Faraday isolators with low heat release are created for high average power lasers. The heat release is reduced either by
shortening the optical element (due to cooling to nitrogen temperatures or use of superconducting solenoids) or by
employing non-traditional magneto-optical media with better thermo-optical properties. It is shown that the suggested
ways make it possible to create a Faraday isolator for 100kW average power.
It is experimentally demonstrated that cooling Faraday isolators to liquid nitrogen temperature considerably decreases thermally induced depolarization and thermal lens. This allows a 30 times increase in maximum average power of laser radiation going through the isolator at the same isolation ratio. It is shown that traditional Faraday isolators under such cooling conditions can operate at powers up to 10 kW, and Faraday isolators with compensation of depolarization and thermal lens - at powers up to 100 kW.