The interaction of polarized microwaves with planar arrays of femtosecond laser-produced plasma filaments in air

Abstract

The interaction of polarized microwaves with subwavelength arrays of parallel plasma filaments, such as those produced by the propagation of high-power femtosecond laser pulses in ambient air, was investigated by calculating the reflection and transmission coefficients as a function of the incidence angles using the finite-difference time-domain (FDTD) method. The time evolution of these coefficients was calculated and compared with experiments. It is found that the plasma filaments array becomes transparent when the polarization of the microwave radiation is perpendicular to the filaments axis, regardless the incidence angle of the microwave with respect to the filaments, except near grazing incidence. Increasing the filaments electron density or diameter, or decreasing the electron collision frequency or filaments spacing, decreases the transmission and increases the reflection. Transmission decreases when increasing the number of filament layers while reflection remains unchanged as the number of filament layers exceeds a given number ($3 in our case). Transmission slightly increases when disorder is introduced in the filament arrays. The detailed calculation results are compared with those obtained from the simple birefringent slab model, which provides a convenient framework to calculate approximately the properties of filament arrays.

Free-space components for microwave transmission

“…Characterizing the geometry of filaments, and the distribution of free electrons therein, during the process of VHMM formation, along with quantitative analysis of the influence of structural inhomogeneity on the performance of VHMMs, are the foci of our current work, and are planned to be published in further articles. Finally, we note that while recently the first studies of the interactions of microwave radiation with the arrays of filaments have been reported by Merian et al [38], further studies including pulsed microwave radiation interactions with filaments are necessary. In this work, we have considered several different applications of VHMM structures for microwave signal manipulation.…”

Dynamics of Large Femtosecond Filament Arrays: Possibilities, Limitations, and Trade-Offs

“…Propagation over such long distances is a result of the dynamic balance between the focusing Kerr nonlinearity, diffraction, and plasma defocusing due to multiphoton absorption. A proper arrangement of plasma channels into arrays built of multiple filaments can lead to control and efficient guiding of electromagnetic radiation in air . Dielectric and hollow-core metallic waveguide configurations , were predicted theoretically and demonstrated experimentally to guide microwave radiation.…”

Virtual hyperbolic metamaterials for manipulating radar signals in air

“…Although this approach offers a way to counteract the diffraction of a radar signal over some distance, the issues of beam steering and coupling microwave signals into such waveguides are likely to be challenging. Finally, very recently, Marian et al 6 reported parametric studies of interactions of microwaves with subwavelength arrays of parallel plasma filaments. Although these studies elucidated reflection and transmission properties of various periodically and randomly arranged filament arrays, no specific physical mechanism enabling guiding, focusing or steering of the microwave beam was discussed.…”