Estimation of the squared modulus of the mutual intensity from high-light-level intensity measurements
The problem of estimating the squared modulus of the mutual intensity (or the complex coherence factor) from high-light-level intensity measurements is addressed for the situation in which the fluctuations of the complex-valued amplitude are governed by circular-Gaussian statistics and the light level is high enough that all nonclassical fluctuations of the measurements can be ignored. A lower bound on the variance of any unbiased estimator is presented, and this bound is compared with the variance of Ebstein's polynomial estimators [J. Opt. Soc. Am. A 8, 1450 (1991)] along with the variance of the maximum-likelihood estimator.