Multilayered optical memory with bits stored as refractive index change. III. Numerical results of a conventional multilayered optical memory
ABSTRACT In terms of the electromagnetic theories described in Part I of our current investigations [J. Opt. Soc. Am. A24, 1776 (2007)] and in [Opt. Express 16, 2797 (2008)], the characteristics of the cross talk and the modulation contrast and the variation of the power of the readout signals with the scanning position along the track are investigated in detail by computer simulations for a conventional multilayered optical memory (CMOM), where the two cases, i.e., the storage medium being homogenous and planar stratified homogenous, are considered. Results show that the feature sizes of bits, the distances between the two adjacent tracks, and the thickness of layers have significant effects on the cross talk and the modulation contrast. The polarization of the reading light also has significant effects on the cross talk, whereas it has only slight effects on the modulation contrast. Moreover, for a CMOM, the optimal polarization of the reading light is suggested.
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ABSTRACT: Rigorous two-dimensional vector-diffraction patterns of a focused beam incident on an optical disk, specifically, a digital versatile disk (DVD), are examined both in the near field and in the far field. An efficient finite-difference frequency-domain method is developed for calculating the electromagnetic fields in the neighborhood of subwavelength dielectric and metallic structures. The results of vector-diffraction theory are compared with those of scalar-diffraction theory for pressed DVD features that consist of pits or of bumps. The sum (data) and difference (tracking) signals from a split photodetector are also calculated for different disk features and for different polarizations. The subwavelength features of a DVD result in considerable vector-diffraction effects both in the near-field profiles and in the detector signals, depending not only on the polarization of illumination but also on whether the features are pits or bumps. This paper provides important insight into the vector-diffraction effects encountered in high-density optical data storage systems.Applied Optics 07/1999; 38(17):3787-97. DOI:10.1364/AO.38.003787 · 1.78 Impact Factor
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ABSTRACT: A full and rigorous vector diffraction model for a multilayered optical disc is described where three vector diffraction processes, namely the focus of the reading light, the interaction with bits and the detection part, are all considered. Moreover, the reflected electric fields resulting from the infinite number of bounces at the multilayered optical disc are also involved. As an example, the detected power is calculated when the reading spot is scanned over the disc under the case of the circularly polarized illumination.Optics Express 03/2008; 16(4):2797-803. DOI:10.1364/OE.16.002797 · 3.53 Impact Factor
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ABSTRACT: The optical disk readout signals from ROM disks are presented by use of a rigorous three-dimensional vector diffraction method. The optical disk is modeled as a crossed metal grating without restriction on the form of the information marks, and the permittivity of the metal is taken into account. The diffracted field from the disk is obtained by means of decomposing the focused incident beam into a spectrum of plane waves and then calculating the diffracted plane waves for each respective incident component. The readout signal is obtained by integration of the energy-flux density of the diffracted field according to the detection scheme of the optical disk system. A typical digital versatile disk (DVD) system is applied with this theory, and the result is far from that of scalar diffraction theory.Applied Optics 01/2001; 39(34):6436-40. DOI:10.1364/AO.39.006436 · 1.78 Impact Factor