利用混合介质提高双池SBS系统性能的研究

双池SBS系统由振荡池和放大池两部分组成．振荡池中产生的Stokes种子光进入放大池，与抽运光作用，产生强的放大，Stokes脉冲宽度变窄，能量转换效率提高．以往人们在振荡池和放大池中使用同一种介质，其目的是为了确保Stokes种子和抽运光的频差恰为布里渊频移．但是，当振荡池和放大池中使用同一种介质时，有时受到介质的吸收系数、增益系数、声子寿命和光学击穿阈值等的限制．     

脉冲光布里渊散射信号的拉曼放大研究

实验研究了前向拉曼泵浦方式下脉冲信号光产生的自发布里渊散射信号和受激布里渊散射(SBS)信号的拉曼放大规律。拉曼泵浦放大自发布里渊散射信号时,随泵浦功率增大会出现SBS现象,对散射信号的放大由拉曼放大和布里渊放大两部分引起,因此增益较大,当拉曼泵浦功率为1 000 mW时Stokes光增益可达54 dB。拉曼泵浦放大SBS信号时,放大过程中只存在拉曼放大。且当泵浦功率增大至600 mW时,会引起多级布里渊散射,致使一级Stokes和泵浦能量会转移到下一级布里渊散射,一级Stokes光增益饱和并下降。     

布里渊放大修正陡前沿Stokes脉冲波形

研究了受激布里渊散射(SBS)放大池中．通过改变抽运光与Stokes种子光脉冲的延时．改变它们在池中的相遇位置．实现抽运光对陡前沿种子光脉冲不同部位的选择性放大．从而修正Stokes脉冲波形。理论和实验研究了Stokes光脉宽、脉冲波形前后沿时长比以及能量提取效率等参数随相遇时间的变化规律．在相遇时间2．5ns时，理论得到前后沿时长比为1，能量提取效率80%以上的Stokes放大光脉冲波形．理论和实验符合较好。     

相遇时间对双布里渊放大池放大控制脉冲波形的影响

在传统独立双池结构的受激布里渊散射(SBS)相位共轭镜(PCM)系统中,对布里渊放大池进行改进。引入修整放大池,采用主放大池与修整放大池相结合的双布里渊放大池结构控制脉冲波形,主放大池对脉冲波形进行粗调,修整放大池对脉冲波形,特别是脉冲前沿进行微调。理论和实验研究了相遇时间对双布里渊放大池放大控制脉冲波形的影响,得到了不同相遇时间下,脉冲波形随双池间距的变化规律。研究表明,相遇时间是决定放大光脉冲波形整体形状的重要参数,相遇时间越长,脉冲可控范围越大,但是系统的效率越低。     

飞秒级超短脉冲光参量转换效率及脉冲特征计算

建立了超短脉冲光参量产生过程的理论模型,数值求解耦合波方程组,研究了在飞秒 级超短脉冲的光参量产生过程中,泵浦光的强度和脉宽对转换效率、输出脉冲的宽度和不对称度的影响。结果表明:泵浦光越强,光参量产生的转换效率越高,同时脉宽的压窄效应越明显;泵浦光的脉宽越窄, GVM参数和IGVD参数就越大,导致转换效率下降,同时引起输出脉冲的脉宽变大和波形的对称性变差。     

数字激光告警系统探测接收前端设计

探测接收前端是激光告警系统的关键部件,针对数字激光告警系统设计激光脉冲探测接收前端.采用宽带、高增益、低噪声的跨导放大方式实现了对最小来袭激光脉冲产生的10 nA,10 ms的微弱窄脉冲电流的放大,采用放大器饱和方式实现信号的整形,把来袭激光脉冲转换、放大成数字系统能处理的数字脉冲,脉冲宽度代表作用能量大小.前端最小可检测来袭激光信号能量达1μW,动态范围达100 dB.该宽带低噪声跨导放大电路很好地处理了电容对窄脉冲的影响,具有带宽宽(500 MHz),成本低的特点,为放大微弱的ns级及以下的窄脉冲电流信号提供一个很好的宽带方案.该设计结构简单、成本低廉、易于维护,不仅可用于激光来袭探测,还可用于激光安防系统等.     

基于掺铒(Er3+)光纤飞秒光孤子脉冲的实验放大研究

通过自行设计的同向泵浦和逆向泵浦两种结构,从脉冲宽度、单脉冲峰值能量、峰值功率、增益以及光谱形状方面实验分析了不同泵浦功率情况下飞秒光孤子脉冲的放大情况,得到了逆向泵浦的效率较高的结论.     

飞秒光参量放大技术原理及应用

飞秒光参量放大技术是一种获得宽带飞秒脉冲的有效手段.首先介绍了飞秒光参量放大技术的基本原理,并通过数值模拟显示了群速度失配及位相失配对信号转换过程的影响.数值计算结果表明:群速度失配及位相失配会导致转换效率下降,群速度失配还会导致脉冲发生畸变.其次,综述了该技术在超短脉冲特别是周期量级脉冲产生方面的研究进展,并介绍了Baltuska等设计的可以产生3.9 fs脉冲的非共线光参量放大装置.其中,详细讨论了超连续白光注入源、泵浦光角色散以及晶体选择三方面内容.最后介绍了该技术在高能飞秒脉冲产生方面取得的最新研究进展.     

大口径锥度光纤SBS种子注入的熔石英棒布里渊放大器特性

使用重复频率为400 Hz的Nd∶YAG单纵模主振荡器功率放大(MOPA)激光器作为光源,大口径锥度光纤作为受激布里渊散射(SBS)种子池产生SBS种子光,固体熔石英棒作为SBS放大池,对反向注入的SBS种子光在熔石英棒中呈现不同增益,也即不同抽运功率条件下的布里渊放大行为从功率、时间和空间三个大的方面进行了详细的实验研究,包括放大的SBS输出功率、注入SBS种子光放大倍率、总的SBS反射率、熔石英棒布里渊放大器提取效率以及脉冲宽度和光束质量随SBS种子注入功率的变化情况等。获得了最高输出15.5 W的放大SBS输出、70倍的SBS种子光放大倍率、大于50%的总反射率以及52%的能量提取效率;观察到脉冲展宽以及布里渊放大器中的增益导引两种现象。实验结果表明,在小信号SBS种子光和大信号SBS种子光注入情况下,熔石英棒布里渊放大器具有不同的放大特性。另外,在实验过程中还发现,SBS种子光和抽运光的空间重合程度以及熔石英棒中抽运功率密度的大小是影响SBS放大输出功率的两个重要方面。     

泵浦光发散度对布里渊池重复运转特性的影响

由于受激布里渊散射(SBS)介质大多为液体和气体,当提高重复运转频率或延长泵浦脉冲的持续时间时,其中的热积累和热驰豫将严重影响甚至破坏SBS的形成及其共轭品质.为改善SBS在高重复频率下的工作性能,实验考察了具有SBS相位共轭镜的MOPA(Master-oscillator-power-amplifier)系统中泵浦光发散度对布里渊池重复运转特性的影响.结果表明:降低泵浦光发散度有利于提高布里渊池的重复运转频率及改善SBS的时空特性,但会增加SBS阈值,减小布里渊池工作的泵浦能量范围,同时,保真度略有下降.     

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     

高负载脉宽可调双池受激布里渊散射系统的实验研究

为了提高双池受激布里渊散射(SBS)系统的能量转换效率和负载能力,在布里渊放大池和产生池中选用布里渊频移接近的不同介质,利用Nd：YAG调Q激光对其特性进行了实验研究。与同种介质的双池系统相比,不仅能保持足够的能量转换效率,而且能够有效地提高其负载能力和稳定性。分析和讨论了双池间距对受激布里渊散射性能的影响。     

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.     

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     

主振-功放系统SBS位相共轭技术研究

利用单池与双池位相共轭池,对SBS位相共轭特性进行了研究,实现MOPA激光系统SBS位相共轭高反射率、高保真度、大能量高光束质量激光输出,为高功率激光器的发展提供了有效技术途径。     

High-energy SBS pulse compression

An efficient two-cell stimulated Brillouin scattering (SBS) pulse-compressor design that can be scaled to large laser-pulse energies is described and a numerical model has been developed that accurately predicts the performance of this pulse-compressor system over a wide range of operating parameters. The compression of a 2.5 J input pulse from a width of 15.8 to 1.7 ns is experimentally demonstrated with 80 percent energy efficiency. A design of an SBS pulse compressor to compress a 25 J pulse to a pulse width less than 1 ns with 80 percent energy efficiency is presented     

Coherent lightwave amplification and stimulated Brillouinscattering in an erbium-doped fiber amplifier

The stimulated Brillouin scattering (SBS) of coherent light pulses launched into an erbium-doped fiber (EDF) is reported. In a 50 m EDF, the SBS peak power reaches about 40 dBm for input powers higher than the threshold power of about 6 dBm. SBS and its amplification in an erbium-doped fiber amplifier (EDFA) result in the deformation of a forward-amplified pulse due to the Brillouin power conversion and deterioration of the EDFA population inversion. It is also shown that very short EDF is effective in suppressing the SBS     

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。     

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。     

Transient transverse stimulated Brillouin scattering with abroad-band pump

The threshold for stimulated Brillouin scattering (SBS), which can damage optical components and be an energy loss mechanism in high-power pulsed laser systems, can be increased by using a broadband laser or by segmenting the aperture in order to limit the interaction length. A theoretical model of transient broadband SBS is developed. The authors start by considering the case of transient SBS with a monochromatic pump and find the effective interaction length for a pump pulse of a given duration. Using this interaction length, they derive expressions for the threshold intensity and for the window size required to avoid SBS with a pulse of given power and duration. They compute the steady-state gain and threshold intensity as a function of bandwidth for a multimode laser with large mode spacing