Second harmonic generation by bessel light beams in a nonlinear regime

Abstract

The summary form only given. The processes of summation-subtraction of frequencies of Bessel light beams (BLB) allow not only to tune a wavelength of laser radiation, but also to change the order of screw wavefront dislocations. Unlike Gaussian beams, Bessel beams permit to realize a multichannel nonlinear process, determined by the type of vector interaction. In the report the results of analytical examination and numerical simulation of multichannel nonlinear processes are presented on the example of SHG pumped by BLB. The fields at the fundamental and doubled frequencies in each channel are BLBs with different longitudinal and transverse wave numbers. Thereof each of SHG channels is characterized by the parameters of phase-mismatch and overlap integral. The given parameters express the requirements of longitudinal and transverse SHG phase-matching and determine the efficiency and spatial structure of radiation of the second harmonics. As a result, the SHG process, for example, of oo-e type, is described by a system of 2M coupled equations of the parabolic type, where M is the number of generation channels. The numerical solution of the given system of equations is carried out and the spatially-angular structure of the second harmonics field is obtained depending on the radial wave number and the width of input BLB at the fundamental frequency, its power, and also parameters of a nonlinear crystal. The regimes of generation of a single-component (ring or axial) and two-component SHG field, and also the tuning of the radius of a ring component are investigated at changing the direction of the collinear phase-matching.