Dressed states and optical resonance

Eiichi Hanamura

The concept of the dressed-atom is extended to electronic system in solids under nearly resonant coherent laser field, which is in contact with phonon and photon fields. Optical resonance saturation and nonlinear optical free induction decay are discussed in terms of this dressed state. The effective temperature is defined in terms of population ratio between the doublet of the dressed states and is related to the optical phenomena from the aspect of an open system far from thermal equilibrium.

Gabriela Wa̧sik, Zbigniew Kowal, Wojciech Gawlik

G. Compagno, Roberto Passante, Franco Persico

Qilin Wu, Daniel J. Gauthier, THOMAS W. MOSSBERG

We experimentally investigate the transient dynamics of two-level atoms driven by a bichromatic optical excitation field when the bichromatic field is configured to contain a strong resonant component and a weaker nonresonant perturber component. We concentrate on the experimental situation in which the two-level atoms are prepared in an eigenstate (dressed state) of the coupled atom-resonant field system prior to exposure to the perturber field. We experimentally demonstrate perturber-field-induced, optical nutation of the dressed-state populations. We show how nutation of the dressed-state populations manifests itself in the fluorescence signal of the transiently driven atoms. We observe that the detuning of the perturber field from transitions between the dressed states of the atom-resonant field system plays the same role in determining the character of the dressed-state optical nutation as the atom-field detuning in the case of the ordinary optical nutation of atomic populations. Our experiments demonstrate the utility of the dressed-atom picture in understanding the complex dynamics of bichromatically driven atoms in a variety of circumstances.

Yea-Hwang Uang

M. S. Shahriar, Philip Hemmer

It is well known that the resonant Raman interaction optically pumps atoms into a non-absorbing dressed-state.1 When this state is long-lived compared to the optical Rabi frequencies and the decay rate of the intermediate state, many interesting dynamics arise. These dynamics are significant in applications such as Raman clock AC–Stark shifts, microwave phase-sensitive optical absorption,2 and Raman cooling. By using appropriate approximations, we show that these dynamics can be well described with a Bloch-vector model, which involves only ground-state populations and coherence. This ground-state Bloch-vector model resembles the Bloch-vector model of a two-level system, but it has subtly different dynamics. Furthermore, we construct a novel dressed-state Bloch-vector that clearly shows the analogy between conventional optical pumping and coherent Raman trapping. In this model, one dressed-state is a nonabsorbing state, and the other is an absorbing state. We use the dressed-state Bloch vector to show how Raman AC–Stark shift arises and how it depends on experimental parameters. We also show how the microwave phase-sensitive optical absorption can be quantitatively calculated in a simple way.