Reduced-confinement antennas for GaAlAs integrated optical waveguides

Monolithically integrated reduced-confinement antennas are shown to produce reductions of >35% in the far-field beam divergence for radiation emitted from single-mode GaAlAs slab waveguides, yielding far-field beams as narrow as 8.2° FWHM along the direction perpendicular to the wafer surface. Reduced confinement of the guided mode near the output endface is achieved using a novel molecular beam epitaxy growth technique to produce a longitudinal variation in the refractive index and thickness of the waveguide film. Unlike present horn antennas, the reduced-confinement geometry has the distinct advantage of being compatible with two-dimensional antenna development.