Influence of thickness of methyl-orange-doped polyvinyl alcohol film on phase conjugate matched filtering

Phase conjugate matched filtering was performed with optical phase conjugation in Fourier-transforming backward degenerate four-wave mixing. A methyl-orange-doped polyvinyl alcohol (MO/PVA) film was used as a phase conjugator. The influence of the film thickness upon decay of a correlation signal due to phase mismatching was investigated. The thickness was varied from 15 mu m to 90 mu m. Reduction of the film thickness relaxes the tolerance for phase mismatching, which also occurs when a large reference picture is placed in a pump beam or when a reference picture shifts from the optical axis of the pump beam. Using a MO/PVA film of 15 mu m thickness, we obtained allowable angles of 3.4 degrees for a horizontally expanded reference picture and larger than 4.3 degrees for a vertically expanded reference picture, assuming about 40% reduction of a correlation signal is allowable.