Analysis of microwave leaky modes propagating through laser plasma filaments column waveguide

A plasma column waveguide formed by a bundle of closely spaced plasma filaments induced by the propagation of ultrafast laser pulses in air and revived by a longer infrared laser pulse is shown to support microwave radiation. We consider values of both the plasma electron density and microwave frequency for which the refractive index of plasma is lower than the refractive index of air; therefore, a leaky plasma waveguide can be realized in extremely high frequency band. The guiding mechanism does not require high conductance of the plasma and can be easily excited by using commercial femtosecond laser sources. A theoretical study of leaky mode characteristics of isotropic and homogeneous plasma column waveguides is investigated with several values of plasma and waveguide structure parameters. The microwave transmission loss was found to be mainly caused by the microwave leakage through the air-plasma interface and is weakly dependent on the plasma absorption. In spite of losses of microwaves caused by leakage and plasma absorption, it is shown to be much lower than both that accompanying to surface waves attaching to single conducting plasma wire and the free space propagation over distances in the order of the filament length, which opens exciting perspectives for short distance point to point wireless transmission of pulsed-modulated microwaves.