Embodiments of the present disclosure are directed toward techniques and configurations for an optical coupler. In some embodiments, the device may include an optical waveguide to transmit light input from a light source. The optical waveguide may include a semiconductor layer, having a trench with one facet that comprises an edge formed under an approximately 45 degree angle and another facet formed substantially normal to the semiconductor layer. The edge may interface with another medium to form a mirror to receive inputted light and reflect received light substantially perpendicularly to propagate the received light. Other embodiments may be described and/or claimed.
