Unidirectional-propagating surface magnetoplasmon based on remanence and its application for subwavelength isolators

Ferrimagnetic material with remanence holds the potential to realize unidirectional propagation of the electromagnetic field by taking advantage of magnetoplasmon in the subwavelength regime. Here, we theoretically investigate magnetoplasmons in a layered structure consisting of a dielectric sandwiched by two magnetic materials with anti-parallel remanent magnetization directions, which shows a complete unidirectional propagating region for both even and odd symmetry modes when the thickness of the dielectric is smaller than a certain value. Additionally, the even symmetry mode supported by such a one-way waveguide can be effectively, with low insertion loss, excited by the fundamental transverse-electric mode of a traditional metal slab waveguide. Relying on low insertion loss and a one-way propagation feature, we propose a broadband and subwavelength isolator working at the microwave region. Our results demonstrate that remanence based magnetoplasmons provide a promising way to realize devices below the diffraction limit with new functionalities.