| 摘要 |
PROBLEM TO BE SOLVED: To obtain a glass composition whose transmittance in the ultraviolet region can be improved. SOLUTION: This fluorine added glass has >=10 ppm concentration of OH, >=10 ppm concentration of Cl and >=1,000 ppm concentration of F in silica and the ratio (concentration) of F to Cl is >=100. The transmittance of the fluorine added glass after irradiation with F2 laser light is lowered by <5%. When the ratio of F to Cl is increased to >=1,000, the transmittance of the fluorine added glass after irradiation with F2 laser light is lowered only by <1%.
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