Abstract
Optical nanofibres are ultrathin optical fibres with a waist diameter typically less than the wavelength of light being guided through them. Cold atoms can couple to the evanescent field of the nanofibre-guided modes and such systems are emerging as promising technologies for the development of atom-photon hybrid quantum devices. Atoms within the evanescent field region of an optical nanofibre can be probed by sending near or on-resonant light through the fibre; however, the probe light can detrimentally affect the properties of the atoms. In this paper, we report on the modification of the local temperature of laser-cooled 87Rb atoms in a magneto-optical trap centred around an optical nanofibre when near-resonant probe light propagates through it. A transient absorption technique has been used to measure the temperature of the affected atoms and temperature variations from 160 μk to 850 μk, for a probe power ranging from 0 to 50 nW, have been observed. This effect could have implications in relation to using optical nanofibres for probing and manipulating cold or ultracold atoms.
Highlights
We report on the modification of the local temperature of laser-cooled 87Rb atoms in a magnetooptical trap centred around an optical nanofibre when near-resonant probe light propagates through it
Thence, we study the effect of a resonant probe beam on the local temperature of the atoms, i.e. those atoms closest to the nanofibre surface, and show a good fit with theory
We have measured the temperature of cold atoms using a transient absorption method whereby an on-resonant probe beam is passed through an optical nanofibre
Summary
The fibre is pulled simultaneously at both ends using computer-controlled motors This leads to a tapering of the original fibre and provides an ONF with a submicron waist diameter. In the experiments reported here, the diameter of the ONF is ∼350 nm with a transmission of ∼84% for 780 nm light when installed in the ultrahigh vacuum chamber needed for the MOT. At this diameter, only the fundamental mode can propagate through the ONF for 780 nm light. In contrast to the fluorescence-based measurements, this enables us to study the effect of the probe itself on the local temperature of the cloud and provides a method by which we can directly modify it.
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