Cold-Atom Physics Using Optical Nanofibers
Optical nanofibers offer a strong transverse confinement of their guided modes which exhibit a pronounced evanescent field surrounding the fiber. This allows to efficiently couple particles (atoms, molecules, etc.) on or near the nanofiber surface to the fiber modes, making nanofibers a powerful tool for their detection, investigation, and manipulation. In this context, we studied the interaction of a small number of cold caesium atoms with the fundamental fiber mode and the nanofiber surface by introducing a subwavelength-diameter optical nanofiber into a cold-atom cloud. Using high resolution spectroscopy, we observed and analyzed light-induced dipole forces, van der Waals interaction, and a significant enhancement of the spontaneous emission rate of the atoms. The latter can be assigned to the modification of the vacuum modes by the nanofiber.
(a) The intensity of the light that is guided by an optical nanofiber decays exponentially outside of the fiber. The decay length depends on the wavelength of the light. Therefore, red light protrudes further out of the fiber. (b) Combining light fields that are red and blue detuned with respect to the resonance frequency of caesium atoms, one can thus realize a trapping potential near the nanofiber surface for the latter.
Moreover, we are able to trap and optically interface laser-cooled atoms using optical nanofibers. Recently, we have shown that this "fiber-coupled" atomic ensemble shows good ground state coherence properties. These results pave the way towards the realization of fully fiber-integrated quantum memories, which would allow quantum communication over hundreds of kilometers given the measured coherence times, or which could be operated as highly efficient photon number-resolving detectors.
G. Sagué, E. Vetsch, W. Alt, D. Meschede, and A. Rauschenbeutel
Cold atom physics using ultra-thin optical fibers: Light-induced dipole forces and surface interactions
Phys. Rev. Lett. 99, 163602 (2007).
E. Vetsch, D. Reitz, G. Sagué, R. Schmidt, S. T. Dawkins, and A. Rauschenbeutel
Optical interface created by laser-cooled atoms trapped in the evanescent field surrounding an optical nanofiber
Phys. Rev. Lett. 104, 203603 (2010)
D. Reitz, C. Sayrin, R. Mitsch, P. Schneeweiss, and A. Rauschenbeutel
Coherence properties of nanofiber-trapped cesium atoms
(please see publication section for a complete list of the publications related to this experiment)
We gratefully acknowledge financial support by:
Volkswagen Foundation (Lichtenberg Professorship)
European Science Foundation (European Young Investigator Award)