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Search Publications by: John H. Lehman (Fed)

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Displaying 26 - 50 of 311

Simplified kilogram traceability for photon momentum radiometers

October 1, 2020
Author(s)
Kyle A. Rogers, Paul A. Williams, Gordon A. Shaw, John H. Lehman
High power laser applications in areas such as laser processing of materials can require an accurately measured laser power. Radiation pressure-based laser power measurement has been proven as a practical method for quantifying these high-power levels in

Calibration of free-space and fiber-coupled single-photon detectors

September 14, 2020
Author(s)
Thomas Gerrits, Alan L. Migdall, Joshua C. Bienfang, John H. Lehman, Sae Woo Nam, Oliver T. Slattery, Jolene D. Splett, Igor Vayshenker, Chih-Ming Wang
We present our measurements of the detection efficiency of free-space and fiber-coupled single- photon detectors at wavelengths near 851 nm and 1533.6 nm. We investigate the spatial uniformity of one free-space-coupled silicon single-photon avalanche diode

Radiation Pressure Laser Power Meter for Industrial Laser Machining

September 10, 2020
Author(s)
Aly Artusio-Glimpse, Ivan Ryger, Natalia A. Azarova, Paul A. Williams, John H. Lehman
Demonstration and validation of a linear radiation pressure-based high-power laser power meter is presented. To date, this device is the most promising real-time, absolute power meter for laser material processing where power monitoring is crucial.

HALO - High Amplification Laser-pressure Optic

June 21, 2020
Author(s)
Alexandra B. Artusio-Glimpse, Kyle A. Rogers, Paul A. Williams, John H. Lehman
Efforts are underway at the National Institute of Standards and Technology to drastically reduce the uncertainty of laser power measurements using radiation pressure. The High Amplification Laser-pressure Optic (HALO) system is a cornerstone of this effort

Microfabricated bolometer based on a vertically aligned carbon nanotube absorber

March 2, 2020
Author(s)
Anna K. Vaskuri, Michelle S. Stephens, Nathan A. Tomlin, Christopher S. Yung, Andrew J. Walowitz, Cameron Straatsma, Dave Harber, John H. Lehman
We have designed a microfabricated planar absolute radiometer based on a vertically aligned carbon nanotube (VACNT) absorber and an electrical power substitution method. The radiometer is designed to operate at room temperature and to be capable of

Calibration of free-space and fiber-coupled single-photon detectors

December 20, 2019
Author(s)
Thomas Gerrits, Alan L. Migdall, Joshua C. Bienfang, John H. Lehman, Sae Woo Nam, Jolene D. Splett, Igor Vayshenker, Chih-Ming Wang
We measure the detection efficiency of single-photon detectors at wavelengths near 851 nm and 1533.6 nm. We investigate the spatial uniformity of one free-space-coupled single-photon avalanche diode and present a comparison between fusion-spliced and

Optical-Fiber Power Meter Comparison between NIST and LAMETRO

November 1, 2019
Author(s)
Johnny Jimenez, Maria Ugalde, John H. Lehman, Igor Vayshenker
We describe the results of a comparison of reference standards between the National Institute of Standards and Technology (NIST-USA) and Laboratorio de Metrologia, Instituto Costarricense de Electricidad (LAMETRO-ICE, COSTA RICA) for optical fiber-based

Compact total irradiance monitor: Flight demonstration

August 30, 2019
Author(s)
Dave Harber, John H. Lehman, Nathan A. Tomlin, Christopher Yung, Malcolm White, Zach Castleman, Ginger Drake, Samuel Van Dreser, Nat Farber, Karl Heurman, Joel Rutkowski, Alan Sims, Jacob Sprunck, Cameron Straatsma, Isaac Wanamaker, Wengang Zheng, Greg Kopp, P. Pilewskie, Michelle Stephens
The long-term balance between Earth's absorption of solar energy and emission of radiation to space is a fundamental climate measurement. Total solar irradiance (TSI) has been measured from space, uninterrupted, for the past 40 years via a series of

BABAR: Black Array of Broadband Absolute Radiometers for far infrared sensing

May 13, 2019
Author(s)
Christopher S. Yung, Nathan A. Tomlin, Cameron Straatsma, Joel Rutkowski, Erik Richard, Dave Harber, John H. Lehman, Michelle S. Stephens
Currently at NIST, there is an effort to develop a black array of broadband absolute radiometers (BABAR) for far infrared sensing. The linear array of radiometer elements is based on uncooled vanadium oxide (VOx) microbolometer pixel technology but with

Inline Laser Power Measurement by Photon Momentum

February 6, 2019
Author(s)
John H. Lehman, Paul A. Williams, Daniel W. Rahn, Kyle A. Rogers
We present a measurement scheme and instrumentation for quantifying laser power by means of photon momentum. The optical design is optimized such that the incoming laser beam is minimally perturbed and is available for other purposes along the incoming

Radiation-Pressure Enabled Traceable Laser Sources at High CW Powers

January 4, 2019
Author(s)
Paul A. Williams, Alexandra B. Artusio-Glimpse, Joshua A. Hadler, Daniel King, Ivan Ryger, Tam Vo, John H. Lehman, Kyle A. Rogers
Radiation pressure has recently been shown to have practical application for multi-kilowatt CW laser power measurement. One key advantage lies in its ability to measure without absorbing the laser beam. This enables a new measurement paradigm where laser

Time-Resolved Absorptance and Melt Pool Dynamics during Intense Laser Irradiation of a Metal

October 25, 2018
Author(s)
Brian J. Simonds, Jeffrey W. Sowards, Joshua A. Hadler, Erik A. Pfeif, Boris Wilthan, Jack R. Tanner, Paul A. Williams, John H. Lehman
Laser welding is a complex, dynamic process by which focused, high-intensity laser light is used to join two metallic surfaces and is being increasing deployed in a variety of industrial applications. Determining the time-dependent absorptance of the laser