High-power, diffraction-limited-beam operation from phase-locked diode-laser arrays of closely spaced ‘‘leaky’’ waveguides (antiguides)

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Abstract
A novel type of phase-locked diode-laser array is demonstrated: an array of closely spaced index depressions (antiguides). The arrays are ten-element AlGaAs/GaAs devices fabricated by metalorganic chemical vapor deposition and liquid phase epitaxy over a patterned substrate. The fundamental and highest-order modes of the array of antiguides have negligible radiation loss: 20–30 times less than that for a single antiguide. The modal-gain differentials between adjacent array modes are at least an order of magnitude larger than those for evanescently coupled arrays of positive-index guides. Fundamental-array-mode operation in a virtually diffraction-limited-beam (1.4°) pattern is obtained to 200 mW. Out-of-phase-mode operation in a virtually diffraction-limited-beam (1.2°) pattern is achieved to 110 mW/uncoated facet. The inherent array-mode stability of antiguided arrays is discussed.