A write head includes a near-field transducer near a media-facing surface of the write head and a waveguide. The waveguide includes a core that overlaps or is co-planer with the near-field transducer at a first region. The core has a second region extending away from the near-field transducer to an energy source. The core has a third region between the first and second regions. The third region has a third crosstrack width that is less than first and second crosstrack widths of the first and second regions