用于ps脉冲放大的大口径放电泵浦KrF激光器

 以简单的火花间隙作为放电开关，建立了一种用于ps脉冲激光放大的大口径放电泵浦KrF准分子激光器。该激光器的有效增益口径截面为4cm×3cm，在自由运转情况下最大激光输出能量为1.3J，脉宽20ns。用作ps放大器时，利用光学偏振放大方式获得了激光能量140mJ，脉冲宽度10ps的激光输出。利用XeCl激光泵浦的染料激光作为探针测量了不同放电条件下和不同气分比条件下激光的增益和吸收系数。     

紫外超短脉冲激光的单次测量

 利用瞬态光栅衍射法研制了一台单次频率分辨光学开关激光参数测量仪,可以对脉宽范围在10 ps以内的紫外超短脉冲激光进行单次测量。利用该仪器对重复频率为10 Hz的放电泵浦和单次运行的电子束泵浦KrF准分子激光器的输出脉冲分别进行了单次测量,结果表明：对于放电泵浦,当系统工作在零啁啾附近时,脉冲波形和光谱分布较规则,相位分布起伏较小,当系统偏离零啁啾状态时,脉冲波形和光谱分布不再规则,并且相位分布为抛物线结构;对于单次运行的电子束泵浦,脉冲波形具有多峰结构,光谱具有复杂的调制,脉宽约为2 ps,带宽约为1.3 nm,相位分布为抛物线结构。     

脉冲功率技术在短波长气体激光器中的应用

 介绍了脉冲功率技术在离子准分子、准分子和软X射线激光研究中的应用情况。给出了三种激光产生对泵浦源电学参数的要求,并给出实现这些电学参数的实验装置以及实验装置的性能指标。在软X射线激光研究方面,利用10级Marx发生器和Blumlein传输线,建立了最高电流峰值40 kA,前沿为26.6 ns的毛细管放电装置,并实现了46.9 nm激光输出。建立了输出电压600 kV、输出电流20 kA的电子束装置,并作为泵浦源实现了离子准分子光腔效应。为了泵浦S2准分子,采用横向放电方式和低电感放电回路,实现了电压脉冲宽度为29.2 ns的窄脉冲放电。     

紫外超短脉冲激光放大过程中脉宽压缩的方案设计

采用放电泵浦KrF准分子激光放大器放大波长为248.4nm的紫外超短脉冲激光。对于能量为0.7mJ、脉宽为550fs的输入脉冲,在光束直径保持10mm不变的条件下,能量放大到15mJ,脉宽展宽到1200fs。为了压缩输出脉冲宽度,分析了群速度色散和自相位调制效应对脉宽展宽的影响。利用棱镜对,采用4种不同的实验方案对脉冲引入负的线性频率啁啾,以补偿KrF准分子激光放大器CaF2窗镜中的群速度色散和自相位调制对脉冲引入的正的线性频率啁啾。结果表明:在放大器之前放置棱镜对的方式可以在保持输出脉冲能量为15mJ的同时,在棱镜对间距为110cm的条件下,将输出脉冲宽度压缩到370fs,输出波长为248.4nm、带宽为0.4nm。     

短谐振腔准分子激光输出的脉冲特性研究

用腔长为7.5cm～20cm的紫外光预电离Blumlein横向放电泵浦XeCl准分子激光器可产生半宽为1.8ns～5ns的短脉冲输出。速率方程的计算机模拟所给出的激光振荡初始尖峰和实验结果做了比较。     

可控制变频率微片激光器

 用20 W光纤耦合LD作为泵浦光源，对Nd^{3+sup>:YVO_{4/sub>微片进行了增益开关实验，获得了可控制变重复频率（1 Hz～25 kHz）的调Q激光输出。输出脉冲激光的宽度为16 ns，输出的峰值功率在几W。从速率方程出发进行了增益开关理论研究，通过数值解，分析了输出激光特性：当泵浦电流高于产生单脉冲的电流时，增加泵浦电流将在一个泵浦脉宽中出现多个激光脉冲输出；增加泵浦脉宽，将在一个泵浦脉宽中出现多个激光脉冲输出，泵浦脉宽越大，子脉冲个数越多；当增加重复频率时，输出与泵浦激光重复频率完全一致的激光脉冲，但也将在一个泵浦脉宽中出现多个激光脉冲输出。}}     

利用脉冲负反馈压缩准分子激光脉冲

分析了准分子激光脉冲在放大过程中的展宽现象。将饱和开关技术应用于放电泵浦激光器放大腔的放大压缩,发展了脉冲负反馈饱和压缩技术。利用该技术在天光一号系统前端LPX-150激光器上成功获得能量100 mJ、脉宽10 ns的脉冲输出,其空间分布均匀性保持在3%以内。这证明该技术可与无阶梯诱导非相干技术联合使用,在保证光束均匀性基础上进行脉冲压缩。     

利用脉冲负反馈压缩准分子激光脉冲

 分析了准分子激光脉冲在放大过程中的展宽现象。将饱和开关技术应用于放电泵浦激光器放大腔的放大压缩,发展了脉冲负反馈饱和压缩技术。利用该技术在天光一号系统前端LPX-150激光器上成功获得能量100 mJ、脉宽10 ns的脉冲输出,其空间分布均匀性保持在3%以内。这证明该技术可与无阶梯诱导非相干技术联合使用,在保证光束均匀性基础上进行脉冲压缩。     

放电泵浦ArF准分子激光动力学模拟与参数分析

利用一维流体模型研究了放电泵浦ArF准分子激光动力学过程,得到气体放电过程中放电电路的电流电压波形,得到了电子密度、光子密度、电场的时空分布特性,分析了放电参数对激光输出的影响。结果表明,电路参数、工作气压、氟气比例均对激光输出有显著影响,放电电路中的电感值对输出影响较小,参数范围较广,而电路中较小的峰化电容值有利于获得长脉冲输出,气压太大或太小都会使输出能量降低,同样,氟气比例太大或太小也会使输出能量降低。     

C-C转移放电泵浦XeCl准分子激光器能量沉积特性的分析

本文报道了一台使用UV自动预电离,C-C转移放电泵浦的XeCl准分子激光器,并且以激光器放电信号和输出激光信号的同时测量结果为依据,分析了激光器放电的能量沉积过程.可为设计同类型准分子激光器提供一些参考数据.     

Performance of optical fibers for transmission of high-peak-power XeCl excimer laser pulses

The simple and efficient fiber delivery of 5-ns pulses from a XeCl excimer laser operating at a wavelength of 308 nm is demonstrated. The coupling scheme uses all of the output energy of the XeCl excimer laser and benefits from a simple and easy-to-adjust fiber coupling. Experiments on the 308-nm fiber delivery for more than 2.5 million laser pulses of 8-ns pulse width (FWHM) and up to 8-mJ stabilized pulse energy are performed. The long-time pulsed UV laser transmission is found to be different for individual samples of optical fibers that perform very similarly in low-intensity UV light applications. For applications with strict demands on the long-time stability, a critical evaluation of the fiber performance with the 308-nm laser under operating conditions is necessary. Measurements between 1 and 200 Hz show a negligible dependence of the fiber delivery performance on the repetition rate of the transmitted laser pulses. PACS 42.55.Lt; 42.81.Cn; 07.69.Vg     

Simple generation of high-power,picosecond, tunable excimer laser pulses

A single excimer laser (a modified commercial oscillation-amplifier combination) is used to pump a dye laser generating a single ps pulse at twice the excimer wavelength and to amplify the frequency-doubled pulse to high peak powers. With XeCl at 308 nm an output pulse energy of 10 mJ with <5 ps pulse width was achieved with <5% ASE energy.     

80 A/cm2 electron beams from metal targets irradiated by KrCl and XeCl excimer lasers

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.On leave from Institute of General Physics, Moscow, Russia     

空气呼吸模式激光推进实验研究

介绍了利用实验室自行研制的紫外预电离TEA CO2激光器进行的金属线导引抛物面光船垂直推进实验,脉冲能量60J时,冲量耦合系数可达到390N／MW。这一结果远高于Myrabo和Schall等人用电子束维持放电激光器获得的空气呼吸模式冲量耦合系数。还介绍了利用光电二极管探测He-Ne激光束,He-Ne激光束强度变化反映了空气呼吸模式激光推进时空气密度变化,进而观察了激光束照射光船后空气扰动的情况。     

Continuous operation up to 3 kHz in a discharge-pumped XeCl excimer laser

Continuous operations at a high repetition rate up to 3 kHz for discharge-pumped XeCl excimer laser are presented. The dependence of the clearing ratio on laser-gas pressure and input energy densities is studied. It was found that suitable laser-gas pressures minimize the clearing ratio for various input-energy densities. It is also shown that few density disturbances in the discharge region are induced by gas heating in a discharge-pumped XeCl excimer laser with low input-energy density     

Comparison of characteristics of an x-ray preionized XeCl laser, pumped by water transmission line and low inductance capacitor bank

With a high uniformity of x-ray preionization, a long pulse duration and a high specific energy (9 J l^-1), an XeCl excimer laser output has been obtained by using a compact low inductance capacitor bank as the laser excitation circuit. The superior features of the low inductance capacitor bank (LICB) compared to the water transmission line (WTL) are attractive for repetitively pulsed XeCl excimer lasers.     

Performance improvement of an x-ray preionized XeCl laser of very small discharge volume

Increasing the preionization electron density is found to be an effective method for improving the output performance of discharge-pumped excimer lasers at high gas pressures when the power-supply voltage becomes a limiting factor. In a small volume (2 cm³), x-ray preionized discharge, orders of magnitude improvement in XeCl laser power output (up to 400 kW) and pulse energy (up to 26 mJ) over previously reported results have been found possible using this method. Modifications to the low energy x-ray source and discharge system leading to these improvements are described. Various laser output characteristics are also presented and discussed.     

准分子激光等离子体开关控制脉宽研究

 利用准分子激光等离子体技术,在紫外预电离XeCl准分子激光器上获得了最短1.58 ns的短脉冲激光输出。实验中分析了聚焦到薄膜表面的光束能量密度对所产生的等离子体密度的影响,并对不同等离子体密度及维持时间情况下脉冲压缩效果进行了讨论,给出了激光器谐振腔在稳定腔及非稳腔两种工作方式下的实验结果。激光器在稳定腔工作时,脉宽可压缩至2.87 ns;采用非稳腔结构时,在脉冲能量不变情况下减小聚焦光斑面积,提高入射到薄膜表面的能量密度,得到了最短1.58 ns的短脉冲激光输出。该技术适用于任何其它准分子器件。     

Ultrafine structure spectrum of XeCl excimer laser

The computation of the rotational lines based on the coupling of vibration and rotation of XeCl excimer was introduced to explain the ultrafine structure spectrum of XeCl excimer laser. The calculated results are in good agreement with that of the experiment.     

Optimization of a Dielectric Barrier Discharge for Pulsed UV Emission of XeCl at 308 nm

A pulsed dielectric barrier discharge (DBD) has been investigated in a wide range of experimental conditions with the purpose of optimization for XeCl excimer radiation. For that the following operation parameters had been considered: four different lamps of coaxial geometry with gas gaps in the range of 1.3 ‐ 6.5 mm; gas mixtures of xenon and chlorine containing admixtures of 1%, 2% and 4% Cl₂ at total filling pressures between 5 mbar and 600 mbar; voltage rise times of 20 ‐ 50 ns and voltage amplitudes of up to 12 kV. A maximum radiation pulse energy of 1.8 µ J has been detected at 310 ± 10 nm with an estimated radiation decay by three orders of magnitude within about 5 µ s. It was shown that the minimization of the voltage rise time is essential for enhancing the radiation pulse energy. Furthermore a correlation between the discharge geometry and the optimum pressure for maximum radiation output was observed. The decay characteristics of the excimer emission provides evidence of the harpoon reaction being the main channel of XeCl formation under our operation conditions (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)