Helical plasma filaments from the self-channeling of intense femtosecond laser pulses in optical fibers
F. Mangini, M. Ferraro, M. Zitelli, A. Niang, T. Mansuryan, A. Tonello, V. Couderc, A. De Luca, S. A. Babin, F. Frezza, S. Wabnitz
Abstract
We experimentally and numerically study the ignition of helical-shaped plasma filaments in standard optical fibers. Femtosecond pulses with megawatt peak power with proper off-axis and tilted coupling in the fiber core produce plasma skew rays. These last for distances as long as 1000 wavelengths thanks to a combination of linear waveguiding and the self-channeling effect. Peculiar is the case of graded-index multimode fibers; here the spatial self-imaging places constraints on the helix pitch. These results may find applications for fabricating fibers with helical-shaped core micro-structuration as well as for designing laser components and three-dimensional optical memories.