Transverse modal instability in liquid-core waveguides.

Nonlinear propagation of few-ps and sub-ps pulses in multimode liquid-core waveguides is investigated numerically. A transverse modal instability phenomenon, akin to those observed in high-power fiber amplifiers, is identified and characterized. Contrary to the case of amplifiers, the origin of the instability is the delayed-response nonlinearities characteristic of liquids, rather than thermo-optic effects. Implications for nonlinear applications are briefly discussed.