Nonreciprocal Magneto-Plasmonic Waveguide with Compact Metal-Sandwiched Structure

A magneto-optical (MO) metal-sandwiched multilayered structure composed of metal, MO medium and dielectric buffer layers is presented and investigated by finite-element-method-based-mode solver and perturbation theory. The results show that this structure exhibits large nonreciprocal phase shift, strong mode confinement in the narrow buffer layers as well as very low propagation loss. The propagation length with 1 dB loss is much longer than the required length of π/2 nonreciprocal phase shifts in this structure. The modal area is smaller than half of the conventional MO waveguides. This phenomenon can be used to achieve a compact plasmonic isolator based on the Mach–Zehnder interferometer.