Design Of Detector For Free-space Laser Communication

As the core device of the free-space laser communication system, the MSMdevice has some advantages, such as, low dark current, low capacitance, highbandwidth sensitivity and simple fabrication process, etc. To adapt to the environmentof the free-space laser communication system, we need the detector’s photosensitivesurface area is large enough. But with the area of the photodetector is larger, thedevice capacitance is proportional to the change to increased, the device bandwidthproportionally decreased. Therefore, the development of large area, high response rate,low signal to noise ratio detector to become the research focus of the present detector.This paper starts from the photoelectric characteristics of MSM-PD. According tothe band theory, analyzed the structural, optical and electronic properties of this device.The main work has several parts as shown:1On the base of the thermionic emission model of MSM photodetectors, weexplain the basic operating mode of InGaAs-MSM photodetectors.2The MSM epitaxial layer structure of semiconductor infrared detectors isdesigned.3The interdigital electrode size of a single point is designed.4The photoluminescence spectra and X-ray diffraction of epitaxial layer aretested.5The detector is packaged and the I-V characteristics,optical mixingcharacteristics and impulse response of the device are tested are tested.