Based On The Design And Characteristics Of The Very Weak Apd Infrared Light Detector

With the arrival of highly informationalized age, the security of information exchange becomes more and more important. Classical key is used in present security communication. Snooper can make duplicate or steal the classical key without being discovered. So this traditional encryption isn't safe enough. The greatest advantage of quantum security communication system is the security. It is based on the quantum mechanics and cryptography, the security is guaranteed by the basic quantum principle—Heisenberg's uncertainty principle and the quantum noncloning principle. Nobody can escape the discovery of the legal users.At present, the experiment and research of quantum security communication have already been developed at full speed. The research contents include the technology of single-photon source, quantum code, quantum information delivers, and single photon detection etc. Near-infrared single photon detection is one of the key problems of realizing the quantum security communication. Domestic research in this aspect is still relatively backward to foreign countries.The purpose of this article is in order to design a kind of steady, high-efficient and low noise single-photon detector system based on the character of commercially available avalanche photodiodes (APD), and do some previous technical research.Article introduces the background and mechanism of quantum cryptography, and the domestic and international recent research. We have analyzed the relative merits and development of single photon detectors. The special operation principle and several kinds of work patterns of APD in single-photon detection are introduced here. In this thesis we have analyzed and realized the single-photon pulse output by fiber optic coupler with attenuation method.We have made an overall design to the single-photon detection system in chapter three, including high-efficient low ripple direct current bias voltage of APD, temperature-controlled systems, designing of constant temperature cavity, ultra short pulse from cable and single photon signal distinguish technology.We have tested some kinds of APD of different company and have analyzed their temperature, gain and noise characteristic in chapter four. We found that the Epitaxx-APD has a good avalanche-gain characteristic, so this kind of APD is very suitable for...