High responsivity mid-infrared indirect detection based on nonlinear crystal BaGa4Se7

Currently, non-oxide BaGa4Se7 crystal has been demonstrated as a superior nonlinear medium for both coherent mid-infrared (MIR) generation and up-conversion detection. By bridging the desired MIR region to the well-developed near-infrared devices, the latter addresses the drawbacks of traditional direct detection. Based on our recent report, a comprehensive study is conducted on the nonlinear optical up-conversion process to achieve high responsivity. An analytical model is developed and verified through experiment. Their measurement and calculation cover the relationship between the up-converted signal and the two input lights, the acceptable angle of detection crystal, and the responsivities at a wavelength ranging from 3 to 8 mu m. The dependence of responsivity on experimental factors is indicated by the model. The present study provides a theoretical reference for the calibration and optimal design of this detection system, which can also be applied to other general MIR up-conversion configurations.