Optical spectral analysis of signals recorded on a pure phase medium

A method of coherent optical spectral analysis for signals recorded on a pure phase medium is proposed and analyzed. The signal record is a transparent strip that consists of three regions, each of which has a constant phase delay associated with it. The boundaries of the symmetric central region are graphs of the signal to be analyzed. The signal record is Fourier transformed in a coherent optical processor, and the amplitude distribution along the fx axis in the Fourier plane gives the signal spectrum. A phase-only medium has been assumed here because it is characteristic of some spatial light modulators (such as thermoplastic) that permit processing in real time. Qualitative verification of the proposed method was obtained from experiments, and the results are in good agreement with the theoretical conclusions.