Brian Kamer

HV discharge acceleration by sequences of UV laser filaments with visible and near-infrared pulses

We investigate the triggering and guiding of DC high-voltage discharges over a distance of 37 cm by filaments produced by ultraviolet (266 nm) laser pulses of 200 ps duration. The latter reduce the breakdown electric field by half and allow up to 80% discharge probability in an electric field of 920 kV m–1. This high efficiency is not further increased by adding nanosecond pulses in the Joule range at 532 and at 1064 nm. However, the latter statistically increases the guiding length, thereby accelerating the discharge by a factor of 2. This effect is due both to photodetachment and to the heating of the plasma channel, that increases the efficiency of avalanche ionization and reduces electron attachment and recombination.

Beam control through nonlinear propagation in air and laser induced discharges

Various models of filamentation in air are presented and the remaining theoretical challenges are pointed out. Means to extend the range of filaments are reviewed and proposed. Filaments offer promise of guiding electrical discharges over large gaps. Experiments of UV filament induced discharge are presented.

Carbon nanotubes for mode-locking: polarization study

Mode-locked fiber lasers are the most promising lasers for intracavity phase interferometry,1 because they offer the possibility to have two orthogonally polarized pulses circulating independently in the cavity. The saturable absorbers based on polarization maintaining tapered fiber coated with carbon nanotubes are developed and analyzed for minimum coupling between the slow and fast axis of the fiber.

Movies of filaments and plasma

Using a streak camera, and combining over 1,000 synchronized frames, 4D (2 D space, time in ps and wavelength) movies of the light and plasma emission in the wake of filaments are produced.