Unexpected large transverse magneto-optic Kerr effect at quasi-normal incidence in magnetoplasmonic crystals

We investigate the transverse magneto-optic Kerr effect (TMOKE) of magnetoplasmonic crystals grown on top of commercial optical disks. From full angle-resolved scans we can identify Wood’s anomalies related to the excitation of plasmons of different orders. From these maps we also detect a wide range of wavelengths and angles of incidence for which the TMOKE signal is increased due to the interaction of light with surface propagating plasmons. Remarkably, conditions are established for unexpectedly large responses at quasi-normal incidence, where, by fundamental symmetry reasons, the intrinsic TMOKE should be vanishingly small. The key towards this unexpected outcome is to engineer the geometry of magnetoplasmonic crystals, so that first-order plasmon dispersion lines run up towards quasi-normal angles of incidence. These results provide general rules for magneto-optic enhancement and, in particular, show the potential of standard commercial disks as platforms for enhanced magneto-optic devices.This work was supported by the Spanish MAT2017-85232-R (AEI/FEDER, UE), MAT2014-56063-C2-1-R, Severo Ochoa SEV-2015-0496 grant, the Generalitat de Catalunya (2017 SGR 1377). M.A.O. acknowledges financial support from the Ministry of Science, Research and Technology of Iran. R.C acknowledges support from CNPq Brazil.Peer reviewe