Active waveguide branch with variable synchronism

An active optical waveguide for modulation or switching of optical power which comprises:

• a main waveguide section which propagates only a single local normal mode,
• said main waveguide branching into first and second diverging branching waveguide sections in a geometrically symmetrical manner with said branches lying in a horizontal plane with a spacing between said branching waveguide sections,
• said branching waveguide sections having a small included angle which is sufficiently small that optical modes will propagate adiabatically;
• first and second axially symmetric electrodes extending along said branching waveguide sections opposite their outer faces,
• said first electrode positioned opposite said first branching waveguide section,
• said second electrode positioned opposite said second branching waveguide section;
• a third electrode covering the spacing between said first and second branching waveguide sections and so positioned that the distances between the outer faces of said third electrode and the inner faces of said first and second electrodes are axially symmetrical and decrease along the length of said first and second branching waveguide sections in the direction away from said main waveguide;
• and
• means for applying a voltage to said electrodes such that said third electrode is made positive or negative in voltage with respect to said first and second electrodes thereby electro-optically raising the index of refraction of one branching waveguide section and lowering by the same amount the index of refraction of the other branching waveguide section,
• whereby optical power is directed to one branching waveguide section during application of one polarity potential and to the opposite branching waveguide section during application of the opposite polarity potential.