Multistability in dynamical systems induced by weak periodic perturbations

It is shown that weak resonant perturbations at subharmonic frequencies can induce multistability in a wide class of nonlinear systems, which display the period-doubling route into chaos or possess isolated subharmonic branches. The number of attractors induced depends on the subharmonic frequency, amplitude, and phase of periodic perturbations, as well as an initial dynamical state of nonlinear systems. Experimental and numerical evidences are given on the basis of a loss-modulated CO2 laser.