All-magneto-optical grating bio-sensors based on enhanced transverse magneto-optical Kerr effect

Abstract

Herein, a novel structure composed of an all-magneto-optical periodic grating, without using noble metals, is presented to enhance the transverse magneto-optical Kerr effect (TMOKE). This is done by calculating the relative changes in the reflection amplitudes for the p-polarized wave using the finite element method (FEM) with COMSOL Multiphysics. Bio-sensing applications of the proposed structure can be possible by detecting alternation in the refractive index of the analyte medium through monitoring of the TMOKE. The simultaneous operation of the magneto-optic layer as a sensing layer is the advantage of our idea, where direct interaction with the analyte happens, leading to the suppression of the wave reflection amplitudes, and finally leading to extreme TMOKE in a magneto-optical (MO) grating (the TMOKE amplitudes are near 0.8 in this work). And since TMOKE shows a Fano-like shape, we calculate sensitivity and figure of merit (FoM) by fitting them together. This results in high sensitivity, and the value of the FoM is remarkable (between 2×103 and 3×103 refractive index unit) at resonance angles for different refractive indices, which makes our proposed structure able to be utilized for bio-sensing applications.