Fresnel zone

About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.

Multiple wavelength linear zone plate alignment apparatus and method

Abstract: An optical alignment apparatus and method for a semiconductor lithography mask and wafer utilizes two monochromatic light sources of different wavelengths. The mask contains targets in the form of linear Fresnel zone plates and the wafer contains a reflecting grating. Incident illumination from the two light sources illuminates the mask targets and is reflected from the wafer gratings in various intensity depending on the physical characteristics of the wafer and mask layers and thicknesses and by the targets. A detector detects the strongest of the diffracted return beams from each of the monochromatic light sources and uses the strongest to align the targets and grating on the mask and wafer for more accurate printing of mask patterns on the wafer.

Limits of applicability of the method of geometric optics and related problems

Abstract: We present on a heuristic basis the universal sufficient conditions for applicability of the method of geometric optics. In formulating the criteria, we make essential use of the concept of the "Fresnel volume" of a ray, whose boundary links the first Fresnel zones "threaded" on the ray. The fundamental criterion of applicability requires that the parameters of the medium and of the wave should vary little over the transverse section of the Fresnel volume. The second criterion, which stems from the first, requires that rays incident on the same given point should lie mostly outside the Fresnel volume of an adjacent ray. The effectiveness of these criteria has been demonstrated in many problems of electrodynamics and acoustics that allow a solution more precise than the ray solution. On the basis of the presented criteria, one can reveal the regions of inapplicability of the ray method (focal and caustic regions, penumbra regions in diffraction by screens and convex bodies, regions where lateral waves arise, etc.). If we know the dimensions of the regions of inapplicability, we can also solve a number of related problems. The most important of these problems are: the problem of determining the field in the neighborhood of caustics and foci and the problem of analyzing the wave pattern as a whole. The proposed criteria also allow a generalization to three-dimensional quantummechanical problems, while outlining the limits of applicability of the quasiclassical approximation.

Ultrasonic transducer probe system

Abstract: An ultrasonic transducer system comprises a one or two dimensional array of transducers which are subdivided into groups. The groups are selected and operated simultaneously in a manner to produce acoustic energy beams which provide an interference pattern in the near-field focal zone. The groups, moreover, are shifted incrementally along a predetermined direction to provide a scan along a workpiece surface. The transducer system, operating in a manner similar to a Fresnel zone lens, yields greatly improved image resolution, particularly when used in conjunction with a B- or C-scan presentation.

High-resolution lenses for sub-100 nm x-ray fluorescence microscopy

Abstract: We report on the design, fabrication, and testing of Fresnel zone plates for high-resolution x-ray fluorescence microscopy using the scanning x-ray microscope at the European Synchrotron Radiation Source. The germanium lenses were optimized for operation near the sulphur absorption edge at 2472 eV photon energy. The high measured diffraction efficiencies of up to 9.6% and the good match to the spatial coherence of the undulator beam resulted in a photon flux of about 4×108 photons per second within the bandwidth of a silicon 〈111〉 monochromator. Using a test object consisting of zinc sulphide nanostructures, we were able to image features in sulphur x-ray fluorescence mode with lateral dimensions down to below 100 nm.

Diffractional optics of millimetre waves

Abstract: Theory of diffraction. Short focusing Fresnel zone plates. Elements of diffraction quasioptics. Synthesis of diffractional elements. Diffractional antennae at millimetre wavelengths. The influence of surface form on the structure of Fresnel zones. Applications of diffractional optics and quasioptics. Diffractional antennae. Optical constants of materials at submillimetrics and millimetric wavelengths.