A luminaire comprises an optical element. The optical element comprises a coupling portion that comprises a coupling cavity that extends along a length of the optical element. The coupling cavity is configured to receive at least one light emitting diode. The optical element further comprises first and second sections extending away from the coupling portion of the optical element along the length of the coupling cavity. The first section comprises a first thickness closer to the coupling portion and a second thickness further from the coupling portion. The first thickness is greater than the second thickness. The second section comprises a third thickness closer to the coupling portion and a fourth thickness further from the coupling portion. The third thickness is greater than the fourth thickness. Light is extracted out of extraction features of opposing sides of at least one section.