宽频带聚焦泵浦准稳态受激电子喇曼散射的增益因子和能量转换效率

本文采用Raman-Maxwell-Bloch方程,计算了宽频带聚焦泵浦准稳态受激电子喇曼散射的增益因子和能量转换效率.在计算中考虑了泵浦抽空、喇曼介质对泵浦光的吸收和喇曼介质的泡和效应.计算结果与XeCl激光在钡蒸汽中的受激喇曼散射实验基本上符合.     

XeCl激光泵浦高压氢的衍射极限SRS斯托克斯光输出

利用XeCl准分子激光在高压氢中产生受激喇曼散射获得峰值功率为0.2MW、衍射极限发射角的一阶(353nm)斯托克斯输出,井研究了泵浦激光发散角对受激喇曼散射转换效率的影响.     

高效率599 nm Ba(NO3)2外腔喇曼激光器

橘黄色波段固体激光器在基于荧光探测的生物医学诊断和显示等众多方面有着广泛的实际应用. 报道了利用532 nm的Nd∶YAG倍频激光抽运外置喇曼腔内的硝酸钡晶体,获得高效率的599 nm橘黄色喇曼激光的实验结果.对外置喇曼腔实验装置和运转参量进行了优化,喇曼振荡腔由对二阶斯托克斯光有最优化反射率的腔镜构成,对实验中所得到的二阶斯托克斯喇曼激光脉宽压缩及出现双尖峰的现象进行了分析.当抽运光功率达到4.1 W时,获得二阶斯托克斯喇曼激光功率为710 mW,输出光中心波长为599.38 nm,半峰全宽（FWHM）为1.1 nm,激光器最大光光转换效率为17.5%,斜率效率为24.8%.     

皮秒激光瞬态受激喇曼散射的实验研究

本文采用对撞脉冲锁模Nd:YAG激光器输出10ps脉冲串,经KTP非线性晶体腔外倍频,泵浦喇曼介质为二甲亚砜(DMSO)液体.实验研究了不同透镜焦长、焦点位置及不同喇曼介质氏度对瞬态受激喇曼散射的影响,获得了能量转换效率分别为45.6%和10.5%的前、后向一阶斯托克斯-喇曼散射光,并对实验结果进行了讨论.     

KGW晶体外腔式高功率579nm喇曼黄光激光器

报道了579nm高功率KGd(WO4)2喇曼晶体外腔式喇曼黄光激光器的输出特性.基于808nm脉冲激光二极管侧面泵浦Nd∶YAG陶瓷、腔内BBO电光晶体同步延迟调Q和Ⅰ类临界相位匹配的LBO晶体腔外倍频方案,并通过外腔式KGW晶体Ng轴二阶斯托克斯喇曼频移,获得了579.54nm黄光激光输出.当脉冲信号重复频率为1kHz、532nm泵浦光最高平均功率为5.02W、脉冲宽度为10.1ns时,获得了最高平均功率2.58 W、脉冲宽度7.4ns、峰值功率348.6kW的579.54nm二阶斯托克斯喇曼黄光激光输出;532nm至579.54nm的光-光转化效率为51.4%、斜率效率为54.8%,光束质量因子Mx2-579.54=5.829、My2-579.54=6.336,输出功率不稳定性小于±2.35%.实验表明:外腔式喇曼结构能够高效地获得喇曼黄光,具有很高的光-光转化效率及良好的功率稳定性,并通过脉冲LD结合同步延迟电光调Q可获得高重复频率、高平均功率、窄脉冲宽度和高峰值功率的黄光激光输出.     

极性倍频晶体中的相干喇曼混频

本文建立了极性倍频晶体中极化声子相干喇曼混频的耦合波方程,其中考虑了超喇曼极化率β_R.该方程在小信号、声子近似以及喇曼驱动的参量近似下求解.结果表明:在高强度泵浦光受激喇曼散射的相干驱动下,极性倍频晶体可以在泵浦光倍频附近产生极化声子的相干喇曼光束.这种光束可以通过不同的相干喇曼混频过程,由倍频光直接转换,或由基波光直接转换,还可以由倍频光与基波光共同转换而成.这三种转换过程具有各自不同的相位失配因子.在一定条件下,后两种过程可以同时进行.在LiIO_3晶体中证实了上述的结论.实验中泵浦光强度约3.0×10~9W/cm~2.     

高效率,窄脉冲1 198.5 nm Ba(NO3)2喇曼激光器

利用1064nm的Nd∶YAG激光抽运振荡腔内的硝酸钡晶体,获得高效率、窄脉冲的喇曼激光输出.硝酸钡晶体由水溶液降温法生长,长度为48 mm.喇曼振荡腔由对抽运光、一阶、二阶斯托克斯光有不同反射率的双色平面镜构成.当抽运光功率达到4.5 W时,获得最高的一阶斯托克斯喇曼激光功率为1.48 W,相应的转换效率为32.9%,并测得斜率效率为40%.由于受激喇曼散射的作用,喇曼脉冲光由抽运脉冲光的19.8 ns压缩为2.4 ns,获得的喇曼激光脉冲波形具有的“上升沿陡峭、下降沿缓慢”的特性,对其形成过程作了定性分析.测得喇曼激光的波长为1 198.5 nm,半峰全宽（FWHM）为1.2 nm.     

钡蒸气的受激喇曼散射及碰撞诱导受激辐射

在宽带XeCl激光泵浦的钡蒸气中,观察到波长分别为472.6nm,582.6nm和648.3nm的碰撞诱导受激辐射以及波长为475nm的受激喇曼散射.碰撞锈导受激辐射脉宽为3ns左右的自终止型短脉冲,其强度随缓冲气体压力的升高而上升.喇曼光脉冲前沿与泵浦光脉冲前沿之间有长20ns的时间延迟,喇曼转换效率随缓冲气体压力的升高而下降     

固体中光声喇曼效应的原理特性分析

从相干喇曼放大过程出发,运用准平衡模型以及热弹理论,对固体样品中光声喇曼效应进行理论分析,导出了脉冲激光泵浦下的光声喇曼信号表达式,并做了数值估算.总结分析了固体介质中光声喇曼效应的一些特性.     

甲烷喇曼激光器研究

以甲烷作为喇曼散射物质,以YAG激光器输出的1.06μ激光作为泵浦光,研究甲烷喇曼激光器的某些特性。1.54μ激光输出能量约10毫焦,脉宽为6至10毫微秒。最佳总转换效率(电源输入能量到1.54μ激光输出能量),约为千分之一。     

注入控制铜蒸气激光方向性时间过程测量

实验研究了注入控制对铜蒸气激光非稳腔输出光束质量的影响，从输出光发散角时间分辨过程的测量结果说明注入加速被注入腔内激光发散角的减小过程。由于被注入腔内放大自发辐射的存在，为得到较好的注入控制效果，注入光的脉宽和进入被注入腔的延时必须恰当。     

Evaluation of a Continuous Flow Furnance Atomizer for Laser Excited Atomic Fluorescence Spectrometry

A system for continuous sample introduction into a ceramic atomization furnace for laser excited atomic fluorescence spectrometry (LEAFS) was developed. The system was evaluated using two different excitation sources, a nitrogen laser-pumped dye laser and a copper vapor laser-pumped dye laser. Pure aqueous Pb solutions were used for system optimization and analytical calibration curves. These curves were linear over at least three     

自滤波铜蒸气激光器的研究

为获得接近衍射极限发散角的铜激光，设计了共焦及平凹二种自滤波非稳定腔并研究了它们的输出特性，分别获得了发散角为２．５倍及１．４倍衍射极限的铜激光。     

光源稳定性对简并四波混频信噪比影响的实验研究

在碘蒸气中研究了染料激光稳定性对简并四波混频(DFWM)信噪比的影响。实验中采用多模Nd∶YAG激光器倍频的输出泵浦染料激光器(染料PM580溶于酒精)。在具有前向补偿分光系统和图像探测系统的帮助下,在常温常压条件下测得泵浦光在波长为554.013 nm时达到饱和光强为290 μJ。同时发现染料激光器的光稳定性(输出波长范围,光束质量和能量转换效率等)随使用时间,泵浦激光脉冲次数和能量的增加而逐渐减弱。另外通过对比发现在染料激光器输出不稳定时,光源单色性和指向性等指标的变化导致在同一泵浦强度不同时刻获得的DFWM信号强度相差很大,且DFWM信号信噪比低。染料激光器光源稳定性对DFWM信号影响的研究结果对物质的痕迹量探测以及无荧光物质光谱定标等方面的应用具有重要意义。     

均匀化位相的常规非稳腔的分析与实验

 对常规非稳腔的输出镜面进行改造,在原来不透光的中央区域引入增透膜,使之能部分透过,使输出耦合能的比例得到提高;同时加敷适当的位相膜,使中央区与环带区波面位相拉平些。着重报导了均匀化相位常规非稳腔的系列实验和分析,从而使常规非稳腔的环带输出引起的中央不透明区与外环带输出波面的位相突变得到改善,克服了远场能量分布出现较严重离散的问题,使远场中央亮斑能量更集中。     

均匀化位相的常规非稳腔的分析与实验

对常规非稳腔的输出镜面进行改造,在原来不透光的中央区域引入增透膜,使之能部分透过,使输出耦合能的比例得到提高;同时加敷适当的位相膜,使中央区与环带区波面位相拉平些.着重报导了均匀化相位常规非稳腔的系列实验和分析,从而使常规非稳腔的环带输出引起的中央不透明区与外环带输出波面的位相突变得到改善,克服了远场能量分布出现较严重离散的问题,使远场中央亮斑能量更集中.     

Nonlinear frequency conversion of copper vapor laser radiation using convergent and parallel laser beams

Results of experiments are presented on the comparison of the efficiency of radiation generation at the sum frequency (λ=0.271 μm) of copper vapor laser (CVL) in a nonlinear DKDP crystal using either convergent or parallel laser beam. An intensity of UV radiation of 0.34 W and a conversion efficiency of 6% obtained under conditions of strong focusing occur to be substantially lower as compared to those obtained using a parallel laser beam of the same power (0.73 W and 12%, respectively). Experimental data on the structure of a CVL beam generated with an unstable resonator are presented, and physical reasons for the limitation of the efficiency of nonlinear frequency conversion are analyzed.     

Role of optical resonator on the pointing stability of copper vapor laser beam

This paper presents a first comprehensive study on the pointing stability of copper vapor laser with an emphasis on bringing out the role of optical resonator. Long term (∼10 min), single pulse, far-field beam pointing stability of a 5.5 kHz repetition rate copper vapor laser (λ = 510 nm) with plane-plane, unstable and filtering resonators, is studied. It is established that the resonator optics largely decides the CVL pointing stability. Minimum beam pointing angle of 8 μrad from generalized diffraction filtered resonator (GDFR) is obtained in contrast to a maximum value of 120 μrad from the plane-plane resonator. The unstable resonators data is in between. The relative trends in CVL pointing stability are discussed in terms of wave-front distortions due to resonator mode build up from optical noise, thermal and mirror misalignment effects. The degree of optical resonator immunity to phase distortions dictates the net pointing stability achieved.     

Performance of a 80 W copper vapor laser with “alignment free” unstable CAT-EYE resonator and other configurations using intra-cavity apertures

Performance of a kinetically enhanced copper vapor laser (KE-CVL) with various stable/unstable “alignment free” CAT-EYE resonator configurations are presented here in this paper. The laser used in the experiment was a 45 mm bore (∼2 l discharge volume) kinetically enhanced copper vapor laser developed in our laboratory and capable of generating maximum power of ∼80 W (at ∼9.8 kHz). The efficiency of the laser was ∼1.4% and beam divergence of ∼3.5 mrad in a plane-plane standard multimode cavity. For the first time performance of unstable CAT-EYE resonator is demonstrated with a CVL/KE-CVL. On using unstable CAT-EYE resonator the divergence of the laser beam reduced to ∼0.22 mrad (∼20-fold reduction as compared to conventional plane-plane cavity), ∼40 W output power and with excellent misalignment tolerance. The laser output power was found to be within ∼5% drift/decline with misalignment angle of about 4 mrad between the mirrors. This is a significant improvement in comparison to standard conventional unstable resonator (M ∼ 50) CVL where ∼0.5 mrad divergence is achieved with power drift/decline of about 45% at ∼4 mrad misalignment angle.Off-axis unstable CAT-EYE unstable resonator was also demonstrated for the first time with further reduction in beam divergence to ∼0.13 mrad and with output power of ∼28 W. The misalignment tolerance was found to be highest in case of off-axis unstable CAT-EYE resonator with decline/drift in laser power of only ∼10% for misalignment angle as high as ∼8 mrad. Performance with intra-cavity apertures in plane-plane type CAT-EYE resonator for transverse mode control is also presented for the first time in CVLs. It is observed that the laser beam divergence reduces significantly to 1.25 mrad (a factor of 2) on using an aperture of ∼3.5 mm at the CAT-EYE reflector as compared to its normal (R = F = d) configuration without aperture. In case of stable CAT-EYE resonator the average beam divergence reduces from 8 mrad to 4 mrad (factor of 2) on using intra-cavity aperture of about 3 mm. It was also observed that high misalignment tolerance was retained on using intra-cavity apertures in almost all the CAT-EYE resonators. Use of intra-cavity mesh was also demonstrated for the first time with stable CAT-EYE resonator for improving the beam focus-ability. Average beam divergence was reduced by a factor of 2.5 (from 8 mrad to 3 mrad) on using intra-cavity mesh. These new configurations in CAT-EYE resonators in KE-CVLs are found to be effective in improving and controlling the laser beam divergence significantly with additional characteristic of high misalignment tolerance.     

Research of laser evaporation of fast-moving target

Evaporation of a stainless steel target moving with high speed (～50 m/s) under action of laser radiation was investigated theoretically and experimentally. In our experiments we used an electroionization CO₂—laser, which generated pulses with duration up to 1 ms and energy up to 100 J. We carried out the microscopic research of laser beam trace on the target surface and investigated the dynamics of the laser plume luminescence. For theoretical research we used 3D numerical model, which took into account: heating, melting and evaporation of target by laser beam, and, thermal effect of oxidation reaction. The results of calculations can explain the experimental data quite good. In particular, it is possible to explain occurrence of interrupted trace on the target at 12–24 kW laser power, that corresponds to intensity in the focal spot of ～10⁷ W/cm². This power is a threshold of unstable mode of laser evaporation. The unstable mode is caused by lack of oxygen, which was pushed away with metal vapor. The lack of oxygen leads to shutting down the oxidation reaction on target surface. The reaction resumes when the vapors fly away and oxygen riches the surface. As the result pulsed mode of evaporation takes place. This phenomenon was observed as pulse mode of laser plume luminescence and was obtained by calculations.