Photothermal Transformation of Bessel Light Beams in Periodically Polarized Nonlinear Crystals

A mechanism of the formation of a photodeflection response in a periodically polarized nonlinear crystal illuminated by a Bessel light beam (BLB) is considered. The thermal-field distribution is found, and the exact solution of the system of heat-conduction equations is obtained using the Fourier–Bessel and Laplace integral transforms for a three-layer system consisting of a nonlinear crystal, a substrate, and environment. A method for controlling the amplitude of the photodeflection signal is proposed based on the application of axicons with an adjustable taper angle or optical schemes providing a change in the conicity of BLBs.