title: Observation of two-wave coupling during the formation of POLICRYPS diffraction gratings.
abstract: We report on the experimental observation of two-wave mixing that occurs inside a sample between the beams used for the fabrication of polymer-liquid-crystal-polymer slices (POLICRYPS) diffraction gratings. The effect depends on the phase shift between the curing interference pattern and the grating being cured. This shift can be mechanically induced by accidental vibrations of the experimental setup; thus a high setup stability is needed. We devised a mechanism that enables us to control setup vibrations in situ and used it to monitor the experiment. When the mechanically induced shift was significantly small, wave mixing was observed only if the initial intensities of the two curing beams were different from each other.
authors.affiliation: Liquid Crystals Laboratory, National Institute for the Physics of Matter, Center of Excellence CEMIF.CAL, Department of Physics, University of Calabria, 87036 Arcavacata di Rende, CS, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Caputo
authors.forename: Luciano
authors.initials: L
authors.lastname: De Sio
authors.forename: Alessandro
authors.initials: A
authors.lastname: Veltri
authors.forename: Cesare
authors.initials: C
authors.lastname: Umeton
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Sukhov