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以可调谐CO2激光差频非线性GaSe晶体为例,在共线相位匹配方式下,计算了oe-e和oe-o两种相位匹配方式下的角度调谐特性、有效非线性系数、走离角和允许角。结果表明:GaSe晶体可产生73.84~3 000μm的太赫兹波,且有效非线性系数为41~54 pm/V;走离角在1.771°~10.63°之间;所允许的最大发散角为13.95~94.7μm.rad,对入射光的方向性要求较高。对于500μm以上的太赫兹波,两种匹配方式除有效非线性系数外没有大的区别。模拟结果对于开展基于激光差频技术产生太赫兹的研究具有重要的指导意义。
Taking tunable CO2 lasers, a nonlinear GaSe crystal, as an example, under the collinear phase matching method, the angular tuning characteristics, the effective nonlinear coefficient and the departure angle are calculated under the phase matching of oe-e and oe-o And allow angle. The results show that the GaSe crystal can produce terahertz wave with the wavelength of 73.84 ~ 3000μm with the effective nonlinear coefficient of 41 ~ 54 pm / V and the distance of departure from 1.771 ° ~ 10.63 °. The maximum allowable divergence angle is 13.95 ~ 94.7μm.rad, the direction of the incident light requires a higher. For terahertz waves above 500μm, there is no big difference between the two match modes except for the effective non-linear coefficients. The simulation results have important guiding significance for the research on terahertz generation based on laser beat frequency technique.