Superconducting Nanowire Single Photon Detector with Optical Cavity
Jie Liu, Li-Qun Zhang, Zhen-Nan Jiang, Kamal Ahmad, Jian-She Liu, Wei Chen**
Tsinghua National Laboratory for Information Science and Technology, Department of Microelectronics and Nanoelectronics, Institute of Microelectronics, Tsinghua University, Beijing 100084
Abstract：Increasing the detection efficiency (DE) is a hot issue in the development of the superconducting nanowire single photon detector (SNSPD). In this work, a cavity-integrated structure coupled to the SNSPD is used to enhance the light absorption of nanowire. Ultra-thin Nb films are successfully prepared by magnetron sputtering, which are used to fabricate Nb/Al SNSPD with the curve of 100 nm and the square area of $4\times4$ μm$^2$ by sputtering and the lift-off method. To characterize the optical and electrical performance of the cavity-integrated SNSPD, a reliable cryogenic research system is built up based on a He$^{3}$ system. To satisfy the need of light coupling, a packaging structure with collimator is conducted. Both DE and the dark count rates increase with $I_{\rm b}$. It is also found that the DE of SNSPD with cavities can be up to 0.17% at the temperature of 0.7 K under the infrared light of 1550 nm, which is obviously higher than that of the SNSPD directly fabricated upon silicon without any cavity structure.
2016, Vol. 33 
