Self-Action of Light Beams in an Amorphous Azobenzene Polymer

We report an experimental study of the self-action of TEM₀₁ and TEM₀₀ Gaussian modes in a layer of a comb-shaped amorphous polymer with cyanobiphenyl and azobenzene side fragments. For the linearly polarized TEM₀₁ mode, a pattern of aberration self-action is observed in the form of rings with an additional system of the fringes, caused by interference from two intensity peaks. The position of the fringes and the microscopic image of the deformation region correspond to the local nature of the nonlinear optical response. For the circularly polarized (with an ellipticity of about 7%) TEM₀₀ Gaussian mode, the polarization of the outer aberration ring is close to linear. This effect stems from the self-rotation of the polarization ellipse due to the manifestation of Kerr-type nonlinearity. A characteristic feature of this effect in an amorphous polymer is an increase in the eccentricity of the ellipse (transformation of circular polarization into linear polarization), which is caused by a light-induced change in the orientation distribution function of the chromophores.