基于腔内泵浦技术的蓝光泵浦Pr:KYF预调Q倍频紫外单频激光器机理研究

The ultraviolet single frequency laser has been widely applied in the filed of high density optical storage, lithography, material processing and so on. For the first time, this project prefers to combine pre-Q-switching technique with Pr:KYF laser crystal's emission line at orange band, and the 482.5nm blue laser is used as a new type of pumping source of Pr:KYF crystal, and directly obtain the output of ultraviolet single frequency laser by once nonlinear frequency doubling technique. The research contents of this project to be carried out are as following:. First, the theoretical model of 482.5nm blue laser which basing on the technology of intra-cavity pumping is established, the key parameters are optimized and solved, and after these;. Second, the relationship between the running time, the cavity loss during the quasi-steady state operation and the different longitudinal mode gain of the Pr:KYF laser is cleared, the optimal conditions to realize single frequency laser operation are obtained;. Third, the temperature rising model of Pr:KYF laser crystal under the condition of cross pumping is constructed, and the structural parameters are solved;. Last, the eigenstates are studied by using the Jones matrix, the conditions of realizing ultraviolet single frequency laser output are optimized, and the experiment are carried out .. For this project, the aim is to reveal the operation mechanism of single frequency laser pumped by blue laser, the technical approach is proposed to realize the best ultraviolet single frequency laser output, and this is of great significance to research on the high average power of single frequency ultraviolet laser.

紫外单频激光在高密度光学存储、光刻及材料处理方面具有广阔的应用前景。本项目首次提出将激光预调Q技术与Pr:KYF晶体在橙黄波段的发射光谱特性相结合，并采用482.5nm蓝光作为Pr:KYF晶体的新型泵浦源，通过倍频技术直接获得紫外单频激光输出。拟开展的研究内容如下：.（1）建立基于腔内泵浦技术的482.5nm蓝光激光器的理论模型，优化求解关键参数；.（2）明确准稳态运转时的运行时间、腔内损耗与Pr:KYF激光器各纵模增益之间的关系，获得实现单频激光运转的最佳条件；.（3）建立交叉泵浦条件下的Pr:KYF晶体温升模型并求解结构参数；.（4）利用Jones矩阵研究本征态问题，优化求解实现紫外单频激光输出的最佳条件并开展实验研究。.本项目旨在揭示蓝光泵浦Pr:KYF预调Q紫外单频激光的运转机理，给出实现紫外单频激光最佳输出的技术途径。这将对研究高平均功率紫外单频激光器具有十分重要意义。

单频紫外激光具有极高的光谱响应度和信噪比，在精密测量、激光全息、激光显示等领域有着广泛的应用。而目前获得单频紫外激光的常用手段是通过对Nd:YAG或Nd:YVO4等激光器输出的近红外波段进行多次倍频，系统光-光转换效率较低。通过预调Q技术与Pr:KYF倍频激光器进行结合是获得高效率单频紫外激光的有效途径。本研究主要研究内容以预调Q理论为切入点，分析了预调Q倍频Pr:KYF激光器的内部工作原理及不同参数对激光器输出特性的影响。同时，以预调Q技术、腔内泵浦技术和倍频组合技术实现单频脉冲激光输出。.具体取得重要研究结果，在理论研究方面，通过对四能级速率方程组引入阶跃函数，建立了用来描述预调Q行为的数学模型，并对预调Q激光器的粒子数演化过程开展了仿真研究，获得了反转粒子数及光子数随时间的演化规律；在此基础上，引入多模竞争理论对预调Q技术中的模式演化过程进行仿真，获得了Pr:KYF预调Q过程中的模式演化规律；同时，通过拉格朗日乘子法对预调Q技术的速率方程进行求解，推导出其解析表达式，结合能量转化模型建立了含阶跃损耗、准稳态运行时间的超越方程，获得了不同参数下(腔长、单频调制深度)预调Q激光器的输出特性。.在实验研究方面，首先开展了Pr离子激光器的激光实验研究，谐振腔采用平凹腔结构，获得红光最大输出功率为1W，光学效率为53%。应用以上谐振腔结构，进行了Pr离子激光器的脉冲激光实验，获得10kHz重频红光脉冲激光，激光阈值为0.56A，单脉冲能量为4.5μJ，脉冲宽度为93.7ns，输出功率为45mW。对不同重频下的实验结果进行分析发现，在重频10kHz时，激光器存在“增益不足”的现象。在此基础上，开展了预调Q实验研究。预调Q实验中，泵浦电流为0.72A时，获得重频为10kHz单频脉冲激光，单脉冲能量为30nJ，脉冲宽度为230.5ns。