Embodiments of the present disclosure are directed toward an optical apparatus that includes a semiconductor layer to propagate light from at least one light source. The optical apparatus may further include a curved echelle grating with a plurality of grating teeth, the echelle grating at an outer side of the semiconductor layer. The curved echelle grating may include a plurality of grating teeth, and a grating tooth of the plurality of grating teeth may have a grating facet and a shadow facet. A shadow facet may have an angle of grating greater than 0 degrees with respect to a normal of a curve of the curved echelle grating. Other embodiments may be described and/or claimed.