Photon Number Distributions

expectation value

This Demonstration shows photon count distributions (probability distributions) of an ideal laser light source (Poisson distribution) and a thermal radiation source (Bose-Einstein distribution). In the interactive plots both functions have the same expectation value (mean). For the Poisson distribution, the expectation value and variance of the photon number

n

coincide; on the other hand, the variance of the thermal photon number distribution goes beyond its expectation value.