| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical directional coupler which can be joined to an optical fiber with high joint efficiency and which is small-sized and of low loss. SOLUTION: The optical directional coupler has two optical waveguides provided over a first region to a fifth region which are consecutive along a propagation direction of light. At the first region and the fifth region, spacing between respective cores 12 is relatively widened and at the third region, spacing between respective optical waveguides is relatively narrowed so that light beams propagating in the respective optical waveguides interact. Further a low refractive index region 13 which is provided between the cores 12 of respective optical waveguides located at the third region and has refractive index lower than refractive index of a clad, is provided. In each optical waveguide, specific refractive index difference between the core and the clad at least at the third region is made to be larger than specific refractive index difference between the core and the clad at the first region and at the fifth region. COPYRIGHT: (C)2004,JPO |
