Radiation trapping inside a hollow-core photonic crystal fiber
  We report the radiation trapping effect inside a hollow-core photonic crystal fiber (PCF). An optical dipole trap was used to load and confine the atoms in the PCF without contacting the wall of the fiber. The transmission of a probe light propagating through the PCF was studied experimentally and theoretically. With the experimental results and theoretical predictions, we conclude that the radiation trapping can play a significant role and should be taken into account in the spectroscopic measurements inside the PCF. 
H. H. Jen, Chang-Yi Wang, Kevin C. J. Lee, Yi-Hsin Chen, and Ite A. Yu
quant-ph physics.atom-ph physics.optics