Abstract: Provided is a titanium-containing quartz glass having excellent UV absorption. The quartz glass absorbs ultraviolet rays having a wavelength of 250 nm or less, ozone generation-related adverse effects on the human body, are prevented, a decrease in transmittance of the quartz glass in the range from near-ultraviolet to visible light due to being colored when irradiated with ultraviolet rays does not occur, absorption build-up or lamp burst-inducing deformation build-up, which is caused by a structural change in the quartz glass that occurs in the range of 200-300 nm when irradiated with ultraviolet rays, is suppressed, and a decrease in transmittance at intended wavelength ranges does not occur even when exposed to ultraviolet rays. The titanium-containing quartz glass having excellent UV absorption is colorless, wherein the average concentration of titanium is 10-500 ppm, the concentration of OH group is 10-350 ppm.

Abstract: It is an object of the invention to provide a synthetic silica glass for a cladding of a core from a fiber laser. The refractive index should be low and there should be no foaming foreign substances. This object is achieved by a synthetic silica glass for an optical element, which contains paramagnetic E? defect centers in an amount that is sufficient to set the absorption coefficient at 215 nm is in the range between 0.001 cm?1 and 2 cm?1; it contains paramagnetic oxygen defect centers in an amount that is sufficient to set the absorption coefficient at 250 nm is in the range between 0.001 cm?1 and 2 cm?1; the OH group concentration is 5 wtppm or less; the viscosity at 1100° C. is in the range between 1×1013.5 poise and 1×1015.5; the total content of metallic elements of Group 3 and Group 13 of the periodic table is 50.000 wtppm or less; and the relative refractive index difference of said synthetic silica glass is in the range between +0.

Abstract: It is an object of the invention to provide a synthetic silica glass for a cladding of a core from a fiber laser. The refractive index should be low and there should be no foaming foreign substances. This object is achieved by a synthetic silica glass for an optical element, which contains paramagnetic E? defect centers in an amount that is sufficient to set the absorption coefficient at 215 nm is in the range between 0.001 cm?1 and 2 cm?1; it contains paramagnetic oxygen defect centers in an amount that is sufficient to set the absorption coefficient at 250 nm is in the range between 0.001 cm?1 and 2 cm?1; the OH group concentration is 5 wtppm or less; the viscosity at 1100° C. is in the range between 1×1013.5 poise and 1×1015.5; the total content of metallic elements of Group 3 and Group 13 of the periodic table is 50.000 wtppm or less; and the relative refractive index difference of said synthetic silica glass is in the range between +0.