| 摘要 |
PURPOSE:To obtain a doped glass base material satisfying low OH groups and high NA by heat-treating a porous glass base material in an atmosphere contg. a gas which volatilize a dopant and a gas which does not volatilize the dopant and wherein the volatilized dopant is not redeposited. CONSTITUTION:An atmosphere contg. an atmospheric gas of chlorine or a chlorine compd. and used for volatilizing a dopant and an atmospheric gas consisting of a chlorine compd. and not volatilizing the dopant is formed, and the volatilized dopant is not redeposited in said atmosphere. A quartz porous glass base material contg. a dopant is heat-treated in said atmosphere. The low OH, high NA, the clarification of the interface between both adjacent glasses, etc. can be satisfied by said method. |
