Electromagnetic (EM) Wave Attachment to Laser Plasma Filaments

摘要

This report explores the theoretical and experimental analysis of using plasma filaments generated by a femtosecond class laser system as a means for transmission of radio frequency (RF) electromagnetic (EM) waves. Theoretically, the plasma filaments are modeled as complex cylindrical wires in space for single and dual wire configurations. Attenuation as a function of distance is calculated for single wire transverse electric mode propagation and dual wire transverse electromagnetic (TEM) mode propagation. Minimum attenuation is shown to be dependent on filament diameter, electron density, and filament separation (for the dual wire case). Initial experimental validation of theoretical models is performed with copper wire filament surrogates. Radio frequency/plasma filament interaction is then demonstrated in a rectangular waveguide fixture. Filament electron density enhancement is demonstrated in cylindrical resonant RF cavities (2.6 GHz and 0.9 GHz) where an increase in pulse width of attached EM waves beyond lifetimes of typical ultrafast laser generated plasma filaments is observed. Transmission of RF energy out of resonant cavities along a filament is demonstrated further validating transmission theory.