0.45 W diffraction-limited beam and single-frequency operation from antiguided phase-locked laser array with distributed feedback grating

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Abstract
A second-order diffraction grating placed below the active region of a phase-locked resonant antiguided array selects the in-phase array mode in addition to its role as a single-longitudinal-mode selector. This type of array-mode discrimination relies on the fact that the resonant in-phase array mode has significantly better field overlap with the grating region than nonresonant array modes. Furthermore, it eliminates the need for a conventional array-mode discriminator: interelement loss; which can cause self-pulsations. Diffraction-limited beam and single-frequency operation is obtained to at least 0.45 W peak pulsed power from 20 element, InGaAs/InGaP/GaAs structures (λ=0.97 μm) of 120-μm-wide aperture. Distributed-feedback operation is confirmed over the 20–40 °C temperature range. The results are in good agreement with theory.