基于偏振探测的CARS非共振背景抑制与分离

为消除非共振背景干扰,提高相干反斯托克斯拉曼散射测量精度,研究了基于偏振探测的相干反斯托克斯拉曼散射非共振背景抑制与分离.首先,从理论上证明了相干反斯托克斯拉曼散射信号强度只取决于三阶非线性极化率共振部分,而与非共振部分无关,并且三阶极化率共振部分与非共振部分偏振方向不一致,为偏振相干反斯托克斯拉曼散射提供了理论支撑;然后,以平面火焰炉温度场为研究对象,设计了偏振相干反斯托克斯拉曼散射探测系统实施方案,并与热电偶、常规相干反斯托克斯拉曼散射两种方法在相同条件下开展了温度测量对比实验.实验结果表明:常规相干反斯托克斯拉曼散射方法的测量相对误差优于7%,测量相对不确定度优于7%;偏振相干反斯托克斯拉曼散射方法的测量相对误差优于4%,测量相对不确定度优于5%;相同工况条件下与常规相干反斯托克斯拉曼散射相比,偏振相干反斯托克斯拉曼散射最接近均值的拟合光谱更加平滑.偏振相干反斯托克斯拉曼散射具有更小的拟合误差,是一种更为有效的相干反斯托克斯拉曼散射诊断方法.     

Ce:BaTiO3晶体电光和二倍频系数的拉曼散射测量

从极性晶体晶格振动的理论出发,推导出正交系以上晶系的晶体的拉曼散射效率与晶体电光系数和二倍频系数的关系,测量了Ｃｅ：ＢａＴＩＯ３和ＢａＴｉＯ３晶体各纵、横模的偏振拉曼谱。在此基础上,计算出这两种晶体的电光系数ｒ３３、ｒ５１和二倍频系数ｄ３３、ｄ１５。结果表明：掺微量Ｃｅ元素对ＢａＴｉＯ３晶体电光系数和二倍频系数影响不大。     

荧光物质光学性质对受激拉曼散射的影响

荧光在受激拉曼散射中能发挥良好的外部种子作用,可以极大幅度降低受激拉曼阈值、增加散射模式的强度。将溶解了荧光物质的CS2溶液作为液芯光纤的芯液体进行荧光增强受激拉曼散射研究。结果表明,很小能量(1.86 mJ)的激光激发就能获得较强的斯托克斯和反斯托克斯拉曼光。以荧光光谱范围较小的罗丹明B(rhodamine B)作为荧光种子,只获得了强度较高的一阶反斯托克斯谱线和强度较低的一阶斯托克斯谱线;以荧光光谱范围很大的β-胡萝卜素(β-carotene)作为荧光种子,很小的抽运能量就获得了7阶斯托克斯光谱。因此可以选用不同光学性质的荧光种子来选择性增强受激拉曼散射的某一散射模式。     

四方相BaTiO_3及BaTiO_3：Ce的拉曼散射特性研究

四方相ＢａＴｉＯ＿３及ＢａＴｉＯ＿３：Ｃｅ的拉曼散射特性研究王瑞敏，赵铁男，刘竟青，朱恪，朱镛，吴星，林筠（中国科学院物理研究所北京１０００８０）（陕西师范大学物理系西安７１００６２）（中国地质大学北京１０００８１）本文报道了在室温下ＢａＴｉＯ＿３及...     

相方相BaTiO3及BaTiO3：Ge的拉曼散射特性研究

本文报道了在室温下ＢａＴｉＯｅ及ＴｉＯ３：Ｃｅ的拉曼谱的特点，着重讨论了前向散射配置下两个Ａ１（ＴＯ）模（位于２７５ｃｍ＾－１和５１６ｃｍ＾－１左右）出现在Ａ１（ＴＯ）谱中的原因，通过设计特别的前向散射实验得到了此配置下由于晶体出射两对入射光的反射造成的背向散射的强度。在ＢａＴｉＯ３的前向散射谱中扣除了背向散射面对人入射光的反射造成的背向散射的强度。在ＢａＴｉＯ３的前向散射谱中扣除了背向散射信号后     

YVO4晶体的高效受激拉曼散射

报道了YVO4晶体在532 nm、30 ps脉冲下的的高效受激拉曼散射。采用腔外单次通过方式测量了不同长度YVO4晶体1阶斯托克斯受激拉曼散射的阈值,并得到该晶体的稳态增益系数为16.0±0.5 cm/GW。实验中观察到2阶斯托克斯线(558.6 nm5、87.8 nm)和1阶反斯托克斯线(508.0 nm),受激拉曼散射的整体转换效率高于50%。     

四方相BaTiO_3:Ce及Mn离子注入的BaTiO_3:Ce的拉曼散射的研究

四方相ＢａＴｉＯ３：Ｃｅ及Ｍｎ离子注入的ＢａＴｉＯ３：Ｃｅ的拉曼散射的研究刘玉龙朱恪张昊朱镛（中科院物理研究所北京１０００８０）赵金涛（张掖师范高等专科学校物理系甘肃张掖７３４０００）萧季驹（香港城市大学物理及材料科学系香港九龙）ＲａｍａｎＳｐｅｃ...     

双光子荧光与相干反斯托克斯拉曼散射显微成像技术的实验研究

双光子荧光与相干反斯托克斯拉曼散射同属于三阶非线性效应,二者之间的差异与联系是一个值得研究的问题.本文基于自行搭建的超连续谱近红外宽带相干反斯托克斯拉曼散射显微成像系统进行光谱成像,同时通过理论与实验对比分析了双光子荧光与相干反斯托克斯拉曼散射图像存在差异的原因.结果表明,具有亚微米以上横向分辨率的相干反斯托克斯拉曼散射成像系统,可以使用较大尺寸的荧光珠进行双光子荧光成像,通过解卷积得到双光子荧光成像的系统分辨率,并将它近似等效于相干反斯托克斯拉曼散射成像系统的当下分辨率.如果需要得到相干反斯托克斯拉曼散射成像系准确的分辨率结果,就必须使用尺寸比相干反斯托克斯拉曼散射成像系统实际分辨率小的球形样品进行实验测量.     

铊系超导单昌的低温生长

采用蠕爬型助熔剂ＣａＯ－ＣｕＯ和蒸发型复合助熔剂ＣａＯ－ＣｕＯ－ＮａＣｌ来制备Ｔｌ－Ｂａ－Ｃａ－Ｃｕ－Ｏ超导单晶，生长炉最高温度８９０℃和８５０℃，因而实现了铊系单晶的低温生工。生长出的单晶分别是典型尺寸为２．０×１．５×０．２ｍｍ＾３，Ｔｃ在１００Ｋ与１１９Ｋ之间的Ｔｌ－２２１２相单晶和尺寸为１．２×１．０×０．１ｍｍ＾３。Ｔｃ约为１１５Ｋ的Ｔｌ－２２２３相超导单晶。     

四方相BaTiO_3及BaTiO_3∶Ce的拉曼散射特性研究

本文报道了在室温下ＢａＴｉＯ３及ＢａＴｉＯ３：Ｃｅ的拉曼谱的特点，着重讨论了前向散射配置下两个１Ｉ（ＴＯ）模（位于２７５ｃｍ－１和５１６ｃｍ－１左右）出现在Ａ１（ＴＯ）谱中的原因。通过设计特别的前向散射实验得到了此配置下由于晶体出射面对入射光的反射造成的背向散射的强度。在ＢａＴｉＯ３的前向散射谱中扣除了背向散射信号后，两个宽峰基本减掉，而掺Ｃｅ后经同样扣除背向散射信号两宽峰却依然很强。这样便证明了它们在前向散射中的出现与杂质有关系。在ＢａＴｉＯ３扣除背向散射后的谱中，还首次观察到一个位于４９２ｃｍ－１的峰。掺Ｃｅ后晶体的吸收曲线有很大变化，本文还讨论了吸收对散射强度的影响。     

LDS751染料的受激喇曼散射

报道了用532nm激光抽运LDS751染料产生720—780nm可调谐染料激光输出的同时,观察到喇曼频移为102和45cm-1的反斯托克斯线,前者谱线较强,后者较弱.与这两条强线对应的斯托克斯线未能观察到.另外,还观察到喇曼频移为34cm-1的一级和二级斯托克斯线与反斯托克斯线 关键词： LDS751染料 受激喇曼散射 喇曼位移 斯托克斯线 反斯托克斯线     

碳纳米管的拉曼光谱及其温度效应

在室温下首次观察到碳纳米管的四级拉曼光谱，并且发现碳纳米管的Ｄ峰和Ｄ＊峰的斯托克斯线和反斯托克斯线频率不一致。此外，还发现碳纳米管的拉曼特征峰频率严重依赖样品的温度，随着温度增加，碳纳米管拉曼特征峰频率下移，频移与温度变化成线性关系。     

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.     

Accurate intensity calibration for low wavenumber (−150 to 150 cm−1) Raman spectroscopy using the pure rotational spectrum of N2

We report on an accurate intensity calibration method for low wavenumber Raman spectroscopy. It uses the rotational Raman spectrum of N₂. The intensity distributions in the rotational Raman spectra of diatomic molecules are theoretically well established. They can be used as primary intensity standards for intensity calibration. The intensity ratios of the Stokes and anti‐Stokes transitions originating from the same rotational levels are not affected by thermal population. Taking the effect of rotation–vibration interactions appropriately into account, we are able to calculate these intensity ratios theoretically. The comparison between the observed and calculated ratios of the N₂ pure rotational spectrum provides an accurate relative sensitivity curve (error ~5 × 10⁻⁴) in the wavenumber region of −150 to 150 cm⁻¹. We determine the temperature of water solely from the low wavenumber Raman spectra, using a thus calibrated spectrometer. The Raman temperature shows an excellent agreement with the thermocouple temperature, with only 0.5 K difference. The present calibration technique will be highly useful in many applications of low wavenumber quantitative Raman spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

Growth profile of stimulated Raman anti‐Stokes scattering influenced by fluorescence seeding in liquid‐core optical fiber

We demonstrated the growth profile of stimulated Raman anti‐Stokes scattering (SRS) of carbon disulfide (CS₂) influenced by fluorescence seeding of all‐trans‐β‐carotene and rhodamine‐B (RhB) in liquid‐core optical fiber (LCOF). The pump energy which was needed to build up the first‐order anti‐Stokes radiation of CS₂ solutions with the fluorescence seeding was lower than that of CS₂ solutions without fluorescence seeding because of the fluorescence enhancement effect on the intensity of the first‐order Stokes radiation. The first‐order anti‐Stokes radiation of the RhB solution (10⁻⁸ M ) was built up at a lower pump energy than that of the all‐trans‐β‐carotene solution (10⁻⁶ M ), and the intensity of the first‐order anti‐Stokes radiation of the RhB solution was higher than that of the all‐trans‐β‐carotene solution. Simultaneously, the coupled wave differential equations were obtained by the theoretical derivation, and the growth profile of the first‐order anti‐Stokes radiation was theoretically calculated with and without the fluorescence seeding by these equations. Copyright © 2009 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.     

Analyzing ultrafast multiplex coherent anti‐Stokes Raman spectra with picosecond probing

This article reports an efficient method to simulate time and frequency resolved coherent anti‐Stokes Raman scattering spectra measured with picosecond pump and probe fields and ultrashort Stokes pulses. A systematic comparison of measured and simulated time and frequency dependent data is presented for carbon tetrachloride, chloroform, cyclohexane, octane, and poly(methyl methacrylate). While the first compound exhibits no Raman active modes in the considered spectral region of the CH‐stretch vibrations, the other ones show Raman spectra of increasing complexity. Vibrational frequencies and homogeneous dephasing rates are extracted by fitting explicit analytical formulas to the recorded data. Interference between nonresonant and resonant contributions to the nonlinear polarization is taken fully into account. The ability to measure the influence of inhomogeneous broadening is discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

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.