanning laser ophthalmoscope (SLO) equipped with spectral imaging laser sources at 488, 514, 633, and 780 nm. Confocal spectral imaging at each laser wavelength allowed evaluation of the image plane from deep within the retinal vascular layer to the more superficial nerve fiber layer in the presence and absence of the short wavelength absorption of the macular pigment. SLO angiography included both fluorescein and indocyanine green procedures to assess the extent of damage to the sensory retina, the retinal pigment epithelium (RPE), and the choroidal vasculature. All laser exposures in this experiment were from a Q-switched Neodymium laser source at an exposure level sufficient to produce vitreous hemorrhage. Confocal imaging of the nerve fiber layer revealed discrete optic nerve sector defects between the lesion site and the macula (retrograde degeneration) as well as between the lesion site and the optic disk (Wallerian degeneration). In multiple hemorrhagic exposures, lesions placed progressively distant from the macula or overlapping the macula formed bridging scars visible at deep retinal levels. Angiography revealed blood flow disturbance at the retina as well as at the choroidal vascular level. These data suggest that acute parafoveal laser retinal injury can involve both direct full thickness damage to the sensory and non-sensory retina and remote nerve fiber degeneration. Such injury has serious functional implications for both central and peripheral visual function.
Discretely tunable micromachined injection-locked lasers
International Nuclear Information System (INIS)
Cai, H; Yu, M B; Lo, G Q; Kwong, D L; Zhang, X M; Liu, A Q; Liu, B
2010-01-01
This paper reports a micromachined injection-locked laser (ILL) to provide tunable discrete wavelengths. It utilizes a non-continuously tunable laser as the master to lock a Fabry–Pérot semiconductor laser chip. Both lasers are integrated into a deep-etched silicon chip with dimensions of 3 mm × 3 mm × 0.8 mm. Based on the experimental results, significant improvements in the optical power and spectral purity have been achieved in the fully locked state, and optical hysteresis and bistability have also been observed in response to the changes of the output wavelength and optical power of the master laser. As a whole system, the micromachined ILL is able to provide single mode, discrete wavelength tuning, high power and direct modulation with small size and single-chip solution, making it promising for advanced optical communications such as wavelength division multiplexing optical access networks.
Moran-Lopez, J. L.; Ortiz, M. E.; Rodriguez, L. F.; Romero-Rochin, V.
2010-01-01
The experimental examination applied in the 40th International Physics Olympiad held in Merida, Yucatan, Mexico, is presented. The examination consisted of two parts: (1) based on the measurements of a diffraction pattern produced by a diode laser impinging on a sharp edge of a razor blade, the students were asked to estimate the wavelength of the…
External-cavity high-power dual-wavelength tapered amplifier with tunable THz frequency difference
DEFF Research Database (Denmark)
Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael
2012-01-01
A tunable 800 nm high-power dual-wavelength diode laser system with double-Littrow external-cavity feedback is demonstrated. The two wavelengths can be tuned individually, and the frequency difference of the two wavelengths is tunable from 0.5 to 5.0 THz. A maximum output power of 1.54 W is achie......A tunable 800 nm high-power dual-wavelength diode laser system with double-Littrow external-cavity feedback is demonstrated. The two wavelengths can be tuned individually, and the frequency difference of the two wavelengths is tunable from 0.5 to 5.0 THz. A maximum output power of 1.54 W...... is achieved with a frequency difference of 0.86 THz, the output power is higher than 1.3 W in the 5.0 THz range of frequency difference, and the amplified spontaneous emission intensity is more than 20 dB suppressed in the range of frequency difference. The beam quality factor M2 is 1.22±0.15 at an output...
Action spectrum for photobleaching of human lenses by short wavelength visible irradiation
DEFF Research Database (Denmark)
Kessel, Line; Larsen, Michael
2015-01-01
transmission with increasing laser irradiation. CONCLUSIONS: For a 75 year old lens an effect corresponding to elimination of 15 years or more of optical ageing was obtained. This study of the spectral characteristics and intensity needed to bleach the human lens with single-photon laser effects found...... an action-spectrum peak at 420 nm tailing gradually off toward longer wavelengths and more steeply toward shorter wavelengths. The results may be used to guide experiments with two-photon bleaching....
Laser pumped lasers for isotope separation
International Nuclear Information System (INIS)
Fry, S.M.
1976-01-01
A study of the isotope separation laser requirements reveals that high pressure polyatomic molecular gas laser pumped lasers can attain the necessary characteristics including tunability, energy output, pulse width, and repetition rate. The results of a search, made for molecules meeting the appropriate requirements for one of several pump schemes utilizing a CO 2 laser and with output in the 12 μm or 16μm wavelength range, are presented. Several methods of pumping are reviewed and two novel pump schemes are presented. A laser pumped laser device design is given, and operation of this device and associated diagnostic equipment is confirmed by repeating experiments in OCS and NH 3 . The results of OCS laser experiments show that an improvement in pump rate and output per unit length is obtained with the device, using a wedged transverse pumping scheme. A new multi-line laser system in NH 3 pumped by a TEA CO 2 laser is reported. More than forty transitions spanning the wavelength range of 9.2 to 13.8 μm are observed and identified. A strong output at 12.08 μm is one of the closest lines yet found to the required laser isotope separation wavelength. Far infrared emission near 65 μm is observed and is responsible for populating levels which lase in pure ammonia near 12.3 μm. Buffer gas (e.g., N 2 or He) pressures of approximately 40--800 torr cause energy transfer by collision-induced rotationaltransitions from the pumped antisymmetric to the lasing symmetric levels in the nu 2 = 1 band of ammonia. Most of the observed lines are aP(J,K) transitions which originate from the nu 2 /sup s/ band. Measurements of the pressure dependence of the laser output shows that some lines lase at pressures greater than one atmosphere. Transient behavior of the 12.08 μm line is calculated from a simplified analytic model and these calculations are compared to the experimental results
Directory of Open Access Journals (Sweden)
Wilson Michael
2008-07-01
Full Text Available Abstract Background The increase in resistance to antibiotics among disease-causing bacteria necessitates the development of alternative antimicrobial approaches such as the use of light-activated antimicrobial agents (LAAAs. Light of an appropriate wavelength activates the LAAA to produce cytotoxic species which can then cause bacterial cell death via loss of membrane integrity, lipid peroxidation, the inactivation of essential enzymes, and/or exertion of mutagenic effects due to DNA modification. In this study, the effect of the LAAA indocyanine green excited with high or low intensity light (808 nm from a near-infrared laser (NIR on the viability of Staphylococcus aureus, Streptococcus pyogenes and Pseudomonas aeruginosa was investigated. Results All species were susceptible to killing by the LAAA, the bactericidal effect being dependent on both the concentration of indocyanine green and the light dose. Indocyanine green photosensitization using both high (1.37 W cm-2 and low (0.048 W cm-2 intensity NIR laser light was able to achieve reductions of 5.6 log10 (>99.99% and 6.8 log10 (>99.99% in the viable counts of Staph. aureus and Strep. pyogenes (using starting concentrations of 106–107 CFU ml-1. Kills of 99.99% were obtained for P. aeruginosa (initial concentration 108–109 CFU ml-1 photosensitized by the high intensity light (1.37 W cm-2; while a kill of 80% was achieved using low intensity irradiation (0.07 W cm-2. The effects of L-tryptophan (a singlet oxygen scavenger and deuterium oxide (as an enhancer of the life span of singlet oxygen on the survival of Staph. aureus was also studied. L-tryptophan reduced the proportion of Staph. aureus killed; whereas deuterium oxide increased the proportion killed suggesting that singlet oxygen was involved in the killing of the bacteria. Conclusion These findings imply that indocyanine green in combination with light from a near-infrared laser may be an effective means of eradicating bacteria
International Nuclear Information System (INIS)
Piper, L.G.; Krech, R.H.; Pugh, E.; Taylor, R.L.
1979-01-01
The feasibility of producing an efficient, short wavelength, storage laser for ICF driven applications by making use of certain state-specific reactions of exoergic azide compounds has been investigated. The ultraviolet (approx. 300 nm) photolysis of gaseous ClN 3 produced prompt emission in the red, which was attributed to the efficient formation of ClN(b 1 Σ + ) with subsequent ClN(X reverse arrow b) fluorescence. Based on these results, a small-scale laser demonstration experiment was constructed using short duration Xe flash lamps as the photolytic source. The results of this latter experiment were negative. The most plausible explanation was that the flash lamps provided sufficient far-uv radiation to dissociate and/or ionize the ClN(b) produced in the primary photolytic step. In parallel, limited experiments were performed on the rapid pyrolysis of a solid, ionic azide, NaN 3 , to produce gaseous N 3 radicals and subsequent production of triplet N 2 molecules
Tunable Microfluidic Dye Laser
DEFF Research Database (Denmark)
Olsen, Brian Bilenberg; Helbo, Bjarne; Kutter, Jörg Peter
2003-01-01
We present a tunable microfluidic dye laser fabricated in SU-8. The tunability is enabled by integrating a microfluidic diffusion mixer with an existing microfluidic dye laser design by Helbo et al. By controlling the relative flows in the mixer between a dye solution and a solvent......, the concentration of dye in the laser cavity can be adjusted, allowing the wavelength to be tuned. Wavelength tuning controlled by the dye concentration was demonstrated with macroscopic dye lasers already in 1971, but this principle only becomes practically applicable by the use of microfluidic mixing...
International Nuclear Information System (INIS)
Nakano, H.; Goto, M.; Tsumori, K.; Kisaki, M.; Ikeda, K.; Nagaoka, K.; Osakabe, M.; Takeiri, Y.; Kaneko, O.; Nishiyama, S.; Sasaki, K.
2015-01-01
The velocity distribution function of hydrogen atoms is one of the useful parameters to understand particle dynamics from negative hydrogen production to extraction in a negative hydrogen ion source. Hydrogen atom temperature is one of the indicators of the velocity distribution function. To find a feasibility of hydrogen atom temperature measurement in large scale filament arc negative hydrogen ion source for fusion, a model calculation of wavelength-modulated laser absorption spectroscopy of the hydrogen Balmer alpha line was performed. By utilizing a wide range tunable diode laser, we successfully obtained the hydrogen atom temperature of ∼3000 K in the vicinity of the plasma grid electrode. The hydrogen atom temperature increases as well as the arc power, and becomes constant after decreasing with the filling of hydrogen gas pressure