MASK DESIGN AND METHOD OF FABRICATING A MODE CONVERTER OPTICAL SEMICONDUCTOR DEVICE

A method of fabricating waveguide on a semiconductor substrate including an optical input at a first end region for receiving a continuous wave coherent light beam having a predetermined first beam profile, and a second end region opposite the first end region active layer for transferring the light beam with a predetermined second beam profile, including forming a sequence of layers including a bottom cladding layer, an active layer, and a top cladding layer on a semiconductor substrate; providing an appropriately configured mask over the region where a waveguide is to be formed; etching the semiconductor substrate down to the active layer thereby forming a partial waveguide structure; and re-growing the top cladding layer and the contact layer to the uniformly planar level of the top surface of the partial waveguide structure.