The rotation of the polarization of light by magneto-optical materials is well exploited by macroscale devices such as optical isolators, however, demonstrations in nano-optics or plasmonics are lacking due to issues such as dissipation and phasematching. Now, Curtis Firby and colleagues from Canada have proposed an integrated magnetoplasmonic Faraday rotator. They predict 99.4% polarization conversion over an 830-μm-long device using low-loss modes that can propagate over a distance of 1 mm. The proposed structure, designed for 1,550 nm wavelength operation, is a 450-nm-wide ridge waveguide with multilayers stacked vertically within. A 25-nm-thick silver layer is surrounded by two 20-nm-thick SiO2 layers. A highindex ‘hat’ for the ridge is formed by a 725-nm-thick layer of TiO2 while the bottom high-index ridge region is a 320-nm-thick Bi:YIG rib on top of a 260-nm-thick Bi:YIG platform. The team designed the waveguide structure such that transverse electric and transverse magnetic modes are phase matched and low-loss but with sufficient mode overlap in the Bi:YIG medium to cause the polarization rotation. The design could lead to miniature integrated circuitry that is capable of modulating polarization at speeds as fast as 10 GHz.
ACS Photon. http://doi.org/bvg4 (2016)