Total Performance of Magneto-Optical Ceramics with a Bixbyite Structure

High-quality magneto-optical ceramics (Tb Y )₂O₃ ( = 0.5⁻1.0) with a Bixbyite structure were extensively investigated for the first time. The total performances of these ceramics were far superior to those of commercial TGG (Tb₃Ga₅O ) crystal, which is regarded as the highest class of Faraday rotator material. In particular, the Verdet constant of Tb₂O₃ (when = 1.0) ceramic was the largest-495 to 154 rad·T ·m in the wavelength range of 633 to 1064 nm, respectively. It was possible to further minimize the Faraday isolator device. The insertion loss of this ceramic was equivalent to that of the commercial TGG single crystal (0.04 dB), and its extinction ratio reached more than 42 dB, which is higher than the value for TGG crystal (35 dB). The thermal lens effect (1/f) was as small as 0.40 m as measured by a 50 W fiber laser. The laser damage threshold of this ceramic was 18 J/cm², which is 1.8 times larger than that of TGG, and it was not damaged during a power handling test using a pulsed laser (pulse width 50 ps, power density 78 MW/cm²) irradiated at 2 MHz for 7000 h.