高功率钛宝石激光放大器理论研究

从麦克斯韦方程出发，建立了宽带高功率激光放大系统的理论模型，同时用数值方法对宽带和窄带高功率激光放大器进行了计算，讨论了增益变窄效应在放大系统中对放大脉冲的影响，从理论上提出并验证了消除由放大介质发射截面不对称对脉冲造成的畸变的方法。论文对正确设计高功率激光驱动器也具有一定指导价值。     

与794nm飞秒激光精确同步的无直流背底的1064nm脉冲光的产生

基于非共线光参量放大(NOPA)，以宽带794nm飞秒激光的倍频光为抽运光，以连续的He-Ne激光为信号光，产生了与宽带794nm飞秒激光精确同步的无直流背底的1064nm的脉冲光.实验结果显示该1064nm的光脉冲可作为光参量啁啾脉冲放大系统的抽运激光链的种子光，从而实现用全光学方法实现OPCPA系统抽运光和信号光的精确同步.还将非共线光参量放大器置于经特殊设计的He-Ne激光腔内，也同样成功得到了无直流背底的1064nm的光脉冲.经一次光参量放大后所得到的1064nm光的光谱和空间啁啾特性与非共线光参量放大器置于He-Ne激光腔外时得到的1064nm的光脉冲相同，而其单脉冲能量约为腔外NOPA的10倍. 关键词： 非线性光参量放大 光参量啁啾脉冲放大 时间同步     

单脉冲飞秒激光时域参数测量技术研究

钛宝石飞秒激光放大系统具有重复频率低、脉冲波形复杂等特点，为准确测量其峰值功率，提出对单次脉冲波形和脉冲宽度测量的需求。介绍了单脉冲飞秒激光时域波形和脉冲宽度的测量原理和测量方法，设计了基于频率分辨光学开关法的单脉冲飞秒激光时域参数测量装置。讨论了单脉冲飞秒激光时域参数测量校准面临的问题及解决方法。     

高对比度紫外电光削波开关

采用电光开关产生短脉冲的技术,建立了一种抑制准分子激光放大链自发辐射放大(ASE)的方法,研制了高对比度紫外电光削波开关,并进行了原理性实验,将其应用于准分子单路主振荡功率放大系统第一级预放大器的ASE控制。实验中电光开关对比度达到了2000多,削波后的预放大器输出激光脉冲信号对比度提高至20 000多,有利于激光信号后续进一步高保真放大,为系统获得窄脉冲输出提供了技术支持。     

高峰值功率大模场全光纤脉冲放大器

报道了一种由纤芯直径分别为15μm和25μm的大模场光纤组成的全光纤脉冲放大器模块.当注入脉冲宽度为10 ns,重复频率为1 Hz.光谱宽度为0.3 nm,脉冲能量为80 nJ的激光脉冲时,经过两级放大输出的激光脉冲峰值功率为30 kW,单脉冲能量为300μJ.此外,实验研究了该放大器模块输出的时间特性.研究发现:由于受激布里渊散射(SBS)效应,限制了单纵模光纤激光在光纤中的高能量放大,采用宽带激光脉冲可以有效地抑制SBS效应,提高光纤放大器的SBS阈值.     

啁啾脉冲放大激光系统中展宽器色散的解析算法

时域色散精密控制是超短激光产生及其应用中的关键技术之一,它通过控制各波长的光程产生相对延迟从而改变脉冲宽度.展宽器是啁啾脉冲放大激光系统中对激光脉冲展宽的装置,基于光线追迹法研究光线在展宽器中的传输路径,可计算飞秒脉冲中各波长的光程,进而计算脉冲展宽量并应用于系统设计.由于展宽器的光程表达式复杂,直接对其求导获得色散表达式较困难,目前只能采用数值导数获得近似解,这在计算过程中会引入误差,不利于激光系统精确设计和优化.本文介绍了一种易实现的求解展宽器色散的解析算法,通过归纳展宽器光程表达式特点,引入四个基元函数,将光程表达式分解和反复代换,可得到高阶色散的精确解析值.本文首先对Martinez型展宽器重新光线追迹,获得与Offner型展宽器一致的相位表达式,其次通过解析算法获得了两种展宽器的精确高阶色散值,最后将解析算法与数值算法的结果进行了比较.该解析算法对于啁啾脉冲放大系统的参数设计具有实用价值.     

钕玻璃宽带激光放大能量提取效率研究

基于钕玻璃宽带脉冲激光放大模型,采用数值模拟的方法,研究了钕玻璃放大器对不同输入光通量、不同脉宽以及不同带宽(或波长分布)脉冲激光放大的能量提取效率。计算结果表明,钕玻璃宽带放大能量提取效率随着输入光通量的增加而提高,并最终趋于某一定值。对于以均匀加宽为主的介质,随着带宽的增加,能量提取效率逐渐下降;对于以非均匀加宽为主的介质,随着带宽的增加,能量提取效率先逐渐升高,达到最大值后开始下降。对于均匀加宽与非均匀加宽线宽比为0.1的混合加宽介质,在饱和通量输入条件下,使用宽带激光能够带来大约80%的效率提升。     

采用光谱展宽技术的钛宝石飞秒激光放大器

报道了飞秒激光啁啾脉冲放大器中的激光脉冲光谱展宽技术，实验中使用了几种光谱展宽元件，结果表明使用激光光谱展宽元件能有效地将飞秒激光脉冲 光谱展宽，抑制了飞秒激光放大器中常见的激光脉冲光谱增益窄化现象，从飞秒放大系统的振荡级输出28fs种子脉冲，放大后得到了重复频率为10Hz、峰值功率为1．6TW、脉冲宽度37．5fs的超短强飞秒激光脉冲 。     

激光放大器的稳定脉冲

本文求得了激光放大器速率方程的小信号解析解,分析了获得稳定脉冲的条件以及泵浦对脉冲放大变形的影响.     

用于飞秒脉冲放大器的马丁内兹展宽器与欧浮纳展宽器性能比较

用解析法针对多通和再生两种放大器，分别研究啁啾脉冲放大技术中马丁内兹展宽器和欧浮纳展宽器的特性和适用范围.我们认为在多通放大器和再生放大器中，马丁内兹展宽器均可以很好地补偿色散；如果使用再生放大器时需要将脉冲宽度展得更宽，可采用紧凑型欧浮纳展宽器. 关键词： 啁啾脉冲放大技术 马丁内兹展宽器 欧浮纳展宽器     

Simulation study of broadband long-pulsed amplification in high-power laser systems

Accurately and efficiently predicting the fundamental-frequency temporal shape of broadband long-pulsed lasers is very important in research on the properties of high-power laser amplifiers. In this study, we first propose that analytic electric polarization in the temporal domain is applied to broadband long-pulsed pulse amplification.We first verify the accuracy of this algorithm in the dozens of picoseconds range and the results are consistent with Miro software. Then we simulate the broadband long-pulsed amplification. The simulation results indicate that the front edge of the output pulse is more enlarged than the end edge owing to saturation and that the gain narrowing induces severe amplitude modulation. Analytic electric polarization in the temporal domain is effective and precise for investigating the broadband pulse amplification in the time scale from dozens of picoseconds to nanoseconds, and the computation time can be decreased by at least 4 orders of magnitude.     

宽带光学参变啁啾脉冲放大系统的色散控制

在设计宽带光学参变啁啾脉冲放大系统时,对色散源进行了理论分析和讨论。对光学参变啁啾脉冲放大系统的色散量以及各个过程中的高阶色散对脉冲时域和频域特性的影响进行了计算。结果表明展宽器引入了非常大的色散,放大器中信号光相位变化产生的色散较大,参量晶体本身引入的色散相对较小可以忽略不计。输出脉冲宽度主要受二阶色散影响,而三阶和四阶色散主要影响脉冲的波形和信噪比,对频域影响很小。     

Generation of high average power, 7.5-fs blue pulses at 5 kHz by adaptive phase control

The spectral width of a 5-kHz Ti:sapphire laser system was broadened by spectral control in a regenerative amplifier consisting of broadband chirped mirrors. The dispersion over the wide spectral range was compensated by a deformable mirror along with a genetic algorithm, resulting in a pulse width of 15 fs. The pulse width is the shortest, to our knowledge, in chirped pulse amplification systems with a regenerative amplifier. The phase distortion of broadband frequency doubling in addition to the Ti:sapphire laser was compensated by using the self-diffraction intensity in sapphire as the feedback signal into the genetic algorithm, resulting in a pulse width of 7.5 fs. The average power of the second harmonic was 1 W with a fundamental input of 7 W.     

The inverse problem of a laser amplifier

Starting from the recurrence relations of a multipass amplifier, an iterative computing method has been presented to solve the inverse problem of a laser amplifier, i.e., to find the initial fluence and pulse shape for a given output pulse and amplifier parameters. Numerical calculations have been performed to illustrate the results.     

Simple generation of tunable near-infrared picosecond dye-laser pulses using spectro-temporal selection

The spectral and temporal processes in broadband pulsed-laser emissions of near-infrared dyes generated from low-Q and short laser cavities have been investigated with a rate equation model extended to a multiwavelength analysis. A very fast spectral evolution is proved, and this leads to the intrinsic presence of a single short pulse on the short-wavelength wing of the broadband IR dye laser spectrum. From the results, the direct generation of picosecond (≈90 ps)infrared dye-laser pulses adjustable in the 700–850 nm spectral range is successfully demonstrated with spectro-temporal selection, in a compact and simple device, using a nitrogen laser (337.1 nm, 8 ns) or a Q-switched ruby laser (694.3 nm, 25 ns) as a pumping source. Received: 6 October 1998 / Revised version: 14 April 1999 / Published online: 11 August 1999     

Multi-millijoule, nonlinear preamplifier for high intensity femtosecond Yb:YAG chirped-pulse amplification lasers at 1030 nm

We report the highest energy broadband laser pulses at a center wavelength of 1030 nm based on optical parametric chirped-pulse amplification (OPCPA). We have demonstrated amplification of 1030 nm femtosecond laser pulses from a broadband Yb oscillator to over 6.5 mJ with a total gain of greater than 10⁷ achieved in a single pass through only 56 mm of gain material at a 10 Hz repetition rate. The amplified spectral bandwidth of 10.8 nm affords recompression to a 230 fs pulse duration following amplification. As an alternative to the regenerative amplifier (RA) this system is one of the more promising candidates for realizing compact, high intensity, direct diode-pumped, high repetition rate femtosecond Yb:YAG chirped-pulse amplification (CPA) in laser systems.     

用逐次逼近迭代法分析含空间滤波器的多程激光放大系统的逆问题

基于Ｆｒａｎｔｚ－Ｎｏｄｖｉｋ（Ｆ－Ｎ）方程和广义惠更斯－菲涅耳衍射积分，提出了解决含空间滤波器的多程激光放大系统的逆问题的迭代算法，并作了数值计算了，所得的数值计算方法和有关结果可用于高功率多程激光放大系统的设计。     

Zakharov-Manakov solution of the SBBS amplifier problem for non-rectangular envelopes

The inverse scattering transform method is applied to the stimulated Brillouin backscattering (SBBS) interaction of nonrectangular laser and signal envelopes in an amplifier experimental setup. Specifically, the Zakharov-Manakov problem is solved for the complete spatial and temporal evolution of laser and signal pulses which are characterised initially (before interaction) by rapidly rising envelopes with exponentially decaying tails.     

含空间滤波器的激光放大系统的逆问题

从Frantz Nodvik方程和广义惠更斯 菲涅耳衍射积分出发，采用快速傅里叶变换和逐次逼近叠代法，求解含空间滤波器的激光放大系统的逆问题，即由所要求的输出激光时间、空间波形和能量密度，并给定放大器和空间滤波器参数情况下，求输入激光时间波形、振幅和相位分布- 关键词：     

Femtosecond pulse parametric amplification at narrowband high power gas laser pumping

In ultrashort pulse amplification a narrowband gas pump pulse laser has been used for the first time. An all-stage optical parametric chirped pulse amplifier (OPCPA) was driven by a single-shot iodine photodissociation laser. For the first time a broadband amplification was achieved in potassium dihydrogen phosphate crystal at 800 nm seeding. Ti:sapphire laser pulses stretched from 12.5 fs to 250 ps were amplified and compressed to 27 fs at a 0.5 TW output power. The results suggest using narrowband high power gas lasers as OPCPA drivers to generate petawatt beams.