Advanced chip package of a fiber coupled superconducting single photon detector for a closed-cycle cryostat

摘要

Superconducting single photon detectors are promising candidates for cutting-edge applications like space-to-ground communication and quantum-key-distribution. The challenge is to transfer the assembly technology from university research to industrial processes. Especially the positioning of the optical fiber with respect to the active area of the superconducting detector are open questions. We demonstrate the operation of a superconducting nanowire single photon detector (SNSPD) in a closed cycle cryostat. The thermal coupling between superconducting detector chip and closed-cycle cryostat is investigated. The possibility to mount the optical fiber in an RIE-ICP-etched hole in a silicon carrier wafer is demonstrated. Different illumination wavelength and intensities are used to validate the SNSPD assembly in the closed cycle cryostat. Further, an advanced package of the silicon carrier wafer and the SNSPD-chip is introduced. In this package, the SNSPD-chip is mounted via flip-chip technology on the silicon carrier wafer. The striven flip-chip position accuracy of ± 1 μm ensures the accurate coupling between optical fiber and active area of the SNSPD.