Stabilisation of chaotic dynamics in semiconductor lasers with optical feedback using optimal control

The application of a method for controlling time-delay chaotic systems to the control of external-cavity laser diode dynamics is reported. The approach is based on optimal control theory and, in general, aims to stabilise nonlinear time-delay systems by the use of an approximating sequence technique. The goal of the approximating sequence technique is to reduce a given nonlinear system into a sequence of linear time-varying equations, with the purpose of approximating to the solution of the nonlinear system. In each of these equations, the linear-quadratic optimal tracking control is implemented. It is shown that in the case of chaotic external-cavity lasers, a feedback control via the laser bias current enables the selection of the desired dynamical behaviour.