Magneto-optical Faraday effect of discontinuous magnetic media with a one-dimensional array structure

Abstract

To elucidate unique Faraday spectra observed in porous magnetic films, we theoretically analyzed the magneto-optical Faraday effect of discontinuous media with an ideal one-dimensional array structure. The media are constituted by magnetic materials (width DM) and air gaps (width DG) which are aligned interchangingly. Propagation properties of optical waves in the media, such as the dispersion characteristics and the polarization states, were explored circumstantially, and apparent Faraday rotation and ellipticity spectra of the discontinuous media were obtained. The analysis reveals that the apparent Faraday spectra of the media vary to a large extent from those of a continuous medium depending strongly on the media structures. The key factors which govern the magneto-optical effect of the discontinuous media are structural elements of DM and 2(DM+DG): The Faraday spectra are subject to change only when DM<λ (λ: the wavelength of optical wave in a vacuum). Then, the magneto-optical effect of the magnetic materials is related to mode conversion from TE to TM when 2(DM+DG)<λ. If DM<λ<2(DM+DG), the mode conversions of both directions from TM to TE and TE to TM are possible. The mode conversion dominates the apparent Faraday spectra of the media, causing the enhancement in the Faraday rotation and systematic shift of the spectra toward shorter and/or longer wavelength of the optical waves. These results explain very well the unique Faraday spectra of the porous films.