14-MHz rate photon counting with room temperature InGaAs / InP avalanche photodiodes

We have developed high speed gated-mode single-photon counters based on InGaAs/InP avalanche photodiodes for use at 1.55μm wavelength. Operation at room temperature allows afterpulse probability to be below 0.2% for gate rates up to 14 MHz. We obtained optimum noise-equivalent power of 2.2× 10−15W/Hz1/2 at 14% quantum efficiency with dark-count probability of 0.2%. We propose a metric (noise-equivalent power divided by gate frequency) for comparing high speed photon counters and show that for this metric our system outperforms previously reported counters at 1.55μm wavelength. We demonstrate that for gate widths of a nanosecond or below, the differing amplitude distributions of dark vs. light counts allow an optimal decision threshold to be set for a given bias voltage.