Patent ID: 7368403

Claim:
A synthetic quartz glass for an optical member, which is to be used in an optical device employing an ArF excimer laser beam as a light source at an energy density of at most 2 mJ/cm 2 /pulse, comprising: a hydrogen molecule concentration that is within a range of at least 1×10 16 molecules/cm 3 and less than 5×10 16 molecules/cm 3 , an OH group concentration that is at most 100 ppm, and the synthetic quartz glass satisfies ΔT 193ST <0.2 and (Δ T 193ST− ΔT 193RC )/Δ T 193ST <0.1, wherein ΔT 93ST (%/cm) represents an amount of decrease in an internal transmittance when the synthetic quartz glass is irradiated with the ArF excimer laser beam so that the internal transmittance at a wavelength of 193 nm emitted by the ArF excimer laser beam at the energy density of at most 2 mJ/cm 2 /pulse is in a stable state, and ΔT 193ST (%/cm) represents an amount of a decrease in the internal transmittance at the wavelength of 193 nm, when the irradiation with the ArF excimer laser beam is stopped for 50 seconds to recover the internal transmittance at a wavelength of 193 nm, and the synthetic quartz glass contains no fluorine.