Lorenz Chaos in Optically Pumped Lasers

Research over over the last eight years shows that lasers are among the most ver­ satile physical systems for studying the dynamic behaviour of nonlinear dissipa­ tive systems where motion never beco­ mes stable or periodic. The wide variety of laser classes, the ease with which several laser parameters can be changed and the rapidity of the internal relaxation proces­ ses have allowed the observation of a rich variety of unstable phenomena [1]. We review here recent studies of one particular type of phenomenon, namely the Lorenz behaviour of optically pumped lasers which represents the first experi­ mental observation of a behaviour of the type predicted by the Lorenz model for deterministic chaos in nonlinear dissipa­ tive systems [2]. It is shown that Lorenz features show some universality in that they are only weakly dependent on certain variables in the model, even though the variations entail a large increase in the number of degrees of freedom. Readers are referred to the literature for other examples demonstrating the versatility of lasers for studying dynamic systems as, for example, the observation of Shilnikov dynamics in CO2 lasers with feedback or with a saturable absorber [3] and the pre­ diction and observation of spatial struc­ tures and optical vortices in multimode lasers [4].