Circular Displacement Current induced Novel Magneto-Optical Effects in All-dielectric Metasurfaces

Abstract

In recent years, various methods have been reported to boost the magneto-optical (MO) response. Several works have reported the enhancements of the MO response relying on the plasmonic effects attributed to the strongly confined electromagnetic field in the structures1-3. However, the nonnegligible disadvantage of this approach is the optical losses due to the high absorption coefficient of the metal materials1. Therefore, combining the all-dielectric metasurfaces which have high-refractive-index and low intrinsic loss with planar photonic structures offers an alternative route to these problems4,5 .But most of the observations so far are focused on enhancement of existing magneto-optical effects in planar MO thin films. A high index contrast, all dielectric magneto-optical metasurface featuring strong Mie resonance modes have not been fabricated. Here, we report observation of circular displacement current induced novel magneto-optical effects in a high index contrast Si/Ce:YIG/YIG/SiO2 all dielectric metasurface. We observe giant transverse magneto-optical Kerr effect (TMOKE) up to 7 % under s-polarized incidence, which is non-existent in planar magneto-optical thin films. This phenomenon is essentially originated from the unique circular displacement current when exciting the magnetic resonance modes, which changes the incident electric field direction locally. These results indicate promising potential of controlling light propagation by utilizing the complex Mie resonance modes in magneto-optical all dielectric metasurfaces. Our work may inspire the development of novel magneto-nanophotonic devices such as vectoral magnetic field sensing, free space non-reciprocal photonic devices and magneto-optical imaging.  Figure 1. (a) Schematic diagram of the metasurface. (b) Scanning electron microscope image of a fabricated device.  Figure 2. (a) Schematic diagram of s-polarized TMOKE characterization set-up. (b)Measured s-polarized TMOKE and reflection spectra of the metasurface compared with bare Ce:YIG/YIG thin films. (c) Measured TMOKE hysteresis for the metasurface and the bare MO films at 1230 nm wavelength. (d) Simulated reflection spectra and TMOKE responses of the metasurface for s-polarized light.