Study of laser texturing processes by reflected light detection

Abstract

Laser texturing technique has been established to provide low flying height and low stiction required for manufacturing high storage density media. The characteristics of the laser bumps can be precisely controlled, and are critically important for the excellent tribological performance. In the study, the hard disks have been textured successfully using the argon ion laser with the aid of an acoustic-optic modulator in the optical path. Alternative laser bumps can be formed with various bump shape and bump height. The topography of the laser bumps are observed using AFM. Laser bumps are formed because of the modification of laser beam on the substrate surface during the heating and cooling processes. In attempt to study the bump formation mechanisms, a photodiode was employed to detect the reflected and scattered laser light, which irradiates on the hard disk surface to form laser bumps. The detected signals were studied under various laser power and pulse duration. It was found that there is a good correlation between the detected signal and the laser bump characteristics. The system has been proved to be an effective and convenient method to study the laser bump formation processes, and to in situ diagnose the laser bump characteristics.