Lateral shearing interferometry of high-harmonic wavefronts

We present a technique for frequency-resolved wavefront characterization of high harmonics based on lateral shearing interferometry. Tilted replicas of the driving laser pulse are produced by a Mach-Zehnder interferometer, producing separate focii in the target. The interference of the resulting harmonics on a flat-field extreme ultraviolet spectrometer yields the spatial phase derivative. A comprehensive set of spatial profiles, resolved by harmonic order, validate the technique and reveal the interplay of single-atom and macroscopic effects.     

Holographic interferometry with wavefront shearing

Application of the common path shearing interferometric techniques to holography to study the phase variations in transparent specimens is described. These shearing interferometers are less susceptible to vibration and other external disturbances. Real-time reconstructed interferograms are shown.     

Physical foundations of achromatic nulling interferometry for stellar coronagraphy

We propose an achromatic interferometer for the observation of a faint off-axis light source against the background of a bright on-axis light source. The on-axis source and its copy acquire an achromatic phase shift by 180° and interfere with a phase difference of π. The achromatic phase shift is attributable to the geometric phase in the three-dimensional interferometer scheme. Interference spatially separates the nulled and bright fields of the on-axis source, redirecting them on opposite sides of the beamsplitter. Interference does not attenuate the field of the off-axis source and redirects it with an equal intensity on both sides of the beamsplitter. We consider the principle of operation of the nulling interferometer and constraints on the attenuation of an extended source due to the decrease in coherence. The laboratory breadboard and experiment are briefly described.     

A microprism array as shearing device for speckle shearing interferometry

In most speckle shearing interferometers image shearing is performed by means of a Michelson interferometer or by means of a wedge prism covering half of the aperture of the camera objective. We present a speckle shearing interferometer which utilizes a microprism array for this purpose. It is placed between the test specimen and the camera. In comparision with a wedge prism it exhibits some advantages: it needs no exact alignment, it works with any camera lens, the shearing distance and direction of shearing can be easily changed by changing position (resp. angular orientation) of the element. Phase stepping for computer evaluation of the speckle shearing interferograms is performed by the translation of the shearing element. A special translation stage was developed. Experimental results are presented. The interferometer is suited for microcomponent and microsystem testing.     

Design of achromatic phase shifters for spaceborne nulling interferometry

The designs of various achromatic phase shifters (APSs) envisaged for nulling interferometry and the search for extrasolar planets or systems from space are discussed in this Letter. It is shown that APS designs can sensibly influence the performance achieved by a simple Bracewell interferometer if they introduce a field of view (FoV) reversal and a pupil flip along one interferometer arm. Analytical and numerical simulations are presented, showing severe signal-to-noise ratio loss and a weak capacity for serendipitous discoveries. The use of FoV-reversal APS should therefore be restricted to the characterization of already known extrasolar planets rather than to their detection.     

Ponderomotive shearing for spectral interferometry of extreme-ultraviolet pulses

We propose a novel method for completely characterizing ultrashort pulses at extreme-ultraviolet (XUV) wavelengths by adapting the technique of spectral phase interferometry for direct electric-field reconstruction to this spectral region. Two-electron wave packets are coherently produced by photoionizing atoms with two time-delayed replicas of the XUV pulse. For one of the XUV pulses, photoionization occurs in the presence of a strong infrared pulse that ponderomotively shifts the binding energy, thereby providing the spectral shear needed for reconstruction of the spectral phase of the XUV pulse.     

径向剪切干涉法综合诊断光束质量研究

 为了解决高功率激光装置光束质量诊断系统的自验证问题,研究了基于空间相位调制的径向剪切干涉法综合诊断光束质量的实验应用。该方法理论上只需一台干涉仪且从单幅干涉图中获取光束的近场、相位和远场分布信息。实验结果表明,目前可以得到高分辨率的相位分布,由测量近场和相位恢复出的远场同CCD直接测量得到的远场形态相同,环围能量比曲线相当吻合,不足之处在于只能提取近场较低空间频率成分,还达不到CCD直接测量的空间分辨水平。     

Holographic reverse shearing interferometry with high measurement sensitivity

The possibility of studying phase objects by reverse shearing interferometry with high measurement sensitivity is demonstrated. Phase objects are studied in two stages. In the first stage, holographic reverse shear interferograms are measured with and without an object under nonlinear conditions with tuning to frequent reference fringes. In the next stage, these interferograms are optically processed to obtain two interference patterns. The behavior of the interference fringes is the same as in the case of conventional double-beam interferometry with a standard reference wave. The increase in the measurement sensitivity in the thus-obtained interference patterns is due to the use of higher diffraction orders reconstructed from the holographic interferograms. A possibility of controlling the width of interference fringes is considered. The results of experimental approval of this technique are presented.     

光源编码的白光散斑剪切干涉计量术

本文提出了一种用非相干光源照明进行剪切干涉计量的方法—光源编码的白光散斑剪切干涉计量术.它采用光栅对光源进行编码以提高空间相干性,使物体的两个剪切像的波面部分相干叠加,以实现剪切干涉.     

径向剪切干涉法综合诊断光束质量研究

为了解决高功率激光装置光束质量诊断系统的自验证问题,研究了基于空间相位调制的径向剪切干涉法综合诊断光束质量的实验应用。该方法理论上只需一台干涉仪且从单幅干涉图中获取光束的近场、相位和远场分布信息。实验结果表明,目前可以得到高分辨率的相位分布,由测量近场和相位恢复出的远场同CCD直接测量得到的远场形态相同,环围能量比曲线相当吻合,不足之处在于只能提取近场较低空间频率成分,还达不到CCD直接测量的空间分辨水平。     

横向剪切干涉中剪切量的选取及分析

横向剪切干涉技术是一种直接测量波面相位分布的光学测量方法,由于其不需要高精度的参考平面,并且能够测量偏离量较大的表面面形偏差,因此得到了更为广泛的应用。但是,通常情况下剪切量大小的选择凭工作经验来确定。为了给出一种定量的剪切量判定方法,论文提出了一种基于Zernike多项式拟合的剪切量判定方法,通过计算机仿真和实验给出了剪切量与测量误差的关系,发现剪切量为测量口径1/10时即可达到良好的测量结果。     

Two-dimensional spectral shearing interferometry for few-cycle pulse characterization

We present a new method for measuring the spectral phase of ultrashort pulses that utilizes spectral shearing interferometry with zero delay. Unlike conventional spectral phase interferometry for direct electric-field reconstruction, which encodes phase as a sensitively calibrated fringe in the spectral domain, two-dimensional spectral shearing interferometry robustly encodes phase along a second dimension. This greatly reduces demands on the spectrometer and allows for complex phase spectra to be measured over extremely large bandwidths, potentially exceeding 1.5 octaves.     

剪切散斑干涉术的统计分析

本文用统计光学方法分析了剪切散斑图的成象过程;散斑图的频谱分布以及全场滤波干涉条纹的形成.发现剪切散斑干涉条纹不仅与三维位移微分有关,而且与面内位移量有关.在此基础上又讨论了影响干涉条纹质量的有关因素,并作了实验验证.     

Surface measurement of the TRAO 14 meter antenna with a shearing interferometry

We employed shearing interferometric technique to the TRAO 14 m antenna to measure and improve the surface figure. For the first time. this technique is combined with a 150 GHz band heterodyne receiver having a narrow IF band width of 500 MHz and results in the improvement of surface to 60 μm at a 0.9 m spatial resolution. The beam efficiency measured after this correction is increased from 36% to 44% at 150 GHz. It was found that the technique is very useful in measuring and correcting, at least, the large scale surface figure of an antenna in an economical way.     

Constant radial shearing interferometry with two spiral phase gratings

Two spiral phase gratings consisting of triangular grooves are used for arranging a simple constant radial shearing interferometer with small light loss. The fringe formation is described and a method for analyzing the interferograms is presented.     

软X射线双频光栅剪切干涉法研究

本文中设计了一种利用软X射线双频光栅作为剪切干涉元件的剪切系统, 使剪切干涉法在软X射线波段得到了应用. 介绍了软X射线双频光栅的结构及衍射特性, 在同步辐射光束线对双频光栅的效率分布进行了测试实验, 两个剪切级次的效率比值高于75%, 干扰级次效率低于5%. 利用软X射线双频光栅为剪切干涉光学元件, 对待测靶进行了静态检测, 得到了对比度高, 稳定的干涉条纹, 验证了该方法在软X射线等离子体密度诊断中的可行性. 关键词： 双频光栅 剪切干涉仪 软X射线 等离子体诊断     

Optical heterodyne grating shearing interferometry for long-range positioning applications

We develop a displacement measurement and positioning system with nanometer resolution over the millimeter traveling range. The method is based on a heterodyne grating shearing interferometry, a homemade lock-in amplifier and a servo control loop for displacement sensing and positioning. The quasi-common optical path configuration of our system provides better immunity against environmental disturbances. The experimental results demonstrate that our system can measure small and long displacement with nanometric resolution. The device achieves a positioning resolution of 2.3 nm over a traveling range of 20 mm.     

In-cylinder temperature field measurement with laser shearing interferometry for spark ignition engines

The temperature field in combustion chamber of spark ignition engine is measured using laser shearing interferometry and high-speed photography in this paper. A set of experimental facility is set up. The relationship equation between the interference fringe image and temperature distribution is deduced. Changing the shearing interferometry quantity, the two-dimensional temperature field of engine combustion chamber and flame propagation can be measured quantitatively by image processing. The test results indicate that the shearing interferometric method has a strong vibration resistance, and a simple and reliable optical path. The temperature distribution and the temperature gradient are different in different zones. The temperature is highest in the burning zone and the temperature gradient is large. The temperature is lower in the burned zone and the temperature gradient is smaller. The temperature is lowest in the unburned zone but the temperature gradient is large. At the initial period of combustion, the flame propagation velocity is low. In the combustion process, the flame front in the approximate spherical shape pushes toward the unburned zone, and the flame propagation velocity starts to decrease. It rapidly increases until it reaches the maximum value as the combustion process going on, and then it gradually decreases until it has burned in the entire combustion chamber.     

Lateral shear interferometry with holo shear lens

A simple method for obtaining lateral shear using holo shear lenses (HSL) has been discussed. This simple device which produces lateral shears in the orthogonal directions has been used for lens testing. The holo shear lens is placed at or near the focus of the lens to be tested. It has also been shown that HSL can be used in speckle shear interferometry as it performs both the functions of shearing and imaging.     

Implementation of electro-optic spectral shearing interferometry for ultrashort pulse characterization

Electro-optic spectral shearing interferometry is implemented for the highly sensitive characterization of ultrashort pulses from a free-running source. A simple phase-locked-loop clock recovery circuit is used to extract the high-frequency microwave clock signal to drive the phase modulator for spectral shearing. We demonstrate accurate full temporal characterization of 200-fs pulses from an optical parametric oscillator at 5-pW average power.