Exotic nonlinear phenomena in optical fibers: from helical plasma beams to rainbow spiral emission

Mario Ferraro

Sapienza University of Rome -

We discuss the spontaneous appearance of exotic nonlinear phenomena, occurring in standard optical fibers when femtosecond laser pulses propagate at intensities close to and above the critical intensity for material breakdown. This regime is characterized by nonlinear phenomena such as supercontinuum generation and self-channeling plasma ignition. Interestingly, the cylindrical fiber geometry can be exploited to provide a helical shape to plasma filaments. By appropriate control of laser/fiber coupling, we were able to produce plasma skew rays, which can propagate over 1,000 wavelength distances without suffering diffraction spreading. When laser pulses are injected in the cladding of few centimeters long fiber spans, one may spontaneously produce the emission of a spiral beam in the far field. Remarkably, in the high-power regime, the colors of the supercontinuum generation self-organize in space, giving rise to a naked-eye visible rainbow spiral emission from the fiber output tip.

Related paper: https://arxiv.org/abs/2010.00487