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 spat iopolarisation mode is analysed. Analytical expressions for these losses we re obtained for different designs of the isolators. It is shown that the de sign with two 22.5 degrees Faraday rotators and with a 67.5 degrees recipro cal rotator between the former devices is best from the standpoint of all t he isolator parameters. The results obtained for a Gaussian beam were exten ded to the case of super-Gaussian and Pi-shaped (step-like) beams. It was e stablished that the Pi-shaped beam exhibits a minimal self-interaction.