The present disclosure illustrates a composition of a visible light and infrared light transmitting optical colored glass. The chalcogenide semiconductor compound Cu.sub.2ZnSnS.sub.4 or Cu.sub.2ZnSnSe.sub.4 is added in the silicate glass system composition, to adjust color and the optical property of the glass. The glass made of this composition has a characteristic of the visible light and infrared light transmitting in a wavelength of range 400 nm to 1200 nm.

A doped silica-titania glass article is provided that includes a glass article having a glass composition comprising (i) a silica-titania base glass, (ii) a fluorine dopant, and (iii) a second dopant. The fluorine dopant has a concentration of fluorine of up to 5 wt. % and the second dopant comprises one or more oxides selected from the group consisting of Al, Nb, Ta, B, Na, K, Mg, Ca and Li oxides at a total oxide concentration from 50 ppm to 6 wt. %. Further, the glass article has an expansivity slope of less than 0.5 ppb/K.sup.2 at 20 C. The second dopant can be optional. The composition of the glass article may also contain an OH concentration of less than 100 ppm.

Ultralow expansion titania-silica glass. The glass has high hydroxyl content and optionally include one or more dopants. Representative optional dopants include boron, alkali elements, alkaline earth elements or metals such as Nb, Ta, Al, Mn, Sn Cu and Sn. The glass is prepared by a process that includes steam consolidation to increase the hydroxyl content. The high hydroxyl content or combination of dopant(s) and high hydroxyl content lowers the fictive temperature of the glass to provide a glass having a very low coefficient of thermal expansion (CTE), low fictive temperature (T.sub.f), and low expansivity slope.

A method for manufacturing an optical fiber preform includes: adding an alkali metal element or an alkaline earth metal element to an inner surface of a glass pipe made of silica-based glass; reducing a diameter of the glass pipe after the adding; etching an inner surface of a continuous section of the glass pipe in a longitudinal direction after the reducing; and collapsing the glass pipe after the etching. At least one of the adding, the reducing, the etching, and the collapsing includes performing a local etching on an inner surface of a section of the glass pipe that is shorter than the continuous section.

A manufacturing method of a quartz glass crucible includes: producing a quartz glass crucible by arc-melting raw material quartz powder deposited on an inner surface of a rotating mold; washing an inner surface of the quartz glass crucible with pure water thereby reducing a total concentration of Na, K, and Ca contained in a silica glass around the inner surface as compared to that before washing; and etching the inner surface with washing liquid containing hydrofluoric acid.