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1.
Triggering and guiding of high voltage discharge by using femtosecond laser filaments with different parameters
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This paper demonstrates the triggering and guiding of the stationary
high voltage (HV) discharges at 5--40 kV by using plasma filaments
generated by femtosecond laser pulses in air. A significant
reduction of the breakdown voltage threshold due to the
pre-ionization of the air gap by laser filamentation is observed.
The discharge experiments are performed by using laser pulses with
different energy from 15--60 mJ. The electron density of filaments
is detected by sonography method. The influence of the electron
density of laser filaments on the triggering and guiding HV
discharge is experimentally investigated. The results have shown
that the behaviour of plasma filaments can strongly affect the
efficiency of triggering and guiding HV discharge. 相似文献
2.
The triggering and guiding of high voltage discharge by plasma filaments generated by 400 nm and 800 nm femtosecond laser were studied experimentally. The detailed diagnostics for characteristics of filaments, such as amount of free electrons, diameter and electron density, were performed using sonographic method, fluorescence imaging and resistivity measurement. A significant reduction of the breakdown voltage threshold due to the pre-ionization of the air gap by laser pulse filaments was observed. It is shown that the 400 nm laser pulses demonstrated stronger triggering ability than 800 nm laser pulse under same pulse energy. This behavior of 400 nm femtosecond pulse is connected to the rich population of highly excited particles in filaments. 相似文献
3.
J. Zhang X. Lu Y. Y. Ma T. T. Xi Y. T. Li Z. M. Sheng L. M. Chen J. L. Ma Q. L. Dong Z. H. Wang Z. Y. Wei 《Laser Physics》2009,19(8):1769-1775
This paper reviews the recent studies of filamentation of femtosecond lasers pulses in air in the Institute of Physics, Chinese Academy of Sciences. The filamentation mechanisms of free propagated femtosecond laser pulses, effect of air turbulence on the filamentation, interaction between filaments are presented. 相似文献
4.
We report on a systematic study of the laser polarization effect on a femtosecond laser filamentation in air.By changing the laser's ellipticity from linear polarization to circular polarization, the onset position of laser filament formation becomes farther from the focusing optics, the filament length is shorter, and less laser energy is deposited. The laser polarization effect on air filaments is supported by a simulation and analysis of the polarization-dependent critical power and ionization rates in air. 相似文献
5.
This paper analytically investigates the interaction of light
filaments generated by a femtosecond laser beam in air. It obtains the
Hamiltonian of a total laser field and interaction force between two
filaments with different phase shifts and crossing angles. The
property of the interaction force, which leads the attraction or
repulsion of filaments, is basically dependent on the phase shift
between filaments. The crossing angle between two filaments can only
determine the magnitude of the interaction force, but does not
change the property of the force. 相似文献
6.
Terahertz radiation source in air based on bifilamentation of femtosecond laser pulses 总被引:1,自引:0,他引:1
Liu Y Houard A Prade B Akturk S Mysyrowicz A Tikhonchuk VT 《Physical review letters》2007,99(13):135002
A new terahertz (THz) source in air based on the bifilamentation of femtosecond laser pulses is reported. This THz radiation is 1 order of magnitude more intense than the transition-Cherenkov THz emission from femtosecond laser filaments reported recently and shows different angular and polarization properties. We attribute it to the emission from a bimodal transmission line created by two plasma filaments. 相似文献
7.
We experimentally demonstrated remote sensing of the constituents of microparticles in air by combining laser-induced breakdown spectroscopy (LIBS) and lidar, using femtosecond terawatt laser pulses. Laser pulses of 70 fs duration and 130 mJ energy generated filaments when focused at a focal length of 20 m and the pulses irradiated artificial saltwater aerosols in air at a 10 Hz pulse repetition rate. Na fluorescence was observed remotely at a distance of 16 m using a 318 mm diameter Newtonian telescope, a spectrometer, and an intensified CCD camera. These results show the possibility of remote measurement of the constituents of atmospheric particles, such as aerosols, clouds, and toxic materials, by LIBS-lidar using femtosecond terawatt laser pulses. 相似文献
8.
We present direct time- and space-resolved measurements of the electron density of femtosecond laser pulse-induced plasma filaments. The dominant nonlinearity responsible for extended atmospheric filaments is shown to be field-induced rotation of air molecules. 相似文献
9.
We examine the nonlinear dynamics of femtosecond filaments in air at different pressures. Emphasis is placed on the changes in multiple filamentation patterns produced by terawatt laser pulses. Principal modifications induced by pressure variations apply to the onset distance, size, and number of the filaments inside the laser bundle. 相似文献
10.
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
11.
Yang H Zhang J Zhang Q Hao Z Li Y Zheng Z Wang Z Dong Q Lu X Wei Z Sheng Z Yu J Yu W 《Optics letters》2005,30(5):534-536
We investigate polarization-dependent properties of the supercontinuum emission generated from filaments produced by intense femtosecond laser pulses propagating through air over a long distance. The conversion efficiency from the 800-nm fundamental to white light is observed to be higher for circular polarization than for linear polarization when the laser intensity exceeds the threshold of the breakdown of air. 相似文献
12.
A commercial femtosecond pulse laser was used to study the interaction of ultrashort laser pulses with aluminum. Tests were conducted to measure the average drilling rate over a range of laser pulse energies in both air and vacuum at the wavelengths corresponding to the fundamental and second harmonic of the laser. For the fundamental wavelength, it was observed that the drilling rates in vacuum were significantly higher than that for drilling in atmospheric air. For the laser beam that was converted to second harmonic, the drilling rate in vacuum at the same energy was slightly lower than that for drilling in air. The observed results can be explained by the presence of an energetic nanosecond pedestal in the laser pulse produced by the femtosecond laser system. This nanosecond component provides a major contribution into drilling and it is strongly affected by the optical breakdown plasma that reduces the drilling rate in air. Conversion to second harmonic reduces the relative energy content of the nanosecond component resulting in a higher contrast femtosecond pulse that is not affected by the near surface plasma. The presence of air results in self-focusing of the second harmonic laser beam, causing an increased drilling rate as compared to the interaction in vacuum. 相似文献
13.
Water vapor fluorescence in air induced by femtosecond laser filaments was systematically investigated. The fluorescence signal intensity was found to be linearly proportional to the water vapor concentration, which opens up the possibility of absolute humidity measurements, even remotely. 相似文献
14.
Q. Luo S.A. Hosseini W. Liu J.-F. Gravel O.G. Kosareva N.A. Panov N. Aközbek V.P. Kandidov G. Roy S.L. Chin 《Applied physics. B, Lasers and optics》2005,80(1):35-38
This paper describes the effects observed during the propagation of intense femtosecond laser pulses in air following the modification of the laser beam diameter with a pair of convex–concave lenses placed/mounted in a telescopic configuration. We observed that by reducing the diameter of the beam the detected back-scattered nitrogen fluorescence from the filaments becomes more stable on a shot-to-shot basis while, for a larger beam size, greater fluctuations are observed that are not correlated to shot-to-shot fluctuations in the laser pulse energy. This result leads to a new method to control the fluorescence signal which can be very important in remote-sensing applications. PACS 42.65.Jx; 42.68.Ay; 42.68.Wt 相似文献
15.
D'Amico C Houard A Franco M Prade B Mysyrowicz A Couairon A Tikhonchuk VT 《Physical review letters》2007,98(23):235002
We attribute a strong forward directed THz emission from femtosecond laser filaments in air to a transition-Cherenkov emission from the plasma space charge moving behind the ionization front at light velocity. Distant targets can be easily irradiated by this new source of THz radiation. 相似文献
16.
HAO Zuoqiang ZHANG Jie YU Jin ZHENG Zhiyuan YUAN Xiaohui ZHANG Zhe LI Yutong WANG Zhaohua LING Weijun WEI Zhiyi 《中国科学G辑(英文版)》2006,49(2):228-235
Long plasma channels in air induced by femtosecond laser pulses are investigated using three different methods, including
the cross-section imaging, resistivity measuring and acoustic diagnostics. These methods are based on different properties
of the light filaments. A comparison of the three diagnostics shows that the imaging method is the most precise one in studying
the filaments distribution and evolution, that the sonographic method is the most convenient approach to detecting long plasma
channels by detecting the acoustic wave generation, and that the resistivity measurement can only be applied for giving a
rough estimate. The diagnostics of filaments allow us to choose appropriate detecting methods and provide further insight
into the dynamic evolution of the light filaments in air. 相似文献
17.
利用皮秒和飞秒激光研究了激光在空气中聚焦产生单个等离子体通道的条件.研究发现,能量为8—12mJ皮秒激光被焦距为15cm的透镜聚焦后,可以产生较为稳定的单个通道.通过横向纵向阴影成像分析发现,通道的管壁对聚焦产生的自发光具有箍缩作用,而通道内部却有利于光的传输.同时还发现,当采用短焦距透镜时,能量低于10mJ的飞秒激光在空气中较易形成单个等离子通道.
关键词:
等离子体通道
皮秒激光
飞秒激光
阴影成像 相似文献
18.
19.
Deep drilling of metals by femtosecond laser pulses 总被引:3,自引:0,他引:3
G. Kamlage T. Bauer A. Ostendorf B.N. Chichkov 《Applied Physics A: Materials Science & Processing》2003,77(2):307-310
Results of recent investigations on deep drilling of metals by femtosecond laser pulses are reported. At high laser fluences,
well above the ablation threshold, femtosecond lasers can drill deep, high-quality holes in metals without any post-processing
or special gas environment. It is shown that for high-quality drilling of metals, the following processes are important: (1)
laser-induced optical breakdown of air containing metal vapor and small metal particles (debris) generated by multi-pulse
femtosecond laser ablation, (2) transformation of laser pulses into light filaments, and (3) low-fluence finishing.
Received: 15 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