Atomic spectroscopy at interfaces (SAI)
Daniel Bloch, Martial Ducloy, Isabelle Maurin, Athanasios Laliotis, João Carlos de Aquino Carvalho (PhD), Junior Lukusa-Mudiayi (PhD)
Former PhD students: Philippe Ballin (june 2012), Elias Moufarej (december 2014)
The team studies the confinement on a vapour through linear laser spectroscopy and sub-Doppler signatures. The confinement is induced by the vicinity of an ideal plane surface, or results from an infiltration in interstices (porous media, opals, ...). The confinement affects the individual response of atoms (modified energy levels and transition couplings) as well as collective behaviors through a coherent veleocity-dependent response.
Reflection spectroscopy at an interface ("selective reflection") probes a typical depth Lambda/2 pi (~100 nm for experiments in the visible range). It has been used for exhaustive studies of the Casimir-Polder interaction (CP) in the near-field regime, which is equivalent to the van der Waals surface attraction (with its -C3i z-3 potential, where z is the atom-surface distance, and C3i a coefficient specific to the atomic level |i>). This interaction between atom dipole fluctuations and the related fluctuations of the electric image induced in the surface can also be interpreted through quantum vacuum fluctuations ("Cavity QED"), with the boundary conditions determined by the interface. The study of excited atoms allows to evidence resonant couplings with surface modes ("polaritons"), whose energy is in the infrared range.
A recent success was the observation of a CP interaction depending on the wall temperature (fig. 1). The atom probes the thermal emission of surface modes in the near-field. The excitation of an atom through a real energy transfer from the surface thermal emission is now under study.
Following our pioneering work on sub-Doppler spectroscopy on nanocell (one dimensional confinement), we investigate the spectroscopy of a vapour under a three-dimensional confinement, through infiltration in the interstices of an artificial opal or a photonic crystal, or through porous media (in co-operation with Uruguay). Also, the extension to molecular transitions, weaker than atomic resonances, has now provided first signals.
Fig. 1: Temperature dependence of the C3 coefficient for Cs(7D3/2) at a sapphire interface.
see also http://www.cnrs.fr/inp/spip.php?article3111