Phase-locked InGaAsP laser array with diffraction coupling

Abstract
A phase-locked array of InGaAsP lasers has been fabricated for the first time. This 50-μm-wide array utilized diffraction coupling between 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.