A device that includes an optical coupler with a waveguide and waveguide index matched materials at an edge of a substrate, and a method of forming the device, is provided herein. The device comprises: a substrate having an edge, and an opening formed therein adjacent the edge; a layer of insulator on the substrate, which forms a bridge across the opening at the edge; a waveguide on the layer of insulator, the waveguide comprising a constant-width region and a tapered region terminating at the edge in a region of the opening; a first layer of optical epoxy in the opening, the optical epoxy indexed matched to the layer of insulator; and, a second layer of the optical epoxy on the tapered region, such that the optical epoxy optically contains an optical signal leaking from the waveguide in the tapered region.