Development of Fiber-Coupled Four-Element Superconducting Nanowire Single-Photon Detectors

We report on the development of fiber-coupled 4-element superconducting nanowire single photon detector arrays. The SNSPD arrays consist of four nanowire elements which are placed into a sensitive area with 15 ¥ 15 μm2square. The device was mounted into small chip-mounting block with four tiny connectors which can pass high frequency signals up to 110 GHz, and each element was connected to each connector through CPW line. The single-mode optical fiber with GRIN lens was fixed to fiber-holding block and was joined to chip-mounting block from back side and aligned accurately so that the light spot irradiate to the center of device sensitive area. The fiber coupled package is then installed into closed-cycle cryocooler system and cooled down to 2.3 K. All four elements were able to detect single photon event, and total system DE reached to 8.07%.