Model for two-beam coupling during the formation of holographic gratings with a nematic film-polymer-slice sequence structure

We present a model accounting for the main features of the wave coupling process that takes place during the UV curing of diffraction gratings made of liquid crystal films separated by slices of polymeric material. The effect depends on the phase shift between the curing interference pattern and the grating being cured. For a unit ratio of the impinging beam intensities, the model confirms the absence of energy transfer, as experimentally observed. When the ratio is not at its unit value, the beam coupling tends to equalize the intensities of the two beams as they propagate inside the sample.