Joan van der Waals Colloquium

Time: 13:15 hrs
Location: De Sitterzaal  

Abstract

“Cavity QED and Spin-Orbit Coupling of Light”
A high-finesse cavity with a single atom is an ideal playground to test fundamentals of light-matter interaction. This is particularly true in the strong-coupling regime of cavity QED, where a photon is exchanged between the cavity mode and the atom faster than all loss rates. At the Max-Planck-Institute for Quantum Optics in Garching we have performed many fundamental experiments in such a strongly coupled atom-cavity system. For instance, we have demonstrated experimentally that it is possible to operate the atom-cavity system as a gateway for photon pairs, favouring the simultaneous transmission of two photons [1]. The high-finesse cavities developed for cavity-QED systems can also be used to study intriguing properties of light even without the presence of an atom. Because of the high resolving power of a high-finesse resonator, the “fine structure” (analogous to that in atomic spectra) of the transmission spectrum of an optical resonator can be explored. This shows details which are caused by the breakdown of the paraxial approximation [2]. We have observed the corresponding cavity modes (see Fig.) and found quantitative agreement between the theoretical and experimental resonator spectrum. An important and unexpected result is the lifting of the degeneracy of Fabry-Perot cavity resonances by spin-orbit coupling of light, which can be shown to be entirely due to a Berry's geometric phase being picked up by the resonating light. Figure: Camera picture of a high-order transverse mode which was observed in the optical transmission of a high-finesse cavity. Modes which are degenerate within the paraxial approximation are split according to their total angular momentum. The large number of nodal lines in the azimuthal direction hints at the high orbital angular momentum involved in this mode.
References
[1] Nonlinear spectroscopy of photons bound to one atom, I. Schuster, A. Kubanek, A. Fuhrmanek, T.
Puppe, P.W.H. Pinkse, K. Murr, G. Rempe, Nature Phys. 4, 382 (2008).
[2] Calculating the Fine Structure of a Fabry-Perot Resonator using Spheroidal Wave Functions, M.
Zeppenfeld and P.W.H. Pinkse, Optics Express 18, 9580 (2010).