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.