Investigation On Precise Temperature Control And Spectral Response Characteristics Of Single-Photon Detector

Quantum communication is a hot research area in the field of modern quantum information.It has been developed rapidly in recent years because of the support of Chinese government.Single photon detector is the core device of quantum communication experiment.In this paper,a precise temperature control system is developed for single photon detector,and the temperature characteristics of photomultiplier tube(PMT)cathode photosensitive material are studied in detail.The main contents are as follows: 1.The noise problem that restricts the detection performance of the single photon detector is investigated thoroughly.It is found that most of the noise of the detector is thermal noise.In order to reduce the negative impacts of thermal noise on the detection performance,the thermal noise of PMT is significantly reduced and the performance of the single photon detector is greatly improved through the design of precise cooling scheme in this paper.2.A set of precise temperature control system based on PID algorithm for PMT single photon counting systemis developed.The rationality of PID algorithm is demonstrated by simulation in MATLAB/Simulink platform.The parameter trial rule of PID control system is obtained,and the parameter adjustment strategy is determined to speed up the temperature control process.3.Based on the high performance PMT(HAMAMATSU R980),a single photon detection system is built to detect the single photon produced by the single photon source under different temperature conditions.The experimental results show that cooling can greatly reduce the number of dark counts in the single photon counting system.The quantitative relationship between the temperature and the number of dark counts in the equipment is obtained.The results show that the single photon counting system can be used in quantum communication experiments.4.The relationship between temperature and PMT photocathode(Ag-O-Cs)light response spectrum is deduced based on the relationship between temperature and semiconductor energy bandgap in Varshni formula.The theoretical results show that when the temperature drops near room temperature,PMT light response spectrum will drift to the short wavelength direction at a rate of ～ 0.2nm/K.5.An experimental system of spectral temperature characteristic analysis based on wide spectral response PMT(HAMAMATSUR316-02,200 nm ～ 1200nm)was designed and built.Combined with the precise temperature control system,the temperature of PMT photosensitive surface was precisely controlled.The spectral response curves of PMT in the range of 750 nm ～ 850 nm at different temperatures were successfully measured.The experimental results show that the average drift rate of the spectral response curve near room temperature is 0.18nm/k,which is consistent with the theory.