Mark formation modeling in optical rewritable recording

Mark formation modeling in optical rewritable recording

Brusche, J.H.
Segal, A.
Vuik, C.
Urbach, H.P.

2006-09-07

In optical rewritable recording media, such as the Blu-ray Disc, amorphous marks are formed on a crystalline background of a phase-change layer, by means of short, high power laser pulses. In order to improve this data storage concept, it is of great importance to understand the mark formation process. Therefore, a rigorous numerical model is developed to study the influence of for instance the polarization of the incident laser light or the geometry and configuration of the recording stack on the size and shape of the mark. The mark formation process can be divided into three stages: the melting of the crystalline background, rapid solidification of the molten region and amorphization. The focus of this study is on the melting stage. In contrast to earlier work [1], the contribution of latent heat is taken into account in the computation of the temperature distribution in the optical recording disk. The corresponding three dimensional Stefan problem is numerically resolved using an adapted version of the discontinuous integration technique as described by for instance Fachinotti et al. [2]. Latent heat is incorporated as an added non-linear term to the heat conduction equation. Besides the inherent non-linear character of the considered partial differential equation, several other numerical challenges arise from the practical background of the problem: the phase-change layer forms an integral part a recording stack, consisting of various layers with possibly large jumps in physical parameters. In addition, there are variations in the geometry (i.e. grooved tracks). This makes that a finite element discretization is preferred. Finally, the accurate capturing of the free interface between the liquid and solid state requires high resolution meshes. In order to reduce computational load, an adaptive local mesh refinement code has been implemented.

Stefan problem
enthalpy method
temperature method
optical rewritable recording

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Conference proceedings

conference paper

(c) 2006 Brusche, J.H.; Segal, A.; Vuik, C.; Urbach, H.P.