为了获得2.15~1 500 μm的相干光源，研究了CO激光在高质量非线性晶体ZnGeP2和GaSe中的混频效应。为了提高转换效率，在激光锁模方式下对CO激光器的二次谐波、和频和差频的产生进行了研究。结果显示，利用GaSe晶体和ZnGeP2晶体，调Q多谱线CO激光辐射的谱线内倍频效率分别大于0.3%和1.1%。采用ZnGeP2晶体进行倍频时，可调谐锁膜CO激光器的转换效率为12.5%。模拟结果显示，二次谐波与和频产生的输出光谱相同。相邻谱线下，和频和差频的产生过程中，基波和一次谐波可以分别在4.0~5.0 μm和100~≥1 200 μm (太赫兹范围)形成振荡。利用锁模CO激光器在ZnGeP2晶体中的混频效应，可以得到2.15~≥1 500 μm的相干光源，同时转换效率可达到甚至高于12.5%。

The CO laser frequency mixing in high-quality ZnGeP2 and GaSe crystals is studied to obtain the 2.15-1 500 μm coherent sources. Secondary Harmonic Generation(SHG), sum- and difference frequency generations are considered as a method for the CO laser frequency mixing and the mode-locking as an efficient way to improve the mixing efficiency.Results show that the internal SHG efficiency of Q-switched multiline CO laser radiation has exceeded by 0.3% for GaSe crystal and has reached by 1.1 % for ZnGeP2 crystal. When the SHG is in ZnGeP2, the internal efficiency of electron beam sustained discharge frequency-tunable mode-locking CO laser is up to 12.5 %. Simultaneous SHG and sum frequency generation show the same output spectrum. It is shown by modeling that the sum and difference frequency generations of neighboring lines of both fundamental and first overtone bands can allow one to get the oscillation,respectively, at 4.0-5.0 μm and 100-≥1 200 μm (THz). In conclusions, the frequency mixing of mode-locked CO laser emission lines in ZnGeP2 crystals allows some one to design 2.15-≥1 500 μm coherent sources with the power frequency conversion efficiency up to or over 12.5%.