THERMAL MODELLING AND ANALYSIS OF HIGH DENSITY PHASE CHANGE REWRITABLE OPTICAL DATA STORAGE

Abstract

An improved three-dimensional thermal model was used to model and analyze the Ge2Sb2Te5-type DVD-RAM 2.6 GB and DVD-RAM 4.7 GB disks for the first time. The new model is more accurate in determining the thermal effects in phase change disks, as it takes into consideration the combined heating effects of both the incident and reflected irradiating laser light. A phase change optical disk thermal modelling and analysis software was also developed. The software is capable of analysing the disks while taking into account both the thermal and optical considerations of DVD-RAM disk design. Important thermal calibration plots that were obtained showed that the peak temperature increases proportionally with the thickness of the 2nd dielectric and phase change layers. It also increased with increases in the groove depth. However, the peak temperature decreased with increases in the reflective layer thickness, while remaining constant against the 1st dielectric layer thickness. Optical considerations like computed modulation amplitudes and measured complex refractive indices were taken into account to enhance the accuracy of the simulations. The final design parameters were chosen such that both the thermal and optical requirements of DVD-RAM disks were satisfied. Based on these parameters a commercial grade DVD-RAM 2.6 GB disk was successfully fabricated.