Minseung Ahn

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We present a spectrometer design based on a novel nanofabricated blazed X-ray transmission grating which is modeled to have superior efficiency. Here we outline a full instrument design proposed for Constellation-X which is expected to give resolving powers ~2000 (HEW). The spectrometer advantages include lower mass budget and smaller diffractor area, as(More)
This paper describes the development of a planar distributed tactile display, and tests its effectiveness for displaying textures. The tactile display is composed of a 6×5 pin array actuated by 30 piezoelectric bimorphs. The pins lie on 1.8 mm centers. Vertical excursion of each pin is controlled over a 0-0.7mm range. Perceptual experiments were conducted(More)
Diffraction gratings are ubiquitous wavelength dispersive elements for photons as well as for subatomic particles, atoms, and large molecules. They serve as enabling devices for spectroscopy, microscopy, and interferometry in numerous applications across the physical sciences. Transmission gratings are required in applications that demand high alignment and(More)
Volume x-ray gratings consisting of a multilayer coating deposited on a blazed substrate can diffract with very high efficiency, even in high orders if diffraction conditions in-plane (grating) and out-of-plane (Bragg multilayer) are met simultaneously. This remarkable property, however, depends critically on the ability to create a structure with near(More)
The authors report on the fabrication of 200 nm period blazed transmission gratings on silicon-on-insulator SOI wafers. These critical angle transmission CAT gratings require 3–5 m tall freestanding grating bars with a very high aspect ratio 100 and smooth sidewalls. In order to meet the challenging geometrical requirements, they modified and improved our(More)
We report on measurements of the diffraction efficiency of 200-nm-period freestanding blazed transmission gratings for wavelengths in the 0.96 to 19.4 nm range. These critical-angle transmission (CAT) gratings achieve highly efficient blazing over a broad band via total external reflection off the sidewalls of smooth, tens of nanometer thin ultrahigh(More)
We report on recent progress in developing diffraction gratings which can potentially provide extremely high spectral resolution of 10-10 in the EUV and soft x-ray photon energy ranges. Such a grating was fabricated by deposition of a multilayer on a substrate which consists of a 6-degree blazed grating with a high groove density. The fabrication of the(More)