Innovative improvements in bismuth-doped rare-earth iron garnet Faraday rotators

Performance of magneto-optic isolators is often limited by the properties of the Faraday rotator, which can be improved. (1) A compensation point layer can be used to control the temperature dependence of the material and consequently improve the extinction ratio to ⩾30 dB from -10°C to 85°C without significant increase in device size or complexity. (2) Variation of composition and lattice parameter can decrease the material absorption and therefore the device insertion loss at specific wavelengths. (3) Development of a “latching” Faraday rotator material with an effective coercivity above 1 kOe allows the design of devices with no bias magnet and consequently lower cost and size