Some characteristics of dyed gelatin films when polarization gratings are recorded are reported. Two dyes, Malachite Green and Methylene Blue, are used in our experiment. In particular, no dichromate was added to Methylene Blue plates before or after exposure. It is shown that, in spite of its having high viscosity, a relief grating is formed when orthogonal linearly polarized beams are superimposed upon the plates. In contrast with previous observations in another photoanisotropic medium, the frequency of the gelatin relief grating does not depend on the directions of the electric field of the orthogonal recording beams. Besides, when orthogonal circularly polarized beams are used in the formation of polarization gratings, no relief grating is produced. Finally, we study the phase modulation obtained after dehydration of the gelatin plates in which the polarization gratings were formed. Postdevelopment phase gratings do not preserve the polarization information of the interference pattern. Also, the grating frequency is increased by a factor of 2 for linear polarization, whereas for circular polarization there is no phase modulation.
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