反斯托克斯拉曼转换增益系数的最佳化

研究了反斯托克斯拉曼转换与受激拉曼散射之间的竞争过程，讨论了反斯托克斯拉曼转换增益系数的最佳化。     

氯苯液芯光纤中的受激喇曼散射

以调QYAG激光器的倍频输出(532.1nm)为泵浦源,进行氯苯液芯光纤的受激喇曼散射实验。得到了四阶斯托克斯线和一阶反斯托克斯线,还观察到了斯托克斯谱线非对称的超展宽现象。对实验结果进行了理论探讨。     

可见光域石英光学纤维中的拉曼光谱

本文提出了石英光纤维的自然和受激拉曼散射的测试方法,给出了自然拉曼散射三级受激拉曼散射和七级斯托克斯光谱。讨论了在低于单模光纤截止波长时的输出模式。对受激拉曼光谱进一步讨论了阈值条件及半值谱宽和泵浦功率的关系。     

反共振空芯光纤中氘气受激拉曼散射实验研究

报道了基于反共振空芯光纤的氘气单程和级联受激拉曼散射实验研究,详细分析了反共振空芯光纤中氘气受激拉曼散射的过程,研究了输出光谱和拉曼谱线功率随氘气压强和泵浦激光功率的变化规律,指出降低气压、采用峰值功率相对较低的泵浦脉冲可以有效抑制转动受激拉曼散射,提高振动受激拉曼散射效率。此外,通过进一步设计、拉制传输带位置合适、带宽较窄的反共振空芯光纤,利用1064 nm脉冲激光泵浦,可以实现高效的氘气一阶振动斯托克斯光(1561 nm)和二阶级联振动斯托克斯光(2925 nm)输出。     

单频保偏掺Yb光纤放大器中的受激布里渊散射实验研究

实验研究了单频单模保偏掺Yb光纤放大器中的受激布里渊散射(SBS)效应。采用前向抽运的两级级联掺Yb光纤放大器,研究了保偏光纤放大器中的受激布里渊散射的光谱变化特性。理论计算的单模光纤的布里渊频移和SBS阈值与实验测试的结果进行了比较。在光纤放大器前后两端观察到多级次的斯托克斯(Stokes)谱线和多级的反斯托克斯(anti-Stokes)谱线,这是由级联受激布里渊散射和四波混频过程产生的。     

掺铒石英光纤中的受激拉曼散射及受激四光子混频

报道了掺铒光纤受激拉曼散射（ＳＲＳ）和受激四光子混频（ＳＦＰＭ）的实验研究。所用光纤长为１０ｍ，泵浦源为ＮｄＹＡＰ倍频５３９．７ｎｍ脉冲激光，脉冲能量为０．１Ｊ，脉宽为５０ｎｓ，获得了从５５２．１～６２２．８ｎｍ的６级受激拉曼散射谱和受激四光子混频的Ｓｔｏｋｅｓ（５４２．９ｎｍ）及反Ｓｔｏｋｅｓ（５３７ｎｍ）谱线。     

外部荧光种子植入法增强液芯光纤的受激拉曼散射

报道了一种能够增强液芯光纤中的受激拉曼散射的外部荧光种子植入法。在毛细管套液芯光纤之间充入荧光染料,实现染料介质与拉曼介质的分离,从外部植入染料荧光种子线性地放大液芯光纤中的受激拉曼散射的初始光强,有效无污染地增强了液芯光纤中拉曼介质的受激拉曼散射强度。实验结果表明,外部荧光染料浓度为最佳值约为10-6 mol/L时,可使液芯光纤中拉曼介质的各阶斯托克斯线均有最大增强。     

包层抽运掺镱光纤激光器中受激拉曼散射和受激布里渊散射效应

高功率光纤激光器大多选用掺镱双包层光纤作为增益介质,由于光纤尺寸较小,极易在光纤谐振腔中产生受激布里渊散射、受激拉曼散射效应。包层掺镱双包层光纤激光器中一旦发生受激拉曼散射和受激布里渊散射效应,其产生高强度信号成为高功率光纤激光器的主要噪声来源,影响激光输出的特性和稳定性。对包层抽运掺镱光纤激光器中的受激布里渊散射和受激拉曼散射进行了实验研究,在单模双包层光纤中观察到受激布里渊散射和受激拉曼散射。实验结果表明,在光纤谐振腔中,抽运方式、谐振腔输出镜损耗、受激瑞利散射对受激布里渊散射的影响较大,尤其是受激瑞利散射为谐振腔提供了附加反馈,不仅压窄激光信号的线宽,而且使得受激布里渊散射的阈值迅速降低。     

单频激光抽运的石英光纤宽带受激拉曼散射实验研究

采用单频高功率Nd∶YVO4 激光的倍频光 (5 32nm)作为抽运源 ,激发长度为 2 5 0m和 92 0m的单模石英光纤 ,开展了石英光纤在可见光谱范围内的受激拉曼散射实验研究 ,获得了宽带宽的、第 1级到第 4级受激拉曼散射Stokes光谱 ,拉曼频移峰值分别为 4 5 0cm- 1 ,10 6 4cm- 1 ,16 10cm- 1 和 2 16 8cm- 1 。     

GdVO4晶体的受激拉曼散射

采用熔体提拉法生长出了高质量的a轴和c轴GdVO4单晶。测量了GdVO4晶体的室温透过光谱,结果表明GdVO4晶体的短波透过截止边为338 nm,长波透过截止边大于3000 nm,透过范围覆盖紫外、可见、近红外和部分中红外波段,因此可以在较宽波长范围内实现拉曼激光频移。研究了GdVO4晶体在532 nm和355 nm皮秒激光脉冲抽运下的受激拉曼散射(SRS)。采用腔外单次通过方式,获得了3级斯托克斯线(557.98 nm,586.86 nm,618.92 nm)和1级反斯托克斯线(508.01 nm),得到GdVO4晶体一级斯托克斯拉曼散射的稳态增益系数为26.6±0.2 cm/GW,二级斯托克斯拉曼散射的稳态增益系数为14.0±0.2 cm/GW,受激拉曼散射的整体转换效率达到43%。报道了GdVO4晶体355 nm激发的受激拉曼散射,观察到2级斯托克斯谱线(365.9 nm,378.1 nm),在此条件下测得一级斯托克斯谱线的拉曼增益高达114±9 cm/GW。     

应用压缩氢的受激喇曼散射实现激光频率宽带调谐

受激喇曼散射(SRS)高功率激光频率转换的重要途径,特别是在近真空紫外波段、近红外、中红外波段更因其具有简便性和高效率而引人注目。由于固体或多数液体对光的吸收和色散,限制了入射光的强度,从而限制了输出的Stokes线及反Stokes线的强度和级数。此外,某些非线性效应较显著的液、固体分子的复杂性,增宽了输出Stokes及反Stokes线的谱线宽度;许多固体和液体的喇曼频移也比较窄,不适合用于频率转换。因此,要利用受激喇曼效应的频移来获得宽范围新波段上的可调谐激光源,往往利用气体中的SRS效应。高压H_2气是有大的     

Forced pump oscillation at anti-Stokes wavelength of coupled Raman fibre laser resonators

Multi-watt oscillation of a Yb/sup 3+/-doped silica fibre pump laser is demonstrated at two wavelengths when pump-coupled Raman fibre laser resonators are constructed using fibre end reflection and a dielectric mirror, which are common to both the pump and Raman fibre lasers. Using an off-resonant Bragg grating to force the initial oscillation of the Raman fibre laser, pump emission at the anti-Stokes wavelength is demonstrated.     

固体三倍频激光在高压H2中受激拉曼散射的实验研究

利用Nd∶YAG激光器的三倍频输出 (35 5nm)在H2 中的受激拉曼散射 (SRS)获得波长在 2 0 4～ 86 7nm范围内的激光输出。当抽运能量为 70mJ时观察到四阶Stokes光和五阶Anti Stokes光 ,其中第一阶Stokes光 (416nm)输出能量为 2 8 7mJ,第二阶Stokes光 (5 0 3nm)输出能量为 16mJ,一阶Anti Stokes光 (30 9nm)输出能量为 3mJ。研究了H2 压力和各阶Stokes光能量的关系 ,同时观察到环行光斑和脉宽压缩现象。     

四倍频Nd：YAG激光在高压氢气中的喇曼频移研究

利用Nd:YAG固体激光器四倍频输出(266nm)在高压H₂中的受激喇曼散射获得多波长的激光输出。当泵浦能量一定时,通过改变H₂压力得到了最佳的能量输出,299nm波长的激光能量为3mJ,341nm波长的激光能量输出为6.1mJ,398nm波长的激光能量输出为2.8mJ,239nm波长的激光能量输出为0.8mJ,同时在477nm,595nm,218nm,200nm波段也有能量输出。     

Time behavior of stimulated Raman scattering

The time relationship between the 1st Stokes, 2nd Stokes, 3rd Stokes, 1st anti-Stokes radiations, and the exciting laser radiation for stimulated Raman scattering in self-focusing liquids has been investigated theoretically and experimentally. A model is presented for calculating the output power and time behavior of the different orders of Stokes radiation when self-focusing occurs. Experimentally, good agreement is found between predicted and measured output powers, but some apparent anomalies are observed in the time behavior for the 2nd and 3rd Stokes radiations and 1st anti-Stokes radiation, especially in carbon disulfide. There are strong indications of dielectric breakdown occurring in the liquids, and it is shown qualitatively that the observed time behavior of the higher order Stokes radiation can be caused by the dielectric breakdown.     

Fibre-optic Solc filter for use in Raman amplification of light

Fibre-optic Solc filters, in which five consecutive fibre coils are tilted with respect to each other, have been fabricated. The wavelength of maximum transmittance is designed to coincide with 1.24 ?m wavelength, and the half-power bandwidth is 61 nm. To show the feasibility of the fibre-optic Solc filter in Raman amplification of light, the third Stokes line (?=1.24 ?m) of 1.06 ?m Nd:YAG laser light from a silica fibre was successfully extracted, while the pump light and other Stokes lines were suppressed below ?13 dB.     

Dopant effect on transmission loss increase due to hydrogen permeation

The transmission loss increase due to hydrogen permeation in a GeO2-doped silica fibre and a P2O5-doped silica fibre are investigated. As a result, the difference of the loss increase between them is observed, and is considered to be due to the difference of the electronegativity between silica, germanium and phosphorus.     

Low-loss high-numerical-aperture optical fibre fabricated by v.a.d. method

Low-loss high-numerical-aperture optical fibres, consisting of GeO2/P2O5-doped silica core and silica cladding, have been made by the v.a.d. method. The minimum transmission loss of the fibre with an n.a. 0.32 was 0.8 dB/km at 1.55 ?m.     

Low-Loss single-mode fibre at the material-dispersion-free wavelength of 1.27 ?m

A GeO2-doped silica single-mode optical fibre with a low attenuation loss of 0.5 dB/km at 1.27 ?m, where the material dispersion of the silica glass falls to zero, has been made by a C.V.D. technique. Attention was paid to reducing OH absorption losses in the single-mode fibre.     

Chemical change from diffused hydrogen gas to hydroxyl ion in silica glass optical fibres

The chemical change from hydrogen gas that diffuses into silica glass for optical fibres to hydroxyl function has been investigated. Hydrogen molecules that diffuse into GeO2-doped silica glass at 500°C easily change into OH ions by thermal energy, while this chemical change does not occur in pure silica glass at 500°C. Also, germanium-doped silica fibre, in which hydrogen gas is dissolved at room temperature, shows OH ion absorption loss increase with chemical change by heat treatment at above 100°C, while pure silica core fibre shows no OH ion absorption loss increase by the same treatment.