Periodic Near-field Enhancement on Metal-Dielectric Interfacial Gratings at Optimized Azimuthal Orientation

The effect of plasmon-wavelength scaled gratings on the surface plasmon resonance is studied experimentally and theoretically. The model samples are multi-layers containing laserfabricated gratings at bimetal-polymer interfaces. Dual-angle dependent surface plasmon resonance measurements are performed illuminating the samples by monochromatic light in Kretschmann arrangement. The double-peaked resonance curves show that it is possible to maximize the grating-coupling efficiency by the appropriate azimuthal orientation of the grooves. The dual-angle dependent reflection problem on three dimensional periodic structures is solved by RF module of COMSOL. The numerical calculations prove that the grating-coupling phenomenon is accompanied by periodic nearfield enhancement at the metal-dielectric interfaces. The airand glass-side plasmons are synchronized along the valleys at the optimal azimuthal orientation. The synchronization possibility of the periodic plasmon-field and adhesion enhancement is an important tool to improve the sensitivity in bio-sensing based on the monitoring of the secondary peaks appeared due to rotated grating-coupling phenomenon.