Waveguide-coupled Superconducting Nanowire Single-Photon Detectors Based on Femtosecond Laser Direct Writing.

The implementation of quantum information technologies requires the development of integrated quantum chips. Femtosecond laser direct writing (FLDW) waveguides and superconducting nanowire single-photon detectors (SNSPDs) have been widely applied in integrated quantum photonic circuits. In this work, a novel FLDW waveguide-coupled SNSPD was designed and realized by integrating FLDW waveguides and conventional SNSPDs together. Through a COMSOL simulation, a waveguide end face-nanowire optical coupling structure was designed and verified. The simulation results showed that the FLDW waveguide-coupled SNSPD device, which had a target wavelength of 780 nm, can achieve 87% optical absorption. Then the preparation process of the FLDW waveguide-coupled SNSPD device was developed, and the fabricated device achieved a system detection efficiency of 1.7% at 10 Hz dark count rate. Overall, this method provides a feasible single-photon detector solution for future on-chip integrated quantum photonic experiments and applications.