We conduct experiments with Cs atoms, cooled by a magneto-optical trap, surrounding a tapered optical nanofibre with a diameter of only 400 nm. The fibre is so thin – less than half the wavelength of light at 852 nm – that the optical field is located mostly in the evanescent field surrounding the fibre. This means that atoms outside the fibre can interact strongly with the field within the fibre.
Here is an example showing the photon counting rate with the MOT, without the MOT, and without lasers. See how the spontaneous emission from the cesium atoms is coupled into the nanofibre!
We have made the nano fibre part of a ring resonator, and observed the vacuum Rabi splitting in such a resonator. At higher power in the resonator, the atoms are saturated by the circulating laser field but at low power, a distinct splitting is observed. Below is shown a figure where the resonator transmission is shown as a function of the laser detuning from the atomic resonance. The resonance of the ring resonator is locked to the atomic resonance.
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