Search results for "Diffraction"
showing 10 items of 1584 documents
Broadband space-variant Fresnel processor
2002
We present a radically new class of optical setup working with white-light illumination, namely, a chromatically compensated processor operating in the Fresnel domain. The optical configuration is a hybrid (diffractive-refractive) three-lens system that exhibits an intermediate achromatic Fresnel plane and an output image plane without chromatic distortion. As a first application of this optical arrangement we develop a parallel space-variant color pattern-recognition experiment with white light.
Gaussian pulse propagation in dispersion-managed systems using chirped fiber gratings with group delay ripples
2005
We study the propagation of Gaussian-shaped pulses in grating-compensated dispersion-managed systems with group delay ripples (GDR). We show that the intersymbol interference caused by the GDR in gratings can be substantially reduced by nonlinear optical loop mirrors and the 40-Gb/s system performance can achieve transoceanic transmission in the presence of amplifier noise and random variations in ripple period of the gratings along the transmission line.
Phase conjugation in BaTiO 3 by use of the indirect photorefractive coupling of orthogonally polarized light waves
1998
A phase-conjugate wave is generated when an ordinary (extraordinary) signal wave is mixed with two counterpropagating extraordinary (ordinary) waves in the plane normal to the BaTiO3 polar axis. The photorefractive grating that couples the ordinary and the extraordinary waves appears if the incident waves induce a noticeable conical parametric scattering; this grating is a difference grating of many noisy scattering gratings recorded by means of the usual diffusion-mediated charge transport. For comparable intensities of signal and pump waves this type of nonlinear wave mixing is much more efficient than that which is due to the circular bulk photovoltaic effect.
Specular reflection of spin-polarized electrons from the W(001) spin-filter crystal in a large range of scattering energies and angles
2015
Extending previous work on the imaging spin-filter technique based on electron diffraction from W(001) in the specular (00)-LEED (low-energy electron diffraction) spot, we studied the scattering-energy and angle-of-incidence landscape of spin sensitivity $S$ and reflectivity ${I/I}_{0}$. The setup includes a spin-polarized GaAs electron source and a rotatable delay-line detector for spatially resolving detection. We measured the intensity and spin asymmetry of the specularly reflected beam for energies between 14 and 37 eV and angles of incidence between ${30}^{\ensuremath{\circ}}$ and ${60}^{\ensuremath{\circ}}$. Resulting energy-angular landscapes show rather good agreement with theory [r…
Axial resonance of periodic patterns by using a Fresnel biprism.
2013
This paper proposes a method for the generation of high-contrast localized sinusoidal fringes with spatially noncoherent illumination and relatively high light throughput. The method, somehow similar to the classical Lau effect, is based on the use of a Fresnel biprism. It has some advantages over previous methods for the noncoherent production of interference fringes. One is the flexibility of the method, which allows the control of the fringe period by means of a simple axial shift of the biprism. Second is the rapid axial fall-off in visibility around the high-contrast fringe planes. And third is the possibility of creating fringes with increasing or with constant period as the light bea…
Talbot interferometry: a new geometry
1993
Abstract With the Talbot effect, planes are found where the Fresnel diffraction pattern, of a Ronchi ruling, exhibits zero visibility. These planes are exploited to propose a novel geometry for Talbot interferometry, which has high sensitivity. Experimental verifications are included.
Chandra Observation of the Persistent Emission from the Dipping Source XB 1916-053
2006
We present the results of a 50 ks long Chandra observation of the dipping source XB 1916-053. During the observation two X-ray bursts occurred and the dips were not present at each orbital period. From the zero-order image we estimate the precise X-ray coordinates of the source with a 90% uncertainty of 0.6''. In this work we focus on the spectral study of discrete absorption features, during the persistent emission, using the High Energy Transmission Grating Spectrometer on board the Chandra satellite. We detect, for the first time in the 1st-order spectra of XB 1916-053, absorption lines associated to Ne X, Mg XII, Si XIV, and S XVI, and confirm the presence of the Fe XXV and Fe XXVI abso…
States of 13C with abnormal radii
2016
Differential cross-sections of the elastic and inelastic 13C + α scattering were measured at E(α) = 90 MeV. The root mean-square radii () of 13C nucleus in the states: 8.86 (1/2−), 3.09 (1/2+) and 9.90 (3/2−) MeV were determined by the Modified diffraction model (MDM). The radii of the first two levels are enhanced compared to that of the ground state of 13C, confirming the suggestion that the 8.86 MeV state is an analogue of the Hoyle state in 12C and the 3.09 MeV state has a neutron halo. Some indications to the abnormally small size of the 9.90 MeV state were obtained. peerReviewed
Brewster angle microscopy and X-ray GID studies of morphology and crystal structure in monolayers of N-tetradecyl-γ,δ-dihydroxypentanoic acid amide
1997
First-order phase transitions from the low-density fluidlike phase to the condensed phase of monolayers of N-tetradecyl-γ,δ-dihydroxypentanoic acid amides at the air−water interface have been studied by π−A isotherms, Brewster angle microscopy (BAM), and synchrotron X-ray grazing incidence diffraction (GID). The thermodynamic differences between enantiomeric and racemic monolayers are too small to be measured. However, chiral discrimination is observable in the macroscopic domain morphology by BAM. The domains of the condensed phase grow dendritically. The characteristic shapes of domains of the pure S and R enantiomers are mirror images of each other. The domains of the racemic mixture are…
Orientational Ordering ofN2OMolecules Adsorbed on Graphite (0001): A Novel Commensurate Pinwheel Structure
2000
The structure and orientational ordering of N2O molecules physisorbed on graphite (0001) is investigated applying x-ray, neutron, and low-energy electron diffraction techniques. Combining the results of the three techniques, we find that N2O forms a highly ordered, hexagonal, commensurate (sqrt[21]xsqrt[21])R10.89 degrees phase. The unit cell contains seven molecules which are arranged in a seven-sublattice pinwheel structure, unexpected for linear molecules on a hexagonal lattice. Potential energy calculations corroborate these results.