共查询到20条相似文献,搜索用时 31 毫秒
1.
Düsterer S. Schwoerer H. Ziegler W. Salzmann D. Sauerbrey R. 《Applied physics. B, Lasers and optics》2003,76(1):17-21
The influence of prepulses on the conversion efficiency (CE) of laser radiation into 13 nm extreme ultraviolet (EUV) radiation,
resulting from lithium-like oxygen ions from O20 μm water droplets, was investigated. The laser pulse durations in the experiment
ranged from 200 fs to 120 ps. Applying prepulses preceding the main pulse at various delays of up to 11 ns, it was shown that
the CE increases differently for each measured pulse duration. The strongest dependence on the introduction of a prepulse
was observed for 2 ps laser pulses with a 20 mJ laser pulse energy. The EUV CE was improved by a factor of 15 by the introduction
of a prepulse. Calculations on the atomic physics of oxygen ions and simulations of the laser–plasma interaction revealed
the influence of the prepulse on the EUV yield.
Received: 25 October 2002 / Published online: 22 January 2003
RID="*"
ID="*"Corresponding author. Fax: +49-3641/947-202, E-mail: duesterer@ioq.uni-jena.de 相似文献
2.
A. A. Andreev K. Yu. Platonov V. I. Chestnov A. E. Petrov 《Optics and Spectroscopy》2014,117(2):276-286
The set of equations describing the motion of a thin (compared to the wavelength) target in the field of a laser pulse that takes into consideration separate motion of the electron and ion layers is derived. In the case of strong Coulomb coupling between the layers, the set of equation of motions of the layers is reduced to the well-known light-sail equation containing a self-consistent coefficient of nonlinear reflection of laser radiation by a moving target. The optimal thickness of the laser target at which the target acquires maximum energy for given laser-pulse parameters is determined. It is shown that this thickness depends not only on laser intensity, but also on laser-pulse duration and the ratio of electron and ion masses. The growth rates of transverse instability of optimal targets under their intense acceleration are analyzed. It is demonstrated that instability does not develop in the currently experimentally accessible range of laser intensities and pulse durations between 100 and 200 fs. 相似文献
3.
使用一维辐射流体力学程序MULTI模拟了脉冲CO2激光烧蚀平面锡靶的过程,研究了脉冲宽度、峰值功率密度、靶材初始密度对锡等离子体电子密度、电子温度的时空分布的影响,并结合统计分析得到最有利于产生13.5 nm 极紫外光的激光脉冲宽度。模拟结果表明,脉冲宽度为100~200 ns的长脉冲激光产生的等离子体有利于实现极紫外输出的最佳条件,通过分析等离子体的电子密度、电子温度的分布对这一结论进行了解释。临界电子密度区域有效吸收了脉冲能量,而低密度的羽辉对激光与极紫外辐射的吸收很少。采用长脉冲激光,使得辐射极紫外等离子体持续时间更长,是提高极紫外辐射效率的有效手段。同时模拟还发现,靶材初始密度对等离子体参数的影响不大。 相似文献
4.
Short-laser-pulse-driven emission of energetic ions into a solid target from a surface layer spalled by a laser prepulse 总被引:1,自引:0,他引:1
A.G. Zhidkov L.V. Zhigilei A. Sasaki T. Tajima 《Applied Physics A: Materials Science & Processing》2001,73(6):741-747
An efficient emission of picosecond bunches of energetic protons and carbon ions from a thin layer spalled from a organic
solid by a laser prepulse is demonstrated numerically. We combine the molecular dynamics technique and multi-component collisional
particle-in-cell method with plasma ionization to simulate the laser spallation and ejection of a thin (∼20–30 nm) solid layer
from an organic target and its further interaction with an intense femtosecond laser pulse. In spite of its small thickness,
a layer produced by laser spallation efficiently absorbs ultrashort laser pulses with the generation of hot electrons that
convert their energy to ion energy. The efficiency of the conversion of the laser energy to ions can be as high as 20%, and
10% to MeV ions. A transient electrostatic field created between the layer and surface of the target is up to 10 GV/cm.
Received: 13 March 2001 / Accepted: 20 March 2001 / Published online: 20 June 2001 相似文献
5.
Sergey Yu. Gus’kov 《Journal of Russian Laser Research》2010,31(6):574-588
We review the results of experimental and theoretical studies of the properties of a nonequilibrium plasma produced from volume-structured
media, containing micro- and nano-size internal elements, under laser-pulse irradiation. We consider two types of materials,
i.e., regularly and stochastically structured materials. The first type is either a set of flat layers or cylindrical and
spherical shells of micrometer thickness, and the second type is either foams of light elements or light foams containing
clusters of heavy elements with dimensions in the range of 10–100 nm. We study the properties of high-temperature laser-produced
plasmas of such materials and applications directed to developing the design of inertial confinement fusion (ICF) targets
and creating powerful sources of thermonuclear neutron and soft X-ray emission initiated by the laser pulse. The foam materials
can be used as absorbers capable of providing homogeneity of laser-energy absorption by the target. A neutron yield up to
1014−1015 DT neutrons per shot can be achieved by heating regularly structured materials using a laser pulse in the regime of the
consequent thermal explosions of solid elements containing isotopes of hydrogen. Laser-radiation conversion into soft X-ray
emission with the efficiency controlled in a wide range may be realized in laser-produced plasmas of porous media doped with
clusters of heavy elements. In particular, such a material can be used as an absorber–converter of laser radiation in inertial
confinement fusion targets. Under direct irradiation of an ICF target by a laser pulse, such a converter can provide transformation
of 20–30% of the absorbed laser energy into the energy of X-ray radiation transferred to thermonuclear capsules. 相似文献
6.
S. Bollanti F. Bonfigli E. Burattini P. Di Lazzaro F. Flora A. Grilli T. Letardi N. Lisi A. Marinai L. Mezi D. Murra C. Zheng 《Applied physics. B, Lasers and optics》2003,76(3):277-284
A long-pulse-width high-output energy (120 ns FWHM, 7 J) XeCl laser has been focused on thin tape targets (Cu and Ta) to generate
more than 100-ns-long (FWHM) EUV pulses in the 10–30 nm spectral region, suitable for projection microlithography. The conversion
efficiency was more than 20% over a 2π solid angle. We observed debris emission using a gated CCD camera, and measured the
debris speed for different irradiation conditions. We found irradiation conditions such that the measured velocities were
low enough that simple mechanical devices combined with krypton at low-pressure could efficiently stop both ionic debris and
cluster debris. Our results show that a suitable combination of driving-laser characteristics, target material and thickness,
environment gas and mechanical choppers can make clean and increase the power of EUV solid-target laser-plasma sources.
Received: 21 October 2002 / Published online: 26 February 2003
RID="*"
ID="*"Corresponding author. Fax: +39-06/9400-5334, E-mail: bollanti@frascati.enea.it 相似文献
7.
Nanocylinder-array structure greatly increases the soft X-ray intensity generated from femtosecond-laser-produced plasma 总被引:5,自引:0,他引:5
T. Nishikawa H. Nakano K. Oguri N. Uesugi M. Nakao K. Nishio H. Masuda 《Applied physics. B, Lasers and optics》2001,73(2):185-188
In order to increase the soft X-ray conversion efficiency for the femtosecond-laser-produced plasma, we adopted a nanocylinder-array
structure target. Gold nanocylinder-array targets with 70–90 nm cylinder diameter and 100 nm cylinder pitch were made. A continuous
smooth soft X-ray spectrum adequate for X-ray absorption spectroscopy was obtained. An around 20-fold soft X-ray (7–20 nm)
fluence enhancement compared with a flat-surface gold foil target was obtained when the cylinder height was 18 μm. X-ray (>0.06 keV)
pulse duration was 17 ps, which is much shorter than that obtained by using the pre-pulse technique. The X-ray pulse peak
intensity was 7-fold higher than that of a gold foil target.
Received: 2 May 2001 / Revised version: 1 June 2001 / Published online: 18 July 2001 相似文献
8.
Pulse-parameter dependence of the configuration characteristics of a micro-structure in fused SiO2 induced by femtosecond laser pulses 总被引:1,自引:0,他引:1
L. Luo C. Li D. Wang H. Yang H. Jiang Q. Gong 《Applied Physics A: Materials Science & Processing》2002,74(4):497-501
The fabrication of a micro-structures in fused SiO2 by femtosecond laser pulses was studied in the range of pulse duration 150∼500 fs, pulse energy 60 nJ to ∼7 μJ and wavelengths
400 nm and 800 nm. The characteristics of the cross section of the micro-structure were explained with the multiphoton-ionization
and avalanche-ionization processes in the femtosecond laser-induced breakdown. The characteristics of the longitudinal length
of the micro-structure relating to the direct-focusing and self-action effects are also discussed.
Received: 10 January 2001 / Accepted: 7 April 2001 / Published online: 23 May 2001 相似文献
9.
1.06μm波长的强激光束辐照Au材料制作的空腔靶,采用目前国内最先进的诊断设备。对腔内高温等离子体现象演变规律进行了实验观察,获得了反射激光、能量吸收、X光转换、亚千X光能谱及时空特性、辐射温度、超热电子等重要物理信息,并就实验结果作了必要的分析和讨论 相似文献
10.
High-power picosecond LiB3O5 optical parametric oscillators tunable in the blue spectral range 总被引:2,自引:0,他引:2
The paper reports on an experimental investigation and numerical analysis of noncritically and critically phasematched LiB3O5 (LBO) optical parametric oscillators (OPOs) synchronously pumped by the third harmonic of a cw diode-pumped mode-locked Nd:YVO4 oscillator–amplifier system. The laser system generates 9.0 W of 355-nm mode-locked radiation with a pulse duration of 7.5 ps
and a repetition rate of 84 MHz. The LBO OPO, synchronously pumped by the 355-nm pulses, generates a signal wave tunable in
the blue spectral range 457–479 nm. With a power of up to 5.0 W at 462 nm and 1.7 W at 1535 nm the conversion efficiency is
74%. The OPO is characterized experimentally by measuring the output power (and its dependence on the pump power, the transmission
of the output coupler and the resonator length) and the pulse properties (such as pulse duration and spectral width). Also
the beam quality of the resonant and nonresonant waves is investigated. The measured results are compared with the predictions
of a numerical analysis for Gaussian laser and OPO beams. In addition to the blue-signal output visible-red 629-nm radiation
is generated by sum-frequency mixing of the 1.535-μm infrared idler wave with the residual 1.064-μm laser radiation. A power
of 1.25 W of 1.535-μm idler radiation and 5.7 W of 1.064-μm laser light generated a red 629-nm output power of 2.25 W.
Received: 2 February 2000 / Revised version: 28 July 2000 / Published online: 22 November 2000 相似文献
11.
研究了不同条件下脉冲放电CO2激光烧蚀平板锡靶产生的等离子体极紫外辐射特性, 设计并建立了一套掠入射极紫外平焦场光栅光谱仪, 结合X射线CCD探测了光源在6.5~16.8 nm波段的时间积分辐射光谱,得到了极紫外光谱随激光脉宽, 入射脉冲能量及背景气压的变化规律。实验结果发现:入射激光脉冲能量在30~600 mJ变化时,极紫外辐射光谱的强度随辐照激光脉冲能量的增加而增加, 但并不是线性关系, 具有饱和效应, 且产生极紫外辐射的脉冲能量阈值约为30 mJ,当激光脉冲能量为425 mJ时具有最高的转换效率,此时中心波长13.5 nm处2%带宽内的转换效率约为1.2%。激光脉冲半高全宽在50~120 ns范围内变化时, 极紫外辐射光谱的峰值位置均位于13.5 nm,光谱形状几乎没有什么变化, 但是脉宽从120 ns变到52 ns后,由于激光功率密度的提高,极紫外辐射强度也随之增强了约1.6倍。极紫外光谱的强度随背景气压的增大而迅速下降, 当腔内空气气压为200 Pa时, 极紫外辐射光子几乎被全部吸收,而当缓冲氦气气压为7×104 Pa时,仍能够探测到微弱的极紫外辐射信号,计算表明100 Pa的空气对13.5 nm极紫外光的吸收系数为3.0 m-1,而100 Pa的He气的吸收系数为0.96 m-1。 相似文献
12.
B. Köhler U. Bäder A. Nebel J.-P. Meyn R. Wallenstein 《Applied physics. B, Lasers and optics》2002,75(1):31-34
We report on an injection-seeded 9.5-W 82-MHz-repetition-rate picosecond optical parametric generator (OPG) based on a 55 mm
long crystal of periodically poled lithium niobate (PPLN) with a quasi-phase-matching (QPM) grating period of 29.75 μm. The
OPG is excited by a continuously diode pumped mode-locked picosecond Nd:YVO4 oscillator-amplifier system. The laser system generates 7 ps pulses with a repetition rate of 82.3 MHz and an average power
of 24 W. Without injection-seeding the total average output power of the OPG is 8.9 W, which corresponds to an internal conversion
efficiency of 50%. The wavelengths of the signal and idler waves were tuned in the range 1.57–1.64 μm and 3.03–3.3 μm, respectively,
by changing the crystal temperature from 150 °C to 250 °C. Injection seeding of the OPG at 1.58 μm with 4 mW of single frequency
continuous-wave radiation of a distributed-feedback (DFB) diode laser increases the OPG output to 9.5 W (53% conversion efficiency).
The injection seeding increases the pulse duration and reduces the spectral bandwidth. When pumped by 10 W of 1.06 μm laser
radiation, the duration of the signal pulses increased from 3.6 ps to 5.5 ps while the spectral bandwidth is reduced from
4.5 nm to 0.85 nm. Seeding thus improved the time-bandwidth product from 1.98 to a value of 0.56, much closer to the Fourier
limit.
Received: 29 April 2002 / Published online: 8 August 2002 相似文献
13.
We describe a laser system that readily provides radiation tunable from 2 μm in the infra-red to 35 nm in the extreme ultraviolet
spectral range. The broad spectral range is covered through a range of non-linear processes such as Raman shifting and high-order
harmonic generation. Pulses with duration of tens of picoseconds are obtained. The relative bandwidth of the radiation is
δλ/λ=10-4, comparable with what can be achieved by using high-resolution monochromators at state-of-the-art synchrotron beamlines.
We discuss different methods for characterising the radiation in this wide wavelength regime. We also discuss the capabilities
of the system from the measured parameters.
Received: 12 December 2000 / Revised version: 8 March 2001 / Published online: 27 April 2001 相似文献
14.
A miniaturized, high repetition rate, picosecond all solid state photo-induced distributed feedback (DFB) polymer-dye laser
is described by applying a passively Q-switched and frequency-doubled Cr4+:Nd3+:YAG-microchip laser (pulse width Δτ=540 ps, repetition rate ν=3 kHz, pump energy Epump=0.15 μJ) as a pump source. A poly-methylmethacrylate film doped with rhodamine B dye serves as active medium. The DFB-laser
pulses are temporally and spectrally characterized, and the stability of the thin polymer/dye film at high repetition rates
is analyzed. The shortest DFB-laser pulses obtained have a duration of 11 ps. After the emission of 350000 pulses the intensity
of the DFB-laser output has decreased by a factor of two and the pulse duration has increased by a factor of 1.2. For single
DFB-laser pulses of 20-ps duration the spectral bandwidth is measured to be Δλ=0.03 nm, which is only 0.005 nm above the calculated
Fourier limit assuming a Gaussian profile for the temporal shape of the pulses. Coarse wavelength tuning of the DFB laser
between 590 and 619 nm is done by turning the prism. Additionally, a fine tuning of the DFB-polymer-laser wavelength is achieved
by changing the temperature of the polymer/dye layer (=-0.05 nm/°C) in the range from 20 to 40 °C.
Received: 1 March 2001 / Revised version: 23 May 2001 / Published online: 18 July 2001 相似文献
15.
We use three-dimensional particle-in-cell simulations to study laser wake field acceleration (LWFA) at highly relativistic
laser intensities. We observe ultra-short electron bunches emerging from laser wake fields driven above the wave-breaking
threshold by few-cycle laser pulses shorter than the plasma wavelength. We find a new regime in which the laser wake takes
the shape of a solitary plasma cavity. It traps background electrons continuously and accelerates them. We show that 12-J,
33-fs laser pulses may produce bunches of 3×1010 electrons with energy sharply peaked around 300 MeV. These electrons emerge as low-emittance beams from plasma layers just
700-μm thick. We also address a regime intermediate between direct laser acceleration and LWFA, when the laser-pulse duration
is comparable with the plasma period.
Received: 12 December 2001 / Published online: 14 March 2002 相似文献
16.
G. Tsilimis J. Kutzner H. Zacharias 《Applied Physics A: Materials Science & Processing》2003,76(5):743-749
An extreme ultraviolet (EUV) laser light source based on high-harmonic generation is presented. Coherent radiation in the
photon energy range hν=20–120 eV is produced in the conversion media argon, neon and helium. High-harmonic radiation in the
energy range 20–50 eV is applied to investigate photoemission spectra of Pt (111) and CO/Pt (111). In the photoemission spectra
of the clean surface, new secondary electron emission structures are found which influence the cross section analysis of the
CO states. When taking these Pt resonances into consideration, the 4σ and 5σ CO shape resonances are found at photon energies
of 37 eV and 28 eV, respectively. Additionally, a resonance at hν=31 eV is also observed for the CO 1π state, in contrast
to formerly published experimental data. Experimental and theoretical data suggest that this resonance is not connected to
the well-known shape resonances in the σ-channel. Based on theoretical approaches, it is identified as an autoionization resonance.
Received: 8 April 2002 / Accepted: 22 May 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-251/833-3604, E-mail: kutzner@uni-muenster.de 相似文献
17.
E. György I.N. Mihailescu P. Serra A. Pérez del Pino J.L. Morenza 《Applied Physics A: Materials Science & Processing》2002,74(6):755-759
We report micrometre-sized crown-like structure growth on a Ti surface by multipulse Nd:YAG (λ=1.064 μm,τ=170 ns) laser irradiation
in air at atmospheric pressure. The irradiation was performed at 8×107 W/cm2 laser-pulse intensity, below the ablation threshold. A ring-shape structure develops in the centre of the irradiation spot
after the action of five laser pulses. The further increase of the laser-pulse number leads gradually to a crown-like structure,
which has, for 150 pulses, a height of 120–140 μm above the non-irradiated Ti surface. The forming crater’s depth does not
exceed the height of the grown structure. In the neighbouring zone, after the action of 25 laser pulses, microcracks of the
oxide surface layer develop. With the next pulses this leads to the formation of a surface microrelief. The crown-like-structure
growth is originated by molten material movement attributed to the laser-induced plasma-recoil pressure.
Received: 6 June 2001 / Accepted: 6 January 2002 / Published online: 26 March 2002 相似文献
18.
A. Tsunemi N. Saito K. Nagasaka H. Tashiro 《Applied physics. B, Lasers and optics》1999,69(2):103-106
16-μm Stokes pulses were directly generated for the first time to our knowledge by an intracavity configuration for the para-hydrogen
Raman laser. We have analyzed Stokes field growth using a focused gain model and designed a pump/Stokes cavity to satisfy
CO2 pump power and pulse duration requirements for Raman oscillation. The CO2 laser oscillation with circular polarization was realized by seeding externally circularly polarized CO2 radiation. An output energy of 2.4 mJ was obtained with the output coupler of 0.5% transmittance, which indicated that 420 mJ
of Stokes pulse energy was stored inside the cavity. This suggests that a much higher energy can be extracted by the optimization
of cavity parameters.
Received: 18 November 1998 / Published online: 26 May 1999 相似文献
19.
G. Schreiber H. Suche Y.L. Lee W. Grundkötter V. Quiring R. Ricken W. Sohler 《Applied physics. B, Lasers and optics》2001,73(5-6):501-504
Using an FM-mode-locked Ti:Er:LiNbO3 waveguide laser as the fundamental source, wavelength conversion by cascaded χ(2):χ(2)-difference frequency generation with a conversion efficiency of up to +3(-4.6) dB was demonstrated at a pulse repetition
rate of about 2 (10) GHz. In addition, multi-channel conversion was demonstrated with a fully packaged wavelength converter
using a continuous fundamental source.
Received: 29 May 2001 / Revised version: 10 August 2001 / Published online: 2 November 2001 相似文献
20.
S. Yu. Gus’kov N. V. Zmitrenko Yu. E. Markushkin Yu. A. Merkul’ev 《Journal of Russian Laser Research》2007,28(2):148-162
The energetic characteristics of the compression and burning of targets with beryllium and beryllium deuteride shells are
compared. The characteristics considered include the hydrodynamic efficiency, the efficiency of energy transmission to the
thermonuclear fuel, and the gain factor found from numerical simulation using the ‘Diana’ one-dimensional mathematical code.
The calculations are carried out for direct-drive cryogenic laser targets with the ablator shells made of beryllium or beryllium
deuteride with parameters corresponding to the third harmonic of energy of the neodymium-laser radiation with a pulse energy
of 1–3 MJ. It is proved that the gain of beryllium hydride targets can be brought to the level of beryllium targets due to
variations in the geometrical parameters of BeD2 targets. It is shown that the fission of BeD2 or BeDT ablators in reactor-scale targets could significantly contribute to the final thermonuclear yield.
__________
Translated from Preprint No. 20 of the P. N. Lebedev Physical Institute, Moscow (2001). 相似文献