硅桥红外辐射单元温度的显微拉曼测定

本文采用显微拉曼光谱实验的方法对红外目标模拟器中的重掺杂Si电阻微桥单元进行了绝对温度的测量 ,并根据斯托克斯与反斯托克斯强度与温度关系以及Raman峰位移动与温度依赖关系两种方法确定温度 ,保证了所测温度的可靠性。针对Si桥建立相应的Raman模型 ,选择合适的物理参数 ,最终得到了反映Si桥工作特性的电流 -温度关系。此外 ,通过对Si桥的空间分辨的测量实验 ,得到了Si桥上的温度分布状况 ,对了解其电阻、热导及氧化等特性十分有用。所有结果表明该方法是器件优化的有效途径。     

胶原蛋白温度效应的Raman光谱研究

在不同温度下对Ⅰ型胶原蛋白进行了拉曼光谱测定。结果表明：随温度的升高，多数谱线向低波数移动，但CH2的变形振动谱线1302cm^-1向高波数移动，苯丙氨酸的特征振动谱线1003cm^-1的波数基本保持不变。同时还给出了拉曼谱线强度随温度的变化关系，得到了0，40，68，90℃四个变性峰，其中40，68℃的峰与DSC(差示扫描量热法)和SHG(二次谐波法)的测量结果一致，0℃的峰为冰冻相变，90℃的变性峰为胶原的二级结构被破坏所致。当温度达到150℃时，谱线强度显著降低，大部分谱线消失，胶原的一级结构遭到破坏。实验还发现胶原纤维在低温区具有较好的复性特性。     

固体和熔融亚硝酸钠的Raman光谱研究

用高温共焦显微激光Raman光谱仪测定了不同温度下固体和熔融状态的亚硝酸钠的拉曼光谱图,获得了有关固体和熔态NaNO2的结构信息,分析了NaNO2熔化过程中的结构变化。     

膨胀石墨的Raman光谱研究

以波长为514.5nm的激光对550-920℃制备的膨胀石墨进行了Raman光谱研究,结果表明:膨胀石墨的Raman光谱与高取向热解石墨基本相同,分别在~1350、~1580、~2445、~2725、~3248和~4300cm-1处出现了相应的Raman位移;其中位于~1350、~2445和~4300cm-1的Raman峰位随着制备温度的不同会发生较大的移动,而不同温度制备的膨胀石墨位于~1580、~2725、~3248cm-1处的三个Ra-man峰位基本接近;~2725 cm-1处的二阶模包含两个分别位于2707和2730cm-1处的Raman峰。膨胀石墨的D模与G模强度比ID/IG随着温度升高下降,而D线的二阶模D*峰强ID*与IG的比值ID*/IG的大体变化趋势是随着温度升高而增大。     

固体和熔融碱金属碳酸盐的Raman光谱研究

用高温共焦显微激光 Raman光谱仪测定了不同温度下固体和熔融态的碳酸钠、碳酸锂以及不同成份的固态和液态 Li2 CO3- Na2 CO3混合物的 Raman光谱图 ,分析了 Na+和 Li+对碳酸根离子作用力的变化。根据 CO32 -对称伸缩振动模的波数移动情况 ,在固态混合物中也发现了混合效应     

一种挥发性熔盐显微Raman光谱研究用封闭样品池及配套热台

本文介绍了一种用于挥发性液体、特别是高温腐蚀性熔融氟化物显微Raman光谱测量用的新样品池和热台。置于氧化铝管中的铂坩埚用来盛装熔融试样。与传统的敞开式样品池不同的是, 本文提出了一种“封闭样品池”的思想, 使用石英片和高温水泥对样品池进行密封。采用铂丝加热, 最高温度可达1100℃。炉膛中部的热梯度较小。使用该装置获得了信噪比很高的光谱。     

MnF2的高压Raman光谱研究

 本文首次报道了在0~3.21 GPa压力范围内MnF₂的高压Raman光谱，结果表明压力在1.32 GPa附近，MnF₂发生了一次结构相变，晶胞中氟原子构成的八面体没有解体。在3.21 GPa下，Raman谱带消失，表明又有一次结构相变发生。     

KTP晶体的激光烧蚀特性及Raman光谱研究

高阈值的KTP晶体的研发,对高能激光领域至关重要。采用高重复频率的紫外激光对KTP进行烧蚀,并对烧蚀前后的Raman光谱进行分析,研究发现：激光等离子体效应是造成晶体破坏的主要原因,其逆韧致吸收效应会大大增加激光脉冲能量的沉积,电离效应使得晶体发生充分的离解,高压冲击波效应则把熔化、气化以及电离混合物外排的同时,使得材料发生断裂。烧蚀前后的Raman光谱的特征峰分布基本相同,说明烧蚀作用没有改变KTP材料的整体结构。但是,特征峰的对比值(RIR)都发生了改变,且有所展宽,说明烧蚀后结晶度降低。其中TiO₆和PO₄等主要氧多面体的特征峰向低波数漂移,说明材料的键合力消弱,更易发生离解。     

分子晶体的高压Raman光谱及结构相变

 本文综合我们从NH₃F（氟化胺）、HCCl₃（氯仿）、HCBr₃（溴仿）、S₈（硫）和C₃N₆H₆（三聚氰胺）等分子晶体获得的高压Raman光谱数据，讨论了分子晶体Raman光谱的谱带强度，频率位移，晶场劈裂和Grüneisen常数等对压力的依赖关系。总结了分子晶体压致结构相变的光谱证据和高压新相结构确定的几种方法。     

用于Raman光谱与微纳米结构同步检测的Raman-AFM系统研究

研究和发展了一种将微区拉曼(Raman)光谱检测与原子力显微镜(AFM)微纳米扫描成像相结合的新型Raman-AFM技术。设计了Raman光谱与AFM扫描成像的原位检测探头;研制出相应的Raman-AFM系统;利用该系统,对ZnO纳米颗粒和TiO2纳米薄膜开展了微区Raman光谱与微纳米结构的检测实验。研究表明,所获得的Raman光谱检测结果与理论值良好吻合,同时,AFM扫描检测得到的图像很好地表征了样品的微纳米结构,从而实现了微区Raman光谱与AFM图像的原位及同步检测,验证了这一技术的可行性,为Raman光谱技术与微纳米技术领域的实际应用提供了技术基础。     

Raman modes of metastable phases of Si and Ge

Abstract

We have measured Raman spectra of metastable phases of Si and Ge prepared in a diamond anvil cell for pressures up to 12 GPa. For Si we observe eight Raman lines with mode Grüneisen parameters varying between -0.3 and 1.5. These lines can be assigned to the zone-center phonons of the cubic BC8-structure (Z = 8) by assuming a violation of Raman selection rules presumably due to disorder. In the case or Ge we observe two phases with different Raman spectra. The spectrum of the first phase is strikingly similar to that of BC8-Si. Below about 5 GPa this phase transforms into a second phase, which can be identified as Ge in the hexagonal diamond structure.     

用硅离子注入方法制备的纳米硅的拉曼散射研究

在直角散射配置下测量了纳米硅样品的拉曼散射谱及其退火温度的关系。结果表明,在８００℃以下退火的样品只观察到单晶硅衬底的光学声子模,在９００℃以上退火,才观察到纳米硅的特征拉曼散射峰。在１２００℃下退火后,纳米硅的特征拉曼散射峰消失,观察到类似于非晶硅的光学声子特征峰,可能表示纳米硅不能承受这样的高温热退火。这些结果进一步证实了光致发光谱的结果。     

Temperature dependences of Raman scattering in different types of GaN epilayers

First-order Raman scatterings of hexagonal GaN layers deposited by the hydride vapour phase epitaxy and by metal-organic chemical vapour deposition on SiC and sapphire substrates are studied in a temperature range between 303 K and 503 K. The temperature dependences of two GaN Raman modes (A₁ (LO) and E₂ (high)) are obtained. We focus our attention on the temperature dependence of E₂ (high) mode and find that for different types of GaN epilayers their temperature dependences are somewhat different. We compare their differences and give them an explanation. The simplified formulas we obtained are in good accordance with experiment data. The results can be used to determine the temperature of a GaN sample.     

Coherent anti‐Stokes Raman scattering in Raman lasers and Raman wavelength converters

In this paper recent research progress on the use of Coherent Anti‐Stokes Raman Scattering (CARS) in Raman lasers and Raman wavelength converters is reviewed. The latest insights in the physical nature and behavior of CARS are addressed, and the recent performance breakthroughs in CARS‐based Raman wavelength conversion are discussed. Based on the new findings regarding the behavior of CARS, a physical explanation for apparent inconsistencies in various experimental observations of Raman wavelength conversion is provided. To conclude it is shown that these recent insights also pave the way to the development of a novel CARS‐based mechanism for reducing the heat dissipation in Raman lasers.     

Optimization of a Raman/EDFA hybrid amplifier based on dual-order stimulated Raman scattering using a single-pump

Based on dual-order stimulated Raman scattering (SRS) of a single 1395 nm Raman fiber laser in 75 km single mode fiber and its corresponding dispersion compensation module, a hybrid Raman/Erbium doped fiber amplifier (EDFA) for long wavelength band (L-band) amplification is realized by inserting a segment of EDF within the span. By comparing the performance of gain and noise in four hybrid amplifiers with different span configurations, we find that the distribution of the secondary L-band amplification obtained from the EDF along the link has a great influence on the performance of the hybrid amplifier. Both gain and noise performance of hybrid amplifier can be improved significantly by optimizing the location of the EDF. Moreover, we can extend the flat gain bandwidth from L-band to central wavelength band (C-band) plus L-band by recycling the residual first-order SRS to pump a segment of EDF with proper length.     

Theoretical and experimental investigations of coherent phonon dynamics in sapphire crystal using femto- second time-resolved coherent anti-Stokes Raman scattering

We report on the theoretical and the experimental investigations of the coherent phonon dynamics in sapphire crystal using the femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) technique. The temporal chirped white-light continuum (WLC) is used for the Stokes pulse, therefore we can perform the selective excitation of the phonon modes without using a complicated laser system. The expected quantum beat phenomenon is clearly observed. The theoretical formulas consist very well with the experimental results. The dephasing times of the excited phonon modes, the wavenumber difference, and the phase shift between the simultaneously excited modes are obtained and discussed. This work opens up a way to study directly high-frequency coherent phonon dynamics in bulk crystals on a femtosecond time scale and is especially helpful for understanding the nature of coherent phonons.     

Polarized Raman scattering and infrared spectroscopy of a natural manganocolumbite single crystal

A well‐ordered natural manganocolumbite single crystal of high quality was used as a prototype for the first determination of the polarized optical phonon modes of materials with the columbite structure. Electron microprobe and X‐ray diffraction characterizations determined the chemical formula as Mn_0.60Fe_0.40(Nb_0.80Ta_0.20)₂O₆, a cationic ordering of 81%, and the crystal structure as belonging to the Pbcn group. Polarized Raman and infrared‐reflectivity spectroscopies on oriented samples allowed us to discern 50 of the 54 predicted gerade (Raman) modes and 31 of the 38 predicted ungerade (infrared) modes for the columbite structure. The selection rules were verified, and polarization leaks only due to slight sample misorientation, confirming the high purity, ordering and quality of the material. From the polar phonon spectra, intrinsic dielectric merit factors < ε_r> = 29.2 and < Q_u × f> of 64 THz were determined, showing adequate values for designing applications in microwave circuitry. Copyright © 2009 John Wiley & Sons, Ltd.     

Stimulated Raman scattering and four-wave Raman mixing seeded by a supercontinuum generated in dibromomethane using picosecond and femtosecond laser sources

Stimulated Raman emission from liquid dibromomethane (vibrational Raman shift frequency, 588 cm⁻¹) is introduced into hydrogen gas (rotational Raman shift frequency, 587 cm⁻¹) as a seed beam, in order to generate numerous rotational lines by four-wave Raman mixing. Unexpectedly, a supercontinuum, which is generated by self-phase modulation in dibromomethane, acted as a seed beam to exclusively generate vibrational lines; the rotational lines are generated only when the supercontinuum is minimal. The former is explained by a competition between the high-gain vibrational and low-gain rotational Raman effects when strongly seeded by a supercontinuum. The latter is explained by stimulated Raman gain under the seed effect exclusively to the first-Stokes rotational line.