Equivalence relations for the enhanced polar Kerr effect at normal incidence

An enhancement of the polar Kerr effect in the magneto-optical (MO) readout system is achieved by specific dielectric thin-film coatings. The MO mediu m of refractive index a and MO constant q, overcoated by a dielectric thin film, is equivalent in normal reflection to an uncoated MO medium of parame ters N and Q. Following this reasoning we present simple relations for equi valent parameters N and Q of different systems. Behaviour of parameters N a nd Q is illustrated by numerical examples. The use of equivalent parameters allows an easier comparison among different MO systems.