氢和甲烷混合气体的受激喇曼散射

使用调Q Nd~(3+):YAG激光的二次谐波(532nm)作为泵浦源,探讨了氢和甲烷混合气体的受激喇曼散射效应。利用光学光谱分析仪(OSA)监测,在不同比例的混合气体中,观测到氢和甲烷各自的SRS谱线以及两种气体的联合谱线,[m,n,=0,|±1,±2,…];观察到斯托克斯和反斯托克斯的谱线频移。实验表明两种气体的混合使得氢和甲烷的受激喇曼散射过程发生了竞争和耦合。     

苯乙醇液芯光纤受激喇曼散射的红移和蓝移展宽

本文首次用调QYAG激光器的倍频光(λ=532.1nm)在苯乙醇液芯光纤中产生受激喇曼散射,观察到了4阶斯托克斯线和2阶反斯托克斯线.讨论了引起红移为主的斯托克斯线展宽的原因.     

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%.     

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.     

KGW 晶体外腔式高功率579 nm喇曼黄光激光器

报道了579 nm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808 nm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579.54 nm黄光激光输出.当脉冲信号重复频率为1 kHz、532 nm泵浦光最高平均功率为5.02 W、脉冲宽度为10.1 ns时,获得了最高平均功率2.58 W、脉冲宽度7.4 ns、峰值功率348.6 kW的579.54 nm二阶斯托克斯喇曼黄光激光输出;532 nm至579.54 nm的光-光转化效率为51.4%、斜率效率为54.8%,光束质量因子M_x-579.54²=5.829、M_y-579.54²=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.     

双折射光纤受激喇曼散射的研究

本文详细地研究了双折射光纤的受激喇曼散射.观测到9级斯托克斯受激喇曼谱.文中讨论和测试了阈值和频移与泵浦光偏振方向间的关系;当泵浦光偏振方向与光纤椭圆核的长轴或短轴平行时的传输损耗.并根据测得的阈值在理论上计算了各级斯托克斯线的喇曼增益系数.     

准分子激光束的喇曼整形

受激喇曼散射可以将紫外准分子激光辐射频移到特定的近紫外和可见光波长.采用喇曼整形技术还可以获得衍射极限发散角的斯托克斯输出.本文研究了注入光束质量对喇曼整形的影响,并求得不同氢压力下的喇曼增益系数和饱和参量.     

单模石英光纤中受激喇曼散射的研究

利用连续光纤激光器为泵浦源,对单模石英光纤中的受激喇曼散射进行了实验研究.在较低功率泵浦下,观察到由自发喇曼散射向受激喇曼散射演化的过程中,光谱不断变窄;当Stokes波信号功率较强时,观察到光谱峰值相对于泵浦波的频移量从440 cm－1转化到490 cm－1.在改进耦合系统后,不仅观察到一级喇曼频移,并且观察到了高阶Stokes光.在产生多级喇曼光谱时能量移动比较复杂,每两级的喇曼频移间隔并不完全相同.     

准分子激光束的喇曼组束

受激喇曼散射可以将紫外准分子激光辐射频移到特定的近紫外或可见光波长,采用喇曼整形技术可以改善斯托克斯光的光束质量,本文报道喇曼组束提高喇曼整形效率的实验结果.     

GaN基量子点结构的喇曼特征

采用量子力学的微扰理论，对GaN基量子点结构的喇曼频移进行分析。在喇曼实验中，观察InGaN／GaN量子点结构的E2和A1(LO)的模式，并发现实验中样品的喇曼频移与GaN的体材料相比，有着明显的红移。     

Stimulated Raman Scattering in Hydrogen Using Capilary Cell

Abstract

Stimulated Raman Scattering processes have been studied and intense Stokes and anti—Stokes laser lines have been observed in a capillary Raman cell filled with molecular hydrogen and pumped by the third harmonic of the Nd:YAG laser at wavelength ?D = 355 nm. Various parametric studies have been performed to establish an optimum condition for the best operation of the Raman laser. The observation of higher—order Stokes and anti—Stokes has been explained on the basis of four—wave mixing and/or cascade energy transfer processes.     

若丹明B荧光增强二硫化碳高阶受激喇曼散射

 利用若丹明B乙醇溶液的荧光改变了二硫化碳的一至三阶Stokes喇曼谱线的强度分布,选择性地增强了三阶Stokes喇曼谱线。在泵浦功率密度为~560MW^.cm^-2时,对染料摩尔浓度分别为~10^-5、cm^-5散射池和~10^-4、1cm散射池进行实验,观察到二硫化碳的三阶Stokes喇曼谱线与染料激光形成的共振增强现象及、二阶Stokes喇曼谱线的部分或完全耗尽。     

From anti‐Stokes photoluminescence to resonant Raman scattering in GaN single crystals and GaN‐based heterostructures

The progress on anti‐Stokes photoluminescence and Stokes and anti‐Stokes Raman scattering in GaN single crystals and GaN/AlN heterostructures is reviewed. Anti‐Stokes photoluminescence investigated in the past was primarily attributed to two‐photon absorption, three‐photon absorption, and phonon‐assisted absorption. On the other hand, anti‐Stokes Raman scattering was used to determine electron‐phonon scattering time and decay time constant for longitudinal‐optical phonons. In a typical high electron mobility transistor based on GaN/AlN heterostructures, strong resonances were reached for first‐order and second‐order Raman scattering processes. Therefore, both Stokes and anti‐Stokes Raman intensities were dramatically enhanced. The feasibility of laser cooling of a nitride structure has been demonstrated. Anti‐Stokes photoluminescence and Raman scattering have potential applications in upconversion lasers and laser cooling of nitride ultrafast electronic and optoelectronic devices.     

反斯托克斯拉曼光谱在BaTiO_3铁电相变研究中的应用

从理论上讨论了一阶和二阶斯托克斯与反斯托克斯拉曼散射截面的温度依赖关系;在２９３Ｋ至４０１Ｋ的温度范围内,测量了ＢａＴｉＯ３单晶斯托克斯和反斯托克斯过程的偏振拉曼光谱;通过对ＢａＴｉＯ３单晶斯托克斯和反斯托克斯拉曼光谱的综合分析,证实在Ｘ（ＺＺ）Ｙ几何配置下测量到的位于２７５和５１４ｃｍ－１处的强峰为一阶拉曼光谱。此结果支持了ＢａＴｉＯ３铁电相变机制的有序—无序模型。     

Cerussite,PbCO3 – a new Stimulated Raman Scattering (SRS)‐active crystal with high‐order Stokes and anti‐Stokes lasing

Orthorhombic PbCO₃, known as natural crystal cerussite, is presented as a new Stimulated Raman Scattering (SRS)‐active crystal. With picosecond laser pumping high‐order Raman‐induced χ⁽³⁾ generation is observed. All registered Stokes and anti‐Stokes sidebands in the visible and near‐IR are identified and attributed to the SRS‐promoting phonon mode A_1g of the carbonate group, with ω_SRS ≈ 1054 cm⁻¹. The first Stokes steady‐state Raman gain coefficient in the visible spectral range is estimated as well to a value not less than 4.6 cm·GW⁻¹.     

532 nm激光泵浦硝酸钡晶体产生外腔拉曼激光

 由于硝酸钡晶体具有很强的对称振动(频率1 047 cm^-1)和较高的拉曼增益,可以用来产生受激拉曼激光。采用单端泵浦的外置拉曼振荡腔与双棱镜分光装置进行了硝酸钡晶体拉曼激光实验,泵浦源为倍频Nd: YAG的532 nm激光,硝酸钡晶体通过水溶液降温法生长,尺寸为10 mm×10 mm×48 mm,采用特殊镀膜的腔镜对各阶斯托克斯光进行优化选择。在泵浦源达到65 mJ时,获得21 mJ一阶斯托克斯光,输出波长为563 nm,以及16 mJ的二阶斯托克斯光,输出波长为599 nm,受激拉曼散射SRS最大的整体转换效率（包含一阶、二阶斯托克斯光之和）为56.3%。     

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。     

Non‐degenerate second‐order scattering and difference combination bands in infrared‐pump/anti‐Stokes resonance Raman‐probe experiments

Non‐degenerate second‐order scattering due to interaction of infrared and ultraviolet pulses is observed in picosecond infrared‐pump/anti‐Stokes Raman‐probe experiments under electronic resonance conditions. We detected resonance hyper‐Rayleigh scattering at the sum frequency of the pulses as well as the corresponding frequency‐down‐shifted resonance hyper‐Raman lines. Nearly coinciding resonance hyper‐Raman and one‐photon resonance Raman spectra indicate conditions of A‐term resonance Raman scattering. Second‐order scattering is distinguished from transient anti‐Stokes Raman scattering of v = 1 to v = 0 transitions and v = 1 to v′ = 1 combination transitions by taking into account their different spectral and temporal behaviour. Separating these processes is essential for a proper analysis of transient vibrational populations. Copyright © 2007 John Wiley & Sons, Ltd.     

Anti‐Stokes Raman spectroscopy as a method to identify the metallic and semiconducting configurations of double‐walled carbon nanotubes

Although Raman spectra reveal, as a signature of double‐walled carbon nanotubes (DWCNTs), two radial breathing mode (RBM) lines associated with the inner and outer tubes, the specification of their nature as metallic or semiconducting remains a topic for debate. Investigating the spectral range of the RBM lines, we present a new procedure of the indexing of the semiconducting or metallic nature of the inner and outer shell that forms the DWCNT. The procedure exploits the difference between the intensities of recorded anti‐Stokes Raman spectrum and the anti‐Stokes spectrum calculated by applying the Boltzmann formulae to the recorded Stokes spectrum. The results indicate that the two spectra do not coincide with what should happen in a normal Raman process, namely, that there are RBM lines of the same intensity in both spectra, as well as RBM lines of higher intensity that are observed in the calculated spectrum. This discrepancy results from the surface‐enhanced Raman scattering mechanism that operates differently on metallic or semiconducting nanotubes. In this context, the analysis of the RBM spectrum can reveal pairs of lines associated with the inner/outer shell structure of DWCNT, and when the intensities between the recorded and calculated spectra coincide, the nanotube is metallic; otherwise, the nanotube is semiconducting. Copyright © 2014 John Wiley & Sons, Ltd.