OPTICAL MAGNETOSTATIC WAVE COUPLED-MODE INTERACTIONS IN GARNET HETEROSTRUCTURES

Optical-magnetostatic wave coupling is considered theoretically in a five-layer structure consisting of three thin films, a cover, and a substrate. Two of the thin films are magnetic and are optimized separately for microwave and optical properties. The optical mode analysis permits the layers to be anisotropic provided the permittivity tensor is diagonal in the problem coordinate system. The magnetooptical properties are then treated as a perturbation. Both Faraday and Cotton-Mouton effects are included. Coupled-mode theory is then applied to the optical modes in the geometry for the general case of non-collinear propagation. Examples are presented showing that 100% conversion lengths of the order of 1 cm at both 1.152 and 1.32-mu-m should be possible in low-loss films even though the optical and microwave guiding layers are distinct. This is a result of an enhancement of the magnetooptical coupling made possible by the use of a multilayered structure. The extra degrees of freedom provided by two magnetic films make it possible to adjust the microwave parameters so that the operating point is near the susceptibility resonance of the optical guiding layer thereby enhancing the magnetic response of this layer. The effects of magnetic damping are expected to be significant under these conditions, however, and should be the subject of future investigations.