Controlled light localization and nonlinear-optical interactions of ultrashort laser pulses in micro- and nanostructured fibers with a tunable photonic band gap

Physical principles behind the control of light localization and nonlinear- optical interactions in micro- and nanostructured fibers are demonstrated. Transmission measurements on the cladding of nanostructured fibers having a form of a two-dimensional periodic structure with a pitch less than 500 nm have revealed the existence of a photonic band gap tunable within the rang e from 930 to 1030 nm. The influence of the structure of the holey-fiber cl adding on the effective area of the waveguide mode and the spectral broaden ing of Ti:sapphire and Cr:forsterite femtosecond laser pulses is experiment ally studied. It is shown that the increase in the air-filling fraction of a holey-fiber cladding results in a considerable enhancement of spectral br oadening of short laser pulses due to the increase in the light localizatio n degree in the fiber core.