Interaction of light with a single atom in the strong focusing regime

Title: Interaction of light with a single atom in the strong focusing regime

Speaker: Kadir Durak

Abstract: We investigate both theoretically and experimentally the near-resonant interaction between a single atom and a focused coherent light beam. We have demonstrated that even for a moderate focusing strength, a single atom localized at the focus of a simple aspheric lens can scatter a significant fraction of light.The strength of an observed effect together with the theoretical predictions suggests to combine the effects of strong focusing with the well-established methods of cavity QED. As an example one can consider a concentric cavity which mirrors are shaped such that the cavity mode volume matches the one subtended between the aspheric lenses in an optimal focusing geometry. Simple estimates show that in such case one can achieve the single photon Rabi frequency few times larger than obtained in the current experiments and thus be able to reduce the Q-factor of the mirrors needed to compensate for the losses. This opens new perspectives in possibility to scale up the system consisting of many `atom+cavity' nodes for quantum networking due to a significant technical simplification of the atom-light interfaces.

We also elaborate both theoretically and experimentally the effect of the temporal pulse shape of the light for maximal excitation probability of a single atom. The result of this study suggests using our spontaneously emitted photons that are the products of a four-wave mixing process combined with the strongly focused (near concentric) cavity that has a large enough linewidth to work with a small input number of photons.


Kadir Durak graduated from Physics department in 2009 from METU. He started his PhD at Centre for Quantum Technologies, National University of Singapore, Singapore, the same year under the supervision of Prof. Christian Kurtsiefer.