Optical isolators based on magnetoplasmonic subwavelength gratings

Optical isolators are one-way devices allowing light to pass only in one direction. They are elementary components to protect laser diodes against spurious back reflections or to build functions like optical circulators. Here we propose a metal-dielectric non-reciprocal waveguide that may pave the way toward the conception of compact integrated isolators. The challenge is to design integrated optical isolator with low footprint, high isolation ratio and low insertion losses. Fig. 1(a) depicts a 3D sketch of the proposed structure which includes a one dimensional (1D) subwavelength periodic gold plasmonic grating. The latter is located on one side of a magneto-optical (MO) dielectric Bismuth Iron Garnet (BIG) waveguide. These elements are placed on top of a non-MO Gallium Gadolinium Garnet (GGG) substrate and buried in SiO2 superstrate. In this configuration nonreciprocal transmission of the TE fundamental mode is obtained by applying a vertical static magnetic field (inducing vertical magnetization in BIG layer).