Modulation of surface plasmon resonance by magnetization reversal in Au/Fe/Au trilayer and wedge structure for achieving higher refractive index sensitivity

We report enhancement of the transverse magneto-optic Kerr effect (TMOKE) in Au/Fe/Au trilayers for improving the refractive index (RI) sensitivity in surface plasmon resonance sensors by magnetic modulation. The thicknesses of the upper Au layer, the Fe layer and the lower Au layer with required thickness resolution were theoretically optimized to maximize the TMOKE intensity with perfect momentum matching, and 3% TMOKE intensity was obtained in a trilayer. Furthermore, a wedge-shaped Au thin film was fabricated on a glass substrate, and the incident angle showing minimum reflectivity was modulated, corresponding to a difference in momentum matching. Resolution of the metal layer thickness (0.26 nm) was demonstrated in a single sensor chip for maximizing the TMOKE intensity. Enhanced RI resolution is expected in sensor chips formed of a Au/Fe/wedge Au trilayer, which will contribute to improvements in the limit of detection when measuring the analytes by analyzing the resulting signals. (author)