高功率光纤激光器中ASE噪声的测量方法（英）

高峰值功率脉冲光纤激光器在激光雷达系统中有着广泛的应用。然而,光纤激光器中放大自发辐射噪声（ASE）严重影响了系统的探测性能。提出一种测量高峰值功率脉冲光纤激光器中ASE噪声的方法。在该方法中,首先对高峰值功率的激光脉冲衰减,然后在时域分别测量和计算ASE噪声和激光脉冲的相对能量。给出了光纤激光器在驱动电流分别为6 A,7 A和8 A时衰减后的ASE噪声廓线以及ASE噪声占激光脉冲能量的比例。     

Mercury and beyond: diode-pumped solid-state lasers for inertial fusion energy

We have begun building the Mercury laser system as the first in a series of new generation diode-pumped solid-state lasers for inertial fusion research. Mercury will integrate three key technologies: diodes, crystals and gas cooling, within a unique laser architecture that is scalable to kilojoules and megajoule energy levels for fusion energy applications. The primary near-term performance goals include 10% electrical efficiencies at 10 Hz and 100 J with a 2–10 ns pulse length at 1.047 μ m wavelength. When completed, Mercury will allow rep-rated target experiments with multiple chambers for high energy density physics research.     

用于高功率激光器的光学元件（特邀）

激光的出现对大多数实际应用系统中的光学元件的性能、质量及其加工提出了严格的要求。激光的高功率性能由3个不同的过程决定：其一是对入射光辐射的吸收（主要由各种吸收机制决定）;其二是由热学性能决定的温度升高和响应;其三是元件的热光学和热机械响应,如变形、应力断裂等。在设计效率高、紧凑性好、可靠性好的应用于不同领域的高功率激光系统时,需要考虑不同运行条件下的脉冲、连续波、不同占空比的重复频率或突发模式等。     

脉冲储能型重复频率Yb:YAG片状激光放大器ASE效应研究

探讨了脉冲储能型重复频率片状Yb:YAG激光放大器抽运过程中的自发辐射放大（ASE）效应和能量提取过程.在Yb³⁺离子抽运动力学的基础上,建立了抽运过程中的自发辐射放大模型,计算了Yb:YAG晶体中三维含时储能密度分布和全片可提取能量.讨论了不同介质尺寸、掺杂浓度及厚度、介质温度参数下,自发辐射放大对储能的影响.给出了较为优化的设计,将有助于基于Yb激光材料的大能量二极管抽运的固体激光器设计. 关键词： 脉冲储能 Yb:YAG激光放大器 自发辐射放大（ASE）     

激光二极管泵浦的重复频率大能量低温Yb:YAG激光器设计

为实现重复频率大能量激光输出,基于Yb:YAG激光介质低温下良好的热特性和激光特性,设计了12kW高功率激光二极管(LD)阵列泵浦的V型腔低温Yb:YAG激光器(液氮温度)。对于泵浦耦合系统和散热结构两个关键点,分别使用光线追迹方法和有限元方法进行了分析,提出了楔形真空窗口和低温热管等解决方案。模拟结果表明,该设计的激光器热效应较低,可实现重复频率大能量输出。     

High power repetitive TEA CO2 pulsed laser

A high power repetitive spark-pin UV-preionized TEA CO₂ laser system is presented. The discharge for generating laser pulses is controlled by a rotary spark switch and a high voltage pulsed trigger. Uniform glow discharge between two symmetrical Chang-electrodes is realized by using an auto-inversion circuit. A couple of high power axial-flow fans with the maximum wind speed of 80 m/s are used for gas exchange between the electrodes. At a repetitive operation, the maximum average output laser power of 10.4 kW 10.6 ??m laser is obtained at 300 Hz, with an electro-optical conversion efficiency of 15.6%. At single pulsed operation, more pumping energy and higher gases pressures can be injected, and the maximum output laser energy of 53 J is achieved.     

大功率脉冲TEA CO2激光器配气比对输出的影响

大功率脉冲TEA CO2激光器的放电腔在不同工作气压和不同配气比例条件下对激光器输出能量和电光转换效率均有较大影响,因此,通过充气压力从30kPa到60kPa的改变和配气比例CO₂:N₂＝1:1到CO2:N2＝1:4的变化,可以改变激光器的输出能量,提高激光器电光转换效率。实验结果表明：当CO2:N2的配气比例为1:3时,激光器输出的电光转换效率存在最佳点。在最佳配气比例CO2:N2:He＝3:9:28,总气压40kPa和注入激励电能保持不变的情况下,激光器单脉冲放电时的输出能量为24.6J;激光器高重复频率放电运转时的电光转换效率达16.4％。激光器的最高放电频率可以达到500Hz并且连续稳定运行工作。     

一种基于增益调制技术的全光纤化脉冲Yb光纤激光器

以波长为975 nm的半导体激光器作为泵浦源,周期性地脉冲泵浦一个包含Yb掺杂光纤和光纤光栅对的Yb光纤激光器,实现了基于增益调制技术的全光纤化高功率Yb光纤激光器的稳定脉冲输出.在50 kHz重频下,采用20 W的泵浦功率和2.4 μs的泵浦脉冲宽度,获得了1 060 nm波长脉冲宽度仅100 ns的稳定脉冲激光输出,单脉冲激光能量约为20 μJ.以此作为脉冲激光种子进行功率放大,获得了性能稳定的全光纤结构高功率脉冲激光输出,放大后单脉冲能量超过200 μJ,激光放大器斜率效率达到60%.     

1 mJ, 500 kHz Nd:YAG/Nd:YVO<Subscript>4</Subscript> MOPA laser with a Nd:YAG cavity-dumping seed laser

We report a high-repetition-rate, high-pulse-energy master oscillator power amplifier (MOPA) laser system, in which the seed laser from the Nd:YAG rod-based oscillator cavity dumped at 500 kHz, was scaled up consecutively by a four-stage Nd:YVO₄ preamplifier and a two-stage Nd:YAG zigzag slab main amplifier. The laser pulsed output with the average power of 510 W was achieved, with the efficiency extraction of 26.6% at the main amplifier stage and the single-pulse energy of 1.02 mJ.     

High-power pulsed diode-pumped Er:ZBLAN fiber laser

We report on the operation and performance of a gain-switched Er:ZBLAN fiber laser based on an active pulsed diode pump system. The produced laser pulses offer high peak powers while retaining the high average powers and efficiency of the cw regime. The measured pulse duration was about 300 ns and nearly independent of the pump repetition frequency. The maximum obtained 68 W of peak power is the highest reported, to our knowledge, for diode-pumped Er:ZBLAN fiber lasers, and the 2 W of average power at the repetition frequency of 100 kHz is 2 orders of magnitude higher than previously reported average power in a pulsed regime. The obtained slope efficiency was 34%.     

Frequency doubling of narrow-linewidth pulsed fiber laser

A pulsed master oscillator power amplifier system is constructed using a double-cladding polarized Ybdoped fiber and an all-fiber Q-switched narrow-linewidth pulsed laser used as seed laser.This system has a high repetition rate and provides a nanosecond pulsed laser with a narrow linewidth and linear polarization.Moreover,it generates amplified radiation with up to 14 W of average power,narrow linewidth(full-width at half-maximum is smaller than 0.12 nm),linear polarization at 1 080-nm wavelength,repetition rate of 51 kHz,and pulse duration of approximately 50 ns.Based on this pulsed amplified radiation,3.5 W of green laser,with an optical-to-optical efficiency of 27.3%,is obtained via single-pass frequency doubling using a noncritical phase matching KTP crystal.     

高功率重频电化学HF激光器(英文)

研制了高功率、高重频非链式HF激光器,并研究了脉冲模式和重频模式下在SF6的混合气中增加电极边缘电场强度而不使用其它措施即可实现自持体引发放电的可能性,得到了重复频率为20 Hz,脉冲能量为67 J,转换效率为3%的激光输出。     

高功率重频电化学HF激光器(英文)

研制了高功率、高重频非链式HF激光器,并研究了脉冲模式和重频模式下在SF6的混合气中增加电极边缘电场强度而不使用其它措施即可实现自持体引发放电的可能性,得到了重复频率为20 Hz,脉冲能量为67 J,转换效率为3%的激光输出。     

Time-resolved photo-electron spectroscopy on mass-selected metal clusters using a regenerative femtosecond amplifier up to 100 Hz

A femtosecond photo-electron experiment is described which provides excellent conditions for measuring time-resolved photo-electron spectra of free, monodispersed cluster anions using repetition rates up to 100 Hz. Cluster anions are synthesized in an electric arc and subsequently cooled in a helium carrier gas. A time-of-flight spectrometer is used for mass separation of the negatively charged clusters. The kinetic energy of the photo-electrons is analyzed by a magnetic-bottle time-of-flight spectrometer, which guarantees a maximum collection efficiency. Femtosecond laser pulses are generated by a seeded regenerative Ti:Sa amplifier, which is externally pumped with the second harmonic of a diode-pumped solid-state Nd:YAG laser. A retroreflector mounted on a computer-controlled translation stage serves as a reproducible time delay of the probe pulse. The high energy output of the laser pulses (∼3 mJ) in combination with the variable repetition rate and the high stability of the amplified pulses provide excellent conditions for recording pump-probe photo-electron spectra of mass-separated cluster anions even at the fairly low ion density of pulsed plasma cluster sources. First results on the electron dynamics of the Pt₃ ^- cluster demonstrate the reliability of the whole system. Further experimental investigations will concentrate on electron-relaxation processes in transition- and noble-metal clusters as well as on the nuclear and transition-state dynamics of chemically reacted adsorbate clusters. Received: 7 January 2000 / Published online: 7 August 2000     

高效转换的大功率皮秒脉冲激光器

本文描述我们设计的带抗共振环(ARR)的对撞脉冲锁模(CPM)非稳腔Nd:YAP和Nd:YAG激光器,该激光腔结合了CPM腔脉宽窄、工作稳定和非稳腔输出能量高的特点,是一理想的高功率激光器同时选择了KTP、BBO和LBO等优良非线性晶体作为腔内倍频元件,实现高效倍频转换获得×10mJ和5GW/cm²的高能量和高功率绿光皮秒脉冲输出,倍频转换效率高达(50～70)%.     

New efficient laser dye for pulsed and CW operation in the UV

A new laser dye for pulsed and cw operation has been synthesized which can be tuned from 362 nm up to 412 nm. For pulsed excitation with a XeCl excimer laser an energy conversion of 18.5% has been measured at the tuning maximum of the dye; this is the highest efficiency for any known dye in the UV. For cw operation a low laser threshold and a goof efficiency have been observed. The range of tuned cw dye lasers is extended by 30 nm to shorter wavelengths. The dye shows high photochemical stability even at high pump laser power.     

Yb:CNGG有源反射镜的多程放大特性研究

高效、高平均功率固体纳秒脉冲激光器在光电对抗、激光雷达、材料改性、激光加工等诸多领域发挥着越来越重要的作用,然而目前大多数纳秒级高平均功率激光器采用Yb:YAG或掺Nd材料作为增益介质,材料的高饱和通量或低储能密度会导致激光器放大链路复杂,体积庞大。研究比较了一种更适合作为高平均功率、高脉冲能量激光器增益介质的无序石榴石晶体Yb:CNGG,研究了有源反射镜结构中Yb:CNGG的多程增益特性,分析了放大过程并建立了多程放大模型,在一定的泵浦条件下优化了晶体参数以实现更好的储能。开展了双程放大实验,在15 kW/cm²的泵浦功率密度下得到了1.53倍的增益。对比Yb:CNGG晶体与Yb:YAG晶体的多程放大能力,在相同的晶体参数和泵浦条件下,在入射能量1 mJ时Yb:CNGG可实现2.11 J的脉冲能量输出,优于Yb:YAG晶体1.41 J的能量输出。     

Sheet metal welding using a pulsed Nd: YAG laser-robot

This paper presents a pulsed Nd: YAG laser-robot system for spot and seam welding of mild steel sheets. The study evaluates the laser beams behaviour for welding, and then investigates pulsed Nd: YAG laser spot and seam welding processes. High pulse power intensity is needed to initiate the key-hole welding process and a threshold pulse energy to reach full penetration. In seam welding, a weld consists of successive overlapping spots. Both high pulse energy and high average power are needed to keep the key-hole welding going. A 70% overlap is used to define overlapping spot welding as seam welding and to optimize process parameters because a high tensile strength joint compatible with the strength of the base material can be obtained when the overlap is ≥70%; at the same time a smooth seam with full penetration is obtained. In these cases, the joints in pulsed Nd: YAG laser welding are comparable in strength to those obtained with CO₂ laser welding. Robot positioning and motion accuracies can meet the demands of Nd: YAG laser sheet metal welding, but its cornering accuracy affects the welding processes. The purpose of the study is to evaluate the YAG laser-robot system for production in the automotive industry.     

Two－Side Electron Beam Pumping System For Hundred－Joule－Level KrF Excimer Laser

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A search for laser heating of a sonoluminescing bubble

Thermodynamic arguments show that a sonoluminescing bubble that acts as a black body can absorb energy from a high power, pulsed laser beam. The mechanism for increasing the temperature of a sonoluminescing bubble is discussed and experiments with a frequency doubled, pulsed Nd:YAG laser are described. A bound for the amount of radiation absorbed is given as no evidence for heating was found at the low radiation intensity employed in the experiments.