Method of increasing the initial transmittance of optical glass

A method of improving the 248 nm transmittance of a deep UV fused silica optical glass, the fused silica optical glass being formed from a halide-free polymethylsiloxane selected from the group consisting of hexamethyldisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethylcyclotrisiloxane, and mixtures of these;

• the fused silica optical glass having a plurality of metal ion impurities and non-bridging oxygens, a charge transfer absorption between the metal ion impurities and the non-bridging oxygens, and a 248 nm transmittance/cm no greater than 91.4%, the method comprising the step of:
• subjecting the deep UV fused silica optical glass to a gas selected from the group consisting of hydrogen and deuterium at a temperature and for a duration sufficient to cause the gas to diffuse into and react with the fused silica optical glass, wherein the step of subjecting improves the 248 nm transmittance/cm of the deep UV fused silica optical glass from 0.6% to 6.9% by reducing said charge transfer absorption.

A method of producing deep UV fused silica optical glass blanks, said method comprising the steps of:

• providing a fused silica glass having an initial 248 nm transmittance/cm no greater than 91.4% and a plurality of metal ions and non-bridging oxygen ions,
• subjecting said provided fused silica glass to a hydrogen treatment gas at a temperature and a duration sufficient to cause the hydrogen to diffuse into the fused silica glass and react with the metal ions and non-bridging oxygen ions to result in hydrogen being bonded to the non-bridging oxygen ions and reducing the metal ions, wherein said subjected fused silica glass has an increased 248 nm transmittance/cm, said increased 248 nm transmittance/cm is between 0.6% and 6.9% greater than said initial 248 nm transmittance/cm.

A method of forming a deep UV fused silica optical glass member blank, the method comprising the steps of:

• providing a fused silica optical glass blank having a plurality of metal ion impurities and non-bridging oxygens, said fused silica optical glass blank having a 248 nm transmittance/cm,
• subjecting the fused silica optical glass blank to a gas selected from the group consisting of deuterium, carbon monoxide and mixtures of these at a temperature and for a duration sufficient to cause the gas to diffuse into the fused silica optical glass and wherein said diffused gas reacts with the fused silica metal ion impurities and non-bridging oxygen and increases the 248 nm transmittance/cm of said fused silica optical glass.