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1.
Measurement of filament length generated by an intense femtosecond laser pulse using electromagnetic radiation detection 总被引:4,自引:0,他引:4
We present a new method to measure the length of a filament induced by the propagation of intense femtosecond laser pulses
in air. We used an antenna to detect electromagnetic pulses radiated from multipole moments inside the filament oscillating
at the plasma frequency. The results are compared with the values detected from the backscattered fluorescence induced by
multiphoton ionization of nitrogen molecules excited inside the filament. The values are found to be in good agreement.
Received: 6 November 2002 / Revised version: 27 January 2003 / Published online: 24 April 2003
RID="*"
ID="*"Corresponding author. Fax: +1-418/656-2623, E-mail: shosseini@phy.ulaval.ca 相似文献
2.
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
3.
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
4.
L. Corner J.S. Gibb G. Hancock A. Hutchinson V.L. Kasyutich R. Peverall G.A.D. Ritchie 《Applied physics. B, Lasers and optics》2002,74(4-5):441-444
We have used a violet diode laser at 404 nm and a distributed feedback diode laser at 1320 nm to produce 0.8 nW of radiation
at 309 nm by sum frequency generation in beta-barium borate. The UV radiation was tuned mode-hop-free over 30 GHz and used
to detect OH radicals produced in a microwave discharge. By chopping the UV light at 500 Hz, we observed a concentration of
2×1012 cm-3 with a signal to noise ratio of 30:1.
Received: 16 November 2001 / Revised version: 23 January 2002 / Published online: 14 March 2002 相似文献
5.
Filamented propagation of femtosecond laser pulses in fused silica is studied using microscopy of Femtosecond Time-resolved Optical Polarigraphy (FTOP). Both super- and subluminal translation of axial intensity maxima in a 100 fs time scale has been directly recorded. The observed spatio-temporal periodicity of the pulse shape in longitudinal and transversal directions is tentatively interpreted as two projections on X and Y axes of the same fringe pattern formed by the interference of the axial part of the beam and spontaneously generated conical beam. 相似文献
6.
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.
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
8.
William P. Acker Ali Serpengüzel Richard K. Chang Steven C. Hill 《Applied physics. B, Lasers and optics》1990,51(1):9-16
The strong stimulated Raman scattering (SRS) from diesel fuel droplets has the potential of providing the relative concentration of multicomponent fuel and the absolute size of individual droplets. The morphology-dependent resonances (MDRs) of a sphere cause the droplet to act as an optical resonator which greatly lowers the SRS threshold. The number density, quality factor, and frequency shift of several MDRs are calculated as a function of the ratio of the index of refraction of the liquid and the surrounding gas, which approaches unity at the thermodynamic critical condition for the fuel spray. The SRS spectra of monodispersed droplets of toluene, pentane, Exxon-Aromatic-150, and Mobil D-2 are presented. The exponential growth region of the SRS intensity I
1S as a function of the input laser intensity I
input is investigated for the toluene carbon ring breathing mode v
2 and the pentane C-H stretching region. The I
1S ratio of toluene and pentane is measured as a function of the ratio of the toluene and pentane concentration for monodispersed droplets. The reduced fluctuation in I
1S when I
input is changed from multimode to single-mode is displayed as a histogram of the I
1S of the v
2 mode of toluene droplets. 相似文献
9.
Self-compression of multi-millijoule femtosecond laser pulses and dramatic increase of the peak intensity are found in pressurized helium and neon within a range of intensity in which the ionization modification of the material parameters by the pulse is negligible. The pulse propagation is studied by the (3 + 1)-dimensional nonlinear Schrödinger equation including basic lowest order optical processes - diffraction, second order of dispersion, and third order of nonlinearity. Smooth and well controllable pulse propagation dynamics is found. Construction of compressed pulses of controllable parameters at given space target point by a proper chose of the pulse energy and/or gas pressure is predicted. 相似文献
10.
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
11.
Korte F. Serbin J. Koch J. Egbert A. Fallnich C. Ostendorf A. Chichkov B.N. 《Applied Physics A: Materials Science & Processing》2003,77(2):229-235
Detailed investigations of the possibilities for using femtosecond lasers for the nanostructuring of metal layers and transparent
materials are reported. The aim is to develop a simple laser-based technology for fabricating two- and three-dimensional nanostructures
with structure sizes on the order of several hundred nanometers. This is required for many applications in photonics, for
the fabrication of photonic crystals and microoptical devices, for data storage, displays, etc. Measurements of thermionic
electron emission from metal targets, which provide valuable information on the dynamics of femtosecond laser ablation, are
discussed. Sub-wavelength microstructuring of metals is performed and the minimum structure size that can be fabricated in
transparent materials is identified. Two-photon polymerization of hybrid polymers is demonstrated as a promising femtosecond
laser-based nanofabrication technology.
Received: 20 November 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +49-511/2788-100, E-mail: ch@lzh.de 相似文献
12.
The amplitudes of terahertz pulses emitted from the surfaces of InAs, InSb, InGaAs, GaAs and Ge after their excitation by femtosecond 1 μm laser pulses was compared. It has been found that this effect is most efficient in p-type InAs. The mechanisms leading to the terahertz emission are investigated and discussed. It has been concluded that in the majority of the investigated semiconductors the main contribution to THz pulse emission comes from the electrical-field-induced optical rectification effect. 相似文献
13.
G. Stobrawa M. Hacker T. Feurer D. Zeidler M. Motzkus F. Reichel 《Applied physics. B, Lasers and optics》2001,72(5):627-630
A novel liquid crystal display (LCD) with 640 stripes was successfully implemented and investigated for femtosecond pulse
shaping. As compared to previously used devices, the large active area allows for operation in high-power laser systems. The
increased number of pixels greatly enlarges the manifold of accessible pulse modulations, making the device an ideal tool
for coherent control experiments and optical information processing.
Received: 1 February 2001 / Published online: 21 March 2001 相似文献
14.
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
15.
The techniques of coupled-cavity modelocking and self-modelocking in which intensity-induced nonlinear effects are exploited have been reviewed for broad-band gain media. Particular emphases have been placed upon the archetypical colour-centre and titanium-sapphire laser configurations in which these techniques were first demonstrated and subsequent refinements are set in context. A femtosecond optical parametric oscillator pumped by a self-mode-locked titanium-sapphire laser has also been described as an exemplar of a practical means of extending the source tunability into the mid-infrared spectral region. 相似文献
16.
The critical intensity inside plasma filaments generated in air by high-power, ultra-short laser pulses is estimated analytically
and compared to recent experimental data. The result, Icrit≈4×1013 W/cm2, is highly relevant for atmospheric applications.
Received 18 August 2000 / Published online: 8 November 2000 相似文献
17.
B. Bakowski L. Corner G. Hancock R. Kotchie R. Peverall G.A.D. Ritchie 《Applied physics. B, Lasers and optics》2002,75(6-7):745-750
Cavity-enhanced absorption spectroscopy is explained in terms of the transmission function of a rapidly swept interferometer,
and the integrated transmission is shown to be proportional to the cavity ringdown time. The technique is demonstrated on
the b1Σg
+-X3Σg
- (1,0) band in molecular oxygen at 687 nm using a tunable diode laser and a relative-ly high-Q optical cavity (finesse ≈4000).
A detection limit of 3×10-8 cm-1 s1/2 is achieved for a 0.8 cm-1 scanning range.
Received: 24 June 2002 / Revised version: 5 August 2002 / Published online: 15 November 2002
RID="*"
ID="*"Corresponding author. Fax: +44-1865/275410, E-mail: peverall@physchem.ox.ac.uk 相似文献
18.
Remote sensing of the atmosphere using ultrashort laser pulses 总被引:2,自引:0,他引:2
P. Rairoux H. Schillinger S. Niedermeier M. Rodriguez F. Ronneberger R. Sauerbrey B. Stein D. Waite C. Wedekind H. Wille L. Wöste C. Ziener 《Applied physics. B, Lasers and optics》2000,71(4):573-580
Theoretical and experimental studies were performed on the propagation of ultrashort optical terawatt pulses through the atmosphere.
Propagation simulations of intense sub-picosecond pulses show that non-linear processes, such as white light generation, can
be initiated at a chosen distance by selecting an appropriate group velocity dispersion. With this technique, a white light
continuum was generated in the atmosphere whose spectral distribution was characterised in the visible and near infra-red.
Applications of this novel light source for atmospheric remote sensing were investigated, combining lidar and time-resolved
broadband absorption spectroscopy techniques. Measurements were performed on the oxygen molecule and water vapour. A comparison
between the experimental results and the tabulated spectroscopic data led to an excellent correlation with measurements made
on water vapour whereas observations on the oxygen showed discrepancy. This study demonstrates that the remote generation
of a white light source represents a new way to access the range-resolved multi-trace gas analysis in the atmosphere.
Received: 8 December 1999 / Revised version: 18 May 2000 / Published online: 16 August 2000 相似文献
19.
A pulsed optical parametric oscillator (OPO) operated in an optical cavity with a grazing-incidence grating configuration
(GIOPO) was used for sensitive photoacoustic detection of trace quantities of dinitrogen oxide (N2O). The (ν1+ν3) combination vibration band of N2O was excited with the idler beam of the GIOPO at 2.86 μm using an optical cavity optimized for the idler beam. The linewidth
of the GIOPO could be reduced to 0.4 cm-1, allowing the rotational structure of the absorption spectrum to be resolved. A concentration sensitivity (signal-to-noise
ratio=3) of 60 parts in 109 by volume (60 ppb V) N2O in synthetic air was obtained. This may be sufficient for continuous monitoring of N2O in the atmosphere.
Received: 29 April 2002 / Revised version: 4 June 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +49-6221/54-4255, E-mail: peter.hess@urz.uni-heidelberg.de 相似文献
20.
Yanhua Han 《Applied Surface Science》2009,255(17):7524-7528
Two-dimensional ‘hat-scratch’ structures are fabricated on silica glass by the interference of three non-coplanar beams originating from a single femtosecond laser pulse. The scanning electron microscope (SEM) characterizations show that the as-formed structures are composed of hat holes and scratch marks. The experimental results indicate that the structures are dependent on the intensity of laser beam. The formation of the two-dimensional ‘hat-scratch’ structures is mainly due to the combined laser ablation effects including ionization, shock wave, plasma expansion, and phase explosion. 相似文献