Research Of Superconducting Nanowire Single Photon Detection

The concept of quantum optics is firstly proposed by Einstein, this theory firstly show that light has two appearances:light is something which has two the behavior of wave and particle, light has wave-particle duality. Light is congregated by a large number of photons. Single photon detector which is based on the feature of quantum of light counts the number of photons in light. Single photon detector is importantly used in quantum optics, quantum information and quantum computation etc. To research the superconducting nanowire single detector (SNSPD) is the main work of this paper, the main contents of this paper as follows:make the chip of superconducting nanowire single detector. Package chip. Establish the cryogenic system. Design the signal amplifier. Establish the experimental system and discuss the quantum efficiency and dark count rate. For the last of this paper, optical experiments are carried out on SNSPD.At the beginning, kinds of single photon are presented, traditional and new type single photon detection is compared in quantum efficiency, resolution capability and dark count rate. As a new type single photon, SNSPD is becoming a hot research direction for its higher quantum efficiency, low dark count rate and good resolution capability.Fabricating the Nanometer thickness film with magnetron sputtering in Ar and N2, in the sputtering procession, the temperature of the Si substrate is kept350-600Celsius, at last the NbN film is successfully fabricated, the sputtering time decide the thickness of the NbN film, the thickness of the NbN film used in the SNSPD is5nm, in order to research the superconducting performance of the NbN film, four probe is used to detect the change of the film resistance when temperature changes, the critical temperature is about9.6K. the core area of the SNSPD is made up of the winding wire which width is200nm, electron beam lithography is used to fabricate the NbN nanowire, the make the Au electrode and package the device with the photosystem, the electrode is extracted by coaxial line. The device of SNSPD is put in low temperature, coaxial line is use to provide the bias current Ib which is lower than the NbN nanowire critical current Ic, the superconductivity will be suppressed when a photon is absorbed, the voltage pulse signal is generated, because the signal is too small, the high speed amplifier should be used to amplify the voltage signal, to detect the voltage pulse signal realizes the single photon detection. Combine the experiments and theory to analyze the quantum efficiency and dark counts in this paper. At last, the SNSPD was used to count the number of the photons after the light waves pass through the hole.