Optical discharge propagation along hollow-core optical fibres

Propagation of an optical discharge along a revolver hollow-core optical fibre under the action of laser radiation is observed for the first time. As a source of radiation, a repetitively pulsed Nd : YAG laser with an average power up to 4 W, generating nanosecond trains of picosecond pulses, is used. After initiating an optical discharge, a motion of plasma formation along the optical fibre towards the laser beam at an average velocity of about 1 m s^-1 is observed. It is revealed that a quasi-periodic destruction structure of the fibre capillary reflective cladding with a period of about 170 μm is formed in the process of optical discharge propagation. The results obtained show that the optical discharge propagation observed in our experiments represents a process of periodic picosecond pulse excitation of a light detonation wave in the air filling the core. As a result, during the action of a train of nanosecond laser pulses, the optical discharge moves along the fibre with a velocity in the range from 100 to 10 km s^-1.