Three-dimensional analysis of light-beam scattering from magneto-optical disk structure by FDTD method

The rewritable magneto-optical (MO) disk consists of a thin magnetized layer, where the information is recorded by a series of anti-magnetized record mark domains. Because this anisotropic dielectric layer causes a change of polarization direction in the reflected light which corresponds to the direction of magnetization, the information is reconstructed by detecting the polarization direction of the scattering light-beam. Although many articles on the theoretical studies of light-beam scattering from the read only type optical disk structure have been reported, articles on the numerical analysis of the magneto-optic disk structure is very few. A three dimensional FDTD method is developed to analyze the scattering of a light-beam from an anisotropic dielectric structure. First, the scattering pattern of the light-beam from a pregroove on a MO disk is calculated. The result is compared with that of the boundary element method to show the validity of the FDTD calculation. Then, the polarization characteristics of scattering light-beam from an anti-magnetized record mark on a MO disk is shown by numerical results.