Fig. 1. Schematic of low noise InGaAs/InP SPD with tunable gate frequency. PG, pulse generator; SPAD, single-photon avalanche diode; Var Cap, variable capacitor; LNA, low noise amplifier; CMP, comparator. (a) SPAD response to the gate signal. (b) Variable capacitor response to the gate signal. (c) Balun output after delay adjustment. The vertical scale in (c) is scaled up to 5 as compared to (a) and (b) for clarity.

Fig. 2. Avalanche signals recorded by the oscilloscope. (a) Avalanche signals after the capacitive cancellation. (b), (c), (d), and (e) show avalanche signals after delay cable adjustment at 1 MHz, 10 MHz, 100 MHz, and 1000 MHz gating frequency, respectively.

Fig. 3. (a) Relationship between dark count rate and detection efficiency under different gate frequencies; (b) relationship between afterpulse probability and detection efficiency under different gate frequencies.

Fig. 4. (a) Effective gate width measurement by scanning the relative delay between optical pulses and gates at 1 GHz gate frequency with a detection efficiency of 20%. (b) Time histogram of detection events. The inset shows the zoomed waveform of the peak histogram.