Phase-locked InGaAsP laser array with diffraction coupling

A phase-locked array of InGaAsP lasers has been fabricated for the first time. The array utilized diffraction coupling between 10 adjacent lasers to achieve phase locking. Threshold current as low as 200 mA is obtained for arrays with 250 μm cavity length. Smooth single-lobe far field patterns with beam divergence as narrow as 3° have been achieved.