According to one aspect, a waveguide comprises a waveguide body further comprising a first face and a second face opposite the first face and a coupling cavity comprising an extent between the first and second faces and defined by at least one light coupling feature that extends between the first and second faces. The coupling cavity is adapted to receive a light emitting diode and the coupling cavity is noncircular and nonrectangular in a cross-section perpendicular to the extent of the coupling cavity. Further, the at least one light coupling feature comprises at least one protrusion.