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Magneto-optic elements are important in applications requiring frequency shifters. Certain
applications require the incorporation of magneto-optic layers into a multilayer optical stack.
This paper is concerned with the development of design methodology for maximizing magnetooptical
effects. To aid in this developmental process, the well-known concept of thin film
Herpin equivalent structures is extended into magneto-optics; specifically, the magneto-
optical analog of Herpin equivalents is derived for a thin magneto-optic layer sandwiched
between a symmetric pair of dielectric films.
The magneto-optic configuration selected is that of the Transverse Kerr effect; that is, the
magneto-optic layer magnetization lies in the plane of the film and is in a direction perpendicular
to the plane of incidence. For this geometry, magneto-optic effects manifest themselves
only for the p (in-plane) polarization. As part of the derivation process, reflectance and
transmittance expressions are derived for a symmetric three-element film configuration. It is
shown that the magneto-optic effects only manifest themselves in reflection; in other words,
the transmitted electric field does not contain a magnetization dependent term.
Additionally, as the direction of propagation of the light wave is reversed (with the electric
field incident on the three layer structure from the back surface), the magneto-optic signal
changes sign, indicating non-reciprocity of the coupling between the light waves and thin film
magnetization. It is also shown that the magnitude of magneto-optic effects depends only
on three terms: (a) the reduced magneto-optic coefficient of thin film material; (b) the phase
thickness of the magneto-optic layer; and (c) the transmittance of the three layer structure.
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