Kerr-resonance-condition-coupled enhancement in magneto-optic media

Abstract

We derive an expression for cyclotron frequency ωc, which sets Re[ε+ε−]=1 in a magneto-optic (MO) substrate, at any incident photon energy. Thereby, at any desired part of the optical spectrum, large Kerr effects can be obtained, which are generally known to occur either at the free-charge-carrier-plasma-resonance frequency ωp, or at frequencies where active electronic transitions take place. Under these conditions, ωp is seen to play a very different role; it is seen that for any ω, the magnitude of the Kerr resonance in a single MO (InSb here) substrate increases with decreasing ωp. With the objective of achieving further Kerr enhancement, the effect of coating a thin film of this ωc-coupled InSb layer on a Ag substrate is numerically studied. Further Kerr enhancement, at the plasma-resonance frequency of Ag, is seen, which is dependent on the thickness of the MO layer and its ωp. In this configuration, giant resonances appear in the effective-dielectric-tensor spectra. The spectral locations of these resonances are dependent on the thickness of the MO layer. We interpret these resonance structures to be the effective cyclotron resonance. Our results suggest that there exists a strong correlation between the effective-cyclotron frequency and the plasma-resonance frequency of the noble.