A semiconductor fabrication process comprising: providing a wafer comprising an optical waveguide semiconductor structure; selectively etching the optical waveguide semiconductor structure with an anisotropic wet etch process to form an angled semiconductor sidewall surface on the optical waveguide semiconductor structure; and processing the angled semiconductor sidewall surface on the optical waveguide semiconductor structure to form a mirror for deflecting optical signals into and out of a lateral plane that is parallel to a major wafer substrate surface, where processing the angled semiconductor sidewall surface comprises: selectively forming one or more patterned oxidation protection layers (109, 110) on the angled semiconductor sidewall surface of the optical waveguide semiconductor structure to expose a first portion of the optical waveguide semiconductor structure defining a first angled semiconductor sidewall surface and to cover a second portion of the optical waveguide semiconductor structure; oxidizing the first portion of the optical waveguide semiconductor structure with a semiconductor oxidation process to produce an oxide layer with an angled oxide sidewall surface substantially parallel to where the first angled semiconductor sidewall surface was located prior to oxidation; removing at least the one or more patterned oxidation protection layers (109, 110) to form a recess opening in the wafer; and growing an epitaxial semiconductor layer in the recess opening from at least the second portion of the optical waveguide semiconductor structure to form the mirror at an interface between the epitaxial semiconductor layer and the angled oxide sidewall surface. providing a wafer comprising an optical waveguide semiconductor structure; selectively etching the optical waveguide semiconductor structure with an anisotropic wet etch process to form an angled semiconductor sidewall surface on the optical waveguide semiconductor structure; and processing the angled semiconductor sidewall surface on the optical waveguide semiconductor structure to form a mirror for deflecting optical signals into and out of a lateral plane that is parallel to a major wafer substrate surface, where processing the angled semiconductor sidewall surface comprises: selectively forming one or more patterned oxidation protection layers (109, 110) on the angled semiconductor sidewall surface of the optical waveguide semiconductor structure to expose a first portion of the optical waveguide semiconductor structure defining a first angled semiconductor sidewall surface and to cover a second portion of the optical waveguide semiconductor structure; oxidizing the first portion of the optical waveguide semiconductor structure with a semiconductor oxidation process to produce an oxide layer with an angled oxide sidewall surface substantially parallel to where the first angled semiconductor sidewall surface was located prior to oxidation; removing at least the one or more patterned oxidation protection layers (109, 110) to form a recess opening in the wafer; and growing an epitaxial semiconductor layer in the recess opening from at least the second portion of the optical waveguide semiconductor structure to form the mirror at an interface between the epitaxial semiconductor layer and the angled oxide sidewall surface. selectively forming one or more patterned oxidation protection layers (109, 110) on the angled semiconductor sidewall surface of the optical waveguide semiconductor structure to expose a first portion of the optical waveguide semiconductor structure defining a first angled semiconductor sidewall surface and to cover a second portion of the optical waveguide semiconductor structure; oxidizing the first portion of the optical waveguide semiconductor structure with a semiconductor oxidation process to produce an oxide layer with an angled oxide sidewall surface substantially parallel to where the first angled semiconductor sidewall surface was located prior to oxidation; removing at least the one or more patterned oxidation protection layers (109, 110) to form a recess opening in the wafer; and growing an epitaxial semiconductor layer in the recess opening from at least the second portion of the optical waveguide semiconductor structure to form the mirror at an interface between the epitaxial semiconductor layer and the angled oxide sidewall surface.