Guiding laser-cooled atoms in hollow-core fibers

Laser-cooled atoms from a low-velocity atomic source are guided in a hollow-core optical fiber using the evanescent-wave dipole force from blue-detuned laser light launched into the glass region of the fiber. The transverse velocity of the guided atoms corresponds to a temperature of $50\hspace{0.5em}\mu \mathrm{K}.$ We achieve a maximum flux through a 23.5-cm-long fiber of 590 000 atoms/second with a laser power of 55 mWatts at a detuning of 6 GHz. With larger detunings of 40 GHz, spontaneous emission from the atoms inside the fiber can be suppressed and the atom’s internal-state population is preserved. We identify two major loss mechanisms for the guiding process and discuss possible solutions.