Research progress of point defects effects on optical properties of ZnGeP₂ crystals

ZnGeP₂ crystal is an important frequency conversion material for the mid-infrared region due to its large nonlinear optical coefficient and broad transparency range. Unfortunately, a serious limitation to the development of ZnGeP₂-based applications is the presence of point defects-related extra optical absorption. The progress of the point defects affecting optical property in ZnGeP₂ was summarized in detail in the paper. The point defects models of ZnGeP₂ were studied by electron paramagnetic resonance technique. The mechanisms of the point defects affecting optical property in ZnGeP₂ were analyzed by combining optical absorption and electron paramagnetic resonance methods. The methods reducing the extra optical absorption were introduced. Finally, the trends in the investigation on point defects and optical property in ZnGeP₂ were prospected.