| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical coupler having small connection loss. SOLUTION: Optical confinement can be intensified for each propagation mode of light propagating from outside through an input waveguide 22 to a multi waveguide part 21, by forming a high refractive index part 26-29 where a refractive index of the core is locally high near the connection part of the multi waveguide part 21 with the input/output waveguides 22-25 of the part 21. With the optical confinement intensified, the propagation constant becomes small in wavelength dependency, the connection loss is reduced, and the waveguide characteristics are greatly improved. As a result, an optical coupler with a small connection loss can be obtained. Similar effect can also be obtained by forming projections 41-44 in which the height of the core is locally high near the connection part of the multi waveguide part 21 with the input/output waveguides 22-25. |
