2.5 GHz Gated InGaAs/InP Single-Photon Avalanche Diode with 44 ps Time Jitter

Abstract

Gated single-photon avalanche diodes (SPADs) are practical solutions for quantum key distribution (QKD) applications. However, the gating frequency is limited by time jitter and afterpulse probability when SPADs operate at a frequency higher than 2 GHz. We find that filter distortion and variation of signal amplitude are the dominant mechanisms for time jitter in high-frequency scenarios, and design a specific low-pass filter (LPF) and a zero crossing discriminator to reduce the time jitter effectively. Specifically, the LPF extracts avalanche signals and forms accurate zero crossing points by its impulse response, and the zero crossing discriminator correctly discriminates avalanche signals to achieve low time jitter. When the SPAD is operated at a gating frequency of 2.5 GHz with a detection efficiency of 21%, the time jitter and afterpulse probability are 44 ps and 1.4%, respectively. Our results pave the way to practical QKD systems at higher clock rates.