External focusing effect on terahertz emission from a two-color femtosecond laser-induced filament in air

Wang, T.-J.; Marceau, Claude; Yuan, Shuai; Chen, Y.; Wang, Q.; Théberge, F.; Châteauneuf, Marc; Dubois, Jacques; Chin, See Leang

doi:10.1002/lapl.201010088

Cited by 29 publications

(13 citation statements)

References 33 publications

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“…The analytical interference model of SC formation [16] reproduces the SC frequency angular spectrum transformation for the case of laser pulse splitting into several subpulses and for multiple refocusing of the light field during femtosecond laser pulse filamenta tion in dispersive media. The filamentation in air is accompanied with third harmonic generation [17], and two color filament in air is used for generation of terahertz radiation [18][19][20]. The unique properties of femtosecond laser radiation in filamentary regime reveal new opportunities for development of atmo spheric optic systems [21], pulse compression [22][23][24], micro optics elements [25], various devices for nonlinear optical conversion of laser radiation [13,26].…”

Section: Introductionmentioning

confidence: 99%

Spatio-temporal evolution scenarios of femtosecond laser pulse filamentation in fused silica

2012

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We investigated the evolution of femtosecond laser pulses at different wavelengths corresponding to normal, zero, and anomalous regimes of group velocity dispersion (GVD) in fused silica. The laser pulse filamentation in different GVD regimes under the same similarity parameters was first considered. It was established numerically that the scenario of the pulse filamentation depends both on temporal factors, which are determined by pulse GVD and self phase modulation, and spatial factors associated with Kerr self focus ing and plasma defocusing. In presence of strong normal GVD the dispersive stretching causes, a pulse power decrease followed by lowering of the intensity in filament, electron density reduction in plasma channel, and suppressing of the refocusing. For zero GVD the multipeak regime of radiation propagation is realized in the filament as a result of recurring self focusings of powerful pulse tail, which was defocused in laser plasma. When GVD is anomalous a sequence of "light bullets" with duration about 10 fs forms in the filament. And the peak intensity in "light bullet" stays the same ≈ 5 × 10 13 W/cm 2 . In the regime of anomalous GVD power is transferred from the pulse edges to its center, where the repeated self focusings occur and form a "light bul let" sequence.

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Section: Introductionmentioning

confidence: 99%

Spatio-temporal evolution scenarios of femtosecond laser pulse filamentation in fused silica

2012

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“…The measurements in this study are conducted with He-cooled bolometer having a HDPE filter mounted just before its 10 mm active area. Several reports have demonstrated through experiments and simulations that with sufficient laser energy, longer-focal-length lenses generate larger THz flux [37,61]. We conducted the experiment with 20, 30, 40, 50, and 70 cm focal length lenses.…”

Section: Thz Energy As a Function Of Lens Focal Lengthmentioning

confidence: 99%

Scaling up and parametric characterization of two-color air plasma terahertz source

et al. 2020

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The plasma produced by frequency mixing of an ultrafast pulsed laser and its secondharmonic field in air is a promising, table-top source of terahertz radiation. To maximize the generation efficiency of such a source, multi-parameter optimization is essential. A parametric study involving various external controls is presented here. Starting from the optimization of phase and polarization of the second-harmonic field, the effect of laser intensity on the terahertz flux is reported. Moreover, the effect of external focusing conditions, such as focal length of the lens and effect of laser beam aperture, is explored in detail. Contrary to the previous reports, we find that with the increase of laser intensity, terahertz (THz) flux increases with more conversion efficiency; this is attributed to the multiple ionization of the air, leading to stacked release of contributory electrons. Exploration of beam convergence reveals that relatively weaker focusing leads to increased terahertz production compared to sharp focusing conditions. Moreover, temporal characterization of the emitted terahertz pulse conducted using electro-optic sampling provides pulse duration of 368 fs with corresponding frequency spectra up to 3.6 THz. The maximum electric field of the terahertz pulse is estimated to be 1.12 MV cm −1 in our experimental conditions. Results of 2D particle-in-cell simulations are also presented with the objective of validating the role of transient photocurrent mechanism in THz generation from two-color laser-induced gas plasma. We believe the broadband, bright THz source presented here will be useful in the imaging of bigger samples as well as nonlinear spectroscopy.

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“…Two-color filamentation in air induced by a femtosecond Ti:sapphire laser pulse (fundamental wave, FW) and its second harmonic wave (SHW) has been demonstrated as an efficient technique to generate an intense THz emission [4][5][6][7][8][9][10][11][12][13][14][15][16]. THz electric field as high as 400 kV/cm [6] and a super-broadband THz spectrum up to 75 THz (λ = 4 μm) with μJ pulse energy [8] were reported.…”

Section: Introductionmentioning

confidence: 99%

Molecular alignment control of terahertz emission from a two-color filament in air

et al. 2011

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We demonstrate a method to control the terahertz (THz) emission from a two-color filament in air based on molecular alignment due to rotational Raman excitation. By tuning the delay time between rotational Raman excitation and THz excitation around the air molecule revival time, a significant modulation of THz emission is observed. The phenomenon is attributed to molecular alignment induced refractive index change, resulting in the changes of the nonlinearity (χ(3)) in neutrals and laser intensities inside the filaments.

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External focusing effect on terahertz emission from a two-color femtosecond laser-induced filament in air

Cited by 29 publications

References 33 publications

Spatio-temporal evolution scenarios of femtosecond laser pulse filamentation in fused silica

Spatio-temporal evolution scenarios of femtosecond laser pulse filamentation in fused silica

Scaling up and parametric characterization of two-color air plasma terahertz source

Molecular alignment control of terahertz emission from a two-color filament in air

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