强太赫兹脉冲产生及硒化镓晶体非线性效应研究  

Intense Terahertz Pulse Generation and Nonlinear Effect of GaSe Crystal

作　　者：索鹏 王晨 李高芳 孙凯文 张文杰 林贤[1] 黄志明[3] 马国宏[1] Suo Peng;Wang Chen;Li Gaofang;Sun Kaiwen;Zhang Wenjie;Lin Xian;Huang Zhiming;Ma Guohong(Department of Physics,Shanghai University,Shanghai 200444,China;School of Electronic&Information Engineering,Shanghai University of Electric Power,Shanghai 200090,China;State Key Laboratory of Infrared Physics,Shanghai Institute of Technical Physics,Chinese Academy of Sciences,Shanghai 200083,China)

机构地区：[1]上海大学物理系,上海200444 [2]上海电力大学电子与信息工程学院,上海200090 [3]中国科学院上海技术物理研究所红外物理国家重点实验室,上海200083

出　　处：《中国激光》2023年第17期208-214,共7页Chinese Journal of Lasers

基　　金：国家自然科学基金(92150101)。

摘　　要：为探索单周期或亚周期的强场太赫兹脉冲抽运下各种材料的非线性光学响应,基于铌酸锂(LiNbO3)晶体,采用飞秒脉冲倾斜波前技术,获得了单脉冲能量为2.6μJ、峰值场强为632 kV/cm的强太赫兹脉冲输出,并在该辐射源的基础上搭建了太赫兹抽运-光探测系统。利用该系统研究了硒化镓(GaSe)晶体的非线性光学响应,观测到亚周期的太赫兹脉冲诱导的光学双折射,其引起的相位变化与普克尔斯效应和克尔效应相关。研究结果为强场太赫兹抽运下介质的非线性效应分析提供了思路,为材料的电光系数和非线性折射率系数的测定提供了借鉴。Objective The study of high-order nonlinear behavior,prompted by single-cycle or subcycle strong terahertz pulses,has been scarce,primarily due to the limitations of highly stable and high-intensity terahertz radiation sources.The strong terahertz field–matter interaction leads to new avenues for exploring and understanding various novel nonlinear phenomena.The employment of a femtosecond laser to pump a lithium niobate(LiNbO3)crystal has been considered as a major strategy for generating strong terahertz radiation.The strong terahertz pulse acquired by this technique can coherently detect and manipulate the optical properties of materials on an ultrafast timescale and can play a crucial role in discovering new phenomena and revealing new mechanisms.In this study,to explore the nonlinear effects of materials under strong terahertz pulse irradiation,a strong terahertz pump-optical probe spectroscopy system is developed by utilizing the tilted wavefront technique based on a lithium niobate crystal.Specifically,the highest terahertz output energy of 2.6μJ and a focused terahertz peak electric field strength of 632 kV/cm are realized.Meanwhile,the nonlinear crystal gallium selenide(GaSe)is examined with this system,and we demonstrate that the strong change in the terahertz pulse-induced refractive index of GaSe is due to Pockels and Kerr effects.Methods A strong terahertz pump-optical probe spectroscopy system is established(Fig.1).This system operates on a Ti∶sapphire laser amplifier that can deliver laser pulses with a single-pulse energy of 2 mJ,a pulse duration of 120 fs,and a repetition rate of 1 kHz.A small portion of the femtosecond laser is divided by a beam splitter to sample the birefringence signal of the material induced by the terahertz pulse,whereas the residual 90%of the laser energy is used to pump the lithium niobate crystal to generate a strong terahertz pulse.A diffraction grating of 1800 line/mm is used to tilt the wavefront of the pump laser.A half-wave plate behind the grating changes the p

关 键 词：材料 铌酸锂晶体 倾斜波前 强太赫兹脉冲 非线性效应 

分 类 号：O437[机械工程—光学工程]