An apparatus includes a write pole proximate a media-facing surface of a recording head. A near-field transducer is adjacent to the write pole. A waveguide has a core layer extending from an energy source to the media-facing surface. The core layer includes a region of reduced downtrack thickness proximate the near-field transducer. The region of reduced downtrack thickness is defined by a notch facing away from the near-field transducer. A material of the notch has a different index of refraction than an index of refraction of the core layer.