Integrated optical arrangement of ridge waveguides on a substrate

In an integrated optical arrangement composed of first and second strip-like ridge waveguides on a substrate of semiconductor material, each of said ridge waveguides being defined by an undoped or an n-doped waveguiding layer of semiconductor material on or in the substrate and by a strip-shaped ridge of semiconductor material that is fashioned on and over the waveguiding layer and defines a width of the strip-shaped ridge waveguide, each of said strip-shaped ridges of the first waveguide and the strip-shaped ridges of the second waveguide proceeding side-by-side separated by an interspace, and wherein externally contactable junctions selected from a group consisting of pn-junctions of p-doped and n-doped material and pin-junctions of p-doped and n-doped material separated by a layer of undoped material being integrated in the region of the strip-shaped ridge of each of the ridge waveguides above and below the waveguiding layer of the ridge waveguide and being integral so that the junction of p-doped to n-doped or undoped material is arranged at a distance from the waveguiding layer and the p-doped material is arranged at the side of the junction facing away from the waveguiding layer and wherein each of the junctions of both the first and second waveguides is contactable, the improvements comprising a third strip-shaped ridge waveguide being arranged in the interspace between the ridges of the first and second ridge waveguide, said third strip waveguide being defined by a waveguiding layer in the substrate and by a strip-shaped ridge fashioned over the waveguiding layer defining a width of said third ridge waveguide, said third strip-shaped ridge being a slight distance from the ridge of the first ridge waveguide and from the ridge of the second ridge waveguide, the junctions of the first ridge waveguide and the second ridge waveguide extend at least over a common longitudinal section of the three ridge waveguides in which the first, second and third ridge waveguides proceed simultaneously side-by-side and the junctions of the first and second ridge waveguides are contacted over the entire length of said common longitudinal section so that an optical mode guided in the waveguiding layer under the ridge of the third ridge waveguide is selectively coupled over into one of the waveguiding layer under the ridge of the first and second ridge waveguides and an optical mode guided in the waveguiding layer under the ridge of the first and second ridge waveguides is selectively coupled into the waveguiding layer under the ridge of the third ridge waveguide.