Atomic Coherence Effects Research Articles

Effects of atomic coherence on a rydberg atom undergoing a two-photon transition in a lossless cavity

The effects of the atomic coherence on the dynamical and statistical properties of an atom undergoing two-photon process are investigated for a field initially in either a coherent state or in a squeezed coherent state. The behaviour here is in contrast with an atom undergoing a one-photon process in which case the Rabi-oscillations are qualitatively the same for all values of coherences between the two atomic levels. Comparison between exact numerical results and the one obtained from the model describing two-photon process is also discussed.

Effect of three-level atomic state coherence on collapse and revival dynamics

For a three-level atom with two excited states each dipole-coupled to a common ground state, the authors have found a particular linear combination of the atomic states which will not experience Rabi oscillations and their associated collapses and revivals. If the atom is initially prepared in this combination state, the atomic population will be coherently trapped there, and the dynamical behaviour will be constant in time.

Effects of Atomic Coherence on Collapses and Revivals in the Binomial State of the Field

Abstract The effects of the coherence between the states of a two-level atom on the phenomenon of collapses and revivals in an undamped binomial state of the electromagnetic field are investigated. It is found that the Rabi oscillations exhibit qualitatively different behaviour for different phases of coherence between the levels. This behaviour in the binomial state of the field is in contrast with that in a coherent state field, in which case the Rabi oscillations are qualitatively the same for all values of the coherence between the two atomic levels.

Squeezing of quantum fluctuations via atomic coherence effects.

In the three-level medium a ${\ensuremath{\chi}}^{(3)}$ may be generated by atomic coherence effects which involve negligible saturation and, hence, are essentially "spontaneous-emission-free." This offers considerable experimental advantages for the generation of squeezed states of light via four-wave mixing or optical bistability.

Atomic coherence effects in a two-mode laser with coupled transitions

An analytical nonperturbative theory of a two-mode laser with coupled transitions is presented. The gain medium is modeled as a homogeneously broadened ..lambda..-type three-level system. Stable stationary solutions of such a two-mode laser are studied with particular attention paid to the two-photon-induced atomic coherence effects. Our analysis shows that the nonradiative collisional decay of atomic coherence affects substantially the extent of mode competition. In particular, the coexistence domain of the two modes increases with a faster decay of the quadrupole atomic coherence that also leads to an increase in the power extraction efficiency.

Atomic coherence effects in resonant degenerate four-wave mixing

We present a study of atomic coherence effects in resonant degenerate four-wave mixing. We find for energy levels having magnetic degeneracies, the third-order nonlinear response resulting from two counterpropagating pump waves orthogonally polarized to an incident probe wave generates a signal whose polarization is phase conjugate to that of the incident probe wave. This effect is due to the coupling of different magnetic states resulting from coherent excitation giving rise to a net electric quadrupole. Experimental studies in Na on the D2 line at 5890 Å confirm the analysis.

Coherent absorption in a homogeneously broadened medium

An investigation of the propagation properties of a short pulse in a resonant absorber with a homogeneously broadened transition is presented with two main questions in mind: 1) the influence of the input pulse area on the transitory regime and on the steady-state propagation; 2) the effects of atomic coherence on the pulse shaping and the time delay of the leading edge of the pulse. The transitory regime of a propagating pulse is investigated and the stability of some asymptotic wave form confirmed. As expected, the transversal relaxation mechanism affects critically the major features of the coherent interaction. A detailed analysis of this problem is also presented.