Ultra-high Resolution Spectroscopy with atomic or molecular Dark Resonances: Exact steady-state lineshapes and asymptotic profiles in the adiabatic pulsed regime

Thomas Zanon-Willette (1) , Emeric de Clercq (2) , Ennio Arimondo (3)

1 LPMAA - Laboratoire de Physique Moleculaire pour l'Atmosphere et l'Astrophysique
2 SYRTE - Systèmes de Référence Temps Espace
3 Dipartimento di Fisica E. Fermi

Exact and asymptotic lineshape expressions are derived from the semi-classical density matrix representation describing a set of closed three-level $\Lambda$ atomic or molecular states including decoherences, relaxation rates and light-shifts. An accurate analysis of the exact steady-state Dark Resonance profile describing the Autler-Townes doublet, the Electromagnetically Induced Transparency or Coherent Population Trapping resonance and the Fano-Feshbach lineshape, leads to the linewidth expression of the two-photon Raman transition and frequency-shifts associated to the clock transition. From an adiabatic analysis of the dynamical Optical Bloch Equations in the weak field limit, a pumping time required to efficiently trap a large number of atoms into a coherent superposition of long-lived states is established. For a highly asymmetrical configuration with different decay channels, a strong two-photon resonance based on a lower states population inversion is established when the driving continuous-wave laser fields are greatly unbalanced. When time separated resonant two-photon pulses are applied in the adiabatic pulsed regime for atomic or molecular clock engineering, where the first pulse is long enough to reach a coherent steady-state preparation and the second pulse is very short to avoid repumping into a new dark state, Dark Resonance fringes mixing continuous-wave lineshape properties and coherent Ramsey oscillations are created. Those fringes allow interrogation schemes bypassing the power broadening effect. Frequency-shifts affecting the central clock fringe computed from asymptotic profiles and related to Raman decoherence process, exhibit non-linear shapes with the three-level observable used for quantum measurement. We point out that different observables experience different shifts on the lower-state clock transition.

Mots clés: Dark resonance; light shift; lineshape; Ramsey fringes

Domaines: Physique Atomique [physics.atom-ph]

Thomas Zanon-Willette, Emeric de Clercq, Ennio Arimondo. Ultra-high Resolution Spectroscopy with atomic or molecular Dark Resonances: Exact steady-state lineshapes and asymptotic profiles in the adiabatic pulsed regime. 2011. ⟨hal-00630748⟩