Photorefractive gratings recording in reversible polymer films containing 4-keto bacteriorhodopsin under absorption saturation

Because the change in the dielectric constant of the medium is proportional to the concentration of bacteriodopsin (BR) molecules in photoexcited state, the absorption saturation leads to steady-state amplitudes of phase grating written in BR by sufficiently intense light beams. Here we describe peculiarities of the initial stage of the grating writing under the absorption saturation, which can be explained by existence of two photocycles