[1]红外动目标识别跟踪系统的dsp+fpga实现




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High-Power Laser and Solid-State Laser


171

Author(s): Pareek, R (Pareek, R.); Kumbhare, MN (Kumbhare, M. N.); Mukherjee, C (Mukherjee, C.)

Title: Effect of oil vapor contamination on the performance of porous silica sol-gel anti reflection-coated optics in vacuum spatial filters of high-power neodymium glass laser - art. no. 023801

Source: OPTICAL ENGINEERING, 47 (2): 23801-23801 FEB 2008

Abstract:

The effect of oil vapor contamination on sol-gel porous silica antireflection (AR) coatings deposited on optics used in vacuum spatial filters of high-power lasers is experimentally studied. The contamination results in the reduction of laser-induced damage threshold (LIDT) and the increase in reflectivity of the AR coatings. In comparison, the silica coatings treated with ammonia and hexamethyl-clisilazane (HMDS) show almost no increase of reflectivity, and their LIDT value reduces only marginally at the wavelength of laser operation. It is found that the decrease in LIDT of the coatings exposed to oil vapors occurs due to higher absorption of the laser light, as evidenced from the increase in the imaginary part of the refractive index of the coatings. (C) 2008 Society of Photo-Optical Instrumentation Engineers.


Addresses: Raja Ramanna Ctr Adv Technol, Laser Plasma Div, Indore 452013, India

Raja Ramanna Ctr Adv Technol, Laser Syst Engn Div, Indore 452013, India

Reprint Address: PAREEK, R, RAJA RAMANNA CTR ADV TECHNOL, LASER PLASMA DIV, INDORE 452013, INDIA

Author's E-mail: rpareek@cat.ernet.in

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172


Author(s): Tan, WS (Tan, W. S.); Kauer, M (Kauer, M.); Hooper, SE (Hooper, S. E.); Barnes, JM (Barnes, J. M.); Rossetti, M (Rossetti, M.); Smeeton, TM (Smeeton, T. M.); Bousquet, V (Bousquet, V.); Heffernan, J (Heffernan, J.)

Title: High-power and long-lifetime InGaN blue-violet laser diodes grown by molecular beam epitaxy

Source: ELECTRONICS LETTERS, 44 (5): 351-353 FEB 28 2008

Abstract:

InGaN 405 nm multiple quantum well laser diodes grown by molecular beam epitaxy (MBE) with a continuous-wave (CW) lifetime of Lip to 42 h are reported. The CW threshold current density of the ridge wave-guide laser diodes is 3.6 kA/cm(2) and the slope efficiency for uncoated facets is 0.42 W/A per facet with a maximum CW output power of 45 mW per facet. Statistical variation of CW lifetime with dissipated power is presented for MBE-grown laser diodes from five different wafers.
Addresses: Europe Ltd, Sharp Labs, Oxford OX4 4GB, England

Reprint Address: TAN, WS, EUROPE LTD, SHARP LABS, EDMUND HALLEY RD,OXFORD SCI PK, OXFORD OX4 4GB, ENGLAND

Author's E-mail: matthias.kauer@sharp.co.uk

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173

Author(s): Lai, HY (Lai, Hsin-Yi); Huang, PH (Huang, Pei-Hsing)



Title: Laser-irradiated thermodynamic behaviors of spallation and recombination at solid-state interface

Source: APPLIED SURFACE SCIENCE, 254 (10): 3067-3073 MAR 15 2008

Abstract:

A microscopic insight of interfacial spallation and recombination behaviors at multilayer thin-film interface induced by incident femtosecond pulsed laser is presented in this paper. Such two different aforementioned behaviors are investigated via the thermodynamic trajectories obtained by using standard Lennard-Jones (L-J) molecular dynamics (MD) simulation. Based on the simulation results, the interfacial damages of multilayer thin film are dominated by a critical threshold that induces an extraordinary expansive dynamics and phase transitions leading to the structural softened and tensile spallation at interface. The critical damage threshold is evaluated at around 8.5 J/m(2) which governs the possible occurrence of two different regimes, i.e. interfacial spallaiton and recombination. In interfacial damage region, quasi-isothermal thermodynamic trajectories can be observed after the interfacial spallation occurs. Moreover, the result of thermodynamic trajectories analyses indicates that, the relaxation of pressure wave may cause the over-heated interfacial zone to reduce volumetric density, thus leading to structural softness and even weaken interfacial structural strength. The crucial effect leading to the phenomenon of low tension spallation is identified. (C) 2007 Elsevier B.V. All rights reserved.


Addresses: Natl Cheng Kung Univ, Dept Mech Engn, Tainan 701, Taiwan

Reprint Address: LAI, HY, NATL CHENG KUNG UNIV, DEPT MECH ENGN, TAINAN 701, TAIWAN

Author's E-mail: hylai@mail.ncku.edu.tw

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174

Author(s): Schellhorn, M (Schellhorn, M.)



Title: High-power diode-pumped Tm : YLF laser

Source: APPLIED PHYSICS B-LASERS AND OPTICS, 91 (1): 71-74 APR 2008

Abstract:

A high-power, continuous-wave 3.5% Tm3+ doped LiYF4 (Tm:YLF) laser has been developed. Using two Tm:YLF rods in a single cavity, 55 W of laser output at 1910 nm was obtained with a slope efficiency of 49%. The M-2 factor was found to be < 3. With a single Tm:YLF rod, a maximum laser power of 30 W was obtained with a slope efficiency of 50%. The laser was tuned to the peak absorption wavelength of Ho:YAG of 1907.5 nm by an intracavity quartz etalon with an output power loss < 1 W.


Addresses: ISL, French German Res Inst, F-68301 St Louis, France

Reprint Address: SCHELLHORN, M, ISL, FRENCH GERMAN RES INST, 5 RUE GEN CASSAGNOU, F-68301 ST LOUIS, FRANCE

Author's E-mail: schellhorn@isl.tm.fr

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175

Author(s): Hu, XP (Hu, X. P.); Zhao, G (Zhao, G.); Yan, Z (Yan, Z.); Wang, X (Wang, X.); Gao, ZD (Gao, Z. D.); Liu, H (Liu, H.); He, JL (He, J. L.); Zhu, SN (Zhu, S. N.)



Title: High-power red-green-blue laser light source based on intermittent oscillating dual-wavelength Nd : YAG laser with a cascaded LiTaO3 superlattice

Source: OPTICS LETTERS, 33 (4): 408-410 FEB 15 2008

Abstract:

We demonstrate a high-power red-green-blue laser source based on the quasi-phase-matching and intermittent oscillating dual-wavelength laser technique. A cascaded LiTaO3 superlattice was used to achieve the generation of red light at 660 nm, green light at 532 nm, and blue light at 440 nm to obtain the output of red-green-blue laser light from a diode-side-pumped Q-switched intermittent oscillating dual-wavelength Nd:YAG laser. The average output power of red-green-blue of 1.01 W was achieved under the total fundamental power of 5.1 W, which corresponds to the conversion efficiency of 20%. (C) 2008 Optical Society of America.


Addresses: Nanjing Univ, Natl Lab Solid State Microstruct, Nanjing 210093, Peoples R China

Nanjing Univ, Dept Phys, Nanjing 210093, Peoples R China

Shandong Univ, Inst Crystal Mat, Jinan 250100, Peoples R China

Reprint Address: ZHU, SN, NANJING UNIV, NATL LAB SOLID STATE MICROSTRUCT, NANJING 210093, PEOPLES R CHINA

Author's E-mail: zhusn@nju.edu.cn

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176

Author(s): Yoh, JJ (Yoh, Jack J.); Lee, H (Lee, Hyunhee); Choi, J (Choi, Jihee); Lee, KC (Lee, Kyung-cheol); Kim, KH (Kim, Ki-hong)



Title: Ablation-induced explosion of metal using a high-power Nd : YAG laser - art. no. 043511

Source: JOURNAL OF APPLIED PHYSICS, 103 (4): 43511-43511 FEB 15 2008

Abstract:

The interaction of a high-power pulsed-laser beam with metal targets in air from a 1.06 mu m, 5 ns, 3 J/pulse, Nd:YAG pulsed laser is investigated together with hydrodynamic theories of laser-supported blast wave and multimaterial reactive Euler equations., The high-speed blast wave generated by the laser ablation of metal reaches a maximum velocity of several thousand meters per second. The apparently similar flow conditions to those of reactive shock wave allow one to apply the equations,of motion for energetic materials and to understand the explosive behavior of metal vaporization upon laser ablation. The characteristic time at which the planar to spherical wave transition occurs is investigated at low (20 mJ/pulse) to high (200 mJ/pulse) beam intensities. The flow structure behind the leading shock wave during the early planar shock state is confirmed by the high-resolution multimaterial hydrocode originally developed for shock compression of condensed matter. A repeatable lab-scale blast wave experiment is conducted at various energy levels with three different ablative targets, and both theoretical and computational analyses are used to verify the flow structures behind the leading shock front that remains spherically symmetric until all the momentum transferred from the absorbed intensity dissipates into open air a few microseconds later. (c) 2008 American Institute of Physics.


Addresses: Seoul Natl Univ, Sch Mech & Aerosp Engn, Seoul 151742, South Korea

Reprint Address: YOH, JJ, SEOUL NATL UNIV, SCH MECH & AEROSP ENGN, SEOUL 151742, SOUTH KOREA

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177


Author(s): Bezotosnyi, VV (Bezotosnyi, V. V.); Vasil'eva, VV (Vasil'eva, V. V.); Vinokurov, DA (Vinokurov, D. A.); Kapitonov, VA (Kapitonov, V. A.); Krokhin, ON (Krokhin, O. N.); Leshko, AY (Leshko, A. Yu.); Lyutetskili, AV (Lyutetskili, A. V.); Murashova, AV (Murashova, A. V.); Nalet, TA (Nalet, T. A.); Nikolaev, DN (Nikolaev, D. N.); Pikhtin, NA (Pikhtin, N. A.); Popov, YM (Popov, Yu. M.); Slipchenko, SO (Slipchenko, S. O.); Stankevich, AL (Stankevich, A. L.); Fetisova, NV (Fetisova, N. V.); Sharnakhov, VV (Sharnakhov, V. V.); Tarasov, IS (Tarasov, I. S.)

Title: High-power laser diodes of wavelength 808 nm based on various types of asymmetric heterostructures with an ultrawide waveguide

Source: SEMICONDUCTORS, 42 (3): 350-353 MAR 2008

Abstract:

The parameters of high-power multimode laser diodes featuring a radiation wavelenoth of 808 nm obtained on the basis of asymmetric heterostructures with an ultrawide waveguide in the systems of AlGaAs/GaAs and (Al)GaInP/GaInAsP/GaAs are compared. In the lasers based on an AlGaAs/GaAs system, the maximum optical power was limited by optical degradation of the SiO2/Si mirrors and amounted to 4.7 W. In the lasers based on an (Al)GaInP/GaInAsP/GaAs system, the maximum optical power was limited by thermal saturation and equaled 7 W. The obtained results show that the (AI)GaInP/GaInAsP/GaAs system is more reliable from the standpoint of an increase in both the maximum optical power and operation life of lasers.
Addresses: Russian Acad Sci, PN Lebedev Phys Inst, Moscow 117924, Russia

Russian Acad Sci, AF Ioffe Physicotech Inst, St Petersburg 194021, Russia

Reprint Address: BEZOTOSNYI, VV, RUSSIAN ACAD SCI, PN LEBEDEV PHYS INST, MOSCOW 117924, RUSSIA

Author's E-mail: a.murashova@mail.ioffe.ru

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178


Author(s): Germann, TD (Germann, T. D.); Strittmatter, A (Strittmatter, A.); Pohl, J (Pohl, J.); Pohl, UW (Pohl, U. W.); Bimberg, D (Bimberg, D.); Rautiainen, J (Rautiainen, J.); Guina, M (Guina, M.); Okhotnikov, OG (Okhotnikov, O. G.)

Title: High-power semiconductor disk laser based on InAs/GaAs submonolayer quantum dots - art. no. 101123

Source: APPLIED PHYSICS LETTERS, 92 (10): 1123-1123 MAR 10 2008

Abstract:

An optically pumped semiconductor disk laser using submonolayer quantum dots (SML QDs) as gain medium is demonstrated. High-power operation is achieved with stacked InAs/GaAs SML QDs grown by metal-organic vapor-phase epitaxy. Each SML-QD layer is formed from tenfold alternate depositions of nominally 0.5 ML InAs and 2.3 ML GaAs. Resonant periodic gain from a 13-fold nonuniform stack design of SML QDs allows to produce 1.4 W cw at 1034 nm. The disk laser demonstrates the promising potential of SML-QD structures combining properties of QD and quantum-well gain media for high-power applications. (C) 2008 American Institute of Physics.
Addresses: Tech Univ Berlin, Inst Festkorperphys, D-1000 Berlin, Germany

Tampere Univ Technol, Optoelect Res Ctr, Tampere 33720, Finland

Reprint Address: GERMANN, TD, TECH UNIV BERLIN, INST FESTKORPERPHYS, SEKR EW 5-2,HARDENBERGSTR 36, D-1000 BERLIN, GERMANY

Author's E-mail: tgermann@sol.physik.tu-berlin.de

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179


Author(s): Shayeganrad, G (Shayeganrad, Gholamreza); Mashhadi, L (Mashhadi, Leila)

Title: Efficient analytic model to optimum design laser resonator and optical coupling system of diode-end-pumped solid-state lasers: influence of gain medium length and pump beam M-2 factor

Source: APPLIED OPTICS, 47 (5): 619-627 FEB 10 2008

Abstract:

A comprehensive analytical model for optimization longitudinal pumping of ideal four-level lasers is presented for accurate analysis by removing limiting assumptions on active length and pump-beam radius in the gain medium. By taking into account the circular-symmetric Gaussian pump beam including the M-2 factor, an analytical formula for the root mean square of the pump beam in the active medium is developed to relate properties of the gain medium and pump beam to the requirement on efficient optimum design. Under the condition of minimum root mean square of pump-beam radius inside the active medium, the key parameters of the optimum optical coupling system have been analytically derived. Using these parameters, optimum mode size and maximum output efficiency are derived as a function of the gain medium length, absorption coefficient, pump-beam M-2 factor, and input power. Dependence of the obtained parameters on the gain medium length, absorption coefficient, pump-beam M-2 factor, and input power has been investigated. The results of this theory are found to be more comprehensive than the previous theoretical investigations. The present model provides a straightforward procedure to design the optimum laser resonator and the coupling optics for maximizing the output. (c) 2008 Optical Society of America.
Addresses: Amir Kabir Univ Technol, Dept Phys, Tehran, Iran

Reprint Address: SHAYEGANRAD, G, AMIR KABIR UNIV TECHNOL, DEPT PHYS, TEHRAN, IRAN

Author's E-mail: shayeganrad@yahoo.com

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180

Author(s): Fang, RR (Fang, Ranran); Zhang, DM (Zhang, Duanming); Li, ZH (Li, Zhihua); Yang, FX (Yang, Fengxia); Li, L (Li, Li); Tan, XY (Tan, Xinyu); Sun, M (Sun, Min)



Title: Improved thermal model and its application in UV high-power pulsed laser ablation of metal target

Source: SOLID STATE COMMUNICATIONS, 145 (11-12): 556-560 MAR 2008

Abstract:

An improved thermal model describing UV high-power nanosecond laser ablation of metal target is presented. The vaporization effect, the plasma shielding effect, as well as the absorption coefficient and absorptivity dependence of temperature are considered in this model. Take iron target as an example, the numerical solutions are obtained from the heat flow equations (before and after melting) using a finite difference method. The space and time dependence of temperature of the target, the time dependence of temperature at two different positions for a certain laser fluence, and the ablation rate as a function of laser fluence are also presented. The numerical results that agreed well with the experimental data are much better than the one without, which indicates that the above two effects and the temperature dependence of absorption coefficient and absorptivity in UV high-power laser ablation of metal target should not be neglected. We hope the present model will be useful for further experimental investigation of metal thin films prepared by pulsed laser deposition. (C) 2008 Elsevier Ltd. All rights reserved.


Addresses: Huazhong Univ Sci & Technol, Dept Phys, Wuhan 430074, Peoples R China

Reprint Address: ZHANG, DM, HUAZHONG UNIV SCI & TECHNOL, DEPT PHYS, WUHAN 430074, PEOPLES R CHINA

Author's E-mail: ranranfang2@gmail.com

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181

Author(s): Song, HW (Song, Hong-Wei); Yu, G (Yu, Gang); Tan, JS (Tan, Jian-Song); Zhou, L (Zhou, Liang); Yu, XL (Yu, Xiao-Li)



Title: Thermal fatigue on pistons induced by shaped high power laser. Part I: Experimental study of transient temperature field and temperature oscillation

Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 51 (3-4): 757-767 FEB 2008

Abstract:

Thermal fatigue behavior is one of the foremost considerations in the design and operation of diesel engines. It is found that thermal fatigue is closely related to the temperature field and temperature fluctuation in the structure. In this paper, spatially shaped high power laser was introduced to simulate thermal loadings on the piston. The incident Gaussian beam was transformed into concentric multi-circular beam of specific intensity distribution with the help of diffractive optical element (DOE), and the transient temperature fields in the piston similar to those under working conditions could be achieved by setting up appropriate loading cycles. Simulation tests for typical thermal loading conditions, i.e., thermal high cycle fatigue (HCF) and thermal shock (or thermal low cycle fatigue, LCF) were carried out. Several important parameters that affect the transient temperature fields and/or temperature oscillations, including controlling mode, intensity distribution of shaped laser, laser power, temporal profile of laser pulse, heating time and cooling time in one thermal cycle, etc., were investigated and discussed. The results show that as a novel method, the shaped high power laser can simulate thermal loadings on pistons efficiently, and it is helpful in the study of thermal fatigue behavior in pistons. (C) 2007 Elsevier Ltd. All rights reserved.


Addresses: Chinese Acad Sci, Inst Mech, Lab Laser Intelligent Mfg, Beijing 100080, Peoples R China

Chinese Acad Sci, Inst Mech, LNM, State Key Lab Nonlinear Mech, Beijing 100080, Peoples R China

Zhejiang Univ, Coll Mech & Energy Engn, Hangzhou 310027, Peoples R China

Reprint Address: SONG, HW, CHINESE ACAD SCI, INST MECH, LAB LASER INTELLIGENT MFG, BEIJING 100080, PEOPLES R CHINA

Author's E-mail: songhw@imech.ac.cn

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182

Author(s): Song, HW (Song, Hong-Wei); Yu, G (Yu, Gang); Kaplan, AFH (Kaplan, Alexander F. H.); Tan, HS (Tan, Han-Song); Yu, XL (Yu, Xiao-Li)



Title: Thermal fatigue on pistons induced by shaped high power laser. Part II: Design of spatial intensity distribution via numerical simulation

Source: INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 51 (3-4): 768-778 FEB 2008

Abstract:

In the laser induced thermal fatigue simulation test on pistons, the high power laser was transformed from the incident Gaussian beam into a concentric multi-circular pattern with specific intensity ratio. The spatial intensity distribution of the shaped beam, which determines the temperature field in the piston, must be designed before a diffractive optical element (DOE) can be manufactured. In this paper, a reverse method based on finite element model (FEM) was proposed to design the intensity distribution in order to simulate the thermal loadings on pistons. Temperature fields were obtained by solving a transient three-dimensional heat conduction equation with convective boundary conditions at the surfaces of the piston workpiece. The numerical model then was validated by approaching the computational results to the experimental data. During the process, some important parameters including laser absorptivity, convective heat transfer coefficient, thermal conductivity and Biot number were also validated. Then, optimization procedure was processed to find favorable spatial intensity distribution for the shaped beam, with the aid of the validated FEM. The analysis shows that the reverse method incorporated with numerical simulation can reduce design cycle and design expense efficiently. This method can serve as a kind of virtual experimental vehicle as well, which makes the thermal fatigue simulation test more controllable and predictable. (C) 2007 Elsevier Ltd. All rights reserved.


Addresses: Chinese Acad Sci, Inst Mech, Lab Laser Intelligent Mfg, Beijing 100080, Peoples R China

Lulea Univ Technol, Div Mfg Syst Engn, SE-97187 Lulea, Sweden

Zhejiang Univ, Coll Mech & Energy Engn, Hangzhou 310027, Peoples R China

Reprint Address: SONG, HW, CHINESE ACAD SCI, INST MECH, LAB LASER INTELLIGENT MFG, BEIJING 100080, PEOPLES R CHINA

Author's E-mail: songhw@imech.ac.cn

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183

Author(s): Lundeman, JH (Lundeman, Jesper Holm); Jensen, OB (Jensen, Ole Bjarlin); Andersen, PE (Andersen, Peter E.); Andersson-Engels, S (Andersson-Engels, Stefan); Sumpf, B (Sumpf, Bernd); Erbert, G (Erbert, Gotz); Petersen, PM (Petersen, Paul Michael)



Title: High power 404 nm source based on second harmonic generation in PPKTP of a tapered external feedback diode laser

Source: OPTICS EXPRESS, 16 (4): 2486-2493 FEB 18 2008

Abstract:

We present results on a 404 nm laser system based on second harmonic generation in a new compact external cavity configuration. We obtain a stable 318 mW cw diffraction limited output from the system with a mode-matched pump power of 630 mW. We observe up to 620 mW SHG, when the cavity is operating in scanning mode. The pump source is an external cavity grating feedback tapered diode laser operating at 808 nm. We find that thermal effects in the nonlinear crystal severely limit the efficiency of the setup with high input powers. (C) 2008 Optical Society of America.


Addresses: Tech Univ Denmark, DTU Fotonik, DK-4000 Roskilde, Denmark

Lund Inst Technol, Dept Phys, SE-22100 Lund, Sweden

Ferdinand Braun Inst Hochstfrequenztechn, D-12489 Berlin, Germany

Reprint Address: LUNDEMAN, JH, TECH UNIV DENMARK, DTU FOTONIK, FREDERIKSBORGVEJ 399, DK-4000 ROSKILDE, DENMARK

Author's E-mail: jesper.holm@risoe.dk

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184

Author(s): Zheng, Y (Zheng, Y.); Lu, H (Lu, H.); Li, Y (Li, Y.); Zhang, K (Zhang, K.); Peng, K (Peng, K.)



Title: Broadband and rapid tuning of an all-solid-state single-frequency Nd : YVO4 laser

Source: APPLIED PHYSICS B-LASERS AND OPTICS, 90 (3-4): 485-488 MAR 2008

Abstract:

A diode-pumped tunable single-frequency Nd:YVO4 laser has been built. The laser incorporates a LiNbO3 etalon (LE) as a coarse tuning element and a LiNbO3 crystal (LC) as a fine tuning element to obtain broadband, rapid tuning. More than 480 mW of output power has been obtained from the tunable laser with frequency tuning range of 17.2 GHz and the tuning response time of 10 ns.


Addresses: Shanxi Univ, Inst Optoelect, State Key Lab Quantum Opt & Quantum Opt Devices, Taiyuan 030006, Peoples R China

Reprint Address: ZHANG, K, SHANXI UNIV, INST OPTOELECT, STATE KEY LAB QUANTUM OPT & QUANTUM OPT DEVICES, TAIYUAN 030006, PEOPLES R CHINA

Author's E-mail: kuanshou@sxu.edu.cn

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185

Author(s): Kachurin, GA (Kachurin, G. A.); Cherkova, SG (Cherkova, S. G.); Volodin, VA (Volodin, V. A.); Marin, DV (Marin, D. V.); Deutschmann, M (Deutschmann, M.)



Title: Effect of high-power nanosecond and femtosecond laser pulses on silicon nanostructures

Source: SEMICONDUCTORS, 42 (2): 183-187 FEB 2008

Abstract:

The effect of high-power nanosecond (20 ns) and femtosecond (120 fs) laser pulses on silicon nanostructures produced by ion-beam-assisted synthesis in SiO2 layers or by deposition onto glassy substrates is studied. Nanosecond annealing brings about a photoluminescence band at about 500 mn, with the intensity increasing with the energy and number of laser pulses. The source of the emission is thought to be the clusters of Si atoms segregated from the oxide. In addition, the nanosecond pulses allow crystallization of amorphous silicon nanoprecipitates in SiO2. Heavy doping promotes crystallization. The duration of femtosecond pulses is too short for excess Si to be segregated from SiO2. At the same time, such short pulses induce crystallization of Thin a-Si films on glassy substrates. The energy region in which crystallization is observed for both types of pulses allows short-term melting of the surface layer.


Addresses: Russian Acad Sci, Inst Semicond Phys, Siberian Branch, Novosibirsk 630090, Russia

Laser Zentrum Hannover, D-30419 Hannover, Germany

Reprint Address: KACHURIN, GA, RUSSIAN ACAD SCI, INST SEMICOND PHYS, SIBERIAN BRANCH, NOVOSIBIRSK 630090, RUSSIA

Author's E-mail: kachurin@isp.nsc.ru

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186


Author(s): Bezotosnyi, VV (Bezotosnyi, V. V.); Bondarev, VY (Bondarev, V. Yu.); Kovalenko, VI (Kovalenko, V. I.); Krokhin, ON (Krokhin, O. N.); Pevtsov, VF (Pevtsov, V. F.); Popov, YM (Popov, Yu. M.); Tokarev, VN (Tokarev, V. N.); Cheshev, EA (Cheshev, E. A.)

Title: Modification of metal film structure by radiation from a diode-pumped solid-state laser for improving the output parameters of high-power laser diodes

Source: QUANTUM ELECTRONICS, 37 (11): 1055-1059 NOV 2008

Abstract:

Metal films of heat-removing elements deposited by magnetron sputtering are modified by radiation from a diode-pumped pulsed solid-state Nd : YAG laser to improve the output parameters of high-power laser diodes.
Addresses: Russian Acad Sci, PN Lebedev Phys Inst, Moscow 119991, Russia

Russian Acad Sci, AM Prokhrov Gen Phys Inst, Moscow 119991, Russia

Reprint Address: BEZOTOSNYI, VV, RUSSIAN ACAD SCI, PN LEBEDEV PHYS INST, LENINSKY PROSP 53, MOSCOW 119991, RUSSIA

Author's E-mail: viktorbe@sci.lebedev.ru

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187


Author(s): Richard, K (Richard, K.); Manson, P (Manson, P.); Ewart, P (Ewart, P.)

Title: A widely tunable, high power, single-mode laser for linear and nonlinear spectroscopy - art. no. 015603

Source: MEASUREMENT SCIENCE & TECHNOLOGY, 19 (1): 15603-15603 JAN 2008

Abstract:

A laser system based on a modeless laser, acting as a narrow bandwidth amplifier, seeded by a single-mode diode laser is reported with significantly improved performance for continuous scanning over a wide spectral range. A novel arrangement is described for scanning the modeless laser to maintain the peak amplification of the narrow bandwidth amplifier at the frequency of the seeding diode laser as it is tuned in frequency. An error signal is generated by optical pick-up of the displacement of the seeding laser generated by dispersion in the modeless laser. The error signal is used to drive a tuning mechanism to correct the central frequency of the modeless laser to match that of the seed laser. This 'seeding by optical pick-up error correction' is demonstrated to provide continuous single-mode scanning and to correct for mode hops in the master oscillator over a range exceeding 170 cm(-1). Application of the system for wide spectral coverage and high-resolution linear and nonlinear laser spectroscopy is illustrated by absorption spectroscopy and polarization spectroscopy of molecular iodine.
Addresses: Univ Oxford, Clarendon Lab, Oxford OX1 3PU, England

Univ Otago, Dept Phys, Dunedin, New Zealand

Reprint Address: RICHARD, K, UNIV OXFORD, CLARENDON LAB, PARKS RD, OXFORD OX1 3PU, ENGLAND

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188

Author(s): Liu, XS (Liu Xue-Sheng); Wang, ZY (Wang Zhi-Yong); Yan, X (Yan Xin); Cao, YH (Cao Ying-Hua)



Title: A high-energy good-beam-quality krypton-lamp-pumped Nd : YAG solid-state laser with one pump cavity

Source: CHINESE PHYSICS LETTERS, 25 (2): 521-523 FEB 2008

Abstract:

We investigate a high-energy good-beam-quality krypton-lamp-pumped pulsed Nd:YAG solid-state laser with one pump cavity. The symmetrical resonator laser is developed and is rated at 80J with beam parameter product 12mm mrad. The total system electro-optics efficiency of the lamp-pumped YAG laser is as high as 3.3% and the stability of output energy is +/-2% with pulse width tunable between 0.1 ms and 10ms. The experimental results are consistent with the theoretical analysis and simulation.


Addresses: Beijing Polytech Univ, Coll Laser Engn, Beijing 100022, Peoples R China

Reprint Address: LIU, XS, BEIJING POLYTECH UNIV, COLL LASER ENGN, BEIJING 100022, PEOPLES R CHINA

Author's E-mail: xueshengl@emails.bjut.edu.cn

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189

Author(s): Kanai, T (Kanai, Takuya); Suda, A (Suda, Akira); Bohman, S (Bohman, Samuel); Kaku, M (Kaku, Masanori); Yamaguchi, S (Yamaguchi, Shigeru); Midorikawa, K (Midorikawa, Katsumi)



Title: Pointing stabilization of a high-repetition-rate high-power femtosecond laser for intense few-cycle pulse generation - art. no. 061106

Source: APPLIED PHYSICS LETTERS, 92 (6): 61106-61106 FEB 11 2008

Abstract:

We have developed a beam stabilization system for high-power femtosecond lasers operating at a repetition rate of 1 kHz. The beam pointing at a hollow fiber input was stabilized to within 1 mu m rms and the fluctuations of the broadened spectra and power were significantly improved. This technique enables us to increase the input power to a hollow fiber for intense few-cycle pulse generation. (c) 2008 American Institute of Physics.


Addresses: Tokai Univ, Dept Phys, Kanagawa 2591292, Japan

RIKEN, Wako, Saitama 3510198, Japan

Reprint Address: KANAI, T, TOKAI UNIV, DEPT PHYS, 1117 KITA KANAME, KANAGAWA 2591292, JAPAN

Author's E-mail: asuda@riken.jp

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190


Author(s): Qin, LJ (Qin, L. J.); Tang, DY (Tang, D. Y.); Xie, GQ (Xie, G. Q.); Dong, CM (Dong, C. M.); Jia, ZT (Jia, Z. T.); Tao, XT (Tao, X. T.)

Title: High-power continuous wave and passively Q-switched laser operations of a Nd : GGG crystal

Source: LASER PHYSICS LETTERS, 5 (2): 100-103 FEB 2008

Abstract:

We report on the continuous wave (CW) and passive Q-switching performance of a high-power diode-pumped Nd:GGG laser. A CW output power of 7.20 W was obtained under an absorbed pump power of 14.97 W, which gives a slop efficiency of 52.7%. With a Cr4+ doped yttrium aluminum garnet crystal as the saturable absorber, the shortest passively Q-switched pulse width, largest pulse energy, and highest peak power achieved were 7.7 ns, 126.25 mu J, and 15.5 kW, respectively.
Addresses: Yantai Univ, Sch Environm & Mat Engn, Yantai 264005, Peoples R China

Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore 639798, Singapore

Shandong Univ, Natl Lab Crystal Mat, Jinan 250100, Peoples R China

Reprint Address: QIN, LJ, YANTAI UNIV, SCH ENVIRONM & MAT ENGN, YANTAI 264005, PEOPLES R CHINA

Author's E-mail: ljqin@ntu.edu.sg

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191

Author(s): Chen, SP (Chen, S. -P.); Li, YG (Li, Y-G.); Lu, KC (Lu, K. -C.); Zhou, SH (Zhou, S. -H.); Liu, ZJ (Liu, Z. -J.)



Title: High power L-band erbium-doped fiber laser pumped by a C-band superfluorescent source

Source: LASER PHYSICS LETTERS, 5 (2): 130-134 FEB 2008

Abstract:

The C-band is demonstrated to be suitable for pumping L-band erbium-doped fiber laser (EDFL) with a broad pumping band. A high power C-band superfluorescent fiber source (SFS) peaked at 1545 nm with output power of 1.86 W is constructed and utilized as pump source for L-band EDFL. Based on this, an all single-mode-fiber L-band EDFL emitting at 1591.9 nm with 1.19 W output power is obtained. The laser exhibits a high conversion efficiency of 64.0% with a high ASE extinction ratio of 66 dB and a narrow bandwidth of less than 0.08 nm.


Addresses: Nankai Univ, Inst Phys, Tianjin 300071, Peoples R China

Natl Univ Def Technol, Coll Optoelect Sci & Engn, Changsha 410073, Peoples R China

Reprint Address: CHEN, SP, NANKAI UNIV, INST PHYS, TIANJIN 300071, PEOPLES R CHINA

Author's E-mail: chespn@163.com

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192


Author(s): Hopkins, JM (Hopkins, J. -M.); Hempler, N (Hempler, N.); Rosener, B (Roesener, B.); Schulz, N (Schulz, N.); Rattunde, M (Rattunde, M.); Manz, C (Manz, C.); Kohler, K (Koehler, K.); Wagner, J (Wagner, J.); Burns, D (Burns, D.)

Title: High-power, (AlGaIn)(AsSb) semiconductor disk laser at 2.0 mu m

Source: OPTICS LETTERS, 33 (2): 201-203 JAN 15 2008

Abstract:

We report a high-power (AlGaIn)(AsSb) semiconductor disk laser emitting around 2 mu m. With a diamond heat spreader used for thermal management, a maximum output power of just over 5 W and slope efficiencies of over 25% were demonstrated. The output wavelength was tunable over an 80 nm range centered at 1.98 mu m. The beam propagation parameter (M-2) was measured to be in the range of 1.1 to 1.4 for output powers up to 3 W. (c) 2008 Optical Society of America.
Addresses: Univ Strathclyde, SUPA, Inst Photon, Wolfson Ctr, Glasgow G4 0NW, Lanark, Scotland

Fraunhofer Inst Appl Solid Phys, Freiburg, Germany

Reprint Address: HOPKINS, JM, UNIV STRATHCLYDE, SUPA, INST PHOTON, WOLFSON CTR, 106 ROTTENROW, GLASGOW G4 0NW, LANARK, SCOTLAND

Author's E-mail: johnmark.hopkins@strath.ac.uk

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193


Author(s): Li, LB (Li, Libo); Lou, QH (Lou, Qihong); Zhou, J (Zhou, Jun); Dong, JX (Dong, Jingxing); Wei, YR (Wei, Yunrong); Du, ST (Du, Songtao); He, B (He, Bing)

Title: High power single transverse mode operation of a tapered large-mode-area fiber laser

Source: OPTICS COMMUNICATIONS, 281 (4): 655-657 FEB 15 2008

Abstract:

To get high output power with good beam quality, a tapered section is introduced to large-mode-area (LMA) Yb-doped fiber laser. Output characteristics of the fiber laser without tapered section and with tapered section are compared experimentally. When the launched pump power is 119.1 W, 77.9 W with M-2 3.08 and 56.4 W with M-2 1.14 can be obtained, respectively. The corresponding slope efficiencies are 71.8% and 54.1%, respectively. Although output power of the tapered fiber laser has 30.6% penalty, brightness of it is as much as 5.28 times of the fiber laser without tapered section. Moreover, spectra of them are measured. It is found that tapered section makes lasing wavelength of the fiber laser shorter. (c) 2007 Elsevier B.V. All rights reserved.
Addresses: Chinese Acad Sci, Shanghai Inst Opt & Fine Mech, Shanghai 201800, Peoples R China

Reprint Address: LI, LB, CHINESE ACAD SCI, SHANGHAI INST OPT & FINE MECH, SHANGHAI 201800, PEOPLES R CHINA

Author's E-mail: whrichardlee@yahoo.com

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194

Author(s): Chen, CH (Chen, Ching-Hsu); Lin, JH (Lin, Ja-Hon)



Title: Dynamics in a tightly-focused end-pumped solid-state laser near degenerate cavity configurations

Source: OPTICS COMMUNICATIONS, 281 (4): 683-691 FEB 15 2008

Abstract:

We numerically study the dynamics of a tightly-focused end-pumped solid-state laser near the degenerate cavity configurations by using the Collins integral together with a rate equation. We find that the field and gain adjust their distributions to exhibit the temporal rather than spatiotemporal instabilities in spite of the coupling of many transverse modes. These instabilities are attributed to the frequency locking but phase unlocking of the degenerate Laguerre-Gaussian modes. The phase portrait is plotted in the three dimensional space with gain, real part, and imaginary part of the field because of similar dynamics for every transverse point. Both of the portrait and the Poincare map show the peculiar features. Moreover, the route to chaos is the mixed effect of period-doubling and quasi-period as the cavity length is tuned. (c) 2007 Elsevier B.V. All rights reserved.


Addresses: Natl Chiayi Univ, Dept Appl Phys, Chiayi 600, Taiwan

Natl Taipei Univ Technol, Inst Electroopt Engn, Taipei 10608, Taiwan

Reprint Address: CHEN, CH, NATL CHIAYI UNIV, DEPT APPL PHYS, CHIAYI 600, TAIWAN

Author's E-mail: chchen@mail.ncyu.edu.tw

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195


Author(s): Katsavets, NI (Katsavets, N. I.); Buchenkov, VA (Buchenkov, V. A.); Iskandarov, MO (Iskandarov, M. O.); Nikitichev, AA (Nikitichev, A. A.); Sokolov, EG (Sokolov, E. G.); Ter-Martirosyan, AL (Ter-Martirosyan, A. L.)

Title: High-power semiconductor radiation sources based on 100-W diode laser bars for pumping solid-state lasers

Source: TECHNICAL PHYSICS LETTERS, 34 (1): 46-47 JAN 2008

Abstract:

High-power semiconductor radiation sources with a total optical output power of up to 5 kW and a power density of 400 W/cm(2) have been developed, representing a vertical stack of quasi-continuous pulsed (500 mu s) 100-W diode laser bars. Based on such sources, a solid-state laser with an output radiation energy of up to 150 mJ has been created, which is intended for information systems, laser radars, spectrum analyzers, etc.
Addresses: ATC, Semicond Device Joint Stock Co, St Petersburg, Russia

State Sci Ctr Russian Fed, SI Vavilov State Opt Inst, St Petersburg, Russia

State Res Inst Semicond Devices, St Petersburg, Russia

Reprint Address: KATSAVETS, NI, ATC, SEMICOND DEVICE JOINT STOCK CO, ST PETERSBURG, RUSSIA

Author's E-mail: n_katsavets@mail.ru

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196

Author(s): Ramadurai, K (Ramadurai, Krishna); Cromer, CL (Cromer, Christopher L.); Lewis, LA (Lewis, Laurence A.); Hurst, KE (Hurst, Katherine E.); Dillon, AC (Dillon, Anne C.); Mahajan, RL (Mahajan, Roop L.); Lehman, JH (Lehman, John H.)



Title: High-performance carbon nanotube coatings for high-power laser radiometry - art. no. 013103

Source: JOURNAL OF APPLIED PHYSICS, 103 (1): 13103-13103 JAN 1 2008

Abstract:

Radiometry for the next generation of high-efficiency, high-power industrial lasers requires thermal management at optical power levels exceeding 10 kW. Laser damage and thermal transport present fundamental challenges for laser radiometry in support of common manufacturing processes, such as welding, cutting, ablation, or vaporization. To address this growing need for radiometry at extremely high power densities, we demonstrate multiwalled carbon nanotube (MWCNT) coatings with damage thresholds exceeding 15 000 W/cm(2) and absorption efficiencies over 90% at 1.06 mu m. This result demonstrates specific design advantages not possible with other contemporary high-power laser coatings. Furthermore, the results demonstrate a performance difference between MWCNTs and single-walled carbon nanotube coatings, which is attributed to the lower net thermal resistance of the MWCNT coatings. We explore the behavior of carbon nanotubes at two laser wavelengths (1.06 and 10.6 mu m) and also evaluate the optical-absorption efficiency and bulk properties of the coatings. (c) 2008 American Institute of Physics.


Addresses: Natl Inst Stand & Technol, Boulder, CO 80305 USA

Univ Colorado, Dept Mech Engn, Boulder, CO 80309 USA

James Madison Univ, Harrisonburg, VA 22807 USA

Natl Renewable Energy Lab, Golden, CO 80305 USA

Virginia Tech, Dept Engn Sci & Mech, Dept Mech Engn, ICTAS, Blacksburg, VA 24060 USA

Reprint Address: LEHMAN, JH, NATL INST STAND & TECHNOL, BOULDER, CO 80305 USA

Author's E-mail: john.lehman@nist.gov

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197

Author(s): Yuan, J (Yuan, J.); Wang, H (Wang, H.); Wu, G (Wu, G.); Liu, H (Liu, H.); Zhang, Y (Zhang, Y.); Yang, L (Yang, L.)



Title: High-power (80 W) potassium titanyl phosphate laser prostatectomy in 128 high-risk patients

Source: POSTGRADUATE MEDICAL JOURNAL, 84 (987): 46-49 JAN 2008

Abstract:

Objective: To evaluate the safety and merits of 80 W potassium titanyl phosphate (KTP) laser prostatectomy in men with high cardiovascular or pulmonary risk, receiving oral anticoagulant medication, or with bleeding disorders.

Methods: A prospective clinical trial was performed in 128 high-risk men with benign prostatic hyperplasia who underwent photoselective vaporisation of the prostate (PVP). The operation time, postoperative serum sodium and packed cell volume were recorded. The International Prostate Symptom Score (IPSS), maximal flow rate (Q(max)) and post-void residual urine volume (PVR) were measured at every follow-up visit.

Results: In all patients, KTP laser prostatectomy was performed successfully. The mean (SD) operation time was 51.6 (22.8) min. No blood transfusions were required. No major complications occurred during surgery, and there was no mortality. The mean (SD) catheterisation time was 2.8 (1.6) days. IPSS decreased from 19.2 (6.1) before surgery to 11.5 (8.2), 7.8 (6.4), 6.7 (5.3) and 6.1 (4.6), respectively, at 1, 3, 6 and 12 months after. Q(max) increased from 7.0 (2.8) ml/s to 14.5 (9.3), 20.2 (11.5), 21.3 (8.6) and 24.8 (8.0) ml/s, respectively. PVR decreased from 168 (89) ml to 35 (29), 30 (26), 27 (21) and 23 (34) ml, respectively.

Conclusions: 80 W KTP laser prostatectomy is a virtually bloodless, safe and effective procedure for men with high cardiovascular or pulmonary risk or bleeding disorders or taking oral anticoagulant medication.
Addresses: Fourth Mil Med Univ, Xijing Hosp, Dept Urol, Xian 710032, Peoples R China

Reprint Address: WU, G, FOURTH MIL MED UNIV, XIJING HOSP, DEPT UROL, XIAN 710032, PEOPLES R CHINA

Author's E-mail: jianliny@fmmu.edu.cn

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198

Author(s): Jing, G (Jing, Gao); Xin, Y (Xin, Yu); Fei, C (Fei, Chen); Xu-Dong, L (Xu-Dong, Li); Zhen, Z (Zhen, Zhang); Jun-Hua, Y (Jun-Hua, Yu); Yue-Zhu, W (Yue-Zhu, Wang)



Title: High power continuous-wave and acousto-optic Q-switched Nd : GdVO4 laser operated at 912 nm

Source: CHINESE PHYSICS LETTERS, 25 (1): 119-121 JAN 2008

Abstract:

We present a high power and efficient operation of the F-4(3/2) -> I-4(9/2) transition in Nd:GdVO4 at 912nm. In the cw mode, the maximum output power of 8.6 W is achieved when the incident pump power is 40.3 W, leading to a slope efficiency of 33.3% and an optical-optical efficiency of 21.3%. To the best of our knowledge, this is the highest cw laser power at 912nm obtained with the conventional Nd:GdVO4 crystal. Pulsed operation of 912 nm laser has also been realized by inserting a small acousto-optic (A-O) Q-Switch inside the resonator. As a result, the minimal pulse width of 20ns and the average laser power 1.43 W at the repetition rate of 10kHz are obtained, corresponding to 7.1 kW peak power. We believe that this is the highest laser peak power at 912 nm. Furthermore, duration of 65ns has also been acquired when the repetition rate is 100kHz.


Addresses: Harbin Inst Technol, Inst Optoelect, Harbin 150001, Peoples R China

Reprint Address: JING, G, HARBIN INST TECHNOL, INST OPTOELECT, HARBIN 150001, PEOPLES R CHINA

Author's E-mail: owengaojing@126.com

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199

Author(s): Lyutetskii, AV (Lyutetskii, A. V.); Borshchev, KS (Borshchev, K. S.); Pikhtin, NA (Pikhtin, N. A.); Slipchenko, SO (Slipchenko, S. O.); Sokolova, ZN (Sokolova, Z. N.); Tarasov, IS (Tarasov, I. S.)



Title: Contribution of Auger recombination to saturation of the light-current characteristics in high-power laser diodes (lambda=1.0-1.9 mu m)

Source: SEMICONDUCTORS, 42 (1): 104-111 JAN 2008

Abstract:

Spectral and light-current characteristics of lasers based on the asymmetric separate-confinement heterostructures InGaAs/InGaAsAl/InP and InGaAs/GaAs/AlGaAs/GaAs were studied in the pulsed mode of lasing. It is shown that, at high levels of current pumping, the charge-carrier concentration in the active region of semiconductor lasers for the near-infrared optical region increases beyond the oscillation threshold; drastic saturation of the light-current characteristics is observed. Processes occurring in lasers as the charge-carrier concentration increases beyond the lasing threshold are studied theoretically. It is established that, at high pump levels, the rate of stimulated recombination decreases, the lifetime of charge carriers increases, and both the concentration of emitted photons and the quantum yield of stimulated radiation decrease. It is shown that variations in stimulated recombination, the decrease in the quantum efficiency, and saturation of the light-current characteristic in semiconductor lasers at high levels of current pumping are caused by the contribution of the nonradiative Auger recombination.


Addresses: Russian Acad Sci, AF Ioffe Physicotech Inst, St Petersburg 194021, Russia

Voronezh State Univ, Voronezh 394006, Russia

Reprint Address: LYUTETSKII, AV, RUSSIAN ACAD SCI, AF IOFFE PHYSICOTECH INST, ST PETERSBURG 194021, RUSSIA

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200

Author(s): Hou, KC (Hou, Kai-Chung); George, S (George, Simi); Mordovanakis, AG (Mordovanakis, Aghapi G.); Takenoshita, K (Takenoshita, Kazutoshi); Nees, J (Nees, John); Lafontaine, B (Lafontaine, Bruno); Richardson, M (Richardson, Martin); Galvanauskas, A (Galvanauskas, Almantas)



Title: High power fiber laser driver for efficient EUV lithography source with tin-doped water droplet targets

Source: OPTICS EXPRESS, 16 (2): 965-974 JAN 21 2008

Abstract:

In this paper we report the development of nanosecond-pulsed fiber laser technology for the next generation EUV lithography sources. The demonstrated fiber laser system incorporates large core fibers and arbitrary optical waveform generation, which enables achieving optimum intensities and other critical beam characteristics on a laser-plasma target. Experiment demonstrates efficient EUV generation with conversion efficiency of up to 2.07% for in-band 13.5-nm radiation using mass-limited Sn-doped droplet targets. This result opens a new technological path towards fiber laser based high power EUV sources for high-throughput lithography steppers. (c) 2007 Optical Society of America.


Addresses: Univ Michigan, Ctr Ultrafast Opt Sci, Ann Arbor, MI 48109 USA

Univ Cent Florida, Coll Opt & Photon, Townes Laser Inst, Laser Plasma Lab, Orlando, FL 32816 USA

Adv Micro Devices Inc, Sunnyvale, CA 94088 USA

Reprint Address: HOU, KC, UNIV MICHIGAN, CTR ULTRAFAST OPT SCI, 2200 BONISTEEL BLVD, ANN ARBOR, MI 48109 USA

Author's E-mail: kchou@umich.edu

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201

Author(s): Yong-Ming, Y (Yong-Ming, Yang); Qi-Ming, X (Qi-Ming, Xu); Zhen, G (Zhen, Guo)



Title: Cystal end temperature distribution under different pumping light in solid state laser

Source: ACTA PHYSICA SINICA, 57 (1): 223-229 JAN 2008

Abstract:

In order to study how different pumping light profiles affect the crystal end temperature field, a classification creterion is suggested, according to which the pumping light can be classified as column light, Gaussian light and plane top light. The end temperature under different pumping power and different pumping light focus diameter are studied. It was found that the end temperature is the highest under the column pumping light, intermediate plane top pumping light and lowesl under Gaussian pumping light when the pumping light has the same : power and the same focus diameter. It shows that the pumping light profile can seriously affect the crystal end temperature field. Finally the effect of the thermal effect caused by the end temperature was studied, which was found to affect the laser quality seriously. When the equivalent curvature radius of the thermal lens changes front 85 to 150 mm, the far field walk-off angle and waist diameter become larger and larger and the laser works unsteadily.


Addresses: Xian Univ Architecture & Technol, Sch Sci, Xian 710055, Peoples R China

Xian Univ Architecture & Technol, Sch Mat, Xian 710055, Peoples R China

Xidian Univ, Sch Tech Phys, Xian 710071, Peoples R China

Reprint Address: YONG-MING, Y, XIAN UNIV ARCHITECTURE & TECHNOL, SCH SCI, XIAN 710055, PEOPLES R CHINA

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202


Author(s): Okulov, AY (Okulov, A. Yu)

Title: 3D-vortex labyrinths in the near field of solid-state microchip laser

Source: JOURNAL OF MODERN OPTICS, 55 (2): 241-259 2008

Abstract:

The usage of vortex-labyrinth fields and Talbot lattices as optical dipole traps for neutral atoms is considered for the wavelength of trapping radiation in the range 0.98-2.79 mu m. The square vortex lattices generated in high Fresnel number solid-state microchip lasers are studied as a possible realization. The distribution of light field is obtained via a nonstationary computational model based on Maxwell-Bloch equations for a class-B laser, discrete Fox-Lee map with relaxation of inversion and a static model based on superposition of copropagating Gaussian beams. The spatial patterns obtained numerically and observed experimentally previously are interpreted as nonlinear superposition of vortices with helicoidal phase dislocations. The distribution of light field is approximated analytically by a sum of array of vortex lines and an additional parabolic subtrap. The separable optical trapping potential is proposed with similar intensity distribution. The factorization of the macroscopic wavefunction has led to the solution of the Gross-Pitaevsky equation for an ensemble of quantum particles trapped in a vortex labyrinth formed by a spatially periodic array of Laguerre-Gaussian beams.
Addresses: Russian Acad Sci, PN Lebedev Phys Inst, Moscow 119991, Russia

Reprint Address: OKULOV, AY, RUSSIAN ACAD SCI, PN LEBEDEV PHYS INST, LENINSKY PROSPECT 53, MOSCOW 119991, RUSSIA

Author's E-mail: okulov@sci.lebedev.ru

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203

Author(s): Li, P (Li, Pingxue); Zhu, C (Zhu, Chen); Zou, S (Zou, Shuzhen); Zhao, H (Zhao, Hong); Jiang, D (Jiang, Dongsheng); Li, G (Li, Gang); Chen, M (Chen, Meng)



Title: Theoretical and experimental investigation of thermal effects in a high power Yb3+-doped double-clad fiber laser

Source: OPTICS AND LASER TECHNOLOGY, 40 (2): 360-364 MAR 2008

Abstract:

In this paper, based on the thermal conduction equations and the steady-state rate equations, a theoretical and numerical analysis of thermal effects is investigated for a single end pumped Yb-doped double-clad fiber laser (YDDC). The distributions of signal power and temperature for different pump powers and fiber parameters are compared. According to the results, the parameters of the optical-cavity have been optimized and an effective method has been adopted to reduce the thermal effects in an experimental investigation. As a result, an output power of 621 W has been obtained with a slope efficiency of 78%. (c) 2007 Elsevier Ltd. All rights reserved.


Addresses: Beijing Univ Technol, Inst Laser Engn, Beijing 100022, Peoples R China

N China Res Inst Electro Opt, Beijing 100015, Peoples R China

Reprint Address: LI, P, BEIJING UNIV TECHNOL, INST LASER ENGN, BEIJING 100022, PEOPLES R CHINA

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204

Author(s): Abboud, JH (Abboud, J. H.); Fidel, AF (Fidel, A. F.); Benyounis, KY (Benyounis, K. Y.)



Title: Surface nitriding of Ti-6Al-4V alloy with a high power CO2 laser

Source: OPTICS AND LASER TECHNOLOGY, 40 (2): 405-414 MAR 2008

Abstract:

Surface nitriding of a Ti-6Al-4V alloy by laser melting in a flow of nitrogen gas has been investigated, with the aim of increasing surface hardness and hence improving related properties such as wear and erosion resistance. The effect of the scanning speed, nitrogen dilution, and nitrogen flow rate on microstructure, microhardness, and cracking of the nitrided layers was studied. Optical, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction (XRD) were used to reveal the microstructure and to identify the phases formed. It is shown that smooth, deep, and crack-free nitride layers of a surface hardness ranging between 500 and 800HV can be obtained by controlling the processing parameters. Cracks are present in the sample processed at slow scanning speed and high laser power. Dilution of the nitrogen gas with argon gas leads to a crack-free nitride layer at the expense of a reduction in surface hardness. Slow scanning speeds lead to the formation of a deep and hard surface layer, and increasing the nitrogen flow rate results in a rough surface with a slight increase in hardness. (c) 2007 Elsevier Ltd. All rights reserved.


Addresses: Garyounis Univ, Fac Engn, Dept Mech Engn, Benghazi, Libya

Omar Al Mukhtar Univ, Dept Mech Engn, Al Bythaa, Libya

Garyounis Univ, Fac Engn, Dept Ind Engn, Benghazi, Libya

Reprint Address: BENYOUNIS, KY, GARYOUNIS UNIV, FAC ENGN, DEPT MECH ENGN, PO BOX 1308, BENGHAZI, LIBYA

Author's E-mail: jhabboud@yahoo.com

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205

Author(s): Beal, VE (Beal, V. E.); Erasenthiran, P (Erasenthiran, P.); Hopkinson, N (Hopkinson, N.); Dickens, P (Dickens, P.); Ahrens, CH (Ahrens, C. H.)



Title: Scanning strategies and spacing effect on laser fusion of H13 tool steel powder using high power Nd : YAG pulsed laser

Source: INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH, 46 (1): 217-232 2008

Abstract:

Layered manufacturing technologies have been used to produce complex parts of diversified materials through different physical/chemical manufacturing principles. Nevertheless only a few materials are commercially available to build parts suitable for engineering applications. In this paper, the powder fusion of H13 tool steel is investigated. A high power Nd:YAG pulsed laser source on a CNC machine was used to fuse the powder, layer by layer, building solid cubes for further analysis. Four different laser vector scanning strategies were evaluated by comparing the results of porosity and layer distortion. The complexity of the laser/powder interaction shows that a complex strategy must be used to avoid porosity and distortion.


Addresses: Univ Fed Santa Catarina, Dept Engn Mecan, POSMEC, BR-88040900 Florianopolis, SC, Brazil

Univ Loughborough, Wolfson Sch Mech & Mfg Engn, Rapid Mfg Res Grp, Loughborough LE11 3TU, Leics, England

Reprint Address: BEAL, VE, UNIV FED SANTA CATARINA, DEPT ENGN MECAN, POSMEC, CAIXA POSTAL 476,CAMPUS UNIV, BR-88040900 FLORIANOPOLIS, SC, BRAZIL

Author's E-mail: valterbeal@gmail.com


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