nm laser beam: Topics by Science.gov

Sample records for nm laser beam

Photonic Breast Tomography and Tumor Aggressiveness Assessment

DTIC Science & Technology

2012-07-01

c) Raw Image 11 The entrance face of the slab sample (source plane) was illuminated by a 100-mW 790-nm diode laser beam. The multi-source...schematically shown in Figure 6. A 10mW 785 nm diode laser beam was used to illuminate the first sample, while a 100mW 785 nm diode laser beam was used for the...signal transmitting narrow-band filter; TS = translation stage; CCD = charge cou- pled device; and PC = computer. Continuous wave 790-nm diode laser
Generation and use of high power 213 nm and 266 nm laser radiation and tunable 210-400 nm laser radiation with BBO crystal matrix array

DOEpatents

Gruen, Dieter M.

2000-01-01

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

NASA Astrophysics Data System (ADS)

Sudheer, S. K.; Pillai, V. P. Mahadevan; Nayar, V. U.

2006-12-01

Advances in Laser Technology and nonlinear Optical techniques can be effectively utilized for LIDAR applications in space and atmospheric sciences to achieve better flexibility and control of the available optical power. Using such devices, one can achieve highly accurate and resolved, measurement of the distribution for atmospheric scattering layers. In the present investigation a diode double end pumped high repetition rate, multi wavelength Nd:YAG laser is designed, fabricated and various laser beam parameters have been characterized for LIDAR applications. Nonlinear optical techniques have been employed to generate higher harmonics like 532nm, 355nm and 266nm for various spectral studies. The experimental setup mainly consists of two Fiber coupled pump laser diodes (Model FAP- 81-30C-800B, Coherent Inc, USA) with a maximum output power of 30Watt at a wavelength of 807-810nm at 30°C set temperature. A second harmonic LBO crystal cut for critical phase matching placed within the laser resonator is provided for converting a fraction of the fundamental beam to a second harmonic beam. A type II frequency tripling LBO nonlinear crystal (cut for critical phase matching) is also located inside the laser resonator. The third harmonic beam and the unconverted fundamental beam are then directed across a type I fourth harmonic LBO crystal cut for critical phase matching where a portion of the fundamental beam and a portion of the third harmonic beam are converted to a fourth harmonic frequency when both fundamental and third harmonic beams propagate through the frequency quadrupling crystal. The resulting beams which are the fundamental (1064nm), second harmonic (532nm), third harmonic (355nm) and fourth harmonic (266nm) are then directed to a fourth harmonic separator in which the fourth harmonic beam is separated from the fundamental beam. A maximum average power of 12W at 1064nm, 8W at 532nm, 5W at 355nm and 3W at 266nm have been measured at a repetition rate of 10KHz. A minimum pulse width of 25ns have been observed.
Compact dual-wavelength Nd:GdVO4 laser working at 1063 and 1065 nm.

PubMed

Wu, Bo; Jiang, Peipei; Yang, Dingzhong; Chen, Tao; Kong, Jian; Shen, Yonghang

2009-04-13

We report a compact diode-laser pumped Nd:GdVO(4) laser with stable dual-wavelength output at 1063 nm and 1065 nm simultaneously. Two types of resonant cavity configurations were presented to support the stable dual-wavelength operation of the laser. Using a polarization beam splitter(PBS) included T-shaped cavity, we obtained a total power output over 5 W in two orthogonal polarized beam directions with 4 W in sigma polarization (1065.5 nm) and 1 W in pi polarization (1063.1 nm). By combining a half-wave-plate with the PBS in the laser cavity, a new configuration favoring one beam direction dual-wavelength output with same polarization direction was realized. A phenomenon of further line splitting was observed in both 1065 nm and 1063 nm.
Green high-power tunable external-cavity GaN diode laser at 515 nm.

PubMed

Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael

2016-09-15

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.
5.7 W cw single-frequency laser at 671 nm by single-pass second harmonic generation of a 17.2 W injection-locked 1342 nm Nd : YVO4 ring laser using periodically poled MgO : LiNbO3.

PubMed

Koch, Peter; Ruebel, Felix; Bartschke, Juergen; L'huillier, Johannes A

2015-11-20

We demonstrate a continuous wave single-frequency laser at 671.1 nm based on a high-power 888 nm pumped Nd:YVO4 ring laser at 1342.2 nm. Unidirectional operation of the fundamental ring laser is achieved with the injection-locking technique. A Nd:YVO4 microchip laser serves as the injecting seed source, providing a tunable single-frequency power of up to 40 mW. The ring laser emits a single-frequency power of 17.2 W with a Gaussian beam profile and a beam propagation factor of M2<1.1. A 60-mm-long periodically poled MgO-doped LiNbO3 crystal is used to generate the second harmonic in a single-pass scheme. Up to 5.7 W at 671.1 nm with a Gaussian shaped beam profile and a beam propagation factor of M2<1.2 are obtained, which is approximately twice the power of previously reported lasers. This work opens possibilities in cold atoms experiments with lithium, allowing the use of larger ensembles in magneto-optical traps or higher diffraction orders in atomic beam interferometers.
Nanoparticles based laser-induced surface structures formation on mesoporous silicon by picosecond laser beam interaction

NASA Astrophysics Data System (ADS)

Talbi, A.; Petit, A.; Melhem, A.; Stolz, A.; Boulmer-Leborgne, C.; Gautier, G.; Defforge, T.; Semmar, N.

2016-06-01

In this study, laser induced periodic surface structures were formed on mesoporous silicon by irradiation of Nd:YAG picosecond pulsed laser beam at 266 nm wavelength at 1 Hz repetition rate and with 42 ps pulse duration. The effects of laser processing parameters as laser beam fluence and laser pulse number on the formation of ripples were investigated. Scanning electron microscopy and atomic force microscopy were used to image the surface morphologies and the cross section of samples after laser irradiation. At relatively low fluence ∼20 mJ/cm2, ripples with period close to the laser beam wavelength (266 nm) and with an always controlled orientation (perpendicular to the polarization of ps laser beam) appeared after a large laser pulse number of 12,000. It has been found that an initial random distribution of SiOx nanoparticles is periodically structured with an increase of the laser pulse number. Finally, it is experimentally demonstrated that we formed a 100 nm liquid phase under the protusion zones including the pores in the picosecond regime.
Wide spectral band beam analysis

NASA Astrophysics Data System (ADS)

Aharon, Oren

2015-03-01

The reality in laser beam profiling is that measurements are performed over a wide spectrum of wavelengths and power ranges. Many applications use multiple laser wavelengths with very different power levels, a fact which dictates a need for a better measuring tool. Rapid progress in the fiber laser area has increased the demand for lasers in the wavelength range of 900 - 1030 nm, while the telecommunication market has increased the demand for wavelength range of 1300nm - 1600 nm, on the other hand the silicone chip manufacturing and mass production requirements tend to lower the laser wavelength towards the 190nm region. In many cases there is a need to combine several lasers together in order to perform a specific task. A typical application is to combine one visible laser for pointing, with a different laser for material processing with a very different wavelength and power level. The visible laser enables accurate pointing before the second laser is operated. The beam profile of the intensity distribution is an important parameter that indicates how a laser beam will behave in an application. Currently a lab, where many different lasers are used, will find itself using various laser beam profilers from several vendors with different specifications and accuracies. It is the propose of this article to present a technological breakthrough in the area of detectors, electronics and optics allowing intricate measurements of lasers with different wavelength and with power levels that vary many orders of magnitude by a single beam profiler.
Widely tunable short-infrared thulium and holmium doped fluorozirconate waveguide chip lasers.

PubMed

Lancaster, D G; Gross, S; Withford, M J; Monro, T M

2014-10-20

We report widely tunable (≈ 260 nm) Tm(3+) and Ho(3+) doped fluorozirconate (ZBLAN) glass waveguide extended cavity lasers with close to diffraction limited beam quality (M(2) ≈ 1.3). The waveguides are based on ultrafast laser inscribed depressed claddings. A Ti:sapphire laser pumped Tm(3+)-doped chip laser continuously tunes from 1725 nm to 1975 nm, and a Tm(3+)-sensitized Tm(3+):Ho(3+) chip laser displays tuning across both ions evidenced by a red enhanced tuning range of 1810 to 2053 nm. We also demonstrate a compact 790 nm diode laser pumped Tm(3+)-doped chip laser which tunes from 1750 nm to 1998 nm at a 14% incident slope efficiency, and a beam quality of M(2) ≈ 1.2 for a large mode-area waveguide with 70 µm core diameter.
Researching the 915 nm high-power and high-brightness semiconductor laser single chip coupling module

NASA Astrophysics Data System (ADS)

Wang, Xin; Wang, Cuiluan; Wu, Xia; Zhu, Lingni; Jing, Hongqi; Ma, Xiaoyu; Liu, Suping

2017-02-01

Based on the high-speed development of the fiber laser in recent years, the development of researching 915 nm semiconductor laser as main pumping sources of the fiber laser is at a high speed. Because the beam quality of the laser diode is very poor, the 915 nm laser diode is generally based on optical fiber coupling module to output the laser. Using the beam-shaping and fiber-coupling technology to improve the quality of output beam light, we present a kind of high-power and high-brightness semiconductor laser module, which can output 13.22 W through the optical fiber. Based on 915 nm GaAs semiconductor laser diode which has output power of 13.91 W, we describe a thoroughly detailed procedure for reshaping the beam output from the semiconductor laser diode and coupling the beam into the optical fiber of which the core diameter is 105 μm and the numerical aperture is 0.18. We get 13.22 W from the output fiber of the module at 14.5 A, the coupling efficiency of the whole module is 95.03% and the brightness is 1.5 MW/cm2 -str. The output power of the single chip semiconductor laser module achieves the advanced level in the domestic use.
The effects of TGG crystal length on output power and beam quality of a unidirectional ring Nd:YVO4 laser with and without second harmonic generation

NASA Astrophysics Data System (ADS)

Ahmadi, A.; Avazpour, A.; Nadgaran, H.; Mousavi, M.

2018-04-01

The effect of terbium gallium garnet (TGG ) crystal length on 1064 and 532 nm output powers and beam quality of a unidirectional ring Nd:YVO4 laser is investigated. In the case of 1064 nm (without nonlinear crystal), the laser output power without considerating the effect of TGG crystal was computed theoretically. Then three TGG crystals with different lengths were placed in the laser setup one by one. A systematic decrease in output power was observed by increasing the TGG crystal length. The experiment was repeated in the case of 532 nm. It was found that in a 532 nm laser, higher laser efficiency and small beam quality degradation can be achieved by increasing the TGG crystal length leading to a 5.7 W green laser with 27 W pump power. The power stability and beam quality were 0.8% for 30 min and less than 1.3, respectively.
Mode coupling enhancement by astigmatism compensation in a femtosecond laser cavity

NASA Astrophysics Data System (ADS)

Castro-Olvera, Gustavo; Garduño-Mejía, Jesus; Rosete-Aguilar, Martha; Roman-Moreno, Carlos J.

2016-09-01

In this work we present a numerical analysis of the mode coupling between the pump-beam and the laser-beam in a Ti:Sapphire crystal used as a gain medium of a femtosecond laser. Using the Matrix ABCD and propagation gaussian beam models, we obtained an optimal configuration for compensate the astigmatism in the output beam laser. Also we analysed pump-beam propagation and got the settings to fix the astigmatism in the crystal. Furthermore we apply this configuration to a homemade femtosecond laser, accomplishing an overall efficiency of laser to 20% in continuum wave (CW) and 16% in mode looking (ML) operation. The femtosecond laser have 30 nm bandwidth to FWHM at 810 nm corresponding 30fs.
Development of Two-Photon Pump Polarization Spectroscopy Probe Technique Tpp-Psp for Measurements of Atomic Hydrogen .

NASA Astrophysics Data System (ADS)

Satija, Aman; Lucht, Robert P.

2015-06-01

Atomic hydrogen (H) is a key radical in combustion and plasmas. Accurate knowledge of its concentration can be used to better understand transient phenomenon such as ignition and extinction in combustion environments. Laser induced polarization spectroscopy is a spatially resolved absorption technique which we have adapted for quantitative measurements of H atom. This adaptation is called two-photon pump, polarization spectroscopy probe technique (TPP-PSP) and it has been implemented using two different laser excitation schemes. The first scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-3P levels using a circularly polarized 656-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 656 nm. As a result, the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. The laser beams were created by optical parametric generation followed by multiple pulse dye amplification stages. This resulted in narrow linewidth beams which could be scanned in frequency domain and varied in energy. This allowed us to systematically investigate saturation and Stark effect in 2S-3P transitions with the goal of developing a quantitative H atom measurement technique. The second scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-4P transitions using a circularly polarized 486-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 486 nm. As a result the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. A dye laser was pumped by third harmonic of a Nd:YAG laser to create a laser beam at 486 nm. The 486-nm beam was frequency doubled to a 243-nm beam. Use of the second scheme simplifies the TPP-PSP technique making it more convenient for diagnostics in practical systems.
Development of infrared sensors using energy transfer/energy upconversion processes: Study of laser excited fluorescence in rare Earth ion doped crystals

NASA Technical Reports Server (NTRS)

Nash-Stevenson, S. K.; Reddy, B. R.; Venkateswarlu, P.

1994-01-01

A summary is presented of the spectroscopic study of three systems: LaF3:Ho(3+), LaF3:Er(3+) and CaF2:Nd(3+). When the D levels of Ho(3+) in LaF3 were resonantly excited with a laser beam of 640 nm, upconverted emissions were detected from J (416 nm), F (485 nm), and E (546 nm) levels. Energy upconverted emissions were also observed from F and E levels of Ho(3+) when the material was excited with an 800 nm near infrared laser. When the D levels of Er(3+) in LaF3 were resonantly excited with a laser beam of 637 nm, upconverted emissions were detected from the E (540 nm) and P (320, 400, and 468 nm) levels. Energy upconverted emissions were also observed from F, E, and D levels of Er(3+) when the material was resonantly excited with an 804 nm near infrared laser. When the D levels of Nd(3+) in CaF2 were resonantly excited with a laser beam of 577 nm, upconverted emissions were detected from the L (360 and 382 nm), K (418 nm), and I (432 nm) levels. Very weak upconverted emissions were detected when this system was irradiated with a near infrared laser. The numbers in parentheses are the wavelengths of the emissions.
Parametric Raman anti-Stokes laser at 503 nm with phase-matched collinear beam interaction of orthogonally polarized Raman components in calcite under 532 nm 20 ps laser pumping

NASA Astrophysics Data System (ADS)

Smetanin, Sergei; Jelínek, Michal; Kubeček, Václav

2017-05-01

Lasers based on stimulated-Raman-scattering process can be used for the frequency-conversion to the wavelengths that are not readily available from solid-state lasers. Parametric Raman lasers allow generation of not only Stokes, but also anti-Stokes components. However, practically all the known crystalline parametric Raman anti-Stokes lasers have very low conversion efficiencies of about 1 % at theoretically predicted values of up to 40 % because of relatively narrow angular tolerance of phase matching in comparison with angular divergence of the interacting beams. In our investigation, to widen the angular tolerance of four-wave mixing and to obtain high conversion efficiency into the antiStokes wave we propose and study a new scheme of the parametric Raman anti-Stokes laser at 503 nm with phasematched collinear beam interaction of orthogonally polarized Raman components in calcite under 532 nm 20 ps laser pumping. We use only one 532-nm laser source to pump the Raman-active calcite crystal oriented at the phase matched angle for orthogonally polarized Raman components four-wave mixing. Additionally, we split the 532-nm laser radiation into the orthogonally polarized components entering to the Raman-active calcite crystal at the certain incidence angles to fulfill the tangential phase matching compensating walk-off of extraordinary waves for collinear beam interaction in the crystal with the widest angular tolerance of four-wave mixing. For the first time the highest 503-nm anti-Stokes conversion efficiency of 30 % close to the theoretical limit of about 40 % at overall optical efficiency of the parametric Raman anti-Stokes generation of up to 3.5 % in calcite is obtained due to realization of tangential phase matching insensitive to the angular mismatch.
Beam shaping by using small-aperture SLM and DM in a high power laser

NASA Astrophysics Data System (ADS)

Li, Sensen; Lu, Zhiwei; Du, Pengyuan; Wang, Yulei; Ding, Lei; Yan, Xiusheng

2018-03-01

High-power laser plays an important role in many fields, such as directed energy weapon, optoelectronic contermeasures, inertial confinement fusion, industrial processing and scientific research. The uniform nearfield and wavefront are the important part of the beam quality for high power lasers, which is conducive to maintaining the high spatial beam quality in propagation. We demonstrate experimentally that the spatial intensity and wavefront distribution at the output is well compensated in the complex high-power solid-state laser system by using the small-aperture spatial light modulator (SLM) and deformable mirror (DM) in the front stage. The experimental setup is a hundred-Joule-level Nd:glass laser system operating at three wavelengths at 1053 nm (1ω), 527 nm (2ω) and 351 nm (3ω) with 3 ns pulse duration with the final output beam aperture of 60 mm. While the clear arperture of the electrically addressable SLM is less than 20 mm and the effective diameter of the 52-actuators DM is about 15 mm. In the beam shaping system, the key point is that the two front-stage beam shaping devices needs to precompensate the gain nonuniform and wavefront distortion of the laser system. The details of the iterative algorithm for improving the beam quality are presented. Experimental results show that output nearfield and wavefont are both nearly flat-topped with the nearfield modulation of 1.26:1 and wavefront peak-to-valley value of 0.29 λ at 1053nm after beam shaping.
High-efficient Nd:YAG microchip laser for optical surface scanning

NASA Astrophysics Data System (ADS)

Šulc, Jan; Jelínková, Helena; Nejezchleb, Karel; Škoda, Václav

2017-12-01

A CW operating, compact, high-power, high-efficient diode pumped 1064nm laser, based on Nd:YAG active medium, was developed for optical surface scanning and mapping applications. To enhance the output beam quality, laser stability, and compactness, a microchip configuration was used. In this arrangement the resonator mirrors were deposited directly on to the laser crystal faces. The Nd-doping concentration was 1 at.% Nd/Y. The Nd:YAG crystal was 5mm long. The laser resonator without pumping radiation recuperation was investigated {the output coupler was transparent for pumping radiation. For the generated laser radiation the output coupler reflectivity was 95%@1064 nm. The diameter of the samples was 5 mm. For the laser pumping two arrangements were investigated. Firstly, a fibre coupled laser diode operating at wavelength 808nm was used in CW mode. The 400 ¹m fiber was delivering up to 14W of pump power amplitude to the microchip laser. The maximum CW output power of 7.2W @ 1064nm in close to TEM00 beam was obtained for incident pumping power 13.7W @ 808 nm. The differential efficiency in respect to the incident pump power reached 56 %. Secondly, a single-emitter, 1W laser diode operating at 808nm was used for Nd:YAG microchip pumping. The laser pumping was directly coupled into the microchip laser using free-space lens optics. Slope efficiency up to 70% was obtained in stable, high-quality, 1064nm laser beam with CW power up to 350mW. The system was successfully used for scanning of super-Gaussian laser mirrors reflectivity profile.
Investigating the effects of laser beams (532 and 660 nm) in annihilation of pistachio mould fungus using spectrophotometry analysis

NASA Astrophysics Data System (ADS)

Saghafi, S.; Penjweini, R.; Becker, K.; Kratky, K. W.; Dodt, H.-U.

2010-09-01

When moulds are illuminated by visible electromagnetic-EM radiations, several effects on nucleus materials and nucleotides can be detected. These effects have a significant influence on mould generation or destruction. This paper presents the effects and implications of a red diode laser beam (660 nm), a second-harmonics of a Nd:YAG laser emitting green beam (532 nm), or the combination of both, on the eradication of Pistachio mould fungus. Incident doses (ID) of both beams are kept identical throughout the experiment. The absorption spectrums of irradiated mouldy samples and the bright-greenish-yellow-fluorescence (BGYF) of fungus occurring in mould texture due to electronic excitation are investigated. We found that a combination of a green and a red laser beam with an ID of 0.5 J/cm2 provides the optimal effects on Pistachio mould fungus eradication.
The Laser Guide Star System for Adaptive Optics at Subaru Telescope

NASA Astrophysics Data System (ADS)

Hayano, Y.; Saito, Y.; Ito, M.; Saito, N.; Akagawa, K.; Takazawa, A.; Ito, M.; Wada, S.; Takami, H.; Iye, M.

We report on the current status of developing the new laser guide star (LGS) system for the Subaru adaptive optics (AO) system. We have three major subsystems: the laser unit, the relay optical fiber and the laser launching telescope. A 4W-class all-solid-state 589nm laser has been developed as a light source for sodium laser guide star. We use two mode-locked Nd:YAG lasers operated at the wavelength of 1064nm and 1319nm to generate sum-frequency conversion into 589nm. The side-LD pumped configuration is used for the mode-locked Nd:YAG lasers. We have carefully considered the thermal lens effect in the cavity to achieve a high beam quality with TEM00; M2 = 1.06. The mode-locked frequency is selected at 143 MHz. We obtained the output powers of 16.5 W and 5.0 W at 1064nm and 1319 nm. Sum frequency generated by mixing two synchronized Nd:YAG mode-locked pulsed beams is precisely tuned to the sodium D2 line by thermal control of the etalon in the 1064nm Nd:YAG laser by observing the maximum fluorescence intensity of heated sodium vapor cell. The maximum output power at 589.159 nm reaches to 4.6 W using a PPMgOSLT crystal as a nonlinear optical crystal. And the output power can be maintained within a stability of +/- 1.2% for more than 3 days without optical damage. We developed a single-mode photonic crystal fiber (PCF) to relay the laser beam from laser clean room, in which the laser unit is located on the Nasmyth platform, to the laser launching telescope mounted behind the secondary mirror of Subaru Telescope. The photonic crystal fiber has solid pure silica core with the mode field diameter of 14 micron, which is relatively larger than that of the conventional step-index type single mode fiber. The length of the PCF is 35m and transmission loss due to the pure silica is 10dB/km at 589nm, which means PCF transmits 92% of the laser beam. We have preliminary achieved 75% throughput in total. Small mode-locked pulse width in time allows us to transmit the high-power laser beam with no suffer from the non-linear scatter effect, i.e. stimulated Brillouin scatter, in the PCF. The laser launching telescope (LLT) has an output clear aperture as 50 cm. It is classical Cassegrain type optical configuration with tertiary mirror to insert the laser beam from the side. The wavefront error is designed to be 60 to 70nm. The LLT is a copy product what European Southern Observatory has been designed for the laser guide star system at Very Large Telescope. We succeeded to launch the laser beam to the sky on October 12, 2006. After several tests on the sky, we succeeded to get an image of the laser guide star with the size of more than 10 arc second. The larger size of the laser guide star is caused by the large optical aberration on the primary mirror of LLT due to the heat stress generated at the trigonal support points. We are making a plan to repair this problem during June and the second laser launching test will start around this summer.
Implementation of a diode-pumped Nd:YAG laser with quick-change output couplers for high-beam quality 1064 or 532 nm wavelength generation

NASA Astrophysics Data System (ADS)

Li, Chun-Hao; Tsai, Ming-Jong

2009-06-01

A novel diode-pumped Nd:YAG laser system that employs a fixed active laser medium and a pair of quick-change output couplers on a precision linear stage for 1064 or 532 nm wavelength generation is presented. Fixed elements include a rear mirror, an acousto-optical Q-switch, and a diode-pumped solid-state laser (DPSSL). Movable elements for 1064 nm generation include an intra-cavity aperture as a mode selection element (MSE) and an output coupler. Movable elements for 532 nm generation include an intra-cavity frequency conversion with KTP, an intra-cavity aperture as a mode selection element (MSE), and an output coupler. Under stable operating conditions, the 1064 nm configuration produced a beam propagation ratio of 1.18 whereas the 532 nm configuration produced a beam propagation ratio of 1.1, both of which used an intra-cavity MSE with an aperture of 1.2 mm and a length of 5 mm.

Gain measurements and spatial coherence in neon-like x-ray lasers

NASA Astrophysics Data System (ADS)

Krishnan, J.; Cairns, C.; Dwivedi, L.; Holden, M.; Key, M. H.; Lewis, C. L. S.; MacPhee, A.; Neely, D.; Norreys, P. A.; Pert, G. J.; Ramsden, S. A.; Smith, C. G.; Tallents, G. J.; Zhang, J.

1995-05-01

Many of the applications with x-ray lasers require high quality output radiation with properties such as short wavelength and a high degree of coherence (longitudinal and spatial). Ne-like Yttrium (Z=39) is potentially a bright and monochromatic XUV lasing medium. The output at 15.5 nm is monochromatic due to the overlap of the J=2-1 and J=0-1 lines. A gain coefficient of 3±1 was obtained at 15.5 nm by irradiating 100 μm wide yttrium stripes at 6×1013 W/cm2 with 1.06 μm, 650 ps pulses from the Rutherford Appleton Laboratory VULCAN laser. We have investigated improving x-ray laser spatial coherence utilizing a series of amplifiers instead of the standard double target configuration. An ``injector-amplifier'' scheme was successfully demonstrated with the Ne-like Ge x-ray laser. A spatially small and coherent part of the 23 nm beam from the standard double target geometry has been relayed using a W/Si multilayer mirror onto a single or double target configuration situated at a distance of ˜1.5 m from the mirror and pumped by two 150 mm diameter beams of VULCAN laser. A beam ``foot-print monitor'' was employed with a flat mirror to relay 23 nm output onto a film pack to record the spatial variation of the x-ray laser beam. Analyzing the fringes obtained through a cross-wire placed in front of the beam shows that an increase in spatial coherence was achieved by adding amplifiers to the x-ray laser beam line.
Laser effect on the 248 nm KrF transition using heavy ion beam pumping

NASA Astrophysics Data System (ADS)

Adonin, A.; Jacoby, J.; Turtikov, V.; Fertman, A.; Golubev, A.; Hoffmann, D. H. H.; Ulrich, A.; Varentsov, D.; Wieser, J.

2007-07-01

In December 2005 the first successful operation of a UV excimer laser pumped with a heavy ion beam was demonstrated at GSI. It was the first experiment in which the specific power deposition was sufficient to overcome laser threshold for a UV excimer scheme. The well known KrF* excimer laser line at λ=248 nm has been chosen for this experiment, because the wavelength is short, but still in the range of usual optical diagnostic tools and the emitted light can propagate in air without attenuation. A bunch compressed U+73238 beam with a particle energy of 250 MeV/u and about 110 ns pulse duration (FWHM) was used for this experiment. Single pulses of a beam intensity up to 2.5×109 particles per bunch were focused into the laser cell along the cavity axis. Compact spectrometers, high speed UV-photodiodes and gated CCD-cameras were used for diagnostics of the spontaneous and stimulated emission. As a main result of the experiment laser effect on the 248 nm KrF* excimer laser line has been obtained and verified by temporal and spectral narrowing of the laser line as well as the threshold behaviour and exponential growth of intensity with increasing pumping power. In summary it could be shown that the pumping power of the heavy ion beam at GSI is now sufficient to pump short wavelength lasers. It is planned to extend laser experiments in near future to the VUV range of the spectrum (λ<200 nm).
Formation of surface nanolayers in chalcogenide crystals using coherent laser beams

NASA Astrophysics Data System (ADS)

Ozga, K.; Fedorchuk, A. O.; El-Naggar, A. M.; Albassam, A. A.; Kityk, V.

2018-03-01

We have shown a possibility to form laser modified surface nanolayers with thickness up to 60 nm in some ternary chalcogenide crystals (Ag3AsS3, Ag3SbS3, Tl3SbS3) The laser treatment was performed by two coherent laser beams split in a space. As the inducing lasers we have applied continuous wave (cw) Hesbnd Cd laser at wavelength 441 nm and doubled frequency cw Nd: YAG laser at 532 nm. The spectral energies of these lasers were higher with respect to the energy gaps of the studied crystals. The optical anisotropy was appeared and defected by monitoring of birefringence at probing wavelength of cw Hesbnd Ne laser at λ = 3390 nm. The changes of the laser stimulated near the surface layer morphology was monitored by TEM and AFM methods as well as by the reflected optical second harmonic generation at fundamental wavelength of microsecond CO2 laser generating at wavelength 10600 nm. This technique may open a new approach for the formation of the near the surface nanolayers in chalcogenides using external cw laser illumination.
589 nm sum-frequency generation laser for the LGS/AO of Subaru Telescope

NASA Astrophysics Data System (ADS)

Saito, Yoshihiko; Hayano, Yutaka; Saito, Norihito; Akagawa, Kazuyuki; Takazawa, Akira; Kato, Mayumi; Ito, Meguru; Colley, Stephen; Dinkins, Matthew; Eldred, Michael; Golota, Taras; Guyon, Olivier; Hattori, Masayuki; Oya, Shin; Watanabe, Makoto; Takami, Hideki; Iye, Masanori; Wada, Satoshi

2006-06-01

We developed a high power and high beam quality 589 nm coherent light source by sum-frequency generation in order to utilize it as a laser guide star at the Subaru telescope. The sum-frequency generation is a nonlinear frequency conversion in which two mode-locked Nd:YAG lasers oscillating at 1064 and 1319 nm mix in a nonlinear crystal to generate a wave at the sum frequency. We achieved the qualities required for the laser guide star. The power of laser is reached to 4.5 W mixing 15.65 W at 1064 nm and 4.99 W at 1319 nm when the wavelength is adjusted to 589.159 nm. The wavelength is controllable in accuracy of 0.1 pm from 589.060 and 589.170 nm. The stability of the power holds within 1.3% during seven hours operation. The transverse mode of the beam is the TEM 00 and M2 of the beam is smaller than 1.2. We achieved these qualities by the following technical sources; (1) simple construction of the oscillator for high beam quality, (2) synchronization of mode-locked pulses at 1064 and 1319 nm by the control of phase difference between two radio frequencies fed to acousto-optic mode lockers, (3) precise tunability of wavelength and spectral band width, and (4) proper selection of nonlinear optical crystal. We report in this paper how we built up each technical source and how we combined those.
Note: Broadly tunable all-fiber ytterbium laser with 0.05 nm spectral width based on multimode interference filter.

PubMed

Mukhopadhyay, Pranab K; Gupta, Pradeep K; Singh, Amarjeet; Sharma, Sunil K; Bindra, Kushvinder S; Oak, Shrikant M

2014-05-01

A multimode interference filter with narrow transmission bandwidth and large self-imaging wavelength interval is constructed and implemented in an ytterbium doped fiber laser in all-fiber format for broad wavelength tunability as well as narrow spectral width of the output beam. The peak transmission wavelength of the multimode interference filter was tuned with the help of a standard in-fiber polarization controller. With this simple mechanism more than 30 nm (1038 nm-1070 nm) tuning range is demonstrated. The spectral width of the output beam from the laser was measured to be 0.05 nm.
Note: Broadly tunable all-fiber ytterbium laser with 0.05 nm spectral width based on multimode interference filter

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Pranab K.; Gupta, Pradeep K.; Singh, Amarjeet; Sharma, Sunil K.; Bindra, Kushvinder S.; Oak, Shrikant M.

2014-05-01

A multimode interference filter with narrow transmission bandwidth and large self-imaging wavelength interval is constructed and implemented in an ytterbium doped fiber laser in all-fiber format for broad wavelength tunability as well as narrow spectral width of the output beam. The peak transmission wavelength of the multimode interference filter was tuned with the help of a standard in-fiber polarization controller. With this simple mechanism more than 30 nm (1038 nm-1070 nm) tuning range is demonstrated. The spectral width of the output beam from the laser was measured to be 0.05 nm.
A Laser Stabilization System for Rydberg Atom Physics

DTIC Science & Technology

2015-09-06

offset locking method which we did. For each system, a small amount of light from a 852 nm (780 nm) diode laser is picked off from the output beam ...this way, tunable sidebands, from 1-10 GHz, that are themselves modulated at .05-5 MHz, can be generated on the input laser beam . The light from the...phase modulation signal. This signal is fed back into the fast (10 MHz bandwidth) locking electronics of the diode laser system to lock the laser to
Narrow linewidth operation of a spectral beam combined diode laser bar.

PubMed

Zhu, Zhanda; Jiang, Menghua; Cheng, Siqi; Hui, Yongling; Lei, Hong; Li, Qiang

2016-04-20

Our experiment is expected to provide an approach for realizing ultranarrow linewidth for a spectral beam combined diode laser bar. The beams of a diode laser bar are combined in a fast axis after a beam transformation system. With the help of relay optics and a transform lens with a long focal length of 1.5 m, the whole wavelength of a spectral combined laser bar can be narrowed down to 0.48 nm from more than 10 nm. We have achieved 56.7 W cw from a 19-element single bar with an M² of 1.4 (in horizontal direction)×11.6 (in vertical direction). These parameters are good evidence that all the beams from the diode laser bar are combined together to increase the brightness.
Multi-wavelength photoacoustic system based on high-power diode laser bars

NASA Astrophysics Data System (ADS)

Leggio, Luca; Wiśniowski, Bartosz; Gawali, Sandeep Babu; Rodríguez, Sergio; Sánchez, Miguel; Gallego, Daniel; Carpintero, Guillermo; Lamela, Horacio

2017-03-01

Multi-wavelength laser sources are necessary for a functional photoacoustic (PA) spectroscopy. The use of high-power diode lasers (HPDLs) has aroused great interest for their relatively low costs and small sizes if compared to solid state lasers. However, HPDLs are only available at few wavelengths and can deliver low optical energy (normally in the order of μJ), while diode laser bars (DLBs) offer more wavelengths in the market and can deliver more optical energy. We show the simulations of optical systems for beam coupling of single high-power DLBs operating at different wavelengths (i.e. 808 nm, 880 nm, 910 nm, 940 nm, and 980 nm) into 400-μm optical fibers. Then, in a separate design, the beams of the DLBs are combined in a compact system making use of dichroic mirrors and focusing lenses for beam coupling into a 400-μm optical fiber. The use of optical fibers with small core diameter (< 1 mm) is particularly suggestive for future photoacoustic endoscopy (PAE) applications that require interior examination of the body.
Generation of the Submicron Soft X-Ray Beam Using a Fresnel Zone Plate

NASA Astrophysics Data System (ADS)

Nishikino, M.; Kawazome, H.; Tanaka, M.; Kishimoto, M.; Hasegawa, N.; Ochi, Y.; Kawachi, T.; Sukegawa, K.; Yamatani, H.; Nagashima, K.; Kato, Y.

We have developed a fully coherent x-ray laser at 13.9 nm and the application research has been started. The generation of submicron x-ray beam is important for the application of high intensity x-ray beam, such as the non-linear optics, the material science, and the biology. The submicron x-ray bee am is generated by the soft x-ray laser with using a Fresnel zone plate. The spot diameter is estimated about 680 nm (290 nm at FWHM) by the theoretical calculation. In this experiment, the diameter of the x-ray beam is measured by the knife-edge scan. The diameter and the intensity are estimated 730 nm (310 nm at FWHM) and 3x1011 W/cm2, respectively.
1030 nm high power polarization maintained fiber laser with narrow linewidth and near-diffraction-limited beam quality

NASA Astrophysics Data System (ADS)

Chu, Qiuhui; Zhao, Pengfei; Li, Chengyu; Wang, Bopeng; Lin, Honghuan; Guo, Chao; Liu, Yu; Jing, Feng; Tang, Chuanxiang

2018-03-01

A high power 1030 nm ytterbium-doped polarization maintained fiber laser with optimized parameters is presented in this paper. The master oscillator power amplifier system with counter-pumped amplifier is established. The output power is 900 W, along with a light-to-light efficiency of 64.2%. The amplified spontaneous emission suppression ratio of spectrum reaches to 40 dB with 3 dB linewidth of 0.14 nm. The polarization extinction ratio is 12 dB, and the beam quality factor is M2x=1.07, M2y=1.12. To the best of our knowledge, this is the first demonstration of 1030 nm high power fiber laser with narrow linewidth, near linear polarization, and neardiffraction-limited beam quality
High-power actively Q-switched single-mode 1342 nm Nd:YVO₄ ring laser, injection-locked by a cw single-frequency microchip laser.

PubMed

Koch, Peter; Bartschke, Juergen; L'huillier, Johannes A

2015-11-30

In this paper we report on the realization of a single-mode Q-switched Nd:YVO₄ ring laser at 1342 nm. Unidirectional and single-mode operation of the ring laser is achieved by injection-locking with a continuous wave Nd:YVO₄ microchip laser, emitting a single-frequency power of up to 40 mW. The ring laser provides a single-mode power of 13.9 W at 10 kHz pulse repetition frequency with a pulse duration of 18.2 ns and an excellent beam quality (M² < 1.05). By frequency doubling of the fundamental 1342 nm laser, a power of 8.7 W at 671 nm with a pulse duration of 14.8 ns and a beam propagation factor of M² < 1.1 is obtained. The 671 nm radiation features a long-term spectral width of 75 MHz.
The study of laser beam riding guided system based on 980nm diode laser

NASA Astrophysics Data System (ADS)

Qu, Zhou; Xu, Haifeng; Sui, Xin; Yang, Kun

2015-10-01

With the development of science and technology, precision-strike weapons has been considered to be important for winning victory in military field. Laser guidance is a major method to execute precision-strike in modern warfare. At present, the problems of primary stage of Laser guidance has been solved with endeavors of countries. Several technical aspects of laser-beam riding guided system have been mature, such as atmosphere penetration of laser beam, clutter inhibition on ground, laser irradiator, encoding and decoding of laser beam. Further, laser beam quality, equal output power and atmospheric transmission properties are qualified for warfare situation. Riding guidance instrument is a crucial element of Laser-beam riding guided system, and is also a vital element of airborne, vehicle-mounted and individual weapon. The optical system mainly consist of sighting module and laser-beam guided module. Photoelectric detector is the most important sensing device of seeker, and also the key to acquire the coordinate information of target space. Currently, in consideration of the 1.06 u m of wavelength applied in all the semi-active laser guided weapons systems, lithium drifting silicon photodiode which is sensitive to 1.06 u m of wavelength is used in photoelectric detector. Compared to Solid and gas laser, diode laser has many merits such as small volume, simple construction, light weight, long life, low lost and easy modulation. This article introduced the composition and operating principle of Laser-beam riding guided system based on 980 nm diode laser, and made a analysis of key technology; for instance, laser irradiator, modulating disk of component, laser zooming system. Through the use of laser diode, Laser-beam riding guided system is likely to have smaller shape and very light.
1-kilowatt CW all-fiber laser oscillator pumped with wavelength-beam-combined diode stacks.

PubMed

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.
System analysis of wavelength beam combining of high-power diode lasers for photoacoustic endoscopy

NASA Astrophysics Data System (ADS)

Leggio, Luca; Gallego, Daniel C.; Gawali, Sandeep B.; Sánchez, Miguel; Rodriguez, Sergio; Osiński, Marek; Sacher, Joachim; Carpintero, Guillermo; Lamela, Horacio

2016-04-01

This paper, originally published on 27 April 2016, was replaced with a corrected/revised version on 8 June 2016. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance. The purpose of wavelength-beam combining (WBC) is to improve the output power of a multi-wavelength laser system while maintaining the quality of the combined beam. This technique has been primarily proposed for industrial applications, such as metal cutting and soldering, which require optical peak power between kilowatts and megawatts. In order to replace the bulkier solid-state lasers, we propose to use the WBC technique for photoacoustic (PA) applications, where a multi-wavelength focused beam with optical peak power between hundreds of watts up to several kilowatts is necessary to penetrate deeply into biological tissues. In this work we present an analytical study about the coupling of light beams emitted by diode laser bars at 808 nm, 880 nm, 910 nm, 940 nm, and 980 nm into a < 600-μm core-diameter optical fiber for PA endoscopy. In order to achieve an efficient coupling it is necessary to collimate the beams in both fast and slow axes by means of cylindrical lenses and to use partial reflection mirrors at 45° tilt. We show an example of beam collimation using cylindrical lenses in both fast and slow axes. In a real PA scenario, the resulting beam should have a sufficient peak power to generate significant PA signals from a turbid tissue>.
Efficient generation of 509 nm light by sum-frequency mixing between two tapered diode lasers

NASA Astrophysics Data System (ADS)

Tawfieq, Mahmoud; Jensen, Ole Bjarlin; Hansen, Anders Kragh; Sumpf, Bernd; Paschke, Katrin; Andersen, Peter E.

2015-03-01

We demonstrate a concept for visible laser sources based on sum-frequency generation of beam combined tapered diode lasers. In this specific case, a 1.7 W sum-frequency generated green laser at 509 nm is obtained, by frequency adding of 6.17 W from a 978 nm tapered diode laser with 8.06 W from a 1063 nm tapered diode laser, inside a periodically poled MgO doped lithium niobate crystal. This corresponds to an optical to optical conversion efficiency of 12.1%. As an example of potential applications, the generated nearly diffraction-limited green light is used for pumping a Ti:sapphire laser, thus demonstrating good beam quality and power stability. The maximum output powers achieved when pumping the Ti:sapphire laser are 226 mW (CW) and 185 mW (mode-locked) at 1.7 W green pump power. The optical spectrum emitted by the mode-locked Ti:sapphire laser shows a spectral width of about 54 nm (FWHM), indicating less than 20 fs pulse width.
Bolt beam propagation analysis

NASA Astrophysics Data System (ADS)

Shokair, I. R.

BOLT (Beam on Laser Technology) is a rocket experiment to demonstrate electron beam propagation on a laser ionized plasma channel across the geomagnetic field in the ion focused regime (IFR). The beam parameters for BOLT are: beam current I(sub b) = 100 Amps, beam energy of 1--1.5 MeV (gamma =3-4), and a Gaussian beam and channel of radii r(sub b) = r(sub c) = 1.5 cm. The N+1 ionization scheme is used to ionize atomic oxygen in the upper atmosphere. This scheme utilizes 130 nm light plus three IR lasers to excite and then ionize atomic oxygen. The limiting factor for the channel strength is the energy of the 130 nm laser, which is assumed to be 1.6 mJ for BOLT. At a fixed laser energy and altitude (fixing the density of atomic oxygen), the range can be varied by adjusting the laser tuning, resulting in a neutralization fraction axial profile of the form: f(z) = f(sub 0) e(exp minus z)/R, where R is the range. In this paper we consider the propagation of the BOLT beam and calculate the range of the electron beam taking into account the fact that the erosion rates (magnetic and inductive) vary with beam length as the beam and channel dynamically respond to sausage and hose instabilities.
Note: Broadly tunable all-fiber ytterbium laser with 0.05 nm spectral width based on multimode interference filter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukhopadhyay, Pranab K., E-mail: pkm@rrcat.gov.in; Gupta, Pradeep K.; Singh, Amarjeet

2014-05-15

A multimode interference filter with narrow transmission bandwidth and large self-imaging wavelength interval is constructed and implemented in an ytterbium doped fiber laser in all-fiber format for broad wavelength tunability as well as narrow spectral width of the output beam. The peak transmission wavelength of the multimode interference filter was tuned with the help of a standard in-fiber polarization controller. With this simple mechanism more than 30 nm (1038 nm–1070 nm) tuning range is demonstrated. The spectral width of the output beam from the laser was measured to be 0.05 nm.
λ/26 silver nanodots fabricated by direct laser writing through highly sensitive two-photon photoreduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Yaoyu; Gu, Min, E-mail: mgu@swin.edu.au

We demonstrated an approach to break the diffraction limit and realise deep-subwavelength two-photon direct laser writing by employing a highly sensitive photoreduction process. The photoreduction photosensitivity increased by at least 4 times while the wavelength of the fabrication laser beam was tuned from 800 nm to 580 nm. The increase of the photosensitivity resulted in improved resolution for the silver dot fabrication. By developing the photoreduction material with adding electron donors, the photosensitivity further increased and enabled the realisation of a single silver dot at 22 nm which is λ/26 for the wavelength of the fabrication laser beam.
High-power linearly-polarized operation of a cladding-pumped Yb fibre laser using a volume Bragg grating for wavelength selection.

PubMed

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.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grubb, Daryl L.; Faircloth, Brian O.; Zediker, Mark S.

A high power laser drilling system utilizing an electric motor laser bottom hole assembly. A high power laser beam travels within the electric motor for performing a laser operation. A system includes a down hole electrical motor having a hollow rotor for conveying a high power laser beam having a wavelength less than 1060 nm through the electrical motor.
LD-pumped erbium and neodymium lasers with high energy and output beam quality

NASA Astrophysics Data System (ADS)

Kabanov, Vladimir V.; Bezyazychnaya, Tatiana V.; Bogdanovich, Maxim V.; Grigor'ev, Alexandr V.; Lebiadok, Yahor V.; Lepchenkov, Kirill V.; Ryabtsev, Andrew G.; Ryabtsev, Gennadii I.; Shchemelev, Maxim A.

2013-05-01

Physical and fabrication peculiarities which provide the high output energy and beam quality for the diode pumped erbium glass and Nd:YAG lasers are considered. Developed design approach allow to make passively Q-switched erbium glass eye-safe portable laser sources with output energy 8 - 12 mJ (output pulse duration is less than 25 ns, pulse repetition rate up to 5 Hz) and beam quality M2 less than 1.3. To reach these values the erbium laser pump unit parameters were optimized also. Namely, for the powerful laser diode arrays the optimal near-field fill-factor, output mirror reflectivity and heterostructure properties were determined. Construction of advanced diode and solid-state lasers as well as the optical properties of the active element and the pump unit make possible the lasing within a rather wide temperature interval (e.g. from minus forty till plus sixty Celsius degree) without application of water-based chillers. The transversally pumped Nd:YAG laser output beam uniformity was investigated depending on the active element (AE) pump conditions. In particular, to enhance the pump uniformity within AE volume, a special layer which practically doesn't absorb the pump radiation but effectively scatters the pump and lasing beams, was used. Application of such layer results in amplified spontaneous emission suppression and improvement of the laser output beam uniformity. The carried out investigations allow us to fabricate the solid-state Nd:YAG lasers (1064 nm) with the output energy up to 420 mJ at the pulse repetition rate up to 30 Hz and the output energy up to 100 mJ at the pulse repetition rate of of 100 Hz. Also the laser sources with following characteristics: 35 mJ, 30 Hz (266 nm); 60 mJ, 30 Hz (355 nm); 100 mJ, 30 Hz (532 nm) were manufactured on the base of the developed Nd:YAG quantrons.
Resonance Raman scattering of β-carotene solution excited by visible laser beams into second singlet state.

PubMed

Lu, Luyao; Shi, Lingyan; Secor, Jeff; Alfano, Robert

2018-02-01

This study aimed to use self-absorption correction to determine the Raman enhancement of β-carotene. The Raman spectra of β-carotene solutions were measured using 488nm, 514nm, 532nm and 633nm laser beams, which exhibited significant resonance Raman (RR) enhancement when the laser energy approaches the electronic transition energy from S 0 to S 2 state. The Raman intensity and the actual resonance Raman gain without self-absorption from S 2 state by β-carotene were also obtained to evaluate the effect of self-absorption on RR scattering. Moreover, we observed the Raman intensity strength followed the absorption spectra. Our study found that, although 488nm and 514nm pumps seemed better for stronger RR enhancement, 532nm would be the optimum Raman pump laser with moderate RR enhancement due to reduced fluorescence and self-absorption. The 532nm excitation will be helpful for applying resonance Raman spectroscopy to investigate biological molecules in tissues. Copyright © 2017 Elsevier B.V. All rights reserved.
Sub-micrometric surface texturing of AZ31 Mg-alloy through two-beam direct laser interference patterning with a ns-pulsed green fiber laser

NASA Astrophysics Data System (ADS)

Furlan, Valentina; Biondi, Marco; Demir, Ali Gökhan; Pariani, Giorgio; Previtali, Barbara; Bianco, Andrea

2017-11-01

Two-beam direct laser interference patterning (DLIP) is the method that employs two beams and provides control over the pattern geometry by regulating the angle between the beams and the wavelength of the beam. Despite the simplistic optical arrangement required for the method, the feasibility of sub-micrometric patterning of a surface depends on the correct manipulation of the process parameters, especially in the case of metallic materials. Magnesium alloys, from this point of view, exhibit further difficulty in processability due to low melting point and high reactivity. With biocompatibility and biodegradability features, Mg-alloy implants can take further advantage of surface structuring for tailoring the biological behaviour. In this work, a two-beam DLIP setup has been developed employing an industrial grade nanosecond-pulsed fiber laser emitting at 532 nm. The high repetition rate and ramped pulse profile provided by the laser were exploited for a more flexible control over the energy content deposited over the heat-sensitive Mg-alloy. The paper describes the strategies developed for controlling ramped laser emission at 20 kHz repetition rate. The process feasibility window was assessed within a large range of parameters. Within the feasibility window, a complete experimental plan was applied to investigate the effect of main laser process parameters on the pattern dimensions. Periodic surface structures with good definition down to 580 nm ± 20 nm spacing were successfully produced.
Diffractive Combiner of Single-Mode Pump Laser-Diode Beams

NASA Technical Reports Server (NTRS)

Liu, Duncan; Wilson, Daniel; Qiu, Yueming; Forouhar, Siamak

2007-01-01

An optical beam combiner now under development would make it possible to use the outputs of multiple single-mode laser diodes to pump a neodymium: yttrium aluminum garnet (Nd:YAG) nonplanar ring oscillator (NPRO) laser while ensuring that the laser operates at only a single desired frequency. Heretofore, an Nd:YAG NPRO like the present one has been pumped by a single multimode laser-diode beam delivered via an optical fiber. It would be desirable to use multiple pump laser diodes to increase reliability beyond that obtainable from a single pump laser diode. However, as explained below, simplistically coupling multiple multimode laser-diode beams through a fiber-optic combiner would entail a significant reduction in coupling efficiency, and lasing would occur at one or more other frequencies in addition to the single desired frequency. Figure 1 schematically illustrates the principle of operation of a laser-diode-pumped Nd:YAG NPRO. The laser beam path is confined in a Nd:YAG crystal by means of total internal reflections on the three back facets and a partial-reflection coating on the front facet. The wavelength of the pump beam - 808 nm - is the wavelength most strongly absorbed by the Nd:YAG crystal. The crystal can lase at a wavelength of either 1,064 nm or 1,319 nm - which one depending on the optical coating on the front facet. A thermal lens effect induced by the pump beam enables stable lasing in the lowest-order transverse electromagnetic mode (the TEM00 mode). The frequency of this laser is very stable because of the mechanical stability of the laser crystal and the unidirectional nature of the lasing. The unidirectionality is a result of the combined effects of (1) a Faraday rotation induced by an externally applied magnetic field and (2) polarization associated with non-normal incidence and reflection on the front facet.
970-nm ridge waveguide diode laser bars for high power DWBC systems

NASA Astrophysics Data System (ADS)

Wilkens, Martin; Erbert, Götz; Wenzel, Hans; Knigge, Andrea; Crump, Paul; Maaßdorf, Andre; Fricke, Jörg; Ressel, Peter; Strohmaier, Stephan; Schmidt, Berthold; Tränkle, Günther

2018-02-01

de lasers are key components in material processing laser systems. While mostly used as pump sources for solid state or fiber lasers, direct diode laser systems using dense wavelength multiplexing have come on the market in recent years. These systems are realized with broad area lasers typically, resulting in beam quality inferior to disk or fiber lasers. We will present recent results of highly efficient ridge waveguide (RW) lasers, developed for dense-wavelength-beamcombining (DWBC) laser systems expecting beam qualities comparable to solid state laser systems and higher power conversion efficiencies (PCE). The newly developed RW lasers are based on vertical structures with an extreme double asymmetric large optical cavity. Besides a low vertical divergence these structures are suitable for RW-lasers with (10 μm) broad ridges, emitting in a single mode with a good beam quality. The large stripe width enables a lateral divergence below 10° (95 % power content) and a high PCE by a comparably low series resistance. We present results of single emitters and small test arrays under different external feedback conditions. Single emitters can be tuned from 950 nm to 975 nm and reach 1 W optical power with more than 55 % PCE and a beam quality of M2 < 2 over the full wavelength range. The spectral width is below 30 pm FWHM. 5 emitter arrays were stabilized using the same setup. Up to now we reached 3 W optical power, limited by power supply, with 5 narrow spectral lines.
Generation of continuous-wave 194 nm laser for mercury ion optical frequency standard

NASA Astrophysics Data System (ADS)

Zou, Hongxin; Wu, Yue; Chen, Guozhu; Shen, Yong; Liu, Qu; Precision measurement; atomic clock Team

2015-05-01

194 nm continuous-wave (CW) laser is an essential part in mercury ion optical frequency standard. The continuous-wave tunable radiation sources in the deep ultraviolet (DUV) region of the spectrum is also serviceable in high-resolution spectroscopy with many atomic and molecular lines. We introduce a scheme to generate continuous-wave 194 nm radiation with SFM in a Beta Barium Borate (BBO) crystal here. The two source beams are at 718 nm and 266 nm, respectively. Due to the property of BBO, critical phase matching (CPM) is implemented. One bow-tie cavity is used to resonantly enhance the 718 nm beam while the 266 nm makes a single pass, which makes the configuration easy to implement. Considering the walk-off effect in CPM, the cavity mode is designed to be elliptical so that the conversion efficiency can be promoted. Since the 266 nm radiation is generated by a 532 nm laser through SHG in a BBO crystal with a large walk-off angle, the output mode is quite non-Gaussian. To improve mode matching, we shaped the 266 nm beam into Gaussian modes with a cylindrical lens and iris diaphragm. As a result, 2.05 mW 194 nm radiation can be generated. As we know, this is the highest power for 194 nm CW laser using SFM in BBO with just single resonance. The work is supported by the National Natural Science Foundation of China (Grant No. 91436103 and No. 11204374).
Efficient Second Harmonic Generation in 3D Nonlinear Optical-Lattice-Like Cladding Waveguide Splitters by Femtosecond Laser Inscription

PubMed Central

Nie, Weijie; Jia, Yuechen; Vázquez de Aldana, Javier R.; Chen, Feng

2016-01-01

Integrated photonic devices with beam splitting function are intriguing for a broad range of photonic applications. Through optical-lattice-like cladding waveguide structures fabricated by direct femtosecond laser writing, the light propagation can be engineered via the track-confined refractive index profiles, achieving tailored output beam distributions. In this work, we report on the fabrication of 3D laser-written optical-lattice-like structures in a nonlinear KTP crystal to implement 1 × 4 beam splitting. Second harmonic generation (SHG) of green light through these nonlinear waveguide beam splitter structures provides the capability for the compact visible laser emitting devices. With Type II phase matching of the fundamental wavelength (@ 1064 nm) to second harmonic waves (@ 532 nm), the frequency doubling has been achieved through this three-dimensional beam splitter. Under 1064-nm continuous-wave fundamental-wavelength pump beam, guided-wave SHG at 532 nm are measured with the maximum power of 0.65 mW and 0.48 mW for waveguide splitters (0.67 mW and 0.51 mW for corresponding straight channel waveguides), corresponding to a SH conversion efficiency of approximately ~14.3%/W and 13.9%/W (11.2%/W, 11.3%/W for corresponding straight channel waveguides), respectively. This work paves a way to fabricate compact integrated nonlinear photonic devices in a single chip with beam dividing functions. PMID:26924255
Efficient Second Harmonic Generation in 3D Nonlinear Optical-Lattice-Like Cladding Waveguide Splitters by Femtosecond Laser Inscription.

PubMed

Nie, Weijie; Jia, Yuechen; Vázquez de Aldana, Javier R; Chen, Feng

2016-02-29

Integrated photonic devices with beam splitting function are intriguing for a broad range of photonic applications. Through optical-lattice-like cladding waveguide structures fabricated by direct femtosecond laser writing, the light propagation can be engineered via the track-confined refractive index profiles, achieving tailored output beam distributions. In this work, we report on the fabrication of 3D laser-written optical-lattice-like structures in a nonlinear KTP crystal to implement 1 × 4 beam splitting. Second harmonic generation (SHG) of green light through these nonlinear waveguide beam splitter structures provides the capability for the compact visible laser emitting devices. With Type II phase matching of the fundamental wavelength (@ 1064 nm) to second harmonic waves (@ 532 nm), the frequency doubling has been achieved through this three-dimensional beam splitter. Under 1064-nm continuous-wave fundamental-wavelength pump beam, guided-wave SHG at 532 nm are measured with the maximum power of 0.65 mW and 0.48 mW for waveguide splitters (0.67 mW and 0.51 mW for corresponding straight channel waveguides), corresponding to a SH conversion efficiency of approximately ~14.3%/W and 13.9%/W (11.2%/W, 11.3%/W for corresponding straight channel waveguides), respectively. This work paves a way to fabricate compact integrated nonlinear photonic devices in a single chip with beam dividing functions.
In situ probing of pulsed laser melting and laser-induced periodic surface structures formation by dynamic reflectivity

NASA Astrophysics Data System (ADS)

Huynh, T. T. D.; Semmar, N.

2017-09-01

The melting process and nanostructure formation induced by nanosecond and picosecond laser pulses on bulk silicon and copper thin film were studied by ex situ analysis and in situ real time reflectivity. Three different probing wavelengths (633, 473 and 326 nm) were used during the pump laser processing and were correlated to the beam parameters (pulse duration, laser fluence and number of laser shots) and copper thin film thickness. On a silicon surface using a KrF laser beam (27 ns, 1 Hz, 248 nm), the melting threshold was determined close to 700 mJ cm-2 and the melting duration increased from 10 to 130 ns as the fluence increased from 700 to 1750 mJ cm-2. Nanostructures with a spatial period close to the laser wavelength were formed on both copper thin film and silicon substrate after nanosecond Nd:YAG laser (10 ns, 266 nm, 1 Hz) irradiation. In the picosecond regime, using an Nd:YAG laser (40 ps, 266 nm, 1 Hz), different nanostructures, from spikes to laser-induced periodic surface structures, were formed on 500 nm copper thin film and were analyzed with respect to the drop in dynamic reflectivity changes versus the number of laser shots.
Perspectives of using the 223-nm wavelength of the KrCl excimer laser for refractive surgery and for the treatment of some eye diseases

NASA Astrophysics Data System (ADS)

Bagayev, Sergei N.; Chernikh, Valery V.; Razhev, Alexander M.; Zhupikov, Andrey A.

2000-06-01

The new surgical UV ophthalmic laser system Medilex based on the KrCl (223 nm) excimer laser for refractive surgery was created. The comparative analysis of using the UV ophthalmic laser systems Medilex based on the ArF (193 nm) and the KrCl (223 nm) excimer lasers for the correction of refractive errors was performed. The system with the radiation wavelength of 223 nanometer of the KrCl excimer laser for refractive surgery was shown to have several medical and technical advantages over the system with the traditionally used radiation wavelength of 193 nanometer of the ArF excimer laser. In addition the use of the wavelength of 223 nanometer extends functional features of the system, allowing to make not only standard for this type systems surgical and therapeutic procedures but also to treat such ocular diseases as the glaucoma and herpetic keratities. For the UV ophthalmic laser systems Medilex three variations of the beam delivery system including special rotating masks and different beam homogenize systems were developed. All created beam delivery systems are able to make the correction of myopia, hyperopia, astigmatism and myopic or hyperopic astigmatism and may be used for therapeutic procedures. The results of the initial treatments of refractive error corrections using the UV ophthalmic laser systems Medilex for both photorefractive keratectomy (PRK) and LASIK procedures are presented.
Effect of scanning speed on continuous wave laser scribing of metal thin films: theory and experiment

NASA Astrophysics Data System (ADS)

Shahbazi, AmirHossein; Koohian, Ata; Madanipour, Khosro

2017-01-01

In this paper continuous wave laser scribing of the metal thin films have been investigated theoretically and experimentally. A formulation is presented based on parameters like beam power, spot size, scanning speed and fluence thresholds. The role of speed on the transient temperature and tracks width is studied numerically. By using two frameworks of pulsed laser ablation of thin films and laser printing on paper, the relation between ablation width and scanning speed has been derived. Furthermore, various speeds of the focused 450 nm continuous laser diode with an elliptical beam spot applied to a 290 nm copper thin film coated on glass, experimentally. The beam power was 150 mW after spatial filtering. By fitting the theoretical formulation to the experimental data, the threshold fluence and energy were obtained to be 13.2 J mm-2 and 414~μ J respectively. An anticipated theoretical parameter named equilibrium~border was verified experimentally. It shows that in the scribing of the 290 nm copper thin film, at a distance where the intensity reaches about 1/e of its maximum value, the absorbed fluence on the surface is equal to zero. Therefore the application of continuous laser in metal thin film ablation has different mechanism from pulsed laser drilling and beam scanning in printers.
Lateral scattered light used to study laser light propagation in turbid media phantoms

NASA Astrophysics Data System (ADS)

Valdes, Claudia; Solarte, Efrain

2010-02-01

Laser light propagation in soft tissues is important because of the growing biomedical applications of lasers and the need to optically characterize the biological media. Following previous developments of the group, we have developed low cost models, Phantoms, of soft tissue. The process was developed in a clean room to avoid the medium contamination. Each model was characterized by measuring the refractive index, and spectral reflectance and transmittance. To study the laser light propagation, each model was illuminated with a clean beam of laser light, using sources such as He-Ne (632nm) and DPSSL (473 nm). Laterally scattered light was imaged and these images were digitally processed. We analyzed the intensity distribution of the scattered radiation in order to obtain details of the beam evolution in the medium. Line profiles taken from the intensity distribution surface allow measuring the beam spread, and to find expressions for the longitudinal (along the beam incident direction) and transversal (across the beam incident direction) intensities distributions. From these behaviors, the radiation penetration depth and the total coefficient of extinction have been determined. The multiple scattering effects were remarkable, especially for the low wavelength laser beam.
Polarimetry diagnostic on OMEGA EP using a 10-ps, 263-nm probe beam.

PubMed

Davies, A; Haberberger, D; Boni, R; Ivancic, S; Brown, R; Froula, D H

2014-11-01

A polarimetry diagnostic was built and characterized for magnetic-field measurements in laser-plasma experiments on the OMEGA EP laser. This diagnostic was built into the existing 4ω (263-nm) probe system that employs a 10-ps laser pulse collected with an f/4 imaging system. The diagnostic measures the rotation of the probe beam's polarization. The polarimeter uses a Wollaston prism to split the probe beam into orthogonal polarization components. Spatially localized intensity variations between images indicate polarization rotation. Magnetic fields can be calculated by combining the polarimetry data with the measured plasma density profile obtained from angular filter refractometry.
Diode-pumped dual-wavelength Nd:LSO laser at 1059 and 1067 nm with nearly diffraction-limited beam quality.

PubMed

Huang, Xiaoxu; Lan, Jinglong; Lin, Zhi; Wang, Yi; Xu, Bin; Xu, Huiying; Cai, Zhiping; Xu, Xiaodong; Zhang, Jian; Xu, Jun

2016-04-10

We report a diode-pumped continuous-wave simultaneous dual-wavelength Nd:LSO laser at 1059 and 1067 nm. By employing a specially coated output coupler with relatively high transmissions at high-gain emission lines of 1075 and 1079 nm, the two low-gain emission lines, 1059 and 1067 nm, can be achieved, for the first time to our knowledge, with maximum output power of 1.27 W and slope efficiency of about 29.2%. The output power is only limited by the available pump power. Output beam quality is also measured to be about 1.19 and 1.21 of the beam propagation factors in the x and y directions, respectively.
Parallel multiplex laser feedback interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Song; Tan, Yidong; Zhang, Shulian, E-mail: zsl-dpi@mail.tsinghua.edu.cn

2013-12-15

We present a parallel multiplex laser feedback interferometer based on spatial multiplexing which avoids the signal crosstalk in the former feedback interferometer. The interferometer outputs two close parallel laser beams, whose frequencies are shifted by two acousto-optic modulators by 2Ω simultaneously. A static reference mirror is inserted into one of the optical paths as the reference optical path. The other beam impinges on the target as the measurement optical path. Phase variations of the two feedback laser beams are simultaneously measured through heterodyne demodulation with two different detectors. Their subtraction accurately reflects the target displacement. Under typical room conditions, experimentalmore » results show a resolution of 1.6 nm and accuracy of 7.8 nm within the range of 100 μm.« less
10 kHz ps 1342 nm laser generation by an electro-optically cavity-dumped mode-locked Nd:YVO4 laser

NASA Astrophysics Data System (ADS)

Chen, Ying; Liu, Ke; He, Li-jiao; Yang, Jing; Zong, Nan; Yang, Feng; Gao, Hong-wei; Liu, Zhao; Yuan, Lei; Lan, Ying-jie; Bo, Yong; Peng, Qin-jun; Cui, Da-fu; Xu, Zu-yan

2017-01-01

We have demonstrated an electro-optically cavity-dumped mode-locked (CDML) picosecond Nd:YVO4 laser at 1342 nm with 880 nm diode-laser direct pumping. At a repetition rate of 10 kHz, an average output power of 0.119 W was achieved, corresponding to a pulse energy of 11.9 μJ. Compared with the continuous wave mode-locking pulse energy of 17.5 nJ, the CDML pulse energy was 680 times higher. The pulse width was measured to be 33.4 ps, resulting in the peak power of 356 kW. Meanwhile, the beam quality was nearly diffraction limited with an average beam quality factor M2 of 1.29.
A miracle happening to a laser beam in a soap film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Startsev, Aleksandr V; Stoilov, Yurii Yu

2003-05-31

When a 10 {mu}W - 3 W laser beam (for example, at 632.8 nm) is focused into a usual soap film of thickness between 10 nm and 10 {mu}m from the side or through a defect on the film surface, the self-channeling of the beam propagating in the film is observed. The beam also exhibits self-branching into submicron filaments, the so-called whiskers of length several tens of centimetres. The results of experiments on the dynamics of behaviour of these whiskers in a soap film, their polariton nature, and possible applications are discussed. (letters)
Design and laser damage properties of a dichroic beam combiner coating for 22.5-deg incidence and S polarization with high transmission at 527 nm and high reflection at 1054 nm

DOE PAGES

Bellum, John C.; Field, Ella S.; Kletecka, Damon E.; ...

2016-10-12

We designed a dichroic beam combiner coating with 11 HfO 2/SiO 2 layer pairs and deposited it on a large substrate. It provides high transmission (HT) at 527 nm and high reflection (HR) at 1054 nm for a 22.5-deg angle of incidence (AOI), S polarization (Spol), and uses near half-wave layer thicknesses for HT at 527 nm, modified for HR at 1054 nm. The two options for the beam combiner each require that a high intensity beam be incident on the coating from within the substrate (from glass). We analyze the laser-induced damage threshold (LIDT) differences between the two optionsmore » in terms of the 527- and 1054-nm E-field behaviors for air → coating and glass → coating incidences. This indicates that LIDTs should be higher for air → coating than for glass → coating incidence. LIDT tests at the use AOI, Spol with ns pulses at 532 and 1064 nm confirm this, with glass → coating LIDTs about half that of air → coating LIDTs. Lastly, these results clearly indicate that the best beam combiner option is for the high intensity 527 and 1054 nm beams to be incident on the coating from air and glass, respectively.« less
Design and laser damage properties of a dichroic beam combiner coating for 22.5-deg incidence and S polarization with high transmission at 527 nm and high reflection at 1054 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bellum, John C.; Field, Ella S.; Kletecka, Damon E.

We designed a dichroic beam combiner coating with 11 HfO 2/SiO 2 layer pairs and deposited it on a large substrate. It provides high transmission (HT) at 527 nm and high reflection (HR) at 1054 nm for a 22.5-deg angle of incidence (AOI), S polarization (Spol), and uses near half-wave layer thicknesses for HT at 527 nm, modified for HR at 1054 nm. The two options for the beam combiner each require that a high intensity beam be incident on the coating from within the substrate (from glass). We analyze the laser-induced damage threshold (LIDT) differences between the two optionsmore » in terms of the 527- and 1054-nm E-field behaviors for air → coating and glass → coating incidences. This indicates that LIDTs should be higher for air → coating than for glass → coating incidence. LIDT tests at the use AOI, Spol with ns pulses at 532 and 1064 nm confirm this, with glass → coating LIDTs about half that of air → coating LIDTs. Lastly, these results clearly indicate that the best beam combiner option is for the high intensity 527 and 1054 nm beams to be incident on the coating from air and glass, respectively.« less

Study of laser preheating dependence on laser wavelength and intensity for MagLIF

NASA Astrophysics Data System (ADS)

Wei, M. S.; Harvey-Thompson, A. J.; Glinsky, M.; Nagayama, T.; Weis, M.; Geissel, M.; Peterson, K.; Fooks, J.; Krauland, C.; Giraldez, E.; Davies, J.; Campbell, E. M.; Bahr, R.; Edgell, D.; Stoeckl, C.; Glebov, V.; Emig, J.; Heeter, R.; Strozzi, D.

2017-10-01

The magnetized liner inertial fusion (MagLIF) scheme requires preheating underdense fuel to 100's eV temperature by a TW-scale long pulse laser via collisional absorption. To better understand how laser preheat scales with laser wavelength and intensity as well as to provide data for code validation, we have conducted a well-characterized experiment on OMEGA to directly compare laser propagation, energy deposition and laser plasma instabilities (LPI) using 2 ω (527 nm) and 3 ω (351 nm) lasers with intensity in the range of (1-5)x1014 Wcm-2. The laser beam (1 - 1.5 ns square pulse) enters the gas-filled plastic liner though a 2-µm thick polyimide window to heat an underdense Ar-doped deuterium gas with electron density of 5.5% of critical density. Laser propagation and plasma temperature are diagnosed by time-resolved 2D x-ray images and Ar emission spectroscopy, respectively. LPI is monitored by backscattering and hard x-ray diagnostics. The 2 ω beam propagation shows a noticeable larger lateral spread than the 3 ω beam, indicating laser spray due to filamentation. LPI is observed to increase with laser intensity and the 2 ω beam produces more hot electrons compared with the 3 ω beam under similar conditions. Results will be compared with radiation hydrodynamic simulations. Work supported by the U.S. DOE ARPA-E and NNSA.
Ridge Minimization of Ablated Morphologies on ITO Thin Films Using Squared Quasi-Flat Top Beam

PubMed Central

Jeon, Jin-Woo; Choi, Wonsuk; Shin, Young-Gwan; Ji, Suk-Young

2018-01-01

In this study, we explore the improvements in pattern quality that was obtained with a femtosecond laser with quasi-flat top beam profiles at the ablated edge of indium tin oxide (ITO) thin films for the patterning of optoelectronic devices. To ablate the ITO thin films, a femtosecond laser is used that has a wavelength and pulse duration of 1030 nm and 190 fs, respectively. The squared quasi-flat top beam is obtained from a circular Gaussian beam using slits with varying x-y axes. Then, the patterned ITO thin films are measured using both scanning electron and atomic force microscopes. In the case of the Gaussian beam, the ridge height and width are approximately 39 nm and 1.1 μm, respectively, whereas, when the quasi-flat top beam is used, the ridge height and width are approximately 7 nm and 0.25 μm, respectively. PMID:29601515
Compact laser transmitter delivering a long-range infrared beam aligned with a monitoring visible beam.

PubMed

Lee, Hong-Shik; Kim, Haeng-In; Lee, Sang-Shin

2012-06-10

A compact laser transmitter, which takes advantage of an optical subassembly module, was proposed and demonstrated, providing precisely aligned collinear IR and visible beams. The collimated IR beam acts as a long-range projectile for simulated combat, carrying an optical pulsed signal, whereas the visible beam plays the role of tracking the IR beam. The proposed laser transmitter utilizes IR (λ(1)=905 nm) and visible (λ(2)=660 nm) light sources, a fiber-optic collimator, and a beam combiner, which includes a wavelength division multiplexing (WDM) filter in conjunction with optical fiber. The device was built via the laser welding technique and then evaluated by investigating the characteristics of the generated light beams. The IR collimated beam produced had a Gaussian profile and a divergence angle of ~1.3 mrad, and the visible monitoring beam was appropriately collimated to be readily discernible in the vicinity of the transmitter. The two beams were highly aligned within an angle of 0.004 deg as anticipated. Finally, we performed a practical outdoor field test to assess the IR beam with the help of a receiver. An effective trajectory was observed ranging up to 660 m with an overall detectable beam width of ~60 cm.
Influence of CdS nanoparticles grain morphology on laser-induced absorption

NASA Astrophysics Data System (ADS)

Ebothé, Jean; Michel, Jean; Kityk, I. V.; Lakshminarayana, G.; Yanchuk, O. M.; Marchuk, O. V.

2018-06-01

Using external illumination of a 7 nanosecond (ns) doubled frequency Nd: YAG laser emitting at λ = 532 nm with frequency repetition 10 Hz it was established a possibility of significant changes of the absorption at the probing wavelength 1150 nm of continuous wave (cw) He-Ne laser for the CdS nanoparticles embedded into the PVA polymer matrix. The effect is observed only during the two beam laser coherent treatment and this effect is a consequence of interference of two coherent beams. It is shown a principal role of the grain morphology in the efficiency of the process, which is more important than the nanoparticle sizes. The photoinduced absorption is manifested in the space distribution of the probing laser beam. The principal role of the grain interfaces between the nanoparticle interfaces and the surrounding polymer matrix is shown. The effect is almost independent of the nanoparticle sizes. It may be used for laser operation by nanocomposites.
Compact lasing system at 13.5-nm to ground state of LiIII at 2Hz

NASA Astrophysics Data System (ADS)

Goltsov, A. Y.; Korobkin, D.; Nam, C. H.; Suckewer, Szymon

1997-11-01

The recent results of the demonstration of the lasing action at 13.5 nm in transition to ground state of LiIII at 2 Hz repetition rate using two lasers is being presented in this paper. A gain length of GL approximately equals 5.5 was measured in the 5 mm long, 0.3 mm diameter, LiF microcapillary using a 50 mJ, 250 fsec UV laser beam. The initial plasma was created in the microcapillary by a low power, relatively long pulse Nd/YAG laser. In order to shed light on observed unusually high efficiency of the ionization of the atoms in microcapillaries, the subpicosecond UV laser beam transmissions through the plasma in microcapillaries were measured. Strong dependence of the beam transmission on the delay time between inial plasma formation with the Nd/YAG laser and the sub-picosecond UV laser was recorded. The final part of the paper discusses some necessary conditions for an extension of the present results towards the shorter wavelength lasers with an emphasis on the presently conducted experiments at Princeton University for the generation gain at 4.8 nm in BV.
Electro-holographic display using a ZBLAN glass as the image space.

PubMed

Son, Jung-Young; Lee, Hyoung; Byeon, Jina; Zhao, Jiangbo; Ebendorff-Heidepriem, Heike

2017-04-01

An Er³⁺-doped ZBLAN glass is used to display a 360° viewable reconstructed image from a hologram on a DMD. The reconstructed image, when the hologram is illuminated by a 852 nm wavelength laser beam, is situated at the inside of the glass, and then a 1530 nm wavelength laser beam is crossed through the image to light it with an upconversion green light, which is viewable at all surrounding directions. This enables us to eliminate the limitation of the viewing zone angle imposed by the finite size of pixels in electro-holographic displays based on digital display chips/panels. The amount of the green light is much higher than that known previously. This is partly caused by the upconversion luminescence induced by 852 and 1530 nm laser beams.
80 A/cm2 electron beams from metal targets irradiated by KrCl and XeCl excimer lasers

NASA Astrophysics Data System (ADS)

Beloglazov, A.; Martino, M.; Nassisi, V.

1996-05-01

Due to the growing demand for high-current and long-duration electron-beam devices, laser electron sources were investigated in our laboratory. Experiments on electron-beam generation and propagation from aluminium and copper targets illuminated by XeCl (308 nm) and KrCl (222 nm) excimer lasers, were carried out under plasma ignition due to laser irradiation. This plasma supplied a spontaneous accelerating electric field of about 370 kV/m without an external accelerating voltage. By applying the modified one-dimensional Poisson equation, we computed the expected current and we also estimated the plasma concentration during the accelerating process. At 40 kV of accelerating voltage, an output current pulse of about 80 A/cm2 was detected from an Al target irradiated by the shorter wavelength laser.
Red and infrared gas laser beam for therapy

NASA Astrophysics Data System (ADS)

Pascu, Mihail-Lucian; Ristici, Marin; Ristici, E.; Tivarus, Madalina-Elena

2000-06-01

For the low power laser therapy, the experiments show that better results are obtained when the laser beam is an overlapping of two radiations: one in the visible region of the spectrum and the other in IR region. Also, some experiments show that for good results in biostimulation it is important to have a high coherence length of laser beam; this is not the case of the laser diodes The He-Ne laser has the best coherence, being able to generate laser radiations in visible and IR. It has tow strong laser lines: 633 nm and 1.15 micrometers . Although their gains are about the same, the available power of the red radiation is 3-4 times higher because of its larger width, when they oscillate separately. Using special dichroic mirrors for simultaneous reflection of the both liens, the laser beam will consist of the two radiations, each of them having good coherence . A 420 mm active length, 1.8 mm inner diameter He-Ne laser tube and a special designed resonator has been developed. The mirrors reflect both radiations as follows: one reflects 99.9 percent and the other, the output mirror, reflects 98 percent. There is a competition between them because these lines have a common lower level. The output power of the laser beam as 6 mW for 633 nm and 4 mW for 1.15 micrometers , respectively.
Plasma Profile Measurements for Laser Fusion Research with the Nike KrF Laser

NASA Astrophysics Data System (ADS)

Oh, Jaechul; Weaver, J. L.; Serlin, V.; Obenschain, S. P.

2015-11-01

The grid image refractometer of the Nike laser facility (Nike-GIR) has demonstrated the capability of simultaneously measuring electron density (ne) and temperature (Te) profiles of coronal plasma. For laser plasma instability (LPI) research, the first Nike-GIR experiment successfully measured the plasma profiles in density regions up to ne ~ 4 ×1021 cm-3 (22% of the critical density for 248 nm light of Nike) using an ultraviolet probe laser (λp = 263 nm). The probe laser has been recently replaced with a shorter wavelength laser (λp = 213 nm, a 5th harmonic of the Nd:YAG laser) to diagnose a higher density region. The Nike-GIR system is being further extended to measure plasma profiles in the on-going experiment using 135°-separated Nike beam arrays for the cross-beam energy transfer (CBET) studies. We present an overview of the extended Nike-GIR arrangements and a new numerical algorithm to extract self-consistant plasma profiles with the measured quantities. Work supported by DoE/NNSA.
Demonstration of miniaturized 20mW CW 280nm and 266nm solid-state UV laser sources

NASA Astrophysics Data System (ADS)

Landru, Nicolas; Georges, Thierry; Beaurepaire, Julien; Le Guen, Bruno; Le Bail, Guy

2015-02-01

Visible 561 nm and 532 nm laser emissions from 14-mm long DPSS monolithic cavities are frequency converted to deep UV 280 nm and 266 nm in 16-mm long monolithic external cavities. Wavelength conversion is fully insensitive to mechanical vibrations and the whole UV laser sources fit in a miniaturized housing. More than 20 mW deep UV laser emission is demonstrated with high power stability, low noise and good beam quality. Aging tests are in progress but long lifetimes are expected thanks to the cavity design. Protein detection and deep UV resonant Raman spectroscopy are applications that could benefit from these laser sources.
2000W high beam quality diode laser for direct materials processing

NASA Astrophysics Data System (ADS)

Qin, Wen-bin; Liu, You-qiang; Cao, Yin-hua; Gao, Jing; Pan, Fei; Wang, Zhi-yong

2011-11-01

This article describes high beam quality and kilowatt-class diode laser system for direct materials processing, using optical design software ZEMAX® to simulate the diode laser optical path, including the beam shaping, collimation, coupling, focus, etc.. In the experiment, the diode laser stack of 808nm and the diode laser stack of 915nm were used for the wavelength coupling, which were built vertical stacks up to 16 bars. The threshold current of the stack is 6.4A, the operating current is 85A and the output power is 1280W. Through experiments, after collimating the diode laser beam with micro-lenses, the fast axis BPP of the stack is less than 60mm.mrad, and the slow-axis BPP of the stack is less than 75mm.mrad. After shaping the laser beam and improving the beam quality, the fast axis BPP of the stack is still 60mm.mrad, and the slow-axis BPP of the stack is less than 19mm.mrad. After wavelength coupling and focusing, ultimately the power of 2150W was obtained, focal spot size of 1.5mm * 1.2mm with focal length 300mm. The laser power density is 1.2×105W/cm2, and that can be used for metal remelting, alloying, cladding and welding. The total optical coupling conversion efficiency is 84%, and the total electrical - optical conversion efficiency is 50%.
Power balance on a multibeam laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sampat, Sid; Kelly, John H.; Kosc, Tanya Z.

Inertial confinement fusion (ICF) cryogenic experiments on the 60-beam OMEGA laser have strict requirements for the laser energy delivered on target to be power balanced in order to maximize target-irradiation uniformity. For OMEGA, this quantity (power balance) is inferred from measurements of the time-integrated energy and time-resolved, spatially integrated temporal profile of each of the 60 beams at the output of the laser. The work presented here proposes a general definition of power balance as measured at the laser output and discusses the conditions that are fundamental to achieving laser power balance. Power balance necessitates equal gain across all stagesmore » of amplification, equal net losses across each amplifier stage, equal frequency conversion (from 1053 nm to 351 nm) of all 60 beams, and equal beam path lengths (beam timing). Typical OMEGA ICF laser pulse shapes consist of one or more short (100-ps) “pickets” followed by a shaped “drive” pulse of 1 to 2 ns. For these experiments, power balance is assessed for the pickets and the drive independently, with the ultimate goal of achieving root-mean-square (rms) imbalance across all 60 beams of less than 2% rms on both. Our work presents a comprehensive summary of laser shot campaigns conducted to significantly improve laser power balance from typical rms values of 4.7% and 5.2%, respectively, to the 3% level for both features along with a discussion of future work required to further reduce the rms power imbalance of the laser system.« less
Power balance on a multibeam laser

NASA Astrophysics Data System (ADS)

Sampat, S.; Kelly, J. H.; Kosc, T. Z.; Rigatti, A. L.; Kwiatkowski, J.; Donaldson, W. R.; Romanofsky, M. H.; Waxer, L. J.; Dean, R.; Moshier, R.

2018-02-01

Inertial confinement fusion (ICF) cryogenic experiments on the 60-beam OMEGA laser have strict requirements for the laser energy delivered on target to be power balanced in order to maximize target-irradiation uniformity. For OMEGA, this quantity (power balance) is inferred from measurements of the time-integrated energy and time-resolved, spatially integrated temporal profile of each of the 60 beams at the output of the laser. The work presented here proposes a general definition of power balance as measured at the laser output and discusses the conditions that are fundamental to achieving laser power balance. Power balance necessitates equal gain across all stages of amplification, equal net losses across each amplifier stage, equal frequency conversion (from 1053 nm to 351 nm) of all 60 beams, and equal beam path lengths (beam timing). Typical OMEGA ICF laser pulse shapes consist of one or more short (100-ps) "pickets" followed by a shaped "drive" pulse of 1 to 2 ns. For these experiments, power balance is assessed for the pickets and the drive independently, with the ultimate goal of achieving root-mean-square (rms) imbalance across all 60 beams of less than 2% rms on both. This work presents a comprehensive summary of laser shot campaigns conducted to significantly improve laser power balance from typical rms values of 4.7% and 5.2%, respectively, to the 3% level for both features along with a discussion of future work required to further reduce the rms power imbalance of the laser system.
Power balance on a multibeam laser

DOE PAGES

Sampat, Sid; Kelly, John H.; Kosc, Tanya Z.; ...

2018-02-15

Inertial confinement fusion (ICF) cryogenic experiments on the 60-beam OMEGA laser have strict requirements for the laser energy delivered on target to be power balanced in order to maximize target-irradiation uniformity. For OMEGA, this quantity (power balance) is inferred from measurements of the time-integrated energy and time-resolved, spatially integrated temporal profile of each of the 60 beams at the output of the laser. The work presented here proposes a general definition of power balance as measured at the laser output and discusses the conditions that are fundamental to achieving laser power balance. Power balance necessitates equal gain across all stagesmore » of amplification, equal net losses across each amplifier stage, equal frequency conversion (from 1053 nm to 351 nm) of all 60 beams, and equal beam path lengths (beam timing). Typical OMEGA ICF laser pulse shapes consist of one or more short (100-ps) “pickets” followed by a shaped “drive” pulse of 1 to 2 ns. For these experiments, power balance is assessed for the pickets and the drive independently, with the ultimate goal of achieving root-mean-square (rms) imbalance across all 60 beams of less than 2% rms on both. Our work presents a comprehensive summary of laser shot campaigns conducted to significantly improve laser power balance from typical rms values of 4.7% and 5.2%, respectively, to the 3% level for both features along with a discussion of future work required to further reduce the rms power imbalance of the laser system.« less
Hydroxyl Tagging Velocimetry in a Mach 2 Flow With a Wall Cavity (Postprint)

DTIC Science & Technology

2005-01-01

tagging velocimetry (HTV) measurements of velocity were made in a Mach 2 flow with a wall cavity. In the HTV method, ArF excimer laser (193 nm) beams...is tracked by planar laser -induced fluorescence. The grid motion over a fixed time delay yields about 50 velocity vectors of the two-dimensional flow...Mach 2 flow with a wall cavity. In the HTV method, ArF excimer laser (193 nm) beams pass through a humid gas and dissociate H2O into H + OH to form
Hydroxyl Tagging Velocimetry in Cavity-Piloted Mach 2 Combustor (Postprint)

DTIC Science & Technology

2006-01-01

combustor with a wall cavity flameholder. In the HTV method, ArF excimer laser (193 nm) beams pass through a humid gas flow and dissociate H2O into H...grid of OH tracked by planar laser -induced fluorescence to yield about 120 velocity vectors of the two-dimensional flow over a fixed time delay...with a wall cavity flameholder. In the HTV method, ArF excimer laser (193 nm) beams pass through a humid gas flow and dissociate H2O into H + OH to
Building achromatic refractive beam shapers

NASA Astrophysics Data System (ADS)

Laskin, Alexander; Shealy, David

2014-10-01

Achromatic beam shapers can provide beam shaping in a certain spectral band and are very important for various laser techniques, such as, applications based on ultra-short pulse lasers with pulse width <100 fs, confocal microscopy, multicolour holography, life sciences fluorescence techniques, where several lasers in spectrum 405-650 nm are used simultaneously, for example 405-650 nm. Conditions of energy re-distribution and zero wave aberration are strictly fulfilled in ordinary plano-aspheric lens pair beam shapers for a definite wavelength only. Hence, these beam shapers work efficiently in relatively narrow, few nm spectrum. To provide acceptable beam quality for refractive beam shaping over a wide spectrum, an achromatizing design condition should be added. Consequently, the typical beam shaper design contains more than two-lenses, to avoid any damaging and other undesirable effects the lenses of beam shaper should be air-spaced. We suggest a two-step method of designing the beam shaper: 1) achromatizing of each plano-aspheric lens using a buried achromatizing surface ("chromatic radius"), then each beam shaper component presents a cemented doublet lens, 2) "splitting" the cemented lenses and realizing air-spaced lens design using optical systems design software. This method allows for using an achromatic design principle during the first step of the design, and then, refining the design by using optimization software. We shall present examples of this design procedure for an achromatic Keplerian beam shaper and for the design of an achromatic Galilean type of beam shaper. Experimental results of operation of refractive beam shapers will be presented as well.
Wavelength adjustability of frequency conversion light of Yb-doped fiber laser based on FBGs

NASA Astrophysics Data System (ADS)

Dobashi, Kazuma; Tomihari, Yasuhiro; Imai, Koichi; Hirohashi, Junji; Makio, Satoshi

2018-02-01

We focused on wavelength conversion of simple and compact CW Yb-Doped fiber laser based on FBGs with wavelength adjustable function. By controlling temperatures of FBGs in fiber laser, it was possible to tune oscillated wavelength from 1064.101 nm to 1064.414 nm with more than 20 W in CW operation mode. Based on this fundamental light, frequency converted light (SHG and THG) were generated by utilizing two PP:Mg-SLT devises. We obtained more than 3 W of SHG light with tuning range of 150 pm and more than 35 mW of THG with tuning range of 100 pm. By selecting FBG grating and QPM grating properly, we can realize adjustable wavelength laser with the same scheme from 1040 nm to 1090 nm and their SHG/THG. With this combination of FBG based fiber laser and QPM devices, it is possible to tune the wavelength just by temperature tuning without any changes of beam shape and beam pointing.
Morphologies of femtosecond laser ablation of ITO thin films using gaussian or quasi-flat top beams for OLED repair

NASA Astrophysics Data System (ADS)

Kim, Hoon-Young; Choi, Won-Suk; Ji, Suk-Young; Shin, Young-Gwan; Jeon, Jin-Woo; Ahn, Sanghoon; Cho, Sung-Hak

2018-02-01

This study compares the ablation morphologies obtained with a femtosecond laser of both Gaussian and quasi-flat top beam profiles when applied to indium tin oxide (ITO) thin films for the purpose of OLED repair. A femtosecond laser system with a wavelength of 1030 nm and pulse duration of 190 fs is used to pattern an ITO thin film. The laser fluence is optimized for patterning at 1.38 J/cm2. The patterned ITO thin film is then evaluated through both optical microscope and atomic force microscope. Ablations with a square quasi-flat top beam are demonstrated using slits with varying x- y axes. With the Gaussian beam, the pattern width of the ablated area is shown to range from 9.17 to 9.99 μm when the number of irradiation pulse increases from one to six. In contrast, when slit control is used to obtain a quasi-flat top beam, the ablated pattern width remains constant at 10 μm, despite the increase in the number of pulse. The improved surface roughness is correlated with the quasi-flat top beam through measured Ra values. Furthermore, when using the Gaussian beam, the minimum resolution of the controllable ablation depth on the ITO thin film is found to be 60 nm. In contrast, when the quasi-flat top beam is used, the minimum ablation depth decreases to 40 nm.
Exposure of Chlorpromazine to 266 nm Laser Beam Generates New Species with Antibacterial Properties: Contributions to Development of a New Process for Drug Discovery

PubMed Central

Pascu, Mihail Lucian; Danko, Balazs; Martins, Ana; Jedlinszki, Nikoletta; Alexandru, Tatiana; Nastasa, Viorel; Boni, Mihai; Militaru, Andra; Andrei, Ionut Relu; Staicu, Angela; Hunyadi, Attila; Fanning, Seamus; Amaral, Leonard

2013-01-01

Introduction Phenothiazines when exposed to white light or to UV radiation undergo a variety of reactions that result in degradation of parental compound and formation of new species. This process is slow and may be sped up with exposure to high energy light such as that produced by a laser. Methods Varying concentrations of Chlorpromazine Hydrochloride (CPZ) (2–20 mg/mL in distilled water) were exposed to 266 nm laser beam (time intervals: 1–24 hrs). At distinct intervals the irradiation products were evaluated by spectrophotometry between 200–1500 nm, Thin Layer Chromatography, High Pressure Liquid Chromatography (HPLC) - Diode Array Detection, HPLC tandem mass spectrometry, and for activity against the CPZ sensitive test organism Staphylococcus aureus ATCC 25923. Results CPZ exposure to 266 nm laser beam of given energy levels yielded species, whose number increased with duration of exposure. Although the major species produced were Promazine (PZ), hydroxypromazine or PZ sulfoxide, and CPZ sulfoxide, over 200 compounds were generated with exposure of 20 mg/mL of CPZ for 24 hrs. Evaluation of the irradiation products indicated that the bioactivity against the test organism increased despite the total disappearance of CPZ, that is due, most probably, to one or more new species that remain yet unidentified. Conclusions Exposure of CPZ to a high energy (6.5 mJ) 266 nm laser beam yields rapidly a large number of new and stable species. For biological grade phenothiazines (in other words knowing the impurities in the samples: solvent and solute) this process may be reproducible because one can control within reasonably low experimental errors: the concentration of the parent compound, the laser beam wavelength and average energy, as well as the duration of the exposure time. Because the process is “clean” and rapid, it may offer advantages over the pyrogenically based methods for the production of derivatives. PMID:23405212

Fabrication and characterization of microcavity lasers in rhodamine B doped SU8 using high energy proton beam

NASA Astrophysics Data System (ADS)

Venugopal Rao, S.; Bettiol, A. A.; Vishnubhatla, K. C.; Bhaktha, S. N. B.; Narayana Rao, D.; Watt, F.

2007-03-01

The authors present their results on the characterization of individual dye-doped microcavity polymer lasers fabricated using a high energy proton beam. The lasers were fabricated in rhodamine B doped SU8 resist with a single exposure step followed by chemical processing. The resulting trapezoidal shaped cavities had dimensions of ˜250×250μm2. Physical characterization of these structures was performed using a scanning electron microscope while the optical characterization was carried out by recording the emission subsequent to pumping the lasers with 532nm, 6 nanosecond pulses. The authors observed intense, narrow emission near 624nm with the best emission linewidth full width at half maximum of ˜9nm and a threshold ˜150μJ/mm2.
A 25kW fiber-coupled diode laser for pumping applications

NASA Astrophysics Data System (ADS)

Malchus, Joerg; Krause, Volker; Koesters, Arnd; Matthews, David G.

2014-03-01

In this paper we report the development of a new fiber-coupled diode laser for pumping applications capable of generating 25 kW with four wavelengths. The delivery fiber has 2.0 mm core diameter and 0.22 NA resulting in a Beam Parameter Product (BPP) of 220 mm mrad. To achieve the specifications mentioned above a novel beam transformation technique has been developed combining two high power laser stacks in one common module. After fast axis collimation and beam reformatting a beam with a BPP of 200 mm mrad x 40 mm mrad in the slow and fast-axis is generated. Based on this architecture a customer-specific pump laser with 25 kW optical output power has been developed, in which two modules are polarization multiplexed for each wavelength (980nm, 1020nm, 1040m and 1060nm). After slow-axis collimation these wavelengths are combined using dense wavelength coupling before focusing onto the fiber endface. This new laser is based on a turn-key platform, allowing straight-forward integration into any pump application. The complete system has a footprint of less than 1.4m² and a height of less than 1.8m. The laser diodes are water cooled, achieve a wall-plug efficiency of up to 60%, and have a proven lifetime of <30,000 hours. The new beam transformation techniques open up prospects for the development of pump sources with more than 100kW of optical output power.
Study of beam aberrations in a germanium XXIII XUV laser amplifier

NASA Astrophysics Data System (ADS)

Smith, C. G.; Key, M. H.; Cairns, G.; Dwivedi, L.; Krishnan, J.; Lewis, C. L. S.; MacPhee, A. G.; Neely, D.; Ramsden, S. A.; Tallents, G.

1996-02-01

A beam of amplified spontaneous emission at {23.2}/{23.6}nm from a GeXXIII XUV laser has been injected into a separate amplifier plasma and the astigmatic aberrations introduced by plasma density gradients in the amplifier have been estimated from analysis of images of the amplified beam.
Inhibited-coupling HC-PCF based beam-delivery-system for high power green industrial lasers

NASA Astrophysics Data System (ADS)

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).
Laser Induced Breakdown Spectroscopy Based on Single Beam Splitting and Geometric Configuration for Effective Signal Enhancement

PubMed Central

Yang, Guang; Lin, Qingyu; Ding, Yu; Tian, Di; Duan, Yixiang

2015-01-01

A new laser induced breakdown spectroscopy (LIBS) based on single-beam-splitting (SBS) and proper optical geometric configuration has been initially explored in this work for effective signal enhancement. In order to improve the interaction efficiency of laser energy with the ablated material, a laser beam operated in pulse mode was divided into two streams to ablate/excite the target sample in different directions instead of the conventional one beam excitation in single pulse LIBS (SP-LIBS). In spatial configuration, the laser beam geometry plays an important role in the emission signal enhancement. Thus, an adjustable geometric configuration with variable incident angle between the two splitted laser beams was constructed for achieving maximum signal enhancement. With the optimized angles of 60° and 70° for Al and Cu atomic emission lines at 396.15 nm and 324.75 nm respectively, about 5.6- and 4.8-folds signal enhancements were achieved for aluminum alloy and copper alloy samples compared to SP-LIBS. Furthermore, the temporal analysis, in which the intensity of atomic lines in SP-LIBS decayed at least ten times faster than the SBS-LIBS, proved that the energy coupling efficiency of SBS-LIBS was significantly higher than that of SP-LIBS. PMID:25557721
Photonic switching based on the photoinduced birefringence in bacteriorhodopsin films

NASA Astrophysics Data System (ADS)

Huang, Yuhua; Wu, Shin-Tson; Zhao, Youyuan

2004-03-01

Photoinduced birefringence in bacteriorhodopsin films was investigated using pump-probe method and its application for photonic switching explored. A diode-pumped second-harmonic YAG laser was used as a pumping beam and a diode laser at λ=660 nm was used as a probing beam. The pump and probe beams overlap at the sample. Without the pumping beam, the probing light cannot transmit the analyzer to the detector. However, due to the photoinduced anisotropy, a portion of the probing light is detected when the pumping beam is present. Since λ=660 nm is far from the absorption peak (˜570 nm) of the ground state, the photoinduced birefringence predominates. Using the intensity-dependent photoinduced birefringence in a bacteriorhodopsin film, we have demonstrated a photonic switch with ˜1000:1 contrast ratio, ˜0.6 s rise time and ˜1.5 s decay time.
Dual-wavelength vortex beam with high stability in a diode-pumped Yb:CaGdAlO4 laser

NASA Astrophysics Data System (ADS)

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.
Ultra-compact laser beam steering device using holographically formed two dimensional photonic crystal.

PubMed

Dou, Xinyuan; Chen, Xiaonan; Chen, Maggie Yihong; Wang, Alan Xiaolong; Jiang, Wei; Chen, Ray T

2010-03-01

In this paper, we report the theoretical study of polymer-based photonic crystals for laser beam steering which is based on the superprism effect as well as the experiment fabrication of the two dimensional photonic crystals for the laser beam steering. Superprism effect, the principle for beam steering, was separately studied in details through EFC (Equifrequency Contour) analysis. Polymer based photonic crystals were fabricated through double exposure holographic interference method using SU8-2007. The experiment results showed a beam steering angle of 10 degree for 30 nm wavelength variation.
Free-space wavelength-multiplexed optical scanner demonstration.

PubMed

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.
High repetition rate ultrashort laser cuts a path through fog

NASA Astrophysics Data System (ADS)

de la Cruz, Lorena; Schubert, Elise; Mongin, Denis; Klingebiel, Sandro; Schultze, Marcel; Metzger, Thomas; Michel, Knut; Kasparian, Jérôme; Wolf, Jean-Pierre

2016-12-01

We experimentally demonstrate that the transmission of a 1030 nm, 1.3 ps laser beam of 100 mJ energy through fog increases when its repetition rate increases to the kHz range. Due to the efficient energy deposition by the laser filaments in the air, a shockwave ejects the fog droplets from a substantial volume of the beam, at a moderate energy cost. This process opens prospects for applications requiring the transmission of laser beams through fogs and clouds.
Laser beam alignment and profilometry using diagnostic fluorescent safety mirrors

NASA Astrophysics Data System (ADS)

Lizotte, Todd E.

2011-03-01

There are a wide range of laser beam delivery systems in use for various purposes; including industrial and medical applications. Virtually all such beam delivery systems for practical purposes employ optical systems comprised of mirrors and lenses to shape, focus and guide the laser beam down to the material being processed. The goal of the laser beam delivery is to set the optimum parameters and to "fold" the beam path to reduce the mechanical length of the optical system, thereby allowing a physically compact system. In many cases, even a compact system can incorporate upwards of six mirrors and a comparable number of lenses all needing alignment so they are collinear. One of the major requirements for use of such systems in industry is a method of safe alignment. The alignment process requires that the aligner determine where the beam strikes each element. The aligner should also preferably be able to determine the shape or pattern of the laser beam at that point and its relative power. These alignments are further compounded in that the laser beams generated are not visible to the unaided human eye. Such beams are also often of relatively high power levels, and are thereby a significant hazard to the eyes of the aligner. Obvious an invisible beam makes it nearly impossible to align laser system without some form of optical assistance. The predominant method of visually aligning the laser beam delivery is the use of thermal paper, paper cards or fluorescing card material. The use of paper products which have limited power handling capability or coated plastics can produce significant debris and contaminants within the beam line that ultimately damage the optics. The use of the cards can also create significant laser light scatter jeopardizing the safety of the person aligning the system. This paper covers a new safety mirror design for use with at various UV and Near IR wavelengths (193 nm to 1064 nm) within laser beam delivery systems and how its use can provide benefits covering eye safety, precise alignment and beam diagnostics.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Shlapakovski, A.; Gorev, S.; Krasik, Ya. E.

The influence of laser beam parameters on the output pulses of a resonant microwave compressor with a laser-triggered plasma switch was investigated. The S-band compressor, consisting of a rectangular waveguide-based cavity and H-plane waveguide tee with a shorted side arm, was filled with pressurized dry air and pumped by 1.8-μs-long microwave pulses of up to 450 kW power. A Nd:YAG laser was used to ignite the gas discharge in the tee side arm for output pulse extraction. The laser beam (at 213 nm or 532 nm) was directed along the RF electric field lines. It was found that the compressor operated most effectivelymore » when the laser beam was focused at the center of the switch waveguide cross-section. In this case, the power extraction efficiency reached ∼47% at an output power of ∼14 MW, while when the laser beam was not focused the maximal extraction efficiency was only ∼20% at ∼6 MW output power. Focusing the laser beam resulted also in a dramatic decrease (down to <1 ns) in the delay of the output pulses' appearance with respect to the time of the beam's entrance into the switch, and the jitter of the output pulses' appearance was minimized. In addition, the quality of the output pulses' waveform was significantly improved.« less
Parametric Raman crystalline anti-Stokes laser at 503 nm with collinear beam interaction at tangential phase matching

NASA Astrophysics Data System (ADS)

Smetanin, S. N.; Jelínek, M.; Kubeček, V.

2017-07-01

Stimulated-Raman-scattering in crystals can be used for the single-pass frequency-conversion to the Stokes-shifted wavelengths. The anti-Stokes shift can also be achieved but the phase-matching condition has to be fulfilled because of the parametric four-wave mixing process. To widen the angular-tolerance of four-wave mixing and to obtain high-conversion-efficiency into the anti-Stokes, we developed a new scheme of the parametric Raman anti-Stokes laser at 503 nm with phase-matched collinear beam interaction of orthogonally-polarized Raman components in calcite oriented at the phase-matched angle under 532 nm 20 ps laser excitation. The excitation laser beam was split into two orthogonally-polarized components entering the calcite at the certain incidence angles to fulfill the nearly collinear phase-matching and also to compensate walk-off of extraordinary waves for collinear beam interaction. The phase matching of parametric Raman interaction is tangential and insensitive to the angular mismatch if the Poynting vectors of the biharmonic pump and parametrically generated (anti-Stokes) waves are collinear. For the first time it allows to achieve experimentally the highest conversion efficiency into the anti-Stokes wave (503 nm) up to 30% from the probe wave and up to 3.5% from both pump and probe waves in the single-pass picosecond parametric calcite Raman laser. The highest anti-Stokes pulse energy was 1.4 μJ.
Safe Laser Beam Propagation for Interplanetary Links

NASA Technical Reports Server (NTRS)

Wilson, Keith E.

2011-01-01

Ground-to-space laser uplinks to Earth–orbiting satellites and deep space probes serve both as a beacon and an uplink command channel for deep space probes and Earth-orbiting satellites. An acquisition and tracking point design to support a high bandwidth downlink from a 20-cm optical terminal on an orbiting Mars spacecraft typically calls for 2.5 kW of 1030-nm uplink optical power in 40 micro-radians divergent beams.2 The NOHD (nominal ocular hazard distance) of the 1030nm uplink is in excess of 2E5 km, approximately half the distance to the moon. Recognizing the possible threat of high power laser uplinks to the flying public and to sensitive Earth-orbiting satellites, JPL developed a three-tiered system at its Optical Communications Telescope Laboratory (OCTL) to ensure safe laser beam propagation through navigational and near-Earth space.
Direct periodic patterning of GaN-based light-emitting diodes by three-beam interference laser ablation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Jeomoh; Ji, Mi-Hee; Detchprohm, Theeradetch

2014-04-07

We report on the direct patterning of two-dimensional periodic structures in GaN-based light-emitting diodes (LEDs) through laser interference ablation for the fast and reliable fabrication of periodic micro- and nano-structures aimed at enhancing light output. Holes arranged in a two-dimensional hexagonal lattice array having an opening size of 500 nm, depth of 50 nm, and a periodicity of 1 μm were directly formed by three-beam laser interference without photolithography or electron-beam lithography processes. The laser-patterned LEDs exhibit an enhancement in light output power of 20% compared to conventional LEDs having a flat top surface without degradation of electrical and optical properties of themore » top p-GaN layer and the active region, respectively.« less
Design and development of 24 times high-power laser beam expander

NASA Astrophysics Data System (ADS)

Lin, Zhao-heng; Gong, Xiu-ming; Wu, Shi-bin; Tan, Yi; Jing, Hong-wei; Wei, Zhong-wei

2013-09-01

As currently, laser calibration, laser radar, laser ranging and the relative field raised up the demand for high magnification laser beam expander. This article intends to introduce a high-energy laser beam expander research and design, large- diameter, wide-band, high-magnification and small obscuration ratio are the main features. By using Cassegrain reflective optical system, this laser beam expander achieves 24 times beam expand, and outgoing effective limiting aperture is Φ600 mm, band scope between 0.45μm to 5μm, single-pulse laser damage threshold greater than 1J/cm2, continuous-wave laser damage threshold greater than 200W/cm2 and obscuration ratio 1:10. Primary mirror underside support uses 9 points float supporting, lateral support mainly depends on mercury belt support and assists by mandrel ball head positioning support. An analyzing base on finite element analysis software ANSYS, and primary mirror deformation status analysis with debug mode and operativemode, when inputs four groups of Angle 170°, 180°, 210° and 240° , mercury belt under each group of angle load-bearing is 65%, 75% , 85% and 100% respectively, totally 16 workingcondition analyze results. At last, the best way to support primary mirror is finalized. Through design of secondary mirror to achieve a five-dimensional precision fine-tune. By assembling and debugging laser beam expander, Zygo interferometer detection system proof image quality (RMS) is 0.043λ (λ=632.8nm), stability (RMS) is 0.007λ (λ=632.8nm), and effective transmission hit 94%, meets the requirements of practical application completely.
Designing Light Beam Transmittance Measuring Tool Using a Laser Pointer

NASA Astrophysics Data System (ADS)

Nuroso, H.; Kurniawan, W.; Marwoto, P.

2016-08-01

A simple instrument used for measuring light beam transmittance percentage made of window film has been developed. The instrument uses a laser pointer of 405 nm and 650 nm ±10% as a light source. Its accuracy approaches 80%. Transmittance data was found by comparing the light beam before and after passing the window film. The light intensity measuring unit was deleted by splitting the light source into two beams through a beam splitter. The light beam was changed into resistance by a NORP12 LDR sensor designed at a circuit of voltage divider rule of Khirchoff's laws. This conversion system will produce light beam intensity received by the sensor to become an equal voltage. This voltage will, then, be presented on the computer screen in the form of a real time graph via a 2.0 USB data transfer.
1.9 W continuous-wave single transverse mode emission from 1060 nm edge-emitting lasers with vertically extended lasing area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miah, M. J., E-mail: jarez.miah@tu-berlin.de; Posilovic, K.; Kalosha, V. P.

2014-10-13

High-brightness edge-emitting semiconductor lasers having a vertically extended waveguide structure emitting in the 1060 nm range are investigated. Ridge waveguide (RW) lasers with 9 μm stripe width and 2.64 mm cavity length yield highest to date single transverse mode output power for RW lasers in the 1060 nm range. The lasers provide 1.9 W single transverse mode optical power under continuous-wave (cw) operation with narrow beam divergences of 9° in lateral and 14° (full width at half maximum) in vertical direction. The beam quality factor M{sup 2} is less than 1.9 up to 1.9 W optical power. A maximum brightness of 72 MWcm{sup −2}sr{supmore » −1} is obtained. 100 μm wide and 3 mm long unpassivated broad area lasers provide more than 9 W optical power in cw operation.« less
Composite Yb:YAG/SiC-prism thin disk laser.

PubMed

Newburgh, G A; Michael, A; Dubinskii, M

2010-08-02

We report the first demonstration of a Yb:YAG thin disk laser wherein the gain medium is intracavity face-cooled through bonding to an optical quality SiC prism. Due to the particular design of the composite bonded Yb:YAG/SiC-prism gain element, the laser beam impinges on all refractive index interfaces inside the laser cavity at Brewster's angles. The laser beam undergoes total internal reflection (TIR) at the bottom of the Yb(10%):YAG thin disk layer in a V-bounce cavity configuration. Through the use of TIR and Brewster's angles, no optical coatings, either anti-reflective (AR) or highly reflective (HR), are required inside the laser cavity. In this first demonstration, the 936.5-nm diode pumped laser performed with approximately 38% slope efficiency at 12 W of quasi-CW (Q-CW) output power at 1030 nm with a beam quality measured at M(2) = 1.5. This demonstration opens up a viable path toward novel thin disk laser designs with efficient double-sided room-temperature heatsinking via materials with the thermal conductivity of copper on both sides of the disk.
1047 nm laser diode master oscillator Nd:YLF power amplifier laser system

NASA Technical Reports Server (NTRS)

Yu, A. W.; Krainak, M. A.; Unger, G. L.

1993-01-01

A master oscillator power amplifier (MOPA) laser transmitter system at 1047 nm wavelength using a semiconductor laser diode and a diode pumped solid state (Nd:YLF) laser (DPSSL) amplifier is described. A small signal gain of 23 dB, a near diffraction limited beam, 1 Gbit/s modulation rates and greater than 0.6 W average power are achieved. This MOPA laser has the advantage of amplifying the modulation signal from the laser diode master oscillator (MO) with no signal degradation.

A six-color four-laser mobile platform for multi-spectral fluorescence imaging endoscopy

NASA Astrophysics Data System (ADS)

Black, John F.; Tate, Tyler; Keenan, Molly; Swan, Elizabeth; Utzinger, Urs; Barton, Jennifer

2015-03-01

The properties of multi-spectral fluorescence imaging using deep-UV-illumination have recently been explored using a fiber-coupled thermal source at 280 nm. The resulting images show a remarkable level of contrast thought to result from the signal being overwhelmingly generated in the uppermost few cell layers of tissue, making this approach valuable for the study of diseases that originate in the endothelial tissues of the body. With a view to extending the technique with new wavelengths, and improving beam quality for efficient small core fiber coupling we have developed a mobile self-contained tunable solid-state laser source of deep UV light. An alexandrite laser, lasing at around 750 nm is frequency doubled to produce 375 nm and then tripled to produce 250 nm light. An optical deck added to the system allows other laser sources to be incorporated into the UV beam-line and a lens system has been designed to couple these sources into a single delivery fiber with core diameters down to 50 microns. Our system incorporates five wavelengths [250 nm, 375 nm, 442 nm (HeCd), 543 nm (HeNe) and 638 nm (diode laser)] as the illumination source for a small diameter falloposcope designed for the study of the distal Fallopian tube origins of high grade serous ovarian cancer. The tunability of alexandrite offers the potential to generate other wavelengths in the 720-800, 360-400 and 240-265 nm ranges, plus other non-linear optical conversion techniques taking advantage of the high peak powers of the laser.
Laser System for Photoelectron and X-Ray Production in the PLEIADES Compton Light Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gibson, D J; Barty, C J; Betts, S M

2005-04-21

The PLEIADES (Picosecond Laser-Electron Interaction for the Dynamic Evaluation of Structures) facility provides tunable short x-ray pulses with energies of 30-140 keV and pulse durations of 0.3-5 ps by scattering an intense, ultrashort laser pulse off a 35-75 MeV electron beam. Synchronization of the laser and electron beam is obtained by using a photoinjector gun, and using the same laser system to generate the electrons and the scattering laser. The Ti Ti:Sapphire, chirped pulse amplification based 500 mJ, 50 fs, 810 nm scattering laser and the similar 300 {micro}J, 5 ps, 266 nm photoinjector laser systems are detailed. Additionally, anmore » optical parametric chirped pulse amplification (OPCPA) system is studied as a replacement for part of the scattering laser front end. Such a change would significantly simplify the set-up the laser system by removing the need for active switching optics, as well as increase the pre-pulse contrast ratio which will be important when part of the scattering laser is used as a pump beam in pump-probe diffraction experiments using the ultrashort tunable x-rays generated as the probe.« less
Single-longitudinal-mode Er:GGG microchip laser operating at 2.7 μm.

PubMed

You, Zhenyu; Wang, Yan; Xu, Jinlong; Zhu, Zhaojie; Li, Jianfu; Wang, Hongyan; Tu, Chaoyang

2015-08-15

We reported on a diode-end-pumped single-longitudinal-mode microchip laser using a 600-μm-thick Er:GGG crystal at ∼2.7 μm, generating a maximum output power of 50.8 mW and the maximum pulsed energy of 0.306 mJ, with repetition rates of pumping light of 300, 200, and 100 Hz, respectively. The maximum slope efficiency of the laser was 20.1%. The laser was operated in a single-longitudinal mode centered at about 2704 nm with a FWHM of 0.42 nm. The laser had a fundamental beam profile and the beam quality parameter M(2) was measured as 1.46. These results indicate that the Er:GGG microchip laser is a potential compact mid-infrared laser source.
UV laser interaction with a fluorescent dye solution studied using pulsed digital holography.

PubMed

Amer, Eynas; Gren, Per; Sjödahl, Mikael

2013-10-21

A frequency tripled Q-switched Nd-YAG laser (wavelength 355 nm, pulse duration 12 ns) has been used to pump Coumarin 153 dye solved in ethanol. Simultaneously, a frequency doubled pulse (532 nm) from the same laser is used to probe the solvent perpendicularly resulting in a gain through stimulated laser induced fluorescence (LIF) emission. The resulting gain of the probe beam is recorded using digital holography by blending it with a reference beam on the detector. Two digital holograms without and with the pump beam were recorded. Intensity maps were calculated from the recorded digital holograms and used to calculate the gain of the probe beam due to the stimulated LIF. In addition numerical data of the local temperature rise was calculated from the corresponding phase maps using Radon inversion. It was concluded that about 15% of the pump beam energy is transferred to the dye solution as heat while the rest is consumed in the radiative process. The results show that pulsed digital holography is a promising technique for quantitative study of fluorescent species.
LLE Review 98 (January-March 2004)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goncharov, V.N.

2004-08-10

This volume of the LLE Review, covering January-March 2004, features ''Performance of 1-THz-Bandwidth, 2-D Smoothing by Spectral Dispersion and Polarization Smoothing of High-Power, Solid-State Laser Beams'', by S. P. Regan, J. A. Marozas, R. S. Craxton, J. H. Kelly, W. R. Donaldson, P. A. Jaanimagi, D. Jacobs-Perkins, R. L. Keck, T. J. Kessler, D. D. Meyerhofer, T. C. Sangster, W. Seka, V.A. Smalyuk, S. Skupsky, and J. D. Zuegel (p. 49). Laser-beam smoothing achieved with 1-THz-bandwidth, two-dimensional smoothing by spectral dispersion and polarization smoothing on the 60-beam, 30-kJ, 351-nm OMEGA laser system is reported. These beam-smoothing techniques are directly applicablemore » to direct-drive ignition target designs for the 192-beam, 1.8-MJ, 351-nm National Ignition Facility. Equivalent-target-plane images for constant-intensity laser pulses of varying duration were used to determine the smoothing. The properties of the phase plates, frequency modulators, and birefringent wedges were simulated and found to be in good agreement with the measurements.« less
Optical design of f-theta lens for dual wavelength selective laser melting

NASA Astrophysics Data System (ADS)

Feng, Lianhua; Cao, Hongzhong; Zhang, Ning; Xu, Xiping; Duan, Xuanming

2016-10-01

F-theta lens is an important unit for selective laser melting (SLM) manufacture. The dual wavelength f-theta lens has not been used in SLM manufacture. Here, we present the design of the f-theta lens which satisfies SLM manufacture with coaxial 532 nm and 1030 nm 1080 nm laser beams. It is composed of three pieces of spherical lenses. The focal spots for 532 nm laser and 1030 nm 1080 nm laser are smaller than 35 μm and 70 μm, respectively. The results meet the demands of high precision SLM. The chromatic aberration could cause separation between two laser focal spots in the scanning plane, so chromatic aberration correction is very important to our design. The lateral color of the designed f-theta lens is less than 11 μm within the scan area of 150 mm x 150 mm, which meet the application requirements of dual wavelength selective laser melting.
Continued improvement in reduced-mode (REM) diodes enable 272 W from 105 μm 0.15 NA beam

NASA Astrophysics Data System (ADS)

Kanskar, M.; Bao, L.; Chen, Z.; Dawson, D.; DeVito, M.; Dong, W.; Grimshaw, M.; Guan, X.; Hemenway, M.; Martinsen, R.; Urbanek, W.; Zhang, S.

2017-02-01

High-power, high-brightness diode lasers from 8xx nm to 9xx nm have been pursued in many applications including fiber laser pumping, materials processing, solid-state laser pumping, and consumer electronics manufacturing. In particular, 915 nm - 976 nm diodes are of interest as diode pumps for the kilowatt CW fiber lasers. Thus, there have been many technical efforts on driving the diode lasers to have both high power and high brightness to achieve high-performance and reduced manufacturing costs. This paper presents our continued progress in the development of high brightness fiber-coupled product platform, elementTM. In the past decade, the amount of power coupled into a single 105 μm and 0.15 NA fiber has increased by over a factor of ten through improved diode laser brilliance and the development of techniques for efficiently coupling multiple emitters into a single fiber. In this paper, we demonstrate the further brightness improvement and power-scaling enabled by both the rise in chip brightness/power and the increase in number of chips coupled into a given numerical aperture. We report a new x-REM design with brightness as high as 4.3 W/mm-mrad at a BPP of 3 mm-mrad. We also report the record 272W from a 2×9 elementTM with 105 μm/0.15 NA beam using x-REM diodes and a new product introduction at 200W output power from 105 μm/0.15 NA beam at 915 nm.
Multi-Wavelength, Multi-Beam, and Polarization-Sensitive Laser Transmitter for Surface Mapping

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Ramos-Izquierdo, Luis; Harding, David; Huss, Tim

2011-01-01

A multi-beam, multi-color, polarized laser transmitter has been developed for mapping applications. It uses commercial off-the-shelf components for a lowcost approach for a ruggedized laser suitable for field deployment. The laser transmitter design is capable of delivering dual wavelengths, multiple beams on each wavelength with equal (or variable) intensities per beam, and a welldefined state of polarization. This laser transmitter has been flown on several airborne campaigns for the Slope Imaging Multi-Polarization Photon Counting Lidar (SIMPL) instrument, and at the time of this reporting is at a technology readiness level of between 5 and 6. The laser is a 1,064-nm microchip high-repetition-rate laser emitting energy of about 8 microjoules per pulse. The beam was frequency-doubled to 532 nm using a KTP (KTiOPO4) nonlinear crystal [other nonlinear crystals such as LBO (LiB3O5) or periodically poled lithium niobiate can be used as well, depending on the conversion efficiency requirements], and the conversion efficiency was approximately 30 percent. The KTP was under temperature control using a thermoelectric cooler and a feedback monitoring thermistor. The dual-wavelength beams were then spectrally separated and each color went through its own optical path, which consisted of a beam-shaping lens, quarterwave plate (QWP), and a birefringent crystal (in this case, a calcite crystal, but others such as vanadate can be used). The QWP and calcite crystal set was used to convert the laser beams from a linearly polarized state to circularly polarized light, which when injected into a calcite crystal, will spatially separate the circularly polarized light into the two linear polarized components. The spatial separation of the two linearly polarized components is determined by the length of the crystal. A second set of QWP and calcite then further separated the two beams into four. Additional sets of QWP and calcite can be used to further split the beams into multiple orders of two. The spatially separated beams had alternating linearly polarization states; a half-wave plate (HWP) array was then made to rotate the alternating states of A multi-beam, multi-color, polarized laser transmitter has been developed for mapping applications. It uses commercial off-the-shelf components for a lowcost approach for a ruggedized laser suitable for field deployment. The laser transmitter design is capable of delivering dual wavelengths, multiple beams on each wavelength with equal (or variable) intensities per beam, and a welldefined state of polarization. This laser transmitter has been flown on several airborne campaigns for the Slope Imaging Multi-Polarization Photon Counting Lidar (SIMPL) instrument, and at the time of this reporting is at a technology readiness level of between 5 and 6. The laser is a 1,064-nm microchip high-repetition-rate laser emitting energy of about 8 microjoules per pulse. The beam was frequency-doubled to 532 nm using a KTP (KTiOPO4) nonlinear crystal [other nonlinear crystals such as LBO (LiB3O5) or periodically poled lithium niobiate can be used as well, depending on the conversion efficiency requirements], and the conversion efficiency was approximately 30 percent. The KTP was under temperature control using a thermoelectric cooler and a feedback monitoring thermistor. The dual-wavelength beams were then spectrally separated and each color went through its own optical path, which consisted of a beam-shaping lens, quarterwave plate (QWP), and a birefringent crystal (in this case, a calcite crystal, but others such as vanadate can be used). The QWP and calcite crystal set was used to convert the laser beams from a linearly polarized state to circularly polarized light, which when injected into a calcite crystal, will spatially separate the circularly polarized light into the two linear polarized components. The spatial separation of the two linearly polarized components is determined by the length of the crystal. A cond set of QWP and calcite then further separated the two beams into four. Additional sets of QWP and calcite can be used to further split the beams into multiple orders of two. The spatially separated beams had alternating linearly polarization states; a half-wave plate (HWP) array was then made to rotate the alternating states of
Simulation of laser beam reflection at the sea surface modeling and validation

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Repasi, Endre

2013-06-01

A 3D simulation of the reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation is suitable for the pre-calculation of images for cameras operating in different spectral wavebands (visible, short wave infrared) for a bistatic configuration of laser source and receiver for different atmospheric conditions. In the visible waveband the calculated detected total power of reflected laser light from a 660nm laser source is compared with data collected in a field trial. Our computer simulation comprises the 3D simulation of a maritime scene (open sea/clear sky) and the simulation of laser beam reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. To predict the view of a camera the sea surface radiance must be calculated for the specific waveband. Additionally, the radiances of laser light specularly reflected at the wind-roughened sea surface are modeled considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). Validation of simulation results is prerequisite before applying the computer simulation to maritime laser applications. For validation purposes data (images and meteorological data) were selected from field measurements, using a 660nm cw-laser diode to produce laser beam reflection at the water surface and recording images by a TV camera. The validation is done by numerical comparison of measured total laser power extracted from recorded images with the corresponding simulation results. The results of the comparison are presented for different incident (zenith/azimuth) angles of the laser beam.
Biomodulation of light on cells in laser surgery

NASA Astrophysics Data System (ADS)

Liu, Timon C.; Li, Yan; Duan, Rui; Cai, Xiongwei

2002-04-01

In laser surgery, it has been observed pulsed 532-nm laser can avoid postoperative purpura, but pulsed 585-nm, 595-nm or 600-nm lasers nonetheless cause purpura when they were used to treat port-wine stains; the XeCl excimer laser (308 nm) can safely and effectively clear psoriasis; both XeCl excimer laser and Ho:YAG laser were used in coronary interventions, but only former was approved by the FDA; open channels after ultraviolet (UV) laser treatment and closed channels with infrared (IR) lasers for transmyocardial laser revascularization; and so on. In this paper, the biological information model of low intensity laser (BIML) is extended to include UVA biomodulation and is used to understand these phenomena. Although the central intensity of the laser beam is so intense that it destroys the tissue, the edge intensity is so low that it can induce biomodulation. Our investigation showed that biomodulation of light on cells might play an important role in the long-term effects of laser surgery.
CW 50W/M2 = 10.9 diode laser source by spectral beam combining based on a transmission grating.

PubMed

Zhang, Jun; Peng, Hangyu; Fu, Xihong; Liu, Yun; Qin, Li; Miao, Guoqing; Wang, Lijun

2013-02-11

An external cavity structure based on the -1st transmission grating is introduced to spectral beam combining a 970 nm diode laser bar. A CW output power of 50.8 W, an electro-optical conversion efficiency of 45%, a spectral beam combining efficiency of 90.2% and a holistic M(2) value of 10.9 are achieved. This shows a way for a diode laser source with several KW power and diffraction-limited beam quality at the same time.
Thermal emittance from ionization-induced trapping in plasma accelerators

DOE PAGES

Schroeder, C. B.; Vay, J. -L.; Esarey, E.; ...

2014-10-03

The minimum obtainable transverse emittance (thermal emittance) of electron beams generated and trapped in plasma-based accelerators using laser ionization injection is examined. The initial transverse phase space distribution following ionization and passage through the laser is derived, and expressions for the normalized transverse beam emittance, both along and orthogonal to the laser polarization, are presented. Results are compared to particle-in-cell simulations. Ultralow emittance beams can be generated using laser ionization injection into plasma accelerators, and examples are presented showing normalized emittances on the order of tens of nm.
Method of laser beam coding for control systems

NASA Astrophysics Data System (ADS)

Pałys, Tomasz; Arciuch, Artur; Walczak, Andrzej; Murawski, Krzysztof

2017-08-01

The article presents the method of encoding a laser beam for control systems. The experiments were performed using a red laser emitting source with a wavelength of λ = 650 nm and a power of P ≍ 3 mW. The aim of the study was to develop methods of modulation and demodulation of the laser beam. Results of research, in which we determined the effect of selected camera parameters, such as image resolution, number of frames per second on the result of demodulation of optical signal, is also shown in the paper. The experiments showed that the adopted coding method provides sufficient information encoded in a single laser beam (36 codes with the effectiveness of decoding at 99.9%).
Bioaerosol detection and classification using dual excitation wavelength laser-induced fluorescence

NASA Astrophysics Data System (ADS)

Jonsson, Per; Wästerby, Pär.; Gradmark, Per-Åke; Hedborg, Julia; Larsson, Anders; Landström, Lars

2015-05-01

We present results obtained by a detection system designed to measure laser-induced fluorescence from individual aerosol particles using dual excitation wavelengths. The aerosol is sampled from ambient air and via a 1 mm diameter nozzle, surrounded by a sheath air flow, confined into a particle beam. A continuous wave blue laser at 404 nm is focused on the aerosol beam and two photomultiplier tubes monitor the presence of individual particles by simultaneous measuring the scattered light and any induced fluorescence. When a particle is present in the detection volume, a laser pulse is triggered from an ultraviolet laser at 263 nm and the corresponding fluorescence spectrum is acquired with a spectrometer based on a diffraction grating and a 32 channel photomultiplier tube array with single-photon sensitivity. The spectrometer measures the fluorescence spectra in the wavelength region from 250 to 800 nm. In the present report, data were measured on different monodisperse reference aerosols, simulants of biological warfare agents, and different interference aerosol particles, e.g. pollen. In the analysis of the experimental data, i.e., the time-resolved scattered and fluorescence signals from 404 nm c.w. light excitation and the fluorescence spectra obtained by a pulsed 263 nm laser source, we use multivariate data analysis methods to classify each individual aerosol particle.
Beam shaping for cosmetic hair removal

NASA Astrophysics Data System (ADS)

Lizotte, Todd E.; Tuttle, Tracie

2007-09-01

Beam shaping has the potential to provide comfort to people who require or seek laser based cosmetic skin procedures. Of immediate interest is the procedure of aesthetic hair removal. Hair removal is performed using a variety of wavelengths from 480 to 1200 nm by means of filtered Xenon flash lamps (pulsed light) or 810 nm diode lasers. These wavelengths are considered the most efficient means available for hair removal applications, but current systems use simple reflector designs and plane filter windows to direct the light to the surface being exposed. Laser hair removal is achieved when these wavelengths at sufficient energy levels are applied to the epidermis. The laser energy is absorbed by the melanin (pigment) in the hair and hair follicle which in turn is transformed into heat. This heat creates the coagulation process, which causes the removal of the hair and prevents growth of new hair [1]. This paper outlines a technique of beam shaping that can be applied to a non-contact based hair removal system. Several features of the beam shaping technique including beam uniformity and heat dispersion across its operational treatment area will be analyzed. A beam shaper design and its fundamental testing will be discussed in detail.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, B.; Japan Science and Technology Agency, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo, 102-0075; Katan, C.

This study demonstrates a measurement system for a non-degenerate two-photon absorption (NDTPA) spectrum. The NDTPA light sources are a white light super continuum beam (WLSC, 500 ∼ 720 nm) and a fundamental beam (798 nm) from a Ti:Sapphire laser. A reliable broadband NDTPA spectrum is acquired in a single-shot detection procedure using a 128-channel lock-in amplifier. The NDTPA spectra for several common laser dyes are measured. Two photon absorption cross section enhancements are found in the experiment and validated by theoretical calculation for all of the chromophores.
Beam displacement as a function of temperature and turbulence length scale at two different laser radiation wavelengths.

PubMed

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
kW-level commercial Yb-doped aluminophosphosilicate ternary laser fiber

NASA Astrophysics Data System (ADS)

Sun, Shihao; Zhan, Huan; Li, Yuwei; Liu, Shuang; Jiang, Jiali; Peng, Kun; Wang, Yuying; Ni, Li; Wang, Xiaolong; Jiang, Lei; Yu, Juan; Liu, Gang; Lu, Pengfei; Wang, Jianjun; Jing, Feng; Lin, Aoxiang

2018-03-01

Based on a master oscillator power amplifier configuration, laser performance of commercial Nufern-20/400-8M Ybdoped aluminophosphosilicate ternary laser fiber was investigated. Pumped by 976 nm laser diodes, 982 W laser output power was obtained with a slope efficiency of 84.9%. Spectrum of output was centered at 1066.56nm with 3dB bandwidth less than 0.32 nm, and the nonlinearity suppression ratio was more than 39dB. Beam quality of Mx2 and M2y were 1.55 and 1.75 at 982 W, respectively. The laser performance indicated that Nufern-20/400-8M Yb-doped aluminophosphosilicate ternary laser fiber is highly competitive for industry fiber laser use.
Extracting the distribution of laser damage precursors on fused silica surfaces for 351 nm, 3 ns laser pulses at high fluences (20-150 J/cm2).

PubMed

Laurence, Ted A; Bude, Jeff D; Ly, Sonny; Shen, Nan; Feit, Michael D

2012-05-07

Surface laser damage limits the lifetime of optics for systems guiding high fluence pulses, particularly damage in silica optics used for inertial confinement fusion-class lasers (nanosecond-scale high energy pulses at 355 nm/3.5 eV). The density of damage precursors at low fluence has been measured using large beams (1-3 cm); higher fluences cannot be measured easily since the high density of resulting damage initiation sites results in clustering. We developed automated experiments and analysis that allow us to damage test thousands of sites with small beams (10-30 µm), and automatically image the test sites to determine if laser damage occurred. We developed an analysis method that provides a rigorous connection between these small beam damage test results of damage probability versus laser pulse energy and the large beam damage results of damage precursor densities versus fluence. We find that for uncoated and coated fused silica samples, the distribution of precursors nearly flattens at very high fluences, up to 150 J/cm2, providing important constraints on the physical distribution and nature of these precursors.
Tunable ultraviolet and blue light generation from Nd:YAB random laser bolstered by second-order nonlinear processes

NASA Astrophysics Data System (ADS)

Moura, André L.; Carreño, Sandra J. M.; Pincheira, Pablo I. R.; Fabris, Zanine V.; Maia, Lauro J. Q.; Gomes, Anderson S. L.; de Araújo, Cid B.

2016-06-01

Ultraviolet and blue light were obtained by nonlinear frequency conversion in a random laser (RL) based on Nd0.10Y0.90Al3(BO3)4 nanocrystalline powder. RL operation at 1062 nm, due to the 4F3/2 → 4I11/2 transition of neodymium ions (Nd3+), was achieved by exciting the Nd3+ with a tunable beam from 680 to 920 nm covering the ground state absorption transitions to the 4F9/2, (4F7/2,4S3/2), (4F5/2,2H9/2), and 4F3/2 states. Light from 340 to 460 nm was obtained via the second-harmonic generation of the excitation beam while tunable blue light, from 417 to 486 nm, was generated by self-sum-frequency mixing between the excitation beam and the RL emission.

Single laser based pump-probe technique to study plasma shielding during nanosecond laser ablation of copper thin films

NASA Astrophysics Data System (ADS)

Nammi, Srinagalakshmi; Vasa, Nilesh J.; Gurusamy, Balaganesan; Mathur, Anil C.

2017-09-01

A plasma shielding phenomenon and its influence on micromachining is studied experimentally and theoretically for laser wavelengths of 355 nm, 532 nm and 1064 nm. A time resolved pump-probe technique is proposed and demonstrated by splitting a single nanosecond Nd3+:YAG laser into an ablation laser (pump laser) and a probe laser to understand the influence of plasma shielding on laser ablation of copper (Cu) clad on polyimide thin films. The proposed nanosecond pump-probe technique allows simultaneous measurement of the absorption characteristics of plasma produced during Cu film ablation by the pump laser. Experimental measurements of the probe intensity distinctly show that the absorption by the ablated plume increases with increase in the pump intensity, as a result of plasma shielding. Theoretical estimation of the intensity of the transmitted pump beam based on the thermo-temporal modeling is in qualitative agreement with the pump-probe based experimental measurements. The theoretical estimate of the depth attained for a single pulse with high pump intensity value on a Cu thin film is limited by the plasma shielding of the incident laser beam, similar to that observed experimentally. Further, the depth of micro-channels produced shows a similar trend for all three wavelengths, however, the channel depth achieved is lesser at the wavelength of 1064 nm.
16 W output power by high-efficient spectral beam combining of DBR-tapered diode lasers.

PubMed

Müller, André; Vijayakumar, Deepak; Jensen, Ole Bjarlin; Hasler, Karl-Heinz; Sumpf, Bernd; Erbert, Götz; Andersen, Peter E; Petersen, Paul Michael

2011-01-17

Up to 16 W output power has been obtained using spectral beam combining of two 1063 nm DBR-tapered diode lasers. Using a reflecting volume Bragg grating, a combining efficiency as high as 93.7% is achieved, resulting in a single beam with high spatial coherence. The result represents the highest output power achieved by spectral beam combining of two single element tapered diode lasers. Since spectral beam combining does not affect beam propagation parameters, M2-values of 1.8 (fast axis) and 3.3 (slow axis) match the M2-values of the laser with lowest spatial coherence. The principle of spectral beam combining used in our experiments can be expanded to combine more than two tapered diode lasers and hence it is expected that the output power may be increased even further in the future.
Formation of 2D bright spatial solitons in lithium niobate with photovoltaic response and incoherent background

NASA Astrophysics Data System (ADS)

Pustozerov, A.; Shandarov, V.

2017-12-01

The influence of incoherent background illumination produced by light-emitting diodes (LED's) of different average wavelengths and laser diode emitting in blue region of visible on diffraction characteristics of narrow coherent light beams of He-Ne laser due to refractive index changes of Fe-doped lithium niobate sample are studied. It has been experimentally demonstrated that nonlinear diffraction of red beams with wavelength 633 nm and diameters on full width of half maximum (FWHM) near to 15 μm may be totally compensated using background light with average wavelengths 450 - 465 nm. To provide the necessary intensity of incoherent background, the combinations of spherical and cylindrical concave lenses with blue LED and laser diode module without focusing its beam have been used.
Fabrication of the polarization independent spectral beam combining grating

NASA Astrophysics Data System (ADS)

Liu, Quan; Jin, Yunxia; Wu, Jianhong; Guo, Peiliang

2016-03-01

Owing to damage, thermal issues, and nonlinear optical effects, the output power of fiber laser has been proven to be limited. Beam combining techniques are the attractive solutions to achieve high-power high-brightness fiber laser output. The spectral beam combining (SBC) is a promising method to achieve high average power output without influencing the beam quality. A polarization independent spectral beam combining grating is one of the key elements in the SBC. In this paper the diffraction efficiency of the grating is investigated by rigorous coupled-wave analysis (RCWA). The theoretical -1st order diffraction efficiency of the grating is more than 95% from 1010nm to 1080nm for both TE and TM polarizations. The fabrication tolerance is analyzed. The polarization independent spectral beam combining grating with the period of 1.04μm has been fabricated by holographic lithography - ion beam etching, which are within the fabrication tolerance.
Thermal lensing in ocular media

NASA Astrophysics Data System (ADS)

Vincelette, Rebecca Lee

2009-12-01

This research was a collaborative effort between the Air Force Research Laboratory (AFRL) and the University of Texas to examine the laser-tissue interaction of thermal lensing induced by continuous-wave, CW, near-infrared, NIR, laser radiation in the eye and its influence on the formation of a retinal lesion from said radiation. CW NIR laser radiation can lead to a thermal lesion induced on the retina given sufficient power and exposure duration as related to three basic parameters; the percent of transmitted energy to, the optical absorption of, and the size of the laser-beam created at the retina. Thermal lensing is a well-known phenomenon arising from the optical absorption, and subsequent temperature rise, along the path of the propagating beam through a medium. Thermal lensing causes the laser-beam profile delivered to the retina to be time dependent. Analysis of a dual-beam, multidimensional, high-frame rate, confocal imaging system in an artificial eye determined the rate of thermal lensing in aqueous media exposed to 1110, 1130, 1150 and 1318-nm wavelengths was related to the power density created along the optical axis and linear absorption coefficient of the medium. An adaptive optics imaging system was used to record the aberrations induced by the thermal lens at the retina in an artificial eye during steady-state. Though the laser-beam profiles changed over the exposure time, the CW NIR retinal damage thresholds between 1110--1319-nm were determined to follow conventional fitting algorithms which neglected thermal lensing. A first-order mathematical model of thermal lensing was developed by conjoining an ABCD beam propagation method, Beer's law of attenuation, and a solution to the heat-equation with respect to radial diffusion. The model predicted that thermal lensing would be strongest for small (< 4-mm) 1/e2 laser-beam diameters input at the corneal plane and weakly transmitted wavelengths where less than 5% of the energy is delivered to the retina. The model predicted thermal lensing would cause the retinal damage threshold for wavelengths above 1300-nm to increase with decreasing beam-diameters delivered to the corneal plane, a behavior which was opposite of equivalent conditions simulated without thermal lensing.
Compact 2100 nm laser diode module for next-generation DIRCM

NASA Astrophysics Data System (ADS)

Dvinelis, Edgaras; Greibus, Mindaugas; TrinkÅ«nas, Augustinas; NaujokaitÄ--, Greta; Vizbaras, Augustinas; Vizbaras, Dominykas; Vizbaras, Kristijonas

2017-10-01

Compact high-power 2100 nm laser diode module for next-generation directional infrared countermeasure (DIRCM) systems is presented. Next-generation DIRCM systems require compact, light-weight and robust laser modules which could provide intense IR light emission capable of disrupting the tracking sensor of heat-seeking missile. Currently used solid-state and fiber laser solutions for mid-IR band are bulky and heavy making them difficult to implement in smaller form-factor DIRCM systems. Recent development of GaSb laser diode technology greatly improved optical output powers and efficiencies of laser diodes working in 1900 - 2450 nm band [1] while also maintaining very attractive size, weight, power consumption and cost characteristics. 2100 nm laser diode module presented in this work performance is based on high-efficiency broad emitting area GaSb laser diode technology. Each laser diode emitter is able to provide 1 W of CW output optical power with working point efficiency up to 20% at temperature of 20 °C. For output beam collimation custom designed fast-axis collimator and slow-axis collimator lenses were used. These lenses were actively aligned and attached using UV epoxy curing. Total 2 emitters stacked vertically were used in 2100 nm laser diode module. Final optical output power of the module goes up to 2 W at temperature of 20 °C. Total dimensions of the laser diode module are 35 x 25 x 16 mm (L x W x H) with a weight of 28 grams. Finally output beam is bore-sighted to mechanical axes of the module housing allowing for easy integration into next-generation DIRCM systems.
Improving the therapeutic window of retinal photocoagulation by spatial and temporal modulation of the laser beam

NASA Astrophysics Data System (ADS)

Sramek, Christopher; Leung, Loh-Shan; Leng, Theodore; Brown, Jefferson; Paulus, Yannis M.; Schuele, Georg; Palanker, Daniel

2011-02-01

Decreasing the pulse duration helps confine damage, shorten treatment time, and minimize pain during retinal photocoagulation. However, the safe therapeutic window (TW), the ratio of threshold powers for thermomechanical rupture of Bruch's membrane and mild coagulation, also decreases with shorter exposures. Two potential approaches toward increasing TW are investigated: (a) decreasing the central irradiance of the laser beam and (b) temporally modulating the pulse. An annular beam with adjustable central irradiance was created by coupling a 532-nm laser into a 200-μm core multimode optical fiber at a 4-7 deg angle to normal incidence. Pulse shapes were optimized using a computational model, and a waveform generator was used to drive a PASCAL photocoagulator (532 nm), producing modulated laser pulses. Acute thresholds for mild coagulation and rupture were measured in Dutch-Belted rabbit in vivo with an annular beam (154-163 μm retinal diameter) and modulated pulse (132 μm, uniform irradiance ``flat-top'' beam) with 2-50 ms pulse durations. Thresholds with conventional constant-power pulse and a flat-top beam were also determined. Both annular beam and modulated pulse provided a 28% increase in TW at 10-ms duration, affording the same TW as 20-ms pulses with conventional parameters.
Diode injection - seeded, 940 nanometer (nm), titanium - sapphire laser for H2O DIAL (differential absorption lidar), measurements

NASA Technical Reports Server (NTRS)

Miller, George E.

1992-01-01

Differential absorption of laser radiation by various molecular species represents both a selective and a sensitive method of measuring specific atmospheric constituents. DIAL measurements can be carried out via two different means. Both involve using two laser pulses with slightly different wavelengths (lambda), (one lambda at a strong absorption line of the molecule of interest, the other detuned into the wing of the line), and comparing the attenuation of the pulses. One approach relies on scattering of the radiation from some conveniently located topographical target. In the other technique elastic scattering from atmospheric aerosols and particulates is used to return the radiation to the lidar receiver system. This case is referred to as the differential absorption and scattering technique, and is the technique we are interested in to measure water vapor at 940 nm. The 940 nm wavelength is extremely desirable to atmospheric scientist interested in accurate DIAL measurements of H2O in the upper and lower troposphere. Simulated measurements using approximately 940 nm and 815 nm lasers at a range of altitudes and experimental conditions are shown. By offering access to larger absorption cross-sections, injected seeded, 940 nm DIAL laser transmitters would allow for more accurate water profile measurements at altitudes from 6 to 16 km than is currently possible with 730 nm and 815 nm DIAL laser transmitters. We have demonstrated the operation of an injected seeded titanium-sapphire (TS) laser operating at approximately 940 nm with an energy of more than 90 mJ per pulse. The TS laser is pumped by a commercial, 600 mJ, 532 nm, 10 Hz Nd:YAG laser. The slope efficiency of the laser using a flat 50 percent R output coupler and a 10 m end-mirror is shown. The laser was injected seeded with a CW, AlGaAs, semiconductor diode laser which had an output of 83 mW. The CW diode seed beam was introduced into the TS laser cavity through a HR end-mirror. When the diode beam is aligned to the TS resonator, it controls the TS laser output wavelength and its spectral line width with the required resolution for DIAL applications. This work supports the need for the development of 940 nm, titanium-sapphire DIAL transmitters.
Electron-beam pumped laser structures based on MBE grown {ZnCdSe}/{ZnSe} superlattices

NASA Astrophysics Data System (ADS)

Kozlovsky, V. I.; Shcherbakov, E. A.; Dianov, E. M.; Krysa, A. B.; Nasibov, A. S.; Trubenko, P. A.

1996-02-01

Cathodoluminescence (CL), photoreflection (PR), phototransmission (PT) of single and multiquantum wells (MQWs) and strain layer {ZnCdSe}/{ZnSe} superlattices (SLs) grown by molecular beam epitaxy (MBE) were studied. An increase of the Stokes shift with the number of quantum wells (QWs) and the appearance of new lines in CL and PT spectra were observed. Room temperature (RT) vertical-cavity surface-emitting laser (VCSEL) operation was achieved by using the SL structures. Output power up to 2.2 W in single longitudinal mode with λ = 493 nm was obtained. Cut facet laser wavelength of the same SL structure was 502 nm.
Generation of spectrally-stable continuous-wave emission and ns pulses at 800 nm and 975 nm with a peak power of 4 W using a distributed Bragg reflector laser and a ridge-waveguide power amplifier

NASA Astrophysics Data System (ADS)

Klehr, A.; Wenzel, H.; Fricke, J.; Bugge, F.; Liero, A.; Hoffmann, Th.; Erbert, G.; Tränkle, G.

2015-03-01

Semiconductor based sources which emit high-power spectrally stable nearly diffraction-limited optical pulses in the nanosecond range are ideally suited for a lot of applications, such as free-space communications, metrology, material processing, seed lasers for fiber or solid state lasers, spectroscopy, LIDAR and frequency doubling. Detailed experimental investigations of 975 nm and 800 nm diode lasers based on master oscillator power amplifier (MOPA) light sources are presented. The MOPA systems consist of distributed Bragg reflector lasers (DBR) as master oscillators driven by a constant current and ridge waveguide power amplifiers which can be driven DC and by current pulses. In pulse regime the amplifiers modulated with rectangular current pulses of about 5 ns width and a repetition frequency of 200 kHz act as optical gates, converting the continuous wave (CW) input beam emitted by the DBR lasers into a train of short optical pulses which are amplified. With these experimental MOPA arrangements no relaxation oscillations in the pulse power occur. With a seed power of about 5 mW at a wavelength of 973 nm output powers behind the amplifier of about 1 W under DC injection and 4 W under pulsed operation, corresponding to amplification factors of 200 (amplifier gain 23 dB) and 800 (gain 29 dB) respectively, are reached. At 800 nm a CW power of 1 W is obtained for a seed power of 40 mW. The optical spectra of the emission of the amplifiers exhibit a single peak at a constant wavelength with a line width < 10 pm in the whole investigated current ranges. The ratios between laser and ASE levels were > 50 dB. The output beams are nearly diffraction limited with beam propagation ratios M2lat ~ 1.1 and M2ver ~ 1.2 up to 4 W pulse power.
Efficient upconversion polymer-inorganic nanocomposite thin film emitters prepared by the double beam matrix assisted pulsed laser evaporation (DB-MAPLE)

NASA Astrophysics Data System (ADS)

Darwish, Abdalla M.; Burkett, Allan; Blackwell, Ashley; Taylor, Keylantra; Walker, Vernell; Sarkisov, Sergey; Koplitz, Brent

2014-09-01

We report on fabrication and investigation of optical and morphological properties of highly efficient (a quantum yield of 1%) upconversion polymer-inorganic nanocomposite thin film emitters prepared by the new technique of double beam matrix assisted pulsed laser evaporation (DB-MAPLE). Polymer poly(methyl methacrylate) (PMMA) host was evaporated on a silicon substrate using a 1064-nm pulsed laser beam using a target made of frozen (to the temperature of liquid nitrogen) solution of PMMA in chlorobenzene. Concurrently, the second 532-nm pulsed beam from the same laser was used to impregnate the polymer host with the inorganic nanoparticulate made of the rare earth upconversion compounds NaYF4: Yb3+, Er3+, NaYF4: Yb3+, Ho3+, and NaYF4: Yb3+, Tm3+. The compounds were initially synthesized using the wet process, baked, and compressed in solid pellet targets. The proposed DB-MAPLE method has the advantage of making highly homogeneous nanocomposite films with precise control of the doping rate due to the optimized overlapping of the plumes produced by the ablation of the organic and inorganic target with the infrared and visible laser beams respectively. X-ray diffraction, electron and atomic force microscopy, and optical fluorescence spectroscopy indicated that the inorganic nanoparticulate preserved its crystalline structure and upconversion properties (strong emission in green, red, and blue bands upon illumination with 980-nm laser diode) after being transferred from the target in the polymer nanocomposite film. The produced films can be used in applications varying from the efficiency enhancement of the photovoltaic cells, optical sensors and biomarkers to anti-counterfeit labels.
Structure and properties of optical-discharge plasma in CO2-laser beam near target surface

NASA Astrophysics Data System (ADS)

Danshchikov, Ye. V.; Dymshakov, V. A.; Lebedev, F. V.; Ryazanov, A. V.

1986-05-01

An experimental study of optical-discharge plasma in a CO2-laser beam at a target surface was made for the purpose of exploring the not yet understood role of this plasma in the laser-target interaction process. Such a plasma was produced by means of a quasi-continuous CO2-laser with an unstable resonator, its power being maintained constant for 1 ms periods. Its radiation was focused on the surfaces of thick and seeding thin Al, Ti, and Ta targets inclined at an approximately 70 deg. angle to the beam, inside a hermetic chamber containing air, argon, or helium under atmospheric pressure. The radiation intensity distribution over the focal plane and the nearest caustic surface in the laser beam was measured along with the plasma parameters, the latter by the methods of spectral analysis and photoelectric recording. The instrumentation for this purpose included an MDR-3 monochromator with an entrance slit, a double electron-optical converter, a memory oscillograph, and an SI-10-30 ribbon lamp as radiation reference standard. The results yielded integral diametral intensity distributions of the emission lines Ti-II (457.2 nm), Ti-I (464 nm), Ar-II (462 nm), radial and axial temperature profiles of optical discharge in metal vapor in surrounding gas, and the radial temperature profile of irradiated metal surface at successive instants of time. The results reveal marked differences between the structures and the properties of optical-discharge plasma in metal vapor and in surrounding gas, optical discharge in the former being characterized by localization within the laser beam and optical discharge in the latter being characterized by a drift away from the target.
High average-power 2 μm radiation generated by intracavity KTP OPO

NASA Astrophysics Data System (ADS)

He, Guangyuan; Guo, Jing; Jiao, Zhongxing; Wang, Biao

2015-09-01

A high average-power 2 μm laser with good beam quality based on an intracavity potassium titanium oxide phosphate (KTP) optical parametric oscillator (OPO) is demonstrated. A concave lens is used in the 1064 nm Nd:YAG pumped laser cavity to compensate for the thermal lensing of the laser rod. The cavity length of the KTP OPO is enlarged to improve the 2 μm beam quality. The maximum average output of the 2 μm laser is up to 18 W at 7 kHz with M 2 less than 6 and pulse width of 70 ns. The FWHM of the signal and idle lights are both less than 3 nm.
Dual-pump CARS temperature and major species concentration measurements in counter-flow methane flames using narrowband pump and broadband Stokes lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thariyan, Mathew P.; Ananthanarayanan, Vijaykumar; Bhuiyan, Aizaz H.

2010-07-15

Dual-pump coherent anti-Stokes Raman scattering (CARS) is used to measure temperature and species profiles in representative non-premixed and partially-premixed CH{sub 4}/O{sub 2}/N{sub 2} flames. A new laser system has been developed to generate a tunable single-frequency beam for the second pump beam in the dual-pump N{sub 2}-CO{sub 2} CARS process. The second harmonic output ({proportional_to}532 nm) from an injection-seeded Nd:YAG laser is used as one of the narrowband pump beams. The second single-longitudinal-mode pump beam centered near 561 nm is generated using an injection-seeded optical parametric oscillator, consisting of two non-linear {beta}-BBO crystals, pumped using the third harmonic output ({proportional_to}355more » nm) of the same Nd:YAG laser. A broadband dye laser (BBDL), pumped using the second harmonic output of an unseeded Nd:YAG laser, is employed to produce the Stokes beam centered near 607 nm with full-width-at-half-maximum of {proportional_to}250 cm{sup -1}. The three beams are focused between two opposing nozzles of a counter-flow burner facility to measure temperature and major species concentrations in a variety of CH{sub 4}/O{sub 2}/N{sub 2} non-premixed and partially-premixed flames stabilized at a global strain rate of 20 s{sup -1} at atmospheric-pressure. For the non-premixed flames, excellent agreement is observed between the measured profiles of temperature and CO{sub 2}/N{sub 2} concentration ratios with those calculated using an opposed-flow flame code with detailed chemistry and molecular transport submodels. For partially-premixed flames, with the rich side premixing level beyond the stable premixed flame limit, the calculations overestimate the distance between the premixed and the non-premixed flamefronts. Consequently, the calculated temperatures near the rich, premixed flame are higher than those measured. Accurate prediction of the distance between the premixed and the non-premixed flames provides an interesting challenge for future computations. (author)« less
Renal denervation using focused infrared fiber lasers: a potential treatment for hypertension.

PubMed

Alexander, Vinay V; Shi, Zhennan; Iftekher, Fariha; Welsh, Michael J; Gurm, Hitinder S; Rising, Gail; Yanovich, Amber; Walacavage, Kim; Islam, Mohammed N

2014-11-01

Renal denervation has recently become of great interest as a potential treatment for resistant hypertension. Denervation techniques using radio frequency (RF) or ultrasound energy sources have already been explored in literature. In this study, we investigate the use of lasers as a potential energy source for renal denervation. In vitro studies are performed in porcine/ovine renal arteries with focused laser beams at 980 nm, 1210 nm, and 1700 nm to study the ability to damage renal nerves without causing injury to non-target tissue structures like the endothelium. Then, a 980 nm laser catheter prototype is built and used to demonstrate in vivo renal denervation in ovine renal arteries. This study utilizes fiber coupled infrared lasers at 980 nm, 1210 nm, and 1700 nm. In vitro laser denervation studies at 980 nm are performed in both porcine and ovine renal arteries to study the ability of focused laser beams to damage renal nerves without injuring the endothelium. In vitro studies using lasers close to the lipid absorption lines at 1210 nm and 1700 nm are also performed in porcine renal arteries to study the possibility of selectively damaging the renal nerves by targeting the lipid myelin sheaths surrounding the nerves. Then, a laser catheter prototype is designed and built for in vivo renal denervation in ovine renal arteries using the 980 nm laser (powers ranging from 2 to 4 W, 5 seconds per exposure). Histochemical evaluations of the frozen sections are performed using methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. Histochemical analysis of in vitro laser treatments at 980 nm in porcine and ovine renal arteries show clear evidence of laser-induced renal nerve damage without injury to the endothelium and part of the media. No evidence of selective nerve damage is observed using the 1210 nm and 1700 nm lasers with the current treatment parameters. Histochemical analysis of in vivo laser treatments in ovine renal arteries using a focused 980 nm laser show clear evidence of renal nerve damage with depths of damage extending > 1.5 mm from the artery wall. Sections with laser-induced damage to the media/adventitia at depths of > 1 mm without injury to the endothelium are also observed. We demonstrate the use of focused lasers as an attractive energy source for causing renal nerve damage without injury to the artery wall and thus, may have potential therapeutic applications for conditions such as resistant hypertension, where renal denervation has been shown to be a promising form of treatment. © 2014 Wiley Periodicals, Inc.
Automated translating beam profiler for in situ laser beam spot-size and focal position measurements

NASA Astrophysics Data System (ADS)

Keaveney, James

2018-03-01

We present a simple and convenient, high-resolution solution for automated laser-beam profiling with axial translation. The device is based on a Raspberry Pi computer, Pi Noir CMOS camera, stepper motor, and commercial translation stage. We also provide software to run the device. The CMOS sensor is sensitive over a large wavelength range between 300 and 1100 nm and can be translated over 25 mm along the beam axis. The sensor head can be reversed without changing its axial position, allowing for a quantitative estimate of beam overlap with counter-propagating laser beams. Although not limited to this application, the intended use for this device is the automated measurement of the focal position and spot-size of a Gaussian laser beam. We present example data of one such measurement to illustrate device performance.
Automated translating beam profiler for in situ laser beam spot-size and focal position measurements.

PubMed

Keaveney, James

2018-03-01

We present a simple and convenient, high-resolution solution for automated laser-beam profiling with axial translation. The device is based on a Raspberry Pi computer, Pi Noir CMOS camera, stepper motor, and commercial translation stage. We also provide software to run the device. The CMOS sensor is sensitive over a large wavelength range between 300 and 1100 nm and can be translated over 25 mm along the beam axis. The sensor head can be reversed without changing its axial position, allowing for a quantitative estimate of beam overlap with counter-propagating laser beams. Although not limited to this application, the intended use for this device is the automated measurement of the focal position and spot-size of a Gaussian laser beam. We present example data of one such measurement to illustrate device performance.
Scaling the spectral beam combining channel by multiple diode laser stacks in an external cavity

NASA Astrophysics Data System (ADS)

Meng, Huicheng; Ruan, Xu; Du, Weichuan; Wang, Zhao; Lei, Fuchuan; Yu, Junhong; Tan, Hao

2017-04-01

Spectral beam combining of a broad area diode laser is a promising technique for direct diode laser applications. We present an experimental study of three mini-bar stacks in an external cavity on spectral beam combining in conjunction with spatial beam combining. At the pump current of 70 A, a CW output power of 579 W, spectral bandwidth of 18.8 nm and electro-optical conversion efficiency of 47% are achieved. The measured M 2 values of spectral beam combining are 18.4 and 14.7 for the fast and the slow axis, respectively. The brightness of the spectral beam combining output is 232 MW · cm-2 · sr-1.
Recent results from experimental studies on laser-plasma coupling in a shock ignition relevant regime

NASA Astrophysics Data System (ADS)

Koester, P.; Antonelli, L.; Atzeni, S.; Badziak, J.; Baffigi, F.; Batani, D.; Cecchetti, C. A.; Chodukowski, T.; Consoli, F.; Cristoforetti, G.; De Angelis, R.; Folpini, G.; Gizzi, L. A.; Kalinowska, Z.; Krousky, E.; Kucharik, M.; Labate, L.; Levato, T.; Liska, R.; Malka, G.; Maheut, Y.; Marocchino, A.; Nicolai, P.; O'Dell, T.; Parys, P.; Pisarczyk, T.; Raczka, P.; Renner, O.; Rhee, Y. J.; Ribeyre, X.; Richetta, M.; Rosinski, M.; Ryc, L.; Skala, J.; Schiavi, A.; Schurtz, G.; Smid, M.; Spindloe, C.; Ullschmied, J.; Wolowski, J.; Zaras, A.

2013-12-01

Shock ignition (SI) is an appealing approach in the inertial confinement scenario for the ignition and burn of a pre-compressed fusion pellet. In this scheme, a strong converging shock is launched by laser irradiation at an intensity Iλ2 > 1015 W cm-2 µm2 at the end of the compression phase. In this intensity regime, laser-plasma interactions are characterized by the onset of a variety of instabilities, including stimulated Raman scattering, Brillouin scattering and the two plasmon decay, accompanied by the generation of a population of fast electrons. The effect of the fast electrons on the efficiency of the shock wave production is investigated in a series of dedicated experiments at the Prague Asterix Laser Facility (PALS). We study the laser-plasma coupling in a SI relevant regime in a planar geometry by creating an extended preformed plasma with a laser beam at ˜7 × 1013 W cm-2 (250 ps, 1315 nm). A strong shock is launched by irradiation with a second laser beam at intensities in the range 1015-1016 W cm-2 (250 ps, 438 nm) at various delays with respect to the first beam. The pre-plasma is characterized using x-ray spectroscopy, ion diagnostics and interferometry. Spectroscopy and calorimetry of the backscattered radiation is performed in the spectral range 250-850 nm, including (3/2)ω, ω and ω/2 emission. The fast electron production is characterized through spectroscopy and imaging of the Kα emission. Information on the shock pressure is obtained using shock breakout chronometry and measurements of the craters produced by the shock in a massive target. Preliminary results show that the backscattered energy is in the range 3-15%, mainly due to backscattered light at the laser wavelength (438 nm), which increases with increasing the delay between the two laser beams. The values of the peak shock pressures inferred from the shock breakout times are lower than expected from 2D numerical simulations. The same simulations reveal that the 2D effects play a major role in these experiments, with the laser spot size comparable with the distance between critical and ablation layers.
Reflective diffractive beam splitter for laser interferometers.

PubMed

Fahr, Stephan; Clausnitzer, Tina; Kley, Ernst-Bernhard; Tünnermann, Andreas

2007-08-20

The first realization of a reflective 50/50 beam splitter based on a dielectric diffraction grating suitable for high-power laser interferometers is reported. The beam splitter is designed to operate at a wavelength of 1064 nm and in s polarization. To minimize the performance degradation of the device that is due to fabrication fluctuations, during the design process special attention was paid to achieve high fabrication tolerances especially of groove width and depth. Applying this beam splitter to high-power laser interferometers, such as future gravitational wave detectors, will avoid critical thermal lensing effects and allow for the free choice of substrate materials.

Laser beam machining of polycrystalline diamond for cutting tool manufacturing

NASA Astrophysics Data System (ADS)

Wyszyński, Dominik; Ostrowski, Robert; Zwolak, Marek; Bryk, Witold

2017-10-01

The paper concerns application of DPSS Nd: YAG 532nm pulse laser source for machining of polycrystalline WC based diamond inserts (PCD). The goal of the research was to determine optimal laser cutting parameters for cutting tool shaping. Basic criteria to reach the goal was cutting edge quality (minimalization of finishing operations), material removal rate (time and cost efficiency), choice of laser beam characteristics (polarization, power, focused beam diameter). The research was planned and realised and analysed according to design of experiment rules (DOE). The analysis of the cutting edge was prepared with use of Alicona Infinite Focus measurement system.
Precise optical dosimetry in low-level laser therapy of soft tissues in oral cavity

NASA Astrophysics Data System (ADS)

Stoykova, Elena V.; Sabotinov, O.

2004-06-01

The new low level laser therapy (LLLT) is widely applied for treatment of diseases of the oral mucosa and parodont. Depending on indication, different optical tips and light-guides are used to create beams with a required shape. However, to the best of our knowledge, the developed irradiation geometries are usually proposed assuming validity of Bouger-Lambert law. This hardly corresponds to the real situation because of the dominating multiple scattering within 600-1200 nm range that destroys correlation between the emitted laser beam and the spatial distribution of the absorbed dose inside the tissue. The aim of this work is to base the dosimetry of the LLLT procedures of periodontal tissues on radiation transfer theory using a flexible Monte-Carlo code. We studied quantitatively the influence of tissue optical parameters (absorption and scattering coefficients, tissue refraction index, anisotropy factor) on decreasing of correlation between the emitted beam and the energy deposition for converging or diverging beams. We evaluated energy deposition for the developed by us LLLT system in a 3-D model of periodontal tissues created using a cross-sectional image of this region with internal structural information on the gingival and the tooth. The laser source is a CW diode laser emitting elliptical beam within 650-675 nm at output power 5-30 mW. To determine the geometry of the irradiating beam we used CCD camera Spiricon LBA 300.
Multicascade X-Ray Free-Electron Laser with Harmonic Multiplier and Two-Frequency Undulator

NASA Astrophysics Data System (ADS)

Zhukovsky, K. V.

2018-06-01

The feasibility of generation of powerful x-ray radiation by a cascade free-electron laser (FEL) with amplification of higher harmonics using a two-frequency undulator is studied. To analyze the FEL operation, a complex phenomenological single-pass FEL model is developed and used. It describes linear and nonlinear generation of harmonics in the FEL with seed laser that takes into account initial electron beam noise and describes all main losses of each harmonic in each FEL cascade. The model is also calibrated against and approved by the experimental FEL data and available results of three-dimensional numerical simulation. The electron beam in the undulator is assumed to be matched and focused, and the dynamics of power in the singlepass FEL with cascade harmonic multipliers is investigated to obtain x-ray laser radiation in the FEL having the shortest length, beam energy, and frequency of the seed laser as low as possible. In this context, the advantages of the two-frequency undulator used for generation of harmonics are demonstrated. The evolution of harmonics in a multicascade FEL with multiplication of harmonics is investigated. The operation of the cascade FEL at the wavelength λ = 1.14 nm, generating 30 MW already on 38 m with the seed laser operating at a wavelength of 11.43 nm corresponding to the maximal reflectivity of the multilayered mirror MoRu/Be coating is investigated. In addition, the operation of the multicascade FEL with accessible seed UVlaser operating at a wavelength of 157 nm (F2 excimer UV-laser) and electron beam with energy of 0.5 GeV is investigated. X-ray radiation simulated in it at the wavelength λ 3.9 nm reaches power of 50 MW already at 27 m, which is by two orders of magnitude shorter than 3.4 km of the x-ray FEL recently put into operation in Europe.
Diode-pumped cw Nd:YAG three-level laser at 869 nm.

PubMed

Lü, Yanfei; Xia, Jing; Cheng, Weibo; Chen, Jifeng; Ning, Guobin; Liang, Zuoliang

2010-11-01

We report for the first time (to our knowledge) a diode-pumped Nd:YAG laser emitting at 869 nm based on the (4)F(3/2)-(4)I(9/2) transition, generally used for a 946 nm emission. Power of 453 mW at 869 nm has been achieved in cw operation with a fiber-coupled laser diode emitting 35.4 W at 809 nm. Intracavity second-harmonic generation in the cw mode has also been demonstrated with power of 118 mW at 435 nm by using a BiB(3)O(6) nonlinear crystal. In our experiment, we used a LiNbO(3) crystal lens to complement the thermal lens of the laser rod, and we obtained good beam quality and high output power stability.
Laser induced white lighting of tungsten filament

NASA Astrophysics Data System (ADS)

Strek, W.; Tomala, R.; Lukaszewicz, M.

2018-04-01

The sustained bright white light emission of thin tungsten filament was induced under irradiation with focused beam of CW infrared laser diode. The broadband emission centered at 600 nm has demonstrated the threshold behavior on excitation power. Its intensity increased non-linearly with excitation power. The emission occurred only from the spot of focused beam of excitation laser diode. The white lighting was accompanied by efficient photocurrent flow and photoelectron emission which both increased non-linearly with laser irradiation power.
Mechanism of nanosecond laser drilling process of 4H-SiC for through substrate vias

NASA Astrophysics Data System (ADS)

Kim, Byunggi; Iida, Ryoichi; Doan, Duc Hong; Fushinobu, Kazuyoshi

2017-06-01

Role of optical parameters on nanosecond laser drilling of 4H-SiC was experimentally studied. Using ns pulsed Nd:YAG laser, parametric studies on effects of wavelength (1064 nm or 532 nm), beam profile (Gaussian or Bessel), and ambient condition (air or water) were conducted. The wavelengths which have large optical penetration depth were selected as wavefront has to propagate through materials to generate Bessel beam. The experimental results showed that carbonization of SiC surface accelerates thermal ablation of the materials with fluence under the lattice melting threshold. Especially, pattern of side lobes with small fluence was formed by irradiation of Bessel beam. The pattern disturbed penetration of wavefronts through materials. Implementation of water environment was not effective to suppress carbonization and had slight effect on improvement of drilling quality. For this reason, deep drilling with small entrance was not achieved using Bessel beam. Irradiation of 1064 nm Gaussian beam with large fluence led to formation of critical amount of re-solidified silicon due to the large optical penetration depth. Carbonization and silicon formation had a significant effect on unique fluence dependence of drilling depth. Absorption mechanism was studied as well to discuss effect of wavelength on processing characteristics.
Multimode laser beam analyzer instrument using electrically programmable optics.

PubMed

Marraccini, Philip J; Riza, Nabeel A

2011-12-01

Presented is a novel design of a multimode laser beam analyzer using a digital micromirror device (DMD) and an electronically controlled variable focus lens (ECVFL) that serve as the digital and analog agile optics, respectively. The proposed analyzer is a broadband laser characterization instrument that uses the agile optics to smartly direct light to the required point photodetectors to enable beam measurements of minimum beam waist size, minimum waist location, divergence, and the beam propagation parameter M(2). Experimental results successfully demonstrate these measurements for a 500 mW multimode test laser beam with a wavelength of 532 nm. The minimum beam waist, divergence, and M(2) experimental results for the test laser are found to be 257.61 μm, 2.103 mrad, 1.600 and 326.67 μm, 2.682 mrad, 2.587 for the vertical and horizontal directions, respectively. These measurements are compared to a traditional scan method and the results of the beam waist are found to be within error tolerance of the demonstrated instrument.
Micro-scanning mirrors for high-power laser applications in laser surgery

NASA Astrophysics Data System (ADS)

Sandner, Thilo; Kimme, Simon; Grasshoff, Thomas; Todt, Ulrich; Graf, Alexander; Tulea, Cristian; Lenenbach, Achim; Schenk, Harald

2014-03-01

We present two novel micro scanning mirrors with large aperture and HR dielectric coatings suitable for high power laser applications in a miniaturized laser-surgical instrument for neurosurgery to cut skull tissue. An electrostatic driven 2D-raster scanning mirror with 5x7.1mm aperture is used for dynamic steering of a ps-laser beam of the laser cutting process. A second magnetic 2D-beam steering mirror enables a static beam correction of a hand guided laser instrument. Optimizations of a magnetic gimbal micro mirror with 6 mm x 8 mm mirror plate are presented; here static deflections of 3° were reached. Both MEMS devices were successfully tested with a high power ps-laser at 532nm up to 20W average laser power.
Photo-oxidation-modulated refractive index in Bi2Te3 thin films

NASA Astrophysics Data System (ADS)

Yue, Zengji; Chen, Qinjun; Sahu, Amit; Wang, Xiaolin; Gu, Min

2017-12-01

We report on an 800 nm femtosecond laser beam induced giant refractive index modulation and enhancement of near-infrared transparency in topological insulator material Bi2Te3 thin films. An ultrahigh refractive index of up to 5.9 was observed in the Bi2Te3 thin film in near-infrared frequency. The refractive index dramatically decreases by a factor of ~3 by an exposure to the 800 nm femtosecond laser beam. Simultaneously, the transmittance of the Bi2Te3 thin films markedly increases to ~96% in the near-infrared frequency. The Raman spectra provides strong evidences that the observed both refractive index modulation and transparency enhancement result from laser beam induced photooxidation effects in the Bi2Te3 thin films. The Bi2Te3 compound transfers into Bi2O3 and TeO2 under the laser beam illumination. These experimental results pave the way towards the design of various optical devices, such as near-infrared flat lenses, waveguide and holograms, based on topological insulator materials.
Single-beam Denisyuk holograms recording with pulsed 30Hz RGB laser

NASA Astrophysics Data System (ADS)

Zacharovas, Stanislovas; Bakanas, RamÅ«nas; Stankauskas, Algimantas

2016-03-01

It is well known fact that holograms can be recorded either by continuous wave (CW) laser, or by single pulse coming from pulsed laser. However, multi-pulse or multiple-exposure holograms were used only in interferometry as well as for information storage. We have used Geola's single longitudinal mode pulsed RGB laser to record Denisyuk type holograms. We successfully recorded objects situated at the distance of more than 30cm, employing the multi-pulse working regime of the laser. To record Denisyuk hologram we have used 50 ns duration 440, 660nm wavelength and 35ns duration 532nm wavelength laser pulses at the repetition rate of 30Hz. As photosensitive medium we have used Slavich-Geola PFG-03C glass photoplate. Radiations with different wavelengths were mixed into "white" beam, collimated and directed onto the photoplate. For further objects illumination an additional flat silver coated mirror was used.
Diode-laser-based therapy device

NASA Astrophysics Data System (ADS)

Udrea, Mircea V.; Nica, Adriana S.; Florian, Mariana; Poenaru, Daniela; Udrea, Gabriela; Lungeanu, Mihaela; Sporea, Dan G.; Vasiliu, Virgil V.; Vieru, Roxana

2004-10-01

A new therapy laser device is presented. The device consists of a central unit and different types of laser probes. The laser probe model SL7-650 delivers seven red (650 nm), 5 mW diode lasers convergent beams. The beams converge at about 30 cm in front of the laser probe and the irradiated area might be varied by simple displacement of the laser probe with respect to the target. The laser probe SL1-808 emits single infrared laser beam up to 500 mW. The efficiency of the use of this device in physiotherapy, and rheumatology, has been put into evidence after years of testing. Dermatology and microsurgery are users of infrared powerful laser probes. The device has successfully passed technical and clinical tests in order to be certified. The laser device design and some medical results are given.
High-power narrow-linewidth quasi-CW diode-pumped TEM00 1064 nm Nd:YAG ring laser.

PubMed

Liu, Yuan; Wang, Bao-shan; Xie, Shi-yong; Bo, Yong; Wang, Peng-yuan; Zuo, Jun-wei; Xu, Yi-ting; Xu, Jia-lin; Peng, Qin-jun; Cui, Da-fu; Xu, Zu-yan

2012-04-01

We demonstrated a high average power, narrow-linewidth, quasi-CW diode-pumped Nd:YAG 1064 nm laser with near-diffraction-limited beam quality. A symmetrical three-mirror ring cavity with unidirectional operation elements and an etalon was employed to realize the narrow-linewidth laser output. Two highly efficient laser modules and a 90° quartz rotator for birefringence compensation were used for the high output power. The maximum average output power of 62.5 W with the beam quality factor M(2) of 1.15 was achieved under a pump power of 216 W at a repetition rate of 500 Hz, corresponding to the optical-to-optical conversion efficiency of 28.9%. The linewidth of the laser at the maximum output power was measured to be less than 0.2 GHz.
Micro particle launcher/cleaner based on optical trapping technology.

PubMed

Liu, Zhihai; Liang, Peibo; Zhang, Yu; Zhang, Yaxun; Zhao, Enming; Yang, Jun; Yuan, Libo

2015-04-06

Efficient and controllable launching function of an optical tweezers is a challenging task. We present and demonstrate a novel single fiber optical tweezers which can trap and launch (clean) a target polystyrene (PS) microsphere (diameter~10μm) with independent control by using two wavelengths beams: 980nm and 1480nm. We employ 980nm laser beam to trap the target PS microsphere by molding the fiber tip into a special tapered-shape; and we employ 1480nm laser beam to launch the trapped PS microsphere with a certain velocity by using the thermophoresis force generated from the thermal effect due to the high absorption of the 1480nm laser beams in water. When the launching force is smaller than the trapping force, the PS microsphere will be trapped near the fiber tip, and the launching force will blow away other PS microspheres in the workspace realizing the cleaning function; When the launching force is larger than the trapping force, the trapped PS microsphere will be launched away from the fiber tip with a certain velocity and towards a certain direction, realizing the launching function. The launching velocity, acceleration and the distance can be measured by detecting the interference signals generated from the PS microsphere surface and the fiber tip end-face. This PS microsphere launching and cleaning functions expanded new features of single fiber optical tweezers, providing for the possibility of more practical applications in the micro manipulation research fields.
Wavelength locking of single emitters and multi-emitter modules: simulation and experiments

NASA Astrophysics Data System (ADS)

Yanson, Dan; Rappaport, Noam; Peleg, Ophir; Berk, Yuri; Dahan, Nir; Klumel, Genady; Baskin, Ilya; Levy, Moshe

2016-03-01

Wavelength-stabilized high-brightness single emitters are commonly used in fiber-coupled laser diode modules for pumping Yb-doped lasers at 976 nm, and Nd-doped ones at 808 nm. We investigate the spectral behavior of single emitters under wavelength-selective feedback from a volume Bragg (or hologram) grating (VBG) in a multi-emitter module. By integrating a full VBG model as a multi-layer thin film structure with commercial raytracing software, we simulated wavelength locking conditions as a function of beam divergence and angular alignment tolerances. Good correlation between the simulated VBG feedback strength and experimentally measured locking ranges, in both VBG misalignment angle and laser temperature, is demonstrated. The challenges of assembling multi-emitter modules based on beam-stacked optical architectures are specifically addressed, where the wavelength locking conditions must be achieved simultaneously with high fiber coupling efficiency for each emitter in the module. It is shown that angular misorientation between fast and slow-axis collimating optics can have a dramatic effect on the spectral and power performance of the module. We report the development of our NEON-S wavelength-stabilized fiber laser pump module, which uses a VBG to provide wavelength-selective optical feedback in the collimated portion of the beam. Powered by our purpose-developed high-brightness single emitters, the module delivers 47 W output at 11 A from an 0.15 NA fiber and a 0.3 nm linewidth at 976 nm. Preliminary wavelength-locking results at 808 nm are also presented.
Picosecond laser with 11 W output power at 1342 nm based on composite multiple doping level Nd:YVO4 crystal

NASA Astrophysics Data System (ADS)

Rodin, Aleksej M.; Grishin, Mikhail; Michailovas, Andrejus

2016-01-01

We report results of design and optimization of high average output power picosecond and nanosecond laser operating at 1342 nm wavelength. Developed for selective micromachining, this DPSS laser is comprised of master oscillator, regenerative amplifier and output pulse control module. Passively mode-locked by means of semiconductor saturable absorber mirror and pumped with 808 nm wavelength Nd:YVO4 master oscillator emits 12.5 ps pulses at repetition rate of 55 MHz with average output power of ∼100 mW. The four-pass confocal delay line forms a longest part of the oscillator cavity in order to suppress thermo-mechanical misalignment. Picked from the train seed pulses were injected to the cavity of regenerative amplifier based on composite Nd:YVO4 crystal with diffusion-bonded segments of multiple Nd doping concentration end-pumped at 880 nm wavelength. Laser produces pulses of ∼13 ps duration at 300 kHz repetition rate with average output power of 11 W and nearly diffraction limited beam quality of M2∼1.03. Attained high peak power ∼2.8 MW facilitates conversion to the 2nd, 3rd and 6th harmonics at 671 nm, 447 nm and 224 nm wavelengths with 80%, 50% and 15% efficiency respectively. Without seeding the regenerative amplifier transforms to electro-optically cavity-dumped Q-switched laser providing 10 ns output pulses at high repetition rates with beam propagation factor of M2∼1.06.
Solid-state Yb : YAG amplifier pumped by a single-mode laser at 920 nm

NASA Astrophysics Data System (ADS)

Obronov, I. V.; Demkin, A. S.; Myasnikov, D. V.

2018-03-01

An optical amplifier scheme for ultrashort 1030-nm pulses is proposed based on an Yb : YAG crystal with axial pumping by a transverse single-mode laser at a wavelength of 920 nm. A small-signal gain up to 40 dB per pass with a high output beam quality is demonstrated. The maximum average power is 14 W with a slope efficiency exceeding 50%.
Long Coherence Length 193 nm Laser for High-Resolution Nano-Fabrication

DTIC Science & Technology

2008-06-27

in the non-linear optical up-converter, as well as specifying their interaction lengths, phase -matching angles, coatings, temperatures of operation...when optical path differences between interfering beams become comparable to the temporal coherence length of the source, the fringe contrast diminishes...switched, intracavity frequency doubled Nd:YAG laser drives an optical parametric oscillator (OPO) running at 710 nm. A portion of the 532 nm light
Recent development on high-power tandem-pumped fiber laser

NASA Astrophysics Data System (ADS)

Zhou, Pu; Xiao, Hu; Leng, Jinyong; Zhang, Hanwei; Xu, Jiangmin; Wu, Jian

2016-11-01

High power fiber laser is attracting more and more attention due to its advantage in excellent beam quality, high electricto- optical conversion efficiency and compact system configuration. Power scaling of fiber laser is challenged by the brightness of pump source, nonlinear effect, modal instability and so on. Pumping active fiber by using high-brightness fiber laser instead of common laser diode may be the solution for the brightness limitation. In this paper, we will present the recent development of various kinds of high power fiber laser based on tandem pumping scheme. According to the absorption property of Ytterbium-doped fiber, Thulium-doped fiber and Holmium-doped fiber, we have theoretically studied the fiber lasers that operate at 1018 nm, 1178 nm and 1150 nm, respectively in detail. Consequently, according to the numerical results we have optimized the fiber laser system design, and we have achieved (1) 500 watt level 1018nm Ytterbium-doped fiber laser (2) 100 watt level 1150 nm fiber laser and 100 watt level random fiber laser (3) 30 watt 1178 nm Ytterbium-doped fiber laser, 200 watt-level random fiber laser. All of the above-mentioned are the record power for the corresponded type of fiber laser to the best of our knowledge. By using the high-brightness fiber laser operate at 1018 nm, 1178 nm and 1150 nm that we have developed, we have achieved the following high power fiber laser (1) 3.5 kW 1090 nm Ytterbium-doped fiber amplifier (2) 100 watt level Thulium-doped fiber laser and (3) 50 watt level Holmium -doped fiber laser.
Cladding-pumped ytterbium-doped fiber laser with radially polarized output.

PubMed

Lin, Di; Daniel, J M O; Gecevičius, M; Beresna, M; Kazansky, P G; Clarkson, W A

2014-09-15

A simple technique for directly generating a radially polarized output beam from a cladding-pumped ytterbium-doped fiber laser is reported. Our approach is based on the use of a nanograting spatially variant waveplate as an intracavity polarization-controlling element. The laser yielded ~32 W of output power (limited by available pump power) with a radially polarized TM (01)-mode output beam at 1040 nm with a corresponding slope efficiency of 66% and a polarization purity of 95%. The beam-propagation factor (M(2)) was measured to be ~1.9-2.1.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, C.T.

Linear and nonlinear photochemistries of 1,4-diazabicyclo(2.2.2)octane (DABCO) are investigated at room temperature by using ArF (193 nm) and KrF (248 nm) lasers. With an unfocused beam geometry, DABCO vapor displays a strong fluorescence when excited at 248 nm, but it shows no detectable emission with 193-nm excitation. The linear photochemistry quantum yield for DABCO is determined as phi/sub p/(248nm) approx. 0.1 and phi/sub p/(193 nm) approx. 0.3. The main stable photochemical products are analyzed as C/sub 2/H/sub 4/ and C/sub 2/H/sub 2/ for 248- and 193-nm excitation, respectively. When focused beam excitation is used, both ArF and KrF lasers dissociatemore » DABCO molecules and give three strong radical emissions of CN*(B vector /sup 2/..sigma.. ..-->.. X vector /sup 2/ ..sigma../sup +/), CH*(A vector /sup 2/..delta.. ..-->.. X vector /sup 2/II), and C/sub 2/*(D vector /sup 3/II/sub g/ ..-->.. a vector /sup 3/II/sub u/). The time behavior, the laser power dependence, and the sample pressure dependence of these emissive radicals are examined. The possible mechanisms for the Rydberg state photochemistry of DABCO are discussed.« less

Diode-side-pumped continuous wave Nd³⁺ : YVO₄ self-Raman laser at 1176 nm.

PubMed

Kores, Cristine Calil; Jakutis-Neto, Jonas; Geskus, Dimitri; Pask, Helen M; Wetter, Niklaus U

2015-08-01

Here we report, to the best of our knowledge, the first diode-side-pumped continuous wave (cw) Nd3+:YVO4 self-Raman laser operating at 1176 nm. The compact cavity design is based on the total internal reflection of the laser beam at the pumped side of the Nd3+:YVO4 crystal. Configurations with a single bounce and a double bounce of the laser beam at the pumped faced have been characterized, providing a quasi-cw peak output power of more than 8 W (multimode) with an optical conversion efficiency of 11.5% and 3.7 W (TEM00) having an optical conversion efficiency of 5.4%, respectively. Cw output power of 1.8 W has been demonstrated.
Laser controlled deposition of metal microstructures via nondiffracting Bessel beam illumination

NASA Astrophysics Data System (ADS)

Drampyan, Rafael; Leonov, Nikita; Vartanyan, Tigran

2016-04-01

The technique of the laser controlled deposition of sodium and rubidium deposits on the sapphire substrate is presented. The metals were deposited on the clean sapphire substrate from the vapor phase contained in the evacuated and sealed cell. We use an axicon to produce a non-diffracting Bessel beam out of the beam got from the cw diode laser with 200 mW power at the wavelength of 532 nm. After 30 minutes of the laser-controlled deposition the substrates were examined in the optical microscope. The obtained metal deposits form the sharp-cut circles with the pitch of 10 μm, coincident with the tens of dark rings of the Bessel beam. Reduction of the laser power leads to the build up of the continuous metal film over the whole substrate.
High Efficiency, Room Temperature Mid-Infrared Semiconductor Laser Development for IR Countermeasures

DTIC Science & Technology

2009-05-01

voltage (I-V) characteristics of several infrared LEDs, including a type-II W-well laser grown by Molecular Beam Epitaxy at Naval Research Laboratory...Injection Cavity (OPIC) lasers includes >4 um emission from a broadband laser and the measurement of spatial and temporal beam profiles. From August 2006...argon) at 15 mTorr, 400W ICP, and 70W RIE power, with an etch rate of 300 nm/min. Epitaxial ZnO layers were plasma etched using BCl3/SF0gas mixtures
Efficient frequency conversion by stimulated Raman scattering in a sodium nitrate aqueous solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganot, Yuval, E-mail: yuvalga@sapir.ac.il, E-mail: ibar@bgu.ac.il; Bar, Ilana, E-mail: yuvalga@sapir.ac.il, E-mail: ibar@bgu.ac.il

2015-09-28

Frequency conversion of laser beams, based on stimulated Raman scattering (SRS) is an appealing technique for generating radiation at new wavelengths. Here, we investigated experimentally the SRS due to a single pass of a collimated frequency-doubled Nd:YAG laser beam (532 nm) through a saturated aqueous solution of sodium nitrate (NaNO{sub 3}), filling a 50 cm long cell. These experiments resulted in simultaneous generation of 1st (564 nm) and 2nd (599 nm) Stokes beams, corresponding to the symmetric stretching mode of the nitrate ion, ν{sub 1}(NO{sub 3}{sup −}), with 40 and 12 mJ/pulse maximal converted energies, equivalent to 12% and 4% efficiencies, respectively, for a 340more » mJ/pulse pump energy. The results indicate that the pump and SRS beams were thermally defocused and that four-wave mixing was responsible for the second order Stokes process onset.« less
Apker Award Talk: Atomic Beam Measurement of the Indium 6p1 / 2 Scalar Polarizability

NASA Astrophysics Data System (ADS)

Augenbraun, Benjamin

2016-05-01

We report on the first measurement of the scalar polarizability of the indium 6p1 / 2 -excited state using two-step laser spectroscopy in an atomic beam. This is one in a series of precise atomic structure measurements by the Majumder lab at Williams College, which serve as stringent tests of abinitio calculation methods for three-valence-electron systems. We stabilize a laser to the indium 5p1 / 2 --> 6s1 / 2 410 nm transition and scan a second laser across the 6s1 / 2 --> 6p1 / 2 1343 nm transition. The two laser beams are overlapped and interact transversely with a collimated atomic beam of indium. Two-tone FM spectroscopy allows us to observe the small (< 1 part in 103) IR absorption, and characteristic sideband features in the RF-demodulated lineshape provide built-in frequency calibration. Application of DC electric fields up to 20 kV/cm give rise to Stark shifts of order 100 MHz. Because our group has previously measured the difference in polarizabilities within the 410 nm transition, we can determine the 6p1 / 2 polarizability with no loss of precision. Preliminary results are in excellent agreement with recent theoretical calculations and can be used to infer accurate values for the indium 6 p - 5 d matrix elements.
Highly-efficient multi-watt Yb:CaLnAlO4 microchip lasers

NASA Astrophysics Data System (ADS)

Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Xu, Xiaodong; Xu, Jun; Yumashev, Konstantin; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc; Major, Arkady

2017-02-01

Tetragonal rare-earth calcium aluminates, CaLnAlO4 where Ln = Gd or Y (CALGO and CALYO, respectively), are attractive laser crystal hosts due to their locally disordered structure and high thermal conductivity. In the present work, we report on highly-efficient power-scalable microchip lasers based on 8 at.% Yb:CALGO and 3 at.% Yb:CALYO crystals grown by the Czochralski method. Pumped by an InGaAs laser diode at 978 nm, the 6 mm-long Yb:CALGO microchip laser generated 7.79 W at 1057-1065 nm with a slope efficiency of η = 84% (with respect to the absorbed pump power) and an optical-to-optical efficiency of ηopt = 49%. The 3 mm-long Yb:CALYO microchip laser generated 5.06 W at 1048-1056 nm corresponding to η = 91% and ηopt = 32%. Both lasers produced linearly polarized output (σ- polarization) with an almost circular beam profile and beam quality factors M2 x,y <1.1. The output performance of the developed lasers was modeled yielding a loss coefficient as low as 0.004-0.007 cm-1. The results indicate that the Yb3+- doped calcium aluminates are very promising candidates for high-peak-power passively Q-switched microchip lasers.
Thermal effects in laser-assisted embryo hatching

NASA Astrophysics Data System (ADS)

Douglas-Hamilton, Diarmaid H.; Conia, Jerome D.

2000-08-01

Diode lasers [(lambda) equals 1480 nm] are used with in-vitro fertilization [IVF] as a promoter of embryo hatching. A focused laser beam is applied in vitro to form a channel in the zona pellucida (shell) of the pre-embryo. After transfer into the uterus, the embryo hatches: it extrudes itself through the channel and implants into the uterine wall. Laser-assisted hatching can result in improving implantation and pregnancy success rates. We present examples of zone pellucida ablation using animal models. In using the laser it is vital not to damage pre-embryo cells, e.g. by overheating. In order to define safe regimes we have derived some thermal side-effects of zona pellucida removal. The temperature profile in the beam and vicinity is predicted as function of laser pulse duration and power. In a crossed-beam experiment a HeNe laser probe detects the temperature-induced change in refractive index. We find that the diode laser beam produces superheated water approaching 200 C on the beam axis. Thermal histories during and following the laser pulse are given for regions in the neighborhood of the beam. We conclude that an optimum regime exists with pulse duration
Relationship between 578-nm (copper vapor) laser beam geometry and heat distribution within biological tissues

NASA Astrophysics Data System (ADS)

Ilyasov, Ildar K.; Prikhodko, Constantin V.; Nevorotin, Alexey J.

1995-01-01

Monte Carlo (MC) simulation model and the thermoindicative tissue phantom were applied for evaluation of a depth of tissue necrosis (DTN) as a result of quasi-cw copper vapor laser (578 nm) irradiation. It has been shown that incident light focusing angle is essential for DTN. In particular, there was a significant rise in DTN parallel to elevation of this angle up to +20 degree(s)C and +5 degree(s)C for both the MC simulation and tissue phantom models, respectively, with no further increase in the necrosis depth above these angles. It is to be noted that the relationship between focusing angles and DTN values was apparently stronger for the real target compared to the MC-derived hypothetical one. To what extent these date are applicable for medical practice can be evaluated in animal models which would simulate laser-assisted therapy for PWS or related dermatologic lesions with converged 578 nm laser beams.
Pointing Reference Scheme for Free-Space Optical Communications Systems

NASA Technical Reports Server (NTRS)

Wright, Malcolm; Ortiz, Gerardo; Jeganathan, Muthu

2006-01-01

A scheme is proposed for referencing the propagation direction of the transmit laser signal in pointing a free-space optical communications terminal. This recently developed scheme enables the use of low-cost, commercial silicon-based sensors for tracking the direction of the transmit laser, regardless of the transmit wavelength. Compared with previous methods, the scheme offers some advantages of less mechanical and optical complexity and avoids expensive and exotic sensor technologies. In free-space optical communications, the transmit beam must be accurately pointed toward the receiver in order to maintain the communication link. The current approaches to achieve this function call for part of the transmit beam to be split off and projected onto an optical sensor used to infer the pointed direction. This requires that the optical sensor be sensitive to the wavelength of the transmit laser. If a different transmit wavelength is desired, for example to obtain a source capable of higher data rates, this can become quite impractical because of the unavailability or inefficiency of sensors at these wavelengths. The innovation proposed here decouples this requirement by allowing any transmit wavelength to be used with any sensor. We have applied this idea to a particular system that transmits at the standard telecommunication wavelength of 1,550 nm and uses a silicon-based sensor, sensitive from 0.5 to 1.0 micrometers, to determine the pointing direction. The scheme shown in the figure involves integrating a low-power 980-nm reference or boresight laser beam coupled to the 1,550-nm transmit beam via a wavelength-division-multiplexed fiber coupler. Both of these signals propagate through the optical fiber where they achieve an extremely high level of co-alignment before they are launched into the telescope. The telescope uses a dichroic beam splitter to reflect the 980- nm beam onto the silicon image sensor (a quad detector, charge-coupled device, or active-pixel-sensor array) while the 1,550- nm signal beam is transmitted through the optical assembly toward the remotely located receiver. Since the 980-nm reference signal originates from the same single-mode fiber-coupled source as the transmit signal, its position on the sensor is used to accurately determine the propagation direction of the transmit signal. The optics are considerably simpler in the proposed scheme due to the use of a single aperture for transmitting and receiving. Moreover, the issue of mechanical misalignment does not arise because the reference signal and transmitted laser beams are inherently co-aligned. The beam quality of the 980-nm reference signal used for tracking is required to be circularly symmetric and stable at the tracking-plane sensor array in order to minimize error in the centroiding algorithm of the pointing system. However, since the transmit signal is delivered through a fiber that supports a single mode at 1,550 nm, propagation of higher order 980-nm modes is possible. Preliminary analysis shows that the overall mode profile is dominated by the fundamental mode, giving a near symmetric profile. The instability of the mode was also measured and found to be negligible in comparison to the other error contributions in the centroid position on the sensor array.
High Average Power Diode Pumped Solid State Lasers: Power Scaling With High Spectral and Spatial Coherence

DTIC Science & Technology

2009-03-30

seeded with 15 W of single-frequency laser light at 1064 nm and cladding -pumped of 700 W in the forward direction and 300 W in the opposite direction...57-W single-mode phosphate fiber laser Our early studies of phosphate fiber lasers taught us that adding an air-hole to the inner cladding and... cladding -pumped with a fiber-coupled laser diode at 977 nm through a dichroic beam splitter placed on the OC side. The fiber ends were cooled using the
Laser annealing and in situ absorption measurement of float glass implanted with Ag ions

NASA Astrophysics Data System (ADS)

Okur, I.; Townsend, P. D.

2004-08-01

In this paper in situ pulsed laser annealing and absorption measurements results of Ag-implanted float glass are reported. A Nd:YAG laser harmonic at 266 nm was used to anneal the target area by coupling energy to the glass host, whilst an argon laser at 488 nm was used as a probe beam of changes in nanoparticle size. The equilibrium conditions show a third order power dependence on the laser pulse energy, which is attributed to the volume in which ion migration can occur during excitation.
Final Report for Contract N00014-86-C-0598 (Thermo Electron Technologies Corporation)

DTIC Science & Technology

1989-12-28

At least 20 A/cm2 were observed at 193 nm. 248 nm (KrF) and 308 (XeCl). Beam brightness appears to be a minimum of 4 x 105 A/cm 2 -rad 2 at 248 nm...governed by the envelope equation3, d2r K b 0 dz (4) For a weakly relativistic beam. e J o r0 2 2 Co 0Mo (yac) 3 (5) where Jo is the beam current...correspond to laser wavotengths of the present study, preliminary measurement for ArF given by x .1 pattern ot spots on the phosphor screen for 248 nm
Laser scattering induced holograms in lithium niobate. [observation of diffraction cones

NASA Technical Reports Server (NTRS)

Magnusson, R.; Gaylord, T. K.

1974-01-01

A 3.0-mm thick poled single crystal of lithium niobate doped with 0.1 mole% iron was exposed to a single beam and then to two intersecting beams of an argon ion laser operating at 515-nm wavelength. Laser scattering induced holograms were thus written and analyzed. The presence of diffraction cones was observed and is shown to result from the internally recorded interference pattern resulting from the interference of the original incident laser beam with light scattered from material inhomogeneities. This phenomenon is analyzed using Ewald sphere construction techniques which reveal the geometrical relationships existing for the diffraction cones.
High energy 523 nm ND:YLF pulsed slab laser with novel pump beam waveguide design

NASA Astrophysics Data System (ADS)

Yang, Qi; Zhu, Xiaolei; Ma, Jian; Lu, Tingting; Ma, Xiuhua; Chen, Weibiao

2015-11-01

A laser diode pumped Nd:YLF master oscillator power amplifier (MOPA) green laser system with high pulse energy and high stable output is demonstrated. At a repetition rate of 50 Hz, 840 mJ pulse energy, 9.1 ns pulse width of 1047 nm infrared laser emitting is obtained from the MOPA system. The corresponding peak power is 93 MW. Extra-cavity frequency doubling with a LiB3O5 crystal, pulse energy of 520 mJ at 523 nm wavelength is achieved. The frequency conversion efficiency reaches up to 62%. The output pulse energy instability of the laser system is less than 0.6% for one hour.
Overview of laser systems for the Orion facility at the AWE.

PubMed

Hopps, Nicholas; Danson, Colin; Duffield, Stuart; Egan, David; Elsmere, Stephen; Girling, Mark; Harvey, Ewan; Hillier, David; Norman, Michael; Parker, Stefan; Treadwell, Paul; Winter, David; Bett, Thomas

2013-05-20

The commissioning of the Orion laser facility at the Atomic Weapons Establishment (AWE) in the UK has recently been completed. The facility is a twelve beam Nd:glass-based system for studying high energy density physics. It consists of ten frequency-tripled beam-lines operating with nanosecond pulses, synchronized with two beam-lines with subpicosecond pulses, each capable of delivering 500 J to target. One of the short pulse beams has the option of frequency doubling, at reduced aperture, to yield up to 100 J at 527 nm in a subpicosecond pulse with high temporal contrast. An extensive array of target diagnostics is provided. This article describes the laser design and commissioning and presents key performance data of the facility's laser systems.
Laser ablation of single-crystalline silicon by radiation of pulsed frequency-selective fiber laser

NASA Astrophysics Data System (ADS)

Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

2015-07-01

We have studied the process of destruction of the surface of a single-crystalline silicon wafer scanned by the beam of a pulsed ytterbium-doped fiber laser radiation with a wavelength of λ = 1062 nm. It is established that the laser ablation can proceed without melting of silicon and the formation of a plasma plume. Under certain parameters of the process (radiation power, beam scan velocity, and beam overlap density), pronounced oxidation of silicon microparticles with the formation of a characteristic loose layer of fine powdered silicon dioxide has been observed for the first time. The range of lasing and beam scanning regimes in which the growth of SiO2 layer takes place is determined.
Laser resonance ionization spectroscopy of antimony

NASA Astrophysics Data System (ADS)

Li, R.; Lassen, J.; Ruczkowski, J.; Teigelhöfer, A.; Bricault, P.

2017-02-01

The resonant ionization laser ion source is an element selective, efficient and versatile ion source to generate radioactive ion beams at on-line mass separator facilities. For some elements with complex atomic structures and incomplete spectroscopic data, laser spectroscopic investigations are required for ionization scheme development. Laser resonance ionization spectroscopy using Ti:Sa lasers has been performed on antimony (Sb) at TRIUMF's off-line laser ion source test stand. Laser light of 230.217 nm (vacuum wavelength) as the first excitation step and light from a frequency-doubled Nd:YVO4 laser (532 nm) as the nonresonant ionization step allowed to search for suitable second excitation steps by continuous wavelength scans from 720 nm to 920 nm across the wavelength tuning range of a grating-tuned Ti:Sa laser. Upon the identification of efficient SES, the third excitation steps for resonance ionization were investigated by laser scans across Rydberg states, the ionization potential and autoionizing states. One Rydberg state and six AI states were found to be well suitable for efficient resonance ionization.
Dual sub-picosecond and sub-nanosecond laser system

NASA Astrophysics Data System (ADS)

Xie, Xinglong; Liu, Fengqiao; Yang, Jingxin; Yang, Xin; Li, Meirong; Xue, Zhiling; Gao, Qi; Guan, Fuyi; Zhang, Weiqing; Huang, Guanlong; Zhuang, Yifei; Han, Aimei; Lin, Zunqi

2003-11-01

A high power laser system delivering a 20-TW, 0.5 - 0.8 ps ultra-short laser pulse and a 20-J, 500-ps long pulse simultaneously in one shot is completed. This two-beam laser operates at the wavelength of 1053 nm and uses Nd doped glass as the gain media of the main amplification chain. The chirped-pulse amplification (CPA) technology is used to compress the stretched laser pulse. After compression, the ultrashort laser pulse is measured: energy above 16.0 J, S/N contrast ratio ~ 10^(5) : 1, filling factor ~>52.7%. Another long pulse beam is a non-compressed chirped laser pulse, which is measured: energy ~ 20 J, pulse duration 500 ps. The two beams are directed onto the target surface at an angle of 15°.
New scanner fiber optic delivery system for laser phototherapy in the treatment of neonatal jaundice

NASA Astrophysics Data System (ADS)

Hamza, Mostafa; Hamza, Mohammad S. E.

1995-05-01

The authors have introduced laser phototherapy for the treatment of neonatal jaundice. Clinical trials have demonstrated its high efficacy compared to the conventionally used fluorescent phototherapy. In this paper a new modification to laser irradiation in phototherapy can be achieved by scanning the laser output beam in the selected wavelength of irradiation (488 nm) through a fiberoptic bundle which irradiate the skin of the baby. Scanning of the laser beam provides intermittent irradiation at high frequency, which can provide the same therapeutic efficacy with almost half the power of laser irradiation.
A high resolution hand-held focused beam profiler

NASA Astrophysics Data System (ADS)

Zapata-Farfan, J.; Garduño-Mejía, J.; Rosete-Aguilar, M.; Ascanio, G.; Román-Moreno, C. J.

2017-05-01

The shape of a beam is important in any laser application and depending on the final implementation, there exists a preferred one which is defined by the irradiance distribution.1 The energy distribution (or laser beam profile) is an important parameter in a focused beam, for instance, in laser cut industry, where the beam shape determines the quality of the cut. In terms of alignment and focusing, the energy distribution also plays an important role since the system must be configured in order to reduce the aberration effects and achieve the highest intensity. Nowadays a beam profiler is used in both industry and research laboratories with the aim to characterize laser beams used in free-space communications, focusing and welding, among other systems. The purpose of the profile analyzers is to know the main parameters of the beam, to control its characteristics as uniformity, shape and beam size as a guide to align the focusing system. In this work is presented a high resolution hand-held and compact design of a beam profiler capable to measure at the focal plane, with covered range from 400 nm to 1000 nm. The detection is reached with a CMOS sensor sized in 3673.6 μm x 2738.4 μm which acquire a snap shot of the previously attenuated focused beam to avoid the sensor damage, the result is an image of beam intensity distribution, which is digitally processed with a RaspberryTMmodule gathering significant parameters such as beam waist, centroid, uniformity and also some aberrations. The profiler resolution is 1.4 μm and was probed and validated in three different focusing systems. The spot sizes measurements were compared with the Foucault knife-edge test.

Micro-scale patterning of indium tin oxide film by spatially modulated pulsed Nd:YAG laser beam

NASA Astrophysics Data System (ADS)

Lee, Jinsoo; Kim, Seongsu; Lee, Myeongkyu

2012-09-01

Here we demonstrate that indium tin oxide (ITO) films deposited on glass can be directly patterned by a spatially -modulated pulsed Nd-YAG laser beam (wavelength = 1064 nm, pulse width = 6 ns) incident onto the film. This method utilizes a pulsed laser-induced thermo-elastic force exerting on the film which plays a role to detach it from the substrate. Sharp-edged clean patterns with feature size as small as 4 μm could be obtained. The threshold pulse energy density for patterning was estimated to be ˜0.8 J/cm2 for 150 nm-thick ITO film, making it possible to pattern over one square centimeter by a single pulse with energy of 850 mJ. Not only being free from photoresist and chemical etching steps, the presented method can also provide much higher throughput than the tradition photoablation process utilizing a tightly focused beam.
Purification of Nanoscale Electron-Beam-Induced Platinum Deposits via a Pulsed Laser-Induced Oxidation Reaction

DOE PAGES

Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon; ...

2014-11-05

Platinum–carbon deposits made via electron-beam-induced deposition were purified in this study via a pulsed laser-induced oxidation reaction and erosion of the amorphous carbon to form pure platinum. Purification proceeds from the top down and is likely catalytically facilitated via the evolving platinum layer. Thermal simulations suggest a temperature threshold of ~485 K, and the purification rate is a function of the PtC 5 thickness (80–360 nm) and laser pulse width (1–100 μs) in the ranges studied. The thickness dependence is attributed to the ~235 nm penetration depth of the PtC 5 composite at the laser wavelength, and the pulse-width dependencemore » is attributed to the increased temperatures achieved at longer pulse widths. Finally, remarkably fast purification is realized at cumulative laser exposure times of less than 1 s.« less
Purification of Nanoscale Electron-Beam-Induced Platinum Deposits via a Pulsed Laser-Induced Oxidation Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon

Platinum–carbon deposits made via electron-beam-induced deposition were purified in this study via a pulsed laser-induced oxidation reaction and erosion of the amorphous carbon to form pure platinum. Purification proceeds from the top down and is likely catalytically facilitated via the evolving platinum layer. Thermal simulations suggest a temperature threshold of ~485 K, and the purification rate is a function of the PtC 5 thickness (80–360 nm) and laser pulse width (1–100 μs) in the ranges studied. The thickness dependence is attributed to the ~235 nm penetration depth of the PtC 5 composite at the laser wavelength, and the pulse-width dependencemore » is attributed to the increased temperatures achieved at longer pulse widths. Finally, remarkably fast purification is realized at cumulative laser exposure times of less than 1 s.« less
Thermal effects in laser-assisted pre-embryo zona drilling

NASA Astrophysics Data System (ADS)

Douglas-Hamilton, Diarmaid H.; Conia, Jerome D.

2001-04-01

Diode lasers ((lambda) equals 1480 nm) are used with in vitro fertilization to dissect the zone pellucida (shell) of pre- embryos. A focused laser beam is applied in vitro to form a channel or trench in the zona pellucida. The procedure is used to facilitate biopsy or as a promoter of embryo hatching. We present examples and measurements of zona pellucida ablation using animal models. In using the laser it is vital not to damage pre-embryo cells, e.g., by overheating. In order to define safe regimes we have derived some thermal side effects of zona pellucida removal. The temperature profile in the beam and vicinity is predicted as function of laser pulse duration and power. In a crossed- beam experiment a HeNe laser probe is used to detect the temperature-induced change in the refractive index of an aqueous solution, and estimate local thermal gradient. We find that the diode laser beam produces superheated water approaching 200 degree(s)C on the beam axis. Thermal histories during and following the laser pulse are given for regions in the neighborhood of the beam. We conclude that an optimum regime exists with pulse duration
Evaluating the effects of a 532-nm fiber-based KTP laser on transoral laser surgery supplies.

PubMed

Coughlan, Carolyn A; Verma, Sunil P

2013-11-01

The KTP laser has become commonplace in transoral head and neck surgery. The interactions of this laser with commonly used supplies in transoral surgery have not been formally examined. This study evaluates the effects of the KTP laser on surgical supplies. Experimental study. The study was conducted in an empty operating room at a university-affiliated medical center. An Aura XP 532-nm KTP laser with a 600-nm fiber was used in pulsed and continuous modes. The beam was focused at the shaft and balloon of 3 "laser-safe" endotracheal tubes (ETTs), a polyvinyl chloride (PVC) ETT, and a Codman surgical patty. Time to penetrate was recorded. Results The KTP laser beam was unable to penetrate any of the laser-resistant ETTs. It did react with the black number markings on the PVC ETT by producing sparks but was unable to penetrate the shaft of the ETT. The KTP laser was nonreactive with all ETT cuffs except in 1 of 3 trials with the outer balloon cuff of a Rusch Lasertubus ETT when the laser was used in a continuous mode. The KTP laser caused the production of a flame upon contact with the blue radiopaque strip of the surgical patty, even when the patty was wet. This study demonstrates that a number of safe ETT options may be used during transoral laser microsurgery with a KTP laser. In addition, Codman surgical patties are shown to be a significant fire risk in KTP laser surgery.
36 W Q-switched Ho:YAG laser at 2097 nm pumped by a Tm fiber laser: evaluation of different Ho3+ doping concentrations

NASA Astrophysics Data System (ADS)

Antipov, O. L.; Eranov, I. D.; Kositsyn, R. I.

2017-01-01

A laser oscillator based on Ho:YAG crystal pumped by a Tm fiber laser with an acousto-optical Q-switch was optimized for maximum output power and pulse-to-pulse stability. Stable operation at 2097 nm in Q-switched mode is demonstrated, with pulse repetition rates from 10 to 30 kHz, and output power of 36 W (at 55 W of pump power at 1908 nm) in the good quality beam. The influence of Ho ion up-conversion and thermal lensing on the oscillation efficiency is discussed.
A High Power, Frequency Tunable Colloidal Quantum Dot (CdSe/ZnS) Laser

PubMed Central

Prasad, Saradh; Saleh AlHesseny, Hanan; AlSalhi, Mohamad S.; Devaraj, Durairaj; Masilamai, Vadivel

2017-01-01

Tunable lasers are essential for medical, engineering and basic science research studies. Most conventional solid-state lasers are capable of producing a few million laser shots, but limited to specific wavelengths, which are bulky and very expensive. Dye lasers are continuously tunable, but exhibit very poor chemical stability. As new tunable, efficient lasers are always in demand, one such laser is designed with various sized CdSe/ZnS quantum dots. They were used as a colloid in tetrahydrofuran to produce a fluorescent broadband emission from 520 nm to 630 nm. The second (532 nm) and/or third harmonic (355 nm) of the Nd:YAG laser (10 ns, 10 Hz) were used together as the pump source. In this study, different sized quantum dots were independently optically pumped to produce amplified spontaneous emission (ASE) with 4 nm to 7 nm of full width at half-maximum (FWHM), when the pump power and focusing were carefully optimized. The beam was directional with a 7 mrad divergence. Subsequently, these quantum dots were combined together, and the solution was placed in a resonator cavity to obtain a laser with a spectral width of 1 nm and tunable from 510 to 630 nm, with a conversion efficiency of about 0.1%. PMID:28336863
A High Power, Frequency Tunable Colloidal Quantum Dot (CdSe/ZnS) Laser.

PubMed

Prasad, Saradh; AlHesseny, Hanan Saleh; AlSalhi, Mohamad S; Devaraj, Durairaj; Masilamai, Vadivel

2017-01-30

Tunable lasers are essential for medical, engineering and basic science research studies. Most conventional solid-state lasers are capable of producing a few million laser shots, but limited to specific wavelengths, which are bulky and very expensive. Dye lasers are continuously tunable, but exhibit very poor chemical stability. As new tunable, efficient lasers are always in demand, one such laser is designed with various sized CdSe/ZnS quantum dots. They were used as a colloid in tetrahydrofuran to produce a fluorescent broadband emission from 520 nm to 630 nm. The second (532 nm) and/or third harmonic (355 nm) of the Nd:YAG laser (10 ns, 10 Hz) were used together as the pump source. In this study, different sized quantum dots were independently optically pumped to produce amplified spontaneous emission (ASE) with 4 nm to 7 nm of full width at half-maximum (FWHM), when the pump power and focusing were carefully optimized. The beam was directional with a 7 mrad divergence. Subsequently, these quantum dots were combined together, and the solution was placed in a resonator cavity to obtain a laser with a spectral width of 1 nm and tunable from 510 to 630 nm, with a conversion efficiency of about 0.1%.
Laser beam riding guided system principle and design research

NASA Astrophysics Data System (ADS)

Qu, Zhou; Jin, Yi; Xu, Zhou; Xing, Hao

2016-01-01

With the development of science and technology, precision-strike weapons has been considered to be important for winning victory in military field. Laser guidance is a major method to execute precision-strike in modern warfare. At present, the problems of primary stage of Laser guidance has been solved with endeavors of countries. Several technical aspects of laser-beam riding guided system have been mature, such as atmosphere penetration of laser beam, clutter inhibition on ground, laser irradiator, encoding and decoding of laser beam. Further, laser beam quality, equal output power and atmospheric transmission properties are qualified for warfare situation. Riding guidance instrument is a crucial element of Laser-beam riding guided system, and is also a vital element of airborne, vehicle-mounted and individual weapon. The optical system mainly consist of sighting module and laser-beam guided module. Photoelectric detector is the most important sensing device of seeker, and also the key to acquire the coordinate information of target space. Currently, in consideration of the 1.06 u m of wavelength applied in all the semi-active laser guided weapons systems, lithium drifting silicon photodiode which is sensitive to 1.06 u m of wavelength is used in photoelectric detector. Compared to Solid and gas laser, diode laser has many merits such as small volume, simple construction, light weight, long life, low lost and easy modulation. This article introduced the composition and operating principle of Laser-beam riding guided system based on 980 nm diode laser, and made a analysis of key technology; for instance, laser irradiator, modulating disk of component, laser zooming system. Through the use of laser diode, Laser-beam riding guided system is likely to have smaller shape and very light.
High power eye-safe Er3+:YVO4 laser diode-pumped at 976 nm and emitting at 1603 nm

NASA Astrophysics Data System (ADS)

Newburgh, G. A.; Dubinskii, M.

2016-02-01

We report on the performance of an eye-safe laser based on a Er:YVO4 single crystal, diode-pumped at 976 nm (4I15/2-->4I11/2 transition) and operating at 1603 nm (4I13/2-->4I15/2 transition) with good beam quality. A 10 mm long Er3+:YVO4 slab, cut with its c-axis perpendicular to the laser cavity axis, was pumped in σ-polarization and lased in π-polarization. The laser operated in a quasi-continuous wave (Q-CW) regime with nearly 9 W output power, and with a slope efficiency of about 39% with respect to absorbed power. This is believed to be the highest efficiency and highest power achieved from an Er3+:YVO4 laser pumped in the 970-980 nm absorption band.
Comprehensive description of the Orion laser facility

NASA Astrophysics Data System (ADS)

Hopps, Nicholas; Oades, Kevin; Andrew, Jim; Brown, Colin; Cooper, Graham; Danson, Colin; Daykin, Simon; Duffield, Stuart; Edwards, Ray; Egan, David; Elsmere, Stephen; Gales, Steve; Girling, Mark; Gumbrell, Edward; Harvey, Ewan; Hillier, David; Hoarty, David; Horsfield, Colin; James, Steven; Leatherland, Alex; Masoero, Stephen; Meadowcroft, Anthony; Norman, Michael; Parker, Stefan; Rothman, Stephen; Rubery, Michael; Treadwell, Paul; Winter, David; Bett, Thomas

2015-06-01

The Orion laser facility at the atomic weapons establishment (AWE) in the UK has been operational since April 2013, fielding experiments that require both its long and short pulse capability. This paper provides a full description of the facility in terms of laser performance, target systems and diagnostics currently available. Inevitably, this is a snapshot of current capability—the available diagnostics and the laser capability are evolving continuously. The laser systems consist of ten beams, optimised around 1 ns pulse duration, which each provide a nominal 500 J at a wavelength of 351 nm. There are also two short pulse beams, which each provide 500 J in 0.5 ps at 1054 nm. There are options for frequency doubling one short pulse beam to enhance the pulse temporal contrast. More recently, further contrast enhancement, based on optical parametric amplification (OPA) in the front end with a pump pulse duration of a few ps, has been installed. An extensive suite of diagnostics are available for users, probing the optical emission, x-rays and particles produced in laser-target interactions. Optical probe diagnostics are also available. A description of the diagnostics is provided.
Compact high-pulse-energy passively Q-switched Nd:YLF laser with an ultra-low-magnification unstable resonator: application for efficient optical parametric oscillator.

PubMed

Cho, C Y; Huang, Y P; Huang, Y J; Chen, Y C; Su, K W; Chen, Y F

2013-01-28

We exploit an ultra-low-magnification unstable resonator to develop a high-pulse-energy side-pumped passively Q-switched Nd:YLF/Cr⁴⁺:YAG laser with improving beam quality. A wedged laser crystal is employed in the cavity to control the emissions at 1047 nm and 1053 nm independently through the cavity alignment. The pulse energies at 1047 nm and 1053 nm are found to be 19 mJ and 23 mJ, respectively. The peak powers for both wavelengths are higher than 2 MW. Furthermore, the developed Nd:YLF lasers are employed to pump a monolithic optical parametric oscillator for confirming the applicability in nonlinear wavelength conversions.
Implementation of a SVWP-based laser beam shaping technique for generation of 100-mJ-level picosecond pulses.

PubMed

Adamonis, J; Aleknavičius, A; Michailovas, K; Balickas, S; Petrauskienė, V; Gertus, T; Michailovas, A

2016-10-01

We present implementation of the energy-efficient and flexible laser beam shaping technique in a high-power and high-energy laser amplifier system. The beam shaping is based on a spatially variable wave plate (SVWP) fabricated by femtosecond laser nanostructuring of glass. We reshaped the initially Gaussian beam into a super-Gaussian (SG) of the 12th order with efficiency of about 50%. The 12th order of the SG beam provided the best compromise between large fill factor, low diffraction on the edges of the active media, and moderate intensity distribution modification during free-space propagation. We obtained 150 mJ pulses of 532 nm radiation. High-energy, pulse duration of 85 ps and the nearly flat-top spatial profile of the beam make it ideal for pumping optical parametric chirped pulse amplification systems.
Orange fiber laser for ophthalmology

NASA Astrophysics Data System (ADS)

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.
Spiking suppression of high power QCW pulse 1319 nm Nd:YAG laser with different intracavity doublers

NASA Astrophysics Data System (ADS)

Bian, Qi; Zuo, Jun-Wei; Guo, Chuan; Xu, Chang; Shen, Yu; Zong, Nan; Bo, Yong; Peng, Qin-Jun; Chen, Hong-Bin; Cui, Da-Fu; Xu, Zu-Yan

2016-09-01

We describe the results of our efforts in suppressing spiking of a high power, high beam quality 1319 nm Nd:YAG microsecond-pulse laser with three different intracavity frequency doublers. The 1319 nm laser is generated by a quasi-continuous-wave diode-pumped Nd:YAG ring laser system. One potassium titanyl phosphate (KTP), two KTPs and one lithium triborate (LBO) as frequency doublers are installed in the ring resonator and tested, respectively. At 800 Hz repetition rate, with a pulse width of 100 µs, performances of spiking suppression for each case are observed. The average output power are 23.6 W, 22.7 W and 23.4 W with beam quality factors of M 2 = 2.21, 1.28 and 1.25 for one KTP, two KTPs and one LBO, respectively. The corresponding brightness are 270 MW/(cm2·sr), 780 MW/(cm2·sr) and 860 MW/(cm2·sr). With better beam quality, higher brightness, and easier maintainability, the LBO is the best option of the three. A laser rate equation model including the insertion loss of the doubler is applied for theoretical analysis of the output temporal pulse shape and power, and the simulated results agree well with the experimental data.
Experimental Demonstration of Longitudinal Beam Phase-Space Linearizer in a Free-Electron Laser Facility by Corrugated Structures

NASA Astrophysics Data System (ADS)

Deng, Haixiao; Zhang, Meng; Feng, Chao; Zhang, Tong; Wang, Xingtao; Lan, Taihe; Feng, Lie; Zhang, Wenyan; Liu, Xiaoqing; Yao, Haifeng; Shen, Lei; Li, Bin; Zhang, Junqiang; Li, Xuan; Fang, Wencheng; Wang, Dan; Couprie, Marie-emmanuelle; Lin, Guoqiang; Liu, Bo; Gu, Qiang; Wang, Dong; Zhao, Zhentang

2014-12-01

Removal of the undesired time-energy correlations in the electron beam is of paramount importance for efficient lasing of a high-gain free-electron laser. Recently, it has been theoretically and experimentally demonstrated that the longitudinal wakefield excited by the electrons themselves in a corrugated structure allows for precise control of the electron beam phase space. In this Letter, we report the first utilization of a corrugated structure as a beam linearizer in the operation of a seeded free-electron laser driven by a 140 MeV linear accelerator, where a gain of ˜10 000 over spontaneous emission was achieved at the second harmonic of the 1047 nm seed laser, and a free-electron laser bandwidth narrowing by 50% was observed, in good agreement with the theoretical expectations.
Short wavelength (visible) GaAs quantum well lasers grown by molecular beam epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woodbridge, K.; Blood, P.; Fletcher, E.D.

1984-07-01

GaAs-AlGaAs multiple quantum well (MQW) injection lasers with well widths from 55 to 13 A have been grown by molecular beam epitaxy and operated at room temperature, showing emission at wavelengths down to 704 nm, the shortest reported for a MQW injection laser with GaAs wells. In a device with 25-A wells some evidence of coupling was apparent when barrier widths were reduced to 40 A. For devices with 80-A barriers there is a difference of about 20 nm between the calculated n = 1 (e--hh) transition wavelength and the lasing wavelength, whereas the calculation agrees with photovoltage absorption measurementsmore » on the same structures.« less
Nd:YAG laser double wavelength ablation of pollution encrustation on marble and bonding glues on duplicated painting canvas

NASA Astrophysics Data System (ADS)

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.
Analysis of all-optical light modulation in proteorhodopsin protein molecules

NASA Astrophysics Data System (ADS)

Roy, Sukhdev; Sharma, Parag

2008-03-01

We present a detailed steady-state and time-dependent theoretical analysis of all-optical light modulation in the recently discovered, wild-type proteorhodopsin (WTpR) protein molecules based on excited-state absorption. Amplitude modulation of cw probe laser beam transmissions at 520, 405, 555 and 560 nm, corresponding to the peak absorption of pR, pRM, pRK and pRN intermediate states of pR photocycle, respectively, by cw and pulsed modulating pump laser beam at 520 nm have been analyzed. The effect of various spectral and kinetic parameters on modulation characteristics has been studied. There is an optimum value of concentration for a given pump intensity value for which maximum modulation of the probe beam can be achieved. The switching characteristics of probe beam at 405 and 520 nm exhibit dip and peak, respectively, which can be removed by decreasing the absorption of pRM state at 520 nm. The modulation in WTpR is at lower pump powers with smaller contrast in comparison to WT bacteriorhodopsin (bR) and WT pharaonis phoborhodopsin (ppR). The modulation characteristics exhibit unique features compared to bR and ppR.
Surface plasmon resonance phenomenon of the insulating state polyaniline

DOE Office of Scientific and Technical Information (OSTI.GOV)

Umiati, Ngurah Ayu Ketut, E-mail: ngurahayuketutumiati@gmail.com; Jurusan Fisika FMIPA Universitas Diponegoro, Jalan Prof. Soedarto, SH Tembalang Semarang 50275; Triyana, Kuwat

2015-04-16

Surface Plasmon Resonance (SPR) phenomenon of the insulating polyaniline (PANI) is has been observed. Surface Plasmon (SP) is the traveled electromagnetic wave that passes through the interface of dielectric metal and excited by attenuated total reflection (ATR) method in Kretschmannn configuration (Au-PANI prism). The resonance condition is observed through the angle of SPR in such condition that SP wave is coupled by the evanescent constant of laser beam. In this research, the laser beam was generated by He–Ne and its wavelength (λ) was 632,8 nm. SPR curve is obtained through observation of incidence angles of the laser beam in prism.more » SPR phenomenon at the boundary between Au – PANI layer has showed by reflection dip when the laser beam passes through the prism. In this early study, the observation was carried out through simulation Winspall 3.02 software and preliminary compared with some experimental data reported in other referred literatures. The results shows that the optimum layer of Au and polyaniline are 50 and 1,5 nm thick respectively. Our own near future experimental work would be further performed and reported elsewhere.« less

Compact high-pulse-energy ultraviolet laser source for ozone lidar measurements.

PubMed

Elsayed, Khaled A; DeYoung, Russell J; Petway, Larry B; Edwards, William C; Barnes, James C; Elsayed-Ali, Hani E

2003-11-20

An all solid-state Ti:sapphire laser differential absorption lidar transmitter was developed. This all-solid-state laser provides a compact, robust, and highly reliable laser transmitter for potential application in differential absorption lidar measurements of atmospheric ozone. Two compact, high-energy-pulsed, and injection-seeded Ti:sapphire lasers operating at a pulse repetition frequency of 30 Hz and wavelengths of 867 and 900 nm, with M2 of 1.3, have been experimentally demonstrated and their properties compared with model results. The output pulse energy was 115 mJ at 867 nm and 105 mJ at 900 nm, with a slope efficiency of 40% and 32%, respectively. At these energies, the beam quality was good enough so that we were able to achieve 30 mJ of ultraviolet laser output at 289 and 300 nm after frequency tripling with two lithium triborate nonlinear crystals.
Femtosecond laser-induced subwavelength ripples formed by asymmetrical grating splitting

NASA Astrophysics Data System (ADS)

Feng, Pin; Jiang, Lan; Li, Xin; Zhang, Kaihu; Shi, Xuesong; Li, Bo; Lu, Yongfeng

2016-05-01

The formation process and mechanism of subwavelength ripples were studied upon irradiation of ZnO by a femtosecond laser (800 nm, 50 fs, 1 kHz). An abnormally asymmetrical grating-splitting phenomenon was discovered. At relatively high laser fluences (F = 0.51-0.63 J/cm2), near-wavelength ripples were split asymmetrically to create subwavelength laser-induced periodic surface structures (LIPSS) with dual gaps (˜230 nm and ˜430 nm) on the primary grooves. At relatively low laser fluences (F = 0.4-0.45 J/cm2), near-wavelength ripples were split symmetrically, leading to the formation of uniform subwavelength structures with a period of ˜340 nm. The splitting phenomena are related to the varying laser beam dose induced by the overlapping during line scanning. The two grating-splitting types further imply that the dominated mechanism for LIPSS formation may be changed under different processing conditions.
Trapped-Ion Quantum Simulation of an Ising Model with Transverse and Longitudinal Fields

DTIC Science & Technology

2013-03-29

resonant λ = 355 nm laser beams which drive stimulated Raman transitions [33, 34]. The beams intersect at right angles so that their wavevector difference...ated by a pair of Raman laser beams with a beatnote frequency of ωS , with the field amplitude determined by the beam intensities. The field directions...cool- ing, followed by optical pumping to the state |↓↓↓ ..〉z and 100 µs of Raman sideband cooling that prepares the motion of all modes along ∆~k in
Efficient frequency doubler of 1560 nm laser based on a semi-monolithic resonant cavity with a PPKTP crystal

NASA Astrophysics Data System (ADS)

Wang, Junmin; Zhang, Kong; Ge, Yulong; Guo, Shanlong

2016-06-01

We have demonstrated 1.61 W of 780 nm single-frequency continuous-wave laser output with a semi-monolithic periodically poled potassium titanyl phosphate (PPKTP) crystal doubler pumped by a 2-W erbium-doped fiber amplifier boosted 1560 nm diode laser. The measured maximum doubling efficiency is 77%, and the practical value should be 80% when taking into account the fundamental-wave mode matching efficiency. The measured beam quality factor of 780 nm output, M2, is better than 1.04. Typical root-mean-square fluctuation of 780 nm output is less than 0.5% in 30 minutes. This compact frequency doubler has good mechanical stability, and can be employed for many applications, such as laser cooling and trapping, atomic coherent control, atomic interferometer, and quantum frequency standard with rubidium atoms.
Modeling and Simulation of a Laser Deposition Process

DTIC Science & Technology

2007-09-04

LAMP system, the diode laser is used. Material of both powder and substrates is Ti - 6Al - 4V , which is widely used in the aerospace industry. Melt Pool...The laser emits at 808 nm and operates in the continuous wave (CW) mode. The substrates have dimensions of 2.5×2.5×0.4 in. The Ti - 6Al - 4V samples were...irradiated using a laser beam with a beam spot diameter of 2.5 mm. Table 1. Material properties for Ti - 6Al - 4V and main process parameters
Excimer laser phototherapy for the dissolution of abnormal growth

DOEpatents

Gruen, D.M.; Young, C.E.; Pellin, M.J.

1985-02-19

Removal of abnormal human tissue with reduced thermal damage is achieved by selecting a laser having a wavelength in the order of 290 to 400 nm, orienting a laser-transmitting glass member toward the abnormal tissue and directing the laser through the glass member at power densities, pulse rates, and times sufficient to cause multiphoton absorption and bond breaking by Coulomb repulsion rather than thermal destruction. The glass member may include a laser beam concentrator provided by a lens or cone at the tissue-treatment end to increase the beam energy per unit area and reduce the treatment area. 6 figs.
Excimer laser phototherapy for the dissolution of abnormal growth

DOEpatents

Gruen, Dieter M.; Young, Charles E.; Pellin, Michael J.

1987-01-01

Removal of abnormal human tissue with reduced thermal damage is achieved by selecting a laser having a wavelength in the order of 290-400 nm, orienting a laser-transmitting glass member toward the abnormal tissue and directing the laser through the glass member at power densities, pulse rates, and times sufficient to cause multiphoton absorption and bond breaking by Coulomb repulsion rather than thermal destruction. The glass member may include a laser beam concentrator provided by a lens or cone at the tissue-treatment end to increase the beam energy per unit area and reduce the treatment area.
DPSSL for direct dicing and drilling of dielectrics

NASA Astrophysics Data System (ADS)

Ashkenasi, David; Schwagmeier, M.

2007-02-01

New strategies in laser micro processing of glasses and other optically transparent materials are being developed with increasing interest and intensity using diode pumped solid state laser (DPSSL) systems generating short or ultra-short pulses in the optical spectra at good beam quality. Utilizing non-linear absorption channels, it can be demonstrated that ns green (532 nm) laser light can scribe, dice, full body cut and drill (flat) borofloat and borosilicate glasses at good quality. Outside of the correct choice in laser parameters, an intelligent laser beam management plays an important role in successful micro processing of glass. This application characterizes a very interesting alternative where standard methods demonstrate severe limitations such as diamond dicing, CO2 laser treatment or water jet cutting, especially for certain type of optical materials and/or geometric conditions. Application near processing examples using different DPSSL systems generating ns pulsed light at 532 nm in TEM 00 at average powers up to 10 W are presented and discussed in respect to potential applications in display technology, micro electronics and optics.
Extreme ultraviolet interferometry of warm dense matter in laser plasmas.

PubMed

Gartside, L M R; Tallents, G J; Rossall, A K; Wagenaars, E; Whittaker, D S; Kozlová, M; Nejdl, J; Sawicka, M; Polan, J; Kalal, M; Rus, B

2010-11-15

We demonstrate that interferometric probing with extreme ultraviolet (EUV) laser light enables determination of the degree of ionization of the "warm dense matter" produced between the critical and ablation surfaces of laser plasmas. Interferometry has been utilized to measure both transmission and phase information for an EUV laser beam at the photon energy of 58.5 eV, probing longitudinally through laser-irradiated plastic (parylene-N) targets (thickness 350 nm) irradiated by a 300 ps duration pulse of wavelength 438 nm and peak irradiance 10(12) W cm(-2). The transmission of the EUV probe beam provides a measure of the rate of target ablation, as ablated plasma becomes close to transparent when the photon energy is less than the ionization energy of the predominant ion species. We show that refractive indices η below the solid parylene N (η(solid) = 0.946) and expected plasma values are produced in the warm dense plasma created by laser irradiation due to bound-free absorption in C(+).
Multi-gigahertz, femtosecond Airy beam optical parametric oscillator pumped at 78 MHz

PubMed Central

Aadhi, A.; Sharma, Varun; Chaitanya, N. Apurv; Samanta, G. K.

2017-01-01

We report a high power ultrafast Airy beam source producing femtosecond pulses at multi-gigahertz (GHz) repetition rate (RR). Based on intra-cavity cubic phase modulation of an optical parametric oscillator (OPO) designed in high harmonic cavity configuration synchronous to a femtosecond Yb-fiber laser operating at 78 MHz, we have produced ultrafast 2D Airy beam at multi-GHz repetition rate through the fractional increment in the cavity length. While small (<1 mm) crystals are used in femtosecond OPOs to take the advantage of broad phase-matching bandwidth, here, we have exploited the extended phase-matching bandwidth of a 50-mm long Magnesium-oxide doped periodically poled LiNbO3 (MgO:PPLN) crystal for efficient generation of ultrafast Airy beam and broadband mid-IR radiation. Pumping the MgO:PPLN crystal of grating period, Λ = 30 μm and crystal temperature, T = 100 °C using a 5-W femtosecond laser centred at 1064 nm, we have produced Airy beam radiation of 684 mW in ~639 fs (transform limited) pulses at 1525 nm at a RR of ~2.5 GHz. Additionally, the source produces broadband idler radiation with maximum power of 510 mW and 94 nm bandwidth at 3548 nm in Gaussian beam profile. Using an indirect method (change in cavity length) we estimate maximum RR of the Airy beam source to be ~100 GHz. PMID:28262823
Photoinduced second-order optical susceptibilities of Er 2O 3 doped TeO 2-GeO 2-PbO glasses

NASA Astrophysics Data System (ADS)

Kassab, L. R. P.; Pinto, R. de A.; Kobayashi, R. A.; Piasecki, M.; Bragiel, P.; Kityk, I. V.

2007-06-01

Second-order optical susceptibilities were established in the optically poled erbium doped tellurite glasses near the melting temperature. The non-linear optical susceptibility was formed by bicolor coherent optical treatment performed by two coherent laser beams originated from 50 ps Nd-YAG laser ( λ = 1.32 μm) exciting the high pressure hydrogen laser cell emitting at 1907 nm. The non-centrosymmetric grating of the medium was created by coherent superposition of the fundamental laser illumination at 1907 nm and the doubled frequency one at 953.5 nm. The maximally all-optically poled SHG occurs for 2% doped Er 2O 3 (in weighting units) TeO 2-GeO 2-PbO glass. It was found that the photoinduced SHG demonstrates a saturation during the photo-treatment of 9-10 min using the two beams polarized at angle about 45° between them. During the coherent bicolor optical treatment it was achieved the value of second-order susceptibility up to 3.6 pm/V at 1907 nm. The optimal ratio between the fundamental beam with power density about 1.1 GW/cm 2 and writing doubled frequency seeding beam about 0.015 GW/cm 2 corresponds to the maximal of photoinduced SHG. For glasses with lower concentration of Er 2O 3, the relaxation of the second-order optical susceptibility is substantially longer and achieves SHG value that corresponds to 80% of the maximal ones. It is necessary to emphasize that efficient optically-poled grating exists only within the narrow temperature range near the glassing temperature. Possible physical mechanisms of the phenomenon observed are discussed. Generally the used glasses possess better parameters than early investigated germinate glasses.
Resonantly diode-pumped eye-safe Er:YAG laser with fiber-shaped crystal

NASA Astrophysics Data System (ADS)

Němec, Michal; Šulc, Jan; Hlinomaz, Kryštof; Jelínková, Helena; Nejezchleb, Karel; Čech, Miroslav

2018-02-01

Solid-state eye-safe lasers are interesting sources for various applications, such as lidar, remote sensing, and ranging. A resonantly diode-pumped Er:YAG laser could be one of them allowing to reach a tunable laser emission in 1.6 μm spectral region. To overcome low pump absorption and poor pumping beam quality generated by commercially available laser diode, an active medium could be formed to long and thin laser rod guiding pumping radiation. Such an effective cooling during a high power pumping, which is a "crystal-fiber" benefit, may be useful for "standard" crystal active medium. The main goal of this work was to investigate the laser characteristics of new developed Er:YAG crystal with a special shape for diode-pumping. Er:YAG fiber-shape crystal with square cross-section (1x1mm) and 40mm in length was doped by 0.1% Er3+ ions. All sides of this crystal were polished and in addition the end-faces of it were antireflection coatings for the wavelength 1470 and 1645 nm. As a pump system, a fiber coupled laser diode (f = 10 Hz, t = 10 ms) emitting radiation at 1465 nm wavelength was used. Er:YAG fiber-shape crystal was placed onto a copper holder in the 85 mm long plan-concave resonator consisting of a pump flat mirror and output curved (r = 150 mm) coupler with a reflectivity of 96 % @ 1645 nm. The dependence of the output peak power on absorbed pump power was investigated and the maximum 0.8 W was obtained. The corresponding slope efficiency was 14.5 %. The emitting wavelength was equaled to 1645 nm (4 nm linewidth, FWHM). The spatial beam structure was close to the Gaussian mode.
Single-shot high aspect ratio bulk nanostructuring of fused silica using chirp-controlled ultrafast laser Bessel beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhuyan, M. K.; Velpula, P. K.; Colombier, J. P.

2014-01-13

We report single-shot, high aspect ratio nanovoid fabrication in bulk fused silica using zeroth order chirp-controlled ultrafast laser Bessel beams. We identify a unique laser pulse length and energy dependence of the physical characteristics of machined structures over which nanovoids of diameter in the range 200–400 nm and aspect ratios exceeding 1000 can be fabricated. A mechanism based on the axial energy deposition of nonlinear ultrashort Bessel beams and subsequent material densification or rarefaction in fused silica is proposed, intricating the non-diffractive nature with the diffusing character of laser-generated free carriers. Fluid flow through nanochannel is also demonstrated.
Sodern development of a high LIDT laser beam expander for ATLID

NASA Astrophysics Data System (ADS)

Battarel, Denis C.; Barnasson, Elodie

2017-11-01

Sodern has been contracted for the development of the laser beam expander used on the lidar of the ATLID instrument developed by Airbus Defence & Space France and Germany (Formerly ASTRIUM) embarked on the EathCARE satellite, element of the ESA (European Space Agency) Living Planet Programme. The ATLID emission beam expander (E-BEX) has two functions: one is to reduce the divergence of the laser in order to achieve a high spatial resolution and the other is to enlarge the laser beam to reduce the power density and thus reduce Laser Induced Contamination (LIC) and Laser Induced Damage Threshold (LIDT) effects on the outer surface exposed to vacuum. This paper exposes the design drivers of the beam expander which are: having optical components withstanding very high laser fluence at a wavelength of 355nm and exhibiting a very low depolarization ratio., hermetically sealing the cavity with metallic gaskets in order to keep the pressure constant so that beam collimation is not affected, choosing housing material compatible with both hermiticity requirements and thermal control. To obtain a high spatial resolution on Earth, ATLID requires a means for controlling beam collimation. This is ensured by an active thermal control on the beam expander in order to change its Wavefront Error (WFE) by a few tens of nanometers.
High power Yb:CALGO ultrafast regenerative amplifier for industrial application

NASA Astrophysics Data System (ADS)

Caracciolo, E.; Guandalini, A.; Pirzio, F.; Kemnitzer, M.; Kienle, F.; Agnesi, A.; Aus der Au, J.

2017-02-01

We present a high-power, single-crystal based, Yb:CALGO regenerative amplifier. The system delivers more than 50 W output power in continuous-wave regime, with diffraction limited beam quality. In Q-switching regime the spectrum is centered at 1043 nm and is 11 nm wide. In regenerative amplification experiments we achieved 34 W at 500 kHz with 12.7 nm FWHM wide spectra centered at 1044 nm seeding with a broadly tunable, single-prism SESAM mode-locked Yb:CALGO laser providing 9 nm wide spectra at 1049 nm. Pulse duration after compression was 140 fs, with excellent beam quality (M2 < 1.25).
Atmospheric propagation of high power laser radiation at different weather conditions

NASA Astrophysics Data System (ADS)

Pargmann, Carsten; Hall, Thomas; Duschek, Frank; Handke, Jürgen

2016-05-01

Applications based on the propagation of high power laser radiation through the atmosphere are limited in range and effect, due to weather dependent beam wandering, beam deterioration, and scattering processes. Security and defense related application examples are countermeasures against hostile projectiles and the powering of satellites and aircrafts. For an examination of the correlations between weather condition and laser beam characteristics DLR operates at Lampoldshausen a 130 m long free transmission laser test range. Sensors around this test range continuously monitor turbulence strength, visibility, precipitation, temperature, and wind speed. High power laser radiation is obtained by a TruDisk 6001 disk laser (Trumpf company) yielding a maximum output power of 6 kW at a wavelength of 1030 nm. The laser beam is expanded to 180 mm and focused along the beam path. Power and intensity distribution are measured before and after propagation, providing information about the atmospheric transmission and alterations of diameter and position of the laser beam. Backscattered laser light is acquired by a photo receiver. As a result, measurements performed at different weather conditions show a couple of correlations to the characteristics of the laser beam. The experimental results are compared to a numerical analysis. The calculations are based on the Maxwell wave equation in Fresnel approximation. The turbulence is considered by the introduction of phase screens and the "von Karman" spectrum.
A Compact Ti:Sapphire Laser With its Third Harmonic Generation (THG) for an Airborne Ozone Differential Absorption Lidar (DIAL) Transmitter

NASA Technical Reports Server (NTRS)

Chen, Songsheng; Storm, Mark E.; Marsh, Waverly D.; Petway, Larry B.; Edwards, William C.; Barnes, James C.

2000-01-01

A compact and high-pulse-energy Ti:Sapphire laser with its Third Harmonic Generation (THG) has been developed for an airborne ozone differential absorption lidar (DIAL) to study the distributions and concentrations of the ozone throughout the troposphere. The Ti:Sapphire laser, pumped by a frequency-doubled Nd:YAG laser and seeded by a single mode diode laser, is operated either at 867 nm or at 900 nm with a pulse repetition frequency of 20 Hz. High energy laser pulses (more than 110 mJ/pulse) at 867 nm or 900 nm with a desired beam quality have been achieved and utilized to generate its third harmonic at 289nm or 300nm, which are on-line and off-line wavelengths of an airborne ozone DIAL. After being experimentally compared with Beta-Barium Borate (beta - BaB2O4 or BBO) nonlinear crystals, two Lithium Triborate (LBO) crystals (5 x 5 x 20 cu mm) are selected for the Third Harmonic Generation (THG). In this paper, we report the Ti:Sapphire laser at 900 nm and its third harmonic at 300 nm. The desired high ultraviolet (UV) output pulse energy is more than 30 mJ at 300 nm and the energy conversion efficiency from 900 nm to 300 nm is 30%.
Dual-wavelength, continuous-wave Yb:YAG laser for high-resolution photothermal common-path interferometry.

PubMed

Zhuang, Fengjiang; Jungbluth, Bernd; Gronloh, Bastian; Hoffmann, Hans-Dieter; Zhang, Ge

2013-07-20

We present a continuous-wave (CW) intracavity frequency-doubled Yb:YAG laser providing 1030 and 515 nm output simultaneously. This laser system was designed for photothermal common-path interferometry to measure spatially resolved profiles of the linear absorption in dielectric media and coatings for visible or infrared light as well as of the nonlinear absorption for the combination of both. A Z-shape laser cavity was designed, providing a beam waist in which an LBO crystal was located for effective second-harmonic generation (SHG). Suitable frequency conversion parameters and cavity configurations were discussed to achieve the optimal performance of a diode-pumped CW SHG laser. A 12.4 W 1030 nm laser and 5.4 W 515 nm laser were developed simultaneously in our experiment.
Some aspects of precise laser machining - Part 2: Experimental

NASA Astrophysics Data System (ADS)

Grabowski, Marcin; Wyszynski, Dominik; Ostrowski, Robert

2018-05-01

The paper describes the role of laser beam polarization on quality of laser beam machined cutting tool edge. In micromachining the preparation of the cutting tools in play a key role on dimensional accuracy, sharpness and the quality of the cutting edges. In order to assure quality and dimensional accuracy of the cutting tool edge it is necessary to apply laser polarization control. In the research diode pumped Nd:YAG 532nm pulse laser was applied. Laser beam polarization used in the research was linear (horizontal, vertical). The goal of the carried out research was to describe impact of laser beam polarization on efficiency of the cutting process and quality of machined parts (edge, surface) made of polycrystalline diamond (PCD) and cubic boron nitride (cBN). Application of precise cutting tool in micromachining has significant impact on the minimum uncut chip thickness and quality of the parts. The research was carried within the INNOLOT program funded by the National Centre for Research and Development.
Laser induced fluorescence of dental caries

NASA Technical Reports Server (NTRS)

Albin, S.; Byvik, C. E.; Buoncristiani, A. M.

1988-01-01

Significant differences between the optical spectra taken from sound regions of teeth and carious regions have been observed. These differences appear both in absorption and in laser induced fluorescence spectra. Excitation by the 488 nm line of an argon ion laser beam showed a peak in the emission intensity around 553 nm for the sound dental material while the emission peak from the carious region was red-shifted by approximately 40 nm. The relative absorption of carious region was significantly higher at 488 nm; however its fluorescence intensity peak was lower by an order of magnitude compared to the sound tooth. Implications of these results for a safe, reliable and early detection of dental caries are discussed.

Laser Demonstration of Diode-Pumped Nd3+-Doped Fluorapatite Anisotropic Ceramics

NASA Astrophysics Data System (ADS)

Akiyama, Jun; Sato, Yoichi; Taira, Takunori

2011-02-01

We report the first demonstration of a diode-pumped anisotropic ceramic laser that uses microdomain-controlled neodymium-doped hexagonal fluorapatite [Nd3+:Ca10(PO4)6F2, Nd:FAP] polycrystalline ceramics as the gain medium, which were fabricated by the rare-earth-assisted magnetic grain-orientation control method, as a step toward achieving giant micro photonics. The laser delivers 1063.10 and 1063.22 nm output beams when pumped with a central wavelength of 807.5 nm and a 2 nm bandwidth diode laser operating in quasi-continuous-wave (QCW) mode. We obtained a maximum QCW peak power of 255 mW with an uncoated 2 at. % Nd:FAP material.
Mountain-Top-to-Mountain-Top Optical Link Demonstration. Part 1

NASA Technical Reports Server (NTRS)

Biswas, A.; Wright, M. W.

2002-01-01

A mountain-top-to-mountain-top optical link was demonstrated between JPL's Table Mountain Facility (TMF), Wrightwood, California, and Strawberry Peak (SP), Lake Arrowhead, California, during the months of June, August, and September of 2000. The bidirectional laser link was nearly horizontal at an altitude of 2 km and spanned a range of 46.8 km. The 780-nm beacon laser transmitted from TMF comprised eight co-propagating mutually incoherent laser beams. The normalized variance or scintillation index (SI) of the individual beacon lasers measured by recording the signal received through 8.50-cm-diameter spotting telescopes on three different nights (June 28-30, 2000) was 1.05 +/- 0.2, 1.76 +/- 0.6, and 0.96 +/- 0.24, respectively. These measurements agreed with values predicted by a heuristic model. The SI of the signal received at SP was found to decrease progressively with an increasing number of beams, and a factor of 3 to 3.5 reduction was achieved for all eight beams. The beam divergence determined by mapping out the point spread function of a few of the individual laser footprints received at SP was 85 to 150 microrad, compared to a design goal of 120 microrad. The 852-nm communications laser beam received at TMF through a 60-cm-diameter telescope on the nights of August 4 and September 14 and 15, 2000, yielded SI values of 0.23 +/- 0.04, 0.32 +/- 0.01, and 0.49 +/- 0.18, respectively, where the reduction was attributed to aperture averaging. The probability distribution functions of the received signal at either end, mitigated by multi-beam averaging in one direction and by aperture averaging in the other direction, displayed lognormal behavior. Consequently, the measured fade statistics showed good agreement with a lognormal model.
Stimulated Raman scattering holography for time-resolved imaging of methane gas.

PubMed

Amer, Eynas; Gren, Per; Edenharder, Stefan; Sjödahl, Mikael

2016-05-01

In this paper, pulsed digital holographic detection is coupled to the stimulated Raman scattering (SRS) process for imaging gases. A Q-switched Nd-YAG laser (532 nm) has been used to pump methane gas (CH₄) at pressures up to 12 bars. The frequency-tripled (355 nm) beam from the same laser was used to pump an optical parametric oscillator (OPO). The Stokes beam (from the OPO) has been tuned to 629.93 nm so that the frequency difference between the pump (532 nm) and the Stokes beams fits a Raman active vibrational mode of the methane molecule (2922 cm^-1). The pump beam has been spatially modulated with fringes produced in a Michelson interferometer. The pump and the Stokes beams were overlapped in time, space, and polarization on the gas molecules, resulting in a stimulated Raman gain of the Stokes beam and a corresponding loss of the pump beam through the SRS process. The resulting gain of the Stokes beam has been detected using pulsed digital holography by blending it with a reference beam on the detector. Two holograms of the Stokes beam, without and with the pump beam fringes present, were recorded. Intensity maps calculated from the recorded digital holograms showed amplification of the Stokes beam at the position of overlap with the pump beam fringes and the gas molecules. The gain of the Stokes beam has been separated from the background in the Fourier domain. A gain of about 4.5% at a pump beam average intensity of 4 MW/cm² and a Stokes beam intensity of 0.16 MW/cm² have been recorded at a gas pressure of 12 bars. The gain decreased linearly with decreasing gas pressure. The results show that SRS holography is a promising technique to pinpoint a specific species and record its spatial and temporal distribution.
Two-photon equivalent weighting of spatial excimer laser beam profiles

NASA Astrophysics Data System (ADS)

Eva, Eric; Bauer, Harry H.; Metzger, K.; Pfeiffer, A.

2001-04-01

Damage in optical materials for semiconductor lithography applications caused by exposure to 248 or 193 nm light is usually two-photon driven, hence it is a nonlinear function of incident intensity. Materials should be tested with flat- topped temporal and spatial laser beam profiles to facilitate interpretation of data, but in reality this is hard to achieve. Sandstrom provided a formula that approximates any given temporal pulse shape with a two- photon equivalent rectangular pulse (Second Symposium on 193 nm Lithography, Colorado Springs 1997). Known as the integral-square pulse duration, this definition has been embraced as an industry standard. Originally faced with the problem of comparing results obtained with pseudo-Gaussian spatial profiles to literature data, we found that a general solution for arbitrarily inhomogeneous spatial beam profiles exists which results in a definition much similar to Sandstrom's. In addition, we proved the validity of our approach in experiments with intentionally altered beam profiles.
Motion-free hybrid design laser beam propagation analyzer using a digital micromirror device and a variable focus liquid lens.

PubMed

Sheikh, Mumtaz; Riza, Nabeel A

2010-06-01

To the best of our knowledge, we propose the first motion-free laser beam propagation analyzer with a hybrid design using a digital micromirror device (DMD) and a liquid electronically controlled variable focus lens (ECVFL). Unlike prior analyzers that require profiling the beam at multiple locations along the light propagation axis, the proposed analyzer profiles the beam at the same plane for multiple values of the ECVFL focal length, thus eliminating beam profiler assembly motion. In addition to measuring standard Gaussian beam parameters, the analyzer can also be used to measure the M(2) beam propagation parameter of a multimode beam. Proof-of-concept beam parameter measurements with the proposed analyzer are successfully conducted for a 633 nm laser beam. Given the all-digital nature of the DMD-based profiling and all-analog motion-free nature of the ECVFL beam focus control, the proposed analyzer versus prior art promises better repeatability, speed, and reliability.
Fabrication of low loss waveguide using fundamental light of Yb-based femtosecond laser (Conference Presentation)

NASA Astrophysics Data System (ADS)

Imai, Ryo; Konishi, Kuniaki; Yumoto, Junji; Gonokami, Makoto K.

2017-03-01

Laser direct writing of optical devices and circuits is attracted attention because of its ability of three-dimensional fabrication without any mask[1]. Recently, Yb-fiber or solid-state laser has been commonly used for fabrication in addition to traditional Ti:S laser. However, it is reported that waveguide cannot be fabricated in fused silica by using the fundamental light from Yb-based femtosecond laser[2]. Some groups reported on waveguide fabrication by using second-harmonic beam of such lasers[3], but wavelength conversion using nonlinear process has drawbacks such as destabilization of laser power and beam deformation by walk off. In this study, we investigated fabrication of low-loss waveguide in fused silica by using the fundamental beam (1030nm) from an Yb solid-state femtosecond laser with a pulse duration of 250 fs. The NA of focusing objective lens was 0.42. The fabricated waveguide was made to have a circular cross-section by shaping laser beam with a slit[4]. We fixed repetition rate to 150 kHz, and identified appropriate scan speed and pulse energy for fabrication of low loss waveguide. Waveguide fabricated with appropriate condition had a propagation loss of 0.2 dB/cm, and this is the first report on optical waveguides in a fused silica fabricated by femto-second laser pulses at a wavelength of 1030nm. [1]K. M. Davis, et. al., Opt. Lett 21, 1729(1996) [2]J. Canning, et. al., Opt. Mater. Express 1, 998(2011) [3]L. Shah, et. al., Opt. Express 13, 1999(2005) [4]M. Ams, et. al., Opt. Express 13, 5676(2005)
UV-laser-based longitudinal illuminated diffuser (LID) incorporating diffractive and Lambertian reflectance for the disinfection of beverages

NASA Astrophysics Data System (ADS)

Lizotte, Todd

2010-08-01

A novel laser beam shaping system was designed to demonstrate the potential of using high power UV laser sources for large scale disinfection of liquids used in the production of food products, such as juices, beer, milk and other beverage types. The design incorporates a patented assembly of optical components including a diffractive beam splitting/shaping element and a faceted pyramidal or conically shaped Lambertian diffuser made from a compression molded PTFE compounds. When properly sintered to an appropriate density, as an example between 1.10 and 1.40 grams per cubic centimeter, the compressed PTFE compounds show a ~99% reflectance at wavelengths ranging from 300 nm to 1500 nm, and a ~98.5% refection of wavelengths from 250 nm to 2000 nm [1]. The unique diffuser configuration also benefits from the fact that the PTFE compounds do not degrade when exposed to ultraviolet radiation as do barium sulfate materials and silver or aluminized mirror coatings [2]. These components are contained within a hermetically sealed quartz tube. Once assembled a laser beam is directed through one end of the tube. This window takes the form of a computer generated diffractive splitter or other diffractive shaper element to split the laser beam into a series of spot beamlets, circular rings or other geometric shapes. As each of the split beamlets or rings cascade downward, they illuminate various points along the tapered PTFE cone or faceted pyramidal form. As they strike the surface they each diffuse in a Lambertian reflectance pattern creating a pseudo-uniform circumferential illuminator along the length of the quartz tube enclosing the assembly. The compact tubular structure termed Longitudinal Illuminated Diffuser (LID) provides a unique UV disinfection source that can be placed within a centrifugal reactor or a pipe based reactor chamber. This paper will review the overall design principle, key component design parameters, preliminary analytic and bench operational testing results.
Cr:ZnSe laser pumped with Tm:YAP microchip laser

NASA Astrophysics Data System (ADS)

Koranda, Petr; Sulc, Jan; Doroshenko, Maxim; Jelinková, Helena; Basiev, Tasoltan T.; Osiko, Vjatcheslav; Badikov, V. V.; Badikov, D.

2010-02-01

Cr:ZnSe laser coherently longitudinally pumped with Tm:YAP microchip laser was realised. The pumping laser consisted of Tm:YAP crystal (3x3 mm) with resonator mirrors deposited directly on its faces (on rear face the dielectric layer with high reflectance for 1998 nm wavelength and high transmittance for 790 nm pumping radiation wavelength; on output face the dielectric layer with reflectance 97% at 1998 nm wavelength). The maximal output power was 5.5 W and the generated radiation wavelength was 1998 nm. The main advantage of this pumping was stable and still output without relaxation spikes (non-spiking). The Tm:YAP laser radiation was collimated and focused by the set of two CaF2 lenses. The pumping beam spot diameter inside the Cr:ZnSe crystal was 300 μm. The Cr:ZnSe laser resonator consisted of flat rear mirror (HT at 1998 nm and HR at 2100 - 2900 nm) and curved output coupler (r = -150 mm, R = 95% at 2100 - 2700 nm). The maximal output energy of stable radiation was 4 mJ (pulse duration 10 ms, repetition rate 10 Hz). For wavelength tuning the Lyott filter (quartz plate under Brewster angle) was placed between the Cr:ZnSe crystal and output coupler. The generated radiation wavelength was continuously tunable from 2246 - 2650 nm.
Laser Beat-Wave Magnetization of a Dense Plasma

NASA Astrophysics Data System (ADS)

Yates, Kevin; Hsu, Scott; Montgomery, David; Dunn, John; Langendorf, Samuel; Pollock, Bradley; Johnson, Timothy; Welch, Dale; Thoma, Carsten

2017-10-01

We present results from the first of a series of experiments to demonstrate and characterize laser beat-wave magnetization of a dense plasma, motivated by the desire to create high-beta targets with standoff for magneto-inertial fusion. The experiments are being conducted at the Jupiter Laser Facility (JLF) at LLNL. The experiment uses the JLF Janus 1 ω (1053 nm) beam and a standalone Nd:YAG (1064 nm) to drive the beat wave, and the Janus 2 ω (526.5 nm) beam to ionize/heat a gas-jet target as well as to provide Thomson-scattering (TS) measurements of the target density/temperature and scattered light from the beat wave. Streaked TS data captured electron-plasma-wave and ion-acoustic-wave features utilizing either nitrogen or helium gas jets. Effects of initial gas density as well as laser intensity on target have been measured, with electron densities ranging from 1E18 to 1E19 cm-3 with temperatures of tens to hundreds of eV, near the desired range for optimal field generation. LSP simulations were run to aid experimental design and data interpretation. LANL LDRD Program.
Wavelength tunable CW red laser generated based on an intracavity-SFG composite cavity

NASA Astrophysics Data System (ADS)

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.
All Fiber-Coupled OH Planar Laser-Induced-Fluorescence (OH-PLIF)-Based Two-Dimensional Thermometry.

PubMed

Hsu, Paul S; Jiang, Naibo; Patnaik, Anil K; Katta, Vish; Roy, Sukesh; Gord, James R

2018-04-01

Two-color, planar laser-induced fluorescence (PLIF)-based two-dimensional (2D) thermometry techniques for reacting flows, which are typically developed in the laboratory conditions, face a stiff challenge in their practical implementation in harsh environments such as combustion rigs. In addition to limited optical access, the critical experimental conditions (i.e., uncontrolled humidity, vibration, and large thermal gradients) often restrict sensitive laser system operation and cause difficulties maintaining beam-overlap. Thus, an all fiber-coupled, two-color OH-PLIF system has been developed, employing two long optical fibers allowing isolation of the laser and signal-collection systems. Two OH-excitation laser beams (∼283 nm and ∼286 nm) are delivered through a common 6 m long, 400 µm core, deep ultraviolet (UV)-enhanced multimode fiber. The fluorescence signal (∼310 nm) is collected by a 3 m long, UV-grade imaging fiber. Proof-of-principle temperature measurements are demonstrated in atmospheric pressure, near adiabatic, CH 4 /O 2 /N 2 jet flames. The effects of the excitation pulse interval on fiber transmission are investigated. The proof-of-principle measurements show significant promise for thermometry in harsh environments such as gas turbine engine tests.
[Spectral properties of light migration in apple fruit tissue].

PubMed

Sun, Teng-Fei; Zhang, Teng-Teng; Zheng, Tian-Tian; Cao, Zeng-Hui; Zhang, Jun

2013-11-01

The present paper simulates laser wavelength 632 and 750 nm Gaussian beam migration in apple fruit tissue using Monte-Carlo method, and researches the spectral properties of absorption and scattering. It was shown that the special energy distribution characteristics of Gaussian beam influenced the diffusion of the laser in the tissue, the reflection, absorption and transmittance of 750 nm by tissue are lower, there are more photons interacting with tissue within the tissue, and they can more clearly reflect the information within the tissue. So, the transmission characteristics of the infrared light were relatively strong in biology tissue, which was convenient for researching biology tissue.
Design of 150W, 105-μm, 0.22NA, fiber coupled laser diode module by ZEMAX

NASA Astrophysics Data System (ADS)

Qi, Yunfei; Zhao, Pengfei; Chen, Qing; Wu, Yulong; Chen, Yongqi; Zou, Yonggang; Lin, Xuechun

2016-10-01

We represent a design of a high brightness, fiber coupled diode laser module based on 16 single emitters at 915nm. The module can produce more than 150 Watts output power from a standard fiber with core diameter of 105μm and numerical aperture (NA) of 0.22. To achieve a high power and high brightness laser beam, the spatial beam combination and polarization beam combination are used to combine output of 16 single emitters into a single beam, and then an aspheric lens is used to couple the combined beam into an optical fiber. The simulation show that the total coupling efficiency is more than 95% and the highest brightness is estimated to be 11MW/ (cm2*sr).
Effects of laser fluence on silicon modification by four-beam laser interference

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Le; Li, Dayou; JR3CN and IRAC, University of Bedfordshire, Luton LU1 3JU

2015-12-21

This paper discusses the effects of laser fluence on silicon modification by four-beam laser interference. In this work, four-beam laser interference was used to pattern single crystal silicon wafers for the fabrication of surface structures, and the number of laser pulses was applied to the process in air. By controlling the parameters of laser irradiation, different shapes of silicon structures were fabricated. The results were obtained with the single laser fluence of 354 mJ/cm{sup 2}, 495 mJ/cm{sup 2}, and 637 mJ/cm{sup 2}, the pulse repetition rate of 10 Hz, the laser exposure pulses of 30, 100, and 300, the laser wavelength of 1064 nm, andmore » the pulse duration of 7–9 ns. The effects of the heat transfer and the radiation of laser interference plasma on silicon wafer surfaces were investigated. The equations of heat flow and radiation effects of laser plasma of interfering patterns in a four-beam laser interference distribution were proposed to describe their impacts on silicon wafer surfaces. The experimental results have shown that the laser fluence has to be properly selected for the fabrication of well-defined surface structures in a four-beam laser interference process. Laser interference patterns can directly fabricate different shape structures for their corresponding applications.« less
Near-infrared supercontinuum laser beam source in the second and third near-infrared optical windows used to image more deeply through thick tissue as compared with images from a lamp source

NASA Astrophysics Data System (ADS)

Sordillo, Laura A.; Lindwasser, Lukas; Budansky, Yury; Leproux, Philippe; Alfano, Robert R.

2015-03-01

With the use of longer near-infrared (NIR) wavelengths, image quality can be increased due to less scattering (described by the inverse wavelength power dependence 1/λn where n≥1) and minimal absorption from water molecules. Longer NIR windows, known as the second (1100 nm to 1350 nm) and third (1600 to 1870 nm) NIR windows are utilized to penetrate more deeply into tissue media and produce high-quality images. An NIR supercontinuum (SC) laser light source, with wavelengths in the second and third NIR optical windows to image tissue provides ballistic imaging of tissue. The SC ballistic beam can penetrate depths of up to 10 mm through tissue.
Thin film beam splitter multiple short pulse generation for enhanced Ni-like Ag x-ray laser emission.

PubMed

Cojocaru, Gabriel V; Ungureanu, Razvan G; Banici, Romeo A; Ursescu, Daniel; Delmas, Olivier; Pittman, Moana; Guilbaud, Olivier; Kazamias, Sophie; Cassou, Kevin; Demailly, Julien; Neveu, Olivier; Baynard, Elsa; Ros, David

2014-04-15

An alternative, novel multiple pulse generation scheme was implemented directly after the optical compressor output of an x-ray pump laser. The new method uses a polarization sensitive thin film beam splitter and a half-wavelength wave plate for tuning the energy ratio in the multiple short pulses. Based on this method, an extensive study was made of the running parameters for a grazing incidence pumped silver x-ray laser (XRL) pumped with a long pulse of 145 mJ in 6 ns at 532 nm and up to 1.45 J in few picoseconds at 810 nm. Fivefold enhancement in the emission of the silver XRL was demonstrated using the new pump method.
Two-wavelength, passive self-injection-controlled operation of diode-pumped cw Yb-doped crystal lasers.

PubMed

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.
Visible high power fiber coupled diode lasers

NASA Astrophysics Data System (ADS)

Köhler, Bernd; Drovs, Simon; Stoiber, Michael; Dürsch, Sascha; Kissel, Heiko; Könning, Tobias; Biesenbach, Jens; König, Harald; Lell, Alfred; Stojetz, Bernhard; Löffler, Andreas; Strauß, Uwe

2018-02-01

In this paper we report on further development of fiber coupled high-power diode lasers in the visible spectral range. New visible laser modules presented in this paper include the use of multi single emitter arrays @ 450 nm leading to a 120 W fiber coupled unit with a beam quality of 44 mm x mrad, as well as very compact modules with multi-W output power from 405 nm to 640 nm. However, as these lasers are based on single emitters, power scaling quickly leads to bulky laser units with a lot of optical components to be aligned. We also report on a new approach based on 450 nm diode laser bars, which dramatically reduces size and alignment effort. These activities were performed within the German government-funded project "BlauLas": a maximum output power of 80 W per bar has been demonstrated @ 450 nm. We show results of a 200 μm NA0.22 fiber coupled 35 W source @ 450 nm, which has been reduced in size by a factor of 25 compared to standard single emitter approach. In addition, we will present a 200 μm NA0.22 fiber coupled laser unit with an output power of 135 W.
Kerr-lens mode-locked Ti:Sapphire laser pumped by a single laser diode

NASA Astrophysics Data System (ADS)

Kopylov, D. A.; Esaulkov, M. N.; Kuritsyn, I. I.; Mavritskiy, A. O.; Perminov, B. E.; Konyashchenko, A. V.; Murzina, T. V.; Maydykovskiy, A. I.

2018-04-01

The performance of a Ti:sapphire laser pumped by a single 461 nm laser diode is presented for both the continuous-wave and the mode-locked regimes of operation. We introduce a simple astigmatism correction scheme for the laser diode beam consisting of two cylindrical lenses affecting the pump beam along the fast axis of the laser diode, which provides the mode-matching between the nearly square-shaped pump beam and the cavity mode. The resulting efficiency of the suggested Ti:Sapphire oscillator pumped by such a laser diode is analyzed for the Ti:sapphire crystals of 3 mm, 5 mm and 10 mm in length. We demonstrate that such a system provides the generation of ultrashort pulses up to 15 fs in duration with the repetition rate of 87 MHz, the average power being 170 mW.
High Bandwidth-Efficiency Resonant Cavity Enhanced Schottky Photodiodes for 800-850 nm Wavelength Operation

DTIC Science & Technology

1998-05-25

at least 50 nm wide centered around 830 nm wavelength. The layers are grown by molecular beam epitaxy on a semi- insulating GaAs substrate. The...limited by the material properties. With the advent of GaAs vertical-cavity surface-emitting lasers ~ VCSEL !,2 the 800–850 nm wavelength range has recently

Morphological effects of nanosecond- and femtosecond-pulsed laser ablation on human middle ear ossicles

NASA Astrophysics Data System (ADS)

Ilgner, Justus F.; Wehner, Martin; Lorenzen, Johann; Bovi, Manfred; Westhofen, Martin

2004-07-01

Introduction: Since the early 1980's, a considerable number of different laser systems have been introduced into reconstructive middle ear surgery. Depending on the ablation mode, however, pressure transients or thermal load to inner ear structures continue to be subject to discussion. Material and methods: We examined single spot ablations by a nanosecond-pulsed, frequency-tripled Nd:YAG-Laser (355 nm, beam diameter 10 μm, pulse rate 2 kHz, power 250 mW) on isolated human mallei. In a second set-up, a similar system (355 nm, beam diameter 20 μm, pulse rate 10 kHz, power 160-1500 mW) was coupled to a scanner to examine the morphology of bone surface ablation over an area of 1mm2. A third set-up employed a femtosecond-pulsed CrLiSAF-Oscillator (850 nm, pulse duration 100 fs, pulse energy 40μJ, beam diameter 36 μm, pulse rate 1 kHz) to compare these results with the former and with those obtained from a commercially available Er:YAG laser for ear surgery (Zeiss ORL E, 2940 nm, single pulse, energy 10-25 mJ). Results: In set-up 1 and 2, thermal effects in terms of marginal carbonization were visible in all single spot ablations of 1 s and longer. With ablations of 0.5 seconds, precise cutting margins with preservation of surrounding tissue could be observed. Cooling with saline solution resulted in no carbonization at 1500 mW and a scan speed of 500 mm/s. Set-up 3 equally showed no carbonization, although scanning times were longer and ablation less pronounced. Conclusion: Ultrashort pulsed laser systems could potentially aid further refinement of reconstructive microsurgery of the middle ear.
Polarization-independent broadband dielectric bilayer gratings for spectral beam combining system

NASA Astrophysics Data System (ADS)

Li, Linxin; Liu, Quan; Chen, Junming; Wang, Leilei; Jin, Yunxia; Yang, Yifeng; Shao, Jianda

2017-02-01

We report on a polarization-independent all-dielectric trapezoidal bilayer grating with broadband and high diffraction efficiency. The bilayer trapezoidal grating ridge on a reflector consists of an HfO2 layer and a SiO2 layer. The theoretical -1st order efficiencies of the grating are more than 95% with wavelength range from 1010 nm to 1080 nm for both TE and TM polarizations. The fabrication tolerances depending on the HfO2 and SiO2 layer grating ridge depths are enough to obtain the designed grating using current craft. The fabricated grating with exceeding 94% efficiency from 1000 nm to 1085 nm measured by a non-polarization laser has been fabricated and applied in a spectral beam combining external cavity to combine eight beams into one beam output with 10.77 kW.
Detection-gap-independent optical sensor design using divergence-beam-controlled slit lasers for wearable devices

NASA Astrophysics Data System (ADS)

Yoon, Young Zoon; Kim, Hyochul; Park, Yeonsang; Kim, Jineun; Lee, Min Kyung; Kim, Un Jeong; Roh, Young-Geun; Hwang, Sung Woo

2016-09-01

Wearable devices often employ optical sensors, such as photoplethysmography sensors, for detecting heart rates or other biochemical factors. Pulse waveforms, rather than simply detecting heartbeats, can clarify arterial conditions. However, most optical sensor designs require close skin contact to reduce power consumption while obtaining good quality signals without distortion. We have designed a detection-gap-independent optical sensor array using divergence-beam-controlled slit lasers and distributed photodiodes in a pulse-detection device wearable over the wrist's radial artery. It achieves high biosignal quality and low power consumption. The top surface of a vertical-cavity surface-emitting laser of 850 nm wavelength was covered by Au film with an open slit of width between 500 nm and 1500 nm, which generated laser emissions across a large divergence angle along an axis orthogonal to the slit direction. The sensing coverage of the slit laser diode (LD) marks a 50% improvement over nonslit LD sensor coverage. The slit LD sensor consumes 100% more input power than the nonslit LD sensor to obtain similar optical output power. The slit laser sensor showed intermediate performance between LD and light-emitting diode sensors. Thus, designing sensors with multiple-slit LD arrays can provide useful and convenient ways for incorporating optical sensors in wrist-wearable devices.
Comparison of Alexandrite and Diode Lasers for Hair Removal in Dark and Medium Skin: Which is Better?

PubMed

Mustafa, Farhad Hamad; Jaafar, Mohamad Suhimi; Ismail, Asaad Hamid; Mutter, Kussay Nugamesh

2014-01-01

To improve laser hair removal (LHR) for dark skin, the fluence rate reaching the hair follicle in LHR is important. This paper presents the results of a comparative study examining the function of wavelength on dark skin types using 755 nm alexandrite and 810 nm diode lasers. The structure of the skin was created using a realistic skin model by the Advanced Systems Analysis Program. In this study, the alexandrite laser (755 nm) and diode laser (810 nm) beam-skin tissue interactions were simulated. The simulation results for both lasers differed. The transmission ratio of the diode laser to the dark skin dermis was approximately 4% more than that of the alexandrite laser for the same skin type. For the diode laser at skin depth z = 0.67 mm, the average transmission ratios of both samples were 36% and 27.5%, but those for the alexandrite laser at the same skin depth were 32% and 25%. Both lasers were suitable in LHR for dark skin types, but the diode laser was better than the alexandrite laser because the former could penetrate deeper into the dermis layer.
Design of laser afocal zoom expander system

NASA Astrophysics Data System (ADS)

Jiang, Lian; Zeng, Chun-Mei; Hu, Tian-Tian

2018-01-01

Laser afocal zoom expander system due to the beam diameter variable, can be used in the light sheet illumination microscope to observe the samples of different sizes. Based on the principle of afocal zoom system, the laser collimation and beam expander system with a total length of less than 110mm, 6 pieces of spherical lens and a beam expander ratio of 10 is designed by using Zemax software. The system is focused on laser with a wavelength of 532nm, divergence angle of less than 4mrad and incident diameter of 4mm. With the combination of 6 spherical lens, the beam divergence angle is 0.4mrad at the maximum magnification ratio, and the RMS values at different rates are less than λ/4. This design is simple in structure and easy to process and adjust. It has certain practical value.
In-band-pumped Ho:KLu(WO4)2 microchip laser with 84% slope efficiency.

PubMed

Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Yumashev, Konstantin; Kuleshov, Nikolai; Petrov, Valentin; Griebner, Uwe; Aguiló, Magdalena; Díaz, Francesc

2015-02-01

We report on a continuous-wave Ho:KLu(WO4)2 (KLuW) microchip laser with a record slope efficiency of 84%, the highest value among the holmium inband-pumped lasers, delivering 201 mW output power at 2105 nm. The Ho laser operating at room temperature on the (5)I8→(5)I7 transition is in-band-pumped by a diode-pumped Tm:KLuW microchip laser at 1946 nm. Ho:KLuW laser operation at 2061 and 2079 nm is also demonstrated with a maximum slope efficiency of 79%. The microchip laser generates an almost diffraction-limited output beam with a Gaussian profile and a M2<1.1. The laser performance of the Ng-cut Ho:KLuW crystal is very similar for pump light polarizations ‖Nm and Np. The positive thermal lens plays a key role in the laser mode stabilization and proper mode-matching. The latter, together with the low quantum defect under in-band-pumping (∼0.08), is responsible for the extraordinary high slope efficiency.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Rakhman, A.; Hafez, Mohamed A.; Nanda, Sirish K.

Here, 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 enhancementmore » 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 1.0 GeV and 50 μA.« less
Continuous-wave laser operation at 743 and 753 nm based on a diode-pumped c-cut Pr:YAlO3 crystal

NASA Astrophysics Data System (ADS)

Lin, Xiuji; Huang, Xiaoxu; Liu, Bin; Xu, Bin; Xu, Huiying; Cai, Zhiping; Xu, Xiaodong; Li, Dongzhen; Liu, Jian; Xu, Jun

2018-02-01

We report on blue-diode-pumped continuous-wave Pr:YAlO3 (YAP) crystal lasers. Using a b-cut sample, a maximum output power of 181 mW is achieved at ∼747 nm with slope efficiency of 12.7% with respect to the absorbed power. Using a c-cut sample, a dual-wavelength laser at ∼743 and ∼753 nm is obtained with a total maximum output power of 72 mW by using the blue diode pumping, for the first time to our knowledge. These laser emissions are all linearly polarized and M2 factors of these output laser beams are also measured. YAP is experimentally verified to be one of effective oxide hosts for Pr-doped visible laser operation besides its fluoride counterparts.
How the stiffness of the optical trap depends on the proximity of the dielectric interface

NASA Astrophysics Data System (ADS)

Jákl, Petr; Šerý, Mojmír; Liška, Miroslav; Zemánek, Pavel

2005-09-01

When a probe confined in a single focused laser beam approaches the surface, it is getting more influenced by the retroreflected beam. This beam interferes with the incident one and a weak standing wave (SW) is created, which slightly modulates the incident beam. We studied experimentally how this phenomena influences the optical trap properties if SW is created using surfaces of two different reflectivities. We used polystyrene probes of diameters 690 nm and 820 nm, tracked their positions with quadrant photodiode (QPD) and analysed their thermal motion to get the axial trap stiffness along optical axis.
Compact beam transport system for free-electron lasers driven by a laser plasma accelerator

DOE PAGES

Liu, Tao; Zhang, Tong; Wang, Dong; ...

2017-02-01

Utilizing laser-driven plasma accelerators (LPAs) as a high-quality electron beam source is a promising approach to significantly downsize the x-ray free-electron laser (XFEL) facility. A multi-GeV LPA beam can be generated in several-centimeter acceleration distance, with a high peak current and a low transverse emittance, which will considerably benefit a compact FEL design. However, the large initial angular divergence and energy spread make it challenging to transport the beam and realize FEL radiation. In this paper, a novel design of beam transport system is proposed to maintain the superior features of the LPA beam and a transverse gradient undulator (TGU)more » is also adopted as an effective energy spread compensator to generate high-brilliance FEL radiation. As a result, theoretical analysis and numerical simulations are presented based on a demonstration experiment with an electron energy of 380 MeV and a radiation wavelength of 30 nm.« less
Investigation of Ag, Al2O3 and TiO2 nanoparticles effects as impurities in Laser Induced Breakdown in distilled water

NASA Astrophysics Data System (ADS)

Mahdieh, Mohammad Hossein; Akbari Jafarabadi, Marzieh; Safari Syahkal, Mehran; Mozaffari, Hossein

2017-08-01

In this paper, laser induced optical breakdown in colloidal nanoparticles was studied by using pump- probe beam technique. Colloidal nanoparticles of Ag (as a good conductor), Al2O3 and TiO2 (with good dielectric properties) were used in this investigation. The optical breakdown was induced by an Nd:YAG laser beam (operating at 1064 nm with pulse duration ∼30 ns). A small portion of the beam was taken by an optical splitter and used as probe beam. The time varying transmission of the probe beam transversely through the plasma was measured during the breakdown process. According to the results, the nanoparticles characteristics and pump beam intensity have significant influence in the breakdown process. Our results also show dissimilar dynamic behaviors for conductor and dielectric nanoparticles at different pump intensity. The results are useful for nanoparticle synthesis by laser ablation in distilled water in which the optical breakdown intensity threshold of ambient water influenced by generated nanoparticles.
Influence of wave-front curvature on supercontinuum energy during filamentation of femtosecond laser pulses in water

NASA Astrophysics Data System (ADS)

Potemkin, F. V.; Mareev, E. I.; Smetanina, E. O.

2018-03-01

We demonstrate that using spatially divergent incident femtosecond 1240-nm laser pulses in water leads to an efficient supercontinuum generation in filaments. Optimal conditions were found when the focal plane is placed 100 -400 μ m before the water surface. Under sufficiently weak focusing conditions [numerical aperture (NA )<0.2 ] and low-energy laser pulses, the supercontinuum energy generated in divergent beams is higher than the supercontinuum energy generated in convergent beams. Analysis by means of the unidirectional pulse propagation equation shows a dramatic difference between filamentation scenarios of divergent and convergent beams, that explains corresponding features of the supercontinuum generation. Under strong focusing conditions (NA ⩾0.2 ) and high-energy laser pulses, the supercontinuum generation is suppressed for convergent beams in contrast to divergent beams that nevertheless are shown experimentally to allow supercontinuum generation. The presented technique of the supercontinuum generation in divergent beams in water is highly demanded in a development of femtosecond optical parametric amplifiers.
Simulation of laser propagation through a three-layer human skin model in the spectral range from 1000 to 1900 nm.

PubMed

Nasouri, Babak; Murphy, Thomas E; Berberoglu, Halil

2014-01-01

For understanding the mechanisms of low-level laser/light therapy (LLLT), accurate knowledge of light interaction with tissue is necessary. We present a three-dimensional, multilayer reduced-variance Monte Carlo simulation tool for studying light penetration and absorption in human skin. Local profiles of light penetration and volumetric absorption were calculated for uniform as well as Gaussian profile beams with different spreads over the spectral range from 1000 to 1900 nm. The results showed that lasers within this wavelength range could be used to effectively and safely deliver energy to specific skin layers as well as achieve large penetration depths for treating deep tissues, without causing skin damage. In addition, by changing the beam profile from uniform to Gaussian, the local volumetric dosage could increase as much as three times for otherwise similar lasers. We expect that this tool along with the results presented will aid researchers in selecting wavelength and laser power in LLLT.
Remote air lasing for trace detection

NASA Astrophysics Data System (ADS)

Dogariu, Arthur; Michael, James B.; Miles, Richard B.

2011-05-01

We demonstrate coherent light propagating backwards from a remotely generated high gain air laser. A short ultraviolet laser pulse tuned to a two-photon atomic oxygen electronic resonance at 226 nm simultaneously dissociates the oxygen molecules in air and excites the resulting atomic oxygen fragments. Due to the focal depth of the pumping laser, a millimeter long region of high gain is created in air for the atomic oxygen stimulated emission at 845nm. We demonstrate that the gain in excess of 60 cm-1 is responsible for both forward and backwards emission of a strong, collimated, coherent laser beam. We present evidence for coherent emission and characterize the backscattered laser beam while varying the pumping conditions. The optical gain and directional emission allows for six orders of magnitude enhancement for the backscattered emission when compared with the fluorescence emission collected into the same solid angle. . This opens new opportunities for the remote detection capabilities of trace species, and provides much greater range for the detection of optical molecular and atomic features from a distant target.
Infrared skin damage thresholds from 1319-nm continuous-wave laser exposures

NASA Astrophysics Data System (ADS)

Oliver, Jeffrey W.; Vincelette, Rebecca; Noojin, Gary D.; Clark, Clifton D.; Harbert, Corey A.; Schuster, Kurt J.; Shingledecker, Aurora D.; Kumru, Semih S.; Maughan, Justin; Kitzis, Naomi; Buffington, Gavin D.; Stolarski, David J.; Thomas, Robert J.

2013-12-01

A series of experiments were conducted in vivo using Yucatan miniature pigs (Sus scrofa domestica) to determine thermal damage thresholds to the skin from 1319-nm continuous-wave Nd:YAG laser irradiation. Experiments employed exposure durations of 0.25, 1.0, 2.5, and 10 s and beam diameters of ˜0.6 and 1 cm. Thermal imagery data provided a time-dependent surface temperature response from the laser. A damage endpoint of fifty percent probability of a minimally visible effect was used to determine threshold for damage at 1 and 24 h postexposure. Predicted thermal response and damage thresholds are compared with a numerical model of optical-thermal interaction. Resultant trends with respect to exposure duration and beam diameter are compared with current standardized exposure limits for laser safety. Mathematical modeling agreed well with experimental data, predicting that though laser safety standards are sufficient for exposures <10 s, they may become less safe for very long exposures.
Simulation of laser propagation through a three-layer human skin model in the spectral range from 1000 to 1900 nm

NASA Astrophysics Data System (ADS)

Nasouri, Babak; Murphy, Thomas E.; Berberoglu, Halil

2014-07-01

For understanding the mechanisms of low-level laser/light therapy (LLLT), accurate knowledge of light interaction with tissue is necessary. We present a three-dimensional, multilayer reduced-variance Monte Carlo simulation tool for studying light penetration and absorption in human skin. Local profiles of light penetration and volumetric absorption were calculated for uniform as well as Gaussian profile beams with different spreads over the spectral range from 1000 to 1900 nm. The results showed that lasers within this wavelength range could be used to effectively and safely deliver energy to specific skin layers as well as achieve large penetration depths for treating deep tissues, without causing skin damage. In addition, by changing the beam profile from uniform to Gaussian, the local volumetric dosage could increase as much as three times for otherwise similar lasers. We expect that this tool along with the results presented will aid researchers in selecting wavelength and laser power in LLLT.
A fundamental mode Nd:GdVO4 laser pumped by a large aperture 808 nm VCSEL

NASA Astrophysics Data System (ADS)

Hao, Y. Q.; Ma, J. L.; Yan, C. L.; Liu, G. J.; Ma, X. H.; Gong, J. F.; Feng, Y.; Wei, Z. P.; Wang, Y. X.; Zhao, Y. J.

2013-05-01

A fundamental mode Nd:GdVO4 laser pumped by a vertical cavity surface emitting laser (VCSEL) is experimentally demonstrated. The VCSEL has a circular output-beam which makes it easier for it to be directly coupled to a Nd:GdVO4 microcrystal. In our research, a large aperture 808 nm VCSEL, with a multi-ring-shaped aperture (MRSA) and an almost Gaussian-shaped far-field profile, is used as the pumping source. Experimental results for the Nd:GdVO4 laser pumped by the VCSEL are presented. The maximum output peak power of 0.754 W is obtained under a pump peak power of 1.3 W, and the corresponding opto-optic conversion efficiency is 58.1%. The average slope efficiency is 65.8% from the threshold pump power of 0.2 W to the pump power of 1.3 W. The laser beam quality factors are measured to be {M}x2=1.2 0 and {M}y2=1.1 5.
Characterization of laser induced damage of HR coatings with picosecond pulses

NASA Astrophysics Data System (ADS)

Li, Cheng; Zhao, Yuan'an; Cui, Yun; Wang, Yueliang; Peng, Xiaocong; Shan, Chong; Zhu, Meiping; Wang, Jianguo; Shao, Jianda

2017-11-01

The effect of protective layer on the picosecond laser-induced damage behaviors of HfO2/SiO2 high-reflective (HR) coatings are explored. Two kinds of 1064nm HR coatings with and without protective layer are deposited by electron beam evaporation. Laser-induced damage tests are conducted with 1064nm, 30ps S-polarized and P-polarized pulses with different angle of incidence (AOI) to make the electric fields intensity in the HR coatings discrepantly. Damage morphology and cross section of damage sites were characterized by scanning electron microscope (SEM) and focused ion beam (FIB), respectively. It is found that SiO2 protective layer have a certain degree of improvement on laser induced damage threshold (LIDT) for every AOIs. The onset damage initiated very near to the Max peak of e-field, after which forms ripple-like pits. The damage morphology presents as layer delamination at high fluence. The Laser damage resistance is correspond with the maximum E-intensity in the coating stacks.
Single-mode large-mode-area laser fiber with ultralow numerical aperture and high beam quality.

PubMed

Peng, Kun; Zhan, Huan; Ni, Li; Wang, Xiaolong; Wang, Yuying; Gao, Cong; Li, Yuwei; Wang, Jianjun; Jing, Feng; Lin, Aoxiang

2016-12-10

By using the chelate precursor doping technique, we report on an ytterbium-doped aluminophosphosilicate (APS) large-mode-area fiber with ultralow numerical aperture of 0.036 and effective fundamental mode area of ∼550 μm². With a bend diameter of 600 mm, the bending loss of fundamental mode LP₀₁ was measured to be <10^-3 dB/m, in agreement with the corresponding simulation results, while that of higher order mode LP₁₁ is >100 dB/m at 1080 nm. Measured in an all-fiber oscillator laser cavity, 592 W single-mode laser output was obtained at 1079.64 nm with high-beam quality M² of 1.12. The results indicate that the chelate precursor doping technique is a competitive method for ultralow numerical aperture fiber fabrication, which is very suitable for developing single-mode seed lasers for high power laser systems.
Short-wavelength ablation of polymers in the high-fluence regime

NASA Astrophysics Data System (ADS)

Liberatore, Chiara; Mann, Klaus; Müller, Matthias; Pina, Ladislav; Juha, Libor; Vyšín, Ludek; Rocca, Jorge J.; Endo, Akira; Mocek, Tomas

2014-05-01

Short-wavelength ablation of poly(1,4-phenylene ether-ether-sulfone) (PPEES) and poly(methyl methacrylate) (PMMA) was investigated using extreme ultraviolet (XUV) and soft x-ray (SXR) radiation from plasma-based sources. The initial experiment was performed with a 10 Hz desktop capillary-discharge XUV laser lasing at 46.9 nm. The XUV laser beam was focused onto the sample by a spherical mirror coated with a Si/Sc multilayer. The same materials were irradiated with 13.5 nm radiation emitted by plasmas produced by focusing an optical laser beam onto a xenon gas-puff target. A Schwarzschild focusing optics coated with a Mo/Si multilayer was installed at the source to achieve energy densities exceeding 0.1 J cm-2 in the tight focus. The existing experimental system at the Laser Laboratorium Göttingen was upgraded by implementing a 1.2 J driving laser. An increase of the SXR fluence was secured by improving the alignment technique.

Detection and counting of a submicrometer particle in liquid flow by self-mixing microchip Yb:YAG laser velocimetry.

PubMed

Ohtomo, Takayuki; Sudo, Seiichi; Otsuka, Kenju

2016-09-20

We observed intermittent modulation by scattered light from a single submicrometer particle moving in the flow channel using a self-mixing microchip Yb:YAG laser Doppler velocimeter (LDV) under lateral beam access. The Doppler-shift frequency chirping (i.e., velocity change) was identified in accordance with a particle passage through the beam focus. Single particle counting, which obeys the Poisson distribution, was performed successfully over a long period of time. The experimental results have been reproduced by a numerical simulation. The LDV signal was increased over 20 dB for a 202-nm particle without chirping by collinear beam access with the laser beam axis aligned along the flow direction.
1-kW monolithic narrow linewidth linear-polarized fiber laser at 1030 nm

NASA Astrophysics Data System (ADS)

Xu, Yang; Fang, Qiang; Cui, Xuelong; Hou, Bowen; Fu, Shijie; Xie, Zhaoxin; Shi, Wei

2018-02-01

We demonstrate an all-fiberized, linear-polarized, narrow spectral linewidth laser system with kilowatts-level output power at 1030 nm in master oscillator-power amplifier (MOPA) configuration. The laser system consists of a linear-polarized, narrow linewidth ( 28 GHz) fiber laser oscillator and two stages of linear-polarized fiber amplifiers. A 925 W linear-polarized fiber laser with a polarization extinction ratio (PER) of 15.2 dB and a spectral width of 60 GHz at the central wavelength of 1030.1 nm is achieved. Owing to the setting of the appropriate parameters for the laser, no indication of Stimulate Brillouin Scattering (SBS) is observed in the system. Moreover, thanks to the excellent quantum efficiency of the laser and the thightly coiling of the active fiber in the main amplifier, the mode instability (MI) is successfully avoided. As a result, the near diffraction-limited beam quality (M2<1.3) is achieved.
High-Power Nd:GdVO4 Innoslab Continuous-Wave Laser under Direct 880 nm Pumping

NASA Astrophysics Data System (ADS)

Deng, Bo; Zhang, Heng-Li; Xu, Liu; Mao, Ye-Fei; He, Jing-Liang; Xin, Jian-Guo

2014-11-01

A high-power cw end-pumped laser device is demonstrated with a slab crystal of Nd:GdVO4 operating at 1063 nm. Diode laser stacks at 880 nm are used to pump Nd:GdVO4 into emitting level 4F3/2. The 149 W output power is presented when the absorbed pump power is 390 W and the optical-to-optical conversion efficiency is 38.2%. When the output power is 120 W, the M2 factors are 2.3 in both directions. Additionally, mode overlap inside the resonator is analyzed to explain the beam quality deterioration.
A novel DWDM method to design a 100-kW Laser

NASA Astrophysics Data System (ADS)

Basu, Santanu

2010-02-01

In this paper, I will present the design analysis of a novel concept that may be used to generate a diffraction-limited beam from an aperture so that as much as 450 kW of laser power can be efficiently deposited on a diffraction-limited spot at a range. The laser beam will be comprised of many closely spaced wavelength channels as in a DWDM. The technique relies on the ability of an angular dispersion amplifier to multiplex a large number of high power narrow frequency lasers, wavelengths of which may be as close as 0.4 nm.
Thulium fiber laser for the use in low-invasive endoscopic and robotic surgery of soft biological tissues

NASA Astrophysics Data System (ADS)

Michalska, M.; Brojek, W.; Rybak, Z.; Sznelewski, P.; Mamajek, M.; Gogler, S.; Swiderski, J.

2016-12-01

An all-fiber, diode-pumped, continuous-wave Tm3+-doped fiber laser operated at a wavelength of 1.94 μm was developed. 37.4 W of output power with a slope efficiency as high as 57% with respect to absorbed pump power at 790 nm was demonstrated. The laser output beam quality factor M2 was measured to be 1.2. The output beam was very stable with power fluctuations <1% measured over 1 hour. The laser system is to be implemented as a scalpel for surgery of soft biological tissues.
Updated LPI Thresholds for the Nike Laser*

NASA Astrophysics Data System (ADS)

Weaver, J. L.; Oh, J.; Afeyan, B.; Phillips, L.; Seely, J.; Kehne, D.; Brown, C.; Obenschain, S. P.; Serlin, V.; Schmitt, A. J.; Feldman, U.; Holland, G.; Manka, C.; Lehmberg, R. H.; McLean, E.

2009-11-01

Advanced implosion designs for direct drive inertial confinement fusion use high laser intensities (10^15-10^16 W/cm^2) to achieve gain (g>100) with a reduction in total laser energy (E<1 MJ). Krypton-fluoride lasers such as the Nike laser at NRL are an attractive choice due to their combination of short wavelength (248 nm), large bandwidth (1-2 THz), and beam smoothing by induced spatial incoherence but the potential threat from laser-plasma instabilities (LPI) needs to be assessed. The 2008 LPI campaign at Nike yielded threshold intensities above 10^15 W/cm^2 for the two-plasmon instability, a value higher than reported for 351 nm glass lasers. The experiments used a planar geometry, solid polystyrene targets, and a subset of beams (E<200 J) with a reduced focal spot (d<125 μm). The 2009 campaign extended the shot parameters to higher laser energies (E<1 kJ) and larger spot sizes (d<300 μm). Spectrally-resolved and time-resolved measurements of x-rays and emission near ^1/2φo and ^3/2φo harmonics of the laser wavelength show threshold intensities consistent with the 2008 results. *Work supported by DoE/NNSA
Enhancing hair follicle regeneration by nonablative fractional laser: Assessment of irradiation parameters and tissue response.

PubMed

Wu, Yueh-Feng; Wang, Shiou-Han; Wu, Pei-Shan; Fan, Sabrina Mai-Yi; Chiu, Hsien-Yi; Tsai, Tsung-Hua; Lin, Sung-Jan

2015-04-01

Identification of methods to enhance anagen entry can be helpful for alopecia. Recently, nonablative laser has been proposed as a potential treatment for alopecia. However, how the laser parameters affect stem cell activity, hair cycles and the associated side effects have not been well characterized. Here we examine the effects of irradiation parameters of 1,550-nm fractional laser on hair cycles. The dorsal skin of eight-week-old female C57BL/6 mice with hair follicles in synchronized telogen was shaved and irradiated with a 1,550-nm fractional erbium-glass laser (Fraxel RE:STORE (SR1500) Laser System, Solta Medical, U.S.A.) with varied beam energies (5-35 mJ) and beam densities (500-3500 microthermal zones/cm(2) ). The cutaneous changes were evaluated both grossly and histologically. Hair follicle stem cell activity was detected by BrdU incorporation and changes in gene expression were quantified by real-time PCR. Direct thermal injury to hair follicles could be observed early after irradiation, especially at higher beam energy. Anagen induction in the irradiated skin showed an all-or-non change. Anagen induction and ulcer formation were affected by the combination of beam energy and density. The lowest beam energy of 5 mJ failed to promote anagen entry at all beam densities tested. As beam energy increased from 10 mJ to 35 mJ, we found a decreasing trend of beam density that could induce anagen entry within 7-9 days with activation of hair follicle stem cells. Beam density above the pro-regeneration density could lead to ulcers and scarring followed by anagen entry in adjacent skin. Analysis of inflammatory cytokines, including TNF-α, IL-1β, and IL-6, revealed that transient moderate inflammation was associated with anagen induction and intense prolonged inflammation preceded ulcer formation. To avoid side effects of hair follicle injury and scarring, appropriate combination of beam energy and density is required. Parameters outside the therapeutic window can result in either no anagen promotion or ulcer formation. © 2015 Wiley Periodicals, Inc.
Novel, compact, and simple ND:YVO4 laser with 12 W of CW optical output power and good beam quality

NASA Astrophysics Data System (ADS)

Zimer, H.; Langer, B.; Wittrock, U.; Heine, F.; Hildebrandt, U.; Seel, S.; Lange, R.

2017-11-01

We present first, promising experiments with a novel, compact and simple Nd:YVO4 slab laser with 12 W of 1.06 μm optical output power and a beam quality factor M2 2.5. The laser is made of a diffusion-bonded YVO4/Nd:YVO4 composite crystal that exhibits two unique features. First, it ensures a one-dimensional heat removal from the laser crystal, which leads to a temperature profile without detrimental influence on the laser beam. Thus, the induced thermo-optical aberrations to the laser field are low, allowing power scaling with good beam quality. Second, the composite crystal itself acts as a waveguide for the 809 nm pump-light that is supplied from a diode laser bar. Pump-light shaping optics, e.g. fast- or slow-axis collimators can be omitted, reducing the complexity of the system. Pump-light redundancy can be easily achieved. Eventually, the investigated slab laser might be suitable for distortion-free high gain amplification of weak optical signals.
Frequency locking of compact laser-diode modules at 633 nm

NASA Astrophysics Data System (ADS)

Nölleke, Christian; Leisching, Patrick; Blume, Gunnar; Jedrzejczyk, Daniel; Pohl, Johannes; Feise, David; Sahm, Alexander; Paschke, Katrin

2018-02-01

This work reports on a compact diode-laser module emitting at 633 nm. The emission frequency can be tuned with temperature and current, while optical feedback of an internal DBR grating ensures single-mode operation. The laser diode is integrated into a micro-fabricated package, which includes optics for beam shaping, a miniaturized optical isolator, and a vapor cell as frequency reference. The achieved absolute frequency stability is below 10-8 , while the output power can be more than 10 mW. This compact absolute frequency-stabilized laser system can replace gas lasers and may be integrated in future quantum technology devices.
Improving the Reliability and Modal Stability of High Power 870 nm AlGaAs CSP Laser Diodes for Applications to Free Space Communication Systems

NASA Technical Reports Server (NTRS)

Connolly, J. C.; Alphonse, G. A.; Carlin, D. B.; Ettenberg, M.

1991-01-01

The operating characteristics (power-current, beam divergence, etc.) and reliability assessment of high-power CSP lasers is discussed. The emission wavelength of these lasers was optimized at 860 to 880 nm. The operational characteristics of a new laser, the inverse channel substrate planar (ICSP) laser, grown by metalorganic chemical vapor deposition (MOCVD), is discussed and the reliability assessment of this laser is reported. The highlights of this study include a reduction in the threshold current value for the laser to 15 mA and a degradation rate of less than 2 kW/hr for the lasers operating at 60 mW of peak output power.
The influence of femtosecond laser pulse wavelength on embryonic stem cell differentiation

NASA Astrophysics Data System (ADS)

Mthunzi, Patience

2012-10-01

Stem cells are rich in proteins, carbohydrates, deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and various other cellular components which are responsible for a diversity of functions. Mostly the building blocks of these intracellular entities play an active role in absorbing ultra-violet (UV) and visible light sources. Light-matter interactions in biomaterials are a complex situation and subsequent damage may not always amount only from wavelength dependent effects but may also be driven by a wealth of other optical parameters which may lead to a variety photochemical reactions. Previously, literature has reported efficient photo-transfection and differentiation of pluripotent stem cells via near infrared (NIR) femtosecond (fs) laser pulses with minimum compromise to their viability. Therefore, in this study the influence of using different fs laser wavelengths on optical stem cell transfection and differentiation is investigated. A potassium titanyl phosphate (KTP) crystal was employed in frequency doubling a 1064 nm fs laser beam. The newly generated 532 nm fs pulsed beam was then utilized for the first time in transient photo-transfection of ES-E14TG2a mouse embryonic stem (mES) cells. Compared to using 1064 nm fs pulses which non-invasively introduce plasmid DNA and other macromolecules into mES cells, our results showed a significant decline in the photo-transfection efficiency following transfecting with a pulsed fs visible green beam.
EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA Annealing of induced absorption in quartz glasses by ArF laser radiation

NASA Astrophysics Data System (ADS)

Sergeev, P. B.; Sergeev, A. P.

2010-11-01

Annealing of individual bands of electron-beam-induced absorption (IA) in the region of 150 — 400 nm in KS-4V, KU-1, and Corning 7980 (ArF Grade) quartz glasses by ArF laser radiation is studied. It is shown that the phototransformation of the IA spectra occurs mainly due to a significant decrease in the amplitudes of bands at λ = 183.5, 213, and 260 nm. The role played by interstitial oxygen, hydrogen, and chlorine in the formation and relaxation of glass defects is considered.
Single-mode oscillation of a diode-pumped Nd:YAG microchip laser at 1835 nm

NASA Astrophysics Data System (ADS)

Lan, Jinglong; Cui, Qin; Wang, Yi; Xu, Bin; Xu, Huiying; Cai, Zhiping

2016-10-01

Single-mode oscillation of a diode-pumped conventional Nd:YAG laser at 1835 nm is demonstrated, for the first time to our knowledge, in the form of microchip configuration. The achieved maximum output power reaches 189 mW with slope efficiency of about 5.5% with respect to absorbed pump power. The laser spectra are measured with linewidth less than 0.08 nm indicating a single longitudinal mode. The output laser beam is also measured to be near diffraction-limited with M2 factors of about 1.2 and 1.5 in x and y directions. Using a mechanical chopper with 50% duty cycle, the maximum output power is improved to 253 mW with slope efficiency of about 9.7%.
Design and fabrication of a high-precision cylinder beam expander

NASA Astrophysics Data System (ADS)

Zhang, Yong-hong; Yan, Hong; Xie, Bing; Li, Jian-ming; Luo, Zhong-xiang

2018-03-01

In order to compress the beam divergence angle and reduce the energy density, beam expansion system is widely used to expand the beam in laser system. Cylinder beam expander belongs to one-dimension expander, which expands the laser beam in only one direction (X direction or Y direction), a refraction cylinder expander whose beam diameter is 180mm×120mm and magnitude ratio is 12 is designed in this paper, the working wavelength is 1058nm. To solve the problem of inequality of the working wavelength and the testing wavelength, compensation method of using parallel plate to test the system aberration is proposed. By rough grinding (precision grinding) polish and the system grinding, the final system aberration is 0.24λ(peak-valley value)
Vortex operation in Er:LuYAG crystal laser at ∼1.6 μm

NASA Astrophysics Data System (ADS)

Liu, Qiyao; Zhao, Yongguang; Zhou, Wei; Shen, Deyuan

2017-09-01

An Er3+-doped Lu1.5Y1.5Al5O12 (Er:LuYAG) solid-state laser with direct generation of optical vortex is reported. The vortex laser operation was realized through being pumped by an annular beam at 1532 nm, which was reformatted by a specially fabricated optical mirror. With two different laser output couplers of 10% and 20% transmissions, pure LG01 mode lasers with right-handedness at 1647.7 nm and 1619.5 nm were yielded from a simple two-mirror cavity, respectively, without any helicity control optical element. Furthermore, stable pulse trains at 1647.7 nm have been achieved via employing an acousto-optic Q-switch, and ∼0.66 mJ pulsed energy and ∼65 ns pulse duration were finally obtained at 1 kHz repetition rate, corresponding to a peak power of ∼10.2 kW. The generated pulse vortex maintained LG01 mode with well-determined right-handedness, as in the case of cw laser operation.
Pulsed laser-induced damage of metals at 492 nm.

PubMed

Marrs, C D; Faith, W N; Dancy, J H; Porteus, J O

1982-11-15

A triaxial flashlamp-pumped dye laser has been used to perform laser damage testing of metal surfaces in the blue-green spectral region. Using LD490 laser dye, the laser produces 0.18-J, 0.5-microsec pulses at 492 nm. The spatial profile of the focused beam is measured in orthogonal directions in the plane of the sample surface. The orthogonal profiles are flat-topped Gaussians with 1/e(2) widths of 270 microm. Multithreshold laser damage test results are presented for polished Mo, diamond-turned high-purity Al alloy, diamond-turned bulk Cu, and diamond-turned electrodeposits of Ag and Au on Cu. Comparisons are made between calculated and experimentally measured slip and melt thresholds.
Design of 20 W fiber-coupled green laser diode by Zemax

NASA Astrophysics Data System (ADS)

Qi, Yunfei; Zhao, Pengfei; Wu, Yulong; Chen, Yongqi; Zou, Yonggang

2017-09-01

We represent a design of a 20 W, fiber-coupled diode laser module based on 26 single emitters at 520 nm. The module can produce more than 20 W output power from a standard fiber with core diameter of 400 μm and numerical aperture (NA) of 0.22. To achieve a 20 W laser beam, the spatial beam combination and polarization beam combination by polarization beam splitter are used to combine output of 26 single emitters into a single beam, and then an aspheric lens is used to couple the combined beam into an optical fiber. The simulation shows that the total coupling efficiency is more than 95%. Project supported by the National Key R& D Program of China (No. 2016YFB0402105), the Key Deployment Program of the Chinese Academy of Sciences (No. KGZD-SW-T01-2), and the National Natural Science Foundation of China (No. 61404135).
Bulk damage and absorption in fused silica due to high-power laser applications

NASA Astrophysics Data System (ADS)

Nürnberg, F.; Kühn, B.; Langner, A.; Altwein, M.; Schötz, G.; Takke, R.; Thomas, S.; Vydra, J.

2015-11-01

Laser fusion projects are heading for IR optics with high broadband transmission, high shock and temperature resistance, long laser durability, and best purity. For this application, fused silica is an excellent choice. The energy density threshold on IR laser optics is mainly influenced by the purity and homogeneity of the fused silica. The absorption behavior regarding the hydroxyl content was studied for various synthetic fused silica grades. The main absorption influenced by OH vibrational excitation leads to different IR attenuations for OH-rich and low-OH fused silica. Industrial laser systems aim for the maximum energy extraction possible. Heraeus Quarzglas developed an Yb-doped fused silica fiber to support this growing market. But the performance of laser welding and cutting systems is fundamentally limited by beam quality and stability of focus. Since absorption in the optical components of optical systems has a detrimental effect on the laser focus shift, the beam energy loss and the resulting heating has to be minimized both in the bulk materials and at the coated surfaces. In collaboration with a laser research institute, an optical finisher and end users, photo thermal absorption measurements on coated samples of different fused silica grades were performed to investigate the influence of basic material properties on the absorption level. High purity, synthetic fused silica is as well the material of choice for optical components designed for DUV applications (wavelength range 160 nm - 260 nm). For higher light intensities, e.g. provided by Excimer lasers, UV photons may generate defect centers that effect the optical properties during usage, resulting in an aging of the optical components (UV radiation damage). Powerful Excimer lasers require optical materials that can withstand photon energy close to the band gap and the high intensity of the short pulse length. The UV transmission loss is restricted to the DUV wavelength range below 300 nm and consists of three different absorption bands centered at 165 nm (peroxy radicals), 215 nm (E'-center), and 265 nm (non-bridging oxygen hole center (NBOH)), which change the transmission behavior of material.
Laser-drilled micro-hole arrays on polyurethane synthetic leather for improvement of water vapor permeability

NASA Astrophysics Data System (ADS)

Wu, Y.; Wang, A. H.; Zheng, R. R.; Tang, H. Q.; Qi, X. Y.; Ye, B.

2014-06-01

Three kinds of lasers at 1064, 532 and 355 nm wavelengths respectively were adopted to construct micro-hole arrays on polyurethane (PU) synthetic leather with an aim to improve water vapor permeability (WVP) of PU synthetic leather. The morphology of the laser-drilled micro-holes was observed to optimize laser parameters. The WVP and slit tear resistance of the laser-drilled leather were measured. Results show that the optimized pulse energy for the 1064, 532 and 355 nm lasers are 0.8, 1.1 and 0.26 mJ, respectively. The diameters of the micro-holes drilled with the optimized laser pulse energy were about 20, 15 and 10 μm, respectively. The depths of the micro-holes drilled with the optimized pulse energy were about 21, 60 and 69 μm, respectively. Compared with the untreated samples, the highest WVP growth ratio was 38.4%, 46.8% and 53.5% achieved by the 1064, 532 and 355 nm lasers, respectively. And the highest decreasing ratio of slit tear resistance was 11.1%, 14.8%, and 22.5% treated by the 1064, 532 and 355 nm lasers, respectively. Analysis of the interaction mechanism between laser beams at three kinds of laser wavelengths and the PU synthetic leather revealed that laser micro-drilling at 355 nm wavelength displayed both photochemical ablation and photothermal ablation, while laser micro-drilling at 1064 and 532 nm wavelengths leaded to photothermal ablation only.
Rapid heating of matter using high power lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bang, Woosuk

2016-04-08

This slide presentation describes motivation (uniform and rapid heating of a target, opportunity to study warm dense matter, study of nuclear fusion reactions), rapid heating of matter with intense laser-driven ion beams, visualization of the expanding warm dense gold and diamond, and nuclear fusion experiments using high power lasers (direct heating of deuterium spheres (radius ~ 10nm) with an intense laser pulse.

Formation of short high-power laser radiation pulses in excimer mediums

NASA Astrophysics Data System (ADS)

Losev, V. F., Sr.; Ivanov, N. G.; Panchenko, Yu. N.

2007-06-01

Presently an excimer mediums continue are examined as one of variants for formation of powerful and over powerful pulses of laser radiation with duration from units of nanosecond up to tens femtosecond. The researches on such powerful installations as "NIKE" (USA) and << SUPER ASHURA >>, Japan) proceed in this direction. The main advantage of excimer mediums is the opportunity to work in a frequency mode, absence of restriction on the size of active area, high uniformity of a gas working medium, high efficiency (up to 10 %) and wide spectral range of laser radiation (KrF, XeCl ~ 2nm, XeF (C-A), Xe IICl ~ 50-100 nanometers). Research in area of high quality laser beams formation in excimer mediums and its amplification in high power amplifiers are carried out the long time in Institute of High Current Electronics SB RAS, Tomsk, Russia. The wide aperture XeCl laser system of MELS-4k is used for these investigations. Last time we take part in program on development of high power excimer laser system with a petawatt level of power. This system supposes the formation and amplification high quality laser beams with different pulse duration from units of nanosecond up to tens femtosecond. We research the possibility of laser beams formation in excimer mediums with ps-ns pulse duration having the low noise and divergence near to diffraction limit. In other hand, we are developing the wide aperture XeF(C-A) amplifier with optical pump on base electron accelerator. According to our estimations of the XeF(C-A) amplifier based on the converter of e-beam energy to the Xe II* fluorescence at 172 nm will allow to obtain up to 100 TW peak power in a 30 fs pulse.
Power enhancement of burst-mode UV pulses using a doubly-resonant optical cavity

DOE PAGES

Rahkman, Abdurahim; Notcutt, Mark; Liu, Yun

2015-11-24

We report a doubly-resonant enhancement cavity (DREC) that can realize a simultaneous enhancement of two incoming laser beams at different wavelengths and different temporal structures. The double-resonance condition is theoretically analyzed and different DREC locking methods are experimentally investigated. Simultaneous locking of a Fabry-Perot cavity to both an infrared (IR, 1064 nm) and its frequency tripled ultraviolet (UV, 355 nm) pulses has been demonstrated by controlling the frequency difference between the two beams with a fiber optic frequency shifter. The DREC technique opens a new paradigm in the applications of optical cavities to power enhancement of burst-mode lasers with arbitrarymore » macropulse width and repetition rate.« less
Research on laser-removal of a deuterium deposit from a graphite sample

NASA Astrophysics Data System (ADS)

Kubkowska, M.; Skladnik-Sadowska, E.; Malinowski, K.; Sadowski, M. J.; Rosinski, M.; Gasior, P.

2014-04-01

The paper presents experimental results of investigation of a removal of deuterium deposits from a graphite target by means of pulsed laser beams. The sample was a part of the TEXTOR limiter with a deuterium-deposited layer. That target was located in the vacuum chamber, pumped out to 5×10-5 Torr, and it was irradiated with a Nd:YAG laser, which generated 3.5-ns pulses of energy of 0.5 J at λ1 = 1063 nm, or 0.1 J at λ3 = 355 nm.
Measuring evaporation rates of laser-trapped droplets by use of fluorescent morphology-dependent resonances.

PubMed

Pastel, R; Struthers, A

2001-05-20

Morphology-dependent resonances (MDRs) are used to measure accurately the evaporation rates of laser-trapped 1- to 2-mum droplets of ethylene glycol. Droplets containing 3 x 10(-5) M Rhodamine-590 laser dye are optically trapped in a 20-mum hollow fiber by two counterpropagating 150-mW, 800-nm laser beams. A weaker 532-nm laser excites the dye, and fluorescence emission is observed near 560 nm as the droplet evaporates. A complete series of first-order TE and TM MDRs dominates the fluorescent output. MDR mode identification sizes the droplets and provides accurate evaporation rates. We verify the automated MDR mode identification by counting fringes in a videotape of the experiment. The longitudinal spring constant of the trap, measured by analysis of the videotaped motion of droplets perturbed from the trap center, provides independent verification of the laser's intensity within the trap.
Measuring Evaporation Rates of Laser-Trapped Droplets by Use of Fluorescent Morphology-Dependent Resonances

NASA Astrophysics Data System (ADS)

Pastel, Robert; Struthers, Allan

2001-05-01

Morphology-dependent resonances (MDRs) are used to measure accurately the evaporation rates of laser-trapped 1- to 2- m droplets of ethylene glycol. Droplets containing 3 x10-5 M Rhodamine-590 laser dye are optically trapped in a 20- m hollow fiber by two counterpropagating 150-mW, 800-nm laser beams. A weaker 532-nm laser excites the dye, and fluorescence emission is observed near 560 nm as the droplet evaporates. A complete series of first-order TE and TM MDRs dominates the fluorescent output. MDR mode identification sizes the droplets and provides accurate evaporation rates. We verify the automated MDR mode identification by counting fringes in a videotape of the experiment. The longitudinal spring constant of the trap, measured by analysis of the videotaped motion of droplets perturbed from the trap center, provides independent verification of the laser s intensity within the trap.
Spectrally enhanced image resolution of tooth enamel surfaces

NASA Astrophysics Data System (ADS)

Zhang, Liang; Nelson, Leonard Y.; Berg, Joel H.; Seibel, Eric J.

2012-01-01

Short-wavelength 405 nm laser illumination of surface dental enamel using an ultrathin scanning fiber endoscope (SFE) produced enhanced detail of dental topography. The surfaces of human extracted teeth and artificial erosions were imaged with 405 nm, 444 nm, 532 nm, or 635 nm illumination lasers. The obtained images were then processed offline to compensate for any differences in the illumination beam diameters between the different lasers. Scattering and absorption coefficients for a Monte Carlo model of light propagation in dental enamel for 405 nm were scaled from published data at 532 nm and 633 nm. The value of the scattering coefficient used in the model was scaled from the coefficients at 532 nm and 633 nm by the inverse third power of wavelength. Simulations showed that the penetration depth of short-wavelength illumination is localized close to the enamel surface, while long-wavelength illumination travels much further and is backscattered from greater depths. Therefore, images obtained using short wavelength laser are not contaminated by the superposition of light reflected from enamel tissue at greater depths. Hence, the SFE with short-wavelength illumination may make it possible to visualize surface manifestations of phenomena such as demineralization, thus better aiding the clinician in the detection of early caries.
Design study of high gradient, low impedance accelerating structures for the FERMI free electron laser linac upgrade

NASA Astrophysics Data System (ADS)

Shafqat, N.; Di Mitri, S.; Serpico, C.; Nicastro, S.

2017-09-01

The FERMI free-electron laser (FEL) of Elettra Sincrotrone Trieste, Italy, is a user facility driven by a 1.5 GeV 10-50 Hz S-band radiofrequency linear accelerator (linac), and it is based on an external laser seeding scheme that allows lasing at the shortest fundamental wavelength of 4 nm. An increase of the beam energy to 1.8 GeV at a tolerable breakdown rate, and an improvement of the final beam quality is desired in order to allow either lasing at 4 nm with a higher flux, or lasing at shorter wavelengths. This article presents the impedance analysis of newly designed S-band accelerating structures, for replacement of the existing backward travelling wave structures (BTWS) in the last portion of the FERMI linac. The new structure design promises higher accelerating gradient and lower impedance than those of the existing BTWS. Particle tracking simulations show that, with the linac upgrade, the beam relative energy spread, its linear and nonlinear z-correlation internal to the bunch, and the beam transverse emittances can be made smaller than the ones in the present configuration, with expected advantage to the FEL performance. The repercussion of the upgrade on the linac quadrupole magnets setting, for a pre-determined electron beam optics, is also considered.
Surface modification of an amorphous Si thin film crystallized by a linearly polarized Nd:YAG pulse laser beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Horita, Susumu; Kaki, Hirokazu; Nishioka, Kensuke

2007-07-01

Amorphous Si films of 60 and 10 nm thick on glass substrates were irradiated by a linearly polarized Nd:YAG pulse laser with the wavelength {lambda}=532 nm at the incident angle {theta}{sub i}=0. The surface of the irradiated 60-nm-thick film had both periodic ridges perpendicular to the electric field vector E and aperiodic ridges roughly parallel to E, where the spatial period of the periodic ridges was almost {lambda}. From the continuous 10-nm-thick film, the separate rectangular Si islands were formed with a periodic distance of {lambda}, with the edges parallel or perpendicular to E. When {theta}{sub i} was increased frommore » normal incidence of the s-polarized beam for a 60-nm-thick film, the aperiodic ridges were reduced while the periodic ridges were still formed. For a 10-nm-thick film, the Si stripes were formed perpendicular to E, using the s-polarized beam at {theta}{sub i}=12 deg. In order to investigate the mechanisms of the surface modifications of, in particular, aperiodic ridges, islands, and stripes, we improved the previous theoretical model of the periodic distribution of the beam energy density (periodic E-D) generated by irradiation of the linearly polarized laser beam, taking account of the multireflection effect in the Si film which is semitransparent for {lambda}. Further, the calculated E-D was corrected with respect to the thermal diffusion in the irradiated Si film. The calculation results show that the two-dimensional E-D consists of a constant or a dc term and a sinusoidal or an ac term which contains various spatial periods. The multireflection effect strongly influences the amplitude and phase of every ac term, which means that the amplitude and phase depend on the film thickness. The thermal diffusion during the heating of the irradiated film greatly reduces the amplitudes of the ac terms with periods below the thermal diffusion length. The theoretical calculation showed that, by increasing {theta}{sub i}, the temperature distribution in the irradiated Si film was changed from two-dimensional toward one-dimensional, which can explain the above experimental results reasonably.« less
Single-grain growth in Si film by chevron-shaped cw laser beam scanning

NASA Astrophysics Data System (ADS)

Yeh, Wenchang; Yamazaki, Satoki; Ishimoto, Akihisa; Morito, Shigekazu

2016-02-01

A single grain with a length of 450 µm and a width of 5-6 µm was grown in a 60 nm Si film on SiO2 by scanning a chevron-shaped cw laser beam, which was formed by passing a linear laser beam through a novel one-sided Dove prism. The crystal did not have any dominant orientations in both the growth and normal directions. The orientation rotated about the transverse direction at a rate of 0.47-0.51°/µm in the forward direction, which suggests that the lattice constant at the film surface was 0.049-0.053% larger than that at the film bottom.
Development of Thomson scattering system on Shenguang-III prototype laser facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Tao; Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, Sichuan 621900; Li, Zhichao

2015-02-15

A Thomson scattering diagnostic system, using a 263 nm laser as the probe beam, is designed and implemented on Shenguang-III prototype laser facility. The probe beam is provided by an additional beam line completed recently. The diagnostic system allows simultaneous measurements of both ion feature and red-shifted electron feature from plasmas in a high-temperature (≥2 keV) and high-density (≥10{sup 21} cm{sup −3}) regime. Delicate design is made to satisfy the requirements for successful detection of the electron feature. High-quality ion feature spectra have already been diagnosed via this system in recent experiments with gas-filled hohlraums.
Extending solid state laser performance

NASA Astrophysics Data System (ADS)

Miesak, Ed

2017-02-01

Coherent Diode-Pumped Solid-State Orlando (CDO), formerly known as Lee Laser, headquartered in Orlando Florida produces CW and pulsed solid state lasers. Primary wavelengths include 1064 nm, 532 nm, and 355 nm. Other wavelengths produced include 1320 nm, 15xx nm, and 16xx nm. Pulse widths are in the range of singles to hundreds of nanoseconds. Average powers are in the range of a few watts to 1000 watts. Pulse repetition rates are typically in the range of 100 Hz to 100 KHz. Laser performance parameters are often modified according to customer requests. Laser parameters that can be adjusted include average power, pulse repetition rate, pulse length, beam quality, and wavelength. Laser parameters are typically cross-coupled such that adjusting one may change some or all of the others. Customers often request one or more parameters be changed without changing any of the remaining parameters. CDO has learned how to accomplish this successfully with rapid turn-around times and minimal cost impact. The experience gained by accommodating customer requests has produced a textbook of cause and effect combinations of laser components to accomplish almost any parameter change request. Understanding the relationships between component combinations provides valuable insight into lasing effects allowing designers to extend laser performance beyond what is currently available. This has led to several break through products, i.e. >150W average power 355 nm, >60W average power 6 ps 1064 nm, pulse lengths longer than 400 ns at 532 nm with average power >100W, >400W 532 nm with pulse lengths in the 100 ns range.
Fiber Raman laser and amplifier pumped by Nd3+:YVO4 solid state laser

NASA Astrophysics Data System (ADS)

Liu, Deming; Zhang, Minming; Liu, Shuang; Nie, Mingju; Wang, Ying

2005-04-01

Pumping source is the key technology of fiber Raman amplifiers (FRA) which are important for ultra long haul and high bit rate dense wavelength division multiplexing (DWDM) systems. In this paper the research work of the project, "Fiber Raman Laser and Amplifier pumped by Nd3+:YVO4 Solid State Laser", supported by the National High-tech Program (863-program) of China is introduced, in which a novel 14xx nm pump module with fine characteristics of high efficiency, simplicity, compactness and low cost is researched and developed. A compact 1342 nm Nd3+:YVO4 diode pumped solid state laser (DPSSL) module is developed with the total laser power of 655mW and the slope efficiency of 42.6% pumped by a 2W 808nm laser diode (LD). A special C-lens fiber collimator is designed to couple the 1342nm laser beam into a piece of single mode fiber (SMF) and the coupling efficiency of 80% is reached. The specific 14xx nm output laser is generated from a single stage Raman resonator which includes a pair of fiber Bragg gratings and a piece of Germanic-silicate or Phospho-silicate fiber pumped by such DPSSL module. The slope efficiency for conversion from 1342 to 14xx nm radiation is 75% and the laser power is more than 300mW each. Finally, Raman gain experiments are carried out with 100km SMF. 100 nm bandwidth with 10dB on-off Raman gain and 1.1dB gain flatness is achieved by pumped at 1425, 1438, 1455 and 1490nm.
A high-finesse Fabry-Perot cavity with a frequency-doubled green laser for precision Compton polarimetry at Jefferson Lab

DOE PAGES

Rakhman, A.; Hafez, Mohamed A.; Nanda, Sirish K.; ...

2016-03-31

Here, 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 enhancementmore » 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 1.0 GeV and 50 μA.« less
Formation of thermochemical laser-induced periodic surface structures on Ti films by a femtosecond IR Gaussian beam: regimes, limiting factors, and optical properties

NASA Astrophysics Data System (ADS)

Dostovalov, A. V.; Korolkov, V. P.; Babin, S. A.

2017-01-01

The formation of thermochemical laser-induced periodic surface structures (TLIPSS) on 400-nm Ti films deposited onto a glass substrate is investigated under irradiation by a femtosecond laser with a wavelength of 1026 nm, pulse duration of 232 fs, repetition rate of 200 kHz, and with different spot sizes of 4-21 μm. The optimal fluence for TLIPSS formation reduces monotonously with increasing the spot diameter in the range. It is found that the standard deviation of the TLIPSS period depends significantly on the beam size and reaches approximately 2% when the beam diameter is in the range of 10-21 μm. In addition to TLIPSS formation with the main period slightly smaller than the laser wavelength, an effect of TLIPSS spatial frequency doubling is detected. The optical properties of TLIPSS (reflection spectrum and diffraction efficiency at different incident angles and polarizations) are investigated and compared with theoretical ones to give a basis for the development of an optical inspecting method. The refractive index and absorption coefficient of oxidized ridges of the TLIPSS are theoretically estimated by simulation of the experimental reflection spectrum in the zeroth diffraction order.
Activating neurons by light in free-moving adult flies

NASA Astrophysics Data System (ADS)

Wu, Ming-Chin; Hsiao, Po-Yen; Chu, Li-An; Lin, Yen-Yin; Fu, Chien-Chung; Chiang, Ann-Shyn

2015-01-01

In this presentation, we show our preliminary results which is related to neurons activation in vivo by laser. A laser scanning system was adopted to guide laser beam to an assigned fly and an assigned position. A 473-nm laser can be a heat punishment source to restrain a wild-type fly's moving area. Furthermore, neurons in optogenetics transgene flies can be triggered by the blue laser in this system.
Formation of laser-induced periodic surface structures on niobium by femtosecond laser irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, A.; Dias, A.; Gomez-Aranzadi, M.

2014-05-07

The surface morphology of a Niobium sample, irradiated in air by a femtosecond laser with a wavelength of 800 nm and pulse duration of 100 fs, was examined. The period of the micro/nanostructures, parallel and perpendicularly oriented to the linearly polarized fs-laser beam, was studied by means of 2D Fast Fourier Transform analysis. The observed Laser-Induced Periodic Surface Structures (LIPSS) were classified as Low Spatial Frequency LIPSS (periods about 600 nm) and High Spatial Frequency LIPSS, showing a periodicity around 300 nm, both of them perpendicularly oriented to the polarization of the incident laser wave. Moreover, parallel high spatial frequency LIPSS were observedmore » with periods around 100 nm located at the peripheral areas of the laser fingerprint and overwritten on the perpendicular periodic gratings. The results indicate that this method of micro/nanostructuring allows controlling the Niobium grating period by the number of pulses applied, so the scan speed and not the fluence is the key parameter of control. A discussion on the mechanism of the surface topology evolution was also introduced.« less
Laser-induced breakdown spectroscopy for in-cylinder equivalence ratio measurements in laser-ignited natural gas engines.

PubMed

Joshi, Sachin; Olsen, Daniel B; Dumitrescu, Cosmin; Puzinauskas, Paulius V; Yalin, Azer P

2009-05-01

In this contribution we present the first demonstration of simultaneous use of laser sparks for engine ignition and laser-induced breakdown spectroscopy (LIBS) measurements of in-cylinder equivalence ratios. A 1064 nm neodynium yttrium aluminum garnet (Nd:YAG) laser beam is used with an optical spark plug to ignite a single cylinder natural gas engine. The optical emission from the combustion initiating laser spark is collected through the optical spark plug and cycle-by-cycle spectra are analyzed for H(alpha)(656 nm), O(777 nm), and N(742 nm, 744 nm, and 746 nm) neutral atomic lines. The line area ratios of H(alpha)/O(777), H(alpha)/N(746), and H(alpha)/N(tot) (where N(tot) is the sum of areas of the aforementioned N lines) are correlated with equivalence ratios measured by a wide band universal exhaust gas oxygen (UEGO) sensor. Experiments are performed for input laser energy levels of 21 mJ and 26 mJ, compression ratios of 9 and 11, and equivalence ratios between 0.6 and 0.95. The results show a linear correlation (R(2) > 0.99) of line intensity ratio with equivalence ratio, thereby suggesting an engine diagnostic method for cylinder resolved equivalence ratio measurements.
Laser-induced microjet injection into preablated skin for more effective transdermal drug delivery

NASA Astrophysics Data System (ADS)

Jang, Hun-jae; Hur, Eugene; Kim, Yoonkwan; Lee, Seol-Hoon; Kang, Nae G.; Yoh, Jack J.

2014-11-01

A breakthrough in the efficient transdermal delivery of drug via the laser-driven microjet is reported. A single source of laser beam is split into two: one beam ablates a targeted spot on a skin and another beam drives the injector for fast microjet ejection into a preablated spot. This combined ablation and microjet injection scheme using a beam splitter utilizes 1∶4 laser energy sharing between generation of the microhole via ablation and the microjet which is generated using the Er:YAG laser beam at a 2940-nm wavelength and 150-μs pulse duration. A careful analysis of the injection mechanism is carried out by studying the response of the elastic membrane that separates a driving water unit for bubble expansion from a drug unit for a microjet ejection. The efficiency of the present delivery scheme is evaluated by the abdominal porcine skin test using the fluorescein isothiocyanate staining and the confocal microscopy for quantitative delivery confirmation. The depth of penetration and the injected volume of the drug are also confirmed by polyacrylamide gel tests.
Laser-induced microjet injection into preablated skin for more effective transdermal drug delivery.

PubMed

Jang, Hun-Jae; Hur, Eugene; Kim, Yoonkwan; Lee, Seol-Hoon; Kang, Nae G; Yoh, Jack J

2014-11-01

A breakthrough in the efficient transdermal delivery of drug via the laser-driven microjet is reported. A single source of laser beam is split into two: one beam ablates a targeted spot on a skin and another beam drives the injector for fast microjet ejection into a preablated spot. This combined ablation and microjet injection scheme using a beam splitter utilizes laser energy sharing between generation of the microhole via ablation and the microjet which is generated using the Er:YAG laser beam at a 2940-nm wavelength and pulse duration. A careful analysis of the injection mechanism is carried out by studying the response of the elastic membrane that separates a driving water unit for bubble expansion from a drug unit for a microjet ejection. The efficiency of the present delivery scheme is evaluated by the abdominal porcine skin test using the fluorescein isothiocyanate staining and the confocal microscopy for quantitative delivery confirmation. The depth of penetration and the injected volume of the drug are also confirmed by polyacrylamide gel tests.
Injection locking of a low cost high power laser diode at 461 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pagett, C. J. H.; Moriya, P. H., E-mail: paulohisao@ifsc.usp.br; Celistrino Teixeira, R.

2016-05-15

Stable laser sources at 461 nm are important for optical cooling of strontium atoms. In most existing experiments, this wavelength is obtained by frequency doubling infrared lasers, since blue laser diodes either have low power or large emission bandwidths. Here, we show that injecting less than 10 mW of monomode laser radiation into a blue multimode 500 mW high power laser diode is capable of slaving at least 50% of the power to the desired frequency. We verify the emission bandwidth reduction by saturation spectroscopy on a strontium gas cell and by direct beating of the slave with the mastermore » laser. We also demonstrate that the laser can efficiently be used within the Zeeman slower for optical cooling of a strontium atomic beam.« less

Full path compensation laser feedback interferometry for remote sensing with recovered nanometer resolutions

NASA Astrophysics Data System (ADS)

Xu, Ling; Tan, Yidong; Zhang, Shulian

2018-03-01

The accuracy of the existing laser feedback interferometry for measuring the remote target is limited to several microns due to environmental disturbances. A novel approach is presented in this paper based on the double-beam frequency-shift feedback of the laser, which can completely eliminate the dead path errors and measure the displacement or vibration with accuracy at nanometer scale even at a far measurement distance. The two beams emitted from one Nd:YVO4 crystal are incident on the measurement target and its adjacent reference surface, respectively. The reference surface could be taken from the nearby stationary object, without the need to put a reference mirror. The feedback paths and shift frequencies of the two beams are the same, so the air disturbances and the thermal effects in the way could be fully compensated. Under common room conditions, the displacement of a steel block at a distance of 10 m is measured, which proved that the system's stability is ±12 nm in 100 s and ±50 nm in 1000 s, the short-term resolution is better than 3 nm, and the linearity within the 300 mm range is 5 × 10-6 and within the 100 μm range is 1 × 10-4.
Wavelength stabilized DBR high power diode laser using EBL optical confining grating technology

NASA Astrophysics Data System (ADS)

Paoletti, R.; Codato, S.; Coriasso, C.; Gotta, P.; Meneghini, G.; Morello, G.; De Melchiorre, P.; Riva, E.; Rosso, M.; Stano, A.; Gattiglio, M.

2018-02-01

This paper reports a DBR High Power Diode Laser (DBR-HPDL) realization, emitting up to 10W in the 920 nm range. High spectral purity (90% power in about 0.5 nm), and wavelength stability versus injected current (about 5 times more than standard FP laser) candidates DBR-HPDL as a suitable device for wavelength stabilized pump source, and high brightness applications exploiting Wavelength Division Multiplexing. Key design aspect is a multiple-orders Electron Beam Lithography (EBL) optical confining grating, stabilizing on same wafer multiple wavelengths by a manufacturable and reliable technology. Present paper shows preliminary demonstration of wafer with 3 pitches, generating DBRHPDLs 2.5 nm spaced.
High-energy high-efficiency Nd:YLF laser end-pump by 808 nm diode

NASA Astrophysics Data System (ADS)

Ma, Qinglei; Mo, Haiding; Zhao, Jay

2018-04-01

A model is developed to calculate the optimal pump position for end-pump configuration. The 808 nm wing pump is employed to spread the absorption inside the crystal. By the optimal laser cavity design, a high-energy high-efficiency Nd:YLF laser operating at 1053 nm is presented. In cw operation, a 13.6 W power is obtained with a slope efficiency of 51% with respect to 30 W incident pump power. The beam quality is near diffraction limited with M2 ∼ 1.02. In Q-switch operation, a pulse energy of 5 mJ is achieved with a peak power of 125 kW at 1 kHz repetition rate.
Progress in LPI Experiments at the NikeLaser

NASA Astrophysics Data System (ADS)

Weaver, J.; Kehne, D.; Obenschain, S.; Schmitt, A.; Serlin, V.; Oh, J.; Lehmberg, R.; Tsung, F.; McKenty, P.; Seely, J.

2014-10-01

The experimental program at the Nike laser facility at NRL is studying laser plasma instabilities (LPI) in the quarter critical region and cross-beam energy transport (CBET). The Nike krypton-fluorine (KrF) laser has unique characteristics that allow parametric studies of LPI. These features include short wavelength (248 nm), large bandwidth (~2-3 THz), beam smoothing by induced spatial incoherence (ISI), and full aperture focal spot zooming during the laser pulse. Nike also has a unique beam geometry that combines two widely separated beam arrays (145° in azimuth) with close beam-beam spacing (as low as 3.5°) within the main drive array. Particularly relevant for the CBET studies, recent campaigns have demonstrated the capability to alter the laser bandwidth by a factor of ~10 as well as shifts in the peak laser wavelength. An extensive LPI diagnostic suite is available for observation of stimulated Raman scattering, two-plasmon decay, stimulated Brillouin scattering, the parametric decay instability, and hard x-ray emission due to hot electrons. An overview of the observations of scattered laser light made during the previous studies of instabilities in the quarter critical region will be presented. Ongoing analysis of observed LPI emission from rotated targets will also be included. Plans for upcoming experiments related to quarter critical instabilities and CBET will be discussed. Work supported by DoE/NNSA.
Infrared laser ablation of polymeric nanocomposites: A study of surface structure and plume formation

NASA Astrophysics Data System (ADS)

Bartolucci, S. F.; Miller, M. J.; Warrender, J. M.

2016-12-01

The behavior of carbon nanotube composites subjected to laser pulse heating with a 1070 nm variable pulse duration laser has been studied. Previous work has shown that carbon nanotube composites form a protective network on the surface of a composite, which reduces heat input to the underlying polymer and slows mass loss. In this work, we have studied the interaction between the incident laser and the plume formed above the composite. We have correlated these interactions with features observed in the time-resolved mass loss data and confirmed them with observations using high-speed video of the laser irradiations. Beam interactions were studied as a function of laser irradiance and nanotube content. It is shown that beam-plume interactions occur for the carbon nanotube composites and that the interactions occur at shorter pulse durations for increased nanotube content and laser irradiance. When we eliminate beam-plume interaction through alteration of the sample orientation relative to the incident beam, we are able to elucidate the individual contributions of the carbon nanotube surface network and the plume to the observed decrease in mass loss after laser irradiation. We examine the plume content using microscopy and Raman spectroscopy and show that greater beam absorption occurs when there is a higher graphitic content in the plume.
Investigation of holmium-doped zirconium oxide ceramic phosphor as an ultraviolet wavelength-discriminating laser beam viewer

NASA Astrophysics Data System (ADS)

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.
Status of the laser ion source at IMP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sha, S.; Graduate University of Chinese Academy of Sciences, Beijing 100049; School of Nuclear science and technology, Lanzhou University, Lanzhou 73000

2012-02-15

A laser (Nd:YAG laser, 3 J, 1064 nm, 8-10 ns) ion source has been built and under development at IMP to provide pulsed high-charge-state heavy ion beams to a radio frequency quadrupole (RFQ) for upgrading the IMP accelerators with a new low-energy beam injector. The laser ion source currently operates in a direct plasma injection scheme to inject the high charge state ions produced from a solid target into the RFQ. The maximum power density on the target was about 8.4 x 10{sup 12} W/cm{sup 2}. The preliminary experimental results will be presented and discussed in this paper.
Note: A pulsed laser ion source for linear induction accelerators

NASA Astrophysics Data System (ADS)

Zhang, H.; Zhang, K.; Shen, Y.; Jiang, X.; Dong, P.; Liu, Y.; Wang, Y.; Chen, D.; Pan, H.; Wang, W.; Jiang, W.; Long, J.; Xia, L.; Shi, J.; Zhang, L.; Deng, J.

2015-01-01

We have developed a high-current laser ion source for induction accelerators. A copper target was irradiated by a frequency-quadrupled Nd:YAG laser (266 nm) with relatively low intensities of 108 W/cm2. The laser-produced plasma supplied a large number of Cu+ ions (˜1012 ions/pulse) during several microseconds. Emission spectra of the plasma were observed and the calculated electron temperature was about 1 eV. An induction voltage adder extracted high-current ion beams over 0.5 A/cm2 from a plasma-prefilled gap. The normalized beam emittance measured by a pepper-pot method was smaller than 1 π mm mrad.
Smooth e-beam-deposited tin-doped indium oxide for III-nitride vertical-cavity surface-emitting laser intracavity contacts

NASA Astrophysics Data System (ADS)

Leonard, J. T.; Cohen, D. A.; Yonkee, B. P.; Farrell, R. M.; DenBaars, S. P.; Speck, J. S.; Nakamura, S.

2015-10-01

We carried out a series of simulations analyzing the dependence of mirror reflectance, threshold current density, and differential efficiency on the scattering loss caused by the roughness of tin-doped indium oxide (ITO) intracavity contacts for 405 nm flip-chip III-nitride vertical-cavity surface-emitting lasers (VCSELs). From these results, we determined that the ITO root-mean-square (RMS) roughness should be <1 nm to minimize scattering losses in VCSELs. Motivated by this requirement, we investigated the surface morphology and optoelectronic properties of electron-beam (e-beam) evaporated ITO films, as a function of substrate temperature and oxygen flow and pressure. The transparency and conductivity were seen to increase with increasing temperature. Decreasing the oxygen flow and pressure resulted in an increase in the transparency and resistivity. Neither the temperature, nor oxygen flow and pressure series on single-layer ITO films resulted in highly transparent and conductive films with <1 nm RMS roughness. To achieve <1 nm RMS roughness with good optoelectronic properties, a multi-layer ITO film was developed, utilizing a two-step temperature scheme. The optimized multi-layer ITO films had an RMS roughness of <1 nm, along with a high transparency (˜90% at 405 nm) and low resistivity (˜2 × 10-4 Ω-cm). This multi-layer ITO e-beam deposition technique is expected to prevent p-GaN plasma damage, typically observed in sputtered ITO films on p-GaN, while simultaneously reducing the threshold current density and increasing the differential efficiency of III-nitride VCSELs.
Photofragmentation of colloidal solutions of gold nanoparticles under femtosecond laser pulses in IR and visible ranges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Danilov, P A; Zayarnyi, D A; Ionin, A A

The specific features of photofragmentation of sols of gold nanoparticles under focused femtosecond laser pulses in IR (1030 nm) and visible (515 nm) ranges is experimentally investigated. A high photofragmentation efficiency of nanoparticles in the waist of a pulsed laser beam in the visible range (at moderate radiation scattering) is demonstrated; this efficiency is related to the excitation of plasmon resonance in nanoparticles on the blue shoulder of its spectrum, in contrast to the regime of very weak photofragmentation in an IR-laser field of comparable intensity. Possible mechanisms of femtosecond laser photofragmentation of gold nanoparticles are discussed. (extreme light fieldsmore » and their applications)« less
Collimation testing using slit Fresnel diffraction

NASA Astrophysics Data System (ADS)

Luo, Xiaohe; Hui, Mei; Wang, Shanshan; Hou, Yinlong; Zhou, Siyu; Zhu, Qiudong

2018-03-01

A simple collimation testing method based on slit Fresnel diffraction is proposed. The method needs only a CMOS and a slit with no requirement in dimensional accuracy. The light beam to be tested diffracts across the slit and forms a Fresnel diffraction pattern received by CMOS. After analysis, the defocusing amount and the distance between the primary peak point and secondary peak point of diffraction pattern fulfill an expression relationship and then the defocusing amount can be deduced from the expression. The method is applied to both the coherent beam and partially coherent beam, and these two beams are emitted from a laser and light-emitting diode (LED) with a spectrum width of about 50 nm in this paper. Simulations show that the wide spectrum of LED has the effect of smooth filtering to provide higher accuracy. Experiments show that the LED with a spectrum width of about 50 nm has a lower limitation error than the laser and can achieve up to 58.1601 μm with focal length 200 mm and slit width 15 mm.
980 nm tapered lasers with photonic crystal structure for low vertical divergence

NASA Astrophysics Data System (ADS)

Ma, Xiaolong; Qu, Hongwei; Zhao, Pengchao; Liu, Yun; Zheng, Wanhua

2016-10-01

High power tapered lasers with nearly diffraction-limited beam quality have attracted much attention in numerous applications such as nonlinear frequency conversion, optical pumping of solid-state and fiber lasers, medical treatment and others. However, the large vertical divergence of conventional tapered lasers is a disadvantage, which makes beam shaping difficult and expensive in applications. Diode lasers with photonic crystal structure can achieve a large mode size and a narrow vertical divergence. In this paper, we present tapered lasers with photonic crystal structure emitting at 980 nm. The epitaxial layer is grown using metal organic chemical vapor deposition. The device has a total cavity length of 2 mm, which consists of a 400-um long ridge-waveguide section and a 1600-um long tapered section. The taper angle is 4°. An output power of 3.3 W is achieved with a peak conversion efficiency of 35% in pulsed mode. The threshold current is 240 mA and the slope efficiency is 0.78 W/A. In continuous wave mode, the output power is 2.87 W, which is limited by a suddenly failure resulting from catastrophic optical mirror damage. The far field divergences with full width at half maximum are 12.3° in the vertical direction and 2.9° in the lateral direction at 0.5 A. At high injection level the vertical divergence doesn't exceed 16°. Beam quality factor M2 is measured based on second moment definition in CW mode. High beam quality is demonstrated by M2 value of less than 2 in both vertical and lateral directions.
Single Frequency Monolithic Solid State Green Laser as a Potential Source for Vibrometry Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sotor, Jaroslaw Z.; Antonczak, Arkadiusz J.; Abramski, Krzysztof M.

2010-05-28

In this paper miniature, monolithic single frequency solid state laser operating at 532 nm is presented. Developed Nd:GdVO{sub 4}/YVO{sub 4}/KTP consist of three crystal bonded together with a UV adhesive. The single frequency operation was obtained in wide temperature range from 17 deg. C to 27 deg. C. The laser operated with output power up to 90 mW at 532 nm. The total optical efficiency (808 nm to 532 nm) was 9.5%. Power stability was at the level of +-0.8% and the long term frequency stability was approximately 3centre dot10{sup -8}. The beam has a Gaussian profile and the M2more » parameter was below 1.1.« less
High repetition rate, high energy, actively Q-switched all-in-fiber laser

NASA Astrophysics Data System (ADS)

Lecourt, J. B.; Bertrand, A.; Guillemet, S.; Hernandez, Y.; Giannone, D.

2010-05-01

We report an actively Q-switched Ytterbium-doped all-in-fibre laser delivering 10ns pulses with high repetition rate (from 100kHz to 1MHz). The laser operation has been validated at three different wavelengths (1040, 1050 and 1064nm). The laser can deliver up to 20Watts average power with an high beam quality (M2 = 1).
Evaluation of the performance of small diode pumped UV solid state (DPSS) Nd:YAG lasers as new radiation sources for atmospheric pressure laser ionization mass spectrometry (APLI-MS).

PubMed

Kersten, Hendrik; Lorenz, Matthias; Brockmann, Klaus J; Benter, Thorsten

2011-06-01

The performance of a KrF* bench top excimer laser and a compact diode pumped UV solid state (DPSS) Nd:YAG laser as photo-ionizing source in LC-APLI MS is compared. The commonly applied bench-top excimer laser, operating at 248 nm, provides power densities of the order of low MW/cm(2) on an illuminated area of 0.5 cm(2) (8 mJ/pulse, 5 ns pulse duration, beam waist area 0.5 cm(2), 3 MW/cm(2)). The DPSS laser, operating at 266 nm, provides higher power densities, however, on a two orders of magnitude smaller illuminated area (60 μJ/pulse, 1 ns pulse duration, beam waist area 2 × 10(-3) cm(2), 30 MW/cm(2)). In a common LC-APLI MS setup with direct infusion of a 10 nM pyrene solution, the DPSS laser yields a significantly smaller ion signal (0.9%) and signal to noise ratio (1.4%) compared with the excimer laser. With respect to the determined low detection limits (LODs) for PAHs of 0.1 fmol using an excimer laser, LODs in DPSS laser LC-APLI MS in the low pmol regime are expected. The advantages of the DPSS laser with respect to applicability (size, cost, simplicity) may render this light source the preferred one for APLI applications not focusing on ultimately high sensitivities. Furthermore, the impact of adjustable ion source parameters on the performance of both laser systems is discussed in terms of the spatial sensitivity distribution described by the distribution of ion acceptance (DIA) measurements. Perspectives concerning the impact on future APLI-MS applications are given.
In vivo monitoring laser tissue interaction using high resolution Fourier-domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Jo, Hang Chan; Shin, Dong Jun; Ahn, Jin-Chul; Chung, Phil-Sang; Kim, DaeYu

2017-02-01

Laser-induced therapies include laser ablation to remove or cut target tissue by irradiating high-power focused laser beam. These laser treatments are widely used tools for minimally invasive surgery and retinal surgical procedures in clinical settings. In this study, we demonstrate laser tissue interaction images of various sample tissues using high resolution Fourier-domain optical coherence tomography (Fd-OCT). We use a Q-switch diode-pumped Nd:YVO4 nanosecond laser (532nm central wavelength) with a 4W maximum output power at a 20 kHz repetition rate to ablate in vitro and in vivo samples including chicken breast and mouse ear tissues. The Fd-OCT system acquires time-series Bscan images at the same location during the tissue ablation experiments with 532nm laser irradiation. The real-time series of OCT cross-sectional (B-scan) images compare structural changes of 532nm laser ablation using same and different laser output powers. Laser tissue ablation is demonstrated by the width and the depth of the tissue ablation from the B-scan images.
Laser ablation of dental calculus at 400 nm using a Ti:sapphire laser

NASA Astrophysics Data System (ADS)

Schoenly, Joshua E.; Seka, Wolf; Rechmann, Peter

2009-02-01

A Nd:YAG laser-pumped, frequency-doubled Ti:sapphire laser is used for selective ablation of calculus. The laser provides <=25 mJ at 400 nm (60-ns pulse width, 10-Hz repetition rate). The laser is coupled into an optical multimode fiber coiled around a 4-in.-diam drum to generate a top-hat output intensity profile. With coaxial water cooling, this is ideal for efficient, selective calculus removal. This is in stark contrast with tightly focused Gaussian beams that are energetically inefficient and lead to irreproducible results. Calculus is well ablated at high fluences >=2J/cm2 stalling occurs below this fluence because of photobleaching. Healthy hard tissue is not removed at fluences <=3 J/cm2.
Calcium and lithium ion production for laser ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okamura, M.; Palm, K.; Stifler, C.

2015-08-23

Calcium and lithium ion beams are required by NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL) to simulate the effects of cosmic radiation. To find out difficulties to provide such high reactive material as laser targets, the both species were experimentally tested. Plate-shaped lithium and calcium targets were fabricated to create ablation plasmas with a 6ns, 1064nm Nd:YAG laser. We found significant oxygen contamination in both the Ca and Li high-charge-state beams due to the rapid oxidation of the surfaces. A large-spot-size, low-power-density laser was then used to analyze the low-charge-state beams without scanning the targets. The low-charge-statemore » Ca beam did not have any apparent oxygen contamination, showing the potential to clean the target entirely with a low-power beam once in the chamber. The Li target was clearly still oxidizing in the chamber after each low-power shot. To measure the rate of oxidation, we shot the low-power laser at the target repeatedly at 10sec, 30sec, 60sec, and 120sec interval lengths, showing a linear relation between the interval time and the amount of oxygen in the beam.« less
FALCON nuclear-reactor-pumped laser program and wireless power transmission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lipinski, R.J.; Pickard, P.S.

1992-12-31

FALCON is a high-power, reactor-pumped laser concept. The major strengths of a reactor-pumped laser are (1) simple, modular construction, (2) long-duration, closed-cycle capability, (3) self-contained power, (4) compact size, and (5) a variety of wavelengths (from visible to infrared). Reactor-pumped lasing has been demonstrated experimentally in various mixtures of xenon, argon, neon, and helium at wavelengths of 585, 703, 725, 1271, 1733, 1792, 2032, 2630, 2650, and 3370 nm with intrinsic efficiency as high as 2.5%. Powers up to 300 W for 2 ms have been demonstrated. Projected beam quality for FALCON is good enough that frequency doubling at reasonablemore » efficiencies could be expected to yield wavelengths at 353, 363, 636, 867, 896, 1016, 1315, 1325, and 1685 nm. Appropriate missions for FALCON are described and include power beaming to satellites, the moon, and unmanned surveillance planes; lunar mapping; space debris removal; and laser propulsion.« less
FALCON nuclear-reactor-pumped laser program and wireless power transmission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lipinski, R.J.; Pickard, P.S.

1992-01-01

FALCON is a high-power, reactor-pumped laser concept. The major strengths of a reactor-pumped laser are (1) simple, modular construction, (2) long-duration, closed-cycle capability, (3) self-contained power, (4) compact size, and (5) a variety of wavelengths (from visible to infrared). Reactor-pumped lasing has been demonstrated experimentally in various mixtures of xenon, argon, neon, and helium at wavelengths of 585, 703, 725, 1271, 1733, 1792, 2032, 2630, 2650, and 3370 nm with intrinsic efficiency as high as 2.5%. Powers up to 300 W for 2 ms have been demonstrated. Projected beam quality for FALCON is good enough that frequency doubling at reasonablemore » efficiencies could be expected to yield wavelengths at 353, 363, 636, 867, 896, 1016, 1315, 1325, and 1685 nm. Appropriate missions for FALCON are described and include power beaming to satellites, the moon, and unmanned surveillance planes; lunar mapping; space debris removal; and laser propulsion.« less

Ultraviolet optical and microstructural properties of MgF2 and LaF3 coatings deposited by ion-beam sputtering and boat and electron-beam evaporation.

PubMed

Ristau, Detlev; Günster, Stefan; Bosch, Salvador; Duparré, Angela; Masetti, Enrico; Ferré-Borrull, Josep; Kiriakidis, George; Peiró, Francesca; Quesnel, Etienne; Tikhonravov, Alexander

2002-06-01

Single layers of MgF2 and LaF3 were deposited upon superpolished fused-silica and CaF2 substrates by ion-beam sputtering (IBS) as well as by boat and electron beam (e-beam) evaporation and were characterized by a variety of complementary analytical techniques. Besides undergoing photometric and ellipsometric inspection, the samples were investigated at 193 and 633 nm by an optical scatter measurement facility. The structural properties were assessed with atomic-force microscopy, x-ray diffraction, TEM techniques that involved conventional thinning methods for the layers. For measurement of mechanical stress in the coatings, special silicon substrates were coated and analyzed. The dispersion behavior of both deposition materials, which was determined on the basis of various independent photometric measurements and data reduction techniques, is in good agreement with that published in the literature and with the bulk properties of the materials. The refractive indices of the MgF2 coatings ranged from 1.415 to 1.440 for the wavelength of the ArF excimer laser (193 nm) and from 1.435 to 1.465 for the wavelength of the F2 excimer laser (157 nm). For single layers of LaF3 the refractive indices extended from 1.67 to 1.70 at 193 nm to approximately 1.80 at 157 nm. The IBS process achieves the best homogeneity and the lowest surface roughness values (close to 1 nm(rms)) of the processes compared in the joint experiment. In contrast to MgF2 boat and e-beam evaporated coatings, which exhibit tensile mechanical stress ranging from 300 to 400 MPa, IBS coatings exhibit high compressive stress of as much as 910 MPa. A similar tendency was found for coating stress in LaF3 single layers. Experimental results are discussed with respect to the microstructural and compositional properties as well as to the surface topography of the coatings.
Stable TEM00-mode Nd:YAG solar laser operation by a twisted fused silica light-guide

NASA Astrophysics Data System (ADS)

Bouadjemine, R.; Liang, D.; Almeida, J.; Mehellou, S.; Vistas, C. R.; Kellou, A.; Guillot, E.

2017-12-01

To improve the output beam stability of a TEM00-mode solar-pumped laser, a twisted fused silica light-guide was used to achieve uniform pumping along a 3 mm diameter and 50 mm length Nd:YAG rod. The concentrated solar power at the focal spot of a primary parabolic mirror with 1.18 m2 effective collection area was efficiently coupled to the entrance aperture of a 2D-CPC/2V-shaped pump cavity, within which the thin laser rod was pumped. Optimum solar laser design parameters were found through ZEMAX© non-sequential ray-tracing and LASCAD© laser cavity analysis codes. 2.3 W continuous-wave TEM00-mode 1064 nm laser power was measured, corresponding to 1.96 W/m2 collection efficiency and 2.2 W laser beam brightness figure of merit. Excellent TEM00-mode laser beam profile at M2 ≤ 1.05 and very good output power stability of less than 1.6% were achieved. Heliostat orientation error dependent laser power variation was considerably less than previous solar laser pumping schemes.
Electron-Beam Recombination Lasers

NASA Astrophysics Data System (ADS)

Rhoades, Robert Lewis

1992-01-01

The first known instance of electron-beam pumping of the 546.1 nm mercury laser is reported. This has been achieved using high-energy electrons to create intense ionization in a coaxial diode chamber containing a mixture of noble gases with a small amount of mercury vapor. Also reported are the results of a study of the 585.3 nm neon laser in He:Ne:Ar mixtures under similar experimental conditions. Both of these lasers are believed to be predominantly pumped by recombination. For the mercury laser, kinetic processes in the partially ionized plasma following the excitation pulse of high-energy electrons should favor the production of atomic mercury ions and molecular ions containing mercury. Subsequent recombination with electrons heavily favors the production of the 7^3S and 6^3 D states of Hg, of which 7^3S is the upper level of the reported laser. For the neon laser, the dominant recombining ion has been previously shown to be Ne_2^{+}. One of the dominant roles of helium in recombination lasers is inferred from the data for the neon laser at low helium concentrations. Helium appears to be necessary for the rapid relaxation of the electron energy which then increases the reaction rates for all known recombination processes thus increasing the pump rate into the upper state.
AlGaAs growth by OMCVD using an excimer laser

NASA Technical Reports Server (NTRS)

Warner, Joseph D.; Wilt, David M.; Pouch, John J.; Aron, Paul R.

1986-01-01

AlGaAs has been grown on GaAs by laser assisted OMCVD using an excimer laser, wavelength 193 nm, and a Cambridge OMCVD reactor. Films were grown at temperatures of 450 and 500 C with the laser beam parallel to the surface and impinging onto the surface at 15 deg from parallel. The samples were heated by RF coils while the laser beam was perpendicular to the gas flow. Typical gas flow parameters are 12 slm of H2, 15 sccm of Ga(CH3)3, 13 sccm of Al(CH3)3, and a pressure of 250 mbar. The initial energy density of the beam at the surface was 40 mJ/sq cm, the pulse rate was 20 pps, and the growth time was 7 min. The films were analyzed by Auger electron spectroscopy for the aluminum concentration and by TEM for the surface morphology.
Average power scaling of UV excimer lasers drives flat panel display and lidar applications

NASA Astrophysics Data System (ADS)

Herbst, Ludolf; Delmdahl, Ralph F.; Paetzel, Rainer

2012-03-01

Average power scaling of 308nm excimer lasers has followed an evolutionary path over the last two decades driven by diverse industrial UV laser microprocessing markets. Recently, a new dual-oscillator and beam management concept for high-average power upscaling of excimer lasers has been realized, for the first time enabling as much as 1.2kW of stabilized UV-laser average output power at a UV wavelength of 308nm. The new dual-oscillator concept enables low temperature polysilicon (LTPS) fabrication to be extended to generation six glass substrates. This is essential in terms of a more economic high-volume manufacturing of flat panel displays for the soaring smartphone and tablet PC markets. Similarly, the cost-effective production of flexible displays is driven by 308nm excimer laser power scaling. Flexible displays have enormous commercial potential and can largely use the same production equipment as is used for rigid display manufacturing. Moreover, higher average output power of 308nm excimer lasers aids reducing measurement time and improving the signal-to-noise ratio in the worldwide network of high altitude Raman lidar stations. The availability of kW-class 308nm excimer lasers has the potential to take LIDAR backscattering signal strength and achievable altitude to new levels.
Electra: Repetitively Pulsed Angularly Multiplexed KrF Laser System Performance

NASA Astrophysics Data System (ADS)

Wolford, Matthew; Myers, Matthew; Giuliani, John; Sethian, John; Burns, Patrick; Hegeler, Frank; Jaynes, Reginald

2008-11-01

As in a full size fusion power plant beam line, Electra is a multistage laser amplifier system. The multistage amplifier system consists of a commercial discharge laser and two doubled sided electron beam pumped amplifiers. Angular multiplexing is used in the optical layout to provide pulse length control and to maximize laser extraction from the amplifiers. Two angularly multiplexed beams have extracted 30 J of KrF laser light with an aperture 8 x 10 cm^2, which is sufficient to extract over 500 J from the main amplifier and models agree. The main amplifier of Electra in oscillator mode has demonstrated single shot and rep-rate laser energies exceeding 700 J with 100 ns pulsewidth at 248 nm with an aperture 29 x 29 cm^2. Continuous operation of the KrF electron beam pumped oscillator has lasted for more than 2.5 hours without failure at 1 Hz and 2.5 Hz. The measured intensity and pulse energy for durations greater than thousand shots are consistent at measurable rep-rates of 1 Hz, 2.5 Hz and 5 Hz.
Effect of laser beam on temperature distribution on artificial cylindrical shaped hard tissue bones

NASA Astrophysics Data System (ADS)

Al-Akhras, M.-Ali H.; Qaseer, Mohammad-Khair; Albiss, B. A.; Gezawa, Umar S.

2018-02-01

Samples from fresh lamb chest bones were made in cylindrical shapes to study the time variation of temperature T as functions of the cylindrical radius and depth when its front surface exposed to a laser beam of 110Mw power and 642nm wavelength. The laser beam was directed at the center of the front surface of the horizontal cylinder. The measurements were done in vacuum and at atmospheric pressure. Our data reveal the linear variation of T with time, followed by a gradual increase before it reaches a plateau value at higher time. This sort of behavior independent of the radius or the depth where the temperature was measured. Moreover, the maximum variation occurs on the front surface where the laser beam was hitting and diminishes gradually with depth deep inside the cylinder. Data at atmospheric pressure showed less changes in temperature. The temperature distribution in bone due to laser irradiation is very important for a rational use of laser therapy as well as in the surgery to minimizes the thermal tissue damage.
A simplified method for generating periodic nanostructures by interference lithography without the use of an anti-reflection coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kapon, Omree; Muallem, Merav; Palatnik, Alex

Interference lithography has proven to be a useful technique for generating periodic sub-diffraction limited nanostructures. Interference lithography can be implemented by exposing a photoresist polymer to laser light using a two-beam arrangement or more simply a one beam configuration based on a Lloyd's Mirror Interferometer. For typical photoresist layers, an anti-reflection coating must be deposited on the substrate to prevent adverse reflections from cancelling the holographic pattern of the interfering beams. For silicon substrates, such coatings are typically multilayered and complex in composition. By thinning the photoresist layer to a thickness well below the quarter wavelength of the exposing beam,more » we demonstrate that interference gratings can be generated without an anti-reflection coating on the substrate. We used ammonium dichromate doped polyvinyl alcohol as the positive photoresist because it provides excellent pinhole free layers down to thicknesses of 40 nm, and can be cross-linked by a low-cost single mode 457 nm laser, and can be etched in water. Gratings with a period of 320 nm and depth of 4 nm were realized, as well as a variety of morphologies depending on the photoresist thickness. This simplified interference lithography technique promises to be useful for generating periodic nanostructures with high fidelity and minimal substrate treatments.« less
Squeezing of Light via Reflection from a Silicon Micromechanical Resonator

DTIC Science & Technology

2013-03-14

Hz. Laser phase noise on the signal beam can be converted to intensity noise by reflection from the dispersive cavity or due to frequency dependent...Figure A6: Experimental setup for characterization of intensity and phase noise. The laser is amplitude stabilized and an attenuator is used to select...nm thick silicon de- vice layer of a silicon-on-insulator microchip (see Fig. 1a). The in-plane differential motion of the two beams at a fundamental
Development of an extended straightness measurement reference

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schenz, R.F.; Griffith, L.V.; Sommargren, G.E.

1988-09-06

The most accurate diamond turning machines have used physical straightness references. These references commonly are made of optical materials, such as Zerodur, and are flat enough to permit straightness measurements with an accuracy of 100--150 nm (4--6 microinches) p-v. In most cases, the flatness error is stable and can be accommodated by using a calibration table. The straightedges for the Large Optics Diamond Turning Machine (LODTM) at Lawrence Livermore National Laboratory (LLNL) are 1.1 meters in length and allow a straightness reference accuracy of 25--50 nm (1--2 microinches) p-v after calibration. Fabrication problems become insurmountable when a straightness reference formore » a length of up to 4 meters is desired. Moreover, the method of calibration by straightedge reversal does not account for gravitational sag when the sensing direction is vertical. Vertical sensing would be required in a four meter system and sag would become unacceptably large. Recent developments published in the literature suggest that the use of a laser beam for a reference may be feasible. Workers at Osaka University have reported a laser beam straightness reference that has a resolution of 3.5 nm, although tests were done only over a 200 mm length. LLNL has begun an investigation on the use of a directionally stabilized laser beam as a straightness measurement reference. The goal of the investigation is to provide a reference that is accurate to 25 nm (1 microinch) over a four meter distance. 3 refs., 2 figs.« less
DNA Damage in Bone Marrow Cells Induced by Femtosecond and Nanosecond Ultraviolet Laser Pulses.

PubMed

Morkunas, Vaidotas; Gabryte, Egle; Vengris, Mikas; Danielius, Romualdas; Danieliene, Egle; Ruksenas, Osvaldas

2015-12-01

The purpose of this study was to investigate the possible genotoxic impact of new generation 205 nm femtosecond solid-state laser irradiation on the DNA of murine bone marrow cells in vitro, and to compare the DNA damage caused by both femtosecond and nanosecond UV laser pulses. Recent experiments of corneal stromal ablation in vitro and in vivo applying femtosecond UV pulses showed results comparable with or superior to those obtained using nanosecond UV lasers. However, the possible genotoxic effect of ultrashort laser pulses was not investigated. Mouse bone marrow cells were exposed to different doses of 205 nm femtosecond, 213 and 266 nm nanosecond lasers, and 254 nm UV lamp irradiation. The comet assay was used for the evaluation of DNA damage. All types of irradiation demonstrated intensity-dependent genotoxic impact. The DNA damage induced depended mainly upon wavelength rather than on other parameters such as pulse duration, repetition rate, or beam delivery to a target. Both 205 nm femtosecond and clinically applied 213 nm nanosecond lasers' pulses induced a comparable amount of DNA breakage in cells exposed to the same irradiation dose. To further evaluate the suitability of femtosecond UV laser sources for microsurgery, a separate investigation of the genotoxic and mutagenic effects on corneal cells in vitro and, particularly, in vivo is needed.
Optical stimulation of the prostate nerves: A potential diagnostic technique

NASA Astrophysics Data System (ADS)

Tozburun, Serhat

There is wide variability in sexual potency rates (9--86%) after nerve-sparing prostate cancer surgery due to limited knowledge of the location of the cavernous nerves (CN's) on the prostate surface, which are responsible for erectile function. Thus, preservation of the CN's is critical in preserving a man's ability to have spontaneous erections following surgery. Nerve-mapping devices, utilizing conventional Electrical Nerve Stimulation (ENS) techniques, have been used as intra-operative diagnostic tools to assist in preservation of the CN. However, these technologies have proven inconsistent and unreliable in identifying the CN's due to the need for physical contact, the lack of spatial selectivity, and the presence of electrical artifacts in measurements. Optical Nerve Stimulation (ONS), using pulsed infrared laser radiation, is studied as an alternative to ENS. The objective of this study is sevenfold: (1) to develop a laparoscopic laser probe for ONS of the CN's in a rat model, in vivo; (2) to demonstrate faster ONS using continuous-wave infrared laser radiation; (3) to describe and characterize the mechanism of successful ONS using alternative laser wavelengths; (4) to test a compact, inexpensive all-single-mode fiber configuration for optical stimulation of the rat CN studies; (5) to implement fiber optic beam shaping methods for comparison of Gaussian and flat-top spatial beam profiles during ONS; (6) to demonstrate successful ONS of CN's through a thin layer of fascia placed over the nerve and prostate gland; and (7) to verify the experimentally determined therapeutic window for safe and reliable ONS without thermal damage to the CN's by comparison with a computational model for thermal damage. A 5.5-Watt Thulium fiber laser operated at 1870 nm and two pigtailed, single mode, near-IR diode lasers (150-mW, 1455-nm laser and 500-mW, 1550-nm laser) were used for non-contact stimulation of the rat CN's. Successful laser stimulation, as measured by an intracavernous pressure (ICP) response in the penis, was achieved with the laser operating in CW mode. CW optical nerve stimulation provides a significantly faster ICP response time using a lower laser power laser than conventional pulsed stimulation. An all-single-mode fiber design was successfully tested in a rat model. The CN reached a threshold temperature of ˜ 42 °C, with response times as short as 3 s, and ICP responses in the rat penis of up to 50 mmHg compared to a baseline of 5--10 mmHg. Chemical etching of the distal single-mode-fiber tip produced a concave shape and transformed the Gaussian to a flat-top spatial beam profile, resulting in simplified alignment of the laser beam with the nerve. This novel, all-single-mode-fiber laser nerve stimulation system introduces several advantages including: (1) a less expensive and more compact ONS configuration; (2) elimination of alignment and cleaning bulk optical components; and (3) improved spatial beam profile for simplified alignment. For the fascia layers over the CN's (240--600 microm), the 1550 nm laser with an optical penetration depth of ˜ 930 microm in water was substituted for the 1455 nm laser. Successful ONS was achieved, for the first time, in fascia layers up to 450 microm thick which is critical for future clinical translation of this method for intra-operative identification and preservation of CN's during prostate cancer surgery. In order to define the upper limit of the therapeutic window for ONS of CN in a rat model, in vivo, identification of the thermal damage threshold for the CN after laser irradiation was investigated by direct comparison of the visible thermal damage data with a theoretical thermal damage calculation utilizing a standard Arrhenius integral model.
Developing magnetorheological finishing (MRF) technology for the manufacture of large-aperture optics in megajoule class laser systems

NASA Astrophysics Data System (ADS)

Menapace, Joseph A.

2010-11-01

Over the last eight years we have been developing advanced MRF tools and techniques to manufacture meter-scale optics for use in Megajoule class laser systems. These systems call for optics having unique characteristics that can complicate their fabrication using conventional polishing methods. First, exposure to the high-power nanosecond and sub-nanosecond pulsed laser environment in the infrared (>27 J/cm2 at 1053 nm), visible (>18 J/cm2 at 527 nm), and ultraviolet (>10 J/cm2 at 351 nm) demands ultra-precise control of optical figure and finish to avoid intensity modulation and scatter that can result in damage to the optics chain or system hardware. Second, the optics must be super-polished and virtually free of surface and subsurface flaws that can limit optic lifetime through laser-induced damage initiation and growth at the flaw sites, particularly at 351 nm. Lastly, ultra-precise optics for beam conditioning are required to control laser beam quality. These optics contain customized surface topographical structures that cannot be made using traditional fabrication processes. In this review, we will present the development and implementation of large-aperture MRF tools and techniques specifically designed to meet the demanding optical performance challenges required in large aperture high-power laser systems. In particular, we will discuss the advances made by using MRF technology to expose and remove surface and subsurface flaws in optics during final polishing to yield optics with improve laser damage resistance, the novel application of MRF deterministic polishing to imprint complex topographical information and wavefront correction patterns onto optical surfaces, and our efforts to advance the technology to manufacture largeaperture damage resistant optics.
Developing Magnetorheological Finishing (MRF) Technology for the Manufacture of Large-Aperture Optics in Megajoule Class Laser Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menapace, J A

2010-10-27

Over the last eight years we have been developing advanced MRF tools and techniques to manufacture meter-scale optics for use in Megajoule class laser systems. These systems call for optics having unique characteristics that can complicate their fabrication using conventional polishing methods. First, exposure to the high-power nanosecond and sub-nanosecond pulsed laser environment in the infrared (>27 J/cm{sup 2} at 1053 nm), visible (>18 J/cm{sup 2} at 527 nm), and ultraviolet (>10 J/cm{sup 2} at 351 nm) demands ultra-precise control of optical figure and finish to avoid intensity modulation and scatter that can result in damage to the optics chainmore » or system hardware. Second, the optics must be super-polished and virtually free of surface and subsurface flaws that can limit optic lifetime through laser-induced damage initiation and growth at the flaw sites, particularly at 351 nm. Lastly, ultra-precise optics for beam conditioning are required to control laser beam quality. These optics contain customized surface topographical structures that cannot be made using traditional fabrication processes. In this review, we will present the development and implementation of large-aperture MRF tools and techniques specifically designed to meet the demanding optical performance challenges required in large-aperture high-power laser systems. In particular, we will discuss the advances made by using MRF technology to expose and remove surface and subsurface flaws in optics during final polishing to yield optics with improve laser damage resistance, the novel application of MRF deterministic polishing to imprint complex topographical information and wavefront correction patterns onto optical surfaces, and our efforts to advance the technology to manufacture large-aperture damage resistant optics.« less
Narrow-stripe broad-area lasers with distributed-feedback surface gratings as brilliant sources for high power spectral beam combining systems

NASA Astrophysics Data System (ADS)

Decker, J.; Crump, P.; Fricke, J.; Wenzel, H.; MaaÎ²dorf, A.; Erbert, G.; Tränkle, G.

2014-03-01

Laser systems based on spectral beam combining (SBC) of broad-area (BA) diode lasers are promising tools for material processing applications. However, the system brightness is limited by the in-plane beam param- eter product, BPP, of the BA lasers, which operate with a BPP of < 3mm-mrad. The EU project BRIDLE (www.bridle.eu) is developing novel diode laser sources for such systems, and several technological advances are sought. For increased system brightness and optimal ber-coupling the diode lasers should operate with reduced BPP and vertical far eld angle (95% power content), μV 95. The resulting diode lasers are fabricated as mini- bars for reduced assembly costs. Gratings are integrated into the mini-bar, with each laser stripe emitting at a different wavelength. In this way, each emitter can be directed into a single bre via low-cost dielectric filters. Distributed-feedback narrow-stripe broad-area (DFB-NBA) lasers are promising candidates for these SBC sys- tems. We review here the design process and performance achieved, showing that DFB-NBA lasers with stripe width, W = 30 μm, successfully cut of higher-order lateral modes, improving BPP. Uniform, surface-etched, 80th-order Bragg gratings are used, with weak gratings essential for high e ciency. To date, such DFB-NBA sources operate with < 50% effciency at output power, Pout < 6 W, with BPP < 1.8 mm-mrad and offV 95 36 . The emission wavelength is about 970 nm and the spectral width is < 0.7 nm (95% power). The BPP is half that of a DFB-BA lasers with W = 90 um. We conclude with a review of options for further performance improvements.
Two-Photon-Absorption Scheme for Optical Beam Tracking

NASA Technical Reports Server (NTRS)

Ortiz, Gerardo G.; Farr, William H.

2011-01-01

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

NASA Astrophysics Data System (ADS)

Choi, Tae Y.; Denton, Michael L.; Noojin, Gary D.; Estlack, Larry E.; Shrestha, Ramesh; Rockwell, Benjamin A.; Thomas, Robert; Kim, Dongsik

2014-09-01

A temperature detection system using a micropipette thermocouple sensor was developed for use within mammalian cells during laser exposure with an 8.6-μm beam at 532 nm. We have demonstrated the capability of measuring temperatures at a single-cell level in the microscale range by inserting micropipette-based thermal sensors of size ranging from 2 to 4 μm into the membrane of a live retinal pigment epithelium (RPE) cell subjected to a laser beam. We setup the treatment groups of 532-nm laser-irradiated single RPE cell and in situ temperature recordings were made over time. Thermal profiles are given for representative cells experiencing damage resulting from exposures of 0.2 to 2 s. The measured maximum temperature rise for each cell ranges from 39 to 73°C the RPE cells showed a signature of death for all the cases reported herein. In order to check the cell viability, real-time fluorescence microscopy was used to identify the transition of pigmented RPE cells between viable and damaged states due to laser exposure.
Laser microprocessing and nanoengineering of large-area functional micro/nanostructures

NASA Astrophysics Data System (ADS)

Tang, M.; Xie, X. Z.; Yang, J.; Chen, Z. C.; Xu, L.; Choo, Y. S.; Hong, M. H.

2011-12-01

Laser microprocessing and nanoengineering are of great interest to both scientists and engineers, since the inspired properties of functional micro/nanostructures over large areas can lead to numerous unique applications. Currently laser processing systems combined with high speed automation ensure the focused laser beam to process various materials at a high throughput and a high accuracy over large working areas. UV lasers are widely used in both laser microprocessing and nanoengineering. However by improving the processing methods, green pulsed laser is capable of replacing UV lasers to make high aspect ratio micro-grooves on fragile and transparent sapphire substrates. Laser micro-texturing can also tune the wetting property of metal surfaces from hydrophilic to super-hydrophobic at a contact angle of 161° without chemical coating. Laser microlens array (MLA) can split a laser beam into multiple laser beams and reduce the laser spot size down to sub-microns. It can be applied to fabricate split ring resonator (SRR) meta-materials for THz sensing, surface plasmonic resonance (SPR) structures for NIR and molding tools for soft lithography. Furthermore, laser interference lithography combined with thermal annealing can obtain a large area of sub-50nm nano-dot clusters used for SPR applications.
A webcam in Bayer-mode as a light beam profiler for the near infra-red

PubMed Central

Langer, Gregor; Hochreiner, Armin; Burgholzer, Peter; Berer, Thomas

2013-01-01

Beam profiles are commonly measured with complementary metal oxide semiconductors (CMOS) or charge coupled devices (CCD). The devices are fast and reliable but expensive. By making use of the fact that the Bayer-filter in commercial webcams is transparent in the near infra-red (>800 nm) and their CCD chips are sensitive up to about 1100 nm, we demonstrate a cheap and simple way to measure laser beam profiles with a resolution down to around ±1 μm, which is close to the resolution of the knife-edge technique. PMID:23645943
A webcam in Bayer-mode as a light beam profiler for the near infra-red.

PubMed

Langer, Gregor; Hochreiner, Armin; Burgholzer, Peter; Berer, Thomas

2013-05-01

Beam profiles are commonly measured with complementary metal oxide semiconductors (CMOS) or charge coupled devices (CCD). The devices are fast and reliable but expensive. By making use of the fact that the Bayer-filter in commercial webcams is transparent in the near infra-red (>800 nm) and their CCD chips are sensitive up to about 1100 nm, we demonstrate a cheap and simple way to measure laser beam profiles with a resolution down to around ±1 μm, which is close to the resolution of the knife-edge technique.

Thermal lens and all optical switching of new organometallic compound doped polyacrylamide gel

NASA Astrophysics Data System (ADS)

Badran, Hussain Ali

In this work thermal lens spectrometry (TLS) is applied to investigate the thermo-optical properties of new organometallic compound containing azomethine group, Dichloro bis [2-(2-hydroxybenzylideneamino)-5-methylphenyl] telluride platinum(II), doped polyacrylamide gel using transistor-transistor logic (TTL) modulated cw 532 nm laser beam as an excitation beam modulated at 10 Hz frequency and probe beam wavelength 635 nm at 14 mW. The technique is applied to determine the thermal diffusivities, ds/dT and the linear thermal expansion coefficient of the sample. All-optical switching effects with low background and high stability are demonstrated.
Long-period fibre grating writing with a slit-apertured femtosecond laser beam (λ = 1026 nm)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dostovalov, A V; Wolf, A A; Babin, S A

We report on long-period grating (LPG) writing in a standard telecom fibre, SMF-28e+, via refractive index modification by femtosecond pulses. A method is proposed for grating writing with a slit-apertured beam, which enables one to produce LPGs with reduced background losses and a resonance peak markedly stronger than that in the case of grating writing with a Gaussian beam. The method can be used to fabricate LPGs for use as spectral filters of fibre lasers and sensing elements of sensor systems. (fibre and integrated-optical structures)
Q-switched all-solid-state lasers and application in processing of thin-film solar cell

NASA Astrophysics Data System (ADS)

Liu, Liangqing; Wang, Feng

2009-08-01

Societal pressure to renewable clean energy is increasing which is expected to be used as part of an overall strategy to address global warming and oil crisis. Photovoltaic energy conversion devices are on a rapidly accelerating growth path driven by government, of which the costs and prices lower continuously. The next generation thin-film devices are considered to be more efficiency and greatly reduced silicon consumption, resulting in dramatically lower per unit fabrication costs. A key aspect of these devices is patterning large panels to create a monolithic array of series-interconnected cells to form a low current, high voltage module. This patterning is accomplished in three critical scribing processes called P1, P2, and P3. All-solid-state Q-switched lasers are the technology of choice for these processes, due to their advantages of compact configuration, high peak-value power, high repeat rate, excellent beam quality and stability, delivering the desired combination of high throughput and narrow, clean scribes. The end pumped all-solid-state lasers could achieve 1064nm IR resources with pulse width of nanoseconds adopting acoustic-optics Q-switch, shorter than 20ns. The repeat rate is up to 100kHz and the beam quality is close to diffraction limit. Based on this, 532nm green lasers, 355nm UV lasers and 266nm DUV lasers could be carried out through nonlinear frequency conversion. Different wave length lasers are chose to process selective materials. For example, 8-15 W IR lasers are used to scribe the TCO film (P1); 1-5 W green lasers are suitable for scribing the active semiconductor layers (P2) and the back contact layers (P3). Our company, Wuhan Lingyun Photo-electronic System Co. Ltd, has developed 20W IR and 5W green end-pumped Q-switched all-solid-state lasers for thin-film solar industry. Operating in high repeat rates, the speed of processing is up to 2.0 m/s.
Realization of a mW-level 10.7-eV (λ = 115.6 nm) laser by cascaded third harmonic generation of a Yb:fiber CPA laser at 1-MHz.

PubMed

Zhao, Zhigang; Kobayashi, Yohei

2017-06-12

We demonstrate a 10.7-eV (λ = 115.6 nm) laser with mW levels of average power and a 1-MHz repetition rate, which was driven by the third harmonic radiation (THG), at 347 nm, of an Yb:fiber chirped pulse amplifier (CPA) laser. The 347 nm ultraviolet radiation was obtained by frequency conversion of the high power output of a 1-MHz Yb:fiber CPA, using beta barium borate (BBO) nonlinear crystals. The frequency converted output was focused down into a gas cell filled with a mixture of Ar and Xe, and was subjected to a second THG frequency conversion. The generated 10.7-eV laser was separated from the fundamental beam using a LiF prism and no further separation from other harmonic waves was required. The highest measured output power was ~80 μW, which corresponded to an average power of ~1.25 mW inside the gas cell when the transmission coefficients of the LiF optics were taken into account. The corresponding conversion efficiency from 347 nm down to 115.6 nm was ~2.5 × 10 -4 .
Optimizing laser produced plasmas for efficient extreme ultraviolet and soft X-ray light sources

NASA Astrophysics Data System (ADS)

Sizyuk, Tatyana; Hassanein, Ahmed

2014-08-01

Photon sources produced by laser beams with moderate laser intensities, up to 1014 W/cm2, are being developed for many industrial applications. The performance requirements for high volume manufacture devices necessitate extensive experimental research supported by theoretical plasma analysis and modeling predictions. We simulated laser produced plasma sources currently being developed for several applications such as extreme ultraviolet lithography using 13.5% ± 1% nm bandwidth, possibly beyond extreme ultraviolet lithography using 6.× nm wavelengths, and water-window microscopy utilizing 2.48 nm (La-α) and 2.88 nm (He-α) emission. We comprehensively modeled plasma evolution from solid/liquid tin, gadolinium, and nitrogen targets as three promising materials for the above described sources, respectively. Results of our analysis for plasma characteristics during the entire course of plasma evolution showed the dependence of source conversion efficiency (CE), i.e., laser energy to photons at the desired wavelength, on plasma electron density gradient. Our results showed that utilizing laser intensities which produce hotter plasma than the optimum emission temperatures allows increasing CE for all considered sources that, however, restricted by the reabsorption processes around the main emission region and this restriction is especially actual for the 6.× nm sources.
Deviation from threshold model in ultrafast laser ablation of graphene at sub-micron scale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gil-Villalba, A.; Xie, C.; Salut, R.

We investigate a method to measure ultrafast laser ablation threshold with respect to spot size. We use structured complex beams to generate a pattern of craters in CVD graphene with a single laser pulse. A direct comparison between beam profile and SEM characterization allows us to determine the dependence of ablation probability on spot-size, for crater diameters ranging between 700 nm and 2.5 μm. We report a drastic decrease of ablation probability when the crater diameter is below 1 μm which we interpret in terms of free-carrier diffusion.
Highly stable, efficient Tm-doped fiber laser—a potential scalpel for low invasive surgery

NASA Astrophysics Data System (ADS)

Michalska, M.; Brojek, W.; Rybak, Z.; Sznelewski, P.; Mamajek, M.; Swiderski, J.

2016-11-01

We report an all-fiber, diode-pumped, continuous-wave Tm3+-doped fiber laser emitting 37.4 W of output power with a slope efficiency as high as 57% with respect to absorbed pump power at 790 nm. The laser operated at ~1.94 µm and the output beam quality factor M 2 was measured to be ~1.2. The output beam was very stable with power fluctuations <1% measured over 1 h. The laser system is to be implemented as a scalpel for low-invasive soft-tissue surgery.
High power single-frequency and frequency-doubled laser with active compensation for the thermal lens effect of terbium gallium garnet crystal.

PubMed

Yin, Qiwei; Lu, Huadong; Su, Jing; Peng, Kunchi

2016-05-01

The thermal lens effect of terbium gallium garnet (TGG) crystal in a high power single-frequency laser severely limits the output power and the beam quality of the laser. By inserting a potassium dideuterium phosphate (DKDP) slice with negative thermo-optical coefficient into the laser resonator, the harmful influence of the thermal lens effect of the TGG crystal can be effectively mitigated. Using this method, the stable range of the laser is broadened, the bistability phenomenon of the laser during the process of changing the pump power is completely eliminated, the highest output power of an all-solid-state continuous-wave intracavity-frequency-doubling single-frequency laser at 532 nm is enhanced to 30.2 W, and the beam quality of the laser is significantly improved.
A double-stream Xe:He jet plasma emission in the vicinity of 6.7 nm

NASA Astrophysics Data System (ADS)

Chkhalo, N. I.; Garakhin, S. A.; Golubev, S. V.; Lopatin, A. Ya.; Nechay, A. N.; Pestov, A. E.; Salashchenko, N. N.; Toropov, M. N.; Tsybin, N. N.; Vodopyanov, A. V.; Yulin, S.

2018-05-01

We present the results of investigations of extreme ultraviolet (EUV) light emission in the range from 5 to 10 nm. The light source was a pulsed "double-stream" Xe:He gas jet target irradiated by a laser beam with a power density of ˜1011 W/cm2. The radiation spectra were measured with a Czerny-Turner monochromator with a plane diffraction grating. The conversion efficiency of the laser energy into EUV radiation caused by Xe+14…+16 ion emission in the range of 6-8 nm was measured using a calibrated power meter. The conversion efficiency of the laser radiation into EUV in the vicinity of 6.7 nm was (2.17 ± 0.13)% in a 1 nm spectral band. In the spectral band of the real optical system (0.7% for La/B multilayer mirrors) emitted into the half-space, it was (0.1 ± 0.006)%. The results of this study provide an impetus for further research on laser plasma sources for maskless EUV lithography at a wavelength of 6.7 nm.
Myocardium tissue ablation with high-peak-power nanosecond 1,064- and 532-nm pulsed lasers: influence of laser-induced plasma.

PubMed

Ogura, Makoto; Sato, Shunichi; Ishihara, Miya; Kawauchi, Satoko; Arai, Tunenori; Matsui, Takemi; Kurita, Akira; Kikuchi, Makoto; Ashida, Hiroshi; Obara, Minoru

2002-01-01

We investigated the mechanism and characteristics of porcine myocardium tissue ablation in vitro with nanosecond 1,064- and 532-nm pulsed lasers at laser intensities up to approximately 5.0 GW/cm(2). Particular attention was paid to study the influence of the laser-induced plasma on the ablation characteristics. The applicability of these two lasers to transmyocardial laser revascularization (TMLR) was discussed. Porcine myocardium tissue samples were irradiated with 1,064- and 532-nm, Q-switched Nd:YAG laser pulses, and the ablation depths were measured. The temporal profiles of the laser-induced optical emissions were measured with a biplanar phototube. For the ablated tissue samples, histological analysis was performed with an optical microscope and a polarization microscope. The ablation efficiency at 1,064 nm was higher than that at 532 nm. The ablation threshold at 1,064 nm (approximately 0.8 GW/cm(2)) was lower than that at 532 nm (approximately 1.6 GW/cm(2)), in spite of the lower absorption coefficient being expected at 1,064 nm. For the 1,064-nm laser-ablated tissues, thermal damage was very limited, while damage presumably caused by the mechanical effect was observed in most of the cases. For the 1,064-nm laser ablation, the ablation threshold was equal to the threshold of the laser-induced optical emission (approximately 0.8 GW/cm(2)), while for the 532-nm laser ablation, the optical emission threshold ( approximately 2.4 GW/cm(2)) was higher than the ablation threshold. We considered that for the 1,064-nm laser ablation, the tissue removal was achieved through a photodisruption process at laser intensities of > approximately 0.8 GW/cm(2). At laser intensities of > 3.0 GW/cm(2), however, the ablation efficiency decreased; this can be attributed to the absorption of incoming laser pulses by the plasma. For the 532-nm laser ablation, the tissue removal was achieved through a photothermal process at laser intensities of > approximately 1.6 GW/cm(2). At laser intensities of > 2.4 GW/cm(2), a photodisruption process may also contribute to the tissue removal, in addition to a photothermal process. With regard to the ablation rates, the 1,064-nm laser was more suitable for TMLR than the 532-nm laser. We concluded that the 1,064-nm Q-switched Nd:YAG laser would be a potential candidate for a laser source for TMLR because of possible fiber-based beam delivery, its compact structure, cost effectiveness, and easy maintenance. Animal trials, however, have to be carried out to evaluate the influence of the tissue damage. Copyright 2002 Wiley-Liss, Inc.
Time-resolved measurements of the angular distribution of lasing at 23.6 nm in Ne-like germanium

NASA Astrophysics Data System (ADS)

Kodama, R.; Neely, D.; Dwivedi, L.; Key, M. H.; Krishnan, J.; Lewis, C. L. S.; O'Neill, D.; Norreys, P.; Pert, G. J.; Ramsden, S. A.; Tallents, G. J.; Uhomoibhi, J.; Zhang, J.

1992-06-01

The time dependence of the angular distribution of soft X-ray lasing at 23.6 nm in Ne-like germanium has been measured using a streak camera. Slabs of germanium have been irradiated over ≈ 22 mm length × 100 μm width with three line focussed beams of the SERC Rutherford Appleton Laboratory VULCAN laser at 1.06 μm wavelength. The laser beam sweeps in time towards the target surface plane and the divergence broadens with time. The change of the peak intensity pointing and the broadening of the profile with time are consistent with expectations of the time dependence of refraction and divergence due to density gradients in the plasma.
Progress on CBET Platform at the Nike Laser

NASA Astrophysics Data System (ADS)

Weaver, J. L.; McKenty, P.; Oh, J.; Kehne, D.; Schmitt, A. J.; Obenschain, S.; Serlin, V.; Lehmberg, R.; Tsung, F.

2015-11-01

Cross-beam energy transport (CBET) studies are underway at the Nike krypton-fluoride (KrF) laser at NRL. This facility has unique characteristics that provide an excellent platform for CBET work - including short wavelength (248 nm), large bandwidth (1-3 THz), beam smoothing by induced spatial incoherence (ISI), and full aperture focal spot zooming. Nike's two beam arrays are widely separated (135° in azimuth) which facilitates CBET studies in a nearly opposing geometry, relevant to Polar Direct Drive implosions. Various target types are planned: planar slabs, cylindrical and spherical shells, and low-density targets. The solid targets will be used to examine gradient geometries and the latter will access larger volume, more uniform plasmas. The initial campaign is exploring changes observed by scattered light diagnostics for both beam arrays as the probe laser spectrum is modified. Work supported by DoE/NNSA.
High Efficiency Electron-Laser Interactions in Tapered Helical Undulators

NASA Astrophysics Data System (ADS)

Duris, Joseph Patrick

Efficient coupling of relativistic electron beams with high power radiation lies at the heart of advanced accelerator and light source research and development. The inverse free electron laser is a stable accelerator capable of harnessing very high intensity laser electric fields to efficiently transfer large powers from lasers to electron beams. In this dissertation, we first present the theoretical framework to describe the interaction, and then apply our improved understanding of the IFEL to the design and numerical study of meter-long, GeV IFELs for compact light sources. The central experimental work of the dissertation is the UCLA BNL helical inverse free electron laser experiment at the Accelerator Test Facility in Brookhaven National Laboratory which used a strongly tapered 54cm long, helical, permanent magnet undulator and a several hundred GW CO2 laser to accelerate electrons from 52 to 106MeV, setting new records for inverse free electron laser energy gain (54MeV) and average accelerating gradient (100MeV/m). The undulator design and fabrication as well as experimental diagnostics are presented. In order to improve the stability and quality of the accelerated electron beam, we redesigned the undulator for a slightly reduced output energy by modifying the magnet gap throughout the undulator, and we used this modified undulator to demonstrated capture of >25% of the injected beam without prebunching. In the study of heavily loaded GeV inverse free electron lasers, we show that a majority of the power may be transferred from a laser to the accelerated electron beam. Reversing the process to decelerate high power electron beams, a mechanism we refer to as tapering enhanced stimulated superradiant amplification, offers a clear path to high power light sources. We present studies of radiation production for a wide range of wavelengths (10mum, 13nm, and 0.3nm) using this method and discuss the design for a deceleration experiment using the same undulator used for acceleration in this experiment. By accounting for the evolving radiation field in the design of the undulator tapering, a large fraction of energy may be transferred between the electrons and laser, enabling compact, high-current GeV accelerators and various wavelength light-sources of unprecedented peak powers.
Radiation damage to amorphous carbon thin films irradiated by multiple 46.9 nm laser shots below the single-shot damage threshold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Juha, L.; Hajkova, V.; Vorlicek, V.

2009-05-01

High-surface-quality amorphous carbon (a-C) optical coatings with a thickness of 45 nm, deposited by magnetron sputtering on a silicon substrate, were irradiated by the focused beam of capillary-discharge Ne-like Ar extreme ultraviolet laser (CDL=capillary-discharge laser; XUV=extreme ultraviolet, i.e., wavelengths below 100 nm). The laser wavelength and pulse duration were 46.9 nm and 1.7 ns, respectively. The laser beam was focused onto the sample surface by a spherical Sc/Si multilayer mirror with a total reflectivity of about 30%. The laser pulse energy was varied from 0.4 to 40 muJ on the sample surface. The irradiation was carried out at five fluencemore » levels between 0.1 and 10 J/cm{sup 2}, accumulating five different series of shots, i.e., 1, 5, 10, 20, and 40. The damage to the a-C thin layer was investigated by atomic force microscopy (AFM) and Nomarski differential interference contrast (DIC) optical microscopy. The dependence of the single-shot-damaged area on pulse energy makes it possible to determine a beam spot diameter in the focus. Its value was found to be equal to 23.3+-3.0 mum using AFM data, assuming the beam to have a Gaussian profile. Such a plot can also be used for a determination of single-shot damage threshold in a-C. A single-shot threshold value of 1.1 J/cm{sup 2} was found. Investigating the consequences of the multiple-shot exposure, it has been found that an accumulation of 10, 20, and 40 shots at a fluence of 0.5 J/cm{sup 2}, i.e., below the single-shot damage threshold, causes irreversible changes of thin a-C layers, which can be registered by both the AFM and the DIC microscopy. In the center of the damaged area, AFM shows a-C removal to a maximum depth of 0.3, 1.2, and 1.5 nm for 10-, 20- and 40-shot exposure, respectively. Raman microprobe analysis does not indicate any change in the structure of the remaining a-C material. The erosive behavior reported here contrasts with the material expansion observed earlier [L. Juha et al., Proc. SPIE 5917, 91 (2005)] on an a-C sample irradiated by a large number of femtosecond pulses of XUV high-order harmonics.« less
A combined remote Raman and LIBS instrument for characterizing minerals with 532 nm laser excitation.

PubMed

Sharma, Shiv K; Misra, Anupam K; Lucey, Paul G; Lentz, Rachel C F

2009-08-01

The authors have developed an integrated remote Raman and laser-induced breakdown spectroscopy (LIBS) system for measuring both the Raman and LIBS spectra of minerals with a single 532 nm laser line of 35 mJ/pulse and 20 Hz. The instrument has been used for analyzing both Raman and LIBS spectra of carbonates, sulfates, hydrous and anhydrous silicates, and iron oxide minerals in air. These experiments demonstrate that by focusing a frequency-doubled 532 nm Nd:YAG pulsed laser beam with a 10x beam expander to a 529-microm diameter spot on a mineral surface located at 9 m, it is possible to measure simultaneously both the remote Raman and LIBS spectra of calcite, gypsum and olivine by adjusting the laser power electronically. The spectra of calcite, gypsum, and olivine contain fingerprint Raman lines; however, it was not possible to measure the remote Raman spectra of magnetite and hematite at 9 m because of strong absorption of 532 nm laser radiation and low intensities of Raman lines from these minerals. The remote LIBS spectra of both magnetite and hematite contain common iron emission lines but show difference in the minor amount of Li present in these two minerals. Remote Raman and LIBS spectra of a number of carbonates, sulfates, feldspars and phyllosilicates at a distance of 9 m were measured with a 532-nm laser operating at 35 mJ/pulse and by changing photon flux density at the sample by varying the spot diameter from 10 mm for Raman to 530 microm for LIBS measurements. The complementary nature of these spectra is highlighted and discussed. The combined Raman and LIBS system can also be re-configured to perform micro-Raman and micro-LIBS analyses, which have applications in trace/residue analysis and analysis of very small samples in the nano-gram range.
Ridge waveguide laser in Nd:LiNbO3 by Zn-diffusion and femtosecond-laser structuring

NASA Astrophysics Data System (ADS)

Martínez de Mendívil, Jon; del Hoyo, Jesús; Solís, Javier; Lifante, Ginés

2016-12-01

Ridge waveguide lasers have been fabricated on Nd3+ doped LiNbO3 crystals. The fs-laser writing technique was used to define ridge structures on a gradient-index planar waveguide fabricated by Zn-diffusion. This planar waveguide was formed in a z-cut LiNbO3 substrate homogeneously doped with a 0.23% of Nd3+ ions. To obtain lateral light confinement, the surface was then micromachined using a multiplexed femtosecond laser writing beam, forming the ridge structures. By butting two mirrors at the channel waveguide end-facets, forming a waveguide laser cavity, TM-polarized laser action at 1085 nm was achieved by end-fire TM-pumping at 815 nm. The waveguide laser shows a threshold of 31 mW, with a 7% of slope efficiency.
Semiconductor laser applications in rheumatology

NASA Astrophysics Data System (ADS)

Pascu, Mihail-Lucian; Suteanu, S.

1996-01-01

Two types of laser diode (LD) based equipment for rheumatology are introduced. The first is a portable device which contains single LD emitting at 890 nm laser pulses (time full width 100 nsec) of reprate tunable within (0.5 - 1.5) kHz; the laser beam average power is 0.7 mW at 1 kHz reprate. The second is computer controlled, contains one HeNe laser and 5 LD allowing 6 modes of patient irradiation (placebo effect evaluation included). HeNe laser works in cw at 632.8 nm; the LD works each as described for the portable equipment. HeNe and LD beams are superposed so that HeNe laser spot in the irradiation plane has a 60 mm diameter and the LD spots covers a 50 mm diameter disc centered on the HeNe laser spot. Clinical applications using the second type of equipment are reported; 1287 patients were treated between October 1991 and October 1994. Female/male ratio was 4:1 and their age distribution was between 18 and 85 years. The average number of exposures was 10 and the mean exposure time was 7 minutes. Studies were made on the treatment of rheumatoid arthritis, seronegative arthritis, degenerative joint diseases, abarticular rheumatism, osteoporosis pain and pains and edema after fractures.
Quasi-three level Nd:YLF fundamental and Raman laser operating under 872-nm and 880-nm direct diode pumping

NASA Astrophysics Data System (ADS)

Wetter, Niklaus U.; Bereczki, Allan; Paes, João. Pedro Fonseca

2018-02-01

Nd:YLiF4 is the gain material of choice whenever outstanding beam quality or a birefringent gain material is necessary such as in certain applications for terahertz radiation or dual-frequency mode-locking. However, for high power CW applications the material is hampered by a low thermal fracture threshold. This problem can be mitigated by special 2D pump set-ups or by keeping the quantum defect to a minimum. Direct pumping into the upper laser level of Nd:YLiF4 is usually performed at 880 nm. For quasi-three level laser emission at 908 nm, direct pumping at this wavelength provides a high quantum defect of 0.97, which allows for very high CW pump powers. Although the direct pumping transition to the upper laser state at 872 nm has a slightly smaller quantum defect of 0.96, its pump absorption cross section along the c-axis is 50% higher than at 880 nm, leading to a higher absorption efficiency. In this work we explore, for the first time to our knowledge, 908 nm lasing under 872 nm diode pumping and compare the results with 880 nm pumping for quasicw and cw operation. By inserting a KGW crystal in the cavity, Raman lines at 990 nm and 972 nm were obtained for the first time from a directly pumped 908 nm Nd:YLF fundamental laser for both quasi-cw and cw conditions.
Ion beam production and study of radioactive isotopes with the laser ion source at ISOLDE

NASA Astrophysics Data System (ADS)

Fedosseev, Valentin; Chrysalidis, Katerina; Day Goodacre, Thomas; Marsh, Bruce; Rothe, Sebastian; Seiffert, Christoph; Wendt, Klaus

2017-08-01

At ISOLDE the majority of radioactive ion beams are produced using the resonance ionization laser ion source (RILIS). This ion source is based on resonant excitation of atomic transitions by wavelength tunable laser radiation. Since its installation at the ISOLDE facility in 1994, the RILIS laser setup has been developed into a versatile remotely operated laser system comprising state-of-the-art solid state and dye lasers capable of generating multiple high quality laser beams at any wavelength in the range of 210-950 nm. A continuous programme of atomic ionization scheme development at CERN and at other laboratories has gradually increased the number of RILIS-ionized elements. At present, isotopes of 40 different elements have been selectively laser-ionized by the ISOLDE RILIS. Studies related to the optimization of the laser-atom interaction environment have yielded new laser ion source types: the laser ion source and trap and the versatile arc discharge and laser ion source. Depending on the specific experimental requirements for beam purity or versatility to switch between different ionization mechanisms, these may offer a favourable alternative to the standard hot metal cavity configuration. In addition to its main purpose of ion beam production, the RILIS is used for laser spectroscopy of radioisotopes. In an ongoing experimental campaign the isotope shifts and hyperfine structure of long isotopic chains have been measured by the extremely sensitive in-source laser spectroscopy method. The studies performed in the lead region were focused on nuclear deformation and shape coexistence effects around the closed proton shell Z = 82. The paper describes the functional principles of the RILIS, the current status of the laser system and demonstrated capabilities for the production of different ion beams including the high-resolution studies of short-lived isotopes and other applications of RILIS lasers for ISOLDE experiments. This article belongs to the Focus on Exotic Beams at ISOLDE: A Laboratory Portrait special issue.
Structured optical vortices with broadband comb-like optical spectra in Yb:Y3Al5O12/YVO4 Raman microchip laser

NASA Astrophysics Data System (ADS)

Dong, Jun; Wang, Xiaolei; Zhang, Mingming; Wang, Xiaojie; He, Hongsen

2018-04-01

Structured optical vortices with 4 phase singularities have been generated in a laser diode pumped continuous-wave Yb:Y3Al5O12/YVO4 (Yb:YAG/YVO4) Raman microchip laser. The broadband comb-like first order Stokes laser emitting spectrum including 30 longitudinal modes covers from 1072.49 nm to 1080.13 nm with a bandwidth of 7.64 nm, which is generated with the Raman shift 259 cm-1 of the c-cut YVO4 crystal converted from the fundamental laser around 1.05 μm. Pump power dependent optical vortex beams are attributed to overlap of the Stokes laser field with the fundamental laser field caused by dynamically changing the coupling losses of the fundamental laser field. The maximum output power is 1.16 W, and the optical-to-optical efficiency is 18.4%. This work provides a method for generating structured optical vortices with an optical frequency comb in solid-state Raman microchip lasers, which have potential applications in quantum computations, micro-machining, and information processing.

Laser-induced retinal damage thresholds for annular retinal beam profiles

NASA Astrophysics Data System (ADS)

Kennedy, Paul K.; Zuclich, Joseph A.; Lund, David J.; Edsall, Peter R.; Till, Stephen; Stuck, Bruce E.; Hollins, Richard C.

2004-07-01

The dependence of retinal damage thresholds on laser spot size, for annular retinal beam profiles, was measured in vivo for 3 μs, 590 nm pulses from a flashlamp-pumped dye laser. Minimum Visible Lesion (MVL)ED50 thresholds in rhesus were measured for annular retinal beam profiles covering 5, 10, and 20 mrad of visual field; which correspond to outer beam diameters of roughly 70, 160, and 300 μm, respectively, on the primate retina. Annular beam profiles at the retinal plane were achieved using a telescopic imaging system, with the focal properties of the eye represented as an equivalent thin lens, and all annular beam profiles had a 37% central obscuration. As a check on experimental data, theoretical MVL-ED50 thresholds for annular beam exposures were calculated using the Thompson-Gerstman granular model of laser-induced thermal damage to the retina. Threshold calculations were performed for the three experimental beam diameters and for an intermediate case with an outer beam diameter of 230 μm. Results indicate that the threshold vs. spot size trends, for annular beams, are similar to the trends for top hat beams determined in a previous study; i.e., the threshold dose varies with the retinal image area for larger image sizes. The model correctly predicts the threshold vs. spot size trends seen in the biological data, for both annular and top hat retinal beam profiles.
Characteristics of 1.9-μm laser emission from hydrogen-filled hollow-core fiber by vibrational stimulated Raman scattering

NASA Astrophysics Data System (ADS)

Gu, Bo; Chen, Yubin; Wang, Zefeng

2016-12-01

We report here the characteristics of 1.9-μm laser emission from a gas-filled hollow-core fiber by stimulated Raman scattering (SRS). A 6.5-m hydrogen-filled ice-cream negative curvature hollow-core fiber is pumped with a high peak-power, narrow linewidth, linearly polarized subnanosecond pulsed 1064-nm microchip laser, generating a pulsed vibrational Stokes wave at 1908.5 nm. The maximum quantum efficiency of about 48% is obtained, which is mainly limited by the mode mismatch between the pump laser beam and the Stokes wave in the hollow-core fiber. The linewidths of the pump laser and the first-order vibrational Stokes wave are measured to be about 1 and 2 GHz, respectively, by a scanning Fabry-Perot interferometer. The pressure selection phenomenon of the vibrational anti-Stokes waves is also investigated. The pulse duration of the vibrational Stokes wave is recorded to be narrower than that of the pump laser. The polarization properties of the hollow-core fiber and the polarization dependence of the vibrational and the rotational SRS are also studied. The beam profile of the vibrational Stokes wave shows good quality.
Studies on 405nm blue-violet diode laser with external grating cavity

NASA Astrophysics Data System (ADS)

Li, Bin; Gao, Jun; Zhao, Jun; Yu, Anlan; Luo, Shiwen; Xiong, Dongsheng; Wang, Xinbing; Zuo, Duluo

2016-03-01

Spectroscopy applications of free-running laser diodes (LD) are greatly restricted as its broad band spectral emission. And the power of a single blue-violet LD is around several hundred milliwatts by far, it is of great importance to obtain stable and narrow line-width laser diodes with high efficiency. In this paper, a high efficiency external cavity diode laser (ECDL) with high output power and narrow band emission at 405 nm is presented. The ECDL is based on a commercially available LD with nominal output power of 110 mW at an injection current of 100 mA. The spectral width of the free-running LD is about 1 nm (FWHM). A reflective holographic grating which is installed on a home-made compact adjustable stage is utilized for optical feedback in Littrow configuration. In this configuration, narrow line-width operation is realized and the effects of grating groove density as well as the groove direction related to the beam polarization on the performances of the ECDL are experimentally investigated. In the case of grating with groove density of 3600 g/mm, the threshold is reduced from 21 mA to 18.3 mA or 15.6 mA and the tuning range is 3.95 nm or 6.01 nm respectively when the grating is orientated in TE or TM polarization. In addition, an output beam with a line-width of 30 pm and output power of 92.7 mW is achieved in TE polarization. With these narrow line-width and high efficiency, the ECDL is capable to serve as a light source for spectroscopy application such as Raman scattering and laser induced fluorescence.
Nanosecond pulse lasers for retinal applications.

PubMed

Wood, John P M; Plunkett, Malcolm; Previn, Victor; Chidlow, Glyn; Casson, Robert J

2011-08-01

Thermal lasers are routinely used to treat certain retinal disorders although they cause collateral damage to photoreceptors. The current study evaluated a confined, non-conductive thermal, 3-nanosecond pulse laser in order to determine how to produce the greatest therapeutic range without causing collateral damage. Data were compared with that obtained from a standard thermal laser. Porcine ocular explants were used; apposed neuroretina was also in place for actual laser treatment. After treatment, the retina was removed and a calcein-AM assay was used to assess retinal pigmented epithelium (RPE) cell viability in the explants. Histological methods were also employed to examine lased transverse explant sections. Three nanoseconds pulse lasers with either speckle- or gaussian-beam profile were employed in the study. Comparisons were made with a 100 milliseconds continuous wave (CW) 532 nm laser. The therapeutic energy range ratio was defined as the minimum visible effect threshold (VET) versus the minimum detectable RPE kill threshold. The 3-nanosecond lasers produced markedly lower minimum RPE kill threshold levels than the CW laser (e.g., 36 mJ/cm(2) for speckle-beam and 89 mJ/cm(2) for gaussian-beam profile nanosecond lasers vs. 7,958 mJ/cm(2) for CW laser). VET values were also correspondingly lower for the nanosecond lasers (130 mJ/cm(2) for 3 nanoseconds speckle-beam and 219 mJ/cm(2) for gaussian-beam profile vs. 1,0346 mJ/cm(2) for CW laser). Thus, the therapeutic range ratios obtained with the nanosecond lasers were much more favorable than that obtained by the CW laser: 3.6:1 for the speckle-beam and 2.5:1 for the gaussian-beam profile 3-nanosecond lasers versus 1.3:1 for the CW laser. Nanosecond lasers, particularly with a speckle-beam profile, provide a much wider therapeutic range of energies over which RPE treatment can be performed, without damage to the apposed retina, as compared with conventional CW lasers. These results may have important implications for the treatment of retinal disease. Copyright © 2011 Wiley-Liss, Inc.
Nanoscale surface modification of glass using a 1064 nm pulsed laser

NASA Astrophysics Data System (ADS)

Theppakuttai, Senthil; Chen, Shaochen

2003-07-01

We report a method to produce nanopatterns on borosilicate glass by a Nd:yttrium-aluminum-garnet laser (10 ns, 1064 nm), using silica nanospheres. Nonlinear absorption of the enhanced optical field between the spheres and glass sample is believed to be the primary reason for the creation of nanofeatures on the glass substrate. By shining the laser beam from the backside of the glass sample, the scattering effects are minimized and only the direct field enhancement due to the spheres is utilized for surface patterning. To confirm this, calculations based on the Mie scattering theory were performed, and the resulting intensity as a function of scattering angles are presented. The nanofeatures thus obtained by this method are 350 nm in diameter and the distance between them is around 640 nm, which is same as the size of spheres used.
Two-color ionization injection using a plasma beatwave accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroeder, C. B.; Benedetti, C.; Esarey, E.

Two-color laser ionization injection is a method to generate ultra-low emittance (sub-100 nm transverse normalized emittance) beams in a laser-driven plasma accelerator. A plasma beatwave accelerator is proposed to drive the plasma wave for ionization injection, where the beating of the lasers effectively produces a train of long-wavelength pulses. The plasma beatwave accelerator excites a large amplitude plasma wave with low peak laser electric fields, leaving atomically-bound electrons with low ionization potential. A short-wavelength, low-amplitude ionization injection laser pulse (with a small ponderomotive force and large peak electric field) is used to ionize the remaining bound electrons at a wakemore » phase suitable for trapping, generating an ultra-low emittance electron beam that is accelerated in the plasma wave. Using a plasma beatwave accelerator for wakefield excitation, compared to short-pulse wakefield excitation, allows for a lower amplitude injection laser pulse and, hence, a lower emittance beam may be generated.« less
Two-color ionization injection using a plasma beatwave accelerator

DOE PAGES

Schroeder, C. B.; Benedetti, C.; Esarey, E.; ...

2018-01-10

Two-color laser ionization injection is a method to generate ultra-low emittance (sub-100 nm transverse normalized emittance) beams in a laser-driven plasma accelerator. A plasma beatwave accelerator is proposed to drive the plasma wave for ionization injection, where the beating of the lasers effectively produces a train of long-wavelength pulses. The plasma beatwave accelerator excites a large amplitude plasma wave with low peak laser electric fields, leaving atomically-bound electrons with low ionization potential. A short-wavelength, low-amplitude ionization injection laser pulse (with a small ponderomotive force and large peak electric field) is used to ionize the remaining bound electrons at a wakemore » phase suitable for trapping, generating an ultra-low emittance electron beam that is accelerated in the plasma wave. Using a plasma beatwave accelerator for wakefield excitation, compared to short-pulse wakefield excitation, allows for a lower amplitude injection laser pulse and, hence, a lower emittance beam may be generated.« less
Continuous-wave dual-wavelength operation of a distributed feedback laser diode with an external cavity using a volume Bragg grating

NASA Astrophysics Data System (ADS)

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 (<0.29 nm) and was used as a single-wavelength source. A volume Bragg grating was used as an output coupler for the external-cavity DFB laser to output another stable wavelength beam with a narrow bandwidth of 0.27 nm. A frequency difference for dual-wavelength operation of 0.88 THz was achieved and an output power of up to 415 mW was obtained. The external-cavity DFB laser showed a stable dual-wavelength operation over the practical current and temperature ranges.
Destruction of monocrystalline silicon with nanosecond pulsed fiber laser accompanied by the oxidation of ablation microparticles

NASA Astrophysics Data System (ADS)

Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

2013-11-01

In this work, we report an observation of process of local destruction monocrystalline silicon with a scanning beam irradiation of pulse ytterbium fiber laser with a wavelength λ= 1062 nm, accompanied by the oxidation of ablation microparticles. It is shown that depending on the power density of irradiation was observed a large scatter size of the microparticles. From a certain average power density is observed beginning oxidation particulate emitted from the surface of the irradiated area. By varying the parameters of the laser beam such as scanning speed, pulse repetition rate, overlap of laser spot, radiation dose can be achieved almost complete oxidation of all formed during the ablation of microparticles.
Note: A pulsed laser ion source for linear induction accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, H., E-mail: bamboobbu@hotmail.com; School of Physics, Peking University, Beijing 100871; Zhang, K.

2015-01-15

We have developed a high-current laser ion source for induction accelerators. A copper target was irradiated by a frequency-quadrupled Nd:YAG laser (266 nm) with relatively low intensities of 10{sup 8} W/cm{sup 2}. The laser-produced plasma supplied a large number of Cu{sup +} ions (∼10{sup 12} ions/pulse) during several microseconds. Emission spectra of the plasma were observed and the calculated electron temperature was about 1 eV. An induction voltage adder extracted high-current ion beams over 0.5 A/cm{sup 2} from a plasma-prefilled gap. The normalized beam emittance measured by a pepper-pot method was smaller than 1 π mm mrad.
Multi-Beam Surface Lidar for Lunar and Planetary Mapping

NASA Technical Reports Server (NTRS)

Bufton, Jack L.; Garvin, James B.

1998-01-01

Surface lidar techniques are now being demonstrated in low Earth orbit with a single beam of pulsed laser radiation at 1064 nm that profiles the vertical structure of Earth surface landforms along the nadir track of a spacecraft. In addition, a profiling laser altimeter, called MOLA, is operating in elliptical Martian orbit and returning surface topography data. These instruments form the basis for suggesting an improved lidar instrument that employs multiple beams for extension of sensor capabilities toward the goal of true, 3-dimensional mapping of the Moon or other similar planetary surfaces. In general the lidar waveform acquired with digitization of a laser echo can be used for laser distance measurement (i.e. range-to-the-surface) by time-of-flight measurement and for surface slope and shape measurements by examining the detailed lidar waveform. This is particularly effective when the intended target is the lunar surface or another planetary body free of any atmosphere. The width of the distorted return pulse is a first order measure of the surface incidence angle, a combination of surface slope and laser beam pointing. Assuming an independent and absolute (with respect to inertial space) measurement of laser beam pointing on the spacecraft, it is possible to derive a surface slope with-respect-to the mean planetary surface or its equipotential gravity surface. Higher-order laser pulse distortions can be interpreted in terms of the vertical relief of the surface or reflectivity variations within the area of the laser beam footprint on the surface.
Laser Ablation of Dental Calculus Around 400 nm Using a Ti:Sapphire Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schoenly, J.; Seka, W.; Rechmann, P.

2009-10-19

A Nd:YAG laser-pumped, frequency-doubled Ti:sapphire laser is used for selective ablation of calculus. The laser provides ≤25 mJ at 400 nm (60-ns pulse width, 10-Hz repetition rate). The laser is coupled into an optical multimode fiber coiled around a 4-in.-diam drum to generate a top-hat output intensity profile. With coaxial water cooling, this is ideal for efficient, selective calculus removal. This is in stark contrast with tightly focused Gaussian beams that are energetically inefficient and lead to irreproducible results. Calculus is well ablated at high fluences ≥2 J/cm^2; stalling occurs below this fluence because of photobleaching. Healthy hard tissue ismore » not removed at fluences ≤3 J/cm^2.« less
Field mappers for laser material processing

NASA Astrophysics Data System (ADS)

Blair, Paul; Currie, Matthew; Trela, Natalia; Baker, Howard J.; Murphy, Eoin; Walker, Duncan; McBride, Roy

2016-03-01

The native shape of the single-mode laser beam used for high power material processing applications is circular with a Gaussian intensity profile. Manufacturers are now demanding the ability to transform the intensity profile and shape to be compatible with a new generation of advanced processing applications that require much higher precision and control. We describe the design, fabrication and application of a dual-optic, beam-shaping system for single-mode laser sources, that transforms a Gaussian laser beam by remapping - hence field mapping - the intensity profile to create a wide variety of spot shapes including discs, donuts, XY separable and rotationally symmetric. The pair of optics transform the intensity distribution and subsequently flatten the phase of the beam, with spot sizes and depth of focus close to that of a diffraction limited beam. The field mapping approach to beam-shaping is a refractive solution that does not add speckle to the beam, making it ideal for use with single mode laser sources, moving beyond the limits of conventional field mapping in terms of spot size and achievable shapes. We describe a manufacturing process for refractive optics in fused silica that uses a freeform direct-write process that is especially suited for the fabrication of this type of freeform optic. The beam-shaper described above was manufactured in conventional UV-fused silica using this process. The fabrication process generates a smooth surface (<1nm RMS), leading to laser damage thresholds of greater than 100J/cm2, which is well matched to high power laser sources. Experimental verification of the dual-optic filed mapper is presented.
Single-frequency, fully integrated, miniature DPSS laser based on monolithic resonator

NASA Astrophysics Data System (ADS)

Dudzik, G.; Sotor, J.; Krzempek, K.; Soboń, G.; Abramski, K. M.

2014-02-01

We present a single frequency, stable, narrow linewidth, miniature laser sources operating at 532 nm (or 1064 nm) based on a monolithic resonators. Such resonators utilize birefringent filters formed by YVO4 beam displacer and KTP or YVO4 crystals to force single frequency operation at 532 nm or 1064 nm, respectively. In both configurations Nd:YVO4 gain crystal is used. The resonators dimensions are 1x1x10.5 mm3 and 1x1x8.5 mm3 for green and infrared configurations, respectively. Presented laser devices, with total dimensions of 40x52x120 mm3, are fully equipped with driving electronics, pump diode, optical and mechanical components. The highly integrated (36x15x65 mm3) low noise driving electronics with implemented digital PID controller was designed. It provides pump current and resonator temperature stability of ±30 μA@650 mA and ±0,003ºC, respectively. The laser parameters can be set and monitored via the USB interface by external application. The developed laser construction is universal. Hence, the other wavelengths can be obtained only by replacing the monolithic resonator. The optical output powers in single frequency regime was at the level of 42 mW@532 nm and 0.5 W@1064 nm with the long-term fluctuations of ±0.85 %. The linewidth and the passive frequency stability under the free running conditions were Δν < 100 kHz and 3ṡ10-9@1 s integration time, respectively. The total electrical power supply consumption of laser module was only 4 W. Presented compact, single frequency laser operating at 532 nm and 1064 nm may be used as an excellent source for laser vibrometry, interferometry or seed laser for fiber amplifiers.
Spectral narrowing of a 980 nm tapered diode laser bar

NASA Astrophysics Data System (ADS)

Vijayakumar, Deepak; Jensen, Ole Bjarlin; Lucas Leclin, Ga"lle; Petersen, Paul Michael; Thestrup, Birgitte

2011-03-01

High power diode laser bars are interesting in many applications such as solid state laser pumping, material processing, laser trapping, laser cooling and second harmonic generation. Often, the free running laser bars emit a broad spectrum of the order of several nanometres which limit their scope in wavelength specific applications and hence, it is vital to stabilize the emission spectrum of these devices. In our experiment, we describe the wavelength narrowing of a 12 element 980 nm tapered diode laser bar using a simple Littman configuration. The tapered laser bar which suffered from a big smile has been "smile corrected" using individual phase masks for each emitter. The external cavity consists of the laser bar, both fast and slow axis micro collimators, smile correcting phase mask, 6.5x beam expanding lens combination, a 1200 lines/mm reflecting grating with 85% efficiency in the first order, a slow axis focusing cylindrical lens of 40 mm focal length and an output coupler which is 10% reflective. In the free running mode, the laser emission spectrum was 5.5 nm wide at an operating current of 30A. The output power was measured to be in excess of 12W. Under the external cavity operation, the wavelength spread of the laser could be limited to 0.04 nm with an output power in excess of 8 W at an operating current of 30A. The spectrum was found to be tuneable in a range of 16 nm.
Compact diode laser module at 1116 nm with an integrated optical isolation and a PM-SMF output

NASA Astrophysics Data System (ADS)

Jedrzejczyk, Daniel; Hofmann, Julian; Werner, Nils; Sahm, Alexander; Paschke, Katrin

2017-02-01

In this work, a fiber-coupled diode laser module emitting around 1116 nm with an output power P < 60 mW is realized. As a laser light source a distributed Bragg reflector (DBR) ridge waveguide diode laser is applied. The module comprises temperature stabilizing components, a micro-lens system as well as an optical micro-isolator. At the output, a polarization-maintaining single-mode fiber (PM-SMF) with a core diameter of 5.5 μm and a standard FC/APC connector are utilized. The generated diffraction limited beam is characterized by a narrow linewidth ( δν < 10 MHz) and a high polarization extinction ratio (PER > 25 dB).
Picosecond laser welding of similar and dissimilar materials.

PubMed

Carter, Richard M; Chen, Jianyong; Shephard, Jonathan D; Thomson, Robert R; Hand, Duncan P

2014-07-01

We report picosecond laser welding of similar and dissimilar materials based on plasma formation induced by a tightly focused beam from a 1030 nm, 10 ps, 400 kHz laser system. Specifically, we demonstrate the welding of fused silica, borosilicate, and sapphire to a range of materials including borosilicate, fused silica, silicon, copper, aluminum, and stainless steel. Dissimilar material welding of glass to aluminum and stainless steel has not been previously reported. Analysis of the borosilicate-to-borosilicate weld strength compares well to those obtained using similar welding systems based on femtosecond lasers. There is, however, a strong requirement to prepare surfaces to a high (10-60 nm Ra) flatness to ensure a successful weld.
Two and Three Beam Pumped Optical Parametric Amplifier of Chirped Pulses

NASA Astrophysics Data System (ADS)

Ališauskas, S.; Butkus, R.; Pyragaitė, V.; Smilgevičius, V.; Stabinis, A.; Piskarskas, A.

2010-04-01

We present two and three beam pumped optical parametric amplifier of broadband chirped pulses. The seed pulses from Ti:sapphire oscillator were stretched and amplified in a non-collinear geometry pumping with up to three beams derived from independent laser amplifiers. The signal with ˜90 nm bandwidth was amplified up to 0.72 mJ. The conversion efficiency dependence on intersection angles of pump beams is also revealed.
Bidirectional current triggering in planar devices based on serially connected VO₂ thin films using 965 nm laser diode.

PubMed

Kim, Jihoon; Park, Kyongsoo; Kim, Bong-Jun; Lee, Yong Wook

2016-08-08

By incorporating a 965 nm laser diode, the bidirectional current triggering of up to 30 mA was demonstrated in a two-terminal planar device based on serially connected vanadium dioxide (VO₂) thin films grown by pulsed laser deposition. The bidirectional current triggering was realized by using the focused beams of laser pulses through the photo-thermally induced phase transition of VO₂. The transient responses of laser-triggered currents were also investigated when laser pulses excited the device at a variety of pulse widths and repetition rates of up to 4.0 Hz. A switching contrast between off- and on-state currents was obtained as ~8333, and rising and falling times were measured as ~39 and ~29 ms, respectively, for 50 ms laser pulses.
Modeling of the laser device for the stress therapy

NASA Astrophysics Data System (ADS)

Matveev, Nikolai V.; Shcheglov, Sergey A.; Romanova, Galina E.; Koneva, Ð.¢atiana A.

2017-05-01

Recently there is a great interest to the drug-free methods of treatment of various diseases. For example, audiovisual therapy is used for the stress therapy. The main destination of the method is the health care and well-being. Visual content in the given case is formed when laser radiation is passing through the optical mediums and elements. The therapy effect is achieved owing to the color varying and complicated structure of the picture which is produced by the refraction, dispersion effects, diffraction and interference. As the laser source we use three laser sources with wavelengths of 445 nm, 520 nm and 640 nm and the optical power up to 1 W. The beam is guided to the optical element which is responsible for the final image of the dome surface. The dynamic image can be achieved by the rotating of the optical element when the laser beam is static or by scanning the surface of the element. Previous research has shown that the complexity of the image connected to the therapy effect. The image was chosen experimentally in practice. The evaluation was performed using the fractal dimension calculation for the produced image. In this work we model the optical image on the surface formed by the laser sources together with the optical elements. Modeling is performed in two stages. On the first stage we perform the simple modeling taking into account simple geometrical effects and specify the optical models of the sources.

A new solid-state, frequency-doubled neodymium-YAG photocoagulation system.

PubMed

Jalkh, A E; Pflibsen, K; Pomerantzeff, O; Trempe, C L; Schepens, C L

1988-06-01

We have developed a solid-state laser system that produces a continuous green monochromatic laser beam of 532 nm by doubling the frequency of a neodymium-YAG laser wavelength of 1064 nm with a potassium-titamyl-phosphate crystal. Photocoagulation burns of equal size and intensity were placed in two rabbit eyes with the solid-state laser system and the regular green argon laser system, respectively, using the same slit-lamp mode of delivery. Histologic findings of lesion sections revealed no important differences between the two systems. In theory, the longer wavelength of the solid-state laser offers the advantages of less scattering in ocular media, higher absorption by oxyhemoglobin, and less absorption by macular xanthophyll than the 514-nm wavelength of the regular green argon laser. The solid-state laser has impressive technical advantages: it contains no argon-ion gas tube that wears out and is expensive to replace; it is much more power efficient, and thus considerably smaller and compact; it is sturdier and easily movable; it does not require external cooling; it uses a 220-V monophasic alternating current; and it requires little maintenance.
Femtosecond laser-controlled self-assembly of amorphous-crystalline nanogratings in silicon

NASA Astrophysics Data System (ADS)

Puerto, Daniel; Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan

2016-07-01

Self-assembly (SA) of molecular units to form regular, periodic extended structures is a powerful bottom-up technique for nanopatterning, inspired by nature. SA can be triggered in all classes of solid materials, for instance, by femtosecond laser pulses leading to the formation of laser-induced periodic surface structures (LIPSS) with a period slightly shorter than the laser wavelength. This approach, though, typically involves considerable material ablation, which leads to an unwanted increase of the surface roughness. We present a new strategy to fabricate high-precision nanograting structures in silicon, consisting of alternating amorphous and crystalline lines, with almost no material removal. The strategy can be applied to static irradiation experiments and can be extended into one and two dimensions by scanning the laser beam over the sample surface. We demonstrate that lines and areas with parallel nanofringe patterns can be written by an adequate choice of spot size, repetition rate and scan velocity, keeping a constant effective pulse number (N eff) per area for a given laser wavelength. A deviation from this pulse number leads either to inhomogeneous or ablative structures. Furthermore, we demonstrate that this approach can be used with different laser systems having widely different wavelengths (1030 nm, 800 nm, 400 nm), pulse durations (370 fs, 100 fs) and repetition rates (500 kHz, 100 Hz, single pulse) and that the grating period can also be tuned by changing the angle of laser beam incidence. The grating structures can be erased by irradiation with a single nanosecond laser pulse, triggering recrystallization of the amorphous stripes. Given the large differences in electrical conductivity between the two phases, our structures could find new applications in nanoelectronics.
Femtosecond laser-controlled self-assembly of amorphous-crystalline nanogratings in silicon.

PubMed

Puerto, Daniel; Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan

2016-07-01

Self-assembly (SA) of molecular units to form regular, periodic extended structures is a powerful bottom-up technique for nanopatterning, inspired by nature. SA can be triggered in all classes of solid materials, for instance, by femtosecond laser pulses leading to the formation of laser-induced periodic surface structures (LIPSS) with a period slightly shorter than the laser wavelength. This approach, though, typically involves considerable material ablation, which leads to an unwanted increase of the surface roughness. We present a new strategy to fabricate high-precision nanograting structures in silicon, consisting of alternating amorphous and crystalline lines, with almost no material removal. The strategy can be applied to static irradiation experiments and can be extended into one and two dimensions by scanning the laser beam over the sample surface. We demonstrate that lines and areas with parallel nanofringe patterns can be written by an adequate choice of spot size, repetition rate and scan velocity, keeping a constant effective pulse number (N eff) per area for a given laser wavelength. A deviation from this pulse number leads either to inhomogeneous or ablative structures. Furthermore, we demonstrate that this approach can be used with different laser systems having widely different wavelengths (1030 nm, 800 nm, 400 nm), pulse durations (370 fs, 100 fs) and repetition rates (500 kHz, 100 Hz, single pulse) and that the grating period can also be tuned by changing the angle of laser beam incidence. The grating structures can be erased by irradiation with a single nanosecond laser pulse, triggering recrystallization of the amorphous stripes. Given the large differences in electrical conductivity between the two phases, our structures could find new applications in nanoelectronics.
Microchip laser based on Yb:YAG/V:YAG monolith crystal

NASA Astrophysics Data System (ADS)

Nejezchleb, Karel; Šulc, Jan; Jelínková, Helena; Škoda, Václav

2016-03-01

V:YAG crystal was investigated as a passive Q-switch of longitudinally diode-pumped microchip laser, emitting radiation at wavelength 1030.5 nm. This laser was based on diffusion bonded monolith crystal (diameter 3 mm) which combines in one piece an active laser part (Yb:YAG crystal, 10 at.% Yb/Y, 3 mm long) and saturable absorber (V:YAG crystal, 2 mm long, initial transmission 86 % @ 1031 nm). The microchip resonator consisted of dielectric mirrors directly deposited on the monolith surfaces (pump mirror HT @ 968 nm and HR @ 1031 nm on Yb:YAG part, output coupler with reflection 55 % @ 1031 nm on the V:YAG part). For longitudinal CW pumping of Yb:YAG part, a fibre coupled (core diameter 100 μm, NA = 0.22, emission @ 968 nm) laser diode was used. The laser threshold was 3.8W. The laser slope efficiency for output mean in respect to incident pumping was 16 %. The linearly polarized generated transversal intensity beam profile was close to the fundamental Gaussian mode. The generated pulse length, stable and mostly independent on pumping power, was equal to 1.3 ns (FWHM). The single pulse energy was increasing with the pumping power and for the maximum pumping 9.7W it was 78 μJ which corresponds to the pulse peak-power 56 kW. The maximum Yb:YAG/V:YAG microchip laser mean output power of 1W was reached without observable thermal roll-over. The corresponding Q-switched pulses repetition rate was 13.1 kHz.
Threshold Damage of In vivo Porcine Skin at 2000 nm Laser Irradiation

DTIC Science & Technology

2006-01-01

surgery. J Clin Laser Med Surg 1992; 10:211-216. 8. Shapshay SM, Rebeiz EE, Pankratov MM. Holmium: Yttrium Aluminium Garnet laser-assisted endoscopic...laser-assisted endoscopic sinus surgery: laboratory experience. Laryngoscope 1991 ; 101:142-149. 10. Min K, Leu H, Zweifel K. Quantitative determination...JTF. Choice of clip levels for beam width measurements using knife-edge techniques. IEEE J. Quantum Electron. 1991 ; 27:1098-1104 19. Finney DJ
Heat profiles of laser-irradiated nails

NASA Astrophysics Data System (ADS)

Paasch, Uwe; Nenoff, Pietro; Seitz, Anna-Theresa; Wagner, Justinus A.; Kendler, Michael; Simon, Jan C.; Grunewald, Sonja

2014-01-01

Onychomycosis is a worldwide problem with no tendency for self-healing, and existing systemic treatments achieve disease-free nails in only 35 to 76% of cases. Recently, treatment of nail fungus with a near-infrared laser has been introduced. It is assumed that fungal eradication is mediated by local heat. To investigate if laser treatment has the potential to eradicate fungal hyphae and arthrospores, laser heat application and propagation needs to be studied in detail. This study aimed to measure nail temperatures using real-time videothermography during laser irradiation. Treatment was performed using 808- and 980-nm linear scanning diode lasers developed for hair removal, enabling contact-free homogeneous irradiation of a human nail plate in one pass. Average and peak temperatures increased pass by pass, while the laser beam moved along the nail plates. The achieved mean peak temperatures (808 nm: 74.1 to 112.4°C, 980 nm: 45.8 to 53.5°C), as well as the elevation of average temperatures (808 nm: 29.5 to 38.2°C, 980 nm: 27.1 to 32.6°C) were associated with pain that was equivalent to that of hair removal procedures and was not significantly different for various wavelengths. The linear scanning laser devices provide the benefits of contact-free homogeneous heating of the human nail while ensuring adequate temperature rises.
Heat profiles of laser-irradiated nails.

PubMed

Paasch, Uwe; Nenoff, Pietro; Seitz, Anna-Theresa; Wagner, Justinus A; Kendler, Michael; Simon, Jan C; Grunewald, Sonja

2014-01-01

Onychomycosis is a worldwide problem with no tendency for self-healing, and existing systemic treatments achieve disease-free nails in only 35 to 76% of cases. Recently, treatment of nail fungus with a near-infrared laser has been introduced. It is assumed that fungal eradication is mediated by local heat. To investigate if laser treatment has the potential to eradicate fungal hyphae and arthrospores, laser heat application and propagation needs to be studied in detail. This study aimed to measure nail temperatures using real-time videothermography during laser irradiation. Treatment was performed using 808- and 980-nm linear scanning diode lasers developed for hair removal, enabling contact-free homogeneous irradiation of a human nail plate in one pass. Average and peak temperatures increased pass by pass, while the laser beam moved along the nail plates. The achieved mean peak temperatures (808 nm: 74.1 to 112.4°C, 980 nm: 45.8 to 53.5°C), as well as the elevation of average temperatures (808 nm: 29.5 to 38.2°C, 980 nm: 27.1 to 32.6°C) were associated with pain that was equivalent to that of hair removal procedures and was not significantly different for various wavelengths. The linear scanning laser devices provide the benefits of contact-free homogeneous heating of the human nail while ensuring adequate temperature rises.
Laser system refinements to reduce variability in infarct size in the rat photothrombotic stroke model

PubMed Central

Alaverdashvili, Mariam; Paterson, Phyllis G.; Bradley, Michael P.

2015-01-01

Background The rat photothrombotic stroke model can induce brain infarcts with reasonable biological variability. Nevertheless, we observed unexplained high inter-individual variability despite using a rigorous protocol. Of the three major determinants of infarct volume, photosensitive dye concentration and illumination period were strictly controlled, whereas undetected fluctuation in laser power output was suspected to account for the variability. New method The frequently utilized Diode Pumped Solid State (DPSS) lasers emitting 532 nm (green) light can exhibit fluctuations in output power due to temperature and input power alterations. The polarization properties of the Nd:YAG and Nd:YVO4 crystals commonly used in these lasers are another potential source of fluctuation, since one means of controlling output power uses a polarizer with a variable transmission axis. Thus, the properties of DPSS lasers and the relationship between power output and infarct size were explored. Results DPSS laser beam intensity showed considerable variation. Either a polarizer or a variable neutral density filter allowed adjustment of a polarized laser beam to the desired intensity. When the beam was unpolarized, the experimenter was restricted to using a variable neutral density filter. Comparison with existing method(s) Our refined approach includes continuous monitoring of DPSS laser intensity via beam sampling using a pellicle beamsplitter and photodiode sensor. This guarantees the desired beam intensity at the targeted brain area during stroke induction, with the intensity controlled either through a polarizer or variable neutral density filter. Conclusions Continuous monitoring and control of laser beam intensity is critical for ensuring consistent infarct size. PMID:25840363
Effect of laser beam conditioning on fabrication of clean micro-channel on stainless steel 316L using second harmonic of Q-switched Nd:YAG laser

NASA Astrophysics Data System (ADS)

Singh, Sanasam Sunderlal; Baruah, Prahlad Kr; Khare, Alika; Joshi, Shrikrishna N.

2018-02-01

Laser micromachining of metals for fabrication of micro-channels generate ridge formation along the edges accompanied by ripples along the channel bed. The ridge formation is due to the formation of interference pattern formed by back reflections from the beam splitter and other optical components involved before focusing on the work piece. This problem can be curtailed by using a suitable aperture or Iris diaphragm so as to cut the unwanted portion of the laser beam before illuminating the sample. This paper reports an experimental investigation on minimizing this problem by conditioning the laser beam using an Iris diaphragm and using optimum process parameters. In this work, systematic experiments have been carried out using the second harmonic of a Q-switched Nd:YAG laser to fabricate micro-channels. Initial experiments revealed that formation of ridges along the sides of micro-channel can easily be minimized with the help of Iris diaphragm. Further it is noted that a clean micro-channel of depth 43.39 μm, width up to 64.49 μm and of good surface quality with average surface roughness (Ra) value of 370 nm can be machined on stainless steel (SS) 316L by employing optimum process condition: laser beam energy of 30 mJ/pulse, 11 number of laser scans and scan speed of 169.54 μm/s with an opening of 4 mm diameter of Iris diaphragm in the path of the laser beam.
Ultraviolet optical and microstructural properties of MgF2 and LaF3 coatings deposited by ion-beam sputtering and boat and electron-beam evaporation

NASA Astrophysics Data System (ADS)

Ristau, Detlev; Gunster, Stefan; Bosch, Salvador; Duparre, Angela; Masetti, Enrico; Ferre-Borrull, Josep; Kiriakidis, George; Peiro, Francesca; Quesnel, Etienne; Tikhonravov, Alexander

2002-06-01

Single layers of MgF2 and LaF3 were deposited upon superpolished fused-silica and CaF2 substrates by ion-beam sputtering (IBS) as well as by boat and electron beam (e-beam) evaporation and were characterized by a variety of complementary analytical techniques. Besides undergoing photometric and ellipsometric inspection, the samples were investigated at 193 and 633 nm by an optical scatter measurement facility. The structural properties were assessed with atomic-force microscopy, x-ray diffraction, TEM techniques that involved conventional thinning methods for the layers. For measurement of mechanical stress in the coatings, special silicon substrates were coated and analyzed. The dispersion behavior of both deposition materials, which was determined on the basis of various independent photometric measurements and data reduction techniques, is in good agreement with that published in the literature and with the bulk properties of the materials. The refractive indices of the MgF2 coatings ranged from 1.415 to 1.440 for the wavelength of the ArF excimer laser (193 nm) and from 1.435 to 1.465 for the wavelength of the F2 excimer laser (157 nm). For single layers of LaF3 the refractive indices extended from 1.67 to 1.70 at 193 nm to approx1.80 at 157 nm. The IBS process achieves the best homogeneity and the lowest surface roughness values (close to 1 nmrms) of the processes compared in the joint experiment. In contrast to MgF2 boat and e-beam evaporated coatings, which exhibit tensile mechanical stress ranging from 300 to 400 MPa, IBS coatings exhibit high compressive stress of as much as 910 MPa. A similar tendency was found for coating stress in LaF3 single layers. Experimental results are discussed with respect to the microstructural and compositional properties as well as to the surface topography of the coatings.
Controlling the excitation process of free electrons by a femtosecond elliptically polarized laser

NASA Astrophysics Data System (ADS)

Gao, Lili; Wang, Feng; Jiang, Lan; Qu, Liangti; Lu, Yongfeng

2015-11-01

This paper is focused on the excitation rates of free electrons of an aluminum (Al) bulk irradiated by an elliptically polarized laser in simulation, using time-dependent density functional theory (TDDFT). The polarized 400 nm, 10 fs laser pulse consisted of two elementary sinusoidal beams, and is adjusted by changing the phase difference φ and the intersection angle θ of the polarization directions between the two beams. The simulation includes cases of φ = π/2 with θ = 30°, θ = 45°, θ = 60°, θ = 90°, θ = 120°, θ = 135°, θ = 150°, and cases of θ = 90° with φ = π/4, φ = π/3, φ = π/2, φ = 2π/3, φ = 3π/4. The absorbed energy, the excitation rates and the density distributions of free electrons after laser termination are investigated. At the given power intensity (1×1014Wcm-2), pulse width (10 fs) and wavelength (400 nm) of each elementary laser beam, computational results indicate that the excitation rate of free electrons is impacted by three major factors: the long axis direction of the laser projected profile, the amplitude difference of the first main oscillation (1st AD), and the total amplitude difference of main oscillations (TAD) of the external electric field. Among the aforementioned three factors for the excitation rate of free electrons, the direction of long axis plays the most significant role. The screen effect is crucial to compare the importance of the remaining two factors. The analysis approach to investigate the electron dynamics under an elliptically polarized laser is both pioneering and effective.
Proximal fiber tip damage during Holmium:YAG and thulium fiber laser ablation of kidney stones

NASA Astrophysics Data System (ADS)

Wilson, Christopher R.; Hardy, Luke A.; Irby, Pierce B.; Fried, Nathaniel M.

2016-02-01

The Thulium fiber laser (TFL) is being studied as an alternative to Holmium:YAG laser for lithotripsy. TFL beam originates within an 18-μm-core thulium doped silica fiber, and its near single mode, Gaussian beam profile enables transmission of higher laser power through smaller fibers than possible during Holmium laser lithotripsy. This study examines whether TFL beam profile also reduces proximal fiber tip damage compared to Holmium laser multimodal beam. TFL beam at wavelength of 1908 nm was coupled into 105-μm-core silica fibers, with 35-mJ energy, 500-μs pulse duration, and pulse rates of 50-500 Hz. For each pulse rate, 500,000 pulses were delivered. Magnified images of proximal fiber surfaces were taken before and after each trial. For comparison, 20 single-use, 270-μm-core fibers were collected after clinical Holmium laser lithotripsy procedures using standard settings (600 mJ, 350 μs, 6 Hz). Total laser energy, number of laser pulses, and laser irradiation time were recorded, and fibers were rated for damage. For TFL studies, output power was stable, and no proximal fiber damage was observed after delivery of 500,000 pulses at settings up to 35 mJ, 500 Hz, and 17.5 W average power. In contrast, confocal microscopy images of fiber tips after Holmium lithotripsy showed proximal fiber tip degradation in all 20 fibers. The proximal fiber tip of a 105-μm-core fiber transmitted 17.5 W of TFL power without degradation, compared to degradation of 270-μm-core fibers after transmission of 3.6 W of Holmium laser power. The smaller and more uniform TFL beam profile may improve fiber lifetime, and potentially reduce costs for the surgical disposables as well.
Mixed garnet laser for a water vapour DIAL

NASA Astrophysics Data System (ADS)

Treichel, Rainer; Strohmaier, Stephan; Nikolov, Susanne; Eichler, Hans-Joachim; Murphy, Eamonn

2017-11-01

For the water vapour DIAL "WALES" the wavelength regions around 935 nm, 942 nm and 944 nm have been identified as the most suitable wavelength ranges. These wavelengths can be obtained using opticalparametric-oscillators (OPOs), stimulated Raman shifters and the Ti-Sapphire laser but none of these systems could deliver all the needed parameters like beam quality, efficiency, pulse length and energy yet. Also these systems are comparably big and heavy making them less suitable for a satellite based application. A fourth possibility to achieve these wavelength ranges is to shift the quasi-3-level laser lines (938 nm and 946 nm) of the Nd:YAG laser by replacing aluminium and yttrium by other rare earth elements. Changes of the host lattice characteristics lead to a shift of the upper and lower laser levels. These modified crystals are summarized under the name of "Mixed Garnet" crystals. Only the Mixed Garnet lasers can be pumped directly with diode laser and use a direct approach to generate the required laser pulses without frequency conversion. Therefore no additional non-linear crystals or special pump lasers are needed and a higher electric to optical efficiency is expected as well as single frequency operation using spectral tuning elements like etalons. In a first phase such mixed garnet crystals had been grown and characterised. The outcome was the selection of the gadolinium-scandium garnet for the most suitable laser crystal. During a second phase the complete laser system with output energy about 18 mJ in single 20 ns pulses and up to 8 mJ in free running mode with a combined pulse width of 250 μs at 942 nm have been demonstrated. The results of the first laser operation and the achieved performance parameter are reported.
Soft X-ray FEL simulation in PAL-XFEL

NASA Astrophysics Data System (ADS)

Shim, Chi Hyun; Ko, In Soo; Parc, Yong Woon; Han, Jang Hui

2015-10-01

The soft X-ray beamline in the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) will provide a photon beam with a wavelength from 1 nm to 3 nm in the self-amplified spontaneous emission (SASE) mode by using an electron beam with a 3.15-GeV beam energy. Linearly polarized radiation will be supplied by using six planar undulators (PUs). The linearly-polarized radiation powers at 1 (3) nm can reach 10.2 (30) GW. Polarization of the radiation will be controlled by applying the reverse undulator tapering scheme to the PUs and adding two helical undulators (HUs). The circularly-polarized radiation powers at 1 (3) nm will be 3.11 (11.73) GW. The degrees of circular polarization will be larger than 0.99 for both wavelengths. Three options for the future upgrade of the beamline to increase the radiation power are proposed.
Surface plasmon polaritons generated by radial polarized laser beam on silver nano-ring

NASA Astrophysics Data System (ADS)

Kozlova, Elena S.; Kotlyar, Victor V.

2017-04-01

In this work the single surface plasmon-polariton was obtained by using frequency-dependent finite difference time domain method for the radial polarized and vortex beams at 532 nm, which were propagating through the silver nanoring on substrate from silica glass, placed in an aqueous medium. The height and width of device were equal to 20 nm and 215 nm respectively. The intensity of surface plasmon-polariton was four times higher and three times higher the intensity of the incident radiation for case of conventional and vortex beams respectively. The full width at half maximum of the nanojet was near 160 nm for each cases. The presented design can be used for manufacturing of highly integrated optical devices and circuits used in high-speed communication applications. The results also can be used to design devices that allow capturing and moving the particles in water or other biofluidics.
Fabrication of hydrophobic structures on coronary stent surface based on direct three-beam laser interference lithography

NASA Astrophysics Data System (ADS)

Gao, Long-yue; Zhou, Wei-qi; Wang, Yuan-bo; Wang, Si-qi; Bai, Chong; Li, Shi-ming; Liu, Bin; Wang, Jun-nan; Cui, Cheng-kun; Li, Yong-liang

2016-05-01

To solve the problems with coronary stent implantation, coronary artery stent surface was directly modified by three-beam laser interference lithography through imitating the water-repellent surface of lotus leaf, and uniform micro-nano structures with the controllable period were fabricated. The morphological properties and contact angle (CA) of the microstructure were measured by scanning electron microscope (SEM) and CA system. The water repellency of stent was also evaluated by the contact and then separation between the water drop and the stent. The results show that the close-packed concave structure with the period of about 12 μm can be fabricated on the stent surface with special parameters (incident angle of 3°, laser energy density of 2.2 J·cm-2 and exposure time of 80 s) by using the three-beam laser at 1 064 nm, and the structure has good water repellency with CA of 120°.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Okamura, M., E-mail: okamura@bnl.gov; Nishina Center for Accelerator-Based Science, RIKEN, Saitama; Palm, K.

Calcium and lithium ion beams are required by NASA Space Radiation Laboratory at Brookhaven National Laboratory to simulate the effects of cosmic radiation. To identify the difficulties in providing such highly reactive materials as laser targets, both species were experimentally tested. Plate shaped lithium and calcium targets were fabricated to create ablation plasmas with a 6 ns 1064 nm neodymium-doped yttrium aluminum garnet laser. We found significant oxygen contamination in both the Ca and Li high charge state beams due to the rapid oxidation of the surfaces. A large spot size, low power density laser was used to create lowmore » charge state beams without scanning the targets. The low charge state Ca beam did not have any apparent oxygen contamination, showing the potential to clean the target entirely of oxide with a low power beam once in the chamber. The Li target was clearly still oxidizing in the chamber after each low power shot. To measure the rate of oxidation, we shot the low power laser at the target repeatedly at 10 s, 30 s, 60 s, and 120 s interval lengths, showing a linear relation between the interval time and the amount of oxygen in the beam.« less
5.5nm wavelength-tunable high-power MOPA diode laser system at 971 nm

NASA Astrophysics Data System (ADS)

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.
830-nm Polarization Controlled Lasing of InGaAs Quantum Wire Vertical-Cavity Surface-Emitting Lasers Grown on (775)B GaAs Substrates by Molecular Beam Epitaxy

NASA Astrophysics Data System (ADS)

Higuchi, Yu; Osaki, Shinji; Sasahata, Yoshifumi; Kitada, Takahiro; Shimomura, Satoshi; Ogura, Mutsuo; Hiyamizu, Satoshi

2007-02-01

We report the first demonstration of room temperature (RT) current injection lasing of vertical-cavity surface-emitting lasers (VCSELs), with self-organized InGaAs/(GaAs)6(AlAs)1 quantum wires (QWRs) in their active region, grown on (775)B-oriented GaAs substrates by molecular beam epitaxy. A (775)B InGaAs QWR-VCSEL with an aperture diameter of 4 μm lased at a wavelength of 829.7 nm and a threshold current of 0.7 mA at RT. The light output was linearly polarized in the direction parallel to the QWRs due to optical anisotropy of the self-organized (775)B InGaAs QWRs.
An instrument for 3D x-ray nano-imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holler, M.; Raabe, J.; Diaz, A.

We present an instrument dedicated to 3D scanning x-ray microscopy, allowing a sample to be precisely scanned through a beam while the angle of x-ray incidence can be changed. The position of the sample is controlled with respect to the beam-defining optics by laser interferometry. The instrument achieves a position stability better than 10 nm standard deviation. The instrument performance is assessed using scanning x-ray diffraction microscopy and we demonstrate a resolution of 18 nm in 2D imaging of a lithographic test pattern while the beam was defined by a pinhole of 3 {mu}m in diameter. In 3D on amore » test object of copper interconnects of a microprocessor, a resolution of 53 nm is achieved.« less

First demonstration of laser engagement of 1-Hz-injected flying pellets and neutron generation.

PubMed

Komeda, Osamu; Nishimura, Yasuhiko; Mori, Yoshitaka; Hanayama, Ryohei; Ishii, Katsuhiro; Nakayama, Suisei; Kitagawa, Yoneyoshi; Sekine, Takashi; Sato, Nakahiro; Kurita, Takashi; Kawashima, Toshiyuki; Kan, Hirofumi; Nakamura, Naoki; Kondo, Takuya; Fujine, Manabu; Azuma, Hirozumi; Motohiro, Tomoyoshi; Hioki, Tatsumi; Kakeno, Mitsutaka; Sunahara, Atsushi; Sentoku, Yasuhiko; Miura, Eisuke

2013-01-01

Pellet injection and repetitive laser illumination are key technologies for realizing inertial fusion energy. Numerous studies have been conducted on target suppliers, injectors, and tracking systems for flying pellet engagement. Here we for the first time demonstrate the pellet injection, counter laser beams' engagement and neutron generation. Deuterated polystyrene (CD) bead pellets, after free-falling for a distance of 18 cm at 1 Hz, are successfully engaged by two counter laser beams from a diode-pumped, ultra-intense laser HAMA. The laser energy, pulse duration, wavelength, and the intensity are 0.63 J per beam, 104 fs, and 811 nm, 4.7 × 10(18) W/cm(2), respectively. The irradiated pellets produce D(d,n)(3)He-reacted neutrons with a maximum yield of 9.5 × 10(4)/4π sr/shot. Moreover, the laser is found out to bore a straight channel with 10 μm-diameter through the 1-mm-diameter beads. The results indicate potentially useful technologies and findings for the next step in realizing inertial fusion energy.
First demonstration of laser engagement of 1-Hz-injected flying pellets and neutron generation

PubMed Central

Komeda, Osamu; Nishimura, Yasuhiko; Mori, Yoshitaka; Hanayama, Ryohei; Ishii, Katsuhiro; Nakayama, Suisei; Kitagawa, Yoneyoshi; Sekine, Takashi; Sato, Nakahiro; Kurita, Takashi; Kawashima, Toshiyuki; Kan, Hirofumi; Nakamura, Naoki; Kondo, Takuya; Fujine, Manabu; Azuma, Hirozumi; Motohiro, Tomoyoshi; Hioki, Tatsumi; Kakeno, Mitsutaka; Sunahara, Atsushi; Sentoku, Yasuhiko; Miura, Eisuke

2013-01-01

Pellet injection and repetitive laser illumination are key technologies for realizing inertial fusion energy. Numerous studies have been conducted on target suppliers, injectors, and tracking systems for flying pellet engagement. Here we for the first time demonstrate the pellet injection, counter laser beams' engagement and neutron generation. Deuterated polystyrene (CD) bead pellets, after free-falling for a distance of 18 cm at 1 Hz, are successfully engaged by two counter laser beams from a diode-pumped, ultra-intense laser HAMA. The laser energy, pulse duration, wavelength, and the intensity are 0.63 J per beam, 104 fs, and 811 nm, 4.7 × 1018 W/cm2, respectively. The irradiated pellets produce D(d,n)3He-reacted neutrons with a maximum yield of 9.5 × 104/4π sr/shot. Moreover, the laser is found out to bore a straight channel with 10 μm-diameter through the 1-mm-diameter beads. The results indicate potentially useful technologies and findings for the next step in realizing inertial fusion energy. PMID:24008696
Bismuth-doped fibre amplifier operating between 1600 and 1800 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Firstov, S V; Alyshev, S V; Riumkin, K E

2015-12-31

We report the first bismuth-doped fibre amplifier operating between 1600 and 1800 nm, which utilises bidirectional pumping (co-propagating and counter-propagating pump beams) by laser diodes at a wavelength of 1550 nm. The largest gain coefficient of the amplifier is 23 dB, at a wavelength of 1710 nm. It has a noise figure of 7 dB, 3-dB gain bandwidth of 40 nm and gain efficiency of 0.1 dB mW{sup -1}. (letters)
Multistable wireless micro-actuator based on antagonistic pre-shaped double beams

NASA Astrophysics Data System (ADS)

Liu, X.; Lamarque, F.; Doré, E.; Pouille, P.

2015-07-01

This paper presents a monolithic multistable micro-actuator based on antagonistic pre-shaped double beams. The designed micro-actuator is formed by two rows of bistable micro-actuators providing four stable positions. The bistable mechanism for each row is a pair of antagonistic pre-shaped beams. This bistable mechanism has an easier pre-load operation compared to the pre-compressed bistable beams method. Furthermore, it solves the asymmetrical force output problem of parallel pre-shaped bistable double beams. At the same time, the geometrical limit is lower than parallel pre-shaped bistable double beams, which ensures a smaller stroke of the micro-actuator with the same dimensions. The designed micro-actuator is fabricated using laser cutting machine on medium density fiberboard (MDF). The bistability and merits of antagonistic pre-shaped double beams are experimentally validated. Finally, a contactless actuation test is performed using 660 nm wavelength laser heating shape memory alloy (SMA) active elements.
Next generation high-brightness diode lasers offer new industrial applications

NASA Astrophysics Data System (ADS)

Timmermann, Andre; Meinschien, Jens; Bruns, Peter; Burke, Colin; Bartoschewski, Daniel

2008-02-01

So far, diode laser systems could not compete against CO II-lasers or DPSSL in industrial applications like marking or cutting due to their lower brightness. Recent developments in high-brightness diode laser bars and beam forming systems with micro-optics have led to new direct diode laser applications. LIMO presents 400W output from a 200μm core fibre with an NA of 0.22 at one wavelength. This is achieved via the combination of newly designed laser diode bars on passive heat sinks coupled with optimized micro-optical beam shaping. The laser is water cooled with a housing size of 375mm x 265mm x 70mm. The applications for such diode laser modules are mainly in direct marking, cutting and welding of metals and other materials, but improved pumping of fibre lasers and amplifiers is also possible. The small spot size leads to extremely high intensities and therefore high welding speeds in cw operation. For comparison: The M2 of the fibre output is 70, which gives a comparable beam parameter product (22mm*mrad) to that of a CO II laser with a M2 of 7 because of the wavelength difference. Many metals have a good absorption within the wavelength range of the laser diodes (NIR, 808nm to 980nm), which permits the cutting of thin sheets of aluminium or steel with a 200W version of this laser. First welding tests show reduced splatters and pores owing to the optimized process behaviour in cw operation with short wavelengths. The availability of a top-hat profile proves itself to be advantageous compared to the traditional Gaussian beam profiles of fibre, solid-state and gas lasers in that the laser energy is evenly distributed over the working area. For the future, we can announce an increase of the output power up to 1200W out of a 200μm fibre (0.22 NA). This will be achieved by further sophistication and optimisation of the coupling technique and the coupling of three wavelengths. The beam parameter product will then remain at 22mm*mrad with a power density of 3.8 MW/cm2 if focussed to a 200Âµm spot. This leads to excellent laser cutting results with extremely small cutting kerfs down to 200μm and very plane cutting edges. Process speeds rise up to more than 10m/min i.e. for thin sheets of stainless steel or titanium.
Injection locking of violet laser diodes with a 3.2 GHz offset frequency for driving Raman transitions in 43Ca+.

PubMed

Keitch, B C; Thomas, N R; Lucas, D M

2013-03-15

Two cw single-mode violet (397 nm) diode lasers are locked to a single external-cavity master diode laser by optical injection locking. A double-pass 1.6 GHz acousto-optic modulator is used to provide a 3.2 GHz offset frequency between the two slave lasers. We achieve up to 20 mW usable output in each slave beam, with as little as 25 μW of injection power at room temperature. An optical heterodyne measurement of the beat note between the two slave beams gives a linewidth of ≤10 Hz at 3.2 GHz. We also estimate the free-running linewidth of the master laser to be approximately 3 MHz by optical heterodyning with a similar device.
Single-mode, All-Solid-State Nd:YAG Laser Pumped UV Converter

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Armstrong, Darrell, J.; Edwards, William C.; Singh, Upendra N.

2008-01-01

In this paper, the status of a high-energy, all solid-state Nd:YAG laser pumped nonlinear optics based UV converter development is discussed. The high-energy UV transmitter technology is being developed for ozone sensing applications from space based platforms using differential lidar technique. The goal is to generate greater than 200 mJ/pulse with 10-50 Hz PRF at wavelengths of 308 nm and 320 nm. A diode-pumped, all-solid-state and single longitudinal mode Nd:YAG laser designed to provide conductively cooled operation at 1064 nm has been built and tested. Currently, this pump laser provides an output pulse energy of >1 J/pulse at 50 Hz PRF and a pulsewidth of 22 ns with an electrical-to-optical system efficiency of greater than 7% and a M(sup 2) value of <2. The single frequency UV converter arrangement basically consists of an IR Optical Parametric Oscillator (OPO) and a Sum Frequency Generator (SFG) setups that are pumped by 532 nm wavelength obtained via Second Harmonic Generation (SHG). In this paper, the operation of an inter cavity SFG with CW laser seeding scheme generating 320 nm wavelength is presented. Efforts are underway to improve conversion efficiency of this mJ class UV converter by modifying the spatial beam profile of the pump laser.
The Slope Imaging Multi-Polarization Photon-Counting Lidar: Development and Performance Results

NASA Technical Reports Server (NTRS)

Dabney, Phillip

2010-01-01

The Slope Imaging Multi-polarization Photon-counting Lidar is an airborne instrument developed to demonstrate laser altimetry measurement methods that will enable more efficient observations of topography and surface properties from space. The instrument was developed through the NASA Earth Science Technology Office Instrument Incubator Program with a focus on cryosphere remote sensing. The SIMPL transmitter is an 11 KHz, 1064 nm, plane-polarized micropulse laser transmitter that is frequency doubled to 532 nm and split into four push-broom beams. The receiver employs single-photon, polarimetric ranging at 532 and 1064 nm using Single Photon Counting Modules in order to achieve simultaneous sampling of surface elevation, slope, roughness and depolarizing scattering properties, the latter used to differentiate surface types. Data acquired over ice-covered Lake Erie in February, 2009 are documenting SIMPL s measurement performance and capabilities, demonstrating differentiation of open water and several ice cover types. ICESat-2 will employ several of the technologies advanced by SIMPL, including micropulse, single photon ranging in a multi-beam, push-broom configuration operating at 532 nm.
Cell viability test after laser guidance

NASA Astrophysics Data System (ADS)

Rosenbalm, Tabitha N.; Owens, Sarah; Bakken, Daniel; Gao, Bruce Z.

2006-02-01

To precisely control the position of multiple types of cells in a coculture for the study of cell-cell interactions, we have developed a laser micropatterning technique. The technique employs the optical forces generated by a weakly focused laser beam. In the beam's focal region, the optical force draws microparticles, such as cells, into the center of the beam, propels them along the beam axis, and guides them onto a target surface. Specific patterns are created through computercontrolled micromanipulation of the substrate relative to the laser beam. Preliminary data have demonstrated cell viability after laser guidance. This project was designed to systematically vary the controllable laser parameters, namely, intensity and exposure time of the laser on single cells, and thus determine the laser parameters that allow negligible cell damage with functional cellular position control. To accomplish this goal, embryonic day 7 (E7) chick forebrain neurons were cultured in 35 mm petri dishes. Control and test cells were selected one hour after cell placement to allow cell attachment. Test cells were subjected to the laser at the focal region. The experimental parameters were chosen as: wavelength - 800 nm, intensities - 100 mW, 200 mW, and 300 mW, and exposure times - 10 s and 60 s. Results were analyzed based on neurite outgrowth and the Live/Dead assay (Viability/Cytoxicity kit from Molecular Probes). No statistical difference (p >> 0.1, student t-test) in viability or function was found between the control neurons and those exposed to the laser. This confirms that laser guidance seems to be a promising method for cellular manipulation.
Variable-focus side-firing endoscopic device

NASA Astrophysics Data System (ADS)

Lemberg, Vladimir G.; Black, Michael

1996-05-01

Conventional side-firing fiber technology exhibits performance limitations and utilizes expensive single-use only devices which often require multiple fibers for laser prostatectomy. Another limitation of existing side-firing fiber technology is its inability to focus the beam to create incisions for urologic applications such as laser TURP (transurethral resectional prostatectomy), tumor necrosis, lithotripsy, genital warts, and photodynamic therapy. Newly introduced variable-focus side-firing endoscopic device utilizes either one or two lenses and a mirror, onto a single cylinder of molded glass. The laser beam exits the optical fiber, passes through the lens, strikes the cylindrical mirror, and traverses the cylindrical surface. Depending on the design, the laser beam is reflected at the angles ranging from 30 degrees to 120 degrees out of the cylindrical lens. A second lens can be formed onto the side of the cylindrical surface at the beam's exit point. Another advantage of the innovative side-firing device is its capability to provide versatile matching to multiple laser wavelengths from 360 nm to 2.5 microns, and achieve power densities great enough to perform vaporization, incision and coagulation of tissue. Precise focusing of the laser beam results in reduced tissue necrosis of surrounding the treatment area as well as in decreased laser radiation back-scattering. Surgeons can very the focus by adjusting the distance from the tip to the target area. The variable focus side-firing device provides a focused beam at the range of 1.0 to 1.5 mm, for incision. Outside this range, it produces a defocused beam for coagulation.
Second harmonic generation and photochromic grating in polyurethane films containing diazo isoxazole chromophore

NASA Astrophysics Data System (ADS)

Marański, Krzysztof; Kucharski, Stanisław; Ortyl, Ewelina; Nunzi, Jean-Michel; Ahmadi-Kandjani, Sohrab; Dabos-Seignon, Sylvie; Chan, Siu-Wai; Barille, Regis

2008-08-01

The chromophoric intermediate: 2,2'-({4-[( E)-(5-methylisoxazol-3-yl)diazenyl]phenyl}-imino)diethanol was used in polyaddition reaction with di-isocyanate to obtain a new polyurethane polymeric material showing nonlinear optical and photochromic properties. The maximum absorption band of the polymer film was at 418 nm. The illumination of the film with crossed beams of the 488 nm Ar + laser yielded surface relief grating of regular structure. Measurement of the frequency doubling signal with 1064 nm laser indicated the polymer as interesting material for photooptical applications. The measured nonlinear optical coefficient, d33, reached 90.2 pm/V.
Bragg gratings inscription in step-index PMMA optical fiber by femtosecond laser pulses at 400 nm

NASA Astrophysics Data System (ADS)

Hu, X.; Kinet, D.; Chah, K.; Mégret, P.; Caucheteur, C.

2016-05-01

In this paper, we report photo-inscription of uniform Bragg gratings in trans-4-stilbenemethanol-doped photosensitive step-index polymer optical fiber. Gratings were produced at ~1575 nm by the phase mask technique with a femtosecond laser emitting at 400 nm with different average optical powers (8 mW, 13 mW and 20 mW). The grating growth dynamics in transmission were monitored during the manufacturing process, showing that the grating grows faster with higher power. Using 20 mW laser beam power, the reflectivity reaches 94 % (8 dB transmission loss) in 70 seconds. Finally, the gratings were characterized in temperature in the range 20 - 45 °C. The thermal sensitivity has been computed equal to - 86.6 pm/°C.
7.5 W blue light generation at 452 nm by internal frequency doubling of a continuous-wave Nd-doped fiber laser.

PubMed

Leconte, Baptiste; Gilles, Hervé; Robin, Thierry; Cadier, Benoit; Laroche, Mathieu

2018-04-16

We present the first frequency-doubled neodymium-doped fiber laser generating multi-watt CW power near 450 nm. A bow-tie resonator incorporating a LBO nonlinear crystal is integrated within a Nd-doped fiber laser emitting near 900 nm. This scheme achieves an IR to blue conversion efficiency close to 55% without any active control of the internal resonant cavity. As a result, up to 7.5 W of linearly-polarized blue power is generated, with beam quality factors M x 2 ~1.0 and M y 2 ~1.5. A simple numerical model has been developed to optimize and analyse the IR to blue conversion efficiency in the resonant cavity. Performance limitations and prospects for further improvements are discussed.
Solid-state laser source of narrowband ultraviolet B light for skin disease care

NASA Astrophysics Data System (ADS)

Tarasov, Aleksandr A.; Chu, Hong

2013-03-01

We report about the development of all-solid-state laser source of narrowband UV-B light for medical applications. The device is based on a gain-switched Ti: Sapphire laser with volume Bragg grating, pumped at 532 nm and operating at 931.8 nm, followed by a third harmonic generator and a fiber optic beam homogenizer. The maximum available pulse energy exceeded 5 mJ at 310.6 nm, with a pulse repetition rates of 50 Hz. The output characteristics satisfy the medical requirements for psoriasis and vitiligo treatment. A new optical scheme for third harmonic generation enhancement at moderate levels of input intensities is proposed and investigated. As a result, 40% harmonic efficiency was obtained, when input pulse power was only 300 kW.
Four different diode lasers comparison on soft tissues surgery: a preliminary ex vivo study.

PubMed

Fornaini, Carlo; Merigo, Elisabetta; Sozzi, Michele; Rocca, Jean-Paul; Poli, Federica; Selleri, Stefano; Cucinotta, Annamaria

2016-06-29

Objectives: The introduction of diode lasers in dentistry had several advantages, principally consisting on the reduced size, reduced cost and possibility to beam delivering by optical fibbers. Up today only the wavelengths around 810 and 980 nm were the most utilized in oral surgery but recently more different lasers had been proposed. The aim of this study was to compare the efficacy of four diode laser wavelengths (810, 980, 1470 and 1950 nm) for the ablation of soft tissues. Material and methods: Specimens were surgically collected from the dorsal surface of four bovine tongues and irradiated by four different diode wavelengths. Thermal increase was measured by two thermocouples, the first at a depth of 0.5 mm, and the second at a depth of 2 mm. Initial and final surface temperatures were recorded by IR thermometer. Epithelial changes, connective tissue modifications, presence of vascular modification and incision morphology were histologically evaluated by two blind pathologists. Results: The time necessary to perform the excision varied between 271 seconds (808 nm, 2W) and 112 seconds (1950 nm, 4W). Temperature increase superficial level varied from 16.3° (980 nm, 4W) and 9.2° (1950 nm, 2 W). The most significant deep temperature increase was recorded by 980 nm, 4 W (17.3°) and the lowest by 1950 nm, 2 W (9.7°). The width of epithelial tissue injuries varied between 74 pm from 1950 nm diode laser at 2 W to 540 pm for 1470 nm diode laser at 4 W. Conclusion: The quality of incision was better and the width of overall tissue injuries was minor in the specimens obtained with higher wavelength (1950 nm) at lower power (2W).
Four different diode lasers comparison on soft tissues surgery: a preliminary ex vivo study

PubMed Central

Merigo, Elisabetta; Sozzi, Michele; Rocca, Jean-Paul; Poli, Federica; Selleri, Stefano; Cucinotta, Annamaria

2016-01-01

Objectives: The introduction of diode lasers in dentistry had several advantages, principally consisting on the reduced size, reduced cost and possibility to beam delivering by optical fibbers. Up today only the wavelengths around 810 and 980 nm were the most utilized in oral surgery but recently more different lasers had been proposed. The aim of this study was to compare the efficacy of four diode laser wavelengths (810, 980, 1470 and 1950 nm) for the ablation of soft tissues. Material and methods: Specimens were surgically collected from the dorsal surface of four bovine tongues and irradiated by four different diode wavelengths. Thermal increase was measured by two thermocouples, the first at a depth of 0.5 mm, and the second at a depth of 2 mm. Initial and final surface temperatures were recorded by IR thermometer. Epithelial changes, connective tissue modifications, presence of vascular modification and incision morphology were histologically evaluated by two blind pathologists. Results: The time necessary to perform the excision varied between 271 seconds (808 nm, 2W) and 112 seconds (1950 nm, 4W). Temperature increase superficial level varied from 16.3° (980 nm, 4W) and 9.2° (1950 nm, 2 W). The most significant deep temperature increase was recorded by 980 nm, 4 W (17.3°) and the lowest by 1950 nm, 2 W (9.7°). The width of epithelial tissue injuries varied between 74 pm from 1950 nm diode laser at 2 W to 540 pm for 1470 nm diode laser at 4 W. Conclusion: The quality of incision was better and the width of overall tissue injuries was minor in the specimens obtained with higher wavelength (1950 nm) at lower power (2W). PMID:27721562
Sub-10-nm suspended nano-web formation by direct laser writing

NASA Astrophysics Data System (ADS)

Wang, Sihao; Yu, Ye; Liu, Hailong; Lim, Kevin T. P.; Madurai Srinivasan, Bharathi; Zhang, Yong Wei; Yang, Joel K. W.

2018-06-01

A diffraction-limited three-dimensional (3D) direct laser writing (DLW) system based on two-photon polymerization can routinely pattern structures at the 100 nm length scale. Several schemes have been developed to improve the patterning resolution of 3D DLW but often require customized resist formulations or multi-wavelength exposures. Here, we introduce a scheme to produce suspended nano-webs with feature sizes below 10 nm in IP-Dip resist using sub-threshold exposure conditions in a commercial DLW system. The narrowest suspended lines (nano-webs) measured 7 nm in width. Larger ∼20 nm nano-webs were patterned with ∼80% yield at increased laser powers. In addition, closely spaced nano-gaps with a center-to-center distance of 33 nm were produced by patterning vertically displaced suspended lines followed by metal deposition and liftoff. We provide hypotheses and present preliminary results for a mechanism involving the initiation of a percolative path and a strain-induced narrowing in the nano-web formation. Our approach allows selective features to be patterned with dimensions comparable to the sub-10 nm patterning capability of electron-beam lithography (EBL).
Microchip Yb:CaLnAlO4 lasers with up to 91% slope efficiency.

PubMed

Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Xu, Xiaodong; Xu, Jun; Jambunathan, Venkatesan; Navratil, Petr; Lucianetti, Antonio; Mocek, Tomas; Zhang, Xuzhao; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc; Major, Arkady

2017-07-01

Multi-watt continuous-wave (CW) operation of tetragonal rare-earth calcium aluminate Yb:CaLnAlO 4 (Ln=Gd,Y)) crystals in plano-plano microchip lasers was demonstrated with an almost quantum-defect-limited slope efficiency. Pumped at 978 nm by an InGaAs laser diode, a 3.4 mm long 8 at. % Yb:CaGdAlO 4 laser generated 7.79 W at 1057-1065 nm with a slope efficiency of η=84% (with respect to the absorbed pump power). An even higher η=91% was achieved with a 2.5 mm long 3 at. % Yb:CaYAlO 4 laser, from which 5.06 W were extracted at 1048-1056 nm. Both lasers produced linearly polarized output (σ-polarization) with an almost circular diffraction-limited beam (Mx,y2<1.1). The output performance of the developed lasers was modeled, yielding an internal loss coefficient as low as 0.004-0.007 cm -1 . In addition, their spectroscopic properties were revisited.
High precision AlGaAsSb ridge-waveguide etching by in situ reflectance monitored ICP-RIE

NASA Astrophysics Data System (ADS)

Tran, N. T.; Breivik, Magnus; Patra, S. K.; Fimland, Bjørn-Ove

2014-05-01

GaSb-based semiconductor diode lasers are promising candidates for light sources working in the mid-infrared wavelength region of 2-5 μm. Using edge emitting lasers with ridge-waveguide structure, light emission with good beam quality can be achieved. Fabrication of the ridge waveguide requires precise etch stop control for optimal laser performance. Simulation results are presented that show the effect of increased confinement in the waveguide when the etch depth is well-defined. In situ reflectance monitoring with a 675 nm-wavelength laser was used to determine the etch stop with high accuracy. Based on the simulations of laser reflectance from a proposed sample, the etching process can be controlled to provide an endpoint depth precision within +/- 10 nm.
Early remote laser detection of vegetation damage caused by certain environmental stress factors

NASA Technical Reports Server (NTRS)

Chappelle, Emmett W.; Mcmurtrey, James E., III

1989-01-01

The fluorescence spectra of plants excited with a pulsed nitrogen laser beam emitting at 337 nm were found to be related to plant type, as well as with changes in the physiology of the plant as the result of various kinds of environmental stress. The plant types which were studied included herbaceous dicots, monocots, hardwoods, and conifers. These plant types could be identified on the basis of differences in either the number of fluorescent bands, or the relative intensity of the bands. The dicots and monocots had fluorescent maxima at 440, 685, and 740 nm. The monocots could be distinguished from the dicots by virtue of having a much higher 440 nm/685 nm ratio. Hardwoods and conifers had an additional fluorescence band at 525 nm, but healthy conifers did not have a band at 685 nm.

Note: Non-invasive optical method for rapid determination of alignment degree of oriented nanofibrous layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pokorny, M.; Rebicek, J.; Klemes, J.

2015-10-15

This paper presents a rapid non-destructive method that provides information on the anisotropic internal structure of nanofibrous layers. A laser beam of a wavelength of 632.8 nm is directed at and passes through a nanofibrous layer prepared by electrostatic spinning. Information about the structural arrangement of nanofibers in the layer is directly visible in the form of a diffraction image formed on a projection screen or obtained from measured intensities of the laser beam passing through the sample which are determined by the dependency of the angle of the main direction of polarization of the laser beam on the axismore » of alignment of nanofibers in the sample. Both optical methods were verified on Polyvinyl alcohol (PVA) nanofibrous layers (fiber diameter of 470 nm) with random, single-axis aligned and crossed structures. The obtained results match the results of commonly used methods which apply the analysis of electron microscope images. The presented simple method not only allows samples to be analysed much more rapidly and without damaging them but it also makes possible the analysis of much larger areas, up to several square millimetres, at the same time.« less
The Conductive Silver Nanowires Fabricated by Two-beam Laser Direct Writing on the Flexible Sheet.

PubMed

He, Gui-Cang; Zheng, Mei-Ling; Dong, Xian-Zi; Jin, Feng; Liu, Jie; Duan, Xuan-Ming; Zhao, Zhen-Sheng

2017-02-02

Flexible electrically conductive nanowires are now a key component in the fields of flexible devices. The achievement of metal nanowire with good flexibility, conductivity, compact and smooth morphology is recognized as one critical milestone for the flexible devices. In this study, a two-beam laser direct writing system is designed to fabricate AgNW on PET sheet. The minimum width of the AgNW fabricated by this method is 187 ± 34 nm with the height of 84 ± 4 nm. We have investigated the electrical resistance under different voltages and the applicable voltage per meter range is determined to be less than 7.5 × 10 3 V/m for the fabricated AgNW. The flexibility of the AgNW is very excellent, since the resistance only increases 6.63% even after the stretched bending of 2000 times at such a small bending radius of 1.0 mm. The proposed two-beam laser direct writing is an efficient method to fabricate AgNW on the flexible sheet, which could be applied in flexible micro/nano devices.
A study of H+ production using metal hydride and other compounds by means of laser ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sekine M.; Kondo K.; Okamura, M.

2012-02-22

A laser ion source can provide wide variety of ion beams from solid target materials, however, it has been difficult to create proton beam efficiently. We examined capability of proton production using beeswax, polyethylene, and metal hydrides (MgH2 and ZrH2) as target materials. The results showed that beeswax and polyethylene could not be used to produce protons because these targets are transparent to the laser wavelength of 1064 nm. On the other hand, the metal hydrides could supply protons. Although the obtained particle numbers of protons were less than those of the metal ions, the metal hydrides could be usedmore » as a target for proton laser ion source.« less
Laser induced fluorescence spectroscopy used for the investigation of Landé gJ- factors of praseodymium energy levels

NASA Astrophysics Data System (ADS)

Sobolewski, Ł. M.; Windholz, L.; Kwela, J.

2017-06-01

Laser induced fluorescence (LIF) spectroscopy was used for the investigation of structures of 52 spectral lines of Pr I in the wavelength range 561.3 - 613.9 nm. As a source of free Pr atoms a hollow cathode discharge lamp was used. We monitored selected LIF signals appearing when the laser beam excites the hollow cathode plasma. LIF spectra were recorded in the presence of a magnetic field of about 800 G produced by a permanent magnet for two linear polarizations of the exciting laser beam. We have determined for the first time Landé gJ- factors for 71 levels of neutral Pr and reinvestigated data for several other levels.
High on/off ratio nanosecond laser pulses for a triggered single-photon source

NASA Astrophysics Data System (ADS)

Jin, Gang; Liu, Bei; He, Jun; Wang, Junmin

2016-07-01

An 852 nm nanosecond laser pulse chain with a high on/off ratio is generated by chopping a continuous-wave laser beam using a Mach-Zehnder-type electro-optic intensity modulator (MZ-EOIM). The detailed dependence of the MZ-EOIM’s on/off ratio on various parameters is characterized. By optimizing the incident beam polarization and stabilizing the MZ-EOIM temperature, a static on/off ratio of 12600:1 is achieved. The dynamic on/off ratios versus the pulse repetition rate and the pulse duty cycle are measured and discussed. The high-on/off-ratio nanosecond pulsed laser system was used in a triggered single-photon source based on a trapped single cesium atom, which reveals clear antibunching.
Ultrabroadband beam splitter with matched group-delay dispersion.

PubMed

Kim, J; Birge, Jonathan R; Sharma, V; Fujimoto, J G; Kärtner, E X; Scheuer, V; Angelow, G

2005-06-15

We present a general design strategy for a broadband thin-film beam splitter with matched group-delay dispersion. By taking the substrate dispersion into account in the coating design, any combination of input and output can show the same dispersion for transmission and reflection. As a specific implementation, an ultrabroadband 50:50 beam splitter from 600 to 1500 nm for femtosecond laser applications was designed, fabricated, and characterized.
Laser modulator for LISA pathfinder

NASA Astrophysics Data System (ADS)

Voland, C.; Lund, G.; Coppoolse, W.; Crosby, P.; Stadler, M.; Kudielka, K.; Özkan, C.

2017-11-01

LISA Pathfinder is an ESA experiment to demonstrate the key technologies needed for the LISA mission to detect gravitational waves in space. The LISA Pathfinder spacecraft represents one arm of the LISA interferometer, containing an optical metrology system and two proof masses as inertial references for the drag-free control system. The LISA Pathfinder payload consists of two drag-free floating test masses located in the inertial sensors with their control electronics and an optical metrology subsystem. The optical metrology subsystem monitors the movement of both test masses relative to each other and to the spacecraft with very high sensitivity and resolution. This is achieved with a heterodyne Mach- Zehnder interferometer. This interferometer requires as input two coherent laser beams with a heterodyne frequency difference of a few kHz. To generate the two laser beams with a heterodyne frequency difference a Nd:YAG laser is used together with the Laser Modulator. The Nd:YAG laser generates a single coherent laser signal at a wavelength of 1064nm which is fibre coupled to the Laser Modulator. The Laser Modulator then generates the two optical beams with the required heterodyne frequency offset. In addition, the Laser Modulator is required to perform laser amplitude stabilization and optical path difference control for the two optical signals. The Laser Modulator consists of an optical unit - the LMU - and RF synthesiser, power amplification and control electronics. These electronics are all housed in the Laser Modulator Electronics (LME). The LMU has four primary functions: • Splitting of the input laser beam into two paths for later superposition in the interferometer. • Applying different frequency shifts to each of the beams. • Providing amplitude modulation control to each of the beams. • Providing active control of the optical path length difference between the two optical paths. The present paper describes the design and performance of the LMU together with a summary of the results of the Laser Modulator engineering model test campaign.
Coherent beam combining architectures for high power tapered laser arrays

NASA Astrophysics Data System (ADS)

Schimmel, G.; Janicot, S.; Hanna, M.; Decker, J.; Crump, P.; Erbert, G.; Witte, U.; Traub, M.; Georges, P.; Lucas-Leclin, G.

2017-02-01

Coherent beam combining (CBC) aims at increasing the spatial brightness of lasers. It consists in maintaining a constant phase relationship between different emitters, in order to combine them constructively in one single beam. We have investigated the CBC of an array of five individually-addressable high-power tapered laser diodes at λ = 976 nm, in two architectures: the first one utilizes the self-organization of the lasers in an interferometric extended-cavity, which ensures their mutual coherence; the second one relies on the injection of the emitters by a single-frequency laser diode. In both cases, the coherent combining of the phase-locked beams is ensured on the front side of the array by a transmission diffractive grating with 98% efficiency. The passive phase-locking of the laser bar is obtained up to 5 A (per emitter). An optimization algorithm is implemented to find the proper currents in the five ridge sections that ensured the maximum combined power on the front side. Under these conditions we achieve a maximum combined power of 7.5 W. In the active MOPA configuration, we can increase the currents in the tapered sections up to 6 A and get a combined power of 11.5 W, corresponding to a combining efficiency of 76%. It is limited by the beam quality of the tapered emitters and by fast phase fluctuations between emitters. Still, these results confirm the potential of CBC approaches with tapered lasers to provide a high-power and high-brightness beam, and compare with the current state-of-the-art with laser diodes.
Applications of OALCLV in the high power laser systems

NASA Astrophysics Data System (ADS)

Huang, Dajie; Fan, Wei; Cheng, He; Wei, Hui; Wang, Jiangfeng; An, Honghai; Wang, Chao; Cheng, Yu; Xia, Gang; Li, Xuechun; Lin, Zunqi

2017-10-01

This paper introduces the recent development of our integrated optical addressed spatial light modulator and its applications in the high power laser systems. It can be used to convert the incident beam into uniform beam for high energy effiency, or it can realize special distribution to meet the requirements of physical experiment. The optical addressing method can avoid the problem of the black matrix effect of the electric addressing device. Its transmittance for 1053nm light is about 85% and the aperture of our device has reached 22mm× 22mm. As a transmissive device, it can be inserted into the system without affecting the original optical path. The applications of the device in the three laser systems are introduced in detail in this paper. In the SGII-Up laser facility, this device demonstrates its ability to shape the output laser beam of the fundamental frequency when the output energy reaches about 2000J. Meanwhile, there's no change in the time waveform and far field distribution. This means that it can effectively improve the capacity of the maximum output energy. In the 1J1Hz Nd-glass laser system, this device has been used to improve the uniformity of the output beam. As a result, the PV value reduces from 1.4 to 1.2, which means the beam quality has been improved effectively. In the 9th beam of SGII laser facility, the device has been used to meet the requirements of sampling the probe light. As the transmittance distribution of the laser beam can be adjusted, the sampling spot can be realized in real time. As a result, it's easy to make the sampled spot meet the requirements of physics experiment.
The Laser MicroJet (LMJ): a multi-solution technology for high quality micro-machining

NASA Astrophysics Data System (ADS)

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.
Fiber-Based 589 nm Laser for Sodium Guide Star

DTIC Science & Technology

2006-02-01

are combined in a 980/1060 nm WDM coupler and free-space launched through an isolator designed for 1060 nm into a 23 m long Yb doped fiber. This fiber...lenses. The final-stage amplifier comprised a 23 m long YDF with a core diameter of 8 lam and a D-shaped inner cladding of 400 jtm diameter. It was...resolution). (b) High resolution spectrum of the 1178 nm output beam at 534 m W output power, linewidth (FWHM) - 0. 6 nm (0.05 nm resolution). The
High power, widely tunable dual-wavelength 2 μm laser based on intracavity KTP optical parametric oscillator

NASA Astrophysics Data System (ADS)

Yan, Dexian; Wang, Yuye; Xu, Degang; Shi, Wei; Zhong, Kai; Liu, Pengxiang; Yan, Chao; Mei, Jialin; Shi, Jia; Yao, Jianquan

2017-01-01

We presented a high power, widely tunable narrowband 2 μm dual-wavelength source employing intracavity optical parametric oscillator with potassium titanium oxide phosphate (KTP) crystal. Two identical KTP crystals were oriented oppositely in the OPO cavity to compensate the walk-off effect. The output average power of dual-wavelength 2 μm laser was up to 18.18 W at 10 kHz with the peak power of 165 kW. The two wavelengths can be tuned in the range of 2070.7 nm to 2191.1 nm for ordinary light while in the range of 2190.7 nm to 2065.9 nm for extraordinary light with the full width at half maximum (FWHM) about 0.8 nm. The pulse width of the tunable laser was as narrow as 11 ns. The beam quality factor M 2 was less than 4 during wavelength tuning.
Laser characterization of the depth profile of complex refractive index of PMMA implanted with 50 keV silicon ions

NASA Astrophysics Data System (ADS)

Stefanov, Ivan L.; Stoyanov, Hristiyan Y.; Petrova, Elitza; Russev, Stoyan C.; Tsutsumanova, Gichka G.; Hadjichristov, Georgi B.

2013-03-01

The depth profile of the complex refractive index of silicon ion (Si+) implanted polymethylmethacrylate (PMMA) is studied, in particular PMMA implanted with Si+ ions accelerated to a relatively low energy of 50 keV and at a fluence of 3.2 × 1015 cm-2. The ion-modified material with nano-clustered structure formed in the near(sub)surface layer of a thickness of about 100 nm is optically characterized by simulation based on reflection ellipsometry measurements at a wavelength of 632.8 nm (He-Ne laser). Being of importance for applications of ion-implanted PMMA in integrated optics, optoelectronics and optical communications, the effect of the index depth profile of Si+-implanted PMMA on the profile of the reflected laser beam due to laser-induced thermo-lensing in reflection is also analyzed upon illumination with a low power cw laser (wavelength 532 nm, optical power 10 - 50 mW).
Full color laser projection display using Kr-Ar laser (white laser) beam-scanning technology

NASA Astrophysics Data System (ADS)

Kim, Yonghoon; Lee, Hang W.; Cha, Seungnam; Lee, Jin-Ho; Park, Youngjun; Park, Jungho; Hong, Sung S.; Hwang, Young M.

1997-07-01

Full color laser projection display is realized on the large screen using a krypton-argon laser (white laser) as a light source, and acousto-optic devices as light modulators. The main wavelengths of red, green and blue color are 647, 515, and 488 nm separated by dichroic mirrors which are designed to obtain the best performance for the s-polarized beam with the 45 degree incident angle. The separated beams are modulated by three acousto-optic modulators driven by rf drivers which has energy level of 1 watt at 144 MHz and recombined by dichroic mirrors again. Acousto-optic modulators (AOM) are fabricated to satisfy high diffraction efficiency over 80% and fast rising time less than 50 ns at the video bandwidth of 5 MHz. The recombined three beams (RGB) are scanned by polygonal mirrors for horizontal lines and a galvanometer for vertical lines. The photodiode detection for monitoring of rotary polygonal mirrors is adopted in this system for the compensation of the tolerance in the mechanical scanning to prevent the image joggling in the horizontal direction. The laser projection display system described in this paper is expected to apply HDTV from the exploitation of the acousto- optic modulator with the video bandwidth of 30 MHz.
Self-mode-locked AlGaInP-VECSEL

NASA Astrophysics Data System (ADS)

Bek, R.; Großmann, M.; Kahle, H.; Koch, M.; Rahimi-Iman, A.; Jetter, M.; Michler, P.

2017-10-01

We report the mode-locked operation of an AlGaInP-based semiconductor disk laser without a saturable absorber. The active region containing 20 GaInP quantum wells is used in a linear cavity with a curved outcoupling mirror. The gain chip is optically pumped by a 532 nm laser, and mode-locking is achieved by carefully adjusting the pump spot size. For a pump power of 6.8 W, an average output power of up to 30 mW is reached at a laser wavelength of 666 nm. The pulsed emission is characterized using a fast oscilloscope and a spectrum analyzer, demonstrating stable single-pulse operation at a repetition rate of 3.5 GHz. Intensity autocorrelation measurements reveal a FWHM pulse duration of 22 ps with an additional coherence peak on top, indicating noise-like pulses. The frequency spectrum, as well as the Gaussian beam profile and the measured beam propagation factor below 1.1, shows no influence of higher order transverse modes contributing to the mode-locked operation.
Design of 6 kw fiber-coupled system for semiconductor laser

NASA Astrophysics Data System (ADS)

Wu, Yulong; Dong, Zhiyong; Chen, Yongqi; Qi, Yunfei; Ding, Lushuang; Zhao, Pengfei; Zou, Yonggang; Xu, Li; Lin, Xuechun

2016-10-01

In this paper, we present the design of a 6 kW fiber-coupled laser diode system by using ZEMAX, and power scaling and fiber coupling techniques for high-power laser diode stacks were introduced in detail. Beams emitted from eight laser diode stacks comprised of four 960 W stacks with center wavelength of 938 nm and four 960 W stacks with center wavelength of 976 nm are combined and coupled into a standard fiber with a core diameter of 800 μm and numerical aperture of 0.22. Simulative result shows that the final power came out of the fiber could reach 6283.9 W, the fiber-coupling efficiency is 87%, and the brightness is 8.2 MW/ (cm2·sr).
Investigation of 100 mJ all solid state end-pumped 1064 nm Q-switched laser

NASA Astrophysics Data System (ADS)

Xie, Shiyong; Wang, Caili; Liu, Hui; Bo, Yong; Xu, Zuyan

2017-11-01

High energy 1064 nm Q-switched laser output is obtained by LD vertical array end pumping Nd:YAG. Cylindrical lens are used for beam shaping of LD array for different divergence angle of fast and slow axis. Based on the theoretical simulation of fundamental mode radius using ABCD transfer matrix, the resonant cavity is optimized and curvature radius of cavity mirrors is determined. The intracavity power density is calculated according to the output laser pulse energy and transmittance of output coupling mirror is optimized under the condition that optical device is not damaged. 1064 nm laser with a maximum output of 110 mJ is generated under LD pump energy of 600 mJ, corresponding to optical conversion efficiency of 18.3%. The laser pulse width is 11 ns and divergence angle is 1.2 mrad. For saturation phenomenon of Q-switched laser output, LD temperature is adjusted to make wavelength deviate from absorption peak of Nd:YAG crystal. The parasitic oscillation, which affects the enhancement of Q-switched laser energy, can be effectively suppressed by reducing gain of pump end of laser medium, which provides an effective technical means for obtaining high energy end-pumped Q-switched laser.
CMO YAG laser damage test facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hue, J.; Dijon, J.; Lyan, P.

1996-12-31

The CMO YAG laser damage test facility, which is equipped with a 30Hz laser, is presented in this paper. The main points are described below: (1) The characteristics of the laser beam and the in situ damage detection technique (a scattered light measurement system) are perfectly suited to work up to the frequency of the laser. They are monitored in real time, and work at three wavelengths: 1064 nm, 532 nm, 355 nm. (2) With this same shutter, it is possible to automatically stop the laser on the pulse which induces the first damages. These automatic capabilities enable the samplesmore » to be tested quickly. (3) A Nomarski microscope supplied with a 16-bit CCD camera enables the test sites to be photographed before and after the laser interaction. Image processing enables the authors to extract the first damages. before and after the laser interaction. Image processing enables them to extract the first damages. (4) Six pulse widths are available (between 3ns and 13ns). Therefore, with all these characterization tools, many kinds of laser tests may be considered. These different features are illustrated by experimental results (1-on-1 test or R-on-1 test).« less
Synthesis of Al2O3 thin films using laser assisted spray pyrolysis (LASP)

NASA Astrophysics Data System (ADS)

Dhonge, Baban P.; Mathews, Tom; Tripura Sundari, S.; Krishnan, R.; Balamurugan, A. K.; Kamruddin, M.; Subbarao, R. V.; Dash, S.; Tyagi, A. K.

2013-01-01

The present study reports the development of a laser assisted ultrasonic spray pyrolysis technique and synthesis of dense optical alumina films using the same. In this technique ultrasonically generated aerosols of aluminum acetylacetonate dissolved in ethanol and a laser beam (Nd:YAG, CW, 1064 nm) were fed coaxially and concurrently through a quartz tube on to a hot substrate mounted on an X-Y raster stage. At the laser focused spot the precursor underwent solvent evaporation and solute sublimation followed by precursor vapor decomposition giving rise to oxide coating, the substrate is rastered to get large surface area coating. The surface morphology revealed coalescence of particles with increase in laser power. The observed particle sizes were 17 nm for films synthesized without laser and 18, 21 and 25 nm for films made with laser at 25, 38 and 50 W, respectively. Refractive index of the films synthesized increased from 1.56 to 1.62 as the laser power increased from 0 to 50 W. The stoichiometry of films was studied using XPS and the increase in interfacial layer thickness with laser power was observed from dynamic SIMS depth profiling and ellipsometry.
Femtosecond laser fabrication of birefringent directional couplers as polarization beam splitters in fused silica.

PubMed

Fernandes, Luís A; Grenier, Jason R; Herman, Peter R; Aitchison, J Stewart; Marques, Paulo V S

2011-06-20

Integrated polarization beam splitters based on birefringent directional couplers are demonstrated. The devices are fabricated in bulk fused silica glass by femtosecond laser writing (300 fs, 150 nJ at 500 kHz, 522 nm). The birefringence was measured from the spectral splitting of the Bragg grating resonances associated with the vertically and horizontally polarized modes. Polarization splitting directional couplers were designed and demonstrated with 0.5 dB/cm propagation losses and -19 dB and -24 dB extinction ratios for the polarization splitting.

Evaluating the influence of laser wavelength and detection stage geometry on optical detection efficiency in a single-particle mass spectrometer

NASA Astrophysics Data System (ADS)

Marsden, Nicholas; Flynn, Michael J.; Taylor, Jonathan W.; Allan, James D.; Coe, Hugh

2016-12-01

Single-particle mass spectrometry (SPMS) is a useful tool for the online study of aerosols with the ability to measure size-resolved chemical composition with a temporal resolution relevant to atmospheric processes. In SPMS, optical particle detection is used for the effective temporal alignment of an ablation laser pulse with the presence of a particle in the ion source, and it gives the option of aerodynamic sizing by measuring the offset of particle arrival times between two detection stages. The efficiency of the optical detection stage has a strong influence on the overall instrument performance. A custom detection laser system consisting of a high-powered fibre-coupled Nd:YAG solid-state laser with a collimated beam was implemented in the detection stage of a laser ablation aerosol particle time-of-flight (LAAP-TOF) single-particle mass spectrometer without major modifications to instrument geometry. The use of a collimated laser beam permitted the construction of a numerical model that predicts the effects of detection laser wavelength, output power, beam focussing characteristics, light collection angle, particle size, and refractive index on the effective detection radius (R) of the detection laser beam. We compare the model predictions with an ambient data set acquired during the Ice in Clouds Experiment - Dust (ICE-D) project. The new laser system resulted in an order-of-magnitude improvement in instrument sensitivity to spherical particles in the size range 500-800 nm compared to a focussed 405 nm laser diode system. The model demonstrates that the limit of detection in terms of particle size is determined by the scattering cross section (Csca) as predicted by Mie theory. In addition, if light is collected over a narrow collection angle, oscillations in the magnitude of Csca with respect to particle diameter result in a variation in R, resulting in large particle-size-dependent variation in detection efficiency across the particle transmission range. This detection bias is imposed on the aerodynamic size distributions measured by the instrument and accounts for some of the detection bias towards sea salt particles in the ambient data set.
Effect of Fiberoptic Collimation Technique on 808 nm Wavelength Laser Stimulation of Cochlear Neurons.

PubMed

Wang, Jingxuan; Lu, Jianren; Tian, Lan

2016-06-01

The purpose of this study was to evaluate the effects of fiberoptic collimation technique on auditory neural stimulation in the cochlea with 808 nm wavelength lasers. Recently, the pulsed near-infrared lasers in the 800-1000 nm wavelength range have been investigated as an emerging technique to trigger auditory neural response in the cochlea. A laser beam divergence in the optical stimulation pathway exists, which may affect stimulation efficiency and spatial selectivity. The fiberoptic collimation technique was proposed for cochlear neuron stimulation, and the C-lens element was designed as the collimation structure. The spiral ganglion cells in deafened guinea pigs' cochlea were irradiated with collimated and uncollimated near-infrared lasers. Optically evoked auditory brainstem response (OABR) under the two laser output modes were recorded. Laser with the collimation technique evoked an average 58% higher OABR amplitude than the uncollimated laser output. In addition, the collimated laser setup consumed on average 35.2% of laser energy compared with the uncollimated laser when evoking the same OABR amplitude. The fiberoptic collimation technique improved stimulation efficiency and reduced stimulating energy consumption in near-infrared neural stimulation in cochlea. The positive effects of laser collimation technique could benefit further research in optically based cochlear implants.
Role of defects in laser-induced modifications of silica coatings and fused silica using picosecond pulses at 1053 nm: II Scaling laws and the density of precursors

DOE PAGES

Laurence, T. A.; Negres, R. A.; Ly, S.; ...

2017-06-22

Here, we investigate the role of defects in laser-induced damage of fused silica and of silica coatings produced by e-beam and PIAD processes which are used in damage resistant, multi-layer dielectric, reflective optics. We perform experiments using 1053 nm, 1–60 ps laser pulses with varying beam size, number of shots, and pulse widths in order to understand the characteristics of defects leading to laser-induced damage. This pulse width range spans a transition in mechanisms from intrinsic material ablation for short pulses to defect-dominated damage for longer pulses. We show that for pulse widths as short as 10 ps, laser-induced damagemore » properties of fused silica and silica films are dominated by isolated absorbers. The density of these precursors and their fluence dependence of damage initiation suggest a single photon process for initial energy absorption in these precursors. Higher density precursors that initiate close to the ablation threshold at shorter pulse widths are also observed in fused silica, whose fluence and pulse width scaling suggest a multiphoton initiation process. We also show that these initiated damage sites grow with subsequent laser pulses. We show that scaling laws obtained in more conventional ways depend on the beam size and on the definition of damage for ps pulses. For this reason, coupling scaling laws with the density of precursors are critical to understanding the damage limitations of optics in the ps regime.« less
Role of defects in laser-induced modifications of silica coatings and fused silica using picosecond pulses at 1053 nm: II Scaling laws and the density of precursors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laurence, T. A.; Negres, R. A.; Ly, S.

Here, we investigate the role of defects in laser-induced damage of fused silica and of silica coatings produced by e-beam and PIAD processes which are used in damage resistant, multi-layer dielectric, reflective optics. We perform experiments using 1053 nm, 1–60 ps laser pulses with varying beam size, number of shots, and pulse widths in order to understand the characteristics of defects leading to laser-induced damage. This pulse width range spans a transition in mechanisms from intrinsic material ablation for short pulses to defect-dominated damage for longer pulses. We show that for pulse widths as short as 10 ps, laser-induced damagemore » properties of fused silica and silica films are dominated by isolated absorbers. The density of these precursors and their fluence dependence of damage initiation suggest a single photon process for initial energy absorption in these precursors. Higher density precursors that initiate close to the ablation threshold at shorter pulse widths are also observed in fused silica, whose fluence and pulse width scaling suggest a multiphoton initiation process. We also show that these initiated damage sites grow with subsequent laser pulses. We show that scaling laws obtained in more conventional ways depend on the beam size and on the definition of damage for ps pulses. For this reason, coupling scaling laws with the density of precursors are critical to understanding the damage limitations of optics in the ps regime.« less
Precision and resolution in laser direct microstructuring with bursts of picosecond pulses

NASA Astrophysics Data System (ADS)

Mur, Jaka; Petkovšek, Rok

2018-01-01

Pulsed laser sources facilitate various applications, including efficient material removal in different scientific and industrial applications. Commercially available laser systems in the field typically use a focused laser beam of 10-20 μm in diameter. In line with the ongoing trends of miniaturization, we have developed a picosecond fiber laser-based system combining fast beam deflection and tight focusing for material processing and optical applications. We have predicted and verified the system's precision, resolution, and minimum achievable feature size for material processing applications. The analysis of the laser's performance requirements for the specific applications of high-precision laser processing is an important aspect for further development of the technique. We have predicted and experimentally verified that maximal edge roughness of single-micrometer-sized features was below 200 nm, including the laser's energy and positioning stability, beam deflection, the effect of spot spacing, and efficient isolation of mechanical vibrations. We have demonstrated that a novel fiber laser operating regime in bursts of pulses increases the laser energy stability. The results of our research improve the potential of fiber laser sources for material processing applications and facilitate their use through enabling the operation at lower pulse energies in bursts as opposed to single pulse regimes.
Object-oriented wavefront correction in an asymmetric amplifying high-power laser system

NASA Astrophysics Data System (ADS)

Yang, Ying; Yuan, Qiang; Wang, Deen; Zhang, Xin; Dai, Wanjun; Hu, Dongxia; Xue, Qiao; Zhang, Xiaolu; Zhao, Junpu; Zeng, Fa; Wang, Shenzhen; Zhou, Wei; Zhu, Qihua; Zheng, Wanguo

2018-05-01

An object-oriented wavefront control method is proposed aiming for excellent near-field homogenization and far-field distribution in an asymmetric amplifying high-power laser system. By averaging the residual errors of the propagating beam, smaller pinholes could be employed on the spatial filters to improve the beam quality. With this wavefront correction system, the laser performance of the main amplifier system in the Shen Guang-III laser facility has been improved. The residual wavefront aberration at the position of each pinhole is below 2 µm (peak-to-valley). For each pinhole, 95% of the total laser energy is enclosed within a circle whose diameter is no more than six times the diffraction limit. At the output of the main laser system, the near-field modulation and contrast are 1.29% and 7.5%, respectively, and 95% of the 1ω (1053 nm) beam energy is contained within a 39.8 µrad circle (6.81 times the diffraction limit) under a laser fluence of 5.8 J cm-2. The measured 1ω focal spot size and near-field contrast are better than the design values of the Shen Guang-III laser facility.
Blue diode laser: a new approach in oral surgery?

NASA Astrophysics Data System (ADS)

Fornaini, Carlo; Merigo, Elisabetta; Selleri, Stefano; Cucinotta, Annamaria

2016-02-01

The introduction of diode lasers in dentistry had several advantages, principally consisting on the reduced size, reduced cost and possibility to beam delivering by optical fibbers. Up today two diode wavelengths, 810 and 980 nm, were the most utilized in oral surgery but recently a new wavelength emitting in the blue had been proposed. The aim of this ex vivo study was to compare the efficacy of five laser wavelengths (450, 532, 808, 1064 and 1340 nm) for the ablation of soft tissues. Specimens were surgically collected from the dorsal surface of four bovine tongues and irradiated by the five different wavelengths. Thermal increase was measured by two thermocouples, the first at a depth of 0.5 mm, and the second at a depth of 2 mm while initial and final surface temperatures were recorded by IR thermometer. The quality of the incision was histologically evaluated by a pathologist by giving a score from 0 to 5. The time necessary to perform the excision varied between 215 seconds (1340 nm, 5W) and 292 seconds (808 nm, 3W). Surface temperature increase was highest for 1340 nm, 5W and lowest for 405 nm, 4 W. The most significant deep temperature increase was recorded by 1340 nm, 5 W and the lowest by 450 nm, 2 W. The quality of incision was better and the thermal elevation lower in the specimens obtained with shortest laser wavelength (450 nm).
Incoherent beam combining of fiber lasers by an all-fiber 7 × 1 signal combiner at a power level of 14 kW.

PubMed

Lei, Chengmin; Gu, Yanran; Chen, Zilun; Wang, Zengfeng; Zhou, Pu; Ma, Yanxing; Xiao, Hu; Leng, Jinyong; Wang, Xiaolin; Hou, Jing; Xu, Xiaojun; Chen, Jinbao; Liu, Zejin

2018-04-16

We demonstrate an all-fiber 7 × 1 signal combiner with an output core diameter of 50 μm for high power incoherent beam combining of seven self-made Yb-doped single-mode fiber lasers around a wavelength of 1080 nm and output power of 2 kW. 14.1 kW combined output power is achieved with a total transmission efficiency of higher than 98.5% and a beam quality of M 2 = 5.37, which is close to the theoretical results based on finite-difference beam propagation technique. To the best of our knowledge, this is the highest output power ever reported for all-fiber structure beam combining generation, which indicates the feasibility and potential of >10 kW high brightness incoherent beam combining based on an all-fiber signal combiner.
Physiological Monitoring of Optically Trapped Cells: Studying the Effects of Confinement by 1064 NM Lazer Tweezers Using Microfluorometry

NASA Astrophysics Data System (ADS)

Liu, Yagang

A novel technique that combines microfluorometric detection and optical laser trapping has been developed for in-situ assessing the physiological state of an optically trapped biological sample. This optical diagnostic technique achieves high sensitivity (>30 dB signal -to-noise ratio) and high spatial resolution (~ 1 μm) over a broad spectral range (>400 nm). The fluorescence spectra derived from exogenous fluorescent probes, including laurdan, acridine orange, propidium iodide and Snarf, are used to assess the effects of optical confinement with respect to temperature, DNA structure, cell viability, and intracellular pH, respectively. In the latter three cases, fluorescence is excited via a two-photon absorption process, using the cw laser trap itself as the fluorescence excitation source. This enables the cw near infrared laser trapping beam to be used simultaneously as an optical diagnostic probe as well as an optical micromanipulator. Using microfluorometry, a temperature increase of less than several degrees centigrade was measured for test samples, including liposomes, Chinese hamster ovary (CHO) cells and human sperm cells that were held stationary by 1064 nm optical tweezers having a power density of ~10^7 W/cm^2. Additional physiological monitoring experiments indicated that there is no observable denaturation of DNA, or change of intracellular pH under typical continuous wave laser trapping conditions (P <= 400 mW). Under some circumstances, however, it was possible to achieve a decrease in cell viability with cw trapping, as monitored by a live/dead vital stain. In comparison, significant DNA denaturation and cellular physiological changes (e.g. cell death) were observed when a Q-switched pulsed laser at a threshold of ~30mu J/pulse was used as trapping source. These results generally support the conclusion that cw laser trapping at 1064 nm wavelength is a safe, non-invasive process and should prove to be of great value for understanding the mechanisms of laser microirradiation effects on living cells held stationary in a near-infrared trapping beam.
Recent developments in heterodyne laser interferometry at Harbin Institute of Technology

NASA Astrophysics Data System (ADS)

Hu, P. C.; Tan, J. B. B.; Yang, H. X. X.; Fu, H. J. J.; Wang, Q.

2013-01-01

In order to fulfill the requirements for high-resolution and high-precision heterodyne interferometric technologies and instruments, the laser interferometry group of HIT has developed some novel techniques for high-resolution and high-precision heterodyne interferometers, such as high accuracy laser frequency stabilization, dynamic sub-nanometer resolution phase interpolation and dynamic nonlinearity measurement. Based on a novel lock point correction method and an asymmetric thermal structure, the frequency stabilized laser achieves a long term stability of 1.2×10-8, and it can be steadily stabilized even in the air flowing up to 1 m/s. In order to achieve dynamic sub-nanometer resolution of laser heterodyne interferometers, a novel phase interpolation method based on digital delay line is proposed. Experimental results show that, the proposed 0.62 nm, phase interpolator built with a 64 multiple PLL and an 8-tap digital delay line achieves a static accuracy better than 0.31nm and a dynamic accuracy better than 0.62 nm over the velocity ranging from -2 m/s to 2 m/s. Meanwhile, an accuracy beam polarization measuring setup is proposed to check and ensure the light's polarization state of the dual frequency laser head, and a dynamic optical nonlinearity measuring setup is built to measure the optical nonlinearity of the heterodyne system accurately and quickly. Analysis and experimental results show that, the beam polarization measuring setup can achieve an accuracy of 0.03° in ellipticity angles and an accuracy of 0.04° in the non-orthogonality angle respectively, and the optical nonlinearity measuring setup can achieve an accuracy of 0.13°.
Structuring by field enhancement of glass, Ag, Au, and Co thin films using short pulse laser ablation

NASA Astrophysics Data System (ADS)

Ulmeanu, M.; Zamfirescu, M.; Rusen, L.; Luculescu, C.; Moldovan, A.; Stratan, A.; Dabu, R.

2009-12-01

Single pulse laser ablation of glass, Ag, Au, and Co thin films was experimentally investigated with a laser pulse width of 400 ps at a wavelength of 532 nm both in the far and near fields. In the far-field regime, the electromagnetic field results from a focused laser beam, while the near-field regime is realized by a combination of the focused laser beam incident on a spherical colloidal particle. For the near-field experiments we have used polystyrene colloidal particles of 700 nm diameter self-assembled or spin coated on top of the surfaces. Laser fluences applied are in the range of 0.01-10 J/cm2. The diameter and the morphologies of the ablated holes were investigated by optical microscopy, profilometry, scanning electron microscopy, and atomic force microscopy. The dependence of the shape of the holes reflects the fluence regime and the thermophysical properties, i.e., melting temperature and thermal diffusivity of the surfaces involved in the experiments. We give quantitative data about the fluence threshold, diameter, and depth ablation dependence for the far and near fields and discuss their values with respect to the enhancement factor of the intensity of the electromagnetic field due to the use of the colloidal particles. Theoretical estimations of the intensity enhancement were done using the finite-difference time-domain method by using the RSOFT software. The application of near fields allows structuring of the surfaces with structure dimension in the order of 100 nm and even below.
Effective temperature of an ultracold electron source based on near-threshold photoionization.

PubMed

Engelen, W J; Smakman, E P; Bakker, D J; Luiten, O J; Vredenbregt, E J D

2014-01-01

We present a detailed description of measurements of the effective temperature of a pulsed electron source, based on near-threshold photoionization of laser-cooled atoms. The temperature is determined by electron beam waist scans, source size measurements with ion beams, and analysis with an accurate beam line model. Experimental data is presented for the source temperature as a function of the wavelength of the photoionization laser, for both nanosecond and femtosecond ionization pulses. For the nanosecond laser, temperatures as low as 14 ± 3 K were found; for femtosecond photoionization, 30 ± 5 K is possible. With a typical source size of 25 μm, this results in electron bunches with a relative transverse coherence length in the 10⁻⁴ range and an emittance of a few nm rad. © 2013 Elsevier B.V. All rights reserved.
High-power green and blue electron-beam pumped surface-emitting lasers using dielectric and epitaxial distributed Bragg reflectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klein, T., E-mail: tklein@ifp.uni-bremen.de; Klembt, S.; Institut Néel, Université Grenoble Alpes and CNRS, B.P. 166, 38042 Grenoble

2015-03-21

ZnSe-based electron-beam pumped vertical-cavity surface-emitting lasers for the green (λ = 530 nm) and blue (λ = 462 nm) spectral region have been realized. Structures with and without epitaxial bottom distributed Bragg reflector have been fabricated and characterized. The samples consist of an active region containing 20 quantum wells with a cavity length varying between an optical thickness of 10 λ to 20 λ. The active material is ZnCdSSe in case of the green devices and ZnSe for the blue ones. Room temperature single mode lasing for structures with and without epitaxial bottom mirror with a maximum output power up to 5.9 W (green) and 3.3 W (blue)more » is achieved, respectively.« less
Augmented reality in laser laboratories

NASA Astrophysics Data System (ADS)

Quercioli, Franco

2018-05-01

Laser safety glasses block visibility of the laser light. This is a big nuisance when a clear view of the beam path is required. A headset made up of a smartphone and a viewer can overcome this problem. The user looks at the image of the real world on the cellphone display, captured by its rear camera. An unimpeded and safe sight of the laser beam is then achieved. If the infrared blocking filter of the smartphone camera is removed, the spectral sensitivity of the CMOS image sensor extends in the near infrared region up to 1100 nm. This substantial improvement widens the usability of the device to many laser systems for industrial and medical applications, which are located in this spectral region. The paper describes this modification of a phone camera to extend its sensitivity beyond the visible and make a true augmented reality laser viewer.
Pump-probe imaging of nanosecond laser-induced bubbles in distilled water solutions: Observations of laser-produced-plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evans, R.; Camacho-Lopez, S.

2010-11-15

This article presents the analysis of the laser-produced-plasma (LPP) formed by the focusing of a 9 ns laser pulse, {lambda}=532 nm, with a NA=0.6 aspherical lens using energies between 100-1500 {mu}J, into distilled water with varying solutions of table salt. Observations of the filamentation plasma were made, which are explained by self-focusing of the laser pulse by the LPP through ponderomotive cavitation of the electron plasma in the center of the beam. The filamentation of the beam through a low density plasma wave guide explains why the transmission of the pump laser through the interaction region was notably higher onmore » previous experiments that we performed [R. Evans et al., Opt. Express 16, 7481 (2008)], than a very similar set of experiments performed by Noack and Vogel [IEEE J. Quantum Electron. 35, 1156 (1999)].« less
Record fifth-harmonic-generation efficiency producing 211 nm, joule-level pulses using cesium lithium borate

DOE PAGES

Begishev, I. A.; Bromage, J.; Yang, S. T.; ...

2018-05-16

The fifth harmonic of a pulsed Nd:YLF laser has been realized in a cascade of nonlinear crystals with a record efficiency of 30%. Cesium lithium borate is used in a Type-I configuration for sum-frequency mixing of 1053 nm and 266 nm, producing 211-nm pulses. Flattopped beam profiles and pulse shapes optimize efficiency. Furthermore, energies of the fifth harmonic up to 335 mJ in 2.4 ns pulses were demonstrated.
Record fifth-harmonic-generation efficiency producing 211 nm, joule-level pulses using cesium lithium borate

DOE PAGES

Begishev, I. A.; Bromage, J.; Yang, S. T.; ...

2018-01-01

The fifth harmonic of a pulsed Nd:YLF laser has been realized in a cascade of nonlinear crystals with a record efficiency of 30%. Cesium lithium borate is used in a Type-I configuration for sum-frequency mixing of 1053 nm and 266 nm, producing 211-nm pulses. Flattopped beam profiles and pulse shapes optimize efficiency. Energies of the fifth harmonic up to 335 mJ in 2.4 ns pulses were demonstrated.
Record fifth-harmonic-generation efficiency producing 211 nm, joule-level pulses using cesium lithium borate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Begishev, I. A.; Bromage, J.; Yang, S. T.

The fifth harmonic of a pulsed Nd:YLF laser has been realized in a cascade of nonlinear crystals with a record efficiency of 30%. Cesium lithium borate is used in a Type-I configuration for sum-frequency mixing of 1053 nm and 266 nm, producing 211-nm pulses. Flattopped beam profiles and pulse shapes optimize efficiency. Furthermore, energies of the fifth harmonic up to 335 mJ in 2.4 ns pulses were demonstrated.
Laser diode fiber optic apparatus for acupuncture treatment by the Oriental method

NASA Astrophysics Data System (ADS)

Pham, Van Hoi; Phung, Huu A.; Bui, Huy; Hoang, Cao D.; Vu, Duc T.; Tran, Minh T.; Nguyen, Minh H.

1998-08-01

The laser acupuncture equipment using laser diodes of 850, 1300 nm and optical fibers as light needles is presented. The double-frequency modulation of laser beam gives the high efficiency treatment of the low-power laser therapy by the oriental acupuncture method. The laser spot from optical fiber of 50 microns is suitable for the irradiation into special points on body or auricular by the acupuncture treatment schema. The laser intensity in pulse regime of 5 - 40 W/cm2 and irradiation time of 5 - 15 minutes are optimum for treatment of neurosis symptoms and pain-relieving.
High-efficiency volume holograms recording on acrylamide and N,N'methylene-bis-acrylamide photopolymer with pulsed laser

NASA Astrophysics Data System (ADS)

Gallego, Sergi; Ortuno, Manuel; Garcia, Celia; Neipp, Cristian; Belendez, Augusto; Pascual, Inmaculada V.

2004-09-01

In order to achieve higher diffraction efficiencies of the volume gratings stored in acrylamide based photopolymer, we introduce in the photopolymer a crosslinker (N,N'methylene-bis-acrylamide). The presence of this component increase the rate polymerization and the modulation of refraction index. The recording was performed using a holographic copying process. The original was a grating of 1000 lines/mm processed using silver halide sensitized gelatine, with diffraction efficiency around 50 % for a reconstruction wavelength of 532 nm. The main beam was split in two secondary beams by the original grating, with an intensity ratio 1:1. The results obtained using the new composition of material are compared with the composition without crosslinker. In the other hand the no linearity of the material's response is also studied comparing the energetic sensitivity, diffraction efficiencies and index modulation of gratings recorded with pulsed and continuous laser. This study is realized fitting the angular scan of each grating using Kogelnik's theory. The gratings are recorded with wavelength of 532 nm when pulsed exposure is used and with wavelength of 514 nm when continues exposure is used. Using pulsed laser at 532 nm the photopolymer without crosslinker presents the diffraction efficiencies lightly smaller than 60%. In the other hand when the crosslinker has been introduced in photopolymer composition, the diffraction efficiencies achieves are higher than 85 %.

Waveguide Harmonic Generator for the SIM

NASA Technical Reports Server (NTRS)

Chang, Daniel; Poberezhskiy, Ilya; Mulder, Jerry

2008-01-01

A second-harmonic generator (SHG) serves as the source of the visible laser beam in an onboard calibration scheme for NASA's planned Space Interferometry Mission (SIM), which requires an infrared laser beam and a visible laser beam coherent with the infrared laser beam. The SHG includes quasi-phase-matched waveguides made of MgO-doped, periodically poled lithium niobate, pigtailed with polarization- maintaining optical fibers. Frequency doubling by use of such waveguides affords the required combination of coherence and sufficient conversion efficiency for the intended application. The spatial period of the poling is designed to obtain quasi-phase- matching at a nominal middle excitation wavelength of 1,319.28 nm. The SHG is designed to operate at a warm bias (ambient temperature between 20 and 25 C) that would be maintained in its cooler environment by use of electric heaters; the heater power would be adjusted to regulate the temperature precisely and thereby maintain the required precision of the spatial period. At the state of development at the time of this reporting, the SHG had been packaged and subjected to most of its planned space-qualification tests.
Structure Optimization of 21,23-Core-Modified Porphyrins Absorbing Long-Wavelength Light as Potential Photosensitizers Against Breast Cancer Cells

DTIC Science & Technology

2006-04-01

recording singlet oxygen emission spectra. A diode -pumped solid-state laser (Millenia X, Spectra-Physics) at 532 nm was the excitation source. The sample...biological properties in vitro Youngjae You,a,* Scott L. Gibsonb and Michael R. Dettya aInstitute for Lasers , Photonics, and Biophotonics, Department...relative to the exciting laser beam. An additional long-pass filter (850LP) was used to attenuate the excitation laser and the fluorescence from the
Laser-induced caesium-137 decay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barmina, E V; Simakin, A V; Shafeev, G A

2014-08-31

Experimental data are presented on the laser-induced beta decay of caesium-137. We demonstrate that the exposure of a gold target to a copper vapour laser beam (wavelengths of 510.6 and 578.2 nm, pulse duration of 15 ns) for 2 h in an aqueous solution of a caesium-137 salt reduces the caesium-137 activity by 70%, as assessed from the gamma activity of the daughter nucleus {sup 137m}Ba, and discuss potential applications of laser-induced caesium-137 decay in radioactive waste disposal. (letters)
Aerospace Sponsored Research Summary Report for 1 October 1989 Through 30 September 1990. Scientific and Engineering Research

DTIC Science & Technology

1990-12-01

3,4]. This work allowed us to view the ultrashort ( - 100 fs) pulses . While this laser was being temporal characteristics of the absorption spectrum...regions of high intensity in single water drop- lets (a = 60 Ant) following excita- tion by a single 7-ns, 532-nn laser pulse . Resonant 532-nm laser ...electronic properties of cluster ions of ion beam and the laser pulse , any desired mass range for simple metals (alkali metals). Our earlier efforts
Experimental Investigation of the Influence of the Laser Beam Waist on Cold Atom Guiding Efficiency.

PubMed

Song, Ningfang; Hu, Di; Xu, Xiaobin; Li, Wei; Lu, Xiangxiang; Song, Yitong

2018-02-28

The primary purpose of this study is to investigate the influence of the vertical guiding laser beam waist on cold atom guiding efficiency. In this study, a double magneto-optical trap (MOT) apparatus is used. With an unbalanced force in the horizontal direction, a cold atomic beam is generated by the first MOT. The cold atoms enter the second chamber and are then re-trapped and cooled by the second MOT. By releasing a second atom cloud, the process of transferring the cold atoms from MOT to the dipole trap, which is formed by a red-detuned converged 1064-nm laser, is experimentally demonstrated. And after releasing for 20 ms, the atom cloud is guided to a distance of approximately 3 mm. As indicated by the results, the guiding efficiency depends strongly on the laser beam waist; the efficiency reaches a maximum when the waist radius ( w ₀) of the laser is in the range of 15 to 25 μm, while the initial atom cloud has a radius of 133 μm. Additionally, the properties of the atoms inside the dipole potential trap, such as the distribution profile and lifetime, are deduced from the fluorescence images.
Metasurface-assisted orbital angular momentum carrying Bessel-Gaussian Laser: proposal and simulation.

PubMed

Zhou, Nan; Wang, Jian

2018-05-23

Bessel-Gaussian beams have distinct properties of suppressed diffraction divergence and self-reconstruction. In this paper, we propose and simulate metasurface-assisted orbital angular momentum (OAM) carrying Bessel-Gaussian laser. The laser can be regarded as a Fabry-Perot cavity formed by one partially transparent output plane mirror and the other metasurface-based reflector mirror. The gain medium of Nd:YVO 4 enables the lasing wavelength at 1064 nm with a 808 nm laser serving as the pump. The sub-wavelength structure of metasurface facilitates flexible spatial light manipulation. The compact metasurface-based reflector provides combined phase functions of an axicon and a spherical mirror. By appropriately selecting the size of output mirror and inserting mode-selection element in the laser cavity, different orders of OAM-carrying Bessel-Gaussian lasing modes are achievable. The lasing Bessel-Gaussian 0 , Bessel-Gaussian 01 + , Bessel-Gaussian 02 + and Bessel-Gaussian 03 + modes have high fidelities of ~0.889, ~0.889, ~0.881 and ~0.879, respectively. The metasurface fabrication tolerance and the dependence of threshold power and output lasing power on the length of gain medium, beam radius of pump and transmittance of output mirror are also discussed. The obtained results show successful implementation of metasurface-assisted OAM-carrying Bessel-Gaussian laser with favorable performance. The metasurface-assisted OAM-carrying Bessel-Gaussian laser may find wide OAM-enabled communication and non-communication applications.
50W CW output power and 12mJ pulses from a quasi-2-level Yb:YAG ceramic rod laser end-pumped at the 969nm zero-phonon line

NASA Astrophysics Data System (ADS)

Fries, Christian; Weitz, Marco; Theobald, Christian; v. Löwis of Menar, Patric; Bartschke, Jürgen; L'huillier, Johannes A.

2015-02-01

With the advent of high power and narrow bandwidth 969 nm pump diodes, direct pumping into the upper laser level of Yb:YAG and hence quasi-2-level lasers became possible. Pumping directly into the emitting level leads to higher quantum efficiency and reduction of non-radiative decay. Consequently, thermal load, thermal lensing and risk of fracture are reduced significantly. Moreover pump saturation and thermal population of uninvolved energy-levels in ground and excited states are benefical for a homogenous distribution of the pump beam as well as the reduction of reabsorption loss compared to 3-level systems, which allows for high-power DPSS lasers. Beside continuous-wave (cw) operation, nanosecond pulses with a repetition rate between 1 and 5 kHz are an attractive alternative to flashlamp-pumped systems (10-100 Hz) in various measurement applications that require higher data acquisition rates because of new faster detectors. Based on measurements of the absorption and a detailed numerical model for pump beam distribution, including beam propagation and saturation factors, power-scaling of a ceramic rod Yb:YAG oscillator was possible. Finally a cw output power of 50 W with 33 % pump efficiency at 1030 nm has been demonstrated (M2 < 1.2). Nanosecond pulses have been produced by cavity-dumping of this system. The cavity-dumped setup allowed for 3-10 ns pulses with a pulse energy of 12.5 mJ at 1 kHz (M2 < 1.1). In order to achieve these results a systematic experimental and numerical investigation on gain dynamics and the identification of different stable operating regimes has been carried out.
Ripeness detection simulation of oil palm fruit bunches using laser-based imaging system

NASA Astrophysics Data System (ADS)

Shiddiq, Minarni; Fitmawati, Anjasmara, Ridho; Sari, Nurmaya; Hefniati

2017-01-01

Ripeness is one of important factors for quality sorting of harvested oil palm fresh fruit bunches (FFB). Traditional ripeness classifications using FFB color and number of fruit loose for harvesting have some disadvantages especially for high oil palm trees. A laser based imaging system is proposed to substitute the traditional method. In this study, ripeness detection simulation of oil palm FFBs was performed. The system composed of two diode lasers with 532 nm and 680 nm in wavelengths and a CMOS camera which was set on a rotating plate for easy adjustment of laser beam hitting FFB. The FFB samples were placed on an aluminum platform with 4 height variations, 1.5 m, 2 m, 2.5 m, and 3 m. The relations of reflectance intensities represented by Red Green Blue (RGB) values of the FFB images to the height variations and ripeness levels of FFBs with and without laser beam were analyzed. The samples were from Tenera variety with 4 ripeness levels called F0, F1, F3, and F4. The results showed that the red component of RGB values were dominant for FFBs without laser and with red laser. The average RGB values are higher for F3 (ripe) level and F4 (overripe). Imaging with green laser showed consistency. Imaging methods using laser was able to differentiate ripeness levels of oil palm fresh fruit bunch, it could be applied for future remote detection of oil palm FFB ripeness.
Using femtosecond laser to fabricate highly precise interior three-dimensional microstructures in polymeric flow chip

PubMed Central

Lee, Chia-Yu; Chang, Ting-Chou; Wang, Shau-Chun; Chien, Chih-Wei; Cheng, Chung-Wei

2010-01-01

This paper reports using femtosecond laser marker to fabricate the three-dimensional interior microstructures in one closed flow channel of plastic substrate. Strip-like slots in the dimensions of 800 μm×400 μm×65 μm were ablated with pulse Ti:sapphire laser at 800 nm (pulse duration of ∼120 fs with 1 kHz repetition rate) on acrylic slide. After ablation, defocused beams were used to finish the surface of microstructures. Having finally polished with sonication, the laser fabricated structures are highly precise with the arithmetic roughness of 1.5 and 4.5 nm. Fabricating such highly precise microstructures cannot be accomplished with nanosecond laser marking or other mechanical drilling methods. In addition, since laser ablation can directly engrave interior microstructures in one closed chip, glue smearing problems to damage molded microstructures possibly to occur during the chip sealing procedures can be avoided too. PMID:21079695
Using femtosecond laser to fabricate highly precise interior three-dimensional microstructures in polymeric flow chip.

PubMed

Lee, Chia-Yu; Chang, Ting-Chou; Wang, Shau-Chun; Chien, Chih-Wei; Cheng, Chung-Wei

2010-10-18

This paper reports using femtosecond laser marker to fabricate the three-dimensional interior microstructures in one closed flow channel of plastic substrate. Strip-like slots in the dimensions of 800 μm×400 μm×65 μm were ablated with pulse Ti:sapphire laser at 800 nm (pulse duration of ∼120 fs with 1 kHz repetition rate) on acrylic slide. After ablation, defocused beams were used to finish the surface of microstructures. Having finally polished with sonication, the laser fabricated structures are highly precise with the arithmetic roughness of 1.5 and 4.5 nm. Fabricating such highly precise microstructures cannot be accomplished with nanosecond laser marking or other mechanical drilling methods. In addition, since laser ablation can directly engrave interior microstructures in one closed chip, glue smearing problems to damage molded microstructures possibly to occur during the chip sealing procedures can be avoided too.
Efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser.

PubMed

Wang, P; Cooper, L J; Sahu, J K; Clarkson, W A

2006-01-15

A novel approach to achieving robust single-spatial-mode operation of cladding-pumped fiber lasers with multimode cores is reported. The approach is based on the use of a fiber geometry in which the core has a helical trajectory within the inner cladding to suppress laser oscillation on higher-order modes. In a preliminary proof-of-principle study, efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser with a 30 microm diameter core and a numerical aperture of 0.087 has been demonstrated. The laser yielded 60.4 W of output at 1043 nm in a beam with M2 < 1.4 for 92.6 W launched pump power from a diode stack at 976 nm. The slope efficiency at pump powers well above threshold was approximately 84%, which compares favorably with the slope efficiencies achievable with conventional straight-core Yb-doped double-clad fiber lasers.
Trace analysis of pollutants in water using the photothermal interferometry as HPLC detector.

PubMed

Seidel, B S; Dübel, O; Faubel, W; Ache, H J

1996-03-01

A new procedure including high performance liquid chromatography in combination with photothermal interference spectroscopy as detection device (HPLC/PIS) has been proposed, optimized and its figures of merit for pesticide residue analysis are shown. The flowing sample under study is set in one arm of a Mach-Zehnder interferometer, and its refractive index is modulated by a periodically chopped continuous wave argon ion laser. As chopper, an acousto optical modulator has been introduced to switch the excitation laser beam between different lines (457 nm, 488 nm, 514 nm) simultaneously. Thus a multi component analysis can be realized either by using an HPLC-system in front of the PIS device or by a multi line Ar(+)-laser, directly. The limit of detection of the HPLC/PIS system reached 71 microg/l of the pesticide di-nitro-ortho-cresol (DNOC).
Effect of Low-Level Laser Therapy and Strength Training Protocol on Hand Grip by Dynamometry

PubMed Central

Barbosa, Rafael; Marcolino, Alexandre; Souza, Vitor; Bertolino, Guilherme; Fonseca, Marisa; Guirro, Rinaldo

2017-01-01

Introduction: The purpose of this study was to investigate the effect of low-level laser therapy (LLLT) – 660 nm and 904 nm - before grip strength protocol in healthy subjects. Methods: The study included 45 healthy volunteers with an average age of 22.7 (±1.4) years, subdivided into the following groups, control group: grip strength training associated with placebo LLLT; 660 nm group: LLLT (660 nm, 20 J/cm2, power of 30 mW, and beam area of 0.06 cm2, continuous, energy 1.2 J, and exposure time 40 seconds per point) before grip strength training and 904 nm group: LLLT (904 nm, 10 J/cm2, peak power of 70 W and 0.13 cm2 beam area, with pulsed beam 9.500 Hz and 30 seconds of exposure time per point and emitted energy 1.2 J) before grip strength training. The LLLT was timed to contact 10 points located in the region of the superficial and deep flexor muscles of the fingers, with a total energy of 12.0 J per session. For the strength training protocol, the volunteer exercised their fingers with the dominant hand on a small table, elbow flexed at 90°, forearm in neutral, using a light extension handle. The Oxford protocol was performed during four weeks. The grip strength was assessed using a dynamometer (Jamar™). The data were evaluated by the analysis of variance (ANOVA) statistical method. Results: In the comparison of intragroup evaluation, only the 904 nm group showed a difference compared to the baseline assessment after 4 weeks (P < 0.05), in the final intergroup evaluation, a difference was observed in the comparison between the control and 904 nm groups Conclusion: In conclusion, LLLT (904 nm) applied before resistance training was effective in gaining grip strength when compared to LLLT (660 nm) and isolated strength training after 4 weeks. PMID:29123629
Compact single-pass X-ray FEL with harmonic multiplication cascades

NASA Astrophysics Data System (ADS)

Zhukovsky, K.

2018-07-01

The generation of X-ray radiation in cascaded single-pass free electron laser (FEL), which amplifies high harmonics of a two-frequency undulator, is studied. Power dynamics of FEL harmonics is explored with the help of the phenomenological model of a single pass FEL. The model describes both linear and non-linear harmonic generation, starting from a coherent seed laser and initial shot noise with account for main loss factors for each harmonic in each cascade individually: the energy spread and beam divergence, the coupling losses between FEL cascades, the diffraction etc. The model was validated with the experiment and with relevant 3-D simulations. It is employed for modeling the cascaded FELs with harmonic multiplication and analyzing the evolution of FEL harmonic power with the aim to obtain the maximum high harmonic power in the X-ray band at the shortest possible FEL length with the lowest possible seed frequency. The advantages of two-frequency undulators in HGHG FELs are elucidated. The requirements for the electron beam are studied; the need for low energy spread is evidenced: our evaluations yield σe < 2 × 10-4. Several cascaded HGHG FELs with two-frequency undulators are modeled. Generation of soft X-ray radiation at λ = 2 . 71 nm, reaching ∼50 MW power with I0 ∼ 100 A in a cascaded FEL at just 40 m with 13.51 nm seed, matching peak reflectivity of Mo/Si, is demonstrated. The generation of 40 MW radiation power at λ = 2 . 27 nm with the beam current I0 ∼ 100 A, energy E = 950 MeV and the energy spread σe = 2 × 10-4 is studied, using second and third harmonics in three-stage 45 m long FEL. The multistage FEL is modeled for generating radiation in nanometer band: ∼40 MW power at λ ∼ 2 . 6 nm with I0 ∼ 175 A current in just ∼40 m long FEL with commercially available F2 excimer UV laser seed at 157 nm. The peak radiation power rises to ∼0.5 GW for ∼1 kA beam current.
Ideal laser-beam propagation through high-temperature ignition Hohlraum plasmas.

PubMed

Froula, D H; Divol, L; Meezan, N B; Dixit, S; Moody, J D; Neumayer, P; Pollock, B B; Ross, J S; Glenzer, S H

2007-02-23

We demonstrate that a blue (3omega, 351 nm) laser beam with an intensity of 2 x 10(15) W cm(-2) propagates nearly within the original beam cone through a millimeter scale, T(e)=3.5 keV high density (n(e)=5 x 10(20) cm(-3)) plasma. The beam produced less than 1% total backscatter at these high temperatures and densities; the resulting transmission is greater than 90%. Scaling of the electron temperature in the plasma shows that the plasma becomes transparent for uniform electron temperatures above 3 keV. These results are consistent with linear theory thresholds for both filamentation and backscatter instabilities inferred from detailed hydrodynamic simulations. This provides a strong justification for current inertial confinement fusion designs to remain below these thresholds.
Spectroscopic study of carbon plasma produced by the first (1064 nm) and second (532 nm) harmonics of Nd:YAG laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanif, M., E-mail: drhanif-mcs@nust.edu.pk; Salik, M.; Arif, F.

2015-03-15

In this research work, spectroscopic studies of carbon (C) plasma by using laser-induced breakdown spectroscopy (LIBS) are presented. The plasma was produced by the first (1064 nm) and second (532 nm) harmonics of a Q-switched Nd:YAG (Quantel Brilliant) pulsed laser having a pulse duration of 5 ns and 10-Hz repetition rate, which is capable of delivering 400 mJ at 1064 nm and 200 mJ at 532 nm. The laser beam was focused on the target material (100% carbon) by placing it in air at atmospheric pressure. The experimentally observed line profiles of five neutral carbon (C I) lines at 247.85,more » 394.22, 396.14, 588.95, and 591.25 nm were used to extract the electron temperature T{sub e} by using the Boltzmann plot method and determine its value, 9880 and 9400 K, respectively, for the fundamental and second harmonics of the laser, whereas the electron density N{sub e} was determined from the Stark broadening profile of neutral carbon line at 247.85 nm. The values of N{sub e} at a distance of 0.05 mm from the target surface for the fundamental-harmonic laser with a pulse energy of 130 mJ and the second-harmonic laser with a pulse energy of 72 mJ are 4.68 × 10{sup 17} and 5.98 × 10{sup 17} cm{sup −3}, respectively. This extracted information on T{sub e} and N{sub e} is useful for the deposition of carbon thin films by using the pulsed laser deposition technique. Moreover, both plasma parameters (T{sub e} and N{sub e}) were also calculated by varying the distance from the target surface along the line of propagation of the plasma plume and also by varying the laser irradiance.« less
Three-beam aerosol backscatter correlation lidar for wind profiling

NASA Astrophysics Data System (ADS)

Prasad, Narasimha S.; Radhakrishnan Mylapore, Anand

2017-03-01

The development of a three-beam aerosol backscatter correlation (ABC) light detection and ranging (lidar) to measure wind characteristics for wake vortex and plume tracking applications is discussed. This is a direct detection elastic lidar that uses three laser transceivers, operating at 1030-nm wavelength with ˜10-kHz pulse repetition frequency and nanosec class pulse widths, to directly obtain three components of wind velocities. By tracking the motion of aerosol structures along and between three near-parallel laser beams, three-component wind speed profiles along the field-of-view of laser beams are obtained. With three 8-in. transceiver modules, placed in a near-parallel configuration on a two-axis pan-tilt scanner, the lidar measures wind speeds up to 2 km away. Optical flow algorithms have been adapted to obtain the movement of aerosol structures between the beams. Aerosol density fluctuations are cross-correlated between successive scans to obtain the displacements of the aerosol features along the three axes. Using the range resolved elastic backscatter data from each laser beam, which is scanned over the volume of interest, a three-dimensional map of aerosol density can be generated in a short time span. The performance of the ABC wind lidar prototype, validated using sonic anemometer measurements, is discussed.
PCF based high power narrow line width pulsed fiber laser

NASA Astrophysics Data System (ADS)

Chen, H.; Yan, P.; Xiao, Q.; Wang, Y.; Gong, M.

2012-09-01

Based on semiconductor diode seeded multi-stage cascaded fiber amplifiers, we have obtained 88-W average power of a 1063-nm laser with high repetition rate of up to 1.5 MHz and a constant 2-ns pulse duration. No stimulated Brillouin scattering pulse or optical damage occurred although the maximum pulse peak power has exceeded 112 kW. The output laser exhibits excellent beam quality (M2x = 1.24 and M2y = 1.18), associated with a spectral line width as narrow as 0.065 nm (FWHM). Additionally, we demonstrate high polarization extinction ratio of 18.4 dB and good pulse stabilities superior to 1.6 % (RMS).
Effects of laser fluence non-uniformity on ambient-temperature soot measurements using the auto-compensating laser-induced incandescence technique

NASA Astrophysics Data System (ADS)

Liu, Fengshan; Rogak, Steven; Snelling, David R.; Saffaripour, Meghdad; Thomson, Kevin A.; Smallwood, Gregory J.

2016-11-01

Multimode pulsed Nd:YAG lasers are commonly used in auto-compensating laser-induced incandescence (AC-LII) measurements of soot in flames and engine exhaust as well as black carbon in the atmosphere. Such lasers possess a certain degree of fluence non-uniformity across the laser beam even with the use of beam shaping optics. Recent research showed that the measured volume fraction of ambient-temperature soot using AC-LII increases significantly, by about a factor of 5-8, with increasing the laser fluence in the low-fluence regime from a very low fluence to a relatively high fluence of near sublimation. The causes of this so-called soot volume fraction anomaly are currently not understood. The effects of laser fluence non-uniformity on the measured soot volume fraction using AC-LII were investigated. Three sets of LII experiments were conducted in the exhaust of a MiniCAST soot generator under conditions of high elemental carbon using Nd:YAG lasers operated at 1064 nm. The laser beams were shaped and relay imaged to achieve a relatively uniform fluence distribution in the measurement volume. To further homogenize the laser fluence, one set of LII experiments was conducted by using a diffractive optical element. The measured soot volume fractions in all three sets of LII experiments increase strongly with increasing the laser fluence before a peak value is reached and then start to decrease at higher fluences. Numerical calculations were conducted using the experimental laser fluence histograms. Laser fluence non-uniformity is found partially responsible for the soot volume fraction anomaly, but is insufficient to explain the degree of soot volume fraction anomaly observed experimentally. Representing the laser fluence variations by a histogram derived from high-resolution images of the laser beam energy profile gives a more accurate definition of inhomogeneity than a simple averaged linear profile across the laser beam.
Estimating the pressure of laser-induced plasma shockwave by stimulated Raman shift of lattice translational modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Zhanlong; College of Physics, Jilin University, Changchun 130012; Shan Xiaoning

2012-07-09

The current paper investigates stimulated Raman scattering (SRS) when laser-induced plasma is formed in heavy water by focusing an intense pulsed 532 nm Nd:YAG laser beam at room temperature. An unexpected low-frequency SRS line attributed to the lattice translational modes of ice-VII (D{sub 2}O) is observed. The pressure of the plasma shockwave is estimated using low-frequency SRS line shift.

Femtosecond OPO based on MgO:PPLN synchronously pumped by a 532 nm fiber laser

NASA Astrophysics Data System (ADS)

Cao, Jianjun; Shen, Dongyi; Zheng, Yuanlin; Feng, Yaming; Kong, Yan; Wan, Wenjie

2017-05-01

With the rapid progress in fiber technologies, femtosecond fiber lasers, which are compact, cost-effective and stable, have been developed and are commercially available. Studies of optical parametric oscillators (OPOs) pumped by this type of laser are demanding. Here we report a femtosecond optical parametric oscillator (OPO) at 79.6 MHz repetition rate based on MgO-doped periodically poled LiNbO3 (MgO:PPLN), synchronously pumped by the integrated second harmonic radiation of a femtosecond fiber laser at 532 nm. The signal delivered by the single resonant OPO is continuously tunable from 757 to 797 nm by tuning the crystal temperature in a poling period of 7.7 μ \\text{m} . The output signal shows good beam quality in TEM00 mode profile with pulse duration of 206 fs at 771 nm. Maximum output signal power of 71 mW is obtained for a pump power of 763 mW and a low pumping threshold of 210 mW is measured. Moreover, grating tuning and cavity length tuning of the signal wavelength are also investigated.
Design and Operation of a Two-Color Interferometer to Measure Plasma and Neutral Gas Densities in a Laser-Triggered Spark Gap Switch

NASA Astrophysics Data System (ADS)

Camacho, J. F.; Ruden, E. L.; Domonkos, M. T.; Schmitt-Sody, A.; Lucero, A.

2014-10-01

A Mach-Zehnder imaging interferometer, operating with 1064-nm and 532-nm wavelength beams from a short-pulse laser and a frequency-doubled branch, respectively, has been designed and built to simultaneously measure plasma free electron and neutral gas densities profiles within a laser-triggered spark gap switch with a 5-mm gap. The switch will be triggered by focusing a separate 532-nm or 1064-nm laser pulse along the gap's axis to trigger low-jitter breakdown. Illuminating the gap transverse to this axis, the diagnostic will generate interferograms for each wavelength, which will then be numerically converted to phase-shift maps. These will be used to calculate independent line-integrated free electron and neutral density profiles by exploiting their different frequency dispersion curves. The density profiles themselves, then, will be calculated by Abel inversion. Details of the interferometer's design will be presented along with density data obtained using a variety of fill gasses at various pressures. Other switch parameters will be varied as well in order to characterize more fully the performance of the switch.
Pulse length of ultracold electron bunches extracted from a laser cooled gas

PubMed Central

Franssen, J. G. H.; Frankort, T. L. I.; Vredenbregt, E. J. D.; Luiten, O. J.

2017-01-01

We present measurements of the pulse length of ultracold electron bunches generated by near-threshold two-photon photoionization of a laser-cooled gas. The pulse length has been measured using a resonant 3 GHz deflecting cavity in TM110 mode. We have measured the pulse length in three ionization regimes. The first is direct two-photon photoionization using only a 480 nm femtosecond laser pulse, which results in short (∼15 ps) but hot (∼104 K) electron bunches. The second regime is just-above-threshold femtosecond photoionization employing the combination of a continuous-wave 780 nm excitation laser and a tunable 480 nm femtosecond ionization laser which results in both ultracold (∼10 K) and ultrafast (∼25 ps) electron bunches. These pulses typically contain ∼103 electrons and have a root-mean-square normalized transverse beam emittance of 1.5 ± 0.1 nm rad. The measured pulse lengths are limited by the energy spread associated with the longitudinal size of the ionization volume, as expected. The third regime is just-below-threshold ionization which produces Rydberg states which slowly ionize on microsecond time scales. PMID:28396879
Diode-pumped DUV cw all-solid-state laser to replace argon ion lasers

NASA Astrophysics Data System (ADS)

Zanger, Ekhard; Liu, B.; Gries, Wolfgang

2000-04-01

The slim series DELTATRAINTM-worldwide the first integrated cw diode-pumped all-solid-state DUV laser at 266 nm with a compact, slim design-has been developed. The slim design minimizes the DUV DPSSL footprint and thus greatly facilitates the replacement of commonly used gas ion lasers, including these with intra-cavity frequency doubling, in numerous industrial and scientific applications. Such a replacement will result in an operation cost reduction by several thousands US$DLR each year for one unit. Owing to its unique geometry-invariant frequency doubling cavity- based on the LAS patent-pending DeltaConcept architecture- this DUV laser provides excellent beam-pointing stability of <2 (mu) rad/ degree(s)C and power stability of <2%. The newest design of the cavity block has adopted a cemented resonator with each component positioned precisely inside a compact monolithic metal block. The automatic and precise crystal shifter ensures long operation lifetime of > 5000 hours of whole 266 nm laser. The microprocessor controlled power supply provides an automatic control of the whole 266 nm laser, making this DUV laser a hands-off system which can meet tough requirements posed by numerous industrial and scientific applications. It will replace the commonplace ion laser as the future DUV laser of choice.
Laser Truss Sensor for Segmented Telescope Phasing

NASA Technical Reports Server (NTRS)

Liu, Duncan T.; Lay, Oliver P.; Azizi, Alireza; Erlig, Herman; Dorsky, Leonard I.; Asbury, Cheryl G.; Zhao, Feng

2011-01-01

A paper describes the laser truss sensor (LTS) for detecting piston motion between two adjacent telescope segment edges. LTS is formed by two point-to-point laser metrology gauges in a crossed geometry. A high-resolution (<30 nm) LTS can be implemented with existing laser metrology gauges. The distance change between the reference plane and the target plane is measured as a function of the phase change between the reference and target beams. To ease the bandwidth requirements for phase detection electronics (or phase meter), homodyne or heterodyne detection techniques have been used. The phase of the target beam also changes with the refractive index of air, which changes with the air pressure, temperature, and humidity. This error can be minimized by enclosing the metrology beams in baffles. For longer-term (weeks) tracking at the micron level accuracy, the same gauge can be operated in the absolute metrology mode with an accuracy of microns; to implement absolute metrology, two laser frequencies will be used on the same gauge. Absolute metrology using heterodyne laser gauges is a demonstrated technology. Complexity of laser source fiber distribution can be optimized using the range-gated metrology (RGM) approach.
Curved grating fabrication techniques for concentric-circle grating, surface-emitting semiconductor lasers

NASA Technical Reports Server (NTRS)

Jordan, Rebecca H.; King, Oliver; Wicks, Gary W.; Hall, Dennis G.; Anderson, Erik H.; Rooks, Michael J.

1993-01-01

We describe the fabrication and operational characteristics of a novel, surface-emitting semiconductor laser that makes use of a concentric-circle grating to both define its resonant cavity and to provide surface emission. A properly fabricated circular grating causes the laser to operate in radially inward- and outward-going circular waves in the waveguide, thus, introducing the circular symmetry needed for the laser to emit a beam with a circular cross-section. The basic circular-grating-resonator concept can be implemented in any materials system; an AlGaAs/GaAs graded-index, separate confinement heterostructure (GRINSCH), single-quantum-well (SQW) semiconductor laser, grown by molecular beam epitaxy (MBE), was used for the experiments discussed here. Each concentric-circle grating was fabricated on the surface of the AlGaAs/GaAs semiconductor laser. The circular pattern was first defined by electron-beam (e-beam) lithography in a layer of polymethylmethacrylate (PMMA) and subsequently etched into the semiconductor surface using chemically-assisted (chlorine) ion-beam etching (CAIBE). We consider issues that affect the fabrication and quality of the gratings. These issues include grating design requirements, data representation of the grating pattern, and e-beam scan method. We provide examples of how these techniques can be implemented and their impact on the resulting laser performance. A comparison is made of the results obtained using two fundamentally different electron-beam writing systems. Circular gratings with period lambda = 0.25 microns and overall diameters ranging from 80 microns to 500 microns were fabricated. We also report our successful demonstration of an optically pumped, concentric-circle grating, semiconductor laser that emits a beam with a far-field divergence angle that is less than one degree. The emission spectrum is quite narrow (less than 0.1 nm) and is centered at wavelength lambda = 0.8175 microns.
InP-based three-dimensional photonic integrated circuits

NASA Astrophysics Data System (ADS)

Tsou, Diana; Zaytsev, Sergey; Pauchard, Alexandre; Hummel, Steve; Lo, Yu-Hwa

2001-10-01

Fast-growing internet traffic volumes require high data communication bandwidth over longer distances than short wavelength (850 nm) multi-mode fiber systems can provide. 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 and 1550 nm wavelengths are required. The great success of GaAs 850 nm 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 available intrinsic 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, 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 (PICs) 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 for fabricating InP-based photonic integrated circuits compatible with surface-emitting laser technology. Employing InP transparency at 1310 and 1550 nm wavelengths, we have created 3-D photonic integrated circuits (PICs) by utilizing light beams in both surface normal and in-plane directions within the InP-based structure. This additional beam routing flexibility allows significant size reduction and process simplification without sacrificing device performance. This innovative 3-D PIC technology platform can be easily extended to create surface-emitting lasers integrated with power monitoring detectors, micro-lenses, external modulators, amplifiers, and other passive and active components. Such added functionality can produce cost--effective solutions for the highest-end laser transmitters required for datacom and short range telecom networks, as well as fiber channels and other cost and performance sensitive applications. We present results for 1310 nm photonic IC surface-emitting laser transmitters operating at 2.5 Gbps without active thermal electric cooling.
Packaging of wavelength stabilized 976nm 100W 105µm 0.15 NA fiber coupled diode lasers

NASA Astrophysics Data System (ADS)

Jiang, Xiaochen; Liu, Rui; Gao, Yanyan; Zhang, Tujia; He, Xiaoguang; Zhu, Jing; Zhang, Qiang; Yang, Thomas; Zhang, Cuipeng

2016-03-01

Fiber coupled diode lasers are widely used in many fields now especially as pumps in fiber laser systems. In many fiber laser applications, high brightness pumps are essential to achieve high brightness fiber lasers. Furthermore, 976nm wavelength absorption band is narrow with Yb3+ doped fiber lasers which is more challenging for controlling wavelength stabilized in diode laser modules. This study designed and implemented commercial available high brightness and narrow wavelength width lasers to be able to use in previous mentioned applications. Base on multiple single emitters using spatial and polarization beam combining as well as fiber coupling techniques, we report a wavelength stabilized, 105μm NA 0.15 fiber coupled diode laser package with 100W of optical output power at 976 nm, which are 14 emitters inside each multiple single emitter module. The emitting aperture of the combined lasers output are designed and optimized for coupling light into a 105μm core NA 0.15 fiber. Volume Bragg grating technology has been used to improve spectral characteristics of high-power diode lasers. Mechanical modular design and thermal simulation are carried out to optimize the package. The spectral width is roughly 0.5 nm (FWHM) and the wavelength shift per °C < 0.02nm. The output spectrum is narrowed and wavelength is stabilized using Volume Bragg gratings (VBGs). The high brightness package has an electrical to optical efficiency better than 45% and power enclosure more than 90% within NA 0.12. Qualification tests have been included on this kind of package. Mechanical shock, vibration and accelerated aging tests show that the package is reliability and the MTTF is calculated to be more than 100k hours at 25°C.
Diode-pumped continuous wave and passively Q-switched Tm, Mg: LiTaO₃ lasers.

PubMed

Feng, T; Li, T; Zhao, S; Li, Q; Yang, K; Zhao, J; Qiao, W; Hang, Y; Zhang, P; Wang, Y; Xu, J

2014-02-24

We have demonstrated the continuous wave and passively Q-switched Tm, Mg: LiTaO3 lasers for the first time. In continuous wave (CW) regime, a maximum CW output power of 1.03 W at 1952 nm was obtained, giving a slope efficiency of 9.5% and a beam quality M2 = 2.2. In passive Q-switching regime, a single walled carbon nanotube (SWCNT) was employed as saturable absorber (SA). The Tm,Mg:LiTaO3 laser has yielded a pulse of 560 ns under repetition rate of 34.2 kHz at 1926 nm, corresponding to a single pulse energy of 10.1 μJ. The results indicate a promising potential of nonlinear crystals in the applications for laser host materials.
High-power operation of highly reliable narrow stripe pseudomorphic single quantum well lasers emitting at 980 nm

NASA Technical Reports Server (NTRS)

Larsson, A.; Forouhar, S.; Cody, J.; Lang, R. J.

1990-01-01

Ridge waveguide pseudomorphic InGaAs/GaAs/AlGaAs single-quantum-well lasers exhibiting record high quantum efficiencies and high output power densities (105 mW per facet from a 6 micron wide stripe) at a lasing wavelength of 980 nm are discussed that were fabricated from a graded index separate confinement heterostructure grown by molecular beam epitaxy. Life testing at an output power of 30 mW per uncoated facet reveals a slow gradual degradation during the initial 500 h of operation after which the operating characteristics of the lasers become stable. The emission wavelength, the high output power, and the fundamental lateral mode operation render these lasers suitable for pumping Er3+-doped fiber amplifiers.
Narrow linewidth picosecond UV pulsed laser with mega-watt peak power.

PubMed

Huang, Chunning; Deibele, Craig; Liu, Yun

2013-04-08

We demonstrate a master oscillator power amplifier (MOPA) burst mode laser system that generates 66 ps/402.5 MHz pulses with mega-watt peak power at 355 nm. The seed laser consists of a single frequency fiber laser (linewidth < 5 KHz), a high bandwidth electro-optic modulator (EOM), a picosecond pulse generator, and a fiber based preamplifier. A very high extinction ratio (45 dB) has been achieved by using an adaptive bias control of the EOM. The multi-stage Nd:YAG amplifier system allows a uniformly temporal shaping of the macropulse with a tunable pulse duration. The light output from the amplifier is converted to 355 nm, and over 1 MW peak power is obtained when the laser is operating in a 5-μs/10-Hz macropulse mode. The laser output has a transform-limited spectrum with a very narrow linewidth of individual longitudinal modes. The immediate application of the laser system is the laser-assisted hydrogen ion beam stripping for the Spallation Neutron Source (SNS).
Beam quality improvement by population-dynamic-coupled combined guiding effect in end-pumped Nd:YVO4 laser oscillator

NASA Astrophysics Data System (ADS)

Shen, Yijie; Gong, Mali; Fu, Xing

2018-05-01

Beam quality improvement with pump power increasing in an end-pumped laser oscillator is experimentally realized for the first time, to the best of our knowledge. The phenomenon is caused by the population-dynamic-coupled combined guiding effect, a comprehensive theoretical model of which has been well established, in agreement with the experimental results. Based on an 888 nm in-band dual-end-pumped oscillator using four tandem Nd:YVO4 crystals, the output beam quality of M^2= 1.1/1.1 at the pump power of 25 W is degraded to M^2 = 2.5/1.8 at 75 W pumping and then improved to M^2= 1.8/1.3 at 150 W pumping. The near-TEM_{00} mode is obtained with the highest continuous-wave output power of 72.1 W and the optical-to-optical efficiency of 48.1%. This work demonstrates great potential to further scale the output power of end-pumped laser oscillator while keeping good beam quality.
Three-beam coherent combination experiments based on segmented mirrors and measure of phase characteristics of beams passing through Yb-doped fiber amplifier

NASA Astrophysics Data System (ADS)

Yang, Ping; Yang, Ruo fu; Shen, Feng; Ao, Mingwu; Jiang, Wenhan

2009-05-01

Coherent combination is one of the most promising ways to realize high power laser output. A three- laser-beam coherent combination system based on adaptive optics (AO) technique has been set up in our laboratory. In this system, three 1064nm laser beams are placed side-by-side and compressed by two reflective mirrors. An active segmented deformable mirror (DM) is used to compensate the optical path difference (OPD) among three laser beams. The beams are overlapped onto a 2900Hz CCD camera to form an interference pattern while the peak intensity of the interference pattern is taken as the cost function to optimize by a stochastic parallel gradient descent (SPGD) algorithm. SPGD algorithm is realized on a RT-Linux dual-core industrial computer. A series of experiments have been accomplished and experimental results show that both static distorted aberrations in the beams and active distorted aberrations (which are brought in by a hot iron and the frequency is about 5Hz) can be compensated successfully when the gain coefficients and the perturbation amplitude of SPGD are chosed appropriately, thereby three beams can be well combined. For controlling the phase of fiber lasers, the phase characteristics of beams passing through Yb-doped dual-clad fiber amplifier are measured by means of investigating the interference pattern under different output power through experiments. The frequency of phase fluctuation is evaluated through analyzing the fluctuation of power within a 90um aperture of far-field focal spot. Experimental results show that the phase fluctuation frequencies of laser beam transmitted through fiber amplifier are mainly in the range of 100~1500Hz. As a result, to control the phase fluctuation of beams passing through fiber amplifier, the bandwidth of any potential phase control scheme must be greater than 1.5 kilohertz.
Kilohertz Pulse Repetition Frequency Slab Ti:sapphire Lasers with High Average Power (10 W)

NASA Astrophysics Data System (ADS)

Wadsworth, William J.; Coutts, David W.; Webb, Colin E.

1999-11-01

High-average-power broadband 780-nm slab Ti:sapphire lasers, pumped by a kilohertz pulse repetition frequency copper vapor laser (CVL), were demonstrated. These lasers are designed for damage-free power scaling when pumped by CVL s configured for maximum output power (of order 100 W) but with poor beam quality ( M 2 300 ). A simple Brewster-angled slab laser side pumped by a CVL produced 10-W average power (1.25-mJ pulses at 8 kHz) with 4.2-ns FWHM pulse duration at an absolute efficiency of 15% (68-W pump power). Thermal lensing in the Brewster slab laser resulted in multitransverse mode output, and pump absorption was limited to 72% by the maximum doping level for commercially available Ti:sapphire (0.25%). A slab laser with a multiply folded zigzag path was therefore designed and implemented that produced high-beam-quality (TEM 00 -mode) output when operated with cryogenic cooling and provided a longer absorption path for the pump. Excessive scattering of the Ti:sapphire beam at the crystal surfaces limited the efficiency of operation for the zigzag laser, but fluorescence diagnostic techniques, gain measurement, and modeling suggest that efficient power extraction ( 15 W TEM 00 , 23% efficiency) from this laser would be possible for crystals with an optical quality surface polish.
Computer simulation of photorefractive keratectomy for the correction of myopia and hyperopia

NASA Astrophysics Data System (ADS)

Pinault, Pascal; 'Huillier, J. P.

1996-01-01

Photorefractive keratectomy (PRK) performed by means of the 193 nm excimer laser has stimulated considerable interest in the ophthalmic community because this new procedure has the potential to correct myopia, hyperopia, and astigmatism. The use of a laser beam to remove a controlled amount of tissue from the cornea implies that both the energy density of the laser beam and the target removed rate are accurately known. In addition, the required tissue ablation profile to achieve refractive correction must be predicted by optical calculations. This paper investigates: (1) Optical computations based on raytracing model to determine what anterior profile of cornea is needed postoperatively for ametropia. (2) Maximal depth of the removed corneal tissue against the ablation zone treated. And (3) the thickness of ablated corneal lenticule at any distance from the optical axis. Relationships between these data are well fitted by polynomial regressive curves in order to be useful as an algorithm in the computer-controlled delivery of the ArF laser beam.
Advances in generation of high-repetition-rate burst mode laser output.

PubMed

Jiang, Naibo; Webster, Matthew C; Lempert, Walter R

2009-02-01

It is demonstrated that the incorporation of variable pulse duration flashlamp power supplies into an Nd:YAG burst mode laser system results in very substantial increases in the realizable energy per pulse, the total pulse train length, and uniformity of the intensity envelope. As an example, trains of 20 pulses at burst frequencies of 50 and 20 kHz are demonstrated with individual pulse energy at 1064 nm of 220 and 400 mJ, respectively. Conversion efficiency to the second- (532 nm) and third- (355 nm) harmonic wavelengths of approximately 50% and 35-40%, respectively, is also achieved. Use of the third-harmonic output of the burst mode laser as a pump source for a simple, home built optical parametric oscillator (OPO) produces pulse trains of broadly wavelength tunable output. Sum-frequency mixing of OPO signal output at 622 nm with residual output from the 355 nm pump beam is shown to produce uniform bursts of tunable output at approximately 226 nm, with individual pulse energy of approximately 0.5 mJ. Time-correlated NO planar laser induced fluorescence (PLIF) image sequences are obtained in a Mach 3 wind tunnel at 500 kHz, representing, to our knowledge, the first demonstration of NO PLIF imaging at repetition rates exceeding tens of hertz.
How safe is gamete micromanipulation by laser tweezers?

NASA Astrophysics Data System (ADS)

Koenig, Karsten; Tromberg, Bruce J.; Tadir, Yona; Berns, Michael W.

1998-04-01

Laser tweezers, used as novel sterile micromanipulation tools of living cells, are employed in laser-assisted in vitro fertilization (IVF). For example, controlled spermatozoa transport with 1064 nm tweezers to human egg cells has been performed in European clinics in cases of male infertility. The interaction of approximately 100 mW near infrared (NIR) trapping beams at MW/cm2 intensity with human gametes results in low mean less than 2 K temperature increases and less than 100 pN trapping forces. Therefore, photothermal or photomechanical induced destructive effects appear unlikely. However, the high photon flux densities may induce simultaneous absorption of two NIR photons resulting in nonlinear interactions. These nonlinear interactions imply non-resonant two-photon excitation of endogenous cellular chromophores. In the case of less than 800 nm tweezers, UV- like damage effects may occur. The destructive effect is amplified when multimode cw lasers are used as tweezer sources due to longitudinal mode-beating effects and partial mode- locking. Spermatozoa damage within seconds using 760 nm traps due to formation of unstable ps pulses in a cw Ti:Sa ring laser is demonstrated. We recommend the use of greater than or equal to 800 nm traps for optical gamete micromanipulation. To our opinion, further basic studies on the influence of nonlinear effects of laser tweezers on human gamete are necessary.
Pros and cons of characterising an optical translocation setup

NASA Astrophysics Data System (ADS)

Maphanga, Charles; Malabi, Rudzani; Ombinda-Lemboumba, Saturnin; Maaza, Malik; Mthunzi-Kufa, Patience

2017-02-01

The delivery of genetic material and drugs into mammalian cells using femtosecond (fs) laser pulses is escalating rapidly. This novel light based technique achieved through a precise focusing of a laser beam on the plasma membrane is called photoporation. This technique is attained using ultrashort laser pulses to irradiate plasma membrane of mammalian cells, thus resulting in the accumulation of a vast amount of free electrons. These generated electrons react photochemically with the cell membrane, resulting in the generation of sub-microscopic pores on the cell membrane enabling a variety of extracellular media to diffuse into the cell. This study is aimed at critically analysing the "do's and don'ts" of designing, assembling, and characterising an optical translocation setup using a femtosecond legend titanium sapphire regenerative amplifier pulsed laser (Gaussian beam, 800 nm, 1 kHz, 113 fs, and an output power of 850 mW). The main objective in our study is to determine optical phototranslocation parameters which are compatible to the plasma membrane and cell viability. Such parameters included beam profiling, testing a range of laser fluencies suitable for photoporation, assessment of the beam quality and laser-cell interaction time. In our study, Chinese Hamster Ovary-K1 (CHO-K1) cells were photoporated in the presence of trypan blue to determine optimal parameters for photoporation experiment. An average power of 4.5 μW, exposure time of 7 ms, with a laser beam spot of 1.1 μm diameter at the focus worked optimally without any sign of cell stress and cytoplasmic bleeding. Cellular responses post laser treatment were analysed using cell morphology studies.
Performance Considerations for the SIMPL Single Photon, Polarimetric, Two-Color Laser Altimeter as Applied to Measurements of Forest Canopy Structure and Composition

NASA Technical Reports Server (NTRS)

Dabney, Philip W.; Harding, David J.; Valett, Susan R.; Vasilyev, Aleksey A.; Yu, Anthony W.

2012-01-01

The Slope Imaging Multi-polarization Photon-counting Lidar (SIMPL) is a multi-beam, micropulse airborne laser altimeter that acquires active and passive polarimetric optical remote sensing measurements at visible and near-infrared wavelengths. SIMPL was developed to demonstrate advanced measurement approaches of potential benefit for improved, more efficient spaceflight laser altimeter missions. SIMPL data have been acquired for wide diversity of forest types in the summers of 2010 and 2011 in order to assess the potential of its novel capabilities for characterization of vegetation structure and composition. On each of its four beams SIMPL provides highly-resolved measurements of forest canopy structure by detecting single-photons with 15 cm ranging precision using a narrow-beam system operating at a laser repetition rate of 11 kHz. Associated with that ranging data SIMPL provides eight amplitude parameters per beam unlike the single amplitude provided by typical laser altimeters. Those eight parameters are received energy that is parallel and perpendicular to that of the plane-polarized transmit pulse at 532 nm (green) and 1064 nm (near IR), for both the active laser backscatter retro-reflectance and the passive solar bi-directional reflectance. This poster presentation will cover the instrument architecture and highlight the performance of the SIMPL instrument with examples taken from measurements for several sites with distinct canopy structures and compositions. Specific performance areas such as probability of detection, after pulsing, and dead time, will be highlighted and addressed, along with examples of their impact on the measurements and how they limit the ability to accurately model and recover the canopy properties. To assess the sensitivity of SIMPL's measurements to canopy properties an instrument model has been implemented in the FLIGHT radiative transfer code, based on Monte Carlo simulation of photon transport. SIMPL data collected in 2010 over the Smithsonian Environmental Research Center, MD are currently being modelled and compared to other remote sensing and in situ data sets. Results on the adaptation of FLIGHT to model micropulse, single'photon ranging measurements are presented elsewhere at this conference. NASA's ICESat-2 spaceflight mission, scheduled for launch in 2016, will utilize a multi-beam, micropulse, single-photon ranging measurement approach (although non-polarimetric and only at 532 nm). Insights gained from the analysis and modelling of SIMPL data will help guide preparations for that mission, including development of calibration/validation plans and algorithms for the estimation of forest biophysical parameters.
Investigation into the optimum beam shape and fluence for selective ablation of dental calculus at lambda = 400 nm.

PubMed

Schoenly, Joshua E; Seka, Wolf; Rechmann, Peter

2010-01-01

A frequency-doubled Ti:sapphire laser is shown to selectively ablate dental calculus. The optimal transverse shape of the laser beam, including its variability under water-cooling, is determined for selective ablation of dental calculus. Intensity profiles under various water-cooling conditions were optically observed. The 400-nm laser was coupled into a multimode optical fiber using an f = 2.5-cm lens and light-shaping diffuser. Water-cooling was supplied coaxially around the fiber. Five human tooth samples (four with calculus and one pristine) were irradiated perpendicular to the tooth surface while the tooth was moved back and forth at 0.3 mm/second, varying between 20 and 180 iterations. The teeth were imaged before and after irradiation using light microscopy with a flashing blue light-emitting diode (LED). An environmental scanning electron microscope imaged each tooth after irradiation. High-order super-Gaussian intensity profiles are observed at the output of a fiber coiled around a 4-in. diameter drum. Super-Gaussian beams have a more-homogenous fluence distribution than Gaussian beams and have a higher energy efficiency for selective ablation. Coaxial water-cooling does not noticeably distort the intensity distribution within 1 mm from the optical fiber. In contrast, lasers focused to a Gaussian cross section (< or =50-microm diameter) without fiber propagation and cooled by a water spray are heavily distorted and may lead to variable ablation. Calculus is preferentially ablated at high fluences (> or =2 J/cm(2)); below this fluence, stalling occurs because of photo-bleaching of the calculus. Healthy dental hard tissue is not removed at fluences < or =3 J/cm(2). Supplying laser light to a tooth using an optical fiber with coaxial water-cooling is determined to be the most appropriate method when selectively removing calculus with a frequency-doubled Ti:sapphire laser. Fluences over 2 J/cm(2) are required to remove calculus efficiently since photo-bleaching stalls calculus removal below that value.

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