High-power spatially coherent operation of unstable resonator semiconductor lasers with regrown lens trains

We have obtained high-power spatially coherent operation in wide-stripe InGaAs/GaAs/AlGaAs semiconductor lasers using a monolithic unstable resonator [consisting of diverging lens elements incorporated above an asymmetric graded-index separate confinement heterostructure (AGRIN-SCH)]. The fabrication involves MOCVD regrowth after wet-chemical etching of lens-like patterns in a GaAs layer above the active region. Pulsed output powers of 175 and 490 mW have been obtained in 170- and 100-μm-wide lasers, respectively, with spatial coherence in the near field exceeding 60%. We observe good lateral mode discrimination up to 3.5 times threshold in the 100-μm stripes with a round-trip magnification of 6.4.