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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。
The experimental results of the THz electromagnetic wave generated by the optical parametric oscillator with Fabry - Perot single cavity of 85 mm length using MgO: LiNbO3 as nonlinear optical medium were reported. The Nd: YAGQ switched pulsed laser with a wavelength of 1064 nm is used as the pumping light source, and the phase matching condition of the parametric oscillator is changed by changing the incident angle. The Si vacuum calorimeter was used and the THz wave interferometer was used; or the THz wave frequency generated was measured by measuring the frequency of idler light. Experiments show that the parametric oscillator output frequency tuning range of 0.9 ~ 3.0 THz. The THz wave output with peak energy of 1.2 THz and energy of 102.5 PJ / pulse was obtained under the conditions of pumping energy of 20 mJ / pulse, pulse width of 16 ns and repetition frequency of 50 Hz. The total reflection of THz wave in the crystal is reduced by introducing the Si prism array, so as to improve the energy output of the THz wave. The metal slit detector was used to measure the beam horizontal spatial distribution of THz wave radiation. The influence of the diffraction effect of Si prism array on the spatial distribution of THz beam was analyzed.