Surface modes enhanced magneto-optical Kerr effect in Fe films underneath two-dimensional array of polystyrene spheres

For bilayers consisting of 20 nm Fe film and top two-dimensional arrays of hexagonal close-packed polystyrene spheres, fine structures are observed in the reflection R and magneto-optical polar Kerr rotation θK spectra. The θK achieves narrow peaks or dips near R minima and are both shifted with the sphere diameter. All phenomena are attributed to the excited guided waves and surface plasmonic modes. The θK peaks and dips near the R minima can be mainly explained as a result of the pure optical constant effect.