READING MAGNETO-OPTICAL (M-O) MEDIA WITH CIRCULARLY POLARIZED LIGHT
Original Publication Date: 1988-Jul-01
Included in the Prior Art Database: 2005-Feb-15
Circularly polarized light can be used to read magneto-optical (M-O) media. Consider the three-level M-O medium shown in Fig. 1. The bottom layer is a M-O active substance such as TbFe, but with a relatively high reflectivity (i.e., 84%). The top layer is a nonabsorbing dielectric or metallic coating with the same reflectivity as the bottom layer. The spacer is nonabsorbing. This structure has the reflection spectrum shown in Fig. 2, where the wavelengths of the minima depend on the thickness of the spacer. This type of medium is, in fact, a Fabry Perot interferometer used in reflection. The exact wavelengths of the minima depend on the phase shift encountered by a ray making a round trip around the cavity formed by the top and bottom reflectors.