Magneto-optical properties of potassium terbium fluoride

High power laser systems require optical isolators to avoid feedback into the pump laser cavity. To date, most of these devices have been based on the inverse Faraday effect in which the plane of polarization of the pump beam is rotated nonreciprocally in response to a magnetic field to prevent reflected light coupling back into the pump laser. Recently, new materials have been developed which have large Verdet coefficients and are able to withstand high optical power. We report measurements of the Verdet coefficient of potassium terbium fluoride and propose a design for an isolator based on this material.