The integration of an optical and a thermal model for applications in optical recording

We consider optical disks consisting of several stacked layers, one of which is a recording layer which consists of a dye (for write once disks) or a phase-change material (for rewritable disks). Due to the illumination by a laser spot the temperature increases locally in the disk. The pulsing laser spot writes marks in the recording layer that represent the digitally encoded data. To guide the laser spot, the structure of the disks is grooved. Due to these grooves, the incident light of the spot is scattered. With the existing finite element program Cyclop, electromagnetic diffraction problems in two-dimensional periodic structures can be solved rigorously for three-dimensional incident fields, such as the laser spot used in optical recording. A three-dimensional finite element method code exists in Philips Research to simulate the heat diffusion during the recording. The optical and thermal models and codes are integrated for a more accurate simulation of the recording process. The integration of the models has been tested on a planar geometry. Finally, thermal simulations are run for stationary and moving predominantly TEand TM-polarized spots that are focused on the center groove of a Blu-ray disk. Conclusions: With the integration of the optical and the thermal model a tool has been developed with which several phenomena, such as polarization effects and the influence of changing the geometry an properties of the stack, can be simulated accurately. The results of such simulations will give insight in the optimization of groove geometry, stack design and the effects of for instance optical and thermal cross-track cross talk. c ©Philips Electronics Nederland BV 2002 iii 000/99 Company Confidential till 200210 iv c ©Philips Electronics Nederland BV 2002