Stabilization of unstable fixed points in the dynamics of a laser with feedback

We report theoretical and experimental results on the stabilization of unstable steady states in a CO2 laser with feedback. Periodic and chaotic oscillations have been suppressed by means of a control loop consisting of a high-pass filter, known as washout filter. Although the filter characteristics are determined on the basis of linear analysis, taking into account the problem of robustness with respect to parameter changes, the present control strategy provides a large attractive domain in the phase space.