Development of optical grade (TbxY1-x)3Al5O12 ceramics as Faraday rotator material

Super full dense (TbxY1-x)(3)Al5O12 (x=0.5-1.0) ceramics with optical grade (pore-free) were successfully produced by solid-state reaction between Tb4O7 and Al2O3 raw powders. Transparent sintered bodies were obtained by sintering at 1720 degrees C for 5hours in vacuum furnace. By additional HIP treatment, optical scattering centers were effectively removed, and finally the optical quality of the sintered bodies was improved to optical grade. Optical loss of the obtained samples at 1064nm was approximately 0.1%/cm, and optically inhomogeneous parts were not observed inside the materials. Gaussian mode laser beam quality was not deteriorated after passing through the sample. Transmitted wavefront distortion inspected by interferometry was as excellent as /12. Verdet constant increased with an increase of Tb content in the garnet composition. When x=1.0, the Verdet constant was 307, 196, and 60radT(-1)m(-1) for 532, 633, and 1064nm, respectively, at each measuring wavelength. These values were about 1.5 times higher than that of the commercially available TGG (Tb3Ga3O12) crystal. Insertion loss of the produced (Tb0.6Y0.4)(3)Al5O12 and TAG ceramics at 1064nm was 0.01 and 0.05dB, respectively, and extinction ratio was 39.5 and 40.3dB, respectively. These properties were superior to that of the commercial high-quality TGG single crystal (insertion loss: 0.05dB, extinction ratio: 35.0dB).