One-dimensional Magneto-photonic Crystal With Flat-top Responses For Optical Isolation

Under the action of magnetic field, one dimensional magneto-photonic crystals(1-D MPCs), incorporating a magnetic layer into a photonic crystal(PC), can improve the effect of Faraday optical rotation of magnetic-optical medium by exploiting properties of band gaps and defects of photonic crystals. Some studies have indicated the possibility of obtaining both large Faraday rotation angle and high transmittance using1-D MPCs. Generally, bulk magneto-optical material is being used as Faraday rotation material in the magneto-optical isolators(MOIs). However, in order to achieve the Faraday rotation angle of45°, the bulk magneto-optical material has commonly a length on the order of more than450μm. This induces a large size of the MOIs so that it is not suitable for the application in the integrated devices. The introduction of1-D MPCs film as Faraday rotation material can efficiently reduce the size of the MOIs.However, the existing MPCs inevitably suffer from narrow bandwidths, more layers, difficulty in manufactureor larger fluctuation of Faraday rotation angle in transmission bandwidth. That is, these1-D MPCs structures can work normally only at the central wavelength. Once encounter instabilities induced by wavelength or temperature fluctuations, they will lose effectiveness. More over, it is not conducive to the preparation of MOIs if the structure of1-D MPC is complex and the entire number of films is large.Based on the study of1-D MPCs mentioned above. After describing the4x4transfer matrix method for analyzing the properties of1-D MPCs, the main work and conclusion of this paper are as following:1. Choosing different materials, we investigate the optical isolation property of (H/L)n/M/(L/H)m/M/(H/L)m/M/(L/H)n and (H/L)n/M/(L/H)m/M/(H/L)n/M/(L/H)n/M/(H/L)m/M/(L/H)n, two1-D MPCs structures were found with large Faraday rotation angle and high transmittance. As for the first structure, with43layers, it can realize the optical isolation around0.95nm. The optical isolation range of the other structure reaches0.85nm with73layers, this structure having higher transmittance and better fluctuation than the first structure. Comparing to the available1-D MPC structures which can realize optical isolation around the central wavelength, both of these two structures having less layers. Integrable optical isolators can be accessed by using the two1-D MPC structures above instead of the bulk type magneto-optical materials in bulk type optical isolator in commerce.2. Based on the (H/L)n/M/(L/H)m/M7(H/L)n/M/(L/H)n/M/(H/L)m/M/(L/H)n, we choose different materials and investigate the optical isolation property of four composite structures. The first composite structure with83layers achieves flat-top width of3.5nm. The optical isolation range of the second composite structure reaches2.5nm with125layers, and this structure has higher transmittance and better fluctuation than the first composite structure. The third composite structure with125layers achieves flat-top width of4nm, and it has better fluctuation than the second composite structure. The last composite structure with115layers achieves a1nm-bandwidth optical isolation, and this structure ensures the achievement of optical isolation without adjusting the applied magnetic field.3. Analysising the mechanism of the broadband optical isolation property of linearly polarized light passing through the above mentioned composite1-D MPCs structures, this can be thought of as:the left and right hand circular polarizations show broadband optical isolation when passing through those1-D MPCs structures.