Mechanism for recording and erasing optical information by laser radiation on an SiO2-(Co+Si)-SiO2-Si multilayer structure

We present in this paper results of investigation of optical properties of SiO2-(Co plus Si)-SiO2-Si structures under laser treatment with Q-switched YAG:Nd and carbon dioxide lasers. The photo-thermo-chemical reaction of Co with Si has a threshold character. No changes in optical properties of (Co plus Si) mixture was observed up to intensities of carbon dioxide laser radiation 2 MW/cm2. At larger intensities the reflection coefficient R decreases from 70% to 45% with increasing of the intensity up to 8 MW/cm2. When this multilayer structure is irradiated with Q-switched YAG:Nd laser with radiation intensity from 14 MW/cm2 to 53 MW/cm2, the magnitude of reflection coefficient returns to its initial value 70%. It means that the information recorded by carbon-dioxide laser is erased. Calculations of the temperature field during irradiation with carbon-dioxide and YAG:Nd laser showed that the phase transition from mixture (Co plus Si) to CoSi2 caused by irradiation with carbon-dioxide laser results in recording of information, whereas the thermal impact caused by irradiation with YAG:Nd laser results in amorphization of CoSi2 and erasing of information.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.