An apparatus includes a waveguide core having an elongated edge parallel to a substrate plane of the apparatus. An output end of the waveguide core faces a media-facing surface of the apparatus. A plate-like portion of a plasmonic material has a major surface facing the elongated edge of the waveguide core, and the major surface has a narrowed output end facing the media-facing surface. An elongated ridge of the plasmonic material is disposed on at least part of the plate-like portion between an input end and the narrowed output end.