Waveguide type optical isolator using faraday and cotton-mouton effects in Bi-substituted YIG thin films

Propagation and mode conversion properties of optical waves in film waveguides made of magneto-optic materials such as garnet crystals are studied in order to construct optical thin film isolators using magneto-optic effects. Gyrotropic YIG films are fabricated on GGG crystal substrates by RF sputtering method. Faraday effects in gyrotropic film waveguides are investigated for non-reciprocal guide parts of optical film devices. Magneto-optic Cotton-Mouton effects are also studied for reciprocal parts of optical devices. Birefringence effects in sputtered garnet films that are very useful for mode matching are found. By using ferrite magnets for external magnetic fields thin film type optical isolators of total lengths of 3.3 - 4.6 mm, consisting of Bi-substituted YIG films, are constructed. Isolation ratio of the isolator for forward and backward optical waves is 7.5 dB.