基于受激布里渊散射的调Q光纤激光器研究

为了获得窄脉宽和高功率的光纤激光脉冲,对基于受激布里渊散射的脉冲抽运调Q光纤激光器进行了实验研究.设计了布喇格光纤光栅、掺Yb3+双包层光纤和单模光纤作为线性谐振腔.采用锥形光纤连接抽运模块与掺Yb3+双包层光纤实现了光纤激光器的全光纤化结构.通过脉冲抽运方式,利用光纤中的非线性效应——背向受激布里渊散射对激光进行混合调Q,得到了纳秒量级的脉冲输出,其脉宽为400ns,平均功率2.5W,重复频率15kHz.结果表明,通过脉冲抽运方式,利用光纤中的受激布里渊散射能够有效地压缩输出脉冲的线宽,实现高功率输出.     

掺Yb双包层光纤激光器脉冲压缩的实验研究

对连续和脉冲泵浦掺 Yb双包层光纤激光器的时域特性进行了实验研究。利用光纤中的受激布里渊散射 (SBS)压窄脉宽 ,将脉冲泵浦产生的 10 0μs光脉冲压缩到 ns量级 ,其压缩因子为 2 .0 8× 10 4,并对实验结果进行了定性分析     

熔融石英中实现高效率的百毫焦受激布里渊散射

固体布里渊增益介质是目前实现高稳定、高重复频率受激布里渊散射(SBS)的重要光学元件，能够产生高光束质量的相位共轭光。然而，不同于被广泛研究的液体布里渊增益介质，目前针对固体布里渊增益介质如何产生高效率高能量的SBS尚无成熟的研究。近日，笔者团队以块状熔融石英作为布里渊增益介质，在高强度纳秒激光脉冲泵浦下，围绕熔融石英中的SBS能量转换效率和损伤阈值与泵浦光纵模的关系开展了研究，实现了最高单脉冲能量183.1 mJ、反射率为81.0%、斜效率高达85.8%的相位共轭光输出。该研究结果对于实现高功率全固态的SBS相位共轭镜，进而提升脉冲激光器的输出功率水平、获得高稳定高效率的SBS运转具有重要的指导意义。     

超窄线宽布里渊光纤激光器研究进展(特邀)EI北大核心CSCD

基于光纤受激布里渊散射的布里渊光纤激光器以其Hz量级甚至亚Hz量级的超窄线宽特性,自问世以来便吸引了广泛的研究关注。超窄线宽布里渊光纤激光器主要经历三个发展阶段,从最初的基于单模光纤谐振腔的布里渊光纤激光器,到向腔内引入掺铒光纤放大器的布里渊掺铒光纤激光器,再到利用一段普通掺铒光纤同时提供布里渊增益与线性增益的紧凑型布里渊掺铒光纤激光器,激光器的性能不断得到发展,相关理论研究也不断得到丰富。近10年,紧凑型布里渊掺铒光纤激光器的研究取得了一系列的进展,在高精度光纤传感等诸多领域有着十分重要的应用前景。按照三个发展阶段依次梳理和总结了布里渊光纤激光器的研究进展,重点阐述了紧凑型布里渊掺铒光纤激光器的机理、特性和应用,并对其未来发展方向进行展望。     

K9玻璃与熔石英玻璃中纵向受激布里渊散射的脉宽压缩和能量提取效率

以K9玻璃与熔石英玻璃代替传统的液体或气体作为纵向受激布里渊散射(LSBS)样品,波长1.064μm,脉宽12 ns的单纵模电光调QNd∶YAG激光器作抽运光,实验上以脉宽压缩和后向斯托克斯(Stokes)散射光频移为标志,测到后向斯托克斯散射光线宽和散射光脉宽压缩比。研究了纵向受激布里渊散射样品的长度、抽运光能量大小、材料种类对纵向受激布里渊散射脉宽压缩效应和散射光能量提取效率的影响。实验结果表明,熔石英与K9玻璃的受激布里渊散射发生阈值、饱和阈值、散射光能量提取效率、散射光脉冲波形均相近,K9玻璃可以成为一种更廉价的受激布里渊散射介质。针对170 mm的熔石英玻璃样品,找到了纵向受激布里渊散射的发生阈值、饱和阈值,并得到了较高的散射光能量提取效率,从100 mm的熔石英玻璃中获得了87%的散射光能量提取效率,而从170 mm的熔石英中获得了90%左右的散射光能量提取效率。实验数据拟合的规律曲线印证了数值模拟结果。     

用后向SBS压缩电光调Q Cr∶LiSAF激光脉冲宽度的研究

在抽运能量一定的条件下 ,采用强聚焦短焦距透镜提高焦点处的光功率密度 ,将Cr∶LiSAF电光调Q激光器的输出脉冲聚焦于装有CS2 介质的受激布里渊散射 (SBS)池中 ,实现了宽线宽、多横模Cr∶LiSAF激光脉冲的后向SBS ,并观察到对激光脉宽的有效压缩。     

抽运光参数对玻璃中受激布里渊散射光能量提取效率的影响

以K9玻璃与熔石英玻璃代替传统的液体或气体作为纵向受激布里渊散射(LSBS)样品,波长1.064μm,脉宽可调的单纵模电光调Q激光器作抽运光,实验探讨了抽运光脉宽、抽运光能量大小、抽运光脉冲重复频率对纵向受激布里渊散射脉宽压缩效应和散射光能量提取效率的影响。实验结果表明,抽运激光脉冲重复频率高,则散射光能量提取效率高;脉宽小,则散射光能量提取效率高;焦距为500 mm时300 mm长的K9玻璃中得到的散射光能量提取效率比170 mm长的熔石英玻璃高;在抽运光脉冲重复频率为1 Hz时,二者都可以得到90%的散射光能量提取效率。探讨了抽运光为多纵模时,固体介质中受激布里渊散射与光学击穿相伴发生的三种不同情况。实验证明,多纵模情况下固体光学介质中同样可以发生受激布里渊散射;多纵模情况下不一定会对固体光学介质产生光学击穿破坏;光学击穿破坏的发生也不一定会阻止受激布里渊散射的发生,二者可以相伴发生。     

用后向SBS压缩电光调Q Cr:LiSAF激光脉冲宽度的研究

在抽运能量一定的条件下，采用强聚焦短焦距透镜提高焦点处的光功率密度，将Cr:LiSAF电光调Q激光器的输出脉冲聚焦于装有CS2介质的受激布里渊散射(SBS)池中，实现了宽线宽、多横模Cr:LiSAF激光脉冲的后向SBS，并观察到对激光脉宽的有效压缩。     

超短脉冲激光微孔加工(上)——理论研究

自20世纪60年代激光器被发明以来,其脉冲宽度被不断压缩至亚皮秒及飞秒量级,使得激光加工技术进入到了超短脉冲阶段。为了进一步优化超短脉冲激光的微加工,理论研究必不可少。主要论述了超短脉冲激光与不同类型材料之间的相互作用机制。简述了超短脉冲激光微孔加工中的典型物理特性,如等离子体效应、自聚焦和光丝效应及锥形辐射等。分析了超短脉冲激光微孔加工的理论研究现状,并得出了目前理论研究中存在的问题。     

自启动低噪声光纤孤子激光器

自启动低噪声光纤孤子激光器基于有源光纤增益介质并产生亚皮秒至皮秒脉冲的各种自启动被动锁模激光器已被实验证实。这些激光器的运转要求激光器腔内有某种形式的非线性机制，以获得脉冲运行。最普通的非线性机制是非线性放大环路反射镜［’·’｝或偏振旋光系统［３］。...     

Laser pulse compression by stimulated Brillouin scattering in tapered waveguides

The use of stimulated Brillouin scattering (SBS) for laser pulse compression by backward wave amplification in a tapered waveguide offers an attractive alternative to systems based on SRS for use with narrowband laser pulses. Almost one hundred percent conversion efficiencies may be achieved since it is not seriously limited by second Stokes production and with the added advantage that the Stokes pulse is a phase conjugate of the input pulse, under appropriate conditions. Due to the characteristically long damping times of Brillouin-active media, the SBS process is transient. In this regime, the tail of the Stokes pulse may experience a gain and loss modulation with the laser field resulting in a breakup of the Stokes pulse. This effect can be controlled by the geometric taper on the waveguide. A practical consideration of the scaling of a Brillouin compressor to high-power laser systems, notably KrF, is presented. Specific compressor configurations for the extraction of laser pulses in the nanosecond time scale are presented, and a survey of some promising compressor media indicate the practical possibility of accomplishing compression by SBS.     

Application of a phase-conjugate Brillouin mirror to generation ofhigh-quality variable-duration KrF pulses

Phase conjugation by Brillouin scattering in SF₆ gas has been implemented on a two-pass KrF amplifier to provide near-diffraction-limited output pulses having a very low background level of amplified spontaneous emission. The pulse duration is variable between 1 and 10 ns by simply attenuating the input pulse. These pulses have also been used for the generation of much shorter duration pulses by truncated Brillouin scattering at the surface of cyclohexane     

利用SBS相位共轭技术改善固体激光和准分子激光光束质量研究的进展

介绍利用受激布里渊散射 (SBS)相位共轭技术改善固体激光和准分子激光光束质量研究的进展 ,特别介绍近几年来在 SBS介质、压缩脉宽和高能量高功率激光系统研究方面取得的一些新成果 ,并指出其未来发展方向。     

Pulse compression to the subphonon lifetime region by half-cyclegain in transient stimulated Brillouin scattering

A new approach to the transient pulse compression by stimulated Brillouin scattering (SBS) is presented. The theoretical analysis involving the time-dependent SBS gain in explicit form leads to a nonlinear system of partial differential equations, solved numerically by a generalization of the split-step method. It is shown theoretically and confirmed experimentally that the phonon lifetime is not always an appropriate parameter that determines the lower limit to the pulse duration in SBS compressors. A half-cycle gain regime is found for pulses shorter than the phonon lifetime. Hence, under proper conditions, pulses as short as half the acoustic period can be produced     

高功率激光器上的SBS脉冲压缩

:对高功率激光器上SBS脉冲压缩技术的研究工作进行了详细的回顾 ,比较了几种常用的SBS脉冲压缩系统 ,总结了常用于脉冲压缩的几种物质的布里渊参数 ,并分析了SBS脉冲压缩技术的可能的发展趋势。     

环己烷中受激布里渊散射脉宽起伏的实验研究

本文用XeCl准分子激光作为泵浦光源 ,对环己烷中的受激布里渊散射脉宽起伏进行了实验研究 .在脉宽压缩 1 .43倍的同时 ,获得了受激布里渊散射脉宽的起伏为 4.86% ,这一结果优于泵浦光脉宽的起伏     

Fourier-transform-limited laser pulses tunable in wavelength and induration (400-2000 ps)

A combined system of an injection-seeded pulsed dye amplifier and a pulse compressor based on stimulated Brillouin scattering (SBS) is investigated. It allows for the generation of powerful pulses both tunable in wavelength and in duration. Online tuning of the pulse duration is possible due to the dependence of SBS compression on input energy. A range of 400-2000 ps at up to 100 mJ output energy is demonstrated. The output pulses are temporally and spectrally resolved to investigate the properties of this system. Coherent nearly Fourier-transform-limited pulses of variable pulse duration in the extreme ultraviolet (UV) are produced employing harmonic conversion. As an application of such pulses a single rotational line of H₂ at 98-nm wavelength is excited, demonstrating that the system may be used for laser-spectroscopic studies to simultaneously gain spectral as well as dynamical information     

窄泵浦脉冲对布里渊光时域反射仪测量精度的影响

在窄泵浦脉冲下,由于布里渊散射光的线宽与泵浦脉宽有关,布里渊光时域反射仪(BOTDR)中泵浦脉冲的宽度对BOTDRs的测量精度有影响.本文以数值方法求解了声-光振幅耦合方程,发现当泵浦脉冲的宽度远大于声子寿命时,布里渊散射光的线宽为自然线宽.而当泵浦脉冲的宽度趋于声子寿命时,布里渊散射光的线宽明显增加,从而降低了BOTDR的测量精度.     

Efficient temporal compression of coherent nanosecond pulses in acompact SBS generator-amplifier setup

A pulse compressor based on stimulated Brillouin scattering (SBS) in liquids is experimentally and theoretically investigated. It allows for the compression of Fourier-transform limited nanosecond pulses of several hundreds of millijoules of energy with both high conversion efficiency and a high temporal compression factor. The two-cell generator-amplifier arrangement is of a compact design not requiring external attenuation of the generator cell input energy. Pulses from an injection-seeded, frequency-doubled Nd:YAG laser of 300-mJ energy were compressed by a factor variable between 6 and 21 at up to 75% reflectivity. Deviation from unity SBS reflectivity is predominantly determined by optical component losses. The generation of 270-ps pulses with high beam quality was achieved in liquid methanol. These powerful pulses of variable duration are difficult to produce with common laser systems and are highly suited for the generation of high-harmonics in gases     

Multiple-short-pulse stimulated Brillouin scattering for trains of200 ps pulses at 1.06 μm

High-reflectivity, good-fidelity multiple-short-pulse stimulated Brillouin scattering phase conjugation is demonstrated for pulse trains containing pulses of 200-ps duration with interpulse separations of 7.5 ns. The reflectivity is seen to build up from pulse to pulse to a final value of 52%. The Brillouin medium is high-pressure SF₆ gas having a Brillouin lifetime of 35 ns. Severe competition with optical breakdown is discussed