Dr. David A. Zimdars Profile

Dr. David A. Zimdars

Technology Program Manager at KLA

SPIE Involvement:

Author

Publications (25)

Proceedings Article | 2 May 2017 Presentation + Paper

Presentation + Paper

Non-destructive evaluation of specialty coating degradation using terahertz time-domain spectroscopy

Carley Nicoletti, Laura Cramer, Alan Fletcher, David Zimdars, Zafar Iqbal, John Federici

Proceedings Volume 10206, 102060W (2017) https://doi.org/10.1117/12.2258027

KEYWORDS: Nondestructive evaluation, Reflectance spectroscopy, Terahertz radiation, Spectroscopy, Ultraviolet radiation, Humidity, Testing and analysis, Refractive index, Data analysis, Coating, Multilayers, Reflectivity, Scanning electron microscopy

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The Terahertz Time Domain Reflection Spectroscopy (THz-TDS) method of paint layer diagnostics is a non-contact electromagnetic technique analogous to pulsed-ultrasound with the added capability of spectroscopic characterization. The THz-TDS sensor emits a near-single cycle electromagnetic pulse with a bandwidth from 0.1 to 3 THz. This wide bandwidth pulse is focused on the coating, and echo pulses are generated from each interface (air-coating, layer-layer, coating-substrate). In this paper, the THz-TDS method is applied to specialty aircraft coatings. The THz-TDS method is able to penetrate the whole coating stack and sample the properties of each layer. Because the reflected pulses from individual layers typically overlap in time, the complex permittivity function and thickness of each layer is determined by a best fit of the measured reflection (either in time or frequency domain) to a layered model of the paint. The THz- TDS method is applied to specialty coatings prior to and during accelerated aging on a series of test coupons. The coupons are also examined during aging using ATR (attenuated total reflectance)-FTIR spectroscopy, Raman scattering spectroscopy, and Scanning Electron Microscopy (SEM) to ascertain, quantify, and understand the breakdown mechanisms of the coatings. In addition, the same samples are characterized using THz-TDS techniques to determine if the THz-TDS method can be utilized as a non-destructive evaluation technique to sense degradation of the coatings. Our results suggest that the degradation mechanism begins in the top coat layer. In this layer, 254 nm UV illumination in combination with the presence of moisture works partially with oxides as catalysts to decompose the polymer matrix thereby creating porosity in the top coat layer. Since the catalytic effect is partial, loss of the oxides by chemical reaction can also occur. As the topcoat layer becomes more porous, it allows water vapor to permeate the topcoat layer and interact with the rain erosion layer via carbonization of the polymer matrix in the rain erosion layer. The presence of the salt accelerates the pitting degradation. The goal of this paper is to determine if THz-TDS can be used to sense degradation of the coating.

Proceedings Article | 7 March 2014 Paper

Paper

Model-based, one-sided, time-of-flight terahertz image reconstruction

Stephen Schmitt, Jeffrey Fessler, Greg Fichter, David Zimdars

Proceedings Volume 9020, 90200N (2014) https://doi.org/10.1117/12.2042282

KEYWORDS: Refraction, Reconstruction algorithms, Model-based design, Image restoration, Data acquisition, Nondestructive evaluation, Transmitters, Receivers, Foam, Terahertz radiation

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Proceedings Article | 27 April 2010 Paper

Paper

Portable video rate time domain terahertz line imager for security and aerospace nondestructive examination

David Zimdars, G. Fichter, C. Megdanoff, M. Murdock, Irl Duling, Jeffrey White, S. Williamson

Proceedings Volume 7671, 76710K (2010) https://doi.org/10.1117/12.850143

KEYWORDS: Terahertz radiation, Imaging systems, Nondestructive evaluation, Video, Reflection, Aerospace engineering, Scanners, Picosecond phenomena, Video surveillance, Inspection

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Proceedings Article | 15 April 2008 Paper

Paper

Quantitative measurement of laminar material properties and structure using time domain reflection imaging

David Zimdars, Jeffrey White, G. Fichter, A. Chernovsky, S. Williamson

Proceedings Volume 6949, 69490B (2008) https://doi.org/10.1117/12.777603

KEYWORDS: Reflection, Picosecond phenomena, Terahertz radiation, Interfaces, Refraction, Optical coatings, Nondestructive evaluation, Ultrasonography, Adhesives, Thin film coatings

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Proceedings Article | 4 May 2007 Paper

Paper

Terahertz measurement and imaging detection of delamination and water intrusion in ground based radome panels

David Zimdars, Jeffrey White, Gregg Sucha, G. Fichter, G. Stuk, C. Megdanoff, A. Chernovsky, S. Williamson

Proceedings Volume 6549, 654906 (2007) https://doi.org/10.1117/12.718732

KEYWORDS: Terahertz radiation, Foam, Reflection, Composites, Nondestructive evaluation, Control systems, Sensors, System integration, Picosecond phenomena, Dielectrics

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Proceedings Article | 4 May 2007 Paper

Paper

Terahertz interferometric imaging of RDX

Alexander Sinyukov, Robert Barat, Dale Gary, Zoi-Heleni Michalopoulou, Ivan Zorych, David Zimdars, John Federici

Proceedings Volume 6549, 654909 (2007) https://doi.org/10.1117/12.719234

KEYWORDS: Terahertz radiation, Interferometry, Sensors, Detector arrays, Spherical lenses, Absorption, Image resolution, Weapons, Explosives, Imaging systems

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Proceedings Article | 12 October 2006 Paper

Paper

Terahertz interferometric imaging of a concealed object

Alexander Sinyukov, Aparajita Bandyopadhyay, Amartya Sengupta, Robert Barat, Dale Gary, Zoi-Heleni Michalopoulou, David Zimdars, John Federici

Proceedings Volume 6373, 63730K (2006) https://doi.org/10.1117/12.685139

KEYWORDS: Terahertz radiation, Interferometry, Sensors, Detector arrays, Imaging systems, Spatial resolution, Metals, Explosives, Weapons, Absorption

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Proceedings Article | 19 May 2006 Paper

Paper

Terahertz interferometric and synthetic aperture imaging

Alexander Sinyukov, Aparajita Bandyopadhyay, Amartya Sengupta, Robert Barat, Dale Gary, Zoi-Heleni Michalopoulou, David Zimdars, John Federici

Proceedings Volume 6212, 62120Z (2006) https://doi.org/10.1117/12.664690

KEYWORDS: Terahertz radiation, Sensors, Interferometry, Metals, Detector arrays, Spatial resolution, Imaging systems, Explosives, Atmospheric propagation, Phase shifts

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Proceedings Article | 19 May 2006 Paper

Paper

Time domain terahertz detection of concealed threats in luggage and personnel

David Zimdars, Jeffrey White, G. Stuk, A. Chernovsky, G. Fichter, S. Williamson

Proceedings Volume 6212, 62120O (2006) https://doi.org/10.1117/12.665748

KEYWORDS: Terahertz radiation, Raster graphics, Transceivers, Transmitters, Reflection, Imaging systems, Millimeter wave imaging, Receivers, Homeland security, Explosives

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Proceedings Article | 19 May 2005 Paper

Paper

THz standoff detection and imaging of explosives and weapons

John Federici, Dale Gary, Robert Barat, David Zimdars

Proceedings Volume 5781, (2005) https://doi.org/10.1117/12.604695

KEYWORDS: Terahertz radiation, Explosives, Sensors, Interferometry, Weapons, Signal attenuation, Absorption, Atmospheric propagation, Imaging arrays, Standoff detection

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Proceedings Article | 18 May 2005 Paper

Paper

High-speed time domain terahertz security imaging

David Zimdars, Jeffrey White, Steven Williamson, G. Stuk

Proceedings Volume 5790, (2005) https://doi.org/10.1117/12.603467

KEYWORDS: Terahertz radiation, Transceivers, Raster graphics, Picosecond phenomena, Millimeter wave imaging, Image resolution, Scanners, Imaging systems, Femtosecond phenomena, Antennas

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Proceedings Article | 18 May 2005 Paper

Paper

Terahertz imaging using an interferometric array

John Federici, Dale Gary, Robert Barat, David Zimdars

Proceedings Volume 5790, (2005) https://doi.org/10.1117/12.603864

KEYWORDS: Terahertz radiation, Sensors, Interferometry, Phase measurement, Imaging arrays, Explosives, Imaging systems, Receivers, Weapons, Wavefronts

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Proceedings Article | 1 April 2005 Paper

Paper

High speed terahertz reflection imaging

David Zimdars

Proceedings Volume 5692, (2005) https://doi.org/10.1117/12.590897

KEYWORDS: Transceivers, Raster graphics, Terahertz radiation, Scanners, Femtosecond phenomena, Imaging systems, Millimeter wave imaging, Optical components, Transmitters, Receivers

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Proceedings Article | 25 March 2005 Paper

Paper

THz standoff detection and imaging of explosives and weapons

John Federici, Robert Barat, Dale Gary, David Zimdars

Proceedings Volume 5727, (2005) https://doi.org/10.1117/12.590377

KEYWORDS: Terahertz radiation, Sensors, Interferometry, Imaging arrays, Explosives, Imaging systems, Weapons, Near field, Wavefronts, Staring arrays

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Proceedings Article | 16 December 2004 Paper

Paper

Transfer function study of biological samples by the THz-TDS

Feng Huang, John Federici, Robert Barat, Dale Gary, David Zimdars

Proceedings Volume 5585, (2004) https://doi.org/10.1117/12.567681

KEYWORDS: Terahertz radiation, Spectroscopy, Biological research, Signal to noise ratio, Signal detection, Proteins, Statistical analysis, Apodization, Silicon, Interference (communication)

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Proceedings Article | 14 December 2004 Paper

Paper

Optical properties around resonance peaks by THz-TDS

Feng Huang, John Federici, Robert Barat, Dale Gary, David Zimdars

Proceedings Volume 5584, (2004) https://doi.org/10.1117/12.567687

KEYWORDS: Terahertz radiation, Absorption, Spectroscopy, Optical properties, Explosives, Transmittance, Phonons, Reflectivity, Refractive index, Oscillators

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Proceedings Article | 8 September 2004 Paper

Paper

Terahertz near-field interferometric and synthetic aperture imaging

Kenneth Walsh, Brian Schulkin, Dale Gary, John Federici, Robert Barat, David Zimdars

Proceedings Volume 5411, (2004) https://doi.org/10.1117/12.541525

KEYWORDS: Sensors, Spherical lenses, Wavefronts, Near field, Imaging arrays, Interferometry, Terahertz radiation, Signal to noise ratio, Synthetic aperture imaging, Explosives

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Proceedings Article | 8 September 2004 Paper

Paper

Terahertz reflection imaging for package and personnel inspection

David Zimdars, Jeffrey White

Proceedings Volume 5411, (2004) https://doi.org/10.1117/12.562216

KEYWORDS: Terahertz radiation, Reflection, Metals, Imaging systems, Transceivers, Inspection, Millimeter wave imaging, Ceramics, Opacity, Imaging spectroscopy

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Proceedings Article | 8 September 2004 Paper

Paper

Analysis of terahertz spectral images of explosives and bioagents using trained neural networks

Filipe Oliveira, Robert Barat, Brian Schulkin, Feng Huang, John Federici, Dale Gary, David Zimdars

Proceedings Volume 5411, (2004) https://doi.org/10.1117/12.542648

KEYWORDS: Terahertz radiation, Neural networks, Interferometry, Explosives, Sensors, Artificial neural networks, Neurons, LabVIEW, Biological research, Tolerancing

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Proceedings Article | 29 July 2003 Paper

Paper

Neural network analysis of terahertz spectra of explosives and bio-agents

Felipe Oliveira, Robert Barat, Brian Shulkin, John Federici, Dale Gary, David Zimdars

Proceedings Volume 5070, (2003) https://doi.org/10.1117/12.500875

KEYWORDS: Terahertz radiation, Neural networks, Metals, Explosives, Analytical research, Biological research, Matrices, Detector arrays, Imaging arrays, Reflectivity

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Proceedings Article | 29 July 2003 Paper

Paper

Fiber-pigtailed terahertz time domain spectroscopy instrumentation for package inspection and security imaging

David Zimdars

Proceedings Volume 5070, (2003) https://doi.org/10.1117/12.519632

KEYWORDS: Terahertz radiation, Receivers, Transmitters, Imaging systems, Inspection, Terahertz spectroscopy, Imaging spectroscopy, Metals, Explosives, Control systems

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Proceedings Article | 23 May 2000 Paper

Paper

Compact fiber-pigtailed terahertz imaging system

James Rudd, David Zimdars, Matthew Warmuth

Proceedings Volume 3934, (2000) https://doi.org/10.1117/12.386344

KEYWORDS: Terahertz radiation, Transmitters, Receivers, Optical fibers, Control systems, Millimeter wave imaging, Imaging systems, Image transmission, Spectroscopy, Imaging spectroscopy

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Proceedings Article | 27 July 1994 Paper

Paper

Picosecond vibrational photon echo experiments in liquids and glasses

David Zimdars, Andrei Tokmakoff, Beate Sauter, Scott Chen, Alfred Kwok, Michael Fayer

Proceedings Volume 2138, (1994) https://doi.org/10.1117/12.181368

KEYWORDS: Picosecond phenomena, Liquids, Glasses, Free electron lasers, Absorption, Temperature metrology, Germanium, Infrared radiation, Metals, Bragg cells

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Proceedings Article | 27 July 1994 Paper

Paper

Molecular energy transfer in condensed matter studied by ultrafast vibrational spectroscopy

Jeffrey Hill, Sheah Chen, Dana Dlott, Andrei Tokmakoff, Beate Sauter, David Zimdars, Michael Fayer

Proceedings Volume 2138, (1994) https://doi.org/10.1117/12.181345

KEYWORDS: Picosecond phenomena, Absorption, Proteins, Carbon monoxide, Free electron lasers, Infrared radiation, Energy transfer, Molecular energy transfer, Mid-IR, Solids

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Proceedings Article | 14 July 1993 Paper

Paper

Picosecond infrared vibrational photon echoes and lifetime measurements using the Stanford superconducting-accelerator-pumped free-electron laser

Michael Fayer, David Zimdars, Andrei Tokmakoff, Scott Chen, Scott Greenfield, Todd Smith, H. Alan Schwettman

Proceedings Volume 1854, (1993) https://doi.org/10.1117/12.148031

KEYWORDS: Liquids, Picosecond phenomena, Glasses, Temperature metrology, Free electron lasers, Infrared photography, Infrared radiation, Chromophores, Molecules, Crystals

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Showing 5 of 25 publications

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