Study on Laser Cleaving of Brittle Materials with Two-Types Laser Beam (Precise Cleaving of the Thick Glass Materials with CO<sub>2</sub> Laser and Er:YAG Laser)

Abstract

This paper deals with the thermal stress cleaving of the thick glass with multiple laser beams. A continuous CO2 laser with a wavelength of 10.6 μm is used to generate the thermal gradients which cause the compressive stress at laser irradiated area and the tensile stress outside of the irradiated area in the specimen. A pulsed Er:YAG laser with a wavelength of 2.94 μm is used as a heat source to raise the temperature inside of the specimen. As a specimen, the soda lime glass with a thickness from 1.3 to 8.0 mm is used. The absorption coefficient at the wavelength of CO2 laser is 18.42 mm-1 and that of Er:YAG laser is 0.58 mm-1. The effect of internal heating with Er:YAG laser on cleaving characteristics, such as a laser power per unit length, thermal damage of the laser irradiated surface and surface roughness and straightness of the cleaved surface, are investigated experimentally. As a result, the application of multiple laser beams to the thermal stress cleaving made it possible to fabricate the thick glass without any damage such as a tipping and a sub-crack on the laser irradiated surface. The surface roughness and straightness at the cleaved surface is quite improved by the internal heating with Er:YAG laser irradiation.