A semiconductor gain device comprising a substrate; an optical waveguide layer extending from a first end of the substrate to a second end of the substrate opposite to the first end, the optical waveguide layer including an active layer formed on the upper surface; a reflective mirror provided at one end of the optical waveguide layer, and an exit aperture on the other end of the optical waveguide layer for emitting optical energy; wherein at least a portion of the optical waveguide layer is curved on the surface of the substrate from the first end to the second end with a radius of curvature of less than 4 mm.