Strong Faraday Rotation Based on Localized Surface Plasmon Enhancement of Embedded Metallic Nanoparticles in Glass

The Faraday rotation originates from the mechanism by which the time-reversal symmetry in the material is broken by the external magnetic field. It is the basis for the development of some magneto-optical devices, such as optical isolators. In integrated optics and telecommunications, nonreciprocal photonic devices with high transmittance and strong Faraday rotation are desired for low-cost, compact optical systems. Localized surface plasmon resonance (LSPR) from the metallic nanoparticles in dielectrics allows the light localization in subwavelength scales, boosting the interaction between nanoparticles and materials, which results in a number of plasmon-enhanced effects. Herein, the strong Faraday rotation in BK7 glass by embedded metallic nanoparticles through LSPR is reported. It is elucidated that the mechanism of Faraday rotation is the near-field enhancement of spin-photon coupling effect in the presence of an external magnetic field. The Verdet constant of the thin-layer BK7 glass with embedded Au nanoparticles is determined as high as 5059.7 rad T^-1 m^-1 at 532 nm, exhibiting excellent magneto-optical features. This work opens a new avenue to develop the subwavelength magneto-optical devices with embedded metallic nanoparticles.