Phase Problem in Coherence Theory

Abstract

For a class of quasi‐monochromatic spectra, including Lorentzian and Gaussian line shapes, it is shown that knowledge of the modulus of the complex degree of temporal coherence γ(τ) does not suffice to reconstruct the spectrum. This is due to the existence of zeros of γ(τ) in the complex τ plane, giving rise to a significant contribution to the phase of γ(τ). The position of the zeros and their physical interpretation are investigated. The case of band‐limited spectra is also treated, and some general properties of the distribution of zeros in this case are given.