Laser-cooled atoms inside a hollow-core photonic-crystal fiber
  We describe the loading of laser-cooled rubidium atoms into a single-mode hollow-core photonic-crystal fiber. Inside the fiber, the atoms are confined by a far-detuned optical trap and probed by a weak resonant beam. We describe different loading methods and compare their trade-offs in terms of implementation complexity and atom-loading efficiency. The most efficient procedure results in loading of ~30,000 rubidium atoms, which creates a medium with optical depth ~180 inside the fiber. Compared to our earlier study this represents a six-fold increase in maximum achieved optical depth in this system. 
M. Bajcsy, S. Hofferberth, T. Peyronel, V. Balic, Q. Liang, A. S.   Zibrov, V. Vuletic, M. D. Lukin
physics.atom-ph physics.optics quant-ph