Minseung Ahn

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The authors report on the fabrication of 200 nm period blazed transmission gratings on silicon-on-insulator ͑SOI͒ wafers. These critical angle transmission ͑CAT͒ gratings require 3 – 5 ␮m tall freestanding grating bars with a very high aspect ratio ͑Ͼ100͒ and smooth sidewalls. In order to meet the challenging geometrical requirements, they modified and(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)
The authors report a silicon-on-insulator ͑SOI͒ process for the fabrication of ultrahigh aspect ratio freestanding gratings for high efficiency x-ray and extreme ultraviolet spectroscopy. This new grating design will lead to blazed transmission gratings via total external reflection on the grating sidewalls for x rays incident at graze angles below their(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)
We have developed a new type of soft x-ray diffraction grating. This critical-angle transmission (CAT) grating combines the advantages of traditional transmission gratings (low mass, extremely relaxed alignment and flatness tolerances) with those of x-ray reflection gratings (high efficiency due to blazing in the direction of grazing-incidence reflection,(More)
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)
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)
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)