Directed transfer of microwave radiation in sliding-mode plasma waveguides produced by ultraviolet laser in atmospheric air

Abstract

Experiments have been performed at hybrid Ti:sapphire/KrF laser facility GARPUN-MTW to develop a novel technique to create a hollow-core sliding-mode plasma-filament waveguide for directed transfer of microwave radiation. Efficient multiphoton air ionization was produced by a train of picosecond 1-TW UV pulses at 248 nm wavelength, or by amplitude-modulated 100 ns pulse combining a short-pulse train with a free-running 1-GW pulse, which detached electrons off O2- ions. Multiple filamentation of UV laser radiation in air was observed, and filamentation theory based on resonance-enhanced ionization was developed to explain the experimental results.

Multiple filamentation of supercritical UV laser beam in atmospheric air

“…Although peak power of $10 TW obtained at large-scale e-beam-pumped KrF facilities exceeds by 5 orders of magnitude the critical power P cr % 0.1 GW for k = 248 nm, no evidences of the UV laser beam filamentation, as well as of nonlinear absorption or phase-modulation were reported in those experiments [6][7][8][9]. On the contrary, in our experiments at GARPUN-MTW Ti:Sapphire/KrF laser facility a multiple filamentation was clearly observed for output UV radiation with a peak power P $1 TW and sub-ps pulse length [18][19][20][21]. A block structure of CaF 2 windows of the final KrF amplifier introduced phase modulation at block boundaries that initiated filamentation of the output beam.…”

Simulation analysis of the HPM propagation along the femtosecond laser plasma double-line

“…Moreover, the interaction can cause the energy transferred from HPM to electrons of the plasma, so that the energy of electrons will lose by the collision of electrons and neutral particles. On the other hand, the conductivity is inversely proportional to the collision frequency as can be seen from formula (2). It is obvious that the smaller the collision frequency, the greater the plasma conductivity and the better the transmission performance of the double-line.…”

“…In recent years, the femtosecond laser technology has attracted great interests of researchers all over the world in 1 the past two decades [1][2][3][4][5] . The high power femtosecond laser can produce plasma filaments in the atmosphere under the dynamic balance between diffraction, dispersion, Kerr nonlinearity and multiple photons ionization, which has been widely used in different applications, such as generating terahertz (THz) radiation [6] , broadening the laser emission spectrum [7] , long-range detection, laser remote sensing, and guiding the forceful lightnings in rainstorm [8] .…”

A New Insight into High-Aspect-Ratio Channel Drilling in Translucent Dielectrics with a KrF Laser for Waveguide Applications

“…For example, the inertially confined fusion with thermonuclear fuel ignition by a strong shock wave (SI ICF) demands a laser pulse of 10–20 ns length and a very sharp rise of power by about two orders of magnitude during the last 200 ps [ 45 ]. The production of long, weakly ionized plasma channels in atmospheric air by UV laser intended for the triggering and guiding of high-voltage (lightning) discharges [ 46 ], or directed transfer of microwaves along plasma waveguides [ 47 ], are the most effective using rather long high-energy pulses of hundred nanoseconds length superimposed with high-power subnanosecond pulses. These pulse forms can be obtained by combining short ( τ sh ≤ τ c ) and long ( τ long ≥ τ c ) pulses when they are simultaneously amplified in KrF gain medium with the gain recovery time τ c ≈ 2 ns [ 48 ].…”