Laser application for optical glass polishing

Abstract

Rapid generation of large area polished optical surfaces by high-power CO2 laser irradiation is shown. Results focus on glasses with high expansion coefficients (α≥10-5/°C) conventionally used in the optical industry. The technique involves active beam integration to obtain an intensity irradiation profile with a good uniformity over large spot sizes and is applied to preheated glass samples with initial rms roughness up to 500 nm. To find out the conditions for successful and reliable use of the proposed laser polishing method, the laser-driven heating process was monitored by means of the surface and depth temperature distributions. Whereas the former was determined in situ from the IR radiation emitted by the glass surface, the latter was obtained by comparison of the IR radiation emitted by the bulk sample with a theoretical model. Laser polishing of 5000 mm2 glass surfaces is reported and processes involved in the modification of the surface texture of the irradiated samples are described and discussed. © 1998 Society of Photo-Optical Instrumentation Engineers.