Enhancement of transverse magneto-optical Kerr effect based on surface plasmon and its application in sensing

In recent years, the combination of magnetic and plasma properties of nanostructures has become a hot research topic. However, most such studies focuse on prism-based sandwich structures, which not only hinders device miniaturization but also has weak transverse magneto-optical Kerr (TMOKE) in amplitude. In this paper, a sub-wavelength periodic nanoporous Au/Co bilayer magneto-optical surface plasmon resonance (MOSPR) sensor is investigated, where the sensing principle is based on the measurement of TMOKE. By optimizing the geometric parameters of the nanostructure, a nearly perfect TMOKE spectrum with a FWHM of only 0.175 nm is obtained, which has a Fano-like pattern and an amplitude close to the theoretical maximum. It is proved that the excitation of high quality SPR enhances the magneto-optical effect. We then analyze the resonant angular shift associated with the TMOKE signal to monitor the change in the analyte refractive index, demonstrating the sensing sensitivity up to 220°RIU−1 and figure of merits (FOM) in excess of 103 in gas. The MOSPR system achieves higher resolution compared to the gold-based SPR system, yielding an order of magnitude higher FOM than the SPR system.