Flat-top response in one-dimensional magnetic photonic bandgapstructures with Faraday rotation enhancement

The transmission and Faraday rotation characteristics of one-dimensional photonic crystals in cerium-substituted yttrium iron garnet (Ce:YIG) with multiple defects in the optical bandgap are studied theoretically at λ = 1.55 μm. It is found that the interdefect spacing can be adjusted to yield a flat top response, with close to 100% transmission and 45° Faraday rotation, for film structures as thin as 30 to 35 μm. This is better than a three-fold reduction in thickness compared to the best Ce:YIG films for comparable rotations, and may allow a considerable reduction in size in manufactured optical isolators. Transmission bands as wide as 7 nm are predicted, which constitutes a considerable improvement over previously reported bandwidths for magnetic photonic crystals. Diffraction across the structure corresponds to a longer optical path length than the thickness of the film, calling for the use of guided optics to minimize insertion losses in integrated devices. The basis for the flat-top transmission in ferrite photonic crystals is presented and discussed