共查询到20条相似文献,搜索用时 31 毫秒
1.
A high power pulse Nd-glass laser system with plasma mirror is studied. Plasma is created on the surface of a solid target and the action is superradiantly triggered. Long trains of modelocked pulses are generated if the carbon or metal targets are used and Q-switched pulses are observed with dielectric targets like PVC. Tens of joules of light energy are extracted from the laser medium and absorbed by plasma in both regimes. Spatial and temporal structures of the laser beam are very reproducible, the laser action is insensitive to variations in air pressure inside the target chamber. Stimulated Brillouin back-scattering in the underdense plasma is discussed as the nonlinear mechanism governing the plasma reflectivity. 相似文献
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A 3 kW radially polarized beam is generated from a CO(2) laser by means of a resonant grating mirror. The design results and spectral characterization of a broadband polarizing mirror are presented as well as the mirror's operation in a CO(2) laser resonator. In a long-term experiment a radially polarized beam with a power of 2.7 kW was observed for several hours, proving the high stability of this polarizing scheme. 相似文献
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We report what is believed to be the first demonstration of soft-x-ray interferometry of a plasma with a tabletop soft-x-ray laser. A Lloyd's mirror interferometer was used in combination with a very compact lambda = 46.9 nm capillary-discharge-pumped laser to map the electron density in the cathode region of a pinch plasma. 相似文献
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H. Komori Y. Ueno H. Hoshino T. Ariga G. Soumagne A. Endo H. Mizoguchi 《Applied physics. B, Lasers and optics》2006,83(2):213-218
A CO2 laser-driven Xe liquid jet plasma has been studied with respect to its usability as a EUV lithography light source. A short-pulse TEA-CO2 master oscillator power amplifier system (MOPA) and a pre-pulse Nd:YAG laser were used for the plasma generation. The dependence of EUV plasma parameters, e.g., conversion efficiency, plasma image, in-band and out-of-band spectra, on the delay time between the pre-pulse and the main pulse laser was investigated. A maximum conversion efficiency of 0.6% was obtained at a delay time of about 200 ns. In addition, characteristics of fast ions were measured by the time-of-flight method. The peak energy of the fast ion energy distribution decreased significantly at delay times longer than 200 ns. This result is very promising with respect to a collector mirror lifetime extension by magnetic field mitigation. PACS 52.50.Jm 相似文献
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In deep penetration laser welding, a capillary called keyhole is formed when the energy intensity reaches 106 W/cm2. During this process, the vaporized metal and the surrounding atmosphere can be ionized to form plasma both in and above the keyhole. The stability of the keyhole has an important influence on the properties of welded components and the fluctuations of plasma. In this paper, a method was developed to acquire the stability information from plasma images taken by high-speed photography. The influences of surface impurity and the flowrate of side-assist gas on the stability were investigated. Bead-on-plate welding was performed on 12 mm E-grade shipbuilding steel plates using a 15 kW CO2 laser, with helium as the blowing gas. Three characteristic parameters were used to evaluate the stability. It was found that these three characteristic parameters can effectively indicate the stability variation caused by the surface impurity and gas flowrate. The present research provides important insights into developing image-based sensors to monitor the welding process. 相似文献
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Lévy A Ceccotti T D'Oliveira P Réau F Perdrix M Quéré F Monot P Bougeard M Lagadec H Martin P Geindre JP Audebert P 《Optics letters》2007,32(3):310-312
We present and characterize a very efficient optical device that employs the plasma mirror technique to increase the contrast of high-power laser systems. Contrast improvements higher than 10(4) with 50% transmission are shown to be routinely achieved on a typical 10 TW laser system when the pulse is reflected on two consecutive plasma mirrors. Used at the end of the laser system, this double plasma mirror preserves the spatial profile of the initial beam, is unaffected by shot-to-shot fluctuations, and is suitable for most high peak power laser systems. We use the generation of high-order harmonics as an effective test for the contrast improvement produced by the double plasma mirrors. 相似文献
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A repetitively pulsed electron-beam-controlled CO2 laser driven by an electron accelerator with a plasma electron emitter based on low-pressure glow discharge with hollow anode
and cathode is presented. The application of the proposed emitter makes it possible to sharply increase the current and to
control the electron-beam duration and, hence, the energy and time characteristics of the laser. It is demonstrated that the
radiation pulse duration ranges from 300 to 1200 μs, whereas the radiation energy amounts to 200 J at an efficiency of 18%.
In the course of lasing, the focal spot is not affected by the heterogeneous heating of the active medium. A significant heterogeneity
in the gas flow upon an incomplete renewal of the gas in the zone filled with radiation leads to an increase in the focal
spot owing to the wavefront distortions.
Original Text ? Astro, Ltd., 2006. 相似文献
9.
J. J. Camacho M. Santos L. Díaz L. J. Juan J. M. L. Poyato 《Applied Physics A: Materials Science & Processing》2010,99(1):159-175
A spectroscopic study of ambient air plasma, initially at room temperature and pressures ranging from 32 to 101 kPa, produced
by high-power transverse excitation atmospheric (TEA) CO2 laser (λ=9.621 and 10.591 μm; τ
FWHM≈64 ns; power densities ranging from 0.29 to 6.31 GW cm−2) has been carried out in an attempt to clarify the processes involved in laser-induced breakdown (LIB) air plasma. The strong
emission observed in the plasma region is mainly due to electronic relaxation of excited N, O and ionic fragments N+. The medium-weak emission is due to excited species O+, N2+, O2+, C, C+, C2+, H, Ar and molecular band systems of N
2+(_{2}^{+}(
B
2\varSigma u+^{2}\varSigma _{\mathrm{u}}^{+}
–X
2\varSigma g+)^{2}\varSigma _{\mathrm{g}}^{+})
, N2(C3
Π
u–B3
Π
g), N
2+(_{2}^{+}(
D2
Π
g–A2
Π
u) and OH(A2
Σ
+–X2
Π). Excitation temperatures of 23400±700 K and 26600±1400 K were estimated by means of N+ and O+ ionic lines, respectively. Electron number densities of the order of (0.5–2.4)×1017 cm−3 and (0.6–7.5)×1017 cm−3 were deduced from the Stark broadening of several ionic N+ and O+ lines, respectively. Estimates of vibrational and rotational temperatures of N
2+_{2}^{+}
electronically excited species are reported. The characteristics of the spectral emission intensities from different species
have been investigated as functions of the air pressure and laser irradiance. Optical breakdown threshold intensities in air
at 10.591 μm have been measured. 相似文献
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A plasma electrode potentially suitable for dc discharge pumped lasers has been developed based on the repetitive creation of a spark channel. The high-density plasma is a source of charge carriers for the dc discharge, thereby largely eliminating the cathode and anode falls. Potential reduction improves with increasing spark repetition frequency until about 9 kHz, at which point the falls are virtually eliminated. Fortuitously, the most beneficial regime of plasma electrode operation also appears to coincide with the optimum E/N range for CO2 laser vibrational excitation. 相似文献
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《Infrared physics》1985,25(4):633-640
Measurement of the e.m.f. generated by the electron emission from laser-produced solid target plasmas shows the evolution of the laser pulse. Using this phenomenon, a “plasma detector” is constructed. The feasibility of the plasma detector is demonstrated for a long TEA CO2 laser pulse (100 mJ, 60ns). Good time resolution is obtained by using an anode coated with ceramics. The linearity of response with the incident laser intensity for the 109–1010 W/cm2 range is confirmed. The relation of the output voltage to the incident laser intensity is analyzed according to the isothermal rarefaction model. This theoretical analysis and experimental results suggest that there exists an optimum separation between the anode and the cathode. 相似文献
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《中国光学快报(英文版)》2018,(10)
The temporal profiles of high-power short-pulse lasers reflected from self-induced plasma mirrors(PMs) were measured with high temporal resolution in the sub-picosecond window. The leading front shape of the laser pulse is found to depend sensitively on the laser fluence on the PM surface. Spectral modulation plays a key role in pulse profile shaping. Our findings will extend our knowledge on properly using PMs. 相似文献
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Air-breathing mode laser propulsion experiment with a long-pulse transversely excited (TE) CO2 laser is carried out, and its ignition problem is solved with the ignition needle of lightcraft. Owing to the ignition needle, an order of magnitude reduction in the ignition threshold is demonstrated. The result is compared with previous study. The momentum coupling coefficient is also measured in the experiment and its dependence upon laser pulse energy (6 14 J) and pulse width (20, 32, and 40 μs) is discussed. 相似文献
19.
W. Fuß J. Göthel K. L. Kompa M. Ivanenko W. E. Schmid 《Applied physics. B, Lasers and optics》1992,55(1):65-70
A low-pressure (20 mbar) CO2 laser allows to extract pulses at several selected wavelengths simultaneously from the same active medium. We demonstrated this, using an industrial laser modified by a Q-switch and a resonator with two branches. In one branch the wavelengths are spatially separated, whereas in the other they oscillate in one common transverse mode. We designed a multi-wavelength resonator which requires a single additional reflector compared to usual laser cavities. It provided tunable oscillation at six wavelength simultaneously. 相似文献
20.
《Infrared physics》1989,29(2-4):415-422
An illustration of an interaction of pulsed multimode TEA CO2 laser radiation, through or without a mask, as well as of a laser scanning process of a frequency Q-modulated cw CO2 laser beam on glass surfaces has been shown. As an object of investigation glass articles with composition as a standard industrial potassium-boron silicate glass, we have used. A complex of investigations shows that the laser treatment leads to qualitative constant changes (well defined peeling structure) depending on the time surface treatment, defocusing and the pulse length of the laser output. 相似文献