【作者】 薛峤；

【导师】 张行愚；

【作者基本信息】 山东大学 ， 光学工程， 2010， 硕士

【摘要】 受激拉曼散射是一种非常有效的频率变换方法,转换后的拉曼激光波长由泵浦基频光的波长和具体的拉曼介质决定。物质的三种状态固体、液体、气体都包括丰富的拉曼介质。受激拉曼散射光的光谱可遍及紫外到近红外,大大拓宽了激光光谱范围。此外受激拉曼散射具有多种优良特性,如拉曼散射光光束质量好、脉冲宽度窄、转化效率高,并且区别于其他非线性效应的是,受激拉曼散射不需要相位匹配。因此,对于拉曼介质的研究自从上世纪60年代发现受激拉曼散射以来从未间断,拉曼介质对于拉曼激光脉冲的放大特性是拉曼介质最重要的特性之一。因此,研究各种各样的拉曼介质对于拉曼激光脉冲的放大特性是一项非常重要的工作。本论文以YVO4晶体作为拉曼转换晶体,通过YVO4晶体对皮秒拉曼激光脉冲及纳秒拉曼激光脉冲的放大实验,测试了拉曼晶体对拉曼激光脉冲的放大特性,并测得了YVO4晶体的拉曼增益系数。以下为本论文的具体研究内容。在皮秒锁模脉冲泵浦激励下,观测YVO4晶体对于皮秒拉曼激光脉冲的放大特性,并根据两块长度不同YVO4晶体对于皮秒拉曼激光脉冲的放大差异得到YVO4晶体的拉曼增益系数。首次实现了根据两块长度不同YVO4晶体对于皮秒拉曼激光脉冲的放大实验得到YVO4晶体的拉曼增益系数。系统地研究了以a切Nd:YVO4晶体作为拉曼介质的端面泵浦主动调Q自拉曼激光器的特性,Nd:YVO4晶体既是激光晶体同时又是拉曼晶体,使用不同透过率的输出镜,在不同的脉冲重复率下,得到不同能量比例状态的基频光和拉曼光,为测试YVO4晶体对于纳秒拉曼激光脉冲的放大特性做充分的准备。实验中选取30 kHz调Q频率并使用特定输出耦合镜(对基频光和拉曼光反射率分别为97.6%和93.7%)时的输出脉冲光来做纳秒拉曼激光脉冲的放大实验。系统地研究了以Nd:YAG作为激光晶体、以a切YVO4晶体作为拉曼介质的端面泵浦主动调Q内腔式拉曼激光器的特性,使用不同透过率的输出镜,在不同的脉冲重复率下,得到不同能量比例状态的基频光和拉曼光。实验中选取20 kHz调Q频率并使用特定输出耦合镜(对基频光和拉曼光反射率分别为97.6%和93.7%)时的输出脉冲光来做纳秒拉曼激光脉冲的放大实验。更多还原

【Abstract】 Stimulated Raman scattering (SRS) is a fairly effective way to shift the frequency of laser. The frequencies of Raman lasers are determined by both the pump laser frequencies and the Raman materials. There are many kinds of Raman materials in all three states of materials, solid, liuquid, and gas. The spectrum of Raman laser ranges from ultraviolet to near-infrared. Besides, stimulated Raman scattering has plenty of excellent characteristics, such as good quality of scattering light, narrow pulse width, high convertion efficiency, without requiring phase matching. So, researches in Raman materials are always on the frontier of science as early as 60’s in the last century. The characteristics of Raman amplifier are one of the most important aspects of Raman materials. It is a quite important job to conduct researches on Raman amplifiers.In this thesis I use YVO4 as the Raman material, studing its amplifying characteristics for Raman laser pulses and measuring its Raman gain coefficient, based on experiments in amplifying nanosecond Raman laser pulses and picosecond Raman laser pulses. The specific contents are stated as following.The Raman gain coefficient is calculated by comparing the outputs of two YVO4 crystals in different lengths under the pump of picosecond mode-locked pulses. This is the first time to obtain the Raman gain coefficient by this method to our knowledge.Both the fundamental laser and Raman laser are obtained from an end-pumped actively Q-switched self-Raman laser, using an a-cut Nd:YVO4 crystal as the laser crystal and Raman crystal. By changing the Q-switched pulse frequency and the transmission of output mirror, different output powers at the fundamental laser and Raman laser are obtained. The experiments of amplifying nanosecond Raman laser pulse are conducted under the condition that the output mirror reflectivity is 97.6% for fundamental wavelength and 93.7% for Raman wavelength and the Q-switched pulse frequency is 30 kHz.Both the fundamental laser and Raman laser are obtained from an end-pumped actively Q-switched intracavity Raman laser, using an Nd:YAG crystal as the laser crystal and an a-cut YVO4 crystal as the Raman crystal. Through changing the Q-switched pulse frequency and the transmission of output mirror, different output powers at the fundamental laser and Raman laser are obtained. In specific experiments for obtaining appropriate pulses in amplifying nanosecond Raman laser, I use output mirror whose reflectivity is 97.6%for the fundamental wavelength and 93.7%for the Raman wavelength and choose Q-switched pulse frequency of 20 kHz.更多还原