Techniques for fabricating waveguide facets and die separation

A fabrication method includes arranging a plurality of dice on a substrate and performing a first etching process that etches a first layer of the substrate at a boundary between adjacent dice on the substrate. The etching forms facets of one or more waveguides that are defined within the first layer, and the etching leaves a portion of the first layer in the boundary between the adjacent dice. The method continues with a second etching process that etches the portion of the first layer and a second layer beneath the portion of the first layer, the second etching process forming a trench in the boundary where the second layer has a different material than the first layer. The method also includes separating the dice from one another along the trench.