Monolithic phase-locked resonant arrays of antiguides, resonant optical-waveguide (ROW) arrays, have been optimized for efficient in-phase-mode operation. Diffraction-limited, in-phase-mode continuous-wave (cw) operation is obtained from 20-element uniform arrays to 250 mW output power, with (front facet) external differential quantum efficiencies of 41%. Single longitudinal mode operation is observed below 100 mW cw. In-phase-operating devices with and without Talbot-type spatial filters are compared, and it is found that for ROW arrays Talbot-type spatial filters are not required.