| 摘要 |
PROBLEM TO BE SOLVED: To improve optical characteristics such as the reduction of loss in the case that a thermal expansion coefficient of a core pattern largely exceeds that of a substrate, in a method for manufacturing a quartz-based optical waveguide.SOLUTION: A lower cladding layer 4-2 is formed on a plane substrate 4-1 (Fig.4 (a)). Next, a convex portion 4-2A corresponding to a core pattern 4-3A of a core layer 4-3 is formed on a lower cladding layer 4-2 (Fig.4 (b)), wherein a height of the convex portion 4-2A is twice or more as great as a thickness of the core layer 4-3. Then, the core layer 4-3 having a thermal expansion coefficient higher than that of the plane substrate 4-1 is deposited on the lower cladding layer 4-2 (Fig.4 (c)). After the core layer 4-3 is subjected to heat treatment at a predetermined heat treatment temperature, an upper cladding layer 4-4 is formed so as to cover the core layer 4-3 (Fig.4 (d)). A width of the convex portion 4-2A, namely, a width of the core pattern 4-3A is so determined that tensile stress acting on the core pattern 4-3A due to the heat treatment is ≤70 MPa. |
