Study of optical properties of multilayer nano thin film by finite-difference time-domain method and Fourier optics approach

Near-field optical disk structure has been an attractive topic in ultrahigh density optical data storage. Evanescent signals of subwavelength recording marks can be retrieved from optical interactions between reading laser beam and near-field active layer in near-field optical disk. In this dissertation, we use the 2-D finite-difference time-domain method (FDTD) and Fourier optics approach to study the mechanism of near-field optical disk. Near-field optical properties and far-field responses of near-field optical disks with various kinds of nanostructrures are studied by FDTD. Results show that evanescent signals of subwavelength recording marks are coupled to propagating waves by nanostructures. Furthermore, a simplified Fourier optical approach is used to study the influence of random nanostructure in near-field active layer. The general properties of near-field optical disk with random nanostructure are analyzed by statistical average. The readout contrast signal and waveform of near-field optical disk with random nano apertures is derived. Results show that resolution of near-field optical disk is influenced by the size of aperture.