Narrow spectral width high power distributed feedback semiconductor lasers

A method of forming a semiconductor laser comprising:

• (a) providing a semiconductor substrate having a surface on which epitaxial layers may be formed;
• (b) growing on the surface of the substrate at least a lower cladding layer, then a lower confinement layer, their an active region layer in which light emission occurs, and then an upper confinement layer that is free of aluminum;
• (c) then etching a distributed feedback grating structure on the aluminum free upper confinement layer comprising periodically alternating elements;
• and
• (d) then growing an upper cladding layer over the grating etched in the upper confinement layer to provide a grating in which the adjacent elements in the grating differ from one another in dielectric constant so as to provide optical feedback for a selected wavelength of light generation from the active region.