Study of Optical Rectification in Polycrystalline Materials Based on Random Quasi-Phase Matching

Abstract

Random quasi-phase matching (RQPM) in polycrystalline materials has been considered as an important technique for nonlinear optical frequency conversion, especially in wideband laser generation involving femtosecond lasers. In this paper, optical rectification (OR) based on RQPM in ZnSe ceramics was investigated for the first time, which could convert ultrashort optical pulses to broadband terahertz waves. A theoretical model of RQPM OR was built, with which the effects of material grain size, thickness, pump wavelength and pump pulse duration on terahertz generation, were simulated and discussed. It was found that RQPM OR in ZnSe is indeed effective in terahertz generation but insensitive to the material grain size and pump wavelength RQPM OR is even better than traditional single crystals such as ZnTe in bandwidth and robustness. The results can be a reference to optimize the RQPM OR nonlinear process, and hopefully, this work will promote the application of costless polycrystalline materials in the hot field of terahertz generation.