| 摘要 |
PURPOSE:To couple the light power with a low loss between waveguides which differ in specific refractive index difference from each other by forming plural optical waveguides on a substrate, and varying one or both of them in waveguide size and equalizing the propagation constants of the both to each other. CONSTITUTION:The optical circuit consists of >=2 kinds of optical waveguides 6 and 7 which have different refractive index differences between the cores 3, 4 and clad 2, the optical waveguides 6 and 7 are put close to each other, and one or both of the waveguides are varied in waveguide size at the where the waveguides are put close to each other. Namely the width W2 of the waveguide 7 is varied and then the effective refractive index Neff,2 is equalized to the refractive index Neff,1 of the waveguide 6. Consequently, the power coupling rate eta becomes 1 by setting the length LC of the coupling part to an odd multiple of complete coupling length L0, namely the power can be transmitted from the waveguide 6 to the waveguide 7 without any loss. |
