M.O. Scully

Atomic coherence effects within the sodium D1 manifold. I. Creation of coherence and dressed state analysis

The connection and similarity between two different models for lasing without inversion are studied, and various dressed state pictures enlighten its physical origin. Recent experiments on coherence effects in sodium are reviewed. The existence of atomic coherence in these experiments is critically examined. It is found that the hyperfine structure and the coupling coefficients within the sodium D1 manifold are of crucial importance.

Atomic coherence effects within the sodium D1 manifold. II. Coherent optical pumping

For pt. I see ibid. p. 231, 1994. We consider optical pumping in the multilevel sodium D1 manifold by several coherent light fields. Coherence between atomic states is taken into account by solving the complete density matrix equations. The manifestation of population trapping and the variation of transmitted light intensity are predicted numerically and verified experimentally for the sodium D1 line. The influence of relaxation and Doppler broadening is elucidated. The interaction of a strong and a weak field is shown to create electromagnetically induced transparency.

Atomic coherence effects within the sodium D1 manifold. III: Lasing without inversion via population trapping

Transient lasing without inversion has been experimentally demonstrated in sodium vapour. The principle of this atomic coherence effect can be well understood from the theory of a simple four-level system. The experimental results match with numerical simulations which take the complete hyperfine structure of the sodium D1 line into account. The differences between our system and a Raman laser are discussed.

Electromagnetically Induced Coherent Backscattering: Concepts and Experiments

We demonstrate a coherent backward wave oscillation using forward propagating fields. This is achieved by using an ultra-dispersive medium. The physics has much in common with propagation of ultraslow light. Experimental progress will be discussed.