Silica glass is one of the most important materials in optical and electronic applications. We have investigated the wet etching characteristics of silica glass in a buffered hydrofluoric acid (BHF) solution after a thermal treatment with a CW CO2 laser. The etch rate at the center of the treated region is found to increase by approximately 100% compared to the untreated glass. This shows that the fast thermal cycle experienced by glass as a result of the laser processing changes microstructure, as characterized by an increase in fictive temperature. Thermally manipulating the microstructure of silica glass with a laser may prove to be an important new fabrication technique for integrated optics. (C) 2003 Elsevier B.V. All rights reserved.