Coupled non-linear systems can be used to describe the dynamics of many interacting systems throughout physics such as Josephson junction arrays, Bose-Einstein condensate and laser arrays. In optics coupled lasers that exhibit a wide range of rich nonlinear and chaotic dynamics   have been a source of much interest over the past few decades. Coupled lasers have also been shown to have potential applications in the field of secure communications based on chaotic synchronization, and in the field of high power lasers based on coherent addition.

When the coupling strength between two lasers is grater then some threshold value phase locking between the two lasers occurs.  We theoretically investigated the dynamics of two weakly coupled laser systems and show how the nonlinear dynamics of the laser amplitudes increase the coherent addition efficiency by nearly an order of magnitude. Specifically, with coupling strength as low as one fifth the threshold value that result in a very low phase locking, laser amplitude synchronization results in an interference pattern contrast of above 90 %. As the coupling strength increases the amplitudes undergo a process of period doubling that eventually leads to chaos.