We report the first mode-locked operation of resonant optical waveguid
e (ROW) semiconductor laser arrays. The well-behaved emission patterns
of such arrays allow coupling to external cavities with efficiencies
comparable to those achieved by using single-element lasers. Single an
d multisegment lasers are employed to achieve active, passive, and hyb
rid mode-locking. The use of an arrayed gain region is effective in in
creasing the saturation energies of gain and absorber segments, result
ing in high pulse energies. Pulses are generated that have well-suppre
ssed secondary pulsations, with pulsewidths as short as 5.6 ps and pea
k powers of over 3 W in a collimated beam with a single main lobe.