Investigation On The High Performance Infrared Detection System

Infrared detection has very important application in physics, chemical, military field, especially with the rapid development of the technology of infrared and terahertz. There is an urgent need for high performance detection system which consisting of a good detector and reasonable detection system. Compared with other detectors in IR and THz region, quantum well photodetectors(QWPs) have their own advantages. In this paper, factors influencing the performance of the infraed and terhertz QWPs are studied firstly. Then, put forward a low background detection sysytem based on lamellar grating interferometer(LGI) for infrared weak signal detection.The first part of this paper is talking about detectors. We demonstrate an IR QWP with the peak response frequency of 9μm and a THz QWP with the peak response of 44μm sandwiched between Ga As and Al Ga As material. We systematically investigated the dark current characteristics of the QWPs in both theoretical and experimental ways, also the photoresponse. However, for the THz QWPs, the low BLIP temperature is the main factor limiting for the applications; we propose two schemes to improve the operating temperatures.In the second part of this paper, the design of a novel low-background spectrometer based on LGI is presented. Reducing background noise helps to improve the spectrometer system detectivity for detectors operating under background limited performance(BLIP) regime, and then improve the signal to noise ratio(SNR) of spectrometer. A lamellar grating interferometer based on a “cold” source and a “cold” detector becomes an extremely sensitive instrument because of the reduction of background radiation. In ideal case, the real BLIP detectivity obtained and corresponding SNR can be improved by three orders of magnitudes when background radiation is reduced from 300 K to 77 K. Besides, without cooling the interferometer, this configuration is more compact and easier-to-build compared to previously reported low-background Michelson spectrometer. This design has important significance for infrared sensitive detection.