We review the results of the work done on coherent effects in hollow-core photonic crystal fibers. These include generation of electromagnetically induced transparency and saturable absorption spectroscopy in molecular gases and atomic vapours.
Low-pressure acetylene in the hollow-core photonic crystal structure fibers is an excellent medium for the room-temperature investigation of the coherent quantum effects in communication wavelength region. Pulsed excitation enables observation of new coherent phenomena like optical nutation or photon echo and evaluation of important temporal characteristics of the light-molecule interactions. We also report original experimental results on the pulsed excitation of the electromagnetically induced transparency in co- and counter-propagation configurations.