| 摘要 |
1416387 Light focusing fibre waveguides CORNING GLASS WORKS 30 March 1973 [30 March 1972] 15431/73 Heading C1M [Also in Divisions G2-G3] A method of forming an article having a radially varying composition such as light focusing fibre waveguides comprises applying a plurality of layers of glass to a cylindrical member, each successive layer having an incrementally different composition as compared with the composition of the preceding layer, heating the structure so formed to the drawing temperature and drawing the heated structure to reduce the cross-sectional area thereof to form an article having a radially varying composition. Each layer may be formed from fused silica doped with a different quantity or kind of material. Suitable dopants are TiO 2 , Ta 2 O 5 , tin oxide, Nb 2 O 5 , ZrO 2 , Al 2 O 3 , La 2 O 3 and GeO 2 . The maximum amount of dopant is preferably below 25% by weight of the composition at that point. The layers may be applied by brushing, spraying or dipping a mixture of glass materials suspended in an organic resin vehicle, e.g. a mixture of titanium resinate solution containing 4À2% by weight Ti and silicon resinate solution containing 7% by weight Si; by chemical vapour deposition ; by radio frequency sputtering or by applying a glass frit and sintering the frit. The cylindrical member may be of glass having a coefficient of expansion compatible with the layers to be applied or graphite. In one embodiment, Fig. 2, a gas-vapour mixture is hydrolysed within flame 16 to form a glass soot 20 which is directed on to a rotated glass cylinder. The gasvapour mixture is changed for each successive layer 10. The soot may be sintered as deposited or it may thereafter be sintered. The cylindrical member may be ground out by means of a diamond reamer, laser milling, etching with hydrofluoric acid, or by core drilling. The resulting hollow body is then drawn to form a film of sold cross-section. If the cylindrical member is not removed from the structure the resulting structure may nevertheless be drawn, except no longitudinal hole will be collapsed. Alternatively the layers of incrementally different composition are applied to the internal surface of a hollow surface, e.g. by the flame hydrolysis technique. Each layer may be about 0À0175 inch in thickness and composite structures having up to 60 such layers may be produced. The plurality of layers of glass soot may be sintered in an induction furnace having an oxygen atmosphere at 1500‹ C. prior to drawing. The drawing may also be carried out in an induction furnace containing oxygen, at a temperature of 2000‹ C. Specific compositions of the glass layers disclosed are (a) a glass consisting of 99À993% by weight SiO 2 and 0À007% by weight TiO 2 and (b) a glass consisting of 97% by weight SiO 2 and 3% by weight TiO 2 . |
