Three‐dimensional FDTD analysis of light scattering from a phase‐change optical disk structure

Abstract

AbstractIn this article, we discuss simulations of the scattering characteristics of models of a phase‐change optical disk illuminated by a laser beam, using the three‐dimensional finite‐difference time domain (FDTD) method. We first analyzed a three‐dimensional conducting pit and a rewritable optical disk model, using the boundary element method (BEM) together with FDTD code that we wrote, and demonstrated that the results of using these two methods are in satisfactory agreement. Next, based on a four‐layer three‐dimensional structural model of a phase‐change optical disk, we investigated visualization images of the near‐field distribution, including the recording layer, as well as examples of far‐field scattering patterns calculated in the planes perpendicular and parallel to the guide groove, in order to determine how these patterns change before and after recording. We then made visualizations of the intensity distribution of light focused by the objective lens, and investigated how the regenerated sum and tracking error signal characteristics differ before and after recording. Finally, for the case in which the optical spot tracks without leaving the guiding groove, we can identify when the spot is in the space between adjacent recording marks. We conclude that a comparative analysis of light scattering by a complicated multilayer optical disk structure can easily be carried out by the 3D FDTD analysis discussed in this article. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(9): 56–66, 2001