非线性晶体走离效应下的二倍频效率研究  

SHG efficiency of nonlinear crystal walk-off effect

作　　者：高锋 蔡云鹏 白振旭 齐瑶瑶 颜秉政 王雨雷 吕志伟 丁洁 Gao Feng;Cai Yunpeng;Bai Zhenxu;Qi Yaoyao;Yan Bingzheng;Wang Yulei;Lv Zhiwei;Ding Jie(Center for Advanced Laser Technology,Hebei University of Technology,Tianjin 300401,China;Hebei Key Laboratory of Advanced Laser Technology and Equipment,Tianjin 300401,China)

机构地区：[1]河北工业大学先进激光技术研究中心,天津300401 [2]河北省先进激光技术与装备重点实验室,天津300401

出　　处：《红外与激光工程》2023年第8期225-234,共10页Infrared and Laser Engineering

基　　金：国家自然科学基金项目(62005075);河北省科技研究项目(QN2020182);河北省自然科学基金项目(F2020202029)。

摘　　要：应用非线性频率变换技术的短波固体激光器在先进研究、生物医疗和工业生产等领域广泛应用,而走离效应是影响非线性变换效率的关键因素。为了实现更高效率的二倍频转换,各种减小走离效应的结构优化方案被提出,多种二倍频效率模型被建立,但是这些模型在普适性和影响因素全面性上还有所欠缺。文中在理想二倍频效率模型的基础上,提出一种非线性晶体走离效应下的二倍频效率模型,对于空间走离过程进行了更为充分的研究,将二倍频过程的多种因素都进行了细化分析。该模型有两个优势:一方面可以从多种参数的角度更精确地对平行传输光束与聚焦光束的二倍频效率分别进行预测;另一方面可以实现最佳二倍频晶体种类和最佳二倍频晶体长度的选择。Objective Visible and ultraviolet laser output can be realized by solid-state lasers using second-harmonic generation(SHG)technology,which have a wide range of applications in many fields,including atmospheric exploration,biomedicine and industrial processing.The spatial walk-off effect that occurs inside the crystal in the SHG process can cause the spatial phase mismatch between the fundamental laser and the frequency-doubling laser,which lead to obvious loss of SHG efficiency restricting the SHG conversion efficiency.In order to further optimize the frequency doubling efficiency,the SHG theoretical model combined with influencing factors including the spatial walk-off effect needs to be improved.Therefore,combined with the spatial walk-off effect and SHG laser analysis,a hybrid model is proposed to study the parameters in the conversion process of the internal walk-off effect of nonlinear crystals.In this model,the influence of various parameters such as SHG crystal length,laser power density,SHG crystal type,laser wavelength on the SHG efficiency are carefully analyzed,which is of great significance for the optimization of SHG structure and the improvement of conversion efficiency.Methods Based on the ideal SHG conversion efficiency model,this study discussed the energy conversion and beam separation in the process of space walk-off effect,and establishes the SHG conversion efficiency model of two different pump structures,including focused beam and parallel transmission beam(Fig.1-2).The specific effects of various parameter changes of SHG crystals and fundamental laser have been discussed.ResultsandDiscussions According to the established frequency-doubling efficiency model,the influence of the departure effect on the frequency-doubling efficiency has been discussed(Fig.3).The frequency-doubling efficiency was analyzed by using the fundamental frequency optical parameters of fundamental frequency light,including beam quality,beam radius,focal length of focusing lens,beam waist size and divergence angle(Fig.4

关 键 词：非线性频率变换 走离效应 二倍频晶体 二倍频效率 

分 类 号：TN241[电子电信—物理电子学]