A luminaire module includes light-emitting elements (LEEs) arranged to provide light; a light guide including a receiving end and an opposing end, the receiving end arranged to receive light provided by the LEEs, a core including a first transparent material with a first refractive index, the core having a pair of opposing side surfaces extending along a length of the light guide between the receiving and opposing ends, and a cladding including a second material having a second smaller refractive index, the cladding extending across and being in contact with at least a portion of the opposing side surfaces forming a cladding-core interface. The cladding-core interface is optically smooth. Additionally, the luminaire module includes an optical extractor arranged to receive guided light from the opposing end of the light guide and configured to output into the ambient environment at least some of the received guided light.