Horizontal aluminum magneto-plasmonic metasurface for efficient magneto-optical Kerr modulation and sensing in the ultraviolet range

Most of the plasmonic nanostructures utilized for magneto-optical (MO) enhancement have been limited to noble metals with resulting enhancement in the visible and infrared spectral range. Here, we designed a horizontal aluminum magneto-plasmonic metasurface, with the ability to control the Kerr rotation angle and enhance the RI sensing performance based on magneto-plasmons, by exploiting the polarization degree of freedom in the ultraviolet range. The surface composes of L-shaped magnetic dielectric embedded in the Al film. The reflection spectrum and the Kerr rotation angle map are both symmetric about the polarization angle of 45° and 135°. It is demonstrated that the sign change of the two maximal Kerr rotation angles at polarization angle of 0° and 90°, originates from the relative contribution of the two mutually orthogonal oscillating electric dipoles. In addition, the RI sensing FoM based on Kerr reversal at 372 nm of this structure reaches 5000/RIU, which is superior to the result in the visible or infrared range (1735/RIU). The results of our investigation demonstrate the potential of Al-based magneto-plasmonic effect and offer opportunities to push the MO spectral response out of the visible range into the ultraviolet range.