高性能85mm短腔光学参变振荡器的THz电磁波输出特性分析

报道了以MgO∶LiNbO3为非线性光学介质,采用85 mm长的法布里珀罗单谐振腔结构形式的光学参变振荡器,产生THz电磁波的实验结果。使用波长为1064 nm的Nd∶YAGQ开关脉冲激光器作为抽运光源,通过改变入射角度使参变振荡器的相位匹配条件发生变化。采用Si真空量热器,并利用THz波干涉测量仪;或通过测量闲频光的频率对产生的THz波频率进行了测量。实验表明该参变振荡器输出频率调谐范围为0.9~3.0 THz。在抽运光能量为20 mJ/pulse,脉冲宽度16 ns,重复频率50 Hz条件下得到输出峰值位于1.2 THz,能量为102.5 PJ/pulse的THz波输出。通过引入Si棱镜阵列减小了THz波在晶体中的全反射,从而提高THz波的能量输出。使用金属缝隙探测器,对辐射的THz波的波束水平方向空间分布进行了测量,分析了Si棱镜阵列的衍射效应对THz波束空间分布的影响。

Analysis of THz Electromagnetic Wave Output Character Based on High Performance 85mm Short Cavity Optical Parametric Oscillator

The THz wave output with the 85 mm F-P single cavity optical parametric oscillator based on the MgO∶LiNbO3 crystal was reported. The Nd∶YAG Q-switched laser with 1064 nm was used as the pump source, and the THz wave was tuned by changing the incident angle as well as the phase matching condition. THz wave frequency can be detected with the THz interferometer and the Si bolometer, or by detecting the idle light frequency. Experimental results indicate the THz wave is 0.9～3.0 THz tunable. The peak energy output is 102.5 pJ/pulse at 1.2 THz with the pump energy of 20 mJ/pulse, pulse width of 16 ns, repetition rate of 50 Hz. THz energy output was increased when a Si-prism array was introduced to decrease THz wave's total reflection at the interface of crystal. The THz wave beam pattern along the horizontal was measured with a metal-slit-detector. The influence of diffraction effect of the Si prism array on the THz wave beam spatial profile was discussed.