Theoretical Physics

10 February 2015
Time: 14:00 to 15:00
Location: Roger Stevens LT 24

Jonathan Goldwin (Birmingham)

Strong coupling of light and cold atoms in optical ring resonators

The coupling between light and matter in free space is typically weak, in the sense that large numbers of atoms or photons are required for any noticeable interaction. This situation changes within optical resonators with high quality factors, where the interaction time and single-photon intensity may become relatively large. In such an environment, the normal modes of the coupled atom-cavity system are 'dressed' states with both atomic and photonic character. Intra-cavity light drives the dynamics of confined atoms, and the atoms modify the light field through optomechanical backaction.

In the first part of my talk I will describe the theory of an atomic Bose-Einstein condensate under the combined influence of gravity and a vertically oriented intra-cavity optical lattice potential. The induced Bloch oscillations of the atoms cause a modulation of the light, which resonantly drives tunnelling between neighbouring lattice sites. For the right choice of parameters, the atoms are coherently transported uphill. In the second part, I will describe an experiment we are building to use cold atoms as the gain medium for a laser with tuneable coupling to its environment. By tailoring the refractive properties of the gas -- and therefore the intra-cavity group velocity -- the laser can be optimised for different sensing tasks, including time/frequency metrology, magnetometry, and rotation sensing.



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