Localised structures in edge emitter semiconductor lasers

This work analyzes the behaviour of a broad area edge emitter laser pumped slightly below threshold. This study shows the formation of isolated intensity peaks induced by the injection of pulses in the transverse section and persisting after the passage of the pulse. The total intensity response is characterised as a function of the intensity and frequency of the holding beam. The authors explore mainly the conditions under which a bistable behaviour is observed. The existence of a two peaks distribution is shown as well. Furthermore, this study considers a model describing a laser diode with a large transverse section. The basic equations describe the coupled dynamics of the electric field and of the carrier density. The field equation includes a 1D transverse Laplacian which describes diffraction in the paraxial approximation, while the carrier equation includes carrier diffusion. The radiation-matter interaction is described by the semiconductor Bloch equations. The authors integrate numerically the dynamical equations assuming a top-hat profile for the current in such a way to simulate the finite extension of the gain region. This boundary condition is fundamental for the agreement between theory and experiments. Experimental and theoretical results can be compared as a specific parameter is changed. The sequence of bifurcations generated is in perfect agreement with the experimental results.