共查询到18条相似文献,搜索用时 78 毫秒
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本文从理论和实验上分析了水的衰减系数及有效增益长度对受激布里渊散射(SBS)输出能量的影响。实验结果表明,衰减系数越小,SBS输出能量越高。由于脉宽压缩效应,当入射光能量足够高并且有效增益长度相对较长时,SBS易获得高能量而形成极高的峰值功率。一旦这种峰值功率超过受激拉曼散射(SRS)或者二阶SBS阈值,SBS就会作为一个新的激发源去激发SRS或者二阶SBS,从而消耗掉部分SBS的能量,所以会出现后向有效增益长度越长,SBS的输出能量越低的现象。
关键词:
受激布里渊散射
衰减系数
有效增益长度
脉宽压缩 相似文献
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ZHANG Yan-jun GAO Hao-lei FU Xing-hu TIAN Yong-sheng WANG Hui-min ZHANG Yi-nan 《光谱学与光谱分析》2018,38(1):285-289
受激布里渊散射会影响少模光纤传输系统中的信噪比、传输距离与传输容量,是影响传输系统入纤功率提高的重要因素。对阶跃型少模光纤的受激布里渊散射谱的阈值进行了研究,运用了布里渊散射谱、模式联运谱的数学模型对少模光纤散射特性进行了分析,探讨了少模光纤布里渊散射增益谱、阈值增益系数,以及光纤各参量对少模光纤阈值的影响。分析结果表明:SI-10阶跃型少模光纤中存在五种不同的传播模式,不同模式有各自的传输常数以及有效折射率,各模式相互作用导致模式展宽、增益降低,且布里渊散射谱峰值增益系数为3.9×10-11 m·W-1。阈值增益系数受到光纤传感距离的影响,在相对较短距离传输中阈值急速下降,且其趋势随长度增加渐趋平缓,当光纤长度达到22 km时阈值增益系数趋于常数18.1。少模光纤的阈值因光纤长度的递增而递减,且递减趋势渐缓趋于常数20.5 dBm;少模光纤不同模式受激布里渊散射的阈值也因光纤长度的递增而递减最终趋于常数,且不同模式的阈值因模式阶数的递增而递增;少模光纤的阈值随着光纤衰减系数和纤芯半径的递增而递增,且增加趋势缓慢增大。不同衰减系数的光纤其阈值在不同长度趋于常数,衰减系数越大受激布里渊散射阈值越大越容易趋于一常数。 相似文献
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受激布里渊散射(SBS)具有脉冲压缩的特性,受激布里渊散射的脉冲宽度随着抽运能量的增大而变小,在水中可以达到几百皮秒的量级.本文在实验上观察到一种受激布里渊散射的脉冲宽度随抽运能量增大而变大的现象,这里称之为反常压缩.SBS的脉冲反常压缩和脉冲压缩与抽运光的强弱会聚情况有关.利用数值模拟,模拟了强弱会聚情况下抽运光在水中的传输规律,强弱会聚情况的抽运光对受激布里渊散射形成的有效增益长度不同:抽运光强会聚时有效增益长度短,形成SBS脉冲宽度的反常压缩;弱会聚时有效增益长度长,也就是正常的SBS脉冲压缩. 相似文献
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当酒精的弱增益拉曼模式处于罗丹明640染料分子的激光增益范围时,在由悬垂液滴构成的圆形谐振腔中,观察到乙醇分子C—H伸缩系列模中多个弱增益拉曼模式的受激拉曼散射(SRS)光谱.随着抽运光的增强,迅速增长的强增益拉曼模式的受激辐射抑制了其他弱增益模式的SRS,并导致染料激光的完全淬灭.通过分析圆形腔腔模的光子速率方程和激光染料分子的三能级粒子数速率方程,解释了观察到的实验现象.
关键词:
受激拉曼散射
悬垂液滴
弱拉曼增益模式
激光增益 相似文献
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结合环形腔理论,运用蒙特卡罗法模拟了光子在介质中的随机行走。研究了倍频Nd:YAG(脉宽6 ns,频率20 Hz)脉冲激光器作为泵浦光,在TiO2 / 若丹明 B有机增益介质中,散射微粒的颗粒密度和泵浦光面积对随机激光器阈值强度的影响。模拟结果表明:随机激光阈值和光子在增益介质中的随机行走路程长度和光子通过边界返回增益区和非增益区的几率有关。随着泵浦光面积的增加,随机激光器阈值降低;增益介质中散射颗粒密度的增加降低了随机激光器的阈值。 相似文献
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受激布里渊散射效应具有光谱线宽窄、频率稳定和增益方向敏感等优点,常用于激光器,慢光产生和微波光子滤波器等.本文基于As2S3硫系玻璃、以SiO2为衬底设计了一种亚微米尺寸的带空气狭缝倒置结构脊型波导结构,具有高达8.22×104 W–1·m–1的后向受激布里渊散射增益系数.研究显示在该结构的同种光学和声学模式下,更小的声光场有效模场面积具有更高的后向受激布里渊散射增益系数.还分析了硫系玻璃的光学损耗对后向受激布里渊散射的影响,发现当波导长度超过最优值后,斯托克斯光波功率开始下降,而增大泵浦光功率不仅可以提高斯托克斯光波功率的极大值,同时还会增大波导长度的最优值.当所输入的泵浦光功率为20 mW时,受激布里渊散射增益达到100 d B波导长度仅需要2 cm,这非常有利于光子器件的片上集成. 相似文献
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本文研究了不同外部环境中原子气体在强激光抽运下的相干Raman散射光谱, 通过对固定无反弹原子气体(不考虑外部自由度)和自由原子气体增益光谱的理论计算, 得到了和Mollow实验结果基本一致的光谱曲线.通过与Mollow谱线结构的比较, 揭示了在微阱约束情况下原子气体存在不同于以上两种环境的高增益光谱, 该谱线直接反应了约束阱的性质, 谱线呈等间距梳状结构, 谱线尖锐分辨率高, 和传统的冷原子气体散射增益光谱的实验结果相比较有更大量级的光增益现象. 论文还分析了散射谱线增益的物理机理, 清晰地给出了约束情况下原子增益谱线的非线性Raman共振条件. 相似文献
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《光学学报》2017,(12)
根据CCD侧向散射激光雷达(Clidar)及Mie散射理论,建立侧向散射光强分布与PM2.5浓度的关系模型,并分析测量误差。在研究过程中,搭建以波长为532nm的激光器为光源、CCD为接收器的Clidar PM2.5浓度测量系统装置;将获取的侧向散射回波信号图与BAM-1020颗粒物监测仪记录的PM2.5浓度进行对比,建立高、低增益下各等级模型的关系式。将高、低增益各等级模型的PM2.5预测值与实际测量结果进行对比,得到各模型的平均误差、残差方差和综合偏差率统计量,并确定最佳反演精度模型的增益和等级i值。结果表明:当PM2.5浓度在0~70μg·m-3范围内时,高增益模型的反演精度高于低增益模型;对于高增益模型,S(20)模型的反演精度最高。 相似文献
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Gain/loss effect on bright solitary wave in a cigar-shaped attractive condensate in the presence of expulsive parabolic potential
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<正>Taking into account both gain/loss and time-dependent atomic scattering length,this paper analytically derives an exact bright solitary wave in a cigar-shaped attractive condensate in the presence of an expulsive parabolic potential. Due to the balance of the scattering length and gain/loss,the bright solitary wave is shown to have constant amplitude. Especially,it is found that the bright solitary wave is accelerated by expulsive force,whose velocity can be modulated by changing the axial and transverse angular frequencies.The results are in good agreement with the experimental observations by Khaykovich et al(2002 Science 296 1290). 相似文献
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A multimode model of a continuously pumped atom laser is shown to be unstable below a critical value of the scattering length. Above the critical scattering length, the atom laser reaches a steady state, the stability of which increases with pumping. Below this limit the laser does not reach a steady state. This instability results from the competition between gain and loss for the excited states of the lasing mode. It will determine a fundamental limit for the linewidth of an atom laser beam. 相似文献
14.
Picosecond stimulated Raman scattering in crystals 总被引:1,自引:0,他引:1
T. T. Basiev P. G. Zverev A. Ya. Karasik V. V. Osiko A. A. Sobol’ D. S. Chunaev 《Journal of Experimental and Theoretical Physics》2004,99(5):934-941
The comparative values of the peak and integral cross sections of spontaneous Raman scattering and the optical dephasing time of molecular vibrations were determined for several oxide crystals by spontaneous Raman spectroscopy. The spectral, time, and energy parameters of stimulated Raman scattering (SRS) were measured for ten crystals using picosecond YLF: Nd laser pumping with a radiation wavelength of 1047 nm. An analysis of the experimental dependence of the threshold energy of pumping SRS on the integral and peak cross sections of spontaneous Raman scattering showed that the SRS gain increment explicitly depended on the integral cross section and was independent of the peak cross section of spontaneous Raman scattering as the ratio between the pumping pulse width (11 ps) and the time of optical dephasing of molecular vibrations changed from 0.42 to 9.3. The gain coefficients of steady-state stimulated Raman scattering under threshold stimulated Raman scattering conditions were determined for all the crystals studied on the basis of the measured threshold SRS pumping energies, the duration and width of the spectrum of pulses, the nonlinear interaction length, the intensity of pumping, and the theoretical dependences that relate the steady-state and transient SRS gain increments. The steady-state SRS gain coefficients obtained in this work fitted well a linear dependence on the peak cross sections of spontaneous Raman scattering, which substantiated the correctness of our analysis and measurements. 相似文献
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V. Jukna G. Tamo?auskas G. Valiulis M. Aputis M. Puida F. Ivanauskas A. Dubietis 《Applied physics. B, Lasers and optics》2009,97(1):175-179
We have studied filamentation of 1-ps laser pulses in a scattering medium (aqueous suspension of 2-μm polystyrene microspheres)
and compared filamentation dynamics to that in pure water. Our results indicate that light scattering does not alter filamentation
dynamics in general, but rather results in farther position of the nonlinear focus, shorter filament length, and the development
of speckle structure in the peripheral part of the beam. The experimental observations are qualitatively reproduced by the
numerical model which accounts for diffraction, self-focusing, multiphoton absorption, and light scattering introduced through
a stochastic diffusion and diffraction term. 相似文献
17.
Jinyong Leng Shengping Chen Wuming Wu Jing Hou Xiaojun Xu 《Optics Communications》2011,284(12):2997-3003
High power operation of single-frequency Raman fiber amplifiers is usually limited by the onset of stimulated Brillouin scattering. A theoretical investigation on single-frequency Raman fiber amplifier limited by stimulated Brillouin scattering is presented in this paper, based on the intensity equations combining stimulated Brillouin scattering and stimulated Raman scattering. A combination of methods is proposed to increase the output power of single-frequency Raman fiber amplifier. These methods include applying a suitable pump scheme according to the fiber length and seed signal power, using short gain fibers, utilizing a multiple-stage scheme and providing suppression of stimulated Brillouin scattering. 相似文献
18.
Emission spectra of multimode lasers are very sensitive to spectrally selective extinction in their cavity. This phenomenon
allows the quantitative measurement of absorption. The sensitivity of measurements of intracavity absorption grows with the
laser pulse duration. The ultimate sensitivity obtained with a cw laser is set by various perturbations of the light coherence,
such as quantum noise, Rayleigh scattering, four-wave mixing by population pulsations, and stimulated Brillouin scattering.
It depends on the particular laser type used, and on its operative parameters, for example pump power, cavity loss, cavity
length, and length of the gain medium. Nonlinear mode-coupling dominates the dynamics of lasers that feature a thin gain medium,
such as dye lasers, whereas Rayleigh scattering is more important in lasers with a long gain medium, such as doped fibre lasers,
or the Ti:sapphire laser. The highest sensitivity so far has been obtained with a cw dye laser. It corresponds to 70000 km
effective length of the absorption path. The ultimate spectral resolution is determined by the spectral width of mode emission,
which is 0.7 Hz in this dye laser. High sensitivity and high temporal and spectral resolution allow various practical applications
of laser intracavity spectroscopy, such as measurements and simulations of atmospheric absorption, molecular and atomic spectroscopy,
process control, isotope separation, study of free radicals and chemical reactions, combustion diagnostics, spectroscopy of
excited states and nonlinear processes, measurements of gain and of spectrally narrow light emission. Intracavity absorption
in single-mode lasers shows enhanced sensitivity as well, although not as high as in multimode lasers.
Received: 10 May 1999 / Published online: 29 July 1999 相似文献