The problem of phase retrieval appears in optical spectroscopy when a power spectrum P(ω) = |f(ω)|2is measured while the entire complex function f(ω) = |f(ω)| exp iθ(ω) is needed for obtaining the desired material properties. Recently we proposed a new approach to solve this problem in optical spectroscopy by using the maximum entropy model. Here we give a short review of its theory and show how to improve the phase retrieval procedure to work well in practice. The usage and applicability of the procedure, especially in reflectance spectroscopy of solids, are demonstrated with practical examples. Its use in other applications is also discussed.
Erik M. Vartiainen, Kai-Erik Peiponen, and Toshimitsu Asakura, "Phase Retrieval in Optical Spectroscopy: Resolving Optical Constants from Power Spectra," Appl. Spectrosc. 50, 1283-1289 (1996)