Theory of a quantum beat laser in a three-level cascade atomic system

Osman Cizmeci, Muhammad Suhail Zubairy

Jianping Song, Yu Feng, Chenli Gan +9 more

Fifth-order attosecond sum-frequency polarization beat (FASPB) is studied in a cascade three level system with the phase-conjugation fourth-order coherence function theory. An improved schematic diagram of geometry, which is different from that inducing fifth-order femtosecond different-frequency polarization beat (FFDPB), is used to obtain FASPB. By analyzing the cases that pump beams have either narrow or broad bandwidth, it is found that the temporal behavior of the sum-frequency polarization beat signal depends on the properties of the lasers and transverse relaxation rate of the atomic energy-level system. Finally, the cascaded four-wave mixing (FWM) processes and the difference between attosecond and femtosecond polarization beats have been discussed, it is found that cascaded or sequential lower processes can often obscure the direct fifth-order polarization beat processes.

Bryan J. Dalton

A theory of stepwise pulsed-laser excitation of cascade Zeeman quantum beats has been developed for a four-level system. The laser pulses are treated in the broad-line approximation and the full optical-pumping equations for the atomic-density matrix of each level have been obtained. These can be used to describe saturation and light shift effects. The weak-pumping theory solutions to the optical pumping equations have been used to obtain expressions for the cascade quantum-beat intensity versus time curves. Larmor precession, spontaneous-emission decay and the populating of the final cascade level during the excitation pulse are all allowed for. A Wiener-Levy phase diffusion model with slowly varying amplitudes is used for the laser pulses, and the final theoretical expressions for the quantum beats depend on the time-dependent intensities of the laser pulses as well as on their polarisations. Hyperfine effects have been ignored. The theory applies to both coincident pulses and to pulses with a time delay between them. An illustrative application to the case of two very short but coincident pulses (during which Larmor precession, spontaneous emission etc. can be ignored) is given. In an accompanying paper the theoretical expressions are further evaluated and successfully applied to the interpretation of cascade Zeeman quantum beat experiments in Fe I.

Aaron S. Manka, Christoph H. Keitel, Shi-Yao Zhu +3 more

Tobias Kramer, Mirta Rodríquez Pinilla, Christian Bracher

Li Ming Yuan

The fourth order coherence function theory has been applyed to study the nonlinear effects of fifth order on polarization beats of a cascade three level system in chaos field.By analyzed the cases that pump beams have either narrowband or broadband linewidth,we found that for both cases the beat signal of the different temporal behavior depends on the stochastic properties of the lasers and transverse relaxation rate of the transition.We also found that a Doppler free precision can be achieved in the measurement of the energy level difference.The spatial modulation behavior of the beat signal has also been discussed.