脉冲前沿倾斜的光学整流THz辐射特性分析  

Analysis on THz radiation characteristics in optical rectification by tilted-pulse-front pumping

作　　者：孟庆龙[1] 曾冰[1] 叶荣[1] 于军立 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

出　　处：《红外与激光工程》2015年第9期2643-2648,共6页Infrared and Laser Engineering

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)

摘　　要：光整流法是目前产生太赫兹(THz)辐射的重要方法之一。建立了采用脉冲前沿倾斜方法实现相位匹配条件的基于光整流法产生太赫兹辐射的转换效率理论模型,比较了脉冲前沿倾斜方式的不同倾斜角对THz辐射转换效率的影响,定量分析了光整流THz辐射转换效率的主要影响因素及其规律,并讨论了飞秒激光参数和晶体参数对THz辐射转换效率的影响。结果表明:脉冲前沿倾斜方式相位匹配条件中的倾斜角对THz辐射转换效率的影响非常大;THz辐射转换效率随着飞秒激光脉宽的增大呈现先增大后减小的规律,且随飞秒激光强度的增大而增大。此外,THz辐射转换效率不仅随着晶体吸收系数的增大而急剧减小,而且随着晶体厚度的增加呈现先逐渐增长,到达一定晶体厚度后,则几乎不随晶体厚度的增长而变化的规律。由此可见,在实际应用中,不仅要求采取措施尽可能满足位相匹配条件和减小晶体对THz辐射的吸收,而且还需要合理选取飞秒激光参数和非线性晶体参数。Optical rectification is one of the important techniques for efficient generation of terahertz pulses. The theoretical model of the optical-to-terahertz conversion efficiency in optical rectification by tilted-pulse-front pumping was built. On the basis, the influence of the different tilted angles from tilted- pulse-front pumping on the conversion efficiency was compared. The effect of the important factors on the optical-terahertz conversion efficiency was analyzed quantitatively, and the influence of the parameters of both the crystals and the femtosecond pulses on the conversion efficiency was discussed. The results show that the influence of the titled angle on the optical-terahertz conversion efficiency was very obvious. The optical-terahertz conversion efficiency increases first and then decreases with the increasing of the pulse duration, where as it increases with the intensity pump pulses. In addition, the optical-terahertz conversion efficiency decreases rapidly with the increasing of the absorption, while increases and then remains unchanged with the increasing thickness of the crystal. Hence it is not only necessary to take measures to meet phase-matching condition as far as possible and decrease the terahertz absorption in the crystal, but also choose optimal parameters of the femtosecond pulse and the nonlinear crystal.

关 键 词：非线性光学 转换效率 光整流 脉冲前沿倾斜 吸收 

分 类 号：O437[机械工程—光学工程]