| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical waveguide element including a mode splitter capable of mode separation from a waveguide capable of guiding two or more kinds of propagation modes, which is connected to a preceding stage of an optical demultiplexer.SOLUTION: An optical waveguide element 10 including an optical waveguide having a core 2 and a clad 3 on a substrate 1 comprises an optical demultiplexer 14 for demultiplexing one input light to a plurality of output light, and a mode splitter 20 provided on a preceding stage which is an input side of the optical demultiplexer 14. A n/nwhich is a ratio between a refractive index nof the core 2 and a refractive index nof the clad 3 is within a range of 101-250%, the mode splitter 20 includes a main waveguide 21 capable of guiding at least two or more kinds of propagation modes with different propagation orders, and a sub waveguide 22 which has a part 22b constituting a directional coupler placed in parallel with the main waveguide 21 at a fixed distance away from the main waveguide 21 and separates at least one or more kinds of propagation modes with different propagation orders from the main waveguide 21. |
