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Search Publications by: Thomas A. Germer ()

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Displaying 1 - 25 of 384

Instrument Development for Spectroscopic Ellipsometry and Diffractometry in the EUV

April 24, 2024
Author(s)
Stephanie Moffitt, Bryan Barnes, Thomas A. Germer, Steven Grantham, Eric Shirley, Martin Sohn, Daniel Sunday, Charles S. Tarrio
Semiconductor devices are noted for ever-decreasing dimensions but now are also becoming more complex. While scanning probe microscopy can still resolve the smallest features, it does not have the throughput for high-volume characterization of full wafers

NIST efforts in extreme-ultraviolet metrology

November 21, 2023
Author(s)
Charles S. Tarrio, Steven Grantham, Rob Vest, Thomas A. Germer, Bryan Barnes, Stephanie Moffitt, Brian Simonds, Matthew Spidell
For several decades, the National Institute of Standards and Technology (NIST) has actively supported metrology programs for extreme ultraviolet (EUV) lithography. We will describe our existing programs in optics lifetime, reflectometry, and radiometry

Spatial frequency domain Mueller matrix imaging

December 14, 2022
Author(s)
Joseph Chue-Sang, Maritoni Litorja, Aaron Goldfain, Thomas A. Germer
Significance: Mueller matrix polarimetry (MMP) and spatial frequency domain imaging (SFDI) are wide-field optical imaging modalities that differentiate tissue primarily by structure alignment and photon transport coefficient, respectively. Because these

Depolarization in diffusely scattering media

April 22, 2021
Author(s)
Thomas A. Germer
We performed Mueller matrix Monte Carlo simulations of the propagation of optical radiation in diffusely scattering media for collimated incidence and report depolarization in the the transmitted rays as a function of thickness, the angle subtended by the

Spatial frequency domain Mueller matrix imaging

April 22, 2021
Author(s)
Joseph Chue-Sang, Aaron Goldfain, Jeeseong C. Hwang, Thomas A. Germer
We combine Mueller matrix polarimetry (MMP) with spatial frequency domain imaging (SFDI) to create a technique that is sensitive to near-surface material anisotropy. We demonstrate this imaging modality with scattering and absorbing phantoms and with a

Spectropolarimetry of primitive phototrophs as global surface biosignatures

February 4, 2021
Author(s)
William Sparks, M. N. Parenteau, Robert E. Blankenship, Thomas Germer, C.H. L. Patty, Kimberly M. Bott, Charles M. Telesco, Victoria S. Meadows
Photosynthesis is an ancient metabolic process that began on the early Earth, offering plentiful energy to organisms that utilize it, to the extent that they can achieve global significance. The potential exists for similar processes to operate on

Evolution of transmitted depolarization in diffusely scattering media

June 1, 2020
Author(s)
Thomas A. Germer
We performed Mueller matrix Monte Carlo simulations of the propagation of optical radiation in diffusely scattering media for collimated incidence and report the results as a function of thickness and the angle subtended by the detector. For sufficiently

Scattering mechanism for quadratic evolution of depolarization

January 15, 2020
Author(s)
Thomas A. Germer
It was recently demonstrated theoretically, when the polarimetric properties of a material depend only upon the direction transverse to that of propagation (long coherence length regime), depolarization in transmission evolves quadratically with material

Modelling photovoltaic soiling losses through optical characterization

January 9, 2020
Author(s)
Greg P. Smestad, Thomas Germer, Hameed Alrashidi, Eduardo F. Fern?ndez, Sumon Dey, Paidisetty S. Kumar, Honey Brahma, Aritra Ghosh, Nazmi Sellami, Ibrahim A. Hassan, Amal Kasry, Bala Pesala, S. Senthilarasu, Florencia Almonacid, K. S. Reddy, Tapas K. Mallick, Leonardo Micheli
The accumulation of soiling on photovoltaic (PV) modules affects PV systems worldwide. Soiling consists of mineral dust, soot particles, aerosols, pollen, fungi and/or other contaminants that deposit on the surface of PV modules. Soiling absorbs, scatters

Classical polarimetry with a twist: a compact, geometric approach

May 22, 2019
Author(s)
William Sparks, Thomas Germer, Rebecca M. Sparks
We present an approach to classical polarimetry which requires no moving parts, is compact and robust, and which encodes the complete polarization information on a single data frame, accomplished by replacing the rotation of components such as wave plates

Uncertainty in global downwelling plane irradiance estimates from sintered polytetra fluoroethylene plaque radiance measurements

May 20, 2019
Author(s)
Alexandre Castagna, B. Carol Johnson, Kenneth Voss, Heidi M. Dierssen, Heather Patrick, Thomas Germer, Zhehai Shang
Global downwelling plane irradiance is a necessary variable to normalize the water-leaving radiance measurements, reducing the magnitude and spectral variabilities introduced by the incident light field. As a result, the normalized measurements, known as