Cyclotron frequency coupled enhancement of Kerr rotation in low refractive index-dielectric/magneto-optic bilayer thin-film structures

We investigate the enhancement of magneto-optic polar Kerr rotation over a broad range of optical frequencies. The Drude model for the dielectric tensor is considered. Resonance-like peaks in the Kerr rotation and ellipticity caused in the vicinity of a plasma edge is extended throughout the visible spectrum by deriving an expression for the cyclotron frequency such that Re(ϵxx)∼1 at any given incident photon energy and plasma frequency of the material. The Kerr rotation obtained by use of this expression was studied for the case of InSb and further enhancement of Kerr rotation was achieved in the case of LiF/InSb bilayer thin-film structure, grown on a glass substrate. The numerical analysis was carried out using a 2×2 characteristic matrix, which takes into account multiple reflections and interface effects within the medium. In addition the role of various magneto-optic material parameters and layer thicknesses is investigated in determining the optical frequency at which the maximum Kerr rotation occurs, under the present cyclotron frequency condition. Enhanced Kerr rotation greater than 1.5° over a broad range of optical frequencies was obtained. Tables showing optimum figure of merit for repeated LiF/InSb bilayers at 3.1 eV for different plasma frequencies are also provided