Filamentation of IR and UV femtosecond pulses upon focusing in air

Dergachev, A A; Ионин, А. А.; Kandidov, V.P.; Селезнев, Л. В.; Sinitsyn, D. V.; Sunchugasheva, E. S.; Shlenov, S. A.

doi:10.1070/qe2013v043n01abeh015007

Cited by 25 publications

(24 citation statements)

References 26 publications

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“…As was also shown in Ref. [12], where process of filamentation and plasma channels formation was compared for focused IR and UV ultrashort pulses, that plasma channel characteristics (shape, geometry size, plasma density, etc.) strongly depend on radiation wavelength.…”

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confidence: 54%

Plasma channels under filamentation of infrared and ultraviolet double femtosecond laser pulses

et al. 2013

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An influence of plasma channel created by a filament of focused UV or IR femtosecond laser pulse (λ=248 nm or 740 nm) on characteristics of other plasma channel formed by a femtosecond pulse at the same wavelength following the first one with varied nanosecond time delay was experimentally studied. A dependence of optical transparency of the first channel and plasma density of the second channel on the time delay was demonstrated to be quite different for such a double UV and IR femtosecond pulses.Propagation of a femtosecond laser pulse with overcritical power through transparent medium results in self-focusing and plasma channels formation (process of filamentation [1,2]). Currently, filamentation phenomenon has wide practical application, in particular, for controlling high-voltage electric discharge [3][4][5][6][7][8] by plasma channels formed by filaments. Two sequential femtosecond pulses (i.e. a double femtosecond pulse) of infrared radiation were used to control electric discharge in [9]. An opportunity of increasing the efficiency of high-voltage discharge control with additional sequential nanosecond pulse was demonstrated in [6]. The first pulse created cold low density plasma, while the second pulse heated the plasma and increased photodetachment of electrons that reduced the breakdown discharge voltage. It was also reported in papers [8,10,11] that conductivity of a long plasma channel was effectively sustained by a train of UV or IR ultrashort pulses. Obviously, the efficiency of plasma channel formation and supporting electron concentration by a train of ultrashort laser pulses depends on the fact how plasma channel formed by a previous laser pulse influences upon filamentation of the subsequent pulse and its plasma channel formation. As was also shown in Ref. [12], where process of filamentation and plasma channels formation was compared for focused IR and UV ultrashort pulses, that plasma channel characteristics (shape, geometry size, plasma density, etc.) strongly depend on radiation wavelength. For the time being, studying parameters of plasma channels formed by focused double femtosecond laser pulse and comparing the results obtained for such a pulse of different (IR and UV) spectral bands has not been conducted. In this paper, an influence of plasma channel created by a filament of focused femtosecond laser pulse (λ=248 nm or 740 nm) on characteristics of other plasma channel formed by a femtosecond pulse at the same wavelength following the first one with varied nanosecond time delay was experimentally studied.Plasma channel parameters formed by a double laser pulse consisting of two sequential ultrashort pulses were experimentally studied by using a Ti-sapphire femtosecond laser system. Laser pulses of 100 fs pulse duration (FWHM) following with 10 Hz repetition rate at the wavelengths of 248 nm and 744 nm with the laser beam radius of 4 mm (e -1 level) were used. The laser pulse peak power was as high as a few self-focusing critical power (P cr ~ 3-5 GW for 744 nm, P cr ~ 100 MW for 248 n...

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confidence: 54%

Plasma channels under filamentation of infrared and ultraviolet double femtosecond laser pulses

et al. 2013

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“…Filamentation of a focused beam was studied for the first time in [3], when the filament was registered in the cuvette with noble gases beyond the geometrical focus of MgF 2 lens with focal length of 2 m. Experiments [4] demonstrated that very tight focusing led to the suppression of the filamentation and generation of dense plasma region near the geometrical focus. Experimental and numerical study of the air filamentation of tightly focused beams [5] and its dependence on the focusing of IR and UV pulses [6] showed that plasma channels passed through the beam focal plane. The transverse beam size has no effect on the length of the channel in a tightly focused beam if the initial peak intensity remains constant [7].…”

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confidence: 99%

The influence of the energy reservoir on the plasma channel in focused femtosecond laser beams

et al. 2015

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The influence of the energy reservoir on plasma channel formation during the filamentation of tightly focused femtosecond laser beams was studied both experimentally and numerically. It was found that for the reservoir localized near the propagation axis, its diameter is much smaller than in the case of a collimated beam and decreases in the vicinity of the focus. A small diaphragm placed in the focal area does not eliminate the plasma channel behind the focal point.

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“…The plasma channel of IR filament is terminated soon after the focal plane of the lens whereas the plasma channel of UV filament survives beyond this plane. However, the peaks in the distribution of the electron density in the plasma channel of IR filament in numerical simulation, associated with the effect of refocusing, were not reproduced in the experiment 20 probably due to the averaging of the signal over the aperture of the electrodes with characteristic size of a few centimeters.…”

Section: Comparative Analysis Of the Ir And Uv Filamentsmentioning

confidence: 67%

Femtosecond laser filament and plasma channels in focused beam in air

Shlenov

Dergachev

Ионин

et al. 2015

18th International School on Quantum Electronics: Laser Physics and Applications

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The filamentation of focused beams at wavelength of 800 and 248 nm in air is studied experimentally and numerically.The results indicate that relatively tight focusing can lead to the coalescence of individual regions of high fluence and high plasma density that result from multiple refocusing, whereas in the case of weak focusing such regions are separated in the pulse propagation direction. The lower multiphoton ionization order in the case of UV radiation leads to a stronger effect of geometric focusing on filament formation. We show the possibility to control the parameters of femtosecond laser plasma filaments by introducing astigmatism in laser beam wavefront. Strong astigmatism can lead to the splitting of the channel into two separate regions. We demonstrate that the self-phase modulation in the thin passthrough dielectric plate decreases the distance to the filament start in air and increases the length of plasma channel.

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Filamentation of IR and UV femtosecond pulses upon focusing in air

Cited by 25 publications

References 26 publications

Plasma channels under filamentation of infrared and ultraviolet double femtosecond laser pulses

Plasma channels under filamentation of infrared and ultraviolet double femtosecond laser pulses

The influence of the energy reservoir on the plasma channel in focused femtosecond laser beams

Femtosecond laser filament and plasma channels in focused beam in air

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