Guiding microwave radiation using laser-induced filaments: the hollow conducting waveguide concept

Abstract

A microwave waveguide that consists of a set of laser plasma filaments produced in air by the propagation of femtosecond laser pulses is investigated according to the hollow conducting waveguide concept. The conductivity, skin depth of the electromagnetic waves in this plasma waveguide and the energy required to excite such a waveguide are calculated for different possible configurations. A hollow conducting plasma waveguide is shown to support guided modes of electromagnetic radiation from millimetre to centimetre wavelength range. Our calculations show that, under the concept of conducting waveguide, it is more suitable to use the TE01 mode rather than TE11 to achieve an extended attenuation length. The attenuation length of the low-loss mode TE01 is shown to be dependent on the geometry of the plasma waveguides, the operating frequency and the plasma effective electron density. The effect of the plasma wall density spread on TE01 propagation is evaluated. Using the hollow conducting plasma waveguide operating in TE01 mode, an enhancement of microwave transmission over both free space propagation and dielectric plasma waveguide is obtained.