Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan.
Opt Lett. 2012 Oct 1;37(19):4155-7. doi: 10.1364/OL.37.004155.
It is theoretically shown that application of a phase mask in optical rectification scheme is equivalent to spatial modulation of the crystal's nonlinear coefficient in cross-section plane of the laser beam. It allows using the technique of quasi-phase-matching for efficient noncollinear terahertz (THz) generation by using high-power wide-aperture optical beam. According to calculations, the linewidth of THz generation can be varied from 10 GHz to a few THz by changing the optical beam size. It is shown that the frequency of THz generation can be also tuned by building the image of the phase mask in the crystal with variable magnification.
从理论上证明，在光整流方案中应用相位掩模相当于在激光束的横截面平面内对晶体的非线性系数进行空间调制。这使得能够使用准相位匹配技术，通过使用高功率宽孔径的光束来有效地产生非共线太赫兹（THz）。根据计算，通过改变光束尺寸，可以将 THz 产生的线宽从 10GHz 变化到几个 THz。结果表明，通过在晶体中构建具有可变放大率的相位掩模的图像，也可以调整 THz 产生的频率。
