基于外腔增强泵浦的窄线宽连续高效拉曼激光器

Raman laser technique is an important nonlinear conversion method, which always is used to emit new wavelength lasers. Since the low gain factor of the Raman crystal, it is hard to generate continuous wave Raman laser. In this research, external cavity pumping enhancement technique is applied to enhance the pump power in Raman crystal so that it could emit continuous wave Raman laser. In order to improve the pump conversion efficiency, in this research, a theoretical model of the external cavity enhanced pump cw Raman laser is built based on the the solution of coupled-wave equations and theory of cavity enhancement. In the experiment, the pump laser and the external Raman cavity are resonant based on PDH method, and insert a sum frequency mixing crystal to improve the unidirectional resonating of the Raman laser, and arise the power stability of the output power. Moreover, in this investigation, a theoretical model of the impact of the thermal effects induced by high power laser to the Raman laser is work out, and the method of compensation is proposed. In the experiment, a cw Raman laser is construced with output power of 5W, power stability better than ±5%/h, and line-width smaller than 20MHz.

拉曼激光技术是一种重要的非线性频率变换方式，常用于产生新型波长激光。由于拉曼晶体增益系数小，因此很难实现连续拉曼激光。本研究使用外腔增强泵浦技术提高拉曼晶体内泵浦功率，实现连续拉曼激光输出。为了提高装置中泵浦光转换效率，在本研究中基于耦合波方程的解和外腔增强理论，建立外腔增强泵浦的连续拉曼激光器理论模型。实验上使用PDH方法实现外腔和泵浦激光的共振，并在腔内插入和频晶体实现单向拉曼激光振荡，提高拉曼激光的稳定性。另外，本研究中建立激光诱导产生拉曼晶体热效应对该系统中拉曼激光输出功率影响的理论模型，并提出补偿方案。最终在实验上实现输出功率5W连续拉曼激光，功率稳定性小于±5%/h，线宽小于20MHz。

本文中设计了光学参量振荡、受激拉曼与和频三种光学频率变换的实验装置并进行了理论与实验研究，实现了高功率、高效率、高能量的激光输出。本文研究内容主要包括：.1. 基于准相位匹配晶体的外腔连续光学参量振荡器研究。通过优化泵浦光的聚焦参数和信号光在谐振腔内的光斑大小，实现了4.4W的窄线宽中红外激光输出。通过实现信号光与参考腔的频率锁定，实现了信号光的线宽压窄。另外设计了基于泵浦增强的光学参量振荡器，并对其瞬态特性进行了研究。.2. 研究基于外腔泵浦增强拉曼激光器。通过设计腔内斯托克光的本征模体积，以降低阈值。实验中以钨酸钡晶体为三阶非线性晶体，1064nm连续激光泵浦，产生1180nm拉曼激光，提出了优化实验装置的方案。.3. 研究基于双波长外腔共振和频的理论模型与实验。对高效转换和频的情况进行数值求解，结合外腔增强理论，得到了双波长外腔共振和频的理论模型。实验上实现了637mW的红光输出，信号光的转换效率达到了93%。观测到了和频光的强度噪声自抑制效应，基于双波长外腔共振和频理论可以解释该现象。