Integration of InGaAs/InP Single Photon Avalanche Diode and Thin Film Lithium Niobate Photonic Chip via Photonic Wire Bonding

Abstract Thin‐film lithium niobate (TFLN) is a powerful platform for integrated quantum photonic chips thanks to its excellent performance on high‐speed optical modulation, low waveguide loss, and strong nonlinear effects. However, realizing compact and cost‐effective single‐photon detection on TFLN photonic chips is challenging. Photonic wire bonding (PWB) is a flexible chip‐to‐chip and chip‐to‐fiber optical interconnection technology. In this work, PWB technology is used to achieve hybrid integration of InGaAs/InP single‐photon avalanche diodes (SPADs) and TFLN photonic chips. A suspended polymer waveguide with a span over 300 µm is fabricated by two‐photon polymerization to connect the TFLN dual‐layer coupling structure (DLCS) and the photon‐sensitive area of the SPAD, through which high‐performance optical coupling between the TFLN photonic chip and the SPAD is achieved. Experiments show that the integrated SPAD has an on‐chip photon detection efficiency (PDE) of 13.8% at −30 °C, with a dark count rate (DCR) of 6 × 10 −4 Hz/gate, an after‐pulse probability (APP) of 3%, and a time jitter of 370 ps. This work shows that PWB provides a convenient solution for the hybrid integration of single‐photon detectors on TFLN photonic chips, which has great potential for developing compact and low‐cost on‐chip systems for quantum communication, quantum information processing, and weak light sensing.