Stochastic resonances in photon number resolving detectors

The photon number statistics of a coherent optical pulse will typically follow a Poissonian distribution. At low photon numbers, a gated avalanche photo-detector (GAPD) is used to detect the presence of photons in each optical pulse. GAPDs use a thresholding logic, but suffer from after-pulsing effects. The efficiency of a GAPD was characterized and its after-pulses were analyzed by looking at the detection patterns obtained. The GAPD was found to show evidence of stochastic resonance which affected the dark noise of the detector. We post-process the detected bit patterns to eliminate the resonances and estimate the true dark count of the detector. The GAPD was then used with a recirculating optical loop to build a multi-photon resolving detector (MPRD). In the MPRD, the probability of detection at consecutive loop round trip times were used to estimate the mean photon number. We quantify these statistics and establish a reliable measure of photon number at an optical power of −94 dBm. The digital electronics was able to store data for 2²⁴ optical pulses, making the statistical analysis meaningful.