| 摘要 |
PROBLEM TO BE SOLVED: To obtain a continuous fine adjusting function for group speed variance by providing a large group speed variance compensating function by inter-mode coupling between optical waveguides. SOLUTION: The large group speed variance compensating function is obtained by the inter-mode coupling between the optical waveguides which are formed of a semiconductor material and have different sectional shapes. The optical waveguides are so designed that light of a TE0 mode is propagated only by the optical waveguide 5 in a mode conversion area 7 and light of a coupling mode of TE2 of the optical waveguide 4 and TE0 mode of the optical waveguide 5 is propagated in a mode coupling area (group speed variance compensation area) 8. When the optical waveguides 4 and 5 in the mode conversion area are present, the propagation constants of the modes are denoted as β1 and β2 and the coupling constant when the modes are coupled together is denoted as κ. When positive group speed variance is obtained by coupling TE0 and TE2 in phase in the mode coupling area, the thickness of a buffer layer 3 of the mode conversion area 7 is so determined that κ=-δ. Here, δ=(β1 -β2 )/2. For opposite-phase coupling, κ=δ. |
