InGaAS PIN photodetector is a kind of semiconductor optical-electrical conversion device that enhances the radiation trapping efficiency of electrons and holes by adding an intrinsic layer I in the middle of PN junction composed of IGaAs, component materials, which in turn improves the efficiency of photoelectric conversion and the response speed, and it has the advantages of good linearity in photoelectric conversion, as well as high sensitivity, fast response, wide-band measurement, and low noise.