基于双温耦合模型的太赫兹晶体损伤阈值分析  

Analysis on damage threshold of terahertz crystals based on twotemperature coupling model

作　　者：于军立 孟庆龙[1] 叶荣[2] 钟哲强[1] 张彬[1] 

机构地区：[1]四川大学电子信息学院,四川成都610065 [2]成都师范学院物理与工程技术学院,四川成都611130

出　　处：《光电子．激光》2015年第7期1417-1422,共6页Journal of Optoelectronics·Laser

基　　金：中国工程物理研究院太赫兹科学技术基金(CAEPTHZ201305);四川省教育厅创新团队计划(13Td0048)资助项目

摘　　要：飞秒激光通过非线性光学整流效应产生太赫兹(THz)波时,THz波转换效率会随着飞秒激光功率的增大而明显提高。然而,飞秒激光功率过高会造成非线性晶体损伤,进而影响THz波的产生及输出,因而对飞秒激光作用下非线性晶体的损伤阈值进行研究具有重要意义。本文在经典的双温模型基础上,引入电子激发、载流子吸收等电离过程的影响,建立了飞秒激光作用下非线性THz晶体损伤阈值的预估模型。采用有限差分法,数值模拟了飞秒激光辐照下THz晶体的温度场变化,并据此对晶体损伤阈值进行预估。在此基础上,分析比较了LiNbO3、ZnTe和ZnSe 3种THz晶体的损伤阈值随激光脉宽的变化规律。结果表明,晶体的禁带宽度和比热容越大,晶体的损伤阈值就越大;LiNbO3晶体因其具有更高的损伤阈值,在产生高功率THz波方面具有更大的优势。The conversion efficiency of terahertz（THz）wave generated in nonlinear optical rectification is obviously improved with the increase of femtosecond laser power.However,the nonlinear crystals tend to be damaged under high-power femtosecond lasers,which seriously affects the generation and output of THz wave.Therefore,it is of great significance to study the damage threshold of nonlinear crystals irradiated by femtosecond lasers.In this paper,based on the classic two-temperature coupling model,the influence of ionization process,including electronic excitation and carrier absorption,has been taken into account,and the prediction model of damage threshold of nonlinear terahertz crystals under femtosecond lasers has been further built up.The variation of the temperature field of terahertz crystals irradiated by femtosecond lasers has been numerically simulated by the finite-difference method,and the damage threshold of terahertz crystals has been estimated.On the basis,the variations of damage thresholds of LiNbO3,ZnTe and ZnSe crystals with the pulse width of femtosecond lasers have been analyzed and compared.The results show that the forbidden band width and specific heat capacity of the crystal significantly affect the damage threshold.In addition,the damage threshold is higher for nonlinear terahertz crystals with larger forbidden band width and heat capacity.Consequently,LiNbO3 crystal is superior in generating high-power THz wave due to its higher damage threshold.

关 键 词：飞秒激光 非线性晶体 双温模型 损伤阈值 

分 类 号：O437[机械工程—光学工程]