Promising Materials for High Power Laser Isolators

Abstract Northrop Grumman Synoptics is developing the growth of large singlecrystal fluoride materials for Faraday rotator / isolator applications. These materials exhibit smaller nonlinear refractive index and thermo‐optic coefficients, while maintaining Verdet constants near those of the commonly used terbium gallium garnet (TGG) crystals. In particular, the cubic potassium terbium fluoride, KTF (KTb 3 F 10 ) crystal has low absorption and thermo‐optic coefficients. The crystal growth and performance of these single‐crystal fluoride materials will be discussed as well as recent improvements to the performance of TGG crystals.