Optical information processing based on nonlinear properties of atomic gases

The effects associated with nonlinear interaction of electromagnetic field with atomic media are investigated in semiclassical approximation. The possibility of its application in information technologies is disscussed. Particularly, nonlinear effects related to the resonant interaction of electromagnetic fields that act on four transitions of a five level M scheme of atomic levels in the stationary limit are studied. Eight stationary solutions that depend on the state of circular polarizations of three operating classical modes of the field are found for the atomic density matrix. To decrease the absorption of the fields on the atomic transitions, the regime of electromagnetically induced transparency is used. The conditions under which the M scheme is close in its optical properties to two or three level schemes are found. Based on the obtained eight solutions, the total accumulated phase shifts of the working waves are calculated. It is shown that the M scheme can perform the operation of double controlled phase shift. Also a model of nonlinear optical system surrounded by two loops of feedback is investigated. The cell with the vapor of rubidium Lambda-type atoms is taken in the capacity of nonlinear element. Two modes of near-resonant electromagnetic field interacting with the cell are involved in the feedback. Two-dimensional optical bistability domain in location of input field intensities is obtained and dependence of its form and magnitude from the system parameters (photon detunings, feedback factor etc.) is investigated. “Input – output” relations corresponding to different trajectories in the bistability domain are obtained.