Superconducting Nanowire Single-Photon Detectors Working At Mid-Infrared

Superconducting nanowire single-photon detectors(SNSPDs)have achieved high system detection efficiency(>90%),high count rate(the maximum count rate of 16 SNSPD arrays is greater than 1.5 GHz),low dark count rate(<0.5 Hz),low timing jitter(<5 ps)and other excellent performance in the near-infrared band,which make SNSPDs attractive to many applications in science and engineering.However,compared with SNSPDs working at near-infrared,SNSPDs working at mid infrared still has many difficulties from device to system.To solve the problems above,this thesis focuses on the following two aspects: the setting up of SNSPD detection system and the design and characterization of SNSPDs at mid-infrared.In the aspect of setting up the SNSPD system,the design,implement and characterization of actively aligned and self-aligned system are performed.The actively aligned system uses nano-positioners to align the incident light with the photosensitive area of meandering superconducting nanowire avalanche photodetector(SNAP)and achieves the detection efficiency of 17.5% at 1550 nm.The self-aligned system is based on the self-aligned package,enabling the characterization of 8-channel arced fractal SNAPs.The arced fractal SNAP with the best performance is selected and the detection efficiency of 90.1% is achieved at 1590 nm.For the device design at mid-infrared,the design of the optical cavity structure at2-micronmeter is carried out,and the simulation results show that the absorptance is more than 90%.For the characterization of SNSPD at mid-infrared,the measurements of detection efficiency and timing jitter of the curved fractal device at 1993 nm are completed and the sources of timing jitter are analyzed in detail.