The Magneto-Optical Photonic Crystal Optical Isolator

Optical isolator is an important part in the optical system, which is low-loss transmission in the forward direction and shows very high optical transmission loss in the backward direction. With the rapid development of integrated optics, the traditional large-scale isolation can not be integrated in the micro-nano scale, so the demand for integrated optical isolators increasingly urgently. Once, there was one kind of one-dimensional magneto-optical photonic crystal isolator based on Faraday Effect, and which was experimentally confirmed that the reverse light was isolated effectively. However, this structure required optical isolators are integrated polarizers on both sides of isolator, which limited the use of this isolator.This article is based on another magneto-optical effect, when the propagation direction of the incident wave is perpendicular to the magnetization direction, which will induce in the magneto-optical Voigt Effect. For the Voigt effect, we establish one kind of magneto-optical photonic crystal of binary and ternary structure. In the edge of the magneto-optical photonic crystal band, the nonreciprocal effect reaches the maximum. Then we make a magneto-optical isolator depending on the nonreciprocal shift phase region. We also study the effect of the incident angle, the film thickness, the non-uniform magnetization and the magneto-optical material parameter on the optical isolators.Because the optical isolators which base on the band edge require a huge thickness, so the actual production is more difficult. Therefore a kind of magneto-optical isolator based on defect model was proposed. A single MO layer is bounded by two non-identical non-magnetic Bragg mirrors. Due to the non-reciprocal effect. There is a frequency gap between transmission peaks for waves propagating in opposite directions, which can achieve isolation. However the incident angle, the film thickness of the Bragg mirrors and the magneto-optical material parameter also affect the performance of the optical isolators. At the same time, we design another isolator with a low refractive index medium as the defect, the Bragg mirrors on both sides of the defect are consisted of the general dielectric layers alternating with a magnetic material layers. In addition, the Bragg mirrors on both sides of the defect are also asymmetrical. This structure of the low refractive index defect manifests very high transmission peaks in the low angles, which can be made a superior performance optical isolator.