Optical properties and Faraday effects on terbium gallium garnet ceramics for Faraday rotator

High-average-power laser is widely used for material processing, development of lithography source and many scientific researches and so on. As there are so many applications of high power lasers, the demands for more powerful laser are growing rapidly. A Faraday element is one of the indispensable optical elements for isolation of laser amplifiers and birefringence compensation of laser materials in such two-pass high-power laser systems. The single crystal TGG(terbium gallium garnet) grown by the Czochralski method takes a long time to grow, and is difficult to make large-size crystals. Ceramic TGG [1, 2] are attractive for actual applications because of low fabrication cost in mass production and short fabrication time. The mechanical properties of ceramic are generally better than those of single crystal because the polycrystalline ceramics are aggregates of crystalline grains. External force is dissipated in ceramics because of random orientation of the grains. Therefore, the fracture toughness of ceramics TGG is larger than that of single crystal TGG. It is also expected that the thermal fracture limit of ceramic TGG is larger than that of single crystal.