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!