Waveguide mirror and method of fabricating a waveguide mirror

A mirror and method of fabricating the mirror, the method comprising: providing a silicon-on-insulator substrate, the substrate comprising: a silicon support layer; a buried oxide (BOX) layer on top of the silicon support layer; and a silicon device layer on top of the BOX layer; creating a via in the silicon device layer, the via extending to the BOX layer; etching away a portion of the BOX layer starting at the via and extending laterally away from the via in a first direction to create a channel between the silicon device layer and silicon support layer; applying an anisotropic etch via the channel to regions of the silicon device layer and silicon support layer adjacent to the channel; the anisotropic etch following an orientation plane of the silicon device layer and silicon support layer to create a cavity underneath an overhanging portion of the silicon device layer; the overhanging portion defining a planar underside surface for vertically coupling light into and out of the silicon device layer; and applying a metal coating to the underside surface.