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

Abstract

Stable propagation of large, multifilament arrays over long distances in air paves new ways for microwave-radiation manipulation. Although, the dynamics of a single or a few filaments was discussed in some of the previous studies, we show that the stability of large plasma filament arrays is significantly more complicated and is constrained by several trade-offs. Here, we analyze the stability properties of rectangular arrays as a function of four parameters: relative phase of the generating beams, number of filaments, separation between them, and initial power. We find that arrays with alternating phase of filaments are more stable than similar arrays with all beams in phase. Additionally, we show that increasing the size of an array increases its stability, and that a proper choice of the beam separation and the initial power has to be made in order to obtain a dense and regular array of filaments. PACS numbers: 52.38.Hb, 42.65.Sf, 42.65.Tg, 42.65.Jx High-power femtosecond laser-pulse filamentation is a flourishing field of nonlinear optics due to its numerous applications in remote sensing, lightning protection, virtual antennas, and waveguiding [1][2][3]. Experiments show that a femtosecond laser beams can ionize atmosphere at the kilometer-scale distances [4]. 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 [5] and efficient guiding of electromagnetic radiation in air [6]. Dielectric [7] and hollow-core metallic waveguide configurations [8,9] were predicted theoretically and demonstrated experimentally [10] to guide microwave radiation. Periodic arrays of densely packed high-intensity filaments were shown to create a hyperbolic metamaterial medium, that allows for radar signal manipulation and resolution enhancement [11,12].Formation of desired, regular filament patterns requires precise control of filament distribution and interaction. Multiple filaments can be generated by an intense Gaussian beam [13,14], whose power is much higher than the critical power of self-focusing P cr . However, the distribution of filaments resulting from the breakup of a Gaussian beam is determined by intensity fluctuations [15] and modulation instability [16,17]. Moreover, the density of filaments generated in this way is limited [18,19]. Therefore, this method can not provide the fine control and the high filament density required for the microwave-radiation manipulation. A certain degree of control of the filament distribution can be obtained by special preparation of the Gaussian beam. It was demonstrated experimentally that the predetermined initial phase [20,21], amplitude distribution [15], and geometry of the beam [22] offer a limited control of the filamentation pattern. The filament distribution in an array can be even more deterministic if the position of each beam is managed independentl...

Filamentation‐Induced Volume Plasma Grating: Dynamics, Possibilities, and Advantages

“…In this sense, filaments originated from the constructed plasma waveguides pre-define perturbations at the cross section of the beam, which have less shot-to-shot deviation of their transverse positions as compared with the self-formation of multiple filamentation. [14,30] It is noteworthy that the volume plasma grating inherited the advantage of planar plasma gratings with enhanced light field intensity. [23][24][25][26] Stronger intensity was observed in case of the volume plasma grating, if we compared the intensities along x direction in Figure 2a with those in Figure 2b.…”

“…On the other hand, stable propagation of arrays of multiple filaments via volume plasma gratings creates homogeneously distributed plasma channels (waveguides) in the wake of the pulse, which might open possibilities microwave-radiation manipulation and telecommunication. [14] A few advantages of volume plasma grating are obvious. First, cross-scale manufacturing can be achieved via volume plasma gratings.…”

“…This evolution is governed by the stability of child filaments in the array and by the mutual interaction between the adjacent child filaments. [14] If it is achiev-able, perhaps we are able to make use of multiple filamentation generation, other than deliberately avoid it. Besides, although studies of planar plasma grating [23][24][25][26] and other techniques to control multiple filaments [27][28][29][30][31][32] might offer us a basic tool for laser modification/ablation, the dimensions of plasma grating are still expected to be increased for further improvements of cross-scale manufacturing.…”

Invisibility Cloak in Microwave Region Using Double Negative Meta-materials and Their Various Applications

“…It is a legit endeavor to avoid inessential scattering of waves in the atmosphere while their transmission that leads to divergence. A class of metamaterials named as VHMMs(Virtual Hyperbolic Meta Materials) is introduced in order to orchestrate or manipulate beam in microwave region, its construction comprises of an assembly (array) of channels consisting of plasma in atmosphere attained by self converging and hence focusing of a laser pulse with high intensity [50,51,52,53].…”

“…The formation of such structure can be utilized in order to collocate the laser beam quite efficiently and for shifting or enrouting the signals transmitted from radar around the target or any obstacle [52,53,54,55,56].…”