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。     

KrF激光脉冲整形研究

 实验研究了脉冲堆积法对KrF激光的整形能力。利用受激布里渊散射(SBS)压缩脉冲获得了脉宽为3~5 ns的短脉冲，用4束激光堆积获得了脉宽为10~15 ns、平顶宽度为5~10 ns的整形脉冲。利用实测SBS脉冲数据，对脉冲堆积法进行了数值模拟，模拟的脉冲宽度为12.7 ns，平顶宽度为7.7 ns，该结果与实验相符。对脉冲堆积法的任意整形能力进行了模拟，讨论了脉冲宽度变化对整形的影响，发现脉宽变化在5%以内时，对整形脉冲的影响较小。对整形脉冲的放大进行了定性研究，结果表明：平顶脉冲通过放大器后，前沿部分放大较多，由于饱和作用，后沿放大较少；如果前端整形脉冲前沿为斜坡状，放大后可以得到近平顶的脉冲。     

能量啁啾电子束自由电子激光放大啁啾脉冲

 提出采用具有能量啁啾电子束的自由电子激光放大器放大啁啾脉冲,分析说明了它的工作机理和滑移现象对其的影响。采用研制的1维非定态程序GOFEL-P,对能量啁啾自由电子激光放大器放大啁啾脉冲的过程进行了数值模拟和分析,计算了不同啁啾参数的脉冲被放大后的腔外压缩情况。结果表明：与单能电子束时相比,能量啁啾自由电子激光可以放大具有更大啁啾参数的啁啾脉冲,使压缩后的脉冲峰值功率增大至568 GW,脉冲宽度缩短至2.29 fs,大幅增强自由电子激光放大啁啾脉冲以及腔外压缩脉冲的效果。     

采用环形再生腔结构的飞秒激光啁啾脉冲放大研究

采用环形再生腔结构的啁啾脉冲放大技术方案, 在重复频率100 Hz,单脉冲能量33.1 mJ的532 nm激光抽运下, 从钛宝石激光中获得了单脉冲能量9.84 mJ的放大输出, 对应的斜效率达33.1%.在重复频率10 Hz的情况下, 同样获得了单脉冲能量为9.64 mJ, 对应斜效率达36.8%的高效率放大结果. 通过色散补偿压缩该啁啾激光脉冲后的单脉冲能量为6.36 mJ, 脉冲宽度为59.7 fs. 测量结果表明典型的能量不稳定度为1.85%. 关键词： 啁啾脉冲放大 再生放大 飞秒激光 环形腔     

增益饱和在啁啾脉冲放大中的影响

研究了增益饱和在啁啾脉冲放大中的影响，发现由于增益饱和在存在，压缩后脉冲的信噪比会下降，而且展宽器附加的色散也会降低输出的信噪比，这种降低对应着一定的光谱畸变。通过对展宽／压缩器作用的分析，提示了啁啾脉冲放大中光谱与光强的内在联系，提出利用非共振放大来修正光谱畸变提高放大压缩后的信噪比。     

可用于超精细加工的高重复率、高光束质量飞秒再生放大脉冲的产生研究

通过飞秒放大增益饱和理论及飞秒脉冲展宽的理论计算与分析，指出在优化放大腔结构参数及改变抽运光能量情况下，可以在省略展宽器基础上实现中等能量的飞秒脉冲再生放大.以此为依据，采用低抽运能量和放大腔中钛宝石晶体离焦技术，成功地进行了无展宽器的高重复率飞秒钛宝石再生放大及压缩技术的实验研究，并获得了高光束质量的飞秒放大光脉冲，放大光脉冲能量大于100μJ，重复频率为1kHz，光谱带宽7.7nm，压缩后脉宽500fs. 关键词： 飞秒光脉冲 再生放大 光束质量 增益饱和     

适用于放大自发辐射平滑光束的脉宽压缩方法

为了增加靶上的功率密度和耦合效率,基于饱和增益开关原理,发展了一种适用于放大自发辐射平滑光束的脉宽压缩方法。利用该方法,在赛格德大学的一台放电泵浦KrF准分子激光器上进行了实验,将该激光器输出的脉宽为14.5 ns的放大自发辐射光束压缩到了7.5 ns,并且保持了光束原有的均匀性。     

高功率超短脉冲激光系统的进展

评述了超高功率亚皮秒脉冲产生的物理基础。峰值功率和照度的增加直接起因于啁啾脉冲放大技术。考查了超短脉冲的产生、展宽、放大和压缩。讨论了发展和设计太瓦－拍瓦激光的方案和一般问题。     

受激布里渊散射脉冲压缩技术研究进展

受激布里渊散射（SBS）作为三阶光学效应广泛应用于激光组束、分布式光纤传感、布里渊激光器等领域。近年来,SBS脉冲压缩亦得到特殊关注。基于布里渊放大过程中的能量转移特性,SBS脉冲压缩技术能够将ns量级脉冲压缩至亚ns量级,峰值功率可提升1～2个数量级。系统介绍了SBS脉冲压缩基本理论,综合论述了SBS压缩器结构、增益介质、泵浦脉冲等因素对脉冲压缩特性的影响,并对SBS脉冲压缩发展趋势进行了展望,为今后SBS特性的研究提供了有益参考,也为高重频、高能量激光的获取提供了可行方案。     

基于预啁啾管理放大的掺镱锁模光纤激光器

报导了一种采用预啁啾管理放大技术实现的百飞秒级掺镱光纤激光器系统。该系统首先利用非线性偏振旋转技术搭建锁模种子激光,实现重复频率为82.3 MHz、压缩后脉宽接近180 fs的近线性啁啾稳定脉冲序列。种子脉冲通过预放大级和预啁啾管理放大级后获得了平均功率为12 W、压缩后脉宽低于100 fs的脉冲。经过预啁啾管理放大级的压缩后脉冲宽度明显优于种子激光的压缩后脉冲宽度。     

氟化氪短脉冲激光的放大和组束研究

为充分利用氟化氪(KrF)准分子激光放大器的长泵浦时间,探索提高激光输出效率的方法,开展紫外超短脉冲在KrF准分子激光器中多脉冲放大和组束的实验研究。采用双脉冲放大方案研究激光脉冲时间间隔对输出能量的影响,确定延时时间,提高脉冲总能量并有效抑制自发辐射(ASE)。实现了单次放大4个紫外超短脉冲,获得了近4倍于单脉冲放大的输出能量。并探索紫外超短激光脉冲的组束技术,成功应用光学角多路的方法将两个亚皮秒的紫外激光脉冲进行精确组束。     

Characterization of ultrashort electron pulses by electron-laser pulse cross correlation

An all-optical method to determine the duration of ultrashort electron pulses is presented. This technique makes use of the laser pulse ponderomotive potential to effectively sample the temporal envelope of the electron pulse by sequentially scattering different sections of the pulse out of the main beam. Using laser pulse parameters that are easily accessible with modern tabletop chirped-pulse amplification laser sources, it is possible to measure the instantaneous duration of electron pulses shorter than 100 fs in the energy range that is most useful for electron diffraction studies, 10-300 keV.     

High-power sub-100-fs UV pulse generation from a spectrally controlled KrF laser

High-power sub-100-fs UV pulses were generated from a KrF excimer laser by spectral control and chirped-pulse amplification. The spectral width was broadened to 1.6 nm, resulting in 72-fs, nearly transform-limited pulses. The average output powers at 1 kHz were 0.6 and 1.2 W for pulse widths of 72 and 110 fs, respectively.     

利用非线性脉冲预整形实现脉冲快速自相似放大

报道了一种通过预先对信号光脉冲非线性整形, 进而在光纤放大器中实现自相似演化的方法. 利用透射光栅对和普通单模光纤组成被动脉冲整形装置, 预先优化脉冲的时域宽度和光谱质量, 使脉冲在光纤放大器中快速演化到自相似子. 研究中首先通过数值模拟对比, 说明了非线性整形对脉冲实现快速自相似放大的关键作用, 提高了放大器输出脉冲质量, 减小了去啁啾脉冲宽度. 实验中, 通过优化非线性整形输出, 在2.2 m 长的掺Yb³⁺光纤中, 在一定抽运功率范围内均实现了脉冲自相似放大, 去啁啾后得到脉冲宽度60 fs 的变换极限脉冲输出. 这种非线性脉冲预整形方法有效减小了 自相似演化所需光纤长度, 同时降低了自相似放大对种子源质量的要求, 首次将全正色散光纤锁模激光器成功用于自相似放大, 促进了当前自相似放大系统的全光纤化. 关键词： 非线性整形 光纤放大器 自相似放大 飞秒激光     

Spatially-hole-burned distributed feedback dye laser produced tunable single picosecond pulses

A new type of distributed feedback dye laser is described in which the Bragg grating is formed by spatial hole-burning. With a simple excimer laser pumped arrangement, single high stability 6 ps pulses were generated. The pulses were nearly transformlimited and were 33 times shorter than the rise time of the pulse which created the Bragg grating.on leave from JATE University, Department of Experimental Physics, Dóm tér 9, H-6720 Szeged, Hungary     

High-repetition-rate 12 fs pulse amplification by a Ti:sapphire regenerative amplifier system

We demonstrate the direct generation of 12 fs pulses from a Ti:sapphire regenerative amplifier system at a 1 kHz repetition rate utilizing properly designed broadband components for chirped-pulse amplification. Optimized designs of a regenerative amplifier with a multilayer gain-narrowing compensator and an adaptive dispersion compensator with a spatial light modulator contribute to the shorter pulse amplification.     

The effect of pulse to pulse variation on ultrashort pulsewidth measurements

An alternate interpretation is presented for the exponential shapes of the second harmonic autocorrelation functions obtained from synchronously pumped mode locked dye laser systems. The shape is reinterpreted as being due to a weighted average of pulses of varying widths and smoothly varying pulse shapes in time. Such pulse width measurements in the past have averaged over a large number of pulses. Several pulse shapes and pulse width distributions are examined all leading to exponential shaped autocorrelation functions. This interpretation implies that the currently determined pulsewidths are shorter, possibly many times shorter than the actual average pulsewidths. A method for selectively descriminating the shortest pulses from the train to increase the time resolution of current laser systems is presented.     

Stacking chirped pulse optical parametric amplification

Stacking chirped pulse optical parametric amplification based on a home-built Yb³⁺-doped mode-locked fiber laser and an all-fiber pulse stacker has been demonstrated. Energic 11 mJ shaped pulses with pulse duration of 2.3 ns and a net total gain of higher than 1.1 × 10⁷ at fluctuation less than 2% rms are achieved by optical parametric amplification pumped by a Q-switched Nd:YAG frequency-doubled laser, which provides a simple and efficient amplification scheme for temporally shaped pulses by stacking chirped pulse.