Microwave guiding in air by a cylindrical filament array waveguide

Abstract

Microwave guiding was demonstrated over 16cm in air using a large diameter hollow plasma waveguide. The waveguide was generated with the 100TW femtosecond laser system at the Advanced Laser Light Source facility. A deformable mirror was used to spatially shape the intense laser pulses in order to generate hundreds of filaments judiciously distributed in a cylindrical shape, creating a cylindrical plasma wall that acts as a microwave waveguide. The microwaves were confined for about 10ns, which corresponds to the free electron plasma wall recombination time. The characteristics of the plasma waveguide and the results of microwave guiding are presented.

Coherent synthesis of terahertz radiation from femtosecond laser filaments in air

“…5(d), where its peak intensity is found to be ~ 250 times that of a single filament. Recently, M. Châteauneuf and coworkers have reported the generation of 10 3 filaments organized in a circle [26]. With proper phase control, it could lead to a 10 6 increase of THz peak intensity.…”

“…The good agreement between our experimental observations and calculations validates the theoretical model and permits to extrapolate the results to a higher number of filaments. It has been demonstrated that a large number of filaments can be organized in regular patterns by manipulation of the beam profile of a femtosecond laser pulse with P >> P cr [24][25][26]. We have calculated the THz radiation distribution for N = 4, 6, 8, 9, 12, 16 filaments organized in a square grid.…”

Long-lived waveguides and sound-wave generation by laser filamentation

“…Experimental data about the long term dynamics is especially scarce. The filamenting pulse leaves behind free electrons at initial densities of 10 16 -10 17 cm -3 [2,3], mostly from multi-photon ionization of oxygen molecules because the ionization potential of N 2 molecules is significantly larger (12 eV and 16 eV for O 2 and N 2 , respectively). Initially, the free electron density exhibits a radial bell-shape profile.…”

Radiofrequency plasma antenna generated by femtosecond laser filaments in air

“…A pioneer work demonstrated the feasibility of radiofrequency (RF) plasma using a nanosecond laser to induce a discharge in air 1 . More recently attention has been paid to the potentiality of femtosecond filamentation for guiding microwave radiation under atmospheric conditions [9][10][11][12] . During filamentation [13][14][15] a weakly ionized plasma column is created in the wake of an intense fs laser pulse, with an initial electron density of ~ 10 16 cm -3 , a  100 µm diameter and a nanosecond recombination time 16 .…”