和频、差频共存的太赫兹波上转换探测理论分析  

Theoretical Analysis of Terahertz-Wave Frequency Up-Conversion Detection Based on Coexisting Difference-and Sum-Frequency Generation

作　　者：尹晓琴[1] 范书振[1,2] 李永富 张行愚[1,3] 刘兆军 赵显[1,2] 方家熊[1,2,4] Yin Xiaoqin;Fan Shuzhen;Li Yongfu;Zhang Xingyu;Liu Zhaojun;Zhao Xian;Fang Jiaxiong(Key Laboratory of Laser&Infrared System(Shandong University),Ministry of Education,Qingdao,Shandong 266237,China;Center for Optics Research and Engineering(CORE),Shandong University,Qingdao,Shandong 266237,China;School of Information Science and Engineering,Shandong University,Qingdao,Shandong 266237,China;Shanghai Institute of Technical Physics,Chinese Academy of Sciences,Shanghai 200083,China)

机构地区：[1]山东大学激光与红外系统集成技术教育部重点实验室,山东青岛266237 [2]山东大学光学高等研究中心,山东青岛266237 [3]山东大学信息科学与工程学院,山东青岛266237 [4]中国科学院上海技术物理研究所,上海200083

出　　处：《中国激光》2021年第12期371-377,共7页Chinese Journal of Lasers

基　　金：国家自然科学基金(61775122,12074222);山东省自然科学基金面上项目(ZR2017MF038)。

摘　　要：基于非线性频率上转换的太赫兹波探测技术具有灵敏度高、响应速度快、可室温操作等优点,现有理论研究中仅考虑了差频转换或和频转换,而这与实验中观察到的二者共存的物理现实并不一致。本文提出了在非线性频率转换过程中差频与和频共存时的理论方程,并以DAST晶体为例模拟分析了不同晶体厚度及泵浦强度下的太赫兹波探测情况。理论计算表明:和频、差频共存下各波变化趋势与单差频或单和频情况有所不同;和频过程的存在会降低差频过程的效率,若只考虑差频,则结果将有所偏差。在特定实验条件下,同时利用差频光与和频光,总信号输出强度更大,其探测效率高于单差频的情况;存在一个最佳的晶体厚度,使得总信号输出最强。进一步计算表明,基于非线性频率上转换的太赫兹单光子探测有可能实现。Objective Terahertz technology is developing rapidly and is widely used in various basic scientific research and application fields such as biology,industrial nondestructive evaluation,environment monitoring,and security.Among the various applications,high-sensitivity detection of terahertz waves has attracted considerable attention.Terahertz-wave detection technology based on nonlinear frequency up-conversion is a promising technique owing to its decent performance in terms of high sensitivity,fast response,and room-temperature operation.Based on the second-order nonlinear effect in crystals,a new near-infrared(NIR)signal light is obtained via the interaction of NIR pumping laser and terahertz wave.High-sensitivity detection of terahertz waves can be achieved with the assistance of signal light detection using mature NIR detection technology.In experiments,difference-frequency generation(DFG)and sum-frequency generation(SFG)exist together.In previous studies,only DFG or SFG process was considered,both of which possess some limitations.Therefore,the coexistence of DFG and SFG demands prompt investigation.In this study,theoretical nonlinear frequency conversion equations that contain both DFG and SFG are proposed.The detailed situations of terahertz-wave detection based on DAST crystals were simulated and analyzed under different setting conditions.Such a theoretical study of terahertz wave detection under the coexistence of DFG and SFG will be helpful in future experiments.Methods In this study,four-wave interaction equations considering the coexistence of DFG and SFG are proposed,derived from the improvement and further deduction of classical three-wave coupling equations.Considering the nonlinear organic crystal DAST as an example,a series of simulations and analyses were performed based on the four-wave interaction equations using MATLAB software and conclusions were drawn.To illustrate lightwave conversion in different nonlinear processes,an ideal case of ignoring the light absorption and phase mismatching wa

关 键 词：非线性光学 上转换 差频与和频共存 太赫兹波探测 单光子探测 

分 类 号：O441.4[理学—电磁学]