Search results for "Diffraction"
showing 10 items of 1584 documents
Measuring Inaccessible Residual Stresses Using Multiple Methods and Superposition
2010
The traditional contour method maps a single component of residual stress by cutting a body carefully in two and measuring the contour of the cut surface. The cut also exposes previously inaccessible regions of the body to residual stress measurement using a variety of other techniques, but the stresses have been changed by the relaxation after cutting. In this paper, it is shown that superposition of stresses measured post-cutting with results from the contour method analysis can determine the original (pre-cut) residual stresses. The general superposition theory using Bueckner’s principle is developed and limitations are discussed. The procedure is experimentally demonstrated by determini…
Fractal-structured multifocal intraocular lens
2017
[EN] In this work, we present a new concept of IOL design inspired by the demonstrated properties of reduced chromatic aberration and extended depth of focus of Fractal zone plates. A detailed description of a proof of concept IOL is provided. The result was numerically characterized, and fabricated by lathe turning. The prototype was tested in vitro using dedicated optical system and software. The theoretical Point Spread Function along the optical axis, computed for several wavelengths, showed that for each wavelength, the IOL produces two main foci surrounded by numerous secondary foci that partially overlap each other for different wavelengths. The result is that both, the near focus an…
Fractal zone plates with variable lacunarity.
2009
Fractal zone plates (FZPs), i.e., zone plates with fractal structure, have been recently introduced in optics. These zone plates are distinguished by the fractal focusing structure they provide along the optical axis. In this paper we study the effects on this axial response of an important descriptor of fractals: the lacunarity. It is shown that this parameter drastically affects the profile of the irradiance response along the optical axis. In spite of this fact, the axial behavior always has the self-similarity characteristics of the FZP itself.
Fabrication of Diffractive Optics: Surface Reliefs and Artificial Dielectrics
1997
After a period of fundamental theoretical research, the field of diffractive optics is now reaching a time of assessment, when we can define the useful limits of each design procedure. Selecting a suitable procedure derives from a compromise between several factors, including design time, desired optical efficiency, and precision. A major consideration in finding such a compromise has been, and still is today, the availability of technologies which can realize the design by generating the diffracting structure with assigned tolerances.
Experimental observation of temporal dispersion gratings in fiber optics
2017
We experimentally demonstrate a temporal analog to the diffraction optical grating in the Fraunhofer formalism. Using amplitude and phase temporal periodic modulations, we show that the accumulation of dispersion in fiber optics induces the development of temporally well-separated sidebands similar to the spatial orders of diffraction that are commonly observed in an optical grating operating in the far field.
Devil’s vortex-lenses
2009
In this paper we present a new kind of vortex lenses in which the radial phase distribution is characterized by the "devil's staircase" function. The focusing properties of these fractal DOEs coined Devil's vortex-lenses are analytically studied and the influence of the topological charge is investigated. It is shown that under monochromatic illumination a vortex devil's lens give rise a focal volume containing a delimited chain of vortices that are axially distributed according to the self-similarity of the lens.
Acetonitrile inclusion complexes of piperazine-based macrocycles
1995
New piperazine-based macrocycles with single small cavities were prepared by using high dilution technique. The inclusion of acetonitrile into the cavity (7, 8) or clathrate formation (3) was studied by 1H-NMR spectroscopy in solution and by X-ray diffraction in the crystalline state. The cycle 3 forms a molecular cleft, a molecular pocket, where the acetonitrile molecule is held by four weak N…H interactions reinforcing the clathrate formation. The cycles 7 and 8 contain a rigid cavity for an exact sterical fit with the methyl group of a linear compound like acetonitrile. The acetonitrile inclusion complex with 7 proved to be stable under normal conditions and was studied by means of therm…
Coupling of Benzynezirconocene with 1,4-Diphenyl-1,3-butadiyne
2000
The thermolysis of diphenylzirconocene in the presence of 1,4-diphenyl-1,3-butadiyne to yield the seven-membered zirconacyclocumulene 1 via the intermediacy of benzynezirconocene is described. This complex has been characterized by an X-ray diffraction study. Additionally, better knowledge of the bonding of the cumulene moiety was achieved by DFT calculations. Cleavage of the Zr−C bonds of 1 with methanol provided the corresponding butatriene 2.
Small-x, Diffraction and Vector Mesons
2015
This talk discusses recent progress in some topics relevant for deep inelastic scattering at small x. We discuss first differences and similarities between conventional collinear factorization and the dipole picture of deep inelastic scattering. Many of the recent theoretical advances at small x are related to taking calculations in the nonlinear saturation regime to next-to-leading order accuracy in the QCD coupling. On the experimental side significant recent progress has been made in exclusive and diffractive processes, in particular in ultraperipheral nucleus-nucleus collisions.
Hard diffraction in photoproduction with Pythia 8
2019
We present a new framework for modeling hard diffractive events in photoproduction, implemented in the general purpose event generator Pythia 8. The model is an extension of the model for hard diffraction with dynamical gap survival in pp and ppbar collisions proposed in 2015, now also allowing for other beam types. It thus relies on several existing ideas: the Ingelman-Schlein approach, the framework for multiparton interactions and the recently developed framework for photoproduction in gamma p, gamma gamma, ep and $e^+e^-$ collisions. The model proposes an explanation for the observed factorization breaking in photoproduced diffractive dijet events at HERA, showing an overall good agreem…