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The phase-locking of two-dimensional (2D) arrays incorporating a large number of electrically pumped, vertical cavity surface emitting lasers (VCSELs) is described. The InGaAs/GaAs quantum well VCSELs are phase locked by patterning the reflectivity of the laser back mirrors. Structures with both weak and strong modulation of the mirror reflectivity have been studied. The strongly modulated (weakly coupled) structures exhibit superior coherence and beam patterns, with up to 27×27 lasers oscillating in virtually a single (highest order) supermode. The weakly modulated (strongly coupled) arrays also emit highly coherent beams, but with lower threshold currents and higher differential efficiencies. Weakly modulated arrays of 20×20 elements (120×120 μm2) exhibited threshold currents of 1 mA per laser and ≳300 mW pulsed output powers. These coherent 2D arrays should be useful for optical signal processing and high optical power applications.
Orenstein et al. (1992) studied this question.