A constant magnetic field is shown to favor the formation of “dark states” and depolarization due to radiation upon laser excitation and play a constructive role in the formation of ordered states.
We report an experimental observation of coherent population trapping in multilevel dark states prepared in the ground hyperfine states of 87Rb atoms confined in a room-temperature vapor cell. The dark states are created by a linearly polarized coupling laser that is tuned to the 87RbD1 $F=2\ensuremath{\leftrightarrow}{F}^{\ensuremath{'}}=1$ or 2 transition and establishes \ensuremath{\Lambda}-type transition chains. The Doppler shift for the \ensuremath{\Lambda}-type transition chains is compensated by the left and right circularly polarized components of the coupling laser. The multilevel dark states that consist of three or two magnetic sublevels among the five degenerate magnetic sublevels in the F=2 ground hyperfine state are probed by a weak probe laser scanned across the same D1 transition and their existence is manifested by a strong dependence of the probe excitation on the probe polarization. Our experiment demonstrates the importance of coherent population trapping in a laser coupled degenerate multilevel open atomic system, which may play an important role in diverse physical phenomena such as atom cooling and trapping, optical pumping, and multiple laser excitation and ionization of atoms and molecules.
This article discusses various aspects of coherent control of the medium using a preparatory laser radiation that provides favorable conditions for the propagation of useful radiation. We discussed the possibility of decrease molecular scattering full section in channels of propagation of laser signals, formation of clarified channel in the inhomogeneous medium of propagation and we analyze the molecular dissociation resulting from an increase in rotational energy induced by two successive laser pulses with orthogonal polarizations. Based on the results of calculations, a constant dipole moment of the molecule is shown to play an insignificant role in its orientation in a laser field.