Physical method and optical elements for improving radiation quality of wide-aperture lasers

On the basis of fundamental research, a method for improving the quality of laser radiation at Fresnel numbers greater than one is proposed. The method consists in providing the generation of a ''pure'' high-order Laguerre-Gaussian ring mode and subsequent local phase correction. and includes the control of multi-pass modes, that are the main cause of deterioration in the quality of the radiation of such lasers. The proposed approach makes it possible to significantly increase the laser power at a divergence close to that of a Gaussian beam. The beam divergence calculations were carried out in accordance with the original numerical model. It is shown that during the propagation of the radiation beam having a different number of co-phase rings in the initial intensity distribution the field distribution evolves to a ring mode of the lowest order. More advanced novel polarization-selective optical elements (axicon and diffraction mirror) that form the basis of the proposed method have been developed for high-power lasers.