共查询到20条相似文献,搜索用时 562 毫秒
1.
S.-Y. Cao W.-P. Kong Z. Wang Z.-M. Song Y. Qin R.-X. Li Q.-Y. Wang Z.-G. Zhang 《Applied physics. B, Lasers and optics》2009,94(2):265-271
A novel technique of controlling the evolution of the filamentation was experimentally demonstrated in an argon gas-filled
tube. The entrance of the filament was heated by a furnace and the other end was cooled with air, which resulted in the temperature
gradient distribution along the tube. The experimental results show that multiple filaments are merged into a single filament
and then no filament by only increasing the temperature at the entrance of the filament. Also, the filament can appear and
disappear after increasing the local temperature and input pulse energy in turn. This technique offers another degree of freedom
to control the filamentation and opens a new way for multi-mJ level monocycle pulse generation through filamentation in the
noble gas. 相似文献
2.
Femtosecond laser filamentation is particularly interesting for remote sensing pollutant in the atmosphere. In this work, we investigate the local shot-to-shot stability of the filament induced fluorescence of nitrogen in air. It is found that the root-mean square fluctuation of the fluorescence signal is at least one order of magnitude lower than that of the linear propagation case. In practice, it would contribute to improve the robustness of long distance spectroscopic analysis of the fluorescence of pollutant molecules inside the filament. We further point out that this unique property of filament induced fluorescence spectroscopy is because of the intensity clamping, a profound phenomenon of filamentation. 相似文献
3.
W. Liu J.-F. Gravel F. Théberge A. Becker S. L. Chin 《Applied physics. B, Lasers and optics》2005,80(7):857-860
We report an experiment to demonstrate the crucial effect of the so-called background reservoir during the propagation of femtosecond laser pulses in air. The background reservoir was blocked by allowing only the filament to pass through a pinhole generated by the filament itself in an aluminum foil. We observed that the filamentation process is terminated immediately after the pinhole. Consequently, to achieve long-range filamentation, it is necessary to maintain the dynamic energy exchange between the reservoir and the self-foci. 相似文献
4.
G. Méchain G. Méjean R. Ackermann P. Rohwetter Y.-B. André J. Kasparian B. Prade K. Stelmaszczyk J. Yu E. Salmon W. Winn L. A. Schlie A. Mysyrowicz R. Sauerbrey L. W?ste J.-P. Wolf 《Applied physics. B, Lasers and optics》2005,80(7):785-789
The propagation of femtosecond terawatt laser pulses at reduced pressure (0.7 atm) is investigated experimentally. In such
conditions, the non-linear refractive index n
2 is reduced by 30%, resulting in a slightly farther filamentation onset and a reduction of the filament number. However, the
filamentation process, especially the filament length, is not qualitatively affected. We also show that drizzle does not prevent
the filaments from forming and propagating. 相似文献
5.
W. Liu O. Kosareva I.S. Golubtsov A. Iwasaki A. Becker V.P. Kandidov S.L. Chin 《Applied physics. B, Lasers and optics》2003,76(3):215-229
The competition between femtosecond laser pulse induced optical breakdown and femtosecond laser pulse filamentation in condensed
matter is studied both experimentally and numerically using water as an example. The coexistence of filamentation and breakdown
is observed under tight focusing conditions. The development of the filamentation process from the creation of a single filament
to the formation of many filaments at higher pulse energy is characterized systematically. In addition, strong deflection
and modulation of the supercontinuum is observed. They manifest themselves at the beginning of the filamentation process,
near the highly disordered plasma created by optical breakdown at the geometrical focus.
Received: 9 July 2002 / Revised version: 15 November 2002 / Published online: 19 March 2003
RID="*"
ID="*"Corresponding author. Fax: +1-418/6562-623, E-mail: wliu@phy.ulaval.ca 相似文献
6.
F. Théberge W. Liu S. A. Hosseini Q. Luo S. M. Sharifi S. L. Chin 《Applied physics. B, Lasers and optics》2005,81(1):131-134
The distance-resolved spectral intensity distribution of the backscattered light from long filaments generated in air using ultra-short and intense laser pulses is presented. A clean fluorescence spectrum from N2 molecules and ions, which is produced by the high peak intensity inside the plasma filament of the fundamental pulse, was clearly resolved from the backscattered supercontinuum. The supercontinuum generated by both the fundamental and the third-harmonic pulses developed progressively and became fully developed only at the end of the filamentation. 相似文献
7.
We present experimental studies of filamentation of a femtosecond laser pulse in air at low pressures. The evolution of the filament has been studied by measuring along the propagation axis the conductivity and the sub-THz emission from the plasma channel. We show experimentally that the filamentation process occurs at pressures as low as 0.2 atm in agreement with numerical simulations. Experimental and numerical results [A. Couairon, M. Franco, G. Méchain, T. Olivier, B. Prade, A. Mysyrowicz, Opt. Commun., submitted for publication] are compared and the possible sources of discrepancy are discussed. 相似文献
8.
V. Jukna G. Tamo?auskas G. Valiulis M. Aputis M. Puida F. Ivanauskas A. Dubietis 《Applied physics. B, Lasers and optics》2009,97(1):175-179
We have studied filamentation of 1-ps laser pulses in a scattering medium (aqueous suspension of 2-μm polystyrene microspheres)
and compared filamentation dynamics to that in pure water. Our results indicate that light scattering does not alter filamentation
dynamics in general, but rather results in farther position of the nonlinear focus, shorter filament length, and the development
of speckle structure in the peripheral part of the beam. The experimental observations are qualitatively reproduced by the
numerical model which accounts for diffraction, self-focusing, multiphoton absorption, and light scattering introduced through
a stochastic diffusion and diffraction term. 相似文献
9.
Influence of Initial Pulse Chirp on Rainbow-Like Supercontinuum Generation from Filamentation in Air
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Supereontinuum (SC) generation from laser filamentation in air is found to depend strongly on the pulse duration. Rainbow-like SC generation is observed only for a pulse of appropriate negative chirp that agrees with the predictions put forward by Golubtsov et al. [Quantum Electron. 33 (2003) 525]. The conversion efficiency of an 800-nm laser light to rainbow-like SC is found to be the highest for 257fs pulses with an initial negative chirp. A larger chirp will lead to filamentation surviving at longer distance. 相似文献
10.
S.L. Chin A. Talebpour J. Yang S. Petit V.P. Kandidov O.G. Kosareva M.P. Tamarov 《Applied physics. B, Lasers and optics》2002,74(1):67-76
Formation and wandering of filaments in air are studied both experimentally and numerically. Filament-center deflections are
collected from 1100 shots of 190-fs and 800-nm pulses in the plane perpendicular to the propagation direction. To calculate
the filament wandering in air we have developed a model of powerful femtosecond laser pulse filamentation in the Kolmogorov
atmospheric turbulence and employed the Monte Carlo method to model the propagation of several hundred laser pulses. Statistical
processing of experimental and numerical data shows that filament-center displacements in the transverse plane obey the Rayleigh-distribution
law. Parameters of the Rayleigh distribution obtained for numerical and experimental data are close to each other.
Received: 23 May 2001 / Revised version: 26 September 2001 / Published online: 29 November 2001 相似文献
11.
We investigate numerically the influence of the pressure on femtosecond filamentation in air. We show that femtosecond filamentation occurs at low pressure and compute the features of the plasma channel generated in the wake of the pulse. We discuss the influence of the pulse duration, chirp and input beam shape on the length of the plasma channels. These calculations constitute a prerequisite for laboratory experiments over short distances as well as for vertical femtosecond filamentation at high altitude on which light detection and ranging techniques or lightning protection rely. 相似文献
12.
Schulz E Steingrube DS Vockerodt T Binhammer T Morgner U Kovačev M 《Optics letters》2011,36(22):4389-4391
The third harmonic generated during femtosecond filamentation in air is studied. By establishing a gradient from atmospheric pressure to vacuum conditions, we truncate the filament abruptly at defined positions. The introduction of the pressure gradient leads to an enhancement of the generated third harmonic radiation by 3 orders of magnitude. This effect is attributed to an improved on-axis phase-matching condition. We investigate the spectral shape and the conversion efficiency of the third harmonic during the propagation in the filament. 相似文献
13.
In this work we numerically compare the interaction of optical vortices (OVs) in self-defocusing and self-focusing Kerr nonlinear media. We find that the basic scenarios (attraction/repulsion, translation/rotation vs. background) in the interaction of two and three vortices with equal and alternative topological charges (TCs) are the same in both media. However, the vortex dynamics under self-focusing conditions is influenced by the reshaping of the surrounding part of the background. Square structure of OVs with alternating TCs is found to be stable with respect to the vortex positions in self-focusing media. This elementary cell is successfully generalized in a large square array of OVs with alternative TCs which brings ordering in the multiple filamentation of the background beam in self-focusing conditions. 相似文献
14.
Random deflection of the white light beam during self-focusing and filamentation of a femtosecond laser pulse in water 总被引:1,自引:0,他引:1
W. Liu O. Kosareva I.S. Golubtsov A. Iwasaki A. Becker V.P. Kandidov S.L. Chin 《Applied physics. B, Lasers and optics》2002,75(4-5):595-599
Ti:sapphire femtosecond laser pulse filamentation in competition with optical breakdown in condensed matter is studied both
experimentally and numerically using water as an example. Strong random deflection and modulation of the supercontinuum under
tight focusing conditions were observed. They manifest the beginning of the filamentation process near the highly disordered
plasma created by optical breakdown at the geometrical focus.
Received: 13 June 2002 / Revised version: 16 August 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +1-418/656-2623, E-mail: wliu@phy.ulaval.ca 相似文献
15.
Supercontinuum generation by femtosecond filaments in air is investigated for different laser wavelengths ranging from ultraviolet to infrared. Particular attention is paid on the role of third-harmonic generation and temporal steepening effects, which enlarge the blue part of the spectrum. A unidirectional pulse propagation model and nonlinear evolution equations are numerically integrated and their results are compared. Apart from the choice of the central wavelength, we emphasize the importance of the clamped intensity reached by self-guided pulses, together with their temporal duration and propagation length as key players acting on both supercontinuum generation of the pump wave and emergence of the third harmonic. Maximal broadening is observed for large wavelengths and long filamentation ranges. 相似文献
16.
Yanping Chen Claude Marceau Francis Théberge Jacques Dubois 《Optics Communications》2009,282(21):4283-2209
We diagnosed the polarization characteristics of Terahertz emission from a two-color femtosecond laser filament when the polarizations of ω and 2ω beams are orthogonal. We discovered that the THz pulse is elliptically polarized. The generation mechanism could be through four-wave optical rectification inside the filament zone where the inversion symmetry of air is broken. 相似文献
17.
A COUAIRON A LOTTI D FACCIO P DI TRAPANI D S STEINGRUBE E SCHULZ T BINHAMMER U MORGNER M KOVACEV M B GAARDE 《Pramana》2014,83(2):221-230
Results illustrating the nonlinear dynamics of ultrashort laser pulse filamentation in gases are presented, with particular emphasis on the filament properties useful for developing attosecond light sources. Two aspects of ultrashort pulse filaments are specifically discussed: (i) numerical simulation results on pulse self-compression by filamentation in a gas cell filled with noble gas. Measurements of high harmonics generated by the pulse extracted from the filament allows for the detection of intensity spikes and subcycle pulses generated within the filament. (ii) Simulation results on the spontaneous formation of conical wavepackets during filamentation in gases, which in turn can be used as efficient driving pulses for the generation of high harmonics and isolated attosecond pulses. 相似文献
18.
19.
Using fully incoherent white light emitted from an incandescent lamp and amplitude mask, we experimentally investigate the influence of several factors on the fabrication of the lattice in photovoltaic self-defocusing LiNbO3:Fe crystal, the factors include the orientation of the crystalline c axis relative to the principal axis of the photonic lattice and the filament, the diameter of input dark spot and the separation of the adjacent input dark spots. Experimental results reveal that the best fabricating condition of photonic lattices is that the principal axis of lattice is tilted for 45^o relative to the crystalline c axis which is parallel to the filament of the lamp. In addition, it is necessary that the diameter of the input dark spot is larger than the half of their separation. 相似文献
20.
S. A. Trushin S. Panja K. Kosma W. E. Schmid W. Fuß 《Applied physics. B, Lasers and optics》2005,80(4-5):399-403
Ten femtosecond pulses at 805 nm with energy up to 1 mJ were produced by self-phase modulation of 45-fs pulses in Ar at atmospheric pressure and subsequent compression by chirped mirrors. Focusing part of this radiation again into Ar at atmospheric pressure generates a single filament with broadband emission covering the range from > 1000 to 250 nm. This range extends farther into the UV than previously observed with such low energies, overlapping even the region of the third harmonic. Only a small fraction of the power is contained outside the central spot. Using a simple prism compressor, pulses were obtained with durations of 70 fs and energies of 700 nJ in the range 270–290 nm.This revised version was published online in March 2005. The last name of the corresponding author W. Fuß was corrected. 相似文献