Synchronization of coupled solid-state lasers

The synchronization of the intensities and phases of coupled solid-state lasers is investigated both experimentally, theoretically, and numerically. In particular, an understanding is developed of how the coupling between the different lasers affects the degree of synchronization between them.;The synchronization of two chaotic lasers is investigated first. Experimental measurements of two coupled lasers made chaotic either by pump or loss modulation show that the intensity fluctuations of the two lasers may be made synchronous if the coupling between the two lasers is made sufficiently large; phase synchronization is always seen to exist when appreciable intensity synchronization is found. Numerical models of two single-mode coupled lasers accurately reproduce the observed dynamics only when the the effects of additional longitudinal modes are included.;Next the dynamics of a system of two unmodulated, coupled lasers are studied for parameters near the phase-locking point. The existence of an amplitude instability is predicted analytically and numerically, and seen experimentally, for coupling strengths slightly less than that necessary to phase-lock the lasers and for frequency detunings on the same order of magnitude as the intensity relaxation oscillation frequency. Quantitative agreement is seen between experiment and theory when the fluctuating detuning is included.;Finally, a simple model for the experimentally measured dynamics of a two-dimensional array of lasers with reflective feedback is presented. This model describes the dynamics of a similar array driven unstable by the amplitude instability discussed previously. Experimentally the spatial correlation between pairs of lasers was investigated; a linear decay in the spatially-averaged intensity correlation function was seen as the distance between laser pairs was increased. In this model, similar decays in the intensity correlation function was seen for coupling strengths just slightly less than that necessary to phase-lock the array.