We report the characteristics of separate confinement heterostructure InGaAs/GaAs/AlGaAs strainedhyphen;layer quantum well heterostructure (lgr;gsim;1 mgr;m) ridge waveguide laser arrays grown by metalorganic chemical vapor deposition, and etched by reactive ion etching. The ten element arrays have ridge widths of 4 mgr;m on 8 mgr;m centers. Several etch depths are examined, covering the range from gainhyphen;guided to strongly indexhyphen;guided elements. For these structures, values of effective index step, Dgr;neff, below sim;6times;10minus;3are necessary to achieve interelement coupling. For Dgr;neff=1.3times;10minus;3, the devices lase in the highest array mode up to sim;1.5 times threshold with a nearly diffractionhyphen;limited doublehyphen;lobed farhyphen;field pattern. For higher currents, additional structure in the farhyphen;field pattern is observed, and is accompanied by splitting of the longitudinal modes due to operation in additional array modes.
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