ATOMIC COOPERATION AND NONLINEAR DYNAMICS IN A MESOSCOPIC MASER

We consider a mesoscopic maser, in which a beam of excited two-level R ydberg atoms interacts with a single radiation mode during propagation through a resonant cavity. The number of atoms in the cavity ranges f rom a few tens to a few hundreds. Steady-state and nonlinear dynamics are investigated both with and without a coherent driving field. At st eady state, atomic cooperation can induce multistability and temporal instabilities. A novel type of bistability is predicted for the amplit ude of the coherently driven cavity held as a function of atomic densi ty. The system dynamics exhibits a variety of regimes, including chaos . We have explored them by varying the experimentally accessible param eters: atomic density, cavity linewidth and driving field amplitude.