Pure in‐phase‐mode operation is obtained from 20/21‐element AlGaAs/GaAs antiguided arrays grown by two‐step metalorganic chemical vapor deposition. Oscillation of out‐of‐phase modes is substantially suppressed by a built‐in spatial filter: two sets of noncollinear antiguides separated by a 50‐&mgr;m‐long laterally unguided region, corresponding to the half‐Talbot distance. Design considerations for 20‐ vs 10‐element arrays are discussed. Diffraction‐limited‐beam operation (i.e., 0.8° lobewidth) is obtained to 1.5×threshold (90 mW, both facets). Beams with 1.3° lobewidth (1.6×diffraction limit) are obtained at 3×threshold and 300 mW (both facets). Devices with optimized facet coatings operate in a single, 1.5°‐wide lobe (i.e., 1.8×diffraction limit) at 330 mW front‐facet emitted power. The main lobe contains 80–87% of the total power.