| 摘要 |
PURPOSE:To obtain the titled high-quality base material without absorbing OH and with less transmission loss by passing a gas contg. an etching agent through the inside of a hollow transparent glass base material having an F- content distribution in the specified radial direction, smoothing the inner wall by heating and making the material solid. CONSTITUTION:A quartz glass-forming material such as a combustible gas, O2 and SiCl4 is supplied from a burner 9 for forming a high-bulk density porous glass layer 11 and from a burner 10 for forming a low-bulk density glass layer 12 to deposit glass fine particles formed by flame hydrolysis on the surface from the part 13 of a quartz pipe for retaining a refractory starting material 7 such as a zirconia pipe attached to a rotary lifting device 8 and a porous glass base material is obtained while slowly rotating and lifting the pipe. Then dehydration, F addition and heating for vitrification are applied to a hollow cylindrical glass base material obtained by pulling out the starting material 7 from the base material to form a hollow transparent glass base material having an F-content distribution in the radial direction. A glass etching agent and, if necessary, O2 are passed through the inside of the base material to smooth the inner wall by heating and then the material is made solid by heating. |
