Holographic formation of phase diffractive elements for light beams conversion with photo-induced absorption coefficient changing in PDLCs

Abstract

A theoretical model of the holographic formation of diffractive optical elements for the Gaussian light beams conversion into Bessel-like ones in polymer-dispersed liquid crystals (PDLCs) is developed. The model is based on the solution of the kinetic equations of photopolymerization-diffusion processes of holograms recording in PDLCs by light beams with inhomogeneous amplitude and phase spatial distributions. The model additionally takes into account the photo-induced changings in the absorption coefficient of the PDLC. It is shown that the absorption changings decreases the rate of the refractive index’s spatial profile decline over the thickness of the material. In this case, when the characteristic time of the absorption changing is much less than the characteristic polymerization time (the absorption changes more rapidly than the photopolymerization takes place), the diffractive element can be characterized by a homogeneous distribution of the refractive index over the thickness.