Optical members and blanks or synthetic silica glass and method for their production

A synthetic silica glass optical member for use with a high-power ultraviolet laser beam having a wavelength shorter than 250 nm, wherein said optical member is made of high-purity synthetic silica glass material which is free from striae in at least one direction corresponding to the incident light, and said member has an OH group concentration of at least about 100 wt. ppm, and a doped hydrogen molecule concentration sufficient to inhibit decreases in light transmittance over time due to exposure to light from said laser beam, said hydrogen concentration being such that when the temperature of said optical member is raised to 1,000.degree. C. under vacuum, at least about 1.times.10.sup.20 molecules/m.sup.2 of dopant gas are released from said member.

A blank for a synthetic silica glass optical member for use with incident light having a wavelength shorter than about 360 nm, wherein said blank is made of a heat treated high-purity silica glass material which is free from striae at least in a direction parallel to the incident light and which contains OH groups, said blank having a minimum OH group concentration of at least about 100 wt. ppm and an OH group concentration distribution in a plane orthogonal to the incident light such that the OH concentration progressively increases from a minimum concentration region to a maximum concentration region without an inflection point so that said blank has an overall refractive index distribution inhomogeneity (.delta.n) in said plane of 2.times.10.sup.-6 or less, and wherein said blank is doped with hydrogen.

A blank for a synthetic silica glass optical member for use with incident light having a wavelength shorter than about 360 nm, wherein said blank is made of a high-purity synthetic silica glass material which is free from striae in at least a direction parallel to the incident light, and which contains concentrations of OH groups and chlorine (Cl) distributed therein, said blank having a first refractive index distribution due to a fictive temperature distribution caused during heating/cooling treatment of the blank, and said first refractive index distribution is substantially offset by a second refractive index distribution due to a combination of the chlorine concentration distribution and the OH group concentration distribution in a plane orthogonal to the incident light.

A method of producing an optical member or blank for use with light having a wavelength rang shorter than about 360 nm, said method comprising the steps of:

• forming a blank from high-purity synthetic silica glass containing OH groups in an amount of at least 50 wt. ppm;
• removing striae from said blank in at least one direction;
• removing internal strains from said bank by heating the blank at a temperature of 1,000.degree. to 1,200.degree. C., and doping said silica glass under an elevated pressure atmosphere containing hydrogen heated to a temperature lower than the temperature of the heated atmosphere of the internal strain removing step such that said glass contains sufficient hydrogen to inhibit decreases in light transmittance over time due to exposure to ultraviolet light.

An optical device comprising in combination a synthetic silica glass optical member for use with ultraviolet incident light having a wavelength shorter than about 360 nm, wherein said optical member is made of high-purity synthetic silica glass material which is free from striae in at least one direction corresponding to the incident light and which contains OH groups in an amount of at least about 50 wt. ppm, and said optical member is doped with hydrogen sufficient to inhibit decreases in light transmittance over time due to exposure to said ultraviolet light and a source of radiation arranged to irradiate said optical member.

A synthetic silica glass optical member for use with ultraviolet incident light having a wavelength shorter than about 360 nm, wherein said optical member is made of an annealed high-purity synthetic silica glass material which is free from striae in at least one direction corresponding to the incident light and which contains OH groups in an amount of at least about 50 wt. ppm and chlorine (Cl) distributed therein, and said optical member is doped with hydrogen sufficient to inhibit decreases in light transmittance over time due to exposure to said ultraviolet light, and said optical member has a first refractive index distribution due to a fictive temperature distribution caused during annealing of said silica glass, and said first refractive index distribution is substantially offset by a second refractive index distribution due to a combination of variations in the chlorine distribution and variations in the OH group distribution in a plane orthogonal to the incident light.

A synthetic silica glass optical member for use with a source of ultraviolet incident light having a wavelength shorter than about 360 nm, wherein said optical member is made of a high-purity synthetic silica glass material which is free from striae in at least one direction corresponding to the incident light and which contains OH groups in an amount of at least about 50 wt. ppm, and said optical member is doped with hydrogen sufficient to inhibit decreases in light transmittance over time due to exposure to said ultraviolet light, said optical member having an OH group concentration distribution in a plane orthogonal to the incident light such that the OH concentration increases progressively from a minimum concentration region to a maximum concentration region without an inflection point so that the refractive index distribution inhomogeneity (.delta.n) in said plane is 2.times.10.sup.-6 or less.