| 摘要 |
PROBLEM TO BE SOLVED: To provide a directional coupler which has a more reduced driving voltage and allows a traveling wave type electrode to be relatively freely designed and thereby can be operated at high speed. SOLUTION: The directional coupler includes a substrate 11 having an electrooptic effect, at least a pair of optical waveguides 12 formed on the substrate, and control electrodes (13 and 14) for controlling effective refractive indexes of the optical waveguides. In operating parts s of the optical waveguides which an electric field of the control electrode acts on, polarization directions of the substrate in the right and the left of a center line C of the pair of optical waveguide as a boundary are different, and polarization directions of the substrate before and after one or more crossing lines L as boundaries, which cross the center line to divide the operating parts into a plurality of regions in a lengthwise direction along the optical waveguides, are different. COPYRIGHT: (C)2011,JPO&INPIT |
