共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Gautier P. Zeitoun C. Hauri A.-S. Morlens G. Rey C. Valentin E. Papalarazou J.-P. Goddet S. Sebban F. Burgy P. Mercère M. Idir G. Dovillaire X. Levecq S. Bucourt M. Fajardo H. Merdji J.-P. Caumes 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(3):459-463
We present a full optimization of the high harmonics wave front owing to the
use of a soft X-ray Hartmann sensor. The sensor was calibrated using a high
harmonic source with an accuracy of λ/50 root-mean-square (rms)
with λ around 30 nm. We observed a high harmonic wave front of
λ/7 rms, which is two times the diffraction-limit, astigmatism
being the dominant aberration for every condition of generation. By clipping
slightly the unfocused high harmonic beam, it is possible to produce a
diffraction-limited beam containing approximately 90% of the incident
energy. 相似文献
2.
A. N. Simonov A. V. Larichev V. P. Shibaev A. I. Stakhanov 《Optics and Spectroscopy》2002,92(4):536-543
The compensation dynamics of phase distortions in optical phase conjugation (OPC) using the film of azocontaining liquid-crystalline polymer was experimentally investigated. The quality of compensation of distortions of the wave front was determined, and the effect of experimental conditions on the OPC dynamics was studied. The coefficient of reflection in OPC reached 35% for a total incident light intensity of ~17 mW/cm2 at a wavelength of 532 nm. The response time of the OPC system was ~1 s at a polymer temperature of 69°C. The high-quality compensation of the wave front distortions of the laser radiation was obtained. The residual error of compensation decreased by a factor of ~100 during the transient OPC process. It is demonstrated that the spatially modulated light beam can be retrieved during repeated passages through a phase plate with strong small-scale aberrations. 相似文献
3.
M. K. Balyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2016,51(4):391-397
Diffraction of a spatially inhomogeneous X-ray wave was theoretically studied in a crystal with cubic nonlinear response to the strength of an external electric field. Using numerical calculations in case of two-beam diffraction of a narrow incident beam, the intensity distributions on the output surface of the crystal was investigated depending on the thickness and intensity of the incident beam. The results of numerical calculations of integral (spatial) coefficients of transmission and reflection are given as functions of incident wave intensity for fixed thickness of the crystal. 相似文献
4.
We report direct measurement of the electromagnetic-field spatial distribution in a neonlike Ar capillary discharge-driven soft x-ray laser beam. The wave front was fully characterized in a single shot using a Shack-Hartmann diffractive optics sensor. The wave front was observed to be dependent on the discharge pressure and capillary length, as a result of beam refraction variations in the capillary plasma. The results predict approximately 70% of the laser beam energy can be focused into an area 4 times the size of the diffraction-limited spot, reaching intensities of approximately 4 x 10(13) W/cm(2). 相似文献
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When a bounded beam is incident on an immersed plate Lamb waves or Rayleigh waves can be generated. Because the amplitude of a bounded beam is not constant along its wave front, a specific beam profile is formed that influences the local efficiency of energy conversion of incident sound into Lamb waves or Rayleigh waves. Understanding this phenomenon is important for ultrasonic immersion experiments of objects because the quality of such experiments highly depends on the amount of energy transmitted into the object. This paper shows by means of experiments based on monochromatic Schlieren photography that the area within the bounded beam responsible for Lamb wave generation differs from that responsible for Rayleigh wave generation. Furthermore it provides experimental verification of an earlier numerical study concerning Rayleigh wave generation. 相似文献
7.
Dewei Gong Zhongxiang Zhou Hongpeng Liu Jian Wang Hongyue Gao 《Optics and Lasers in Engineering》2009,47(6):662-666
A two-dimensional optical beam splitter has been realized that uses the higher diffraction orders of a refractive-index grating. Gratings were recorded experimentally with light from a semiconductor laser incident at a small angle on phenanthrenequinone-doped poly(methyl methacrylate) photopolymer. The incident signal beam, which was made up of three different wavelengths (632.8, 532.0, and 488.0 nm), was split by the grating into multiple output beams with nearly equal size and separation. Results are given for when the sample grating was placed behind, in front of, and in the focal plane of a Fourier lens. The properties of higher-order-diffraction images have been discussed. The discussion shows that a two-dimensional higher-diffraction-order optical beam splitter provides a practical method for splitting a signal beam. 相似文献
8.
An acute retroreflector having dihedral angles of 45, 60 and 90 deg exactly reflects incident rays in the opposite direction.
Beam pattern or wave front of the reflected light of the acute retroreflector can be controlled by tuning dihedral angles.
We present here a new method for calculating the reflected wave front of the acute retroreflector, in which the wave front
is calculated with high accuracy and in a shorter calculation time than by the conventional ray trace method. 相似文献
9.
N. G. Bykova I. E. Zabelinskii L. B. Ibragimova P. V. Kozlov S. V. Stovbun A. M. Tereza O. P. Shatalov 《Russian Journal of Physical Chemistry B, Focus on Physics》2018,12(1):108-114
Experiments on the measurement of air emission intensity behind the front of incident shock wave were carried out in a shock tube at an initial pressure of 0.25 Torr and shock wave velocities of 6.3–8.4 km/s. The emission intensity was measured in absolute units both in the form of an integral spectral distribution in a wavelength range of 120?400 nm (panoramic spectra) and as the time evolution of emission at the individual atomic lines of nitrogen and oxygen atoms. The results of the measurements demonstrated that the emission in air behind a shock wave in the vacuum ultraviolet region of 120–200 nm had a much higher radiation flux level than the emission in a range of 200–900 nm. 相似文献
10.
Ribak EN 《Optics letters》2001,26(23):1834-1836
Scintillation in measured wave fronts adds spurious dislocations and deformations to their reconstruction. The source of the problem is caustics formed by aberrations in intermediate planes. I propose to use intentional caustics to measure wave fronts under severe conditions such as low light level, fast scale variations, large aberrations, and discontinuities in the wave front. A simple realization is based on the Hartmann-Shack sensor, which samples the wave front with a lenslet array. Movement of the lenslets' foci is linear with slope changes. Here the lenslets are effectively formed in an acousto-optic device: Two standing waves are launched perpendicularly to the light beam and to each other. At some distance down the beam, each wave creates a comb of caustics, and the two orthogonal combs add up to an array of caustic spots. The spatial frequency of the array is linear with the temporal frequency of the standing sound waves. A simple Fourier demodulation scheme supplies the two wave-front gradients. 相似文献
11.
Baker KL Stappaerts EA Wilks SC Gavel D Young PE Tucker J Olivier SS Silva DA Olsen J 《Optics letters》2004,29(9):980-982
The achievable Strehl ratio when a finite-bit correction to an aberrated wave front is implemented is examined. The phase-conjugate engine used to measure the aberrated wave front consists of a quadrature interferometric wave-front sensor, a liquid-crystal spatial light modulator, and computer hardware-software to calculate and apply the correction. A finite-bit approximation to the conjugate phase is calculated and applied to the spatial light modulator to remove the aberrations from the optical beam. The experimentally determined Strehl ratio of the corrected beam is compared with analytical expressions for the expected Strehl ratio and shown to be in good agreement with those predictions. 相似文献
12.
Alexei A. Kamshilin Serguei V. Miridonov Igor S. Sidorov Dmitry V. Semenov Ervin Nippolainen 《Optical Review》2009,16(2):160-166
We present an analysis of statistical properties of dynamic speckles to estimate the limiting accuracy of measurements achievable
in a distance sensor using spatially filtered dynamic speckles. The main reason for inaccurate measurements using dynamic
speckles is their stochastic nature. It is shown that the average lifetime of dynamic speckles is the key factor defining
the measurement accuracy. Main conclusions of the theoretical analysis were confirmed in an experiment carried out with a
fast moving rough surface. Special attention is paid to a recently proposed range sensor using dynamic speckles generated
by a fast-deflecting laser beam. It is shown that this sensor possesses the best combination of accuracy and response time. 相似文献
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The g(44) grating is an electroholographic transmission grating in which the applied field is perpendicular to both the grating vector and the wave vector of the incident beam. It is argued that in this configuration the incident beam traverses through a periodically rotating index ellipsoid. It is shown that in the g(44) configuration the Bragg condition is fulfilled for a specific value of the applied field and for a diffracting beam polarization that is perpendicular to that of the incident beam. Consequently, the g(44) grating can be used as an electrically controlled filter. Tunability of 7 nm is demonstrated in a 2mm thick grating. 相似文献
15.
粗糙表面激光散射特性的理论研究 总被引:8,自引:0,他引:8
用矢量微扰动方法分析激光束在粗糙表面上散射的分布特性。详细讨论高斯光束的角谱和适用于准直激光束散射问题的波前分割概念认为,当用入射总功率作归一化因子时,准直粗激光束散射可近似地作为平面波处理,而细激光束散射则与平面波存在很大的差异,利用所得结果讨论了一维粗糙表面的激光隐身作用及椭圆偏振光入射时镜反射方向和后向散射场的偏振态。最后介绍两种线偏振光在粗糙表面上散射分布的差异。实验验证了主要结论。 相似文献
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Pfeiffer F Bunk O Schulze-Briese C Diaz A Weitkamp T David C van der Veen JF Vartanyants I Robinson IK 《Physical review letters》2005,94(16):164801
We report a quantitative measurement of the full transverse coherence function of the 14.4 keV x-ray radiation produced by an undulator at the Swiss Light Source. An x-ray grating interferometer consisting of a beam splitter phase grating and an analyzer amplitude grating has been used to measure the degree of coherence as a function of the beam separation out to 30 microm. Importantly, the technique provides a model-free and spatially resolved measurement of the complex coherence function and is not restricted to high resolution detectors and small fields of view. The spatial characterization of the wave front has important applications in discovering localized defects in beam line optics. 相似文献
19.
T. D. Lee H. W. Lee J. K. Kim C. O. Park 《Applied Physics A: Materials Science & Processing》1989,48(5):475-479
The grating-like spatially periodic structures are produced on the (100) surfaces of the single crystal silicon by the trains of 10 ps mode-locked ruby laser pulses at the wavelength of 694.3 nm. The periods and orientations of the structures are consistent with the model which involves the interference of the incident light with the surface electromagnetic wave excited through the coupling by surface roughness. Previously unappreciated elliptic ripple patterns are found and explained as the trails of the capillary wave excited on the molten Si surface due to the radially non-uniform deposition of energy. 相似文献
20.
Csaba Vass Károly Osvay Tamás Véső Béla Hopp Zsolt Bor 《Applied Physics A: Materials Science & Processing》2008,93(1):69-73
Submicrometer period fused silica gratings were produced by two-beam interferometric laser-induced backside wet etching technique
(TWIN LIBWE). The fourth harmonic of a Nd:YAG laser beam was spatially filtered in two steps, and the smoothened beam was
split into two parts and interfered at incident angles of 60°, 30°, 14°, and 7.7°, respectively, on the backsides of fused
silica plates that were in contact with a liquid absorber. The periods of the produced fused silica gratings were, respectively,
154 nm, 266 nm, 550 nm, and 990 nm. In the next step, TWIN-LIBWE setup was completed by using a coupling rectangular prism
in order to reach immersion setup, which made possible to fabricate 104 nm period fused silica grating. This is the smallest
laser-generated grating constant in fused silica at present.
The morphology of the etched gratings was characterized by atomic force microscope. Important parameters (modulation depth,
low-pass filtered waviness, quality factor) of the produced gratings were determined. Evolution of the grating parameters
was also studied in the 990 nm case: the dependence of modulation depth, waviness, and quality factor on the number of laser
pulses was investigated. 相似文献