Integrated Magneto-Optical Devices for On-Chip Photonic Systems

Development of magneto-optical (MO) materials could lead to a range of nonreciprocal optical devices for emerging standardized photonic integrated circuit (PIC) fabrication processes.

Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio

The magneto-optical (MO) oxide layer consists of (Bi,Y)₃Fe₅O₁₂ or BiYIG, bismuth garnet. This material was selected because it has a better figure of merit than the CeYIG previously used, especially at lower wavelengths (1310 nm vs. 1550 nm). A top-down deposition process was developed in which BiYIG/YIG stacks are grown on the Si waveguide with YIG on top. The stack is annealed at 800°C/5 min to crystallize both layers, with the YIG templating the BiYIG leading to garnet phases rather than other oxides, and the BiYIG is directly on the Si waveguide. Initial attempts led to a film with Bi oxide phases, because the Bi was in excess and could not escape during the anneal as occurs in Si/YIG/BiYIG stacks. Hence the composition was adjusted to include slightly more Fe, which yielded films with only garnet peaks.

Conditions were also developed for growth of Bi-substituted iron garnet (BiYIG) on GGG garnet and Si substrates by combinatorial pulsed laser deposition.