Principle Of Laser Recording Mechanism By Forming An Alloy In The Multilayer Of Thin Metallic Films

Abstract

An optical recording disk employing an alloy mode mechanism has been developed. The disk is a plastic substrate on which a multilayer of four thin metallic films is formed by sputtering deposition. The first and the second layers on the substrate are the recording layers of Sb,Se, and Bi,Te,, respectively. The third is an adiabatic layer and the fourth e-rdflectivb layer. The disk is double-bonded; i.e., two disks are bonded together with protective and adhesive layers like a sandwich. The disk is recordable on one or both sides. A laser diode is used as the optical source for reading and writing. The laser beam scans the guide groove and address pits that have been embossed on the plastic substrate. The recording mechanism is based on multiple interference in the multilayer. When the laser beam heats the recording layers, the Sb2, Se3, and Bi2,Te3, form a four-element alloy by diffusion. Then the boundaries in the multilayer disappear to change the condition of initial multiple interference, which increases the reflectivity twice to2four times. The disk has high sensitivity and sharp cutoff at a laser power of 0.8nJ/μm2, below which the reflectivity does not change. The optimum recording power depends on the scanning velocity and pulse duration of the laser beam.