Wide-field interferometric measurements of nonstationary complex coherence function

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.

A method of measuring the second-order degree of coherence in an arbitrary plane by means of a compact wavefront shearing interferometer is described. The prism interferometer previously described by Saunders produces two sheared images that interfere, allowing measurement of the degree of spatial coherence. If the degree of coherence is a function of coordinate differences only, the visibility is constant; otherwise it varies over the field. Experimental results are given.

Diffusion coefficients measured with a flowing junction cell and a wavefront shearing interferometer are reported. These coefficients were correlated with respect to solution concentration for three liquid systems: monoethanolamine‐water, diethanolamine‐water and triethanolamine‐water at 25°. Equations from fundamental electrolytic theory were used as a basis for correlation.

Turbulence coherence in complex wind field: Focusing on its on-site characteristics based on multi-point clustering

Method of generating a vortex array embedded in a partially coherent beam is proposed and experimentally demonstrated. The vortex array exists in the complex coherence function of a random field arising due to interference of three independent coherence functions with appropriate phase profiles. Existence of the vortex array is confirmed by presenting amplitude and phase distributions of the complex coherence function. The phase structure of the complex coherence function, embedded with a vortex array, is obtained by interfering it with an independent fourth coherence function known as a reference and applying the Fourier fringe analysis technique to the cross-covariance of the intensity of the resultant random field.

We propose a new analysis method of microtremor circular arrays for detecting phase velocities of Rayleigh waves in microtremors, aiming to conduct the microtremor array observations with fewer restriction of seismometer arrangement than the spatial autocorrelation (SPAC) method. The method is based on the complex coherence function (CCF) of the Rayleigh waves formulated by Shiraishi and Matsuoka (2005) to study the relationship between wave sources and observation points on an array. In this method, the values of the Bessel function J0 (kr) (k: wave number, r: distance between observation points) that generate phase velocities are obtained as a solution of the simultaneous equations of CCFs, while they are calculated from the directional average of CCFs in the SPAC method. Therefore, our method allows observation points not equally spaced on the circumference.From theoretical studies of this method for a circular array, it was found that seismometers on the circumference could be set at almost any place with the condition of symmetrical seismometer arrangement. Moreover, a field experiment have confirmed that the phase velocity obtained from the proposed method agreed with that of the SPAC method.

Complex self-coherence function determination using geometric phase techniques

We review the principle of coherence dynamics proposed recently to explain the origin of coherence vortices, which are the phase singularities in a complex coherence function. Some properties associated with coherence vortex, such as the coherence current describing the circular contrast flow close to a vortex core and conservation laws of coherence, are investigated both theoretically and experimentally.

Propagation of a coherent light through an anisotropic random medium generates randomly polarized field, known as polarization speckle. In this paper, an experimental technique is proposed and demonstrated to recover the transmittance of a polarized object from polarization speckle. Recovery of the polarized object from polarization speckle is made possible by combining the far-field intensity correlation of the object speckle with off-axis holography to determine the complex coherence function of the speckle. The desired object speckle which is uniformly polarized is filtered from the polarization speckle using a polarizer. The results are compared with the case where the complex coherence function is determined in the absence of the polarizer.

The optimal microphone array includes two processing blocks ‐ minimum variance distortionless response (MVDR) beamformer and the single‐channel Wiener filter, which acts as post‐filter. The main drawback of MVDR beamformer is the cancellation of the desired speech signal and its degradation in multi‐path wave propagation environment. To make the adaptive algorithm robust against room reverberation and to prevent desired signal cancellation, an estimation of the unknown desired speaker's transfer function was proposed. The estimation is based on the imperfect signal and the interference covariance matrices estimated from available microphone signals during speaker activity and pause of speech respectively. As MVDR beamformer suppresses coherent interference, post‐filter has to reduce diffuse acoustic noise. The post‐filter proposed in this paper is developed under assumption that complex coherence function is unknown but time invariant. The additional improvement of the post‐processing algorithm on low frequencies is obtained by combining a priori noise power attenuation factor for diffuse noise field with estimated one. The proposed algorithm is tested on simulated room with reverberation, and compared with some known post‐processing algorithms with rather good results.

Two-cell theory to measure membrane resistance based on proton flow: Theory development and experimental validation

We combine the measurements of luminosity dependence of bias with the luminosity dependent weak lensing analysis of dark matter around galaxies to derive the galaxy bias and constrain amplitude of mass fluctuations. We take advantage of theoretical and simulation predictions that predict that, while halo bias is rapidly increasing with mass for high masses, it is nearly constant in low mass halos. We use a new weak lensing analysis around the same Sloan Digital Sky Survey (SDSS) galaxies to determine their halo mass probability distribution. We use these halo mass probability distributions to predict the bias for each luminosity subsample. Galaxies below ${L}_{*}$ are antibiased with $b<1$ and for these galaxies bias is only weakly dependent on luminosity. In contrast, for galaxies above ${L}_{*}$ bias is rapidly increasing with luminosity. These observations are in an excellent agreement with theoretical predictions based on weak lensing halo mass determination combined with halo bias-mass relations. We find that for standard cosmological parameters theoretical predictions are able to explain the observed luminosity dependence of bias over six magnitudes in absolute luminosity. We combine the bias constraints with those from the Wilkinson Microwave Anisotropy Probe (WMAP) and the SDSS power spectrum analysis to derive new constraints on bias and ${\ensuremath{\sigma}}_{8}$. For the most general parameter space that includes running and neutrino mass, we find ${\ensuremath{\sigma}}_{8}=0.88\ifmmode\pm\else\textpm\fi{}0.06$ and ${b}_{*}=0.99\ifmmode\pm\else\textpm\fi{}0.07$. In the context of spatially flat models we improve the limit on the neutrino mass for the case of three degenerate families from ${m}_{\ensuremath{\nu}}<0.6\text{ }\text{ }\mathrm{e}\mathrm{V}$ without bias to ${m}_{\ensuremath{\nu}}<0.18\text{ }\text{ }\mathrm{e}\mathrm{V}$ with bias (95% C.L.), which is weakened to ${m}_{\ensuremath{\nu}}<0.24\text{ }\text{ }\mathrm{e}\mathrm{V}$ if running is allowed. The corresponding limit for $3\text{ }\mathrm{\text{massless}}+1\text{ }\mathrm{\text{massive}}$ neutrino is 1.37 eV.

The electromagnetic transition properties of the decuplet to octet baryon (Δ → Nγ) is studied within the framework of a hypercentral quark model. The confinement potential is assumed as a hypercentral coloumb plus linear potential. The transition magnetic moment and transition amplitude fM1 for the Δ → Nγ are in agreement with other theoretical predictions. The present result of the radiative decay width is found to be in excellent agreement with the experimental values reported by the particle data group over other theoretical model predictions.

We combine a telescopic imaging system with a common-path, lateral-shearing interferometer and use phase-shifting interferometry to measure the complex spatial coherence function (or mutual intensity) of a linearly-polarized optical field. Our telescopic design increases the numerical aperture of the system without distorting the shape of the wave front, and therefore without changing the phase difference between lateral positions in the optical field. Our method of generating lateral-sheared images introduces no additional astigmatism. To demonstrate the use of the interferometer we extract the information contained in the complex spatial coherence function to reconstruct the amplitude and phase of a coherent optical field, and we also show how the spatial coherence function evolves from a coherent field to a partially coherent one as light traverses a random multiple-scattering medium.

We investigate the possibility of interferometric optical field sensor with DMD forming a series of sampling interferometers in the pupil of an optical system. Our preliminary experiment validates the feasibility of our approach for the field reconstruction in the case of coherent field. We believe that this approach can be extended to sensing of speckle patterns and even incoherent fields, by analyzing not only the intensity and phase, but also the amplitude and the visibility of the interference patterns. Such analysis would yield the complete complex amplitude and/or coherence function, making the approach directly applicable to a wide range of inverse source problems in optics.