An apparatus includes a waveguide extending along a light-propagation direction between a light source and a media-facing surface. The waveguide comprises an assistant layer configured to receive light from a light source, truncated with an intermediate bottom cladding layer. A core layer comprises a coupling end configured to receive light from the assistant layer. The coupling end comprises a taper that widens toward the media-facing surface. A near field transducer is disposed proximate the media-facing surface and is configured to receive the light from the core layer.