External-cavity designs for phase-coupled laser diode arrays

High-brightness single laser diodes based on the taper design have demonstrated output powers of a few watts with a single transverse mode operation. The use of arrays of such lasers results in a further increase of the laser power, but with the drawback of a loss in the spatial brightness which is reduced as the filling factor of the array. To overcome this limitation, coherent operation of the laser array does improve the brightness. The purpose of this work is to propose and evaluate passive coherent combining architectures, based on external cavity designs. Coherence of the entire laser bars is induced by the diffractive coupling between the emitters within the external cavity. Two different configurations were described, the first one is based on the Talbot self-imaging effect and the second one consists in the angular filtering of the laser emission.