Suppression of Multistability in a Multimode VCSEL by Isotropic Optical Feedback

We study experimentally the behavior of a multistable vertical cavity surface-emitting laser under influence of isotropic optical feedback (OF). Without feedback, this laser displays spatial multistability which shows up in the laser power and polarized-resolved measurements of the laser intensity. We show that OF shifts the existence boundaries of multistability and can suppress multistability for a strong enough strength of optical feedback transforming it into bistability. This effect is demonstrated with the help of hysteretic dependencies of the laser intensity on the injection current and by the method of vibrational resonance. The latter method allows one to reveal “hidden” states which cannot be observed in the hysteretic behavior. Besides, we study also how optical feedback changes statistical properties of polarization fluctuations. We show that a strong enough OF leads to symmetrization of the distribution function of polarization noise.