Optical member made of synthetic quartz glass, and process for its production

摘要

To reduce the change in the refractive index of an irradiated portion of synthetic quartz glass, caused by the irradiation with a high energy light emitted from a light source such as a KrF excimer laser or an ArF excimer laser. A process for producing an optical member made of synthetic quartz glass, wherein the OH group concentration of the optical member is set depending upon the energy density of the laser beam employed, to adjust the ratio R (KJ/cm²-ppb)^-1 of the change in the refractive index of the optical member to the cumulative irradiation energy (KJ/cm²) by the laser, to be 0<=R<=0.2, thereby to control the change in the refractive index of the optical member made of synthetic quartz glass by the irradiation with a laser beam to be within a predetermined range.