Spatial, Spectral, and Temporal Characteristics of Stimulated Light Scattering in Water

Spatial, temporal, and spectral characteristics of stimulated light scattering (SS) in water were investigated in both nano- and picosecond ranges under different experimental conditions and compared with the analogous characteristics of stimulated light scattering in other liquids. Stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) of light were studied. The results obtained provide useful information on the structure of water, its purity, and additions, which can result in its pollution. The excitation conditions of stimulated light scattering (SS) in one spatial mode and with maximum pulse energy conversion were determined. It is shown that stimulated light scattering can be successfully applied to control water quality (and it can be done very fast) as well as for information processing, i.e., the amplitude–phase structure of complex light fields can be registered in water as a dynamic hologram and reconstructed in real time.     

Fundamental Studies of Stimulated Raman Scattering and Adaptive Optics on the Basis of Stimulated Light Scattering

Some results associated with the fundamental investigations of stimulated scattering of light in various media are reported. A number of problems of adaptive optics based on stimulated scattering is studied. Concrete results of experimental investigations of physically important characteristics of conventional (spontaneous) and stimulated Raman scattering are presented and discussed. Among them are the scattering indicatrix and the relations between the phases of laser radiation incident on a substance and stimulated scattering. These results were first obtained in the G. S. Landsberg Optical Department of the P. N. Lebedev Physical Institute of the Russian Academy of Sciences. Data on excitation sources and the radiation detection technique are systematized. The main characteristics of spontaneous Raman scattering and forward and backward stimulated Raman scattering (energy parameters, pulse duration, pulse shape, divergence, brightness, spectral width, far- and near-field intensity distributions) are presented. The results on dynamic holography, phase conjugation of light in stimulated scattering, and reconstruction and recording of information (images) with the help of amplifying dynamic holograms are presented. The physical mechanisms responsible for the interference field recording and the phase conjugation of pump radiation in stimulated light scattering are discussed. The data on phase conjugation for stimulated scattering excited by picosecond optical pulses and the results associated with the effect of excitation geometry on the optical phase conjugation in the case of stimulated scattering excited by nanosecond pulses are presented.     

多色非相干光入射ICF黑腔受激布里渊散射分析

为研究多色非相干激光入射ICF黑腔的受激布里渊散射（SBS）和受激拉曼散射（SRS）发展情况,建立了一维受激散射稳态谱分析模型,并发展了相应的数值模拟程序。分析了不同频率激光激发的受激散射光通过共用等离子体波耦合的物理图像以及影响背散光谱的物理因素。针对波长差0.3 nm的等强度双色光入射封底金腔的SBS进行了模拟分析,结果表明：采用双色光有效抑制了SBS;SBS光谱劈裂成间距为0.3 nm的两个峰;波长较长的入射光对应的SBS光获得了较大的增益;如果固定激光总强度和总带宽,则存在抑制SBS的最优光束数目。     

神光Ⅲ原型装置的黑腔靶背向散射光测量技术

在惯性约束聚变研究中,为研究激光等离子体互作用产生的受激布里渊与受激拉曼散射光(SRS),基于神光Ⅲ原型装置利用新的背向散射诊断系统对真空黑腔靶与充气黑腔靶以及有无束匀滑效果情况下的散射光光谱进行了测量。实验发现,在相同条件下,充气黑腔靶SRS散射光比真空黑腔靶大,在终端光学组件中使用束匀滑效果后也能降低散射光。诊断系统记录的散射光强度及光谱的时间变化过程对研究激光等离子体相互作用提供了重要的数据支撑。     

神光Ⅲ原型装置的黑腔靶背向散射光测量技术

在惯性约束聚变研究中,为研究激光等离子体互作用产生的受激布里渊与受激拉曼散射光(SRS),基于神光Ⅲ原型装置利用新的背向散射诊断系统对真空黑腔靶与充气黑腔靶以及有无束匀滑效果情况下的散射光光谱进行了测量。实验发现,在相同条件下,充气黑腔靶SRS散射光比真空黑腔靶大,在终端光学组件中使用束匀滑效果后也能降低散射光。诊断系统记录的散射光强度及光谱的时间变化过程对研究激光等离子体相互作用提供了重要的数据支撑。     

Scattering of light waves by electron electrostatic waves in laser produced plasmas

The propagation of light waves in an underdense plasma is studied using one-dimensional Vlasov-Maxwell numerical simulation.It is found that the light waves can be scattered by electron plasma waves as well as other heavily and weakly damping electron wave modes,corresponding to stimulated Raman and Brilluoin-like scatterings.The stimulated electron acoustic wave scattering is also observed as a high scattering level.High frequency plasma wave scattering is also observed.These electron electrostatic wave modes are due to a non-thermal electron distribution produced by the wave-particle interactions.The collision effects on stimulated electron acoustic wave and the laser intensity effects on the scattering spectra are also investigated.     

Bursting behaviours in cascaded stimulated Brillouin scattering

Stimulated Brillouin scattering is studied by numerically solving the Vlasov-Maxwell system. A cascade of stimulated Brillouin scattering can occur when a linearly polarized laser pulse propagates in a plasma. It is found that a stimulated Brillouin scattering cascade can reduce the scattering and increase the transmission of light, as well as introduce a bursting behaviour in the evolution of the laser-plasma interaction. The bursting time in the reflectivity is found to be less than half the ion acoustic period. The ion temperature can affect the stimulated Brillouin scattering cascade, which can repeat several ×at low ion temperatures and can be completely eliminated at high ion temperatures. For stimulated Brillouin scattering saturation, higher-harmonic generation and wave-wave interaction of the excited ion acoustic waves can restrict the amplitude of the latter. In addition, stimulated Brillouin scattering cascade can restrict the amplitude of the scattered light.     

Stimulated Raman scattering of light in artificial opal filled by water

We investigate stimulated scattering of light in globular photonic crystals infiltrated by water. Excitation of stimulated scattering of light is realized using powerful ultrashort (70 ps) laser pulses with an energy of 35 mJ and a frequency repetition of 15 Hz. We use the second-harmonic generation (532 nm) of the master oscillator and amplifier with a wavelength of 1064 nm. The photonic crystals under study are artificial opals filled by water or ethanol. We characterize the sample structures employing an electronic microscope along with the fiber-optics reflectance-spectroscopy technique. Photonic crystals have a stop band near the spectral positions of the exciting line (532 nm) and the first satellite of stimulated Raman scattering of light in water (649 nm). We observe a substantial reduction of the threshold of stimulated Raman scattering of light in water-infiltrated artificial-opal matrices in comparison with that of pure water. Such a reduction is explained as the result of a sharp increase in the photonic density of states near the stop-band edges of investigated photonic crystals. The reduction in the threshold of stimulated Raman scattering of light in water-infiltrated artificial-opal matrices opens up the opportunity to observe stimulated Raman scattering in numerous water media, including water solutions, biological and medical samples, heavy waters, and others.     

Comparison of the amplification coefficients of conjugate and non-conjugate waves in stimulated light scattering

The energies of conjugate and non-conjugate waves in stimulated light scattering were experimentally measured simultaneously. The level of spontaneous scattered light was measured with the same setup. These data allow to compare amplification coefficients of conjugate and non-conjugate waves. The coefficient for the conjugate wave proved to be two times greater then for the non-conjugate wave, assuming that ～√N_m modes are excited inside the light guide with carbondisulfide, which was used as scattering medium. N_m is the maximal number of light guide modes which can propogate within a solid angle occupied by scattering light.     

New mechanisms of slow light and their applications

The last decade has been of great significance for the development of slow light technology. Electromagnetically induced transparency (EIT), coherent population oscillation (CPO), stimulated Brillouin scattering (SBS), stimulated Raman scattering (SRS), soliton collision, and photonic crystal waveguides have been used to slow down the velocity of light. In this paper, some important theoretical and technical developments of slow light technology that occurred over the last decade are discussed. Novel technologies for slowing down the velocity of light and their primary applications are introduced in detail. In addition, the future developing trends of slow light and its potential applications, especially in optical fiber sensors, are also forecasted and proposed in this paper.     

Reflection and scattering from laser-irradiated solid targets at a wavelength of 0.44 μm

Studies of the reflectivity and spectral behaviour of the light scattered from plane solid targets irradiated with the third harmonic of the iodine laser (λ = 0.44 μm) in the intensity range 10¹² to 10¹⁵ W/cm² are reported. The complex spectra of the scattered light observed with normally and obliquely incident laser light provide evidence of stimulated scattering processes. The results are compared with current theories on stimulated Brillouin scattering.     

一种用弱信号光调制的宽带光纤拉曼相干光源

本文考察了光纤中外加可调谐信号光条件下的受激拉曼散射现象,提出一种新的宽带光纤拉曼相干光源的设想。这种光源是利用波长可调的弱信号光来调制固定波长的强泵浦光在光纤中产生的高阶受激拉曼散射,使得高阶受激拉曼散射Stokes峰值波长随弱信号光的波长改变而改变。从而获得一个输出均匀而频带又比信号光宽得多的高强度相干光。     

类胡萝卜素的分子光谱研究

类胡萝卜素是含有9个CC共轭双键的短链多烯类生物分子. 特殊的分子结构, 使其不仅在光采集, 光防护, 防癌, 抗癌等生物学领域有重要应用, 而且在分子导线, 光开关, 滤光器等光电器件研制中也有重要的非生物学应用. 本文对它的分子光谱进行研究和总结, 结果表明, 类胡萝卜素具有宽带荧光, 将其用于荧光增强受激拉曼散射可以获得宽带受激拉曼散射; 电子能隙随温度降低而收缩, 电子吸收光谱红移, 这特性使它能研制优质半导体元件; 极大的拉曼活性和三阶非线性系数, CC键基频拉曼散射截面可以比普通分子大10个数量级, 和频、倍频拉曼散射强度也很高, 低温下与基频强度比可达0.5. 类胡萝卜素分子的这些光谱特性对多烯类分子结构、性能研究及其在非生物学中的应用有重要参数价值.     

双折射光纤受激拉曼散射偏光特性的实验研究

对椭圆芯光纤受激拉曼散射偏光特性进行了系统的实验研究。实验巾观察到8级斯托克斯线和2级反斯托克斯线,对不同偏振态的抽运光激励下各级斯托克斯线的偏振特性、拉曼频移等参量进行了分析,并给出了经验公式。其结果与实验数据符合良好。实验表明,双折射光纤受激拉曼谱的各级斯托克斯线的偏振状态不但与拉曼介质有关还与抽运光的偏振态有关,入射抽运光偏振态对低阶次的斯托克斯线拉曼频移的影响较小,而对高级斯托克斯线拉曼频移影响较大。     

Light beams wavefront reconstruction and real volume image reconstruction of the object at the stimulated Raman scattering

In the present work volume real image reconstruction at the Stimulated Raman Scattering (SRS) of the object, illuminated by laser light, has been observed experimentally for the first time in the large wavelength diapason. The thresholds and exciting power density intervals for observation of the reconstruction differ for different wavelengths and kinds of stimulated scattering. The image reconstruction at stimulated scattering has been shown to be consequence of the wavefront reconstruction effect at SRS, revealed by the authors in 1970. The phenomenon of the image reconstruction at stimulated scattering has some common features with the holograms registration and reconstruction, but there is no known holography method, quite similar to the discovered effect.     

皮秒激光抽运高压H_2的受激拉曼散射研究

利用Nd :YAG锁模序列脉冲激光 (10 6 4nm)抽运充有高压H2 的拉曼池 ,输出光束经棱镜分光后投射在屏上 ,在可见光及近紫外光区用彩色胶卷摄得 15个受激拉曼散射光斑 ;经 1m光栅摄谱仪摄谱 ,在 36 5— 6 0 5nm波长范围内得到 6 5条受激拉曼谱线 .通过实验结果与理论计算值的比较 ,证明除了H2 的振动拉曼频移量 4 15 4 6cm- 1 外 ,还有多个振动及转动拉曼频移量共同参与作用 ,从而产生了从紫外到红外众多波长的受激拉曼散射光 .     

基于受激布里渊散射的宽带宽和高精度的微波频率瞬时测量

提出了一种基于受激布里渊散射效应的瞬时频率测量方法.未知信号经过强度调制作为泵浦光,矢量网络分析仪产生的信号经过相位调制作为扫描信号光,当泵浦光和扫描信号光之间满足相位匹配条件时,受激布里渊散射效应发生并实现相位调制到强度调制的转换,未知信号的频率被测量.实验验证可以测量0.5 GHz-27 GHz的微波信号的频率,最大误差小于20 MHz.     

高非线性微结构光纤中基于受激布里渊散射的慢光延迟

全光连续可调的慢光技术在全光网络和光信息处理等领域具有重要的应用前景. 利用自行设计并拉制的高非线性微结构光纤, 实验研究了基于受激布里渊散射的可调谐慢光延迟. 采用单抽运光和单级延迟方案, 当抽运光功率为162.6 mW时, 在长度为120 m的高非线性微结构光纤中获得了最大76 ns的延迟量, 相当于0.76个脉冲宽度. 通过调节抽运光功率的大小, 可以实现对慢光延迟量的可调谐.该慢光延迟方案具有延迟量大、 全光可调谐及与现有光通信系统兼容等优势. 关键词： 慢光 微结构光纤 受激布里渊散射