Phase-locked ridge waveguide InGaAs-GaAs-AlGaAs strained-layer quantum well heterostructure laser arrays

We report the characteristics of separate confinement heterostructure InGaAs/GaAs/AlGaAs strained-layer quantum well heterostructure (λ≳1 μm) 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 μm on 8 μm centers. Several etch depths are examined, covering the range from gain-guided to strongly index-guided elements. For these structures, values of effective index step, Δneff, below ∼6×10−3 are necessary to achieve interelement coupling. For Δneff=1.3×10−3, the devices lase in the highest array mode up to ∼1.5 times threshold with a nearly diffraction-limited double-lobed far-field pattern. For higher currents, additional structure in the far-field pattern is observed, and is accompanied by splitting of the longitudinal modes due to operation in additional array modes.