Saturated absorption in acetylene and hydrogen cyanide in hollow-core photonic bandgap fibers

Saturated absorption is studied in overtone transitions of C2H2 and (HCN)-C-13 molecules confined in the hollow core of a photonic bandgap fiber. The dynamics of filling and venting the fiber is markedly different for the two molecules owing to the presence of a permanent dipole moment in one of them. Saturation is observed for input power down to 10 mW, and well resolved Lamb dips limited by transit time broadening across the 10 m m core diameter are observed with a counter-propagating probe beam. (c) 2005 Optical Society of America.