Abstract

A number of experiments have been carried out in which quadrature and photon-number squeezed light have been generated. The signature of both is a sub-Poisson photoelectron number (or equivalently a sub-shot-noise photoelectron current). The photomultiplier tube (PMT), with a large amplification and low excess noise factor, is often a preferred detector in such experiments. The detectability of nonclassical light by a PMT can be reduced by the presence of background noise, the most deleterious of which is caused by Cherenkov photon emissions from clustered cosmic-ray cascade particles as they transverse the faceplate of the PMT. We have empirically determined that cosmic-ray events can be substantially avoided by using experimental durations of less than tens of seconds. However, for experiments that cannot be conducted in such short periods of time, cosmic- ray clusters may pose a significant limitation. The fluctuations of extensive air-shower particles at ground level turn out to be well described by the two-parameter Poisson-driven Yule-Furry or by the negative-binomial counting distribution. Experimental results for various PMTs operated in the dark are presented along with theoretical predictions.

© 1987 Optical Society of America