Abstract: A folded optical waveguide structure comprises a substrate supporting a waveguide slab. An array of laterally spaced grating waveguides extends from the slab along the substrate to propagate optical signals to and from a reflective surface of a mirror member at an end face of the substrate. A layer of index matching material is located between the ends of the waveguides and the reflective surface. A thermally conductive, e.g. copper, body is interposed between the mirror member and the substrate such that dimensional changes of the thermally conductive body resulting from changes in ambient temperature of the grating array waveguides, tilt the mirror member against the substrate, away from or toward the end face of the substrate.

Abstract: An optical waveguide device comprising a free space region, suitably provided by a slab waveguide, having optical signal ports for coupling to input and output waveguide sections and an optical waveguide grating including an array of grating waveguides coupling the free space region to a reflector surface to provide a folded structure. Dielectric waveguide structures are preferred. The grating includes tapered optical waveguide sections laterally spaced and optically isolated from each other which extend from the free space region, with the grating waveguides continuing as extensions of the tapered waveguide sections. Each of the grating waveguides differs in length from a neighboring grating waveguide by a constant increment, preferably an optical path length increment.