液体介质快脉冲电压下击穿特性研究

设计了液体介质快脉冲击穿试验装置和电压电流测量系统，研究了重复频率、电极形状及电极间距与介质击穿场强、击穿电压和击穿时延等击穿特性参数的关系，比较了变压器油、十二烷基苯、蓖麻油三种典型液体绝缘介质在直流及快脉冲电压作用下的绝缘性能。结果表明:短脉冲持续时间下液体绝缘材料有异常高的击穿场强；重复脉冲串作用下的击穿场强比单个脉冲下明显减小，重复频率2 kHz时击穿场强减小了约30％；电极头半径大小对击穿也有影响，半径R＝5 mm时，击穿电压最高；击穿时延随击穿场强减小而变长，在其他条件相同的情况下，测得击穿时延随机波动；蓖麻油的快脉冲电压绝缘性能最好，变压器油次之。     

Compact corner-pumped Nd:YAG/YAG composite slab laser

Corner-pumping is a new pumping scheme in diode-pumped all-solid-state lasers, having such advantages as high pump efficiency, favorable pump uniformity and low cost. Compact corner-pumped Nd:YAG/YAG composite slab lasers at 1064 nm with low or medium output powers and high efficiency are demonstrated in this paper. Combined with intracavity frequency doubling by a LBO crystal, a corner-pumped Nd:YAG/YAG composite slab 532 nm green laser with a stable output is realized successfully. The experimental results show that corner-pumping can reduce laser costs greatly, release the thermal effects of slab crystals and improve the output beam quality, and that the new pumping scheme is feasible in the design of diode-pumped all-solid-state lasers with low or medium output powers.     

1.8 mJ高倍率Nd:YAG板条皮秒激光放大器

设计了一种高倍率的固体皮秒脉冲激光放大器,采用Nd:YAG板条作为激光增益介质。借助板条结构的角度选通结构,搭建了板条五通放大系统,实现了对注入皮秒脉冲激光的高倍率放大。种子源工作在脉冲模式,放大器泵浦源在连续模式工作。皮秒光纤激光器可以在不同的重复频率下工作,脉冲宽度为13.4 ps。种子光经过隔离和耦合系统之后,注入板条的单脉冲能量为25 nJ。当种子源工作重复频率为24.46 MHz时,板条放大器输出平均功率377 W,单脉冲能量15.5 μJ;当种子源工作重复频率为49.8 kHz时,板条放大器输出平均功率89 W,单脉冲能量1.8 mJ,峰值功率为134 MW,放大倍率达到7.2×104。     

High-power high-stability Q-switched green laser with intracavity frequency doubling of diode-pumped composite ceramic Nd:YAG laser

We successfully obtain high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal. By use of a composite ceramic Nd:YAG rod and a type-II high gray track resistance KTP (HGTR-KTP) crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.     

A high-power high-stability Q-switched green laser with intracavity frequency doubling using a diode-pumped composite ceramic Nd：YAG laser

We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal. By using a composite ceramic Nd:YAG rod and a type-II high gray track resistance KTP (HGTR-KTP) crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.     

二极管侧泵浦单横模1kHz电光Q开关激光器

 本文介绍了二极管侧泵浦Nd:YAG板条1kHz重复频率Q开关激光器的研制,实验获得最大单脉冲能量0.712mJ,脉宽小于10ns的输出。对Nd:YAG板条进行了三种冷却方式的比较实验,实验证明DPL在高重复频率工作时,激光介质的热效应是影响高重复频率工作的激光器效率的重要因素。     

Experimental Study of a Diode-Pumped Nd:YAG Slab Laser Amplifier

We demonstrate a laser-diode-pumped Nd:YAG slab amplifier with dimensions of 7×35×138.2 mm. The fluorescence is homogeneously distributed in the Nd:YAG amplifier, and a stored energy of 3.2 J can be achieved at 1,500 W pump power. For a repetition frequency of 200 Hz, 25 μJ injection polarized seed light, and 1,500 W pump power, the small signal gain reaches 12.66. At the same repetition frequency, 0.4 mJ with 27 ns bandwidth of injected seed-light energy and a 6×26 mm aperture, the output energy reaches 1.071 J. The extraction efficiency is 33.46% after four-pass amplification. An energy amplification from millijoules to joules is realized for the injected laser beam.     

激光二极管列阵泵浦的位相共轭板条YAG激光放大系统

采用新型的微通道冷却半导体激光二极管列阵泵浦ＹＡＧ激光振荡器及板条ＹＡＧ放大器，文中用ＣＣｌ４受激布里渊散射作位相共轭镜，使激光在板条放大器中作多通放大，获得了高重复率下小于１．５倍衍射极限的高质量１．０６μｍ的激光输出，其脉冲宽度为１５ｎｓ，平均功率为１８０Ｗ。     

High efficiency diode-pumped slab oscillator and amplifier for space-based application

The design and performance of conduction-cooled, laser diode-pumped oscillator and amplifier slab laser featuring high efficiency, high pulse energy and high beam quality for space-based application are reported. The oscillator was a diode-pumped Q-Switched Nd:YAG slab laser using unstable resonator, and the amplifiers were two zig-zag Nd:YAG slabs based on a side-pumped slab geometry. A near diffraction-limited output of 450 mJ in a 10 ns pulse at a repetition rate of 20 Hz was obtained, corresponding to an optical-to-optical conversion efficiency of over 20%.     

千瓦级半导体抽运的固体热容板条激光器

报道了千瓦级激光二极管面阵抽运固体热容激光器的理论与实验研究,分别采用Nd∶YAG单板条和双板条串接的热容激光器,利用热容激光器的理论计算模型计算了在一定的工作时间内激光输出特性,并进行了实验验证。实验中采用的晶体尺寸均为59mm×40mm×4.5mm,对单板条进行抽运时平均功率大约为5.6kW,双板条串接时为11.2kW,重复频率为1kHz,占空比为20%。实验中观察了1s的工作时间内脉冲能量输出的波动情况,单板条时单脉冲能量输出最大为1.3J,在1 s后单脉冲能量输出下降到开始的70%左右,而双板条串接时单脉冲能量输出最大为2.06J,在1s后单脉冲能量输出下降到开始的50%左右,对单块晶体采用通水冷却的准热容热管理模式能有效地降低其热效应。     

A Compact 532-nm Source by Frequency Doubling of a Diode Stack End-Pumped Nd：YAG Slab Laser

A near-diffraction-limited green source is generated at 1 kHz repetition rate by frequency doubling of a diode stack end-pumped electro-optically Q-switched Nd：YAG slab laser. We obtain 9. 7mJ green light with pulse width of 12.2ns at a repetition rates of i kHz. The pump to green optical conversion efficiency is 12.9%. The energy pulse stability at 532nm is about 0.8%.     

脉冲LDA侧面泵浦大能量Nd:YAG激光器时变热效应分析

建立了激光二极管阵列(LDA)侧面泵浦棒状Nd:YAG增益介质时变热效应理论计算模型。采用有限元Ansys软件模拟分析了脉冲LDA侧面泵浦大能量固体激光器的时变热效应特性。研究结果表明,所研究的脉冲LDA侧面泵浦大能量Nd:YAG激光器热效应具有时变特性,介质横截面内中心点处的稳态温度场分布随时间呈锯齿形周期变化,锯齿形变化频率为LDA泵浦频率,脉冲LDA泵浦参数对介质稳态温度场分布有较大影响。分析和计算了介质内热梯度、应力双折射以及激光晶体端面效应等导致的晶体热透镜焦距。计算表明,介质的热焦距主要来源于介质内温度梯度引起的热透镜焦距。     

二极管侧泵浦板条固体激光器的热效应研究

 用有限差分法对二极管侧泵浦板条激光介质的温度分布作了数值计算。在此基础上, 对不同条件下二极管侧泵浦激光器的最佳冷却方案进行了研究。用峰值功率为100W, 工作频率为100Hz的二极管泵浦Nd:YAG板条作了实验研究, 所得结果与计算符合较好。     

激光二极管端面泵浦的调Q内腔倍频Nd：YAG激光器

报道了用两个１．５Ｗ激光二极管偏振耦合端面泵浦的声光调Ｑ内腔倍频Ｎｄ：ＹＡＧ激光器。输出５３２ｎｍ绿光重复频率１ＫＨｚ时，最大峰值功率为２．２３ＫＷ，最窄脉宽为１８ｎｓ，平均功率４０ｍＷ。最高重复频率３０ＫＨｚ。重复频率１５ｋＨＺ时，最高平均率１２８ｍＷ。对声光调Ｑ内倍频Ｎｄ：ＹＡＧ激光器的动态特性进行了理论分析及计算。     

Timing-jitter reduced high-repetition-rate Q-switched Nd:YVO<Subscript>4</Subscript>/Cr<Superscript>4+</Superscript>:YAG micro laser with low pump power

We report a high repetition rate Q-switched Nd:YVO₄/Cr⁴⁺:YAG micro laser with small pump power. Unwanted defects in pulse train, which are inherently large in passively Q-switched laser, was simply minimized by controlling temperature of Nd:YVO₄/Cr⁴⁺:YAG medium. When T ₀ = 90% Cr⁴⁺:YAG and R _OC = 90% output coupler were used, Q-switched Nd:YVO₄/Cr⁴⁺:YAG micro laser showed the optimum output; maximum output power of 58 mW, optical-to-optical efficiency of 9.1%, repetition rate of 1.1 MHz, and pulse width of 57 ns were achieved with 640 mW pumping. MHz-order repetition rate in Nd:YVO₄/Cr⁴⁺:YAG Q-switched laser with low pumping (<1 W) is the highest value to the best of our knowledge.     

Emission Spectrochemical Analysis of Metals Using a Nitrogen Laser

Comparative studies of the possibilities of using pulsed nitrogen and Nd:YAG lasers for emission spectrochemical analysis of copper-zinc alloys have been made. The nitrogen laser developed on the basis of the commercial excimer laser provided an energy of radiation pulses of 5 mJ with an error of less than 0.8% at a repetition frequency of 100 Hz. The high stability and the high pulse repetition frequency of the nitrogen laser were attained due to the additional high-speed fan inside the laser chamber, which provided agitation and circulation of the gas mixture. It has been shown by experiment that the spectral emission of the plasma formed by means of the nitrogen laser is characterized by intensity fluctuations with a root-mean-square deviation of 1.4%, whereas in the case of using an Nd:YAG laser it was 14.3%. The advantages of the nitrogen laser that are due to the increased signal-to-background ratio and the suppression of the selective evaporation effect have been revealed.     

Cross-relaxation and spectral broadening of gain for Nd/Cr:YAG ceramic lasers with white-light pump source under high-temperature operation

Spectral broadening of the fluorescence of a Nd/Cr:YAG ceramic at the 1064 nm lasing wavelength was observed, and the amplification properties at a high temperature were investigated by considering cross-relaxation. These ceramics are promising for use as a solid-laser material pumped with solar or lamp light. It has been found that whenever the temperature of a laser medium is high and a spectral shift occurs, a high small-signal gain remains owing to the broad spectral band and the cross-relaxation. This optical property is remarkably different from that of a Nd:YAG laser. For a conventional Nd:YAG laser, the bandwidth at 1064 nm is 0.45 nm, and a reduction in small-signal gain occurs at a temperature of 373 K because the spectral peak shift is 0.005 nm/K. However, for the Nd/Cr:YAG ceramic, the bandwidths are 1.2 and 1.9 nm in the case of 0.1% Cr ion doping and 3% Cr ion doping, respectively, owing to the existence of excited Cr ions and the shortening of the effective Nd ion coherence time. It is prospected that the laser medium can be used at a high temperature of 600 K.     

Efficient corner-pumped Nd:YAG/YAG composite slab laser

A corner-pumped type is a new pumping type in the diode-pumped all-solid-state lasers, which has the advantages of high pump efficiency and favourable pump uniformity. A highly efficient corner-pumped Nd:YAG/YAG composite slab laser is demonstrated in this paper. The maximal continuous-wave output power of the 1064~nm laser is up to 18.57~W with a slope efficiency and an optical-to-optical conversion efficiency of 44.9{\%} and 39.8{\%}, respectively. Inserting an acousto-optic $Q$-switch in the cavity, the highest average output power of the quasi-continuous wave 1064~nm laser of 6.73~W is obtained at a repetition rate of 9.26~kHz. The experimental results show that a corner-pumped type is a kind of feasible schedules in the design of diode-pumped all-solid-state lasers with low or medium output powers.     

Stable single-mode operation of injection-seeded Q-switched Nd:YAG laser by sine voltage modulation

Based on the modified ramp and fire technique, a novel injection seeding approach with real-time resonance tracking is successfully demonstrated in a single-frequency Nd:YAG pulsed laser. Appling a high-frequency sinusoidal modulation voltage to one piezo actuator and an adjustable DC voltage to another piezo actuator for active feedback, single-mode laser output with high-frequency stability is obtained, and the effect of the piezo hysteresis on the frequency stability can be eliminated for a laser diode pumped Q-switched Nd:YAG laser at a repetition rate of 400 Hz.     

Conductively cooled 250-Hz single frequency Nd：YAG laser

A conductively cooled, laser diode （LD） end-pumped, injection-seeded single frequency Nd：YAG laser is designed and impleinented. The laser utilizes Nd：YAG rod as gain medium and compact dual-endpumping arrangement using two fiber-coupled LDs with a maximum output of 150 W. The optimized ramp-fire technique is applied to build reliable single longitudinal mode oscillating. The laser is capable of producing a 10-raJ Q-switched pulse with 13-ns pulse width at 1064 nm at a pulse repetition rate of 250 Hz. The output beam qualities M2 of approximately 1.19 and 1.22 in horizontal and vertical directions are detected, respectively.