Anomalous Switching of Giant Magnetoplasmonic Transverse Kerr Effect

概要

論文の詳細を見る
It was recently proven by Belotelov et al. [J. Opt. Soc. Am. B 26, 1594 (2009)] how the magneto-optical (MO) transverse Kerr effect gets strongly enhanced when a smooth magnetic dielectric film is covered with a thin noble metal layer perforated with subwavelength slit arrays. This was attributed to the non-reciprocal influence of the MO substrate on the plasmon resonances of the noble metal grating. Here we extend on this work by studying how the thickness of the grating influences these extraordinary transmission effects and a surprising behavior is observed. At small gold thickness the strong enhancement at the Wood-plasmon anomalies is observed, as predicted before. The spectral position of these peaks is in accordance with the equation which is shown in the above mentioned paper. Surprisingly, when increasing the gold thickness the Kerr effect of the Wood anomalies is seen to weaken, disappear at a critical thickness (174 nm resp. 204 nm), and finally switch sign (all under fixed magnetization). We show that this behavior is caused by a critical coupling of the surface plasmons at the garnet-gold interface with grating air-slit cavity resonance modes.