Molecular quantum wakes for clearing fog

Abstract

High intensity laser filamentation in air has recently demonstrated that, through plasma generation and its associated shockwave, fog can be cleared around the beam, leaving an optically transparent path to transmit light. However, for practical applications like free-space optical communication (FSO), channels of multi-centimeter diameters over kilometer ranges are required, which is extremely challenging for a plasma based method. Here we report a radically different approach, based on quantum control. We demonstrate that fog clearing can also be achieved by producing molecular quantum wakes in air, and that neither plasma generation nor filamentation are required. The effect is clearly associated with the rephasing time of the rotational wave packet in N 2 .Pump excitation provided in the form of resonant trains of 8 pulses separated by the revival time are able to transmit optical data through fog with initial extinction as much as −6 dB.

Opto-mechanical expulsion of individual micro-particles by laser-induced shockwave in air

“…Both can be used for the positioning of the filament and the calculation of the separation distance between it and the trapped sphere. The snapshot shown in Figure 3 shows the cylindrical symmetry of the acoustic wave, as previously observed in similar shadowgraphy experiments 23,36 . The range of the effect was investigated for different particle-filament distances and observed up to 5.5 mm.…”

“…An alternative to plasma induced heating was recently proposed by Schroeder et al 23 : the coherent control of the molecular rotation of nitrogen molecules. Control was obtained by Raman exciting N2 with a train of femtosecond pulses with an adjustable inter-pulse period 24 .…”

Control of Femtosecond Filamentation by Means of the Alignment of Gas Molecules by Short-Wavelength Infrared Laser Pulses

“…Therefore, the second femtosecond pulse can propagate synchronously with the quantum wake region for a sufficiently long time so that the effect of the first-pulse induced change in the refractive index on the filamentation of the second pulse is strongly enhanced. Thus, the laser-induced nonadiabatic alignment of molecules in gases opens the possibility for control of the state of atmospheric lines for transmission of laser radiation [12], for the creation of lasing conditions on nitrogen ions upon filamentation in air [13], and for control of the generation of the supercontinuum and high order harmonics for an increase in the electron density in plasma channels of the filament and the further compression of pulses [7,14]. The experimental studies of the effect of the preliminary alignment of molecules on the features of filamentation showed…”

Cumulative Effects in 100 kHz Repetition‐Rate Laser‐Induced Plasma Filaments in Air

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When ultrashort intense laser pulses propagate in optically transparent media, such as in air, intensity-dependent nonlinear effects, for example, Kerr focusing, absorption, and gas ionization, lead to pulse reshaping and the formation of filaments, which can sustain nonlinear effects over several tens of meters. [1,2] Laser filamentation in ambient air has attracted considerable attention in recent years owing to its central role in several applications, such as the formation of stationary localized waves, [3] electric-discharge steering, [4][5][6] machining, [7] control and guiding of lightning, [8][9][10][11] atmospheric control, [12][13][14] remote sensing, [15][16][17] pulse compression, [18] optical communication, [19][20][21][22] and the generation of coherent radiation in hardly accessible spectral regions such as the deep UV and THz. [23][24][25][26][27][28][29] Filaments modify the gas density in which they propagate through different nonlinear light-matter interaction pathways, such as by excitation of molecular

…”

“…This long-lasting effect is responsible for the low-density gas channel that accompanies filamentation [33][34][35] and plays a dominant role in the triggering and steering of high-voltage discharges and lightning control. [36][37][38][39] The temporary reduction of the density was also shown to enable energy transfer via air-waveguide guided lasers, [34] to open communication channels through fog, [19,20] and may be employed to improve remote spectroscopy. [40] Common sources employed for filamentation are Ti:Sapphireamplified lasers with high pulse energies (>10 mJ) and low repetition rates (≤1 kHz).…”