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Search Publications by: Marla L. Dowell (Fed)

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Displaying 1 - 25 of 50

Advancing Measurement Science for Microelectronics: CHIPS R&D Metrology Program

February 13, 2024
Author(s)
Marla L. Dowell, Hannah Brown, Gretchen Greene, Paul D. Hale, Brian Hoskins, Sarah Hughes, Bob R. Keller, R Joseph Kline, June W. Lau, Jeff Shainline
The CHIPS and Science Act of 2022 called for NIST to "carry out a microelectronics research program to enable advances and breakthroughs....that will accelerate the underlying R&D for metrology of next-generation microelectronics and ensure the

Radio Spectrum Occupancy Measurements Amid COVID-19 Telework and Telehealth

October 14, 2022
Author(s)
Dan Kuester, Xifeng Lu, Dazhen Gu, Azizollah Kord, Jake Rezac, Katie Carson, Marla L. Dowell, Elizabeth Eyeson, Ari Feldman, Keith Forsyth, Vu Le, John Marts, Mike McNulty, Kyle Neubarth, Andre Rosete, Matthew Ryan, Maija Teraslina
During the COVID-19 pandemic, NIST began a targeted campaign of measurements of averaged power and occupancy rate in the radio spectrum. The purpose was to sample real environments to offer timely insights into data infrastructure where it might be

A Planar Hyperblack Absolute Radiometer

November 14, 2016
Author(s)
John H. Lehman, Michelle S. Stephens, Malcolm G. White, Andreas Steiger, Christian Monte, Joerg Hollandt, Ivan Ryger, Mathias Kehrt, Marla L. Dowell
The absolute responsivity of a planar radiometer fabricated from micromachined silicon and having carbon nanotubes as the absorber and thermistor was measured in the visible and far infrared (free-field terahertz) wavelength range by means of detector

Laser Welding of Dual-Phase Galvanized Sheet Steel

March 18, 2016
Author(s)
Stephanie L. Miller, Erik A. Pfeif, Andrei F. Kazakov, Esther Baumann, Marla L. Dowell
Laser welding has many advantages over traditional joining methods, but remains underutilized. NIST has undertaken an initiative to improve predictions of weldability, reliability, and performance of laser welds. This study investigates butt welding of

Progress toward Radiation-Pressure-Based Measurement of High-Power Laser Emission - Under Policy Review

October 6, 2014
Author(s)
Paul A. Williams, Joshua A. Hadler, Daniel King, Robert Lee, Frank C. Maring, Gordon A. Shaw, Nathan A. Tomlin, John H. Lehman, Marla L. Dowell
We present an overview of our efforts toward using optical radiation pressure as a means to measure optical power from high-power lasers. Early results with measurements ranging from tens of watts to 92 kW prove the concept, but validation uncertainties

Absolute calibration of optical power and fluence rate for PDT: Report of AAPM TG140

July 23, 2013
Author(s)
Marla L. Dowell, Timothy Zhu, Christopher Bonnerup, Valdir Colussi, Jarod Finlay, Lothar Lilge, Thomas Slowery, claudio sibata
This report is primarily concerned with methods for optical calibration of laser power and light fluence rate for continuous wave (CW) light sources, predominantly used in photodynamic therapy (PDT). Dosimetry of light is very important for PDT, however

Random testing reveals excessive power in commercial laser pointers

May 1, 2013
Author(s)
Joshua A. Hadler, Edna L. Tobares, Marla L. Dowell
In random testing of 122 commercial laser pointers, we observed that 89.7 % of green pointers and 44.4 % of red pointers were not in compliance with the Code of Federal Regulations, producing laser power in excess of the Accessible Emission Limit at one or

Accurate, inexpensive testing of handheld lasers for safe use and operation

March 7, 2013
Author(s)
Marla L. Dowell, Joshua A. Hadler
An accurate, inexpensive test bed for measurements of optical power emitted from handheld lasers is described. Our test bed consists of a thermopile detector, bandpass optical filters, an adjustable iris, and self-centering holders for mounting of the

Laser power meter comparison at far infrared wavelengths and terahertz frequencies

August 1, 2012
Author(s)
John H. Lehman, Marla L. Dowell, Nina P. Basta, Kerry N. Betz, Erich N. Grossman
We have evaluated the responsivity of seven different detectors compared to an electrically calibrated photo-acoustic detector at 119 υm (2.5 THz) and 394 υm (0.76 THz) laser wavelengths. Among the detectors is an electrically calibrated thermopile having

Absolute high-power laser measurements with a flowing water power meter

September 18, 2011
Author(s)
Christopher L. Cromer, Xiaoyu X. Li, John H. Lehman, Marla L. Dowell
We describe a novel flowing water power meter (FWOPM) for high-power laser radiometry in the range of 50 W to 10 kW. The FWOPM has several design features; a rotating mirror oriented at 45° with respect to the incoming radiation, a conical light-trapping

Comparison of absolute measurements of laser power using next generation NIST high power radiometer and Air Force high power calorimeter

June 8, 2011
Author(s)
Marla L. Dowell, Christopher L. Cromer, Xiaoyu X. Li, John Bagford, Dan Seibert, John Eric, David Cooper, Steven Comisford, Ernie Cromwell, Richard Bowling
We report comparisons of laser power measurements between the new NIST radiometer, also known as the BB Prime, and the current Air Force standards, known as the BB calorimeter. [1] These measurements were performed using high power laser sources in the Air

Bilateral comparison of power measurement standards for KrF lasers between PTB and NIST

May 2, 2010
Author(s)
Marla L. Dowell, Christopher L. Cromer, Darryl A. Keenan, Stefan Kuck, Friedhelm Brandt
We report results of the first bilateral laser power comparison for 248-nm KrF excimer lasers accomplished by the National Metrology Institutes of Germany (Physikalisch-Technische Bundesanstalt, PTB) and of the United States of America (National Institute

Reflective attenuators for high energy laser measurements

March 14, 2010
Author(s)
John H. Lehman, David J. Livigni, Christopher L. Cromer, Xiaoyu X. Li, Marla L. Dowell
A high-energy laser attenuator in the range of 250 mJ (20 nsec pulse width, 10 Hz repetition rate, 1064 nm, 1574 nm wavelengths) is described. The optical elements that constitute the attenuator are mirrors with relatively low reflectance, oriented at 45°

Uncertainty calculation for spectral-responsivity measurements

September 1, 2009
Author(s)
John H. Lehman, Chih-Ming Wang, Marla L. Dowell, Joshua A. Hadler
This paper discusses a procedure for measuring the absolute spectral responsivity of optical-fiber power meters and computation of the calibration uncertainty. The procedure reconciles measurement results associated with a monochromator-based measurement

UV pulse response nonlinearity of two Si photodiodes

October 30, 2008
Author(s)
Shao Yang, Darryl A. Keenan, Marla L. Dowell
We measured the pulse response nonlinearity of two silicon photodiodes at 193 and 248 nm with different measurement conditions. We found large and different nonlinearities. We discuss the cause of the nonlinear features.

Choosing the right detector for laser power and energy measurements

October 1, 2008
Author(s)
Marla L. Dowell
You may not realize the importance of good laser metrology and its many pitfalls until you realize how much of today’s commonplace conveniences – from long distance communications to LASIK (laser-assisted in situ keratomileusis) to state-of-the-art cutting

High power laser calibrations at NIST

September 1, 2008
Author(s)
Xiaoyu X. Li, Joshua A. Hadler, Christopher L. Cromer, John H. Lehman, Marla L. Dowell
This document describes the calibration service for the responsivity of laser power meters and detectors used with continuous wave high power lasers at laser wavelengths of 1.06 and 10.6 micrometers. An overview of the calibration procedures, measurement

Reflective attenuator for high energy laser measurements

June 20, 2008
Author(s)
John H. Lehman, David J. Livigni, Xiaoyu X. Li, Christopher L. Cromer, Marla L. Dowell
A high-energy laser attenuator in the range of 250 mJ (20 nsec pulse width, 10 Hz repetition rate, 1064 nm wavelength) is described. The optical elements which constitute the attenuator are mirrors with relatively low reflectance, oriented at 45° angle of

Biophotonic tools in cell and tissue diagnostics

May 1, 2007
Author(s)
Michael Brownstein, Robert A. Hoffman, Richard Levenson, Thomas E. Milner, Marla L. Dowell, Paul A. Williams, Grady S. White, Adolfas Gaigalas, Jeeseong C. Hwang
In order to maintain the rapid advance of biophotonics in the U.S. and to enhance our competitiveness worldwide, key measurement tools must be in place. As a part of a wide-reaching effort to improve the U.S. technology base, the National Institute of

Review of ultraviolet and high power laser measurement standards at NIST

October 25, 2006
Author(s)
John H. Lehman, Christopher L. Cromer, Shao Yang, Marla L. Dowell
High accuracy laser radiometry is on the verge of growth and improvements just as new laser technologies are evolving. Our present tasks are directed toward anticipating and meeting the measurement needs in two areas; higher power and shorter wavelengths

The Next Generation of Laser Radiometry at NIST

February 27, 2006
Author(s)
John H. Lehman, Christopher L. Cromer, Marla L. Dowell
High accuracy laser radiometry is on the verge of significant improvements just as new laser technologies are evolving. Our present tasks are directed toward anticipating and meeting the measurement needs in two areas; higher power and shorter wavelengths