GaSe晶体的双光子吸收对太赫兹输出的影响  

Two-photon Absorption Attenuated THz Generation in GaSe

作　　者：姜可[1,2] 谢冀江[1] 杨贵龙[1] 谢京江[1] 李殿军[1] 陈飞[1] 

机构地区：[1]中国科学院长春光学精密机械与物理研究所激光与物质相互作用国家重点实验室,吉林长春130033 [2]中国科学院大学,北京100049

出　　处：《发光学报》2015年第3期361-365,共5页Chinese Journal of Luminescence

基　　金：激光与物质相互作用国家重点实验室开放基础研究课题(SKLLIM1012)资助项目

摘　　要：根据光整流效应,利用超快激光脉冲泵浦GaSe晶体实现了0.2-2.5 THz的宽带太赫兹辐射输出。禁带中的电子在两个800 nm光子的作用下激发到导带中形成自由载流子,进而吸收所产生的太赫兹辐射,最终导致太赫兹的输出随泵浦功率的增加而趋于饱和。为了研究双光子吸收对太赫兹输出的影响,测量了800nm处的GaSe晶体的双光子吸收系数,结果为0.165 cm/GW。通过对太赫兹输出实验数据的拟合,得到GaSe晶体中自由载流子对太赫兹输出的吸收截面为1×10^-15cm^2。本文的研究结果可用于优化GaSe晶体在强激光泵浦下的太赫兹转换效率。The broadband THz generation from 0 . 2 to 2 . 5 THz was measured as a function of pump intensity in a single pure gallium selenide crystal based on the optical rectification of ultrafast laser pulses. Two-photon absorption at 800 nm can generate free charge carriers which can absorb the generated THz radiation, and finally attenuate THz output. The result indicates that the pump inten-sity dependence of ouput THz radiation changes from square to sub-linear relationship and the satu-ration of output THz radiation appears at high pump intensity. To study the impact of two photon ab-sorption on THz generation, the two photon absorption coefficient of GaSe at 800 nm is measured to be 0. 165 cm/GW, which is determined by the measured nonlinear transmission. The THz output fitting result taking account of the free charge carrier absorption cross section of 1 × 10^ -15 cm^2 is con-sistent with the experiment data very well. This estimation result can be used to optimize the conversion efficient of THz generation in GaSe crystal under intense laser pump.

关 键 词：GaSe晶体 双光子吸收 太赫兹 吸收截面 

分 类 号：O437[机械工程—光学工程] TN248[理学—光学]