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为提高太赫兹(THz)波的产生效率,研究了飞秒激光与GaAs晶体的相互作用。首先研究了块状GaAs晶体中泵浦光与THz波间的相位匹配,结果显示泵浦光的群折射率曲线与THz波的折射率曲线不存在交点,表明了块状晶体结构中相位失配问题的存在;然后设计了四种不同尺寸的波导结构,根据波导理论计算了波导结构在0.1~6 THz波段的折射率,并结合波导的吸收和色散参数分析了THz波在晶体中的最佳传输距离。研究结果表明,GaAs波导结构能够有效增大泵浦光与THz波的相位匹配程度,从而提高飞秒激光与晶体耦合过程中THz波的产生效率。研究为基于飞秒激光与GaAs晶体相互作用的高效THz产生技术提供了理论依据。
In order to improve the generation efficiency of THz wave, the interaction between femtosecond laser and GaAs crystal was studied. The phase matching between the pump light and the THz wave in the bulk GaAs crystal was first studied. The results show that there is no intersection of the refraction index curve of the pump light with that of the THz wave, indicating the phase mismatch in the bulk crystal structure Then, four kinds of waveguides of different sizes were designed. According to the waveguide theory, the refractive index of the waveguide structure in the 0.1-6 THz band was calculated, and the best THz wave in the crystal was analyzed with the absorption and dispersion parameters of the waveguide Transmission distance. The results show that the GaAs waveguide structure can effectively increase the phase matching between the pump light and the THz wave and improve the THz wave generation efficiency in the femtosecond laser-crystal coupling process. The research provides a theoretical basis for efficient THz generation technology based on the interaction between femtosecond laser and GaAs crystal.