MM-wave spatial interferometry as an alternative to radar for coherent point sources

In this paper we present the basic method for determining the range and bearing of objects by performing spatial interferometry upon the mm-wave phasefront it radiates. A three-port quasi-optical circuit is used as an example of how this technique may be employed. The paper considers the simplest possible case of locating a single coherent source in order to establish the basic principles of the method.     

Two-pion interferometry for a partially coherent evolution source

We give the formulas of two-pion Hanbury-Brown-Twiss (HBT) correlation function for a partially coherent evolution pion-emitting source, using quantum probability amplitudes in a path-integral formalism. The multiple scattering of the particles in the source is taken into consideration based on Glauber scattering theory. Two-pion interferometry with effects of the multiple scattering and source collective expansion is examined for a partially coherent source of hadronic gas with a finite baryon density and evolving hydrodynamically. We do not find observable effect of either the multiple scattering or the source collective expansion on HBT chaotic parameter.     

Two-pion interferometry for a partially coherent evolution source

We give the formulas of two-pion Hanbury-Brown-Twiss (HBT) correlation function for a partially coherent evolution pion-emitting source,using quantum probability amplitudes in a path-integral formalism.The multiple scattering of the particles in the source is taken into consideration based on Glauber scattering theory.Two-pion interferometry with effects of the multiple scattering and source collective expansion is examined for a partially coherent source of hadronic gas with a finite baryon density and evolving hydrodynamically.We do not find observable effect of either the multiple scattering or the source collective expansion on HBT chaotic parameter.     

Determination of the torsional stiffness of an azimuth tube with a stiffened opening by holographic interferometry

This paper deals with the determination of the torsinal stiffness of an important component of antenna structures, namely, the azimuth tube, by holographic interferometry. Experimental investigations were carried out on a structural model of an azimuth tube with an opening and a slip joint at its mid-height. In addition to the determination of the torsional stiffness, the technique was successfully employed to isolate the rotational slip at the splice joint. The results of the experimental investigation compare favourably with those obtained by finite element analysis for the cases of an azimuth tube with unstiffened and stiffened openings. The work indicates that valuable quantitative information can be obtained by holographic interferometry and associated techniques.     

Free-space terminator and coherent broadband blackbody interferometry

We propose a free-space terminator and broadband interferometry based on a coherent blackbody effect in an ultrathin nonreflecting metallic layer in the microwave to infrared domains. A frequency-insensitive device consisting of a metallic layer in a ring (Sagnac) interferometer can be used for autocorrelation measurements of extremely broad EM spectra.     

Temperature measurements by coherent Rayleigh scattering

We demonstrate, for the first time to our knowledge, the utility of coherent Rayleigh scattering (CRS) for temperature measurements in low-density gases and weakly ionized plasmas by measuring the translational temperature of neutral argon in a glow discharge. By analysis of the near-Gaussian spectral profile of the CRS signal, we determine temperatures with an uncertainty of 相似文献   

部分相干光栅衍射效应和干涉术

本文提出一种新的部分相干照明的光栅衍射干涉仪.先分析了光栅的介于Talbot和Lan效应之间的部分相干衍射效应.部分相干干涉图的特点是条纹由频率成倍的两种光栅状载波所表征.调整光源狭缝,系统在两相干性极端分别转成Talbot和Lau干涉仪.理论分析采用了模糊函数方法.最后给出了实验.     

Effective absorption coefficient measurements in PMMA and PTFE by clean ablation process with a coherent VUV source at 125 nm

First measurements of effective absorption coefficient and penetration depth are given here from the ablation of poly-methylmethacrylate (PMMA) and poly-tetrafluoroethylene (PTFE) samples at 125 nm (≈10 eV). The coherent VUV source used which provides smooth, efficient and clean etched areas, is briefly described. Experimental curves of etch depth as a function of the number of laser shots and etch rate as a function of energy density are obtained and compared with previous works performed at 157 nm (F₂ laser) and 193 nm (ArF laser). Experimental results are described with a Beer–Lambert absorption law and discussed. Received: 2 March 1999 / Accepted: 8 March 1999 / Published online: 11 August 1999     

Quantum interferometry via a coherent state mixed with a squeezed number state

We theoretically investigate the phase sensitivity with parity measurement on a Mach–Zehnder interferometer with a coherent state combined with a squeezed number state. Within a constraint on the total mean photon number, we find, via parity measurement, that the mixing of a coherent state and squeezed number state can give better phase sensitivity than mixing a coherent state and squeezed vacuum state when the phase shift deviates from the optimal phase φ= 0. In addition,we show that the classical Fisher information for parity measurement saturates the quantum Fisher information when the phase shift approaches to zero. Thus, the quantum Crame′r–Rao bound can be reached via the parity measurement in the case of φ= 0.     

Two improved methods of surface-displacement measurements by holographic interferometry

This paper describes two new methods for measuring surface-displacements. The first method is an improvement of Ennos' scheme in that multiple object beams are used instead of multiple hologram plates. This arrangement enables the three fringe patterns required for calculating displacement components to be viewed from the same direction, i.e., normal view. Thus the necessity of laborious fringe reprojection is eliminated. The second method involves making three holograms, one situated on each of the three coordinate axes assigned to the surface. Each hologram picks up one component of displacement. Hence no separation of displacement components is required. An experimental demonstration is presented which utilizes the first technique and checks with theoretical predictions.     

相干点源照明时消球差光学系统的像场结构

利用矢量傅里叶变换和稳相法获得了相干点源位于光轴上任意位置时，消球差光学系统像场结构的积分表达式，详细研究了使用线偏振光照明时像平面上大物方孔径角对像场结构的影响.模拟计算表明，在像空间垂直于光轴的平面上，如果物方孔径角较大，磁场分布绕光轴旋转90°后不再与电场分布相同，电场能量密度、磁能量密度和玻印亭矢量分布的等高线始终近似为椭圆，并且物方孔径角是导致玻印亭矢量分布失去圆对称性的主要因素.同时当使用小像方孔径角时，电场能量密度分布形状的长轴方向垂直于物空间电场的振动方向；随着像方孔径角逐渐增大，电场能量密度分布形状的长轴方向将逐渐变为与物空间电场的振动方向相同.这些结论完全不同于以前理论所预测的结果. 关键词： 成像系统 像场结构 矢量傅里叶变换 稳相法     

Single-optical-element soft-x-ray interferometry with a laser-plasma x-ray source

We report on a compact interferometer for the water-window soft-x-ray range that is suitable for operation with laser-plasma sources. The interferometer consists of a single diffractive optical element that focuses impinging x rays to two focal spots. The light from these two secondary sources forms the interference pattern. The interferometer was operated with a liquid-nitrogen jet laser-plasma source at lambda=2.88 nm. Scalar wave-field propagation was used to simulate the interference pattern, showing good correspondence between theoretical and experimental results. The diffractive optical element can simultaneously be used as an imaging optic, and we demonstrate soft-x-ray microscopy with interferometric contrast enhancement of a phase object.     

Measurement of the coherent neutron scattering length of 3He by neutron interferometry

A precise determination of the coherent scattering length of ³He with a neutron interferometer yields a value a_c = 4.29 ± 0.04 fm. A comparison with varoous theoretical perdictions is made and its relation to the few-body problem is discussed. A combination with other experimental results yield as most probable values for the free singlet- and triplet scattering length a_s = 8.0 ± fm and a_t = 3.05 ± 0.07 fm, respectively.     

Refractive index distribution measurements by means of spectrally-resolved white-light interferometry

A new procedure to measure the spatial distribution of the refractive index in transparent media is presented. It is based on the spectral analysis of optical interferograms obtained from a wide, continuous-spectrum light source. The method yields fairly high precision (up to 10^-8) in the measurements of local values of differential refractive index, Δn (Δn=n−n_ref), along a line in the sample. By means of a CCD TV-camera linked to a microcomputer, fast recording and automatic data processing are achieved. As an application, we present an experimental study of a thermal gradient in a liquid sample.     

浅海低频长线阵声源方位估计*

浅海大孔径水平阵信号估计近端射的低频声源方位时, 常规波束形成会产生明显的波束偏移和分裂现象, 从而造成单声源方位估计偏差。针对这一问题, 提出一种基于块稀疏压缩感知的声源方位估计方法。根据简正模理论, 将水平阵接收声场表示为方位角空间的块稀疏信号模型, 并通过块正交匹配追踪算法进行方位估计。仿真和2011年北黄海实验数据结果表明所提块正交匹配追踪方法可实现浅海波导环境下低频近端射的单个声源方位的准确估计。     

Simple quantum systems as a source of coherent information

A set of very important simple quantum systems is analyzed from the standpoint of the amount of coherent information that is accessible when information channels corresponding to the systems are used. It is shown that for simple quantum models the coherent information can be calculated and used for estimating the potential possibilities of the corresponding quantum channel as a source of physical information in experiments associated with the effects of the coherence of quantum states. The following physical models are studied: a two-level atom in a laser radiation field, an aggregate of two two-level subsystems in a multilevel atom (hydrogen), a system of two two-level atoms in the process of joint quantum-deterministic evolution and under the action of transformations of quantum measurement and quantum duplication, as well as one and two two-level atoms in the process of emission.