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Publications

Search Publications by

Thomas A. Germer (Fed)

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Displaying 1 - 25 of 189

Size-Monodisperse Metal Nanoparticles Via Hydrogen-Free Spray Pyrolysis

October 12, 2021
Author(s)
Jae H. Kim, Thomas Germer, George W. Mulholland, S H. Ehrman
Pure copper nanoparticles were produced using a co-solvent approach avoiding use of hydrogen or other reducing gas. Compared with the particles formed without the co-solvent, the addition of alcohol has a significant effect in preventing oxidation, which

Depolarization in diffusely scattering media

April 22, 2021
Author(s)
Thomas 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 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

Structured Illumination Mueller Matrix Imaging

May 16, 2019
Author(s)
Joseph P. Angelo, Thomas Germer, Maritoni Litorja
We perform Mueller matrix imaging (MMI) of diffusely scattering phantoms under sinusoidal irradiance of varying spatial frequency. Quantitative polarimetric sensing via MMI completely characterizes a sample's polarimetric properties, while structured

Imaging linear and circular polarization features in leaves with complete Mueller matrix polarimetry

June 1, 2018
Author(s)
C.H. L. Patty, David Luo, Frans Snik, Freek Ariese, Wybren J. Buma, Inge L. ten Kate, Rob J. van Spanning, William Sparks, Thomas Germer, Gy?z? Garab, Michael W. Kudenov
Spectropolarimetry of intact plant leaves allows to probe the molecular architecture of vegetation photosynthesis in a non-invasive and non-destructive way and, as such, can offer a wealth of physiological information. In addition to the molecular signals

Waveguide coupling via magnetic gratings with effective strips

April 14, 2018
Author(s)
Kevin Roccapriore, David Lyvers, Dean Brown, Ekaterina Poutrina, Augustine Urbas, Thomas Germer, Vladimir Drachev
Gratings with complex multilayer strips are studied under inclined incident light. Great interest in these gratings is due to applications as input/output tools for waveguides and as subwavelength metafilms. The structured strips introduce anisotropy in

Modeling the polarized X-ray scattering from periodic nanostructures with molecular anisotropy

December 1, 2017
Author(s)
Christopher D. Liman, Thomas A. Germer, Daniel F. Sunday, Dean M. DeLongchamp, Regis J. Kline
We discuss a new technique to measure molecular orientation in nanostructures using resonant soft X-rays. This technique is based on a variable angle transmission measurement called critical dimension X-ray scattering that enables the characterization of

Plasma nanotexturing of silicon surfaces for photovoltaics applications: Influence of initial surface finish on the evolution of topographical and optical properties

November 27, 2017
Author(s)
Guillaume Fischer, Etienne Drahi, Martin Foldyna, Thomas Germer, Erik V. Johnson
Using a plasma to generate a surface texture with feature sizes on the order of nanometers ("nanotexturing") is a promising technique being considered for application in thin, high- efficiency crystalline silicon solar cells. This study investigates the

Scattered Light Analysis of Birefringent Coatings for Distributed Polarization Rotators

October 20, 2016
Author(s)
Katelynn A. Sharma, Thomas Germer, Christopher Smith, Jonathan Zuegel, James B. Oliver, Thomas G. Brown
We characterize scattered light in polarization optics designed to maintain uniform illumination on target during spherical direct drive fusion experiments. An optical scatter instrument is used to measure the scatter distribution in the forward and