共查询到20条相似文献,搜索用时 15 毫秒
1.
Chromatic-distortion compensation in splitting and focusing of femtosecond pulses by use of a pair of diffractive optical elements 总被引:1,自引:0,他引:1
We propose a simple optical system to compensate for chromatic distortion that occurs during fan-out of femtosecond pulses by diffractive optics. The proposed system comprises a pair of diffractive elements, one for splitting an incoming pulse and the other for focusing the split pulses. With an appropriate separation between the elements, chromatic distortion resulting from the spectral bandwidth of a femtosecond pulse is removed, and an array of focused pulses with the same dimensions can be obtained. The theory has been verified through optical and processing experiments with 100-fs, 800-nm pulses. 相似文献
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《Optik》2014,125(24):7198-7202
In the present paper, laser pulse distortion/breakup and the effect of the plasma channel on the laser propagation through the collisional plasma have been studied by using moment theory approach. Second order nonlinear differential equations of the beam width parameter have been derived for the propagation of the laser through uniform homogenous plasma and preformed plasma channel having parabolic density profile. Differential equations of beam width parameter have been solved numerically using Runge Kutta method. It has been observed from analysis that when the laser pulse propagates through the homogenous plasma, the low intensity front and rear parts of the laser get defocused/diffracted and the high intensity central/main portion of the laser pulse gets self-guided. As a result of this, the laser pulse gets distorted. This distortion of the laser has not been observed when the laser pulse is propagated through the plasma channel having density minimum at the axis and maximum at the edges. The laser pulse is guided as a whole, even the low intensity front and rear parts of the laser are also guided. Therefore, the plasma channel is useful to prevent the distortion/breakup of the laser. 相似文献
3.
Xiaohong Zhou Xiaorong Gao Li Wang Zeyong Wang Bin Luo Jinlong Li 《Optics & Laser Technology》2012,44(7):2120-2124
In chirped pulse amplification, the amplification of an optical pulse in laser amplifying medium is a very important link. After considering dispersion, Kerr nonlinear effect, gain distribution and loss of the medium, the physical model that the optical pulse propagates in the medium has been established, which is suitable for the general situation where the optical pulse propagates in the amplifying medium. Using a split-step Fourier method, the propagation state of a chirped optical pulse in the amplifying medium has been numerically simulated, and the influences of the gain dispersion of the medium and the frequency detuning of the pulse on the optical pulse have been discussed emphatically. The results show that, with the amplification and propagation of the ultrashort chirped pulse in the amplifying medium, gain saturation and Kerr nonlinear effect of the medium will cause distortion of the optical pulse. For the optical pulse with a wideband spectrum, gain dispersion will cause the gain narrowing effect, so it is equivalent to a loss mechanism. The frequency detuning of the optical pulse will cause distortion of the pulse, which can be used to weaken the impact of gain saturation, thus reshaping the optical pulse. 相似文献
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Pingping Sun Dean Liu Yanli Zhang Yan Zhang Fang Liu Xuejie Zhang Jianqiang Zhu 《Optik》2011,122(24):2230-2233
By means of Collins diffraction integral, the propagation expression of an ultrashort laser pulse passing through a spatial filter is derived. The effects of the magnification of spatial filter on pulse broadening and distortion of pulse-front for the ultrashort optical pulse are analytically deduced and numerically simulated. It is found that pulse broadening and propagation time difference of a laser pulse getting through spatial filter is proportional to the magnification. As a conclusion, in an ultrashort pulse laser system with a large aperture, the effect of pulse broadening and distortion of pulse-front should be considered. 相似文献
6.
Jiying Huang Wang He Shuhong Gong 《International Journal of Infrared and Millimeter Waves》2007,28(10):889-899
When a pulse wave propagates through fog, the effects of distortion, being severer at millimeter wave band, is caused by fog
because of its dispersive property. The transfer function of a pulse signal is obtained by the theory of radio wave propagation;
the complex envelope is deduced by the solution of Fourier integral. The broadening and compressing effects of a pulse wave
are discussed. The variations of distortion effects with pulse-width, propagation distance and visibility of fog are found.
As an example, the simulating and calculating results of distortion effects for Gaussian pulse at millimeter wave band are
given. 相似文献
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Zhang S Yang X Gorenstein DG 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,143(2):382-386
In certain water suppression experiments, the residual water, which comes from a region away from the center of the RF coil and experiences a much smaller flip angle than the designed one, may appear. The residual water in the WET sequence can be reduced significantly by using a composite 90(x)( degrees )90(y)( degrees )90(-x)( degrees )90(-y)( degrees ) pulse, which de-excites molecules experiencing a small flip angle. The composite pulse, however, has two null excitation points near on resonance, causing a severe loss of spectrum intensity and baseline distortion toward the null points. Since the residual water experiences a very small flip angle, it can be treated as a linear spin system; i.e., the intensity of the residual water is proportional to the pulse strength and width. Based on this principle, the residual water can be reduced dramatically by replacing the 90 degrees pulse in the "270" WET sequence with a 270 degrees pulse for one out of every four scans, without noticeable loss of intensity and baseline distortion. 相似文献
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In this paper single ultra-fast voltage pulses are introduced to the
Pt/Ir tip of a scanning tunnelling microscope (STM), and the
non-destructive threshold of the graphite surface is studied
systematically in a wide range of pulse durations (from 10$^{4}$ to
8\,ns). Considering the waveform distortion of the pulses at the
tunnelling region, this paper gives the corrected threshold curve of
pulse amplitude depending on pulse duration. A new explanation of
threshold power has been suggested and fits the experimental results
well. 相似文献
12.
It was reported earlier that it is possible to obtain large pulse advancement with minimum pulse distortion in fast-light propagation through an erbium-doped fiber amplifier by placing the pulse on top of a mutually coherent constant background field. Here we show that comparable distortion reduction can be obtained through use of a mutually incoherent background field, a procedure that could be much more readily implemented under many circumstances. We also show that further improvement can be obtained by means of adjusting the pulse power, and for a pulse-power of the distortion decreases about 56% from 0.56 with no background while the fractional advancement decreases only about 3% from 0.16. 相似文献
13.
X射线皮秒分幅相机在强X射线情况下的应用研究 总被引:1,自引:0,他引:1
扫描型变象管X射线皮秒分幅相机在强X射线情况下,由于空间电荷效应,像质变坏,甚至无法工作。本文简述了MgF光阴极材料的性能。首次在X射线皮秒变象管分幅相机上的应用结果:降低了强X射线源情况下分幅管内空间电荷效应的影响,并获得了清晰的物理图像。 相似文献
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The interferometric measurement of an ultrashort optical pulse is demonstrated using three-photon ionization of Xe in a time-of-flight
mass spectrometer (MS). This approach allowed measurement of the third-order fringe-resolved autocorrelation trace of an ultrashort
optical pulse in the deep-ultraviolet (DUV) region. The pulse can be measured in situ using the same MS that is employed in
ultrafast spectroscopy. Sensitivity (>3×107 W) was sufficient to measure a DUV pulse used in such applications. This setup has the potential to measure the temporal
duration of a broadband (204–306 nm) ultrashort optical pulse with no additional distortion in the temporal characteristics. 相似文献
17.
J.C. Delagnes A. Monmayrant P. Zahariev A. Arbouet B. Chatel B. Girard M.A. Bouchene 《Applied physics. B, Lasers and optics》2007,86(4):573-578
An ultra-short pulse propagating in a resonant dense atomic medium experiences an important distortion due to a strong modification
of its spectral phase. This distortion cannot be corrected using the usual simple dispersive devices (a pair of prisms, gratings,
etc.). We present here an experimental demonstration of the compensation of this effect using a dual 640-pixel high-resolution
pulse-shaper device. A cross-correlation intensity measurement combined with the XFROG (cross-correlated frequency-resolved
optical gating) spectral phase measurement of the compensated pulse are performed; efficient correction of the resonant dispersive
phase is shown. A spectacular temporal compression of the propagating pulse is then obtained.
PACS 92.60.Ta; 42.50.Md; 42.65.Re; 42.79.-e 相似文献
18.
YY Wang X Peng M Alharbi CF Dutin TD Bradley F Gérôme M Mielke T Booth F Benabid 《Optics letters》2012,37(15):3111-3113
We report on the recent design and fabrication of kagome-type hollow-core photonic crystal fibers for the purpose of high-power ultrashort pulse transportation. The fabricated seven-cell three-ring hypocycloid-shaped large core fiber exhibits an up-to-date lowest attenuation (among all kagome fibers) of 40 dB/km over a broadband transmission centered at 1500?nm. We show that the large core size, low attenuation, broadband transmission, single-mode guidance, and low dispersion make it an ideal host for high-power laser beam transportation. By filling the fiber with helium gas, a 74?μJ, 850?fs, and 40?kHz repetition rate ultrashort pulse at 1550?nm has been faithfully delivered at the fiber output with little propagation pulse distortion. Compression of a 105?μJ laser pulse from 850?fs down to 300?fs has been achieved by operating the fiber in ambient air. 相似文献
19.
由于同轴电缆的低通传输特性,脉冲信号在同轴电缆中传输时不可避免地会出现畸变,并且畸变程度会随着脉冲信号频率、带宽以及传输距离的增加而增大。创新性地将图像处理领域中的一种图像复原方法——维纳滤波法应用于脉冲信号同轴电缆传输畸变补偿,仅利用同轴电缆的S参数和输出信号即可完成输入信号的重构。并以10 m同轴电缆为对象,采用该方法分别对双指数脉冲信号、高斯调制脉冲信号、调制方波信号进行传输畸变补偿。结果表明:对于不同样式的信号,该方法均具有优异的补偿性能;并且,与工程上常用的衰减补偿法相比,该方法不仅补偿精度高,还具有高的计算效率,在同轴电缆脉冲信号传输畸变补偿中具有很好的实用价值。 相似文献
20.
Bruno Macke 《Optics Communications》2008,281(1):12-17
We examine how the interference of a coherent light-pulse with its slightly time-delayed copy may generate a pulse nearly identical to the original one and ahead of it. The simplicity of this 2-pulse system enabled us to obtain exact analytic expressions of the pulse distortion, valid for a wide class of pulse shapes. Explicit results are given for the pulses usually considered (gaussian, hyperbolic-secant) but also for more realistic pulses of strictly limited duration. We finally show that, for a given distortion, the 2-pulse system can produce pulse advancements comparable to those which have been actually demonstrated in the optical range with other superluminal systems. 相似文献