Faraday isolator with compensation depolarization caused by Verdet constant temperature dependence

Thermally induced depolarization is known to be the principal factor limiting the usage of Faraday devices in laser radiation with high average power. In a number of practically important cases, the major contribution to the depolarization in Faraday devices is inhomogeneous Faraday rotation due to the temperature dependence of the Verdet constant. At the moment there are no satisfactory solutions to this problem. In this work a new scheme of a Faraday isolator with compensation of the contributions to thermally induced depolarization from the temperature dependence of the Verdet constant and thermally induced birefringence was proposed. The efficiency of using the proposed scheme and comparison with known schemes is analyzed analytically and numerically on an example of two magneto-optical crystals: TGG at cryogenic temperature and EuF2 in critical orientation at room temperature in which the contribution to thermally induced depolarization from non-uniform Faraday rotation due to the temperature dependence of the Verdet constant is major.