Structures for an optical component, such as an optical reflector or an Echelle grating, and methods of forming such structures. The structure comprises a first waveguide core positioned in a vertical direction over a semiconductor substrate. The first waveguide core includes a tapered section and a plurality of segments separated by a plurality of gaps. A second waveguide core, which is positioned in the vertical direction relative to the first waveguide core, includes a portion positioned adjacent to the first waveguide core.