基于综合泵浦的全固态激光器可控热管理理论和应用研究

Thermal effect has become the main drawback which hinders the efficient operation of all-solid-state lasers with high power and good beam quality. The thermal management is therefore very important for improving the performance of all-solid-state lasers. In this application, we intend to research on theory and application of controllable thermal management based on integrated pumping for all-solid-state lasers. In-band pumping is considered as a promising technology for its low quantum defect and heat generation but still suffers the problem of low pump absorption and therefore the optical efficiency is unsatisfying. On the contrary, the traditional pumping is well absorbed thus can achieve high optical efficiency but the thermal effects are much more serious. By pumping the laser gain medium with in-band and traditional pump source simultaneously, which is defined as integrated pumping, we could combine the advantages of two pumping schemes and meanwhile overcome the shortcomings of them. If the power proportions of the two kinds of pump are adjusted as needed; the highest optical efficiency allowed can be achieved with the thermal load controlled under the restriction. The active, controllable thermal management is then realized. The general solution of the optimal pump power proportion under different restrictions will be found out to establish the theoretical model of the controllable heat management technology. The experimental research of integrated pumped high power end-pumped Nd:YVO4 laser and side-pumped Nd:YAG laser system will be carried out to investigate the application of the controllable thermal management theory. Treat heat as a key performance indicator as well as output power and conversion efficiency when evaluating the system. The optimal power proportion under different restrictions can be determined and thus the theoretical model of the controllable heat management technology can be verified. The research can provide adequate scientific basis and technical preparations for the development of high-power integrated pumped all-solid-state lasers with controllable thermal management.

热效应是全固态激光器高功率、高效率、高光束质量运转的主要瓶颈，热管理技术直接关系激光器性能的优劣。本申请拟研究基于综合泵浦的全固态激光器可控热管理理论和应用：利用同带泵浦光和传统泵浦光同时对工作介质进行综合泵浦，根据需要调节两波长泵浦光功率配比，充分发挥同带泵浦量子缺陷率低、热负载小和传统泵浦吸收好、光光效率高的优点，克服同带泵浦吸收差、光光效率低和传统泵浦热效应严重的缺点，可在将热控制在允许范围内的同时实现激光器的高光光效率运转，实现主动的、可控的热管理。计算不同限制条件下综合泵浦最优配比的通解，建立可控热管理技术的理论模型；将热作为一个主要因素，与输出功率、转换效率综合考虑对系统进行评价；开展可控热管理技术在端泵Nd:YVO4和侧泵Nd:YAG高功率激光系统中的应用研究，找出泵浦最优配比，验证综合泵浦可控热管理理论，为发展高功率综合泵浦可控热管理激光器提供充分的科学依据和技术准备。

热效应是固体激光器性能的最主要限制因素。掺Nd激光增益介质的传统泵浦方式和同带泵浦方式由于泵浦吸收系数和量子亏损等方面的差异，分别具有高热高效和低热低效的特性。为解决上述问题，我们在研究同带泵浦方式吸收和激光效率特性的基础上，利用传统泵浦光和同带泵浦光同时泵浦激光晶体，通过调节两个波长的泵浦光的功率配比，对激光器功率和热负载进行主动调控，以实现具体应用条件下的最优输出特性，具体如下：1）为最大限度地降低热负载，采用914nm Nd:YVO4激光器和914nm锁波长LD为泵浦源进行主动调Q Nd:YVO4自拉曼激光器和锁模Nd:YVO4激光器的实验研究。自拉曼激光器在15.7W入射泵浦功率下获得2.58W 1525nm斯托克斯光输出，光光效率16.4%，锁模激光器在20W入射泵浦功率下获得6.5W 1064nm激光输出，通过器件参数和合理优化实现了与传统泵浦方式相比拟的转换效率，验证了914nm基态斯塔克能级同带泵浦方式的可行性。2）基于速率方程理论分析不同泵浦波长和器件参数对激光器效率和热负载的影响，建立双波长综合泵浦方式的理论模型，分析其适用范围和优化条件。在此基础上分别利用808/880nm端泵Nd:YVO4激光器和808/885nm侧泵Nd:YAG激光器开展双波长综合泵浦方式的实验研究，实验验证了通过改变双波长泵浦光功率配比对激光器的输出功率和热负载进行主动调控，实现具体应用条件下的最优输出特性的设想。端泵Nd:YVO4激光器1064nm和1342nm激光输出功率分别为61.2W和22.7W，光光效率分别为49.0%和23.4%；侧泵Nd:YAG激光器1064nm激光最高输出功率267W。利用885nm同带泵浦Nd:YAG-YVO4内腔拉曼激光器结构获得16.7W 1176nm一阶斯托克斯光输出和10.6W 588nm黄光输出。