Characteristic features of the operation of different designs of the Faraday isolator for a high average laser-radiation power

The influence of the thermal self-interaction of the laser radiation in the first pass through a Faraday isolator on the power losses in the main spatiopolarisation mode is analysed. Analytical expressions for these losses were obtained for different designs of the isolators. It is shown that the design with two 22.5° Faraday rotators and with a 67.5° reciprocal rotator between the former devices is best from the standpoint of all the isolator parameters. The results obtained for a Gaussian beam were extended to the case of super-Gaussian and Π-shaped (step-like) beams. It was established that the Π-shaped beam exhibits a minimal self-interaction.