LOW SCATTERING SILICA GLASS, AND METHOD FOR THERMALLY TREATING SILICA GLASS

摘要

Provided is a low scattering silica glass which is suitable as a material for an optical communication fiber. A silica glass having a fictive temperature of 1000°C or higher and having a pore radius of 0.240 nm or less as observed by a positron annihilation lifetime method. A method for thermally treating a silica glass, said method comprising holding the silica glass to be thermally treated under an atmosphere having a temperature ranging from 1200 to 2000°C inclusive and a pressure of 30 MPa or more and then cooling the silica glass, wherein the procedure for cooling the silica glass from 1200 to 900°C is carried out at an average temperature-lowering rate of 40°C/min or more. A method for thermally treating a silica glass, said method comprising holding the silica glass to be thermally treated under an atmosphere having a temperature ranging from 1200 to 2000°C inclusive and a pressure of 140 MPa or more and then cooling the silica glass, wherein the procedure for cooling the silica glass from 1200 to 900°C is carried out under an atmosphere having a pressure of 140 MPa or more.