Optimization of a magneto–optic trap using nanofibers*

Abstract

We experimentally demonstrate a reliable method based on a nanofiber to optimize the number of cold atoms in a magneto–optical trap (MOT) and to monitor the MOT in real time. The atomic fluorescence is collected by a nanofiber with subwavelength diameter of about 400 nm. The MOT parameters are experimentally adjusted in order to match the maximum number of cold atoms provided by the fluorescence collected by the nanofiber. The maximum number of cold atoms is obtained when the intensities of the cooling and re-pumping beams are about 23.5 mW/cm2 and 7.1 mW/cm2, respectively; the detuning of the cooling beam is −13.0 MHz, and the axial magnetic gradient is about 9.7 Gauss/cm. We observe a maximum photon counting rate of nearly (4.5±0.1) × 105 counts/s. The nanofiber–atom system can provide a powerful and flexible tool for sensitive atom detection and for monitoring atom–matter coupling. It can be widely used from quantum optics to quantum precision measurement.