OPTICAL WAVEGUIDE HAVING HIGH SPECIFIC REFRACTIVE INDEX DIFFERENCE AND METHOD FOR ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To produce a small-sized low-cost optical waveguide having a small loss and a high specific refractive index difference. ;SOLUTION: A core 3 having a high refractive index is formed on a substrate 1, the periphery of the core 3 is coated with clad layers 2, 4 having a low refractive index obtained by adding fluorine to SiO2 and heat treatment is carried out at 1,250-1,300°C to diffuse fluorine in the surface of the clad layer 4. An SiO2 protective layer 5 is formed and the heat treatment is carried out at 800-1,200°C to attain annealing while preventing the diffusion of fluorine in the interior of the clad layer 4. The rise of the refractive index of the clad layer 4 is prevented and the specific refractive index difference between the core 3 and the clad layer 4 is increased. The confinement of light is therefore promoted and the resulting quartz glass waveguide is easily reduced in loss, size and cost.;COPYRIGHT: (C)2001,JPO