Mode launching on a multimode slab-waveguide by a plane wave

Abstract: Mode launching on a symmetrical multimode slab-waveguide by a plane wave incident onto the front side of the guide is investigated theoretically and experimentally. A single plane wave always excites a whole set of modes. Among these are, in general, three adjacent modesm-1, m, m+1 which are excited most strongly. The relative power launched into these modes is approximately given by the ratio 0.4:1:0.4. The theoretical results are confirmed by qualitative observations of the far-field mode patterns. In the far field the modes are separated by using a wedge-type waveguide.