Statistical Features of a CO2 Laser with Pump Modulation

We report the behaviour of a single mode homogeneously broadened CO2 laser when the gain parameter is swept from a negative value (laser below threshold) to a positive one (laser above threshold), so that the dynamical system goes through a bifurcation point. The modulation of the control parameter (gain) is done by repeatedly applying a linear ramp to the discharge current. As the gain never takes the stationary value associated with the instantaneous current value, the observed bifurcation is delayed with respect to the time at which the control parameter passes through the instability [1].