Guo-Qun Chen, Hong-Yang Zhao, Shun Wang, Xiangying Hao, Hai-Wei Du, and Rui-Bo Jin
Schematic diagram of cascaded difference frequency. The propagation directions of the pump, the signal and THz wave are along the x axis, while their polarization directions are along the z axis.
https://www.osapublishing.org/osac/fulltext.cfm?uri=osac-4-8-2330&id=454030
Highly efficient terahertz (THz) wave sources based on the difference frequency generation (DFG) process in nonlinear optical crystals plays an important role for the applications of THz waves. In order to find more novel nonlinear crystals, here, we theoretically investigate the generation of THz waves using the isomorphs of periodically poled KTiOPO4 (PPKTP), including periodically poled RTP, KTA, RTA and CTA. By solving the cascaded difference frequency coupled wave equations, it is found that the intensities of the THz wave generated from the cascaded difference frequency processes are improved by 5.27, 2.87, 2.82, 3.03, and 2.76 times from the non-cascaded cases for KTP, RTP, KTA, RTA and CTA, respectively. The effects of the crystal absorption, the phase mismatch, and the pump intensity are also analyzed in detail. This study might help to provide a stronger THz radiation source based on nonlinear crystals.
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