A method, and devices produced therewith, for improving the flatness of etched mirror facets (18) of integrated optic structures with non-planar stripe waveguides (17) such as ridge or groove diode lasers or passive devices like modulators and switches. The curvature in the mirror facet surface, occurring at the edges of the waveguide due to topographical, lithographical and etch process effects, that causes detrimental phase distortions, is avoided by widening the waveguide end (23) near the mirror surface (18) thereby shifting the curved facet regions away from the light mode region (24) to surface regions (29) where curvature is not critical.