Bi-Directional Faraday Rotation Selective Enhancement on Embedded Nano-Gratings

The magneto-optic rotation enhanced by plamonic resonance brought a new method in the research of magnetoplasmon and magneto-optical devices. To further the availability of this method, the Faraday effect on embedded nano-gratings with Bi-substituted yttrium iron garnet substrate is investigated here to achieve bi-directional rotation enhancement selectively. The surface of the simulation structure is designed as 1-D gratings to excite extraordinary optical transmission, and the transmitted light is rotated in the magneto-optic (MO) material. It is found that the characteristic of the bi-directional Faraday rotation enhancement can be greatly influenced by the embedding depth of the metal strips in the MO material. According to this, without changing the applied magnetic field or turning over the MO material, the selectively enhanced Faraday rotation is produced along two opposite directions. Moreover, by optimizing the thickness of metal, a great improvement of figure of merit is obtained. Finally, in the same wavelength regime, the properties of the structure are contrasted when the metal is set to be gold or silver, respectively. This letter provides a useful thought in magnetoplasmon studies, and can be used to fabricate many magneto-optical devices.