High-light-level variance of estimators for intensity interferometry and fourth-order correlation interferomel

The variance of certain estimators relevant to intensity interferometry, laser speckle correlography, and fourth-order correlation interferometry are considered when the field amplitude obeys circular complex Gaussian statistics and the classical or high-light-level regime is obtained. A family of optimal unbiased estimators for |μ(Δ)|2, the squared modulus of the spatial-coherence factor, is found when a single measurement is performed and 〈I〉, the mean intensity, is known a priori. Calculations of the variance of multiple-measurement estimators for |μ(Δ)|2 and μ*(Δ)μ*(Δ + e) are performed. Results of statistical measurements of laser speckle are presented and are shown to agree with the calculations.