Nonlinear cavity QED and spin-orbit coupling of light
Dr. Pepijn Pinkse (Max-Planck-Institut für Quantenoptik, Garching)

<p> 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 an optical excitation is exchanged between the cavity mode and the atom faster than all loss rates. A consequence is that the coupled system behaves fundamentally different than the sum of its constituents. For instance, the atom-cavity system shows resonances which favour the transmission of photon pairs. We demonstrate this two-photon transition by resolving it spectroscopically [1]. At the same time, we detect the super-Poissonian photon statistics on this resonance [2]. </p>

<p> 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, sets of distinct higher-order transverse cavity modes are observed which should all be degenerate in the paraxial approximation. A new set of vector solutions to Maxwell's equations based on solutions to the wave equation in spheroidal coordinates [3] allows us to calculate the first-order corrections in the short wavelength limit to eigenmodes and eigenfrequencies in a Fabry-Perot resonator. The predicted lifting of degeneracies matches the observed set of cavity modes well, including a splitting due to coupling between orbital angular momentum and spin angular momentum. </p>

<p> [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) </p>

<p> [2] Two-Photon Gateway in One-Atom Cavity Quantum Electrodynamics, A. Kubanek, A. Ourjoumtsev, I. Schuster, M. Koch, P.W.H. Pinkse, K. Murr, G. Rempe, Phys. Rev. Lett. 101, 203602 (2008) </p>

<p> [3] Solutions to Maxwell's Equations using Spheroidal Coordinates, M. Zeppenfeld, ArXiv 0901.3662 </p>