| 摘要 |
PROBLEM TO BE SOLVED: To realize an optical waveguide having large difference in the refractive index between the core and the clad and having small warpage and low loss. SOLUTION: A protruded core 2 consisting of SiONH is formed by a plasma CVD method on a SiO2 substrate 1. Since the refractive index nw of the core 2 is selected in the range from 1.46 to 1.57, an additive to control the refractive index is not required. SiO2 is used for the clad 3 to cover the core 2, and the material used further contains at least one kind of an additive to control the refractive index such as B, P, F to increase the difference in the refractive index and to control the coefficient of thermal expansion. When SiO2 is used for the clad 3, the difference in the refractive index between the core 2 and the clad 3 can be varied in the range of 0.17 to 7.0%. Since the SiONH film has the coefficient of thermal expansion close to that of the SiO2 substrate 1 and the clad 3, warpage can be reduced. |
