Optical member made of high-purity and transparent synthetic silica glass and method for production thereof or blank thereof
AssigneesShin-Etsu Quartz Products Co., Ltd., Heraeus Quarzglas GmbH & Co. KG
InventorsShigeru Yamagata, Michiyou Kuriyama, Kyoichi Inaki, Ralf Takke
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Abstract
This invention relates to an optical member made of highly transparent, high-purity synthetic silica glass, to a method for manufacturing a blank or an optical member of such glass, and to the optical members themselves. The optical members have an absolute refractive index, n.sub.d, of 1.460 or more and a hydrogen molecule concentration of at least 5.times.10.sup.16 molecules/cm.sup.3 uniformly distributed throughout the glass and are particularly well suited for use in apparatus in which they are exposed to a high-power laser beam such as that produced by an excimer laser.
Claims21
An optical member exhibiting improved resistance to degradation upon exposure to ultraviolet laser radiation, said optical member consisting of synthetic silica glass having a refractive index n.sub.d of at least 1,460 at a wavelength of 589 nm, a hydrogen molecule content substantially evenly distributed throughout the glass of at least 5.times.10.sup.16 molecules/cm.sup.3, and Raman scattering intensity ratios R.sub.1 and R.sub.2 of less than 0.48 and less than 0.15, respectively, where R.sub.1 is the ratio of the Raman scattering peak intensity (I.sub.1) at a wave number of 495 cm.sup.-1 to the Raman scattering peak intensity (I.sub.0) at a wave number of 800 cm.sup.-1, and R.sub.2 is the ratio of the Raman peak scattering intensity (I.sub.2) at a wave number of 606 cm.sup.-1 to I.sub.0 as defined above.
An optical member exhibiting improved resistance to degradation upon exposure to ultraviolet laser radiation, said optical member being formed by synthesizing a solid ingot of silica glass by oxyhydrogen flame hydrolysis;
- heat treating said glass at a temperature of at least 1000.degree. C. under an atmosphere at a pressure of at least 1000 kgf/cm.sup.2 consisting essentially of rare gas for a period of time sufficient to obtain a hydrogen molecule content substantially evenly distributed throughout the glass of at least 5.times.10.sup.16 molecules/cm.sup.3 ;
- cooling the heat treated glass to a temperature below the strain point of the glass while maintaining an elevated pressure of at least 500 kgf/cm.sup.2, whereby the rate of cooling in the temperature range between the lower of 1200.degree. C. or the maximum heat treatment temperature and said temperature below the strain point of the glass is at most 100.degree. C./hr;
- and forming the cooled glass into an optical member.
Dependencies are inferred from the claim text.