共查询到20条相似文献,搜索用时 125 毫秒
1.
Temperature controlled filamentation is experimentally demonstrated in a temperature gradient gas-filled tube. The proper position of the tube is heated by a furnace and two ends of the tube are cooled by air. The experimental results show that multiple filaments are shrunken into a single filament or no filament only by increasing the temperature at the beginning of the filament. This technique offers another degree of freedom of controlling the filamentation and opens a new way for intense monocycle pulse generation through gradient temperature in a noble gas. 相似文献
2.
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
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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
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A. Iwasaki N. Aközbek B. Ferland Q. Luo G. Roy C.M. Bowden S.L. Chin 《Applied physics. B, Lasers and optics》2003,76(3):231-236
We demonstrate a new method for measuring the length of a femtosecond laser pulse induced filament in air using a LIDAR (LIght
Detection And Ranging) technique. The LIDAR involves a detector with a fast response time. The back-scattered multiphoton
induced fluorescence from nitrogen molecules excited inside the filament is measured, from which the length of the filament
can be determined. We find good agreement between the measured filament length and the length estimated from burn patterns
on paper. In addition, good qualitative agreement between the experimental measurement and numerical simulations is obtained
for the signal features of the filament. We propose that this new method can be used to quantitatively determine filamentation
at longer distances.
Received: 11 June 2002 / Revised version: 21 October 2002 / Published online: 5 February 2003
RID="*"
ID="*"Corresponding author. Fax: +1-418/656-2623, E-mail: aiwasaki@phy.ulaval.ca 相似文献
7.
Deng YP Zhu JB Ji ZG Liu JS Shuai B Li RX Xu ZZ Théberge F Chin SL 《Optics letters》2006,31(4):546-548
We investigate the evolution of filamentation in air by using a longitudinal diffraction method and a plasma fluorescence imaging technique. The diameter of a single filament in which the intensity is clamped increases as the energy of the pump light pulse increases, until multiple filaments appear. 相似文献
8.
Self-compressed (SC) pulses have been achieved through the filamentation process in air without any additional dispersion compensation, using the input pulse chirp as the control parameter. For any studied input pulse energy (3-5 mJ), we have found two opposite sign input group-delay dispersion values for which SC pulses can be achieved systematically. In addition, we have observed that the energy coupled into the inner core of the filament is always of the order of 20% of the total input pulse energy, which opens the way to a scalable technique to obtain intense short pulses directly from the filamentation process. 相似文献
9.
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
10.
We show that the filamentation dynamics of a femtosecond laser probe pulse can be readily controlled by properly matching it to the quantum revivals of pre-aligned molecules prepared through impulsive rotational Raman excitation with an advancing ultrashort pump pulse. Several features of the filamentation process including supercontinuum generation, the length of the plasma channel generated in the wake of the filament, the associated secondary radiations and the multiple filamentation pattern are all easily modified by tuning the cross phase modulation induced by the field-free revivals of molecular alignment, through the delay between the pump and the probe pulses. We show that molecular alignment can also be used to generate conical waves with extremely short intensity spike called shocked X-waves and to further tune the frequency of a few-cycle laser pulse in the wake of a self-guided intense filament. 相似文献
11.
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
12.
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
13.
Sarri G Cecchetti CA Jung R Hobbs P James S Lockyear J Stevenson RM Doria D Hoarty DJ Willi O Borghesi M 《Physical review letters》2011,106(9):095001
The onset of filamentation, following the interaction of a relatively long (τ(L)?1 ns) and intense (I(L)?5×10(14) W/cm(2)) laser pulse with a neopentane filled gas bag target, has been experimentally studied via the proton radiography technique, in conditions of direct relevance to the indirect drive inertial confinement fusion scheme. The density gradients associated with filamentation onset have been spatially resolved yielding direct and unambiguous evidence of filament formation and quantitative information about the filamentation mechanism in agreement with previous theoretical modelings. Experimental data confirm that, once spatially smoothed laser beams are used, filamentation is not a relevant phenomenon during the heating laser beams propagation through typical hohlraum gas fills. 相似文献
14.
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
15.
B. Alonso O. Varela I. J. Sola J. San Román A. Za?r C. Méndez L. Roso 《Applied physics. B, Lasers and optics》2010,101(1-2):15-22
The influence of the input pulse chirp and energy on the filamentation process is studied. Output beam profiles, spectra and energies were systematically measured by changing the pulse chirp for different input energies. A map of the different energy-chirp regions was compiled. It shows that high-energy stable single filament can be obtained by using chirped input pulses, allowing the scaling-up of the energy throughput in the filament. Moreover, under high-energy regimes nonlinear effects induced by chirped pulses could produce pulse post-compression. 相似文献
16.
Conical emission from laser plasma interactions in the filamentation of powerful ultrashort laser pulses in air 总被引:4,自引:0,他引:4
We performed detailed experimental and numerical investigations of the conical emission (CE) accompanying the filamentation of powerful ultrashort laser pulses in air. It was found that the CE originates from self-phase modulation in the plasma produced by the pulse during propagation. The experiment and the simulation agree on the essential features of the CE: The CE angle decreases with increasing wavelength and is independent of the position along the filament, and there is no CE at Stokes-shifted wavelengths. 相似文献
17.
Self-transformation of a powerful femtosecond laser pulse into a white-light laser pulse in bulk optical media (or supercontinuum generation) 总被引:2,自引:0,他引:2
V.P. Kandidov O.G. Kosareva I.S. Golubtsov W. Liu A. Becker N. Akozbek C.M. Bowden S.L. Chin 《Applied physics. B, Lasers and optics》2003,77(2-3):149-165
We present experimental and theoretical results on white-light generation in the filamentation of a high-power femtosecond laser pulse in water and atmospheric air. We have shown that the high spatio-temporal localization of the light field in the filament, which enables the supercontinuum generation, is sustained due to the dynamic transformation of the light field on the whole transverse scale of the beam, including its edges. We found that the sources of the supercontinuum blue wing are in the rings, surrounding the filament, as well as at the back of the pulse, where shock-wave formation enhanced by self-steepening takes place. We report on the first observation and demonstration of the interference of the supercontinuum spectral components arising in the course of multiple filamentation in a terawatt laser pulse. We demonstrate that the conversion efficiency of an initially narrow laser pulse spectrum into the supercontinuum depends on the length of the filament with high intensity gradients and can be increased by introducing an initial chirp. PACS 42.65.Jx; 42.65.Re; 42.25.Bs; 42.50.Hz 相似文献
18.
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-focusing 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 × 1013 W/cm2. 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 bullet?? sequence. 相似文献
19.
Two-cycle optical pulses with duration of 5 fs and energy of 0.7 mJ have been generated at 1 kHz by compressing the 38 fs laser pulses from a carrier-envelope phase (CEP) controlled Ti:sapphire laser system through a cascade filamentation compression technique. A simple and effective method is developed to suppress multiple filament formation and stabilize a single filament by inserting a soft aperture with an appropriate diameter into the driving laser beam prior to focusing, resulting in an excellent compressed beam quality. The good beam quality and potentially higher peak power make this ultrashort laser pulse source a significant tool for high-field physics applications. 相似文献