Chulmin Joo

Ralf K Heilmann7
Paul T Konkola6
Carl G Chen6
7Ralf K Heilmann
6Paul T Konkola
6Carl G Chen
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The Reflection Grating Spectrometer (RGS) on Constellation-X will require thousands of large gratings with very exacting tolerances. Two types of grating geometries have been proposed. In-plane gratings have low ruling densities (∼ 500 l/mm) and very tight flatness and assembly tolerances. Off-plane gratings require much higher ruling densities (∼ 5000(More)
We report on the measurement of the fringe-to-substrate phase error in our Nanoruler system. This system utilizes scanning beam interference lithography to pattern and measure large-area, nanometer-accuracy gratings that are appropriate for semiconductor and integrated opto-electronic metrology. We present the Nanonruler's metrology system that is based on(More)
Quantitative measurement of diffusive and directional processes of intracellular structures is not only critical in understanding cell mechanics and functions, but also has many applications, such as investigation of cellular responses to therapeutic agents. We introduce a label-free optical technique that allows non-perturbative characterization of(More)
We are developing a Scanning Beam Interference Lithography (SBIL) system. SBIL represents a new paradigm in semiconductor metrology, capable of patterning large-area linear gratings and grids with nanometer overall phase accuracy. Realizing our accuracy goal is a major challenge because the interference fringes have to be locked to a moving substrate with(More)
By interfering two small diameter Gaussian laser beams, scanning beam interference lithography ͑SBIL͒ is capable of patterning linear gratings and grids in resist while controlling their spatial phase distortions to the nanometer level. Our tool has a patterning area that is up to 300 mm in diameter. The motive for developing SBIL is to provide the(More)
The Reflection Grating Spectrometer (RGS) on Constellation-X is designed to supply astronomers with high spectral resolution in the soft x-ray band from 0.25 to 2 keV. High resolution, large collecting area and low mass at grazing incidence require very flat and thin grating substrates, or thin-foil optics. Thin foils typically have a diameter-to-thickness(More)
In scanning beam interference lithography, a resist-coated substrate is scanned under phase-locked interfering beams to pattern large gratings or grids with nanometer level distortions. To achieve design goals, it is required to measure the spatial period, phase, and rotation of the interference fringes in real-time with high precision. In this article, we(More)
Solar thermoelectric generators (STEGs), which are used for various applications, (particularly small size electronic devices), have optical concentration systems for high energy conversion efficiency. In this study, a refraction-assisted STEG (R-STEG) is designed based on phase-change materials. As the phase-change material (PCM) changes phase from solid(More)
Vortex flow imaging is a relatively new medical imaging method for the dynamic visualization of intracardiac blood flow, a potentially useful index of cardiac dysfunction. A reconstruction method is proposed here to quantify the distribution of blood flow velocity fields inside the left ventricle from color flow images compiled from ultrasound measurements.(More)
An implantable wireless optogenetic stimulation system with an LED-based optical stimulation cuff electrode was developed for peripheral nerve control. The proposed system consisted of a battery-powered optical cuff electrode, optical stimulation controller, and wireless communication system. The optical cuff electrode had a polydimethylsiloxane (PDMS)(More)