Spontaneous improvement of spatial coherence and frequency locking in high-pump-power multimode lasers

By using the time average of amplitude products we are able to identify changes in the dynamical complexity and the spatial coherence of a multimode laser. We find that there are cases in which as the pump increases, the dynamical complexity decreases and the spatial coherence improves. In some limiting cases the complexity is reduced to zero and the beam is completely coherent spatially. We show that these phenomena are caused by phase synchronization of the mode amplitudes and that they can be observed using slow detectors.