水中受激拉曼散射的能量增强及受激布里渊散射的光学抑制

为提高液体介质中受激拉曼散射的输出能量,提出了通过温度调控来抑制受激布里渊散射的方法,设计了532 nm多纵模宽带脉冲激光泵浦的受激拉曼散射发生系统,测量了不同温度下水中前向受激拉曼散射及后向受激布里渊散射的输出能量,分析了水温、泵浦激光线宽及热散焦效应对受激拉曼散射输出能量影响的物理机制.实验结果表明:通过降低水温可实现对受激布里渊散射过程的有效抑制,同时减小热散焦效应带来的光束畸变,从而有效提高受激拉曼散射的输出能量.研究结果对液体介质中的受激拉曼散射多波长转换具有重要意义.     

分布式拉曼光纤放大器动态增益控制研究

介绍了动态增益控制的必要性，对动态拉曼传输方程进行了简化，并将其以矩阵形式表示，从而减少了方程的数量，提高了计算速度。由拉曼传输耦合方程推出一种适用于分布式拉曼放大器实时控制的自动控制算法。考虑工程需要，该算法忽略了噪声功率、泵浦间的受激拉曼效应，以及信号和泵浦间受激拉曼效应对泵浦功率的损耗。结果表明该算法能够达到快速抑制输入信号功率突变引起的输出功率／增益波动的目的。     

双包层光纤激光器的受激拉曼散射与热应力

 建立了高功率掺镱双包层光纤激光器的速率方程模型与热应力模型，对影响受激拉曼散射效应和热应力效应的关键参数（如纤芯半径、光纤长度、泵浦波长、泵浦方式）进行了数值模拟。结果表明:对于较小的纤芯半径，光纤内的斯托克斯光功率较大且增长迅速，因此增加纤芯半径能有效减弱受激拉曼散射效应；减小光纤长度能提高受激拉曼散射的阈值，而纤芯的热应力也增大，因此在不出现热应力引起光纤断裂的情况下，可以减小光纤长度以提高输出功率；采用976 nm波段泵浦源能提高输出功率，降低热应力的影响；两端均匀泵浦方式可以有效降低纤芯热应力，同时维持高功率输出。     

双折射光纤中斯托克斯波的增益谱

根据激光脉冲在双折射光纤中传输时的混合模方程,考虑拉曼效应后,得出在受激拉曼散射和参量放大共同作用下的增益。数值模拟了当输入泵浦波沿两双折射轴450附近区域传输时,在不同色散区斯托克斯增益谱随输入功率及群速度失配等相关参数的变化关系;结果表明斯托克斯增益谱在不同色散区表现出明显不同的特性,当满足一定条件下,可利用混合模双折射光纤中传输的泵浦波分解出的脉冲序列来分离和提取T频脉冲。     

双折射光纤中斯托克斯波的增益谱

根据激光脉冲在双折射光纤中传输时的混合模方程,考虑拉曼效应后,得出在受激拉曼散射和参量放大共同作用下的增益。数值模拟了当输入泵浦波沿两双折射轴450附近区域传输时,在不同色散区斯托克斯增益谱随输入功率及群速度失配等相关参数的变化关系;结果表明斯托克斯增益谱在不同色散区表现出明显不同的特性,当满足一定条件下,可利用混合模双折射光纤中传输的泵浦波分解出的脉冲序列来分离和提取T频脉冲。     

D2受激拉曼散射产生的紫外激光用于O3差分吸收激光雷达的研究

脉冲Nd∶YAG四倍频激光(266nm)泵浦D2的受激拉曼散射第二级斯托克斯光(316.39nm)用作O3差分吸收激光雷达的λoff。为研究D2的受激拉曼散射效应和定量解释其物理机制作了一系列的实验。通过调节泵浦能量和气体压强,得到了各级散射光的能量转换效率,找到了第二级斯托克斯光的优化条件。     

序列脉冲倍频YAG激光器泵浦的氧气受激拉曼散射研究

对序列脉冲倍频ＹＡＧ激光器泵浦的氧气受激拉曼散射进行了研究。对氧气的受激拉曼散射池的热传导过程进行了数值模拟计算，实验研究了序列脉冲倍频ＹＡＧ激光器泵浦情况下氧气受激拉曼散射的热效应问题。     

光纤受激布里渊增益谱线型特性分析

光纤受激布里渊效应是一种非常重要的光纤非线性效应,受激布里渊增益谱的线型特性,对于光谱分析、微波光子学、光纤传感等领域的应用,至关重要。针对增益谱线型特性研究,现有方法难以获取高信噪比的增益谱数据,介绍了一种采用两个窄线宽激光器的增益谱测量方法,其中一个激光器作为探针信号,另一个可调谐激光器作为泵浦信号在宽波段范围内进行推扫。得益于激光器的高信噪比单谱线特性,并利用偏振跟随特性,实现了高信噪比的受激布里渊增益谱测量。测量并分析了不同泵浦功率,对于谱型和线宽等受激布里渊增益特性的影响,特别是,直接实验测量了增益谱型从洛伦兹线型到高斯线型的演化,揭示了泵浦功率等影响受激布里渊增益水平的因素,对于增益谱线型的影响。实验发现,当泵浦功率超过15 dBm时,增益谱出现饱和效应,导致测量增益谱线宽开始随泵浦功率提高而展宽,难以直接测量得到高泵浦功率时的高斯线型的增益谱。提出通过归一化等校正处理,以获取受激布里渊增益谱与待测信号光谱的有效卷积信息,从而得到了近似为高斯线型的增益谱型;针对中间增益区域增益谱型较为复杂,缺少合适增益谱线型演化数学模型的难题,给出了一种基于k次洛伦兹函数拟合的谱型模型,描述从洛伦兹线型到高斯线型的完整演进过程。实验表明拟合效果良好,是一种行之有效的受激布里渊增益谱线型数学模型,可完整描述增益谱在不同增益时的线型。最后,探索了受激布里渊效应在光谱分析方面的应用,通过合理选择泵浦功率等手段,增益谱型为高斯线型时的光谱分光效果最佳,获取了0.2 pm分辨率的6314CA稳定光源的光谱,显示了光纤受激布里渊效应在超高分辨率光谱分析领域的巨大技术优势,而这对于新一代光网络的验证评估至关重要。     

KrF激光泵浦H2受激拉曼放大

利用KrF激光泵浦高压H_2,在同轴前向的受激拉曼散射(SRS)作用下,产生受激拉曼放大,1阶Stokes光对泵浦光的转换效率为17.2％,并对影响放大过程和转换效率的若干因素作了分析。     

单模石英光纤受激拉曼散射温度特性研究

研究了在不同温度下单模石英光纤的受激拉曼散射光谱,从实验和理论上分析了温度对拉曼散射光谱特性的影响,在脉冲调Q倍频YAG激光的泵浦作用下,获得了石英光纤一级斯托克斯光的拉曼频移、带宽及光强随温度的变化规律。实验表明随着温度的升高,拉曼频移逐渐增大,在一定的温度范围内拉曼频移和温度成线性关系。在相同的泵浦功率作用下,当温度较低时,拉曼光谱的级次较低, 低温对高阶斯托克斯光有抑制作用; 温度越低其阈值越高;而拉曼光谱的谱线宽度随温度的变化不是线性的,存在一个谱线宽度极大值点。理论和实验表明温度对光纤受激拉曼散射的光谱特性有直接的影响。     

On the interaction of stimulated spin-flip raman scattering and stimulated recombination radiation in InSb

We have studied the interaction of stimulated spin-flip Raman scattering and stimulated recombination radiation in n-InSb using a CW CO pump laser. A change in linewidth and output power of second Stokes spin-flip radiation is observed when the tuning curve of the first Stokes stimulated spin-flip radiation and the stimulated recombination radiation cross. The observations are explained using a simple rate equation model.     

由混合激发钠分子—原子系统产生的强度振荡变化的红外受激喇曼散射

本文报道以等频二步激发钠分子-原子系统,观测到强度随泵浦光的调谐而呈振荡变化的3P—4P受激喇曼散射,以及对应4D—4P和4F—3D跃迁的红外受激辐射和由四波混频产生的816.8～822.1nm区内可调谐相干辐射。文中对这些过程进行了分析讨论。     

Spectral broadening of continuous-wave monochromatic pump radiation caused by stimulated Brillouin scattering in optical fiber

We experimentally show that, when stimulated Brillouin scattering is generated in optical fiber by use of monochromatic cw pump radiation, the transmitted pump radiation exhibits spectral broadening that is much narrower than the classical homogeneous gain-narrowed Brillouin bandwidth. The bandwidth is practically independent of the pump strength, fiber characteristics, and the waveguide-induced inhomogeneously broadened bandwidth of the Stokes emission. We show that these properties arise from strong parametric coupling of the Stokes and pump signals in the pump-depletion region.     

SRS generation of anti-Stokes radiation under phase quasi-matching conditions

New methods of generation of anti-Stokes radiation of stimulated Raman scattering in media with changeable parameters of the third-order nonlinearity χ⁽³⁾ along the longitudinal coordinate are proposed. The conditions of obtaining phase quasi-matching in different media and reaching the maximum efficiency of conversion into the anti-Stokes component of stimulated scattering are determined by numerical methods. The dependence of the efficiency of energy transfer from the pump wave to the anti-Stokes wave on the ratio of intensities of the pump and Stokes waves at the input of the medium is studied. The models of the media in which the efficiency of generation of anti-Stokes radiation exceeds 30% are obtained. The results of the investigation can be used for the development of new efficient nonlinear optical devices upconverting the laser radiation frequency.     

XeCl laser generated infra-red SRS in barium vapour

Radiation at 2.36 μm is produced by stimulated electronic Raman scattering in barium vapour. The pump radiation is provided by a XeCl excimer laser. Photon conversion efficiencies of up to 1% are observed. The variations of the infra-red Stokes output with barium number density and with pump intensity are described.     

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.     

Generaton of tunable 16 μm radiation by stimulated hyper-raman effect in strontium vapour

The generation of tunable 16 μm radiation by stimulated hyper-Raman scattering from atomic strontium vapour is reported. The infrared radiation has a linewidth of 0.4 cm⁻¹ which corresponds to that of the nitrogen laser pumped dye laser used as a pump source. Due to relatively low pump intensity the infrared power was only 20 mW. However, the system is easily scalable to a higher conversion efficiency.     

The influence of silver nanoparticles on the stimulated luminescence of rhodamine 6G solutions

The influence of silver nanoparticles on the spontaneous and stimulated luminescence of rhodamine 6G molecules in aqueous solutions is studied. It is found that the laser photoexcitation of the dye solution gives rise to spontaneous fluorescence, which, with increasing pump power, transforms into stimulated laser radiation and superluminescence. Addition of silver nanoparticles to rhodamine 6G solutions enhances all types of luminescence and lowers the generation threshold for both types of the stimulated emission. The dependences of the laser radiation and superluminescence intensities on the concentration of silver nanoparticles correlate with the data on the spontaneous fluorescence.     

Rotational Raman scattering dependence on pump polarization

The influence of the ellipticity degree of the pump radiation polarization on threshold energies and energy conversion efficiencies of stimulated rotational Raman scattering (SRRS) are investigated in H₂ with a XeCl excimer laser, by using different focusing geometries. For the first time, it is shown that the dependence of SRRS on pump radiation polarization is also affected by the focusing geometry, i.e. whether low- or high-angle focusing is applied. The experimentally determined threshold energies as a function of the pump radiation polarization are in accordance with theory mainly at high-angle focusing geometries. It is also shown for the first time that gain suppression effects on vibrational Raman scattering have to be considered in understanding the experimental results. Received: 5 January 1999 / Final version: 10 September 1999 / Published online: 8 March 2000     

White-light parametric instabilities in plasmas

Parametric instabilities driven by partially coherent radiation in plasmas are described by a generalized statistical Wigner-Moyal set of equations, formally equivalent to the full wave equation, coupled to the plasma fluid equations. A generalized dispersion relation for stimulated Raman scattering driven by a partially coherent pump field is derived, revealing a growth rate dependence, with the coherence width sigma of the radiation field, scaling with 1/sigma for backscattering (three-wave process), and with 1/sigma1/2 for direct forward scattering (four-wave process). Our results demonstrate the possibility to control the growth rates of these instabilities by properly using broadband pump radiation fields.