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Search Publications by: Paul A. Williams (Fed)

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Displaying 26 - 50 of 119

Micromachined force balance for optical power measurement by radiation pressure sensing

August 6, 2018
Author(s)
Ivan Ryger, Alexandra B. Artusio-Glimpse, Paul A. Williams, Nathan A. Tomlin, Michelle S. Stephens, Matthew T. Spidell, Kyle A. Rogers, John H. Lehman
We introduce a micromachined force scale for laser power measurement by means of radiation pressure sensing. With this technique, the measured laser light is not absorbed and can be utilized while being measured. We employ silicon micromachining technology

Point-of-Use, Nonexclusive, High-Power Laser Power Meter

June 19, 2018
Author(s)
Aly Artusio-Glimpse, Ivan Ryger, Paul A. Williams, John H. Lehman
We have developed a small-package, high-power laser power meter that directly measures radiation pressure on a high-reflectivity mirror for nonexclusive, in situ laser measurements without pick- off schemes. Furthermore, our non-inertial design inhibits

Correlation of Neutron-Based Strain Imaging and Mechanical Behavior of Armor Steel Welds Produced with the Hybrid Laser Arc Welding Process

June 11, 2018
Author(s)
Jeffrey W. Sowards, Daniel S. Hussey, David L. Jacobson, Stan Ream, Paul A. Williams
Bragg edge neutron transmission imaging was used to characterize the spatial distribution of thermally induced residual strains in a steel armor plate welded with a hybrid laser arc process. This residual strain distribution was compared to the spatial

Optical Measurements of Dynamic Absorptance during High-power Laser Spot Welding

May 7, 2018
Author(s)
Brian Simonds, Jeffrey W. Sowards, Joshua A. Hadler, Boris Wilthan, Erik A. Pfeif, Jack R. Tanner, Chandler Harris, Paul A. Williams, John Lehman
We present precision measurements of the time-dependent absorptance during a 10 ms fiber-laser spot weld on 316L stainless steel. From these, the precise time and energy at which a keyhole is formed can be determined.

Geometric contributions to chopper wheel optical attenuation uncertainty

December 9, 2017
Author(s)
Matthew T. Spidell, Joshua A. Hadler, Michelle S. Stephens, John H. Lehman, Paul A. Williams
Calibrated reflective optical choppers are used in NIST’s high power laser calibration services due to their advantages in performance and safety over wedges and semi-transparent materials for beam power reduction. While the design, operation, and

On-site multi-kilowatt laser power meter calibration using radiation pressure

December 1, 2017
Author(s)
Paul A. Williams, Joshua A. Hadler, Brian J. Simonds, John H. Lehman
We have demonstrated the calibration of a thermal power meter against a radiation-pressure power meter in the range of 20 kW in a manufacturing test environment. The results were compared to a traditional calorimeter-based laboratory calibration undertaken

Prototype Tests of a Miniature Radiation Pressure Sensor

July 2, 2017
Author(s)
Alexandra B. Artusio-Glimpse, Paul A. Williams, Nathan A. Tomlin, Ivan Ryger, Michelle S. Stephens, John H. Lehman
Using reflection, radiation pressure (RP) sensors provide a means for in-situ power measurement simply and accurately. The first realization of multi-kW RP power meters (RPPM) established a new paradigm of optical power measurement technology [1]. Our

Silicon Micromachined Capacitive Force Scale: The Way to Improved Radiation Pressure Sensing

July 2, 2017
Author(s)
Ivan Ryger, Paul A. Williams, Nathan A. Tomlin, Alexandra B. Artusio-Glimpse, Michelle S. Stephens, Matthew T. Spidell, John H. Lehman
Measurement of high optical power using radiation pressure sensing [1] is attractive for its non-absorbing power measurment allowing compact sensor dimensions, faster response times and negligible optical power dissipation compared to standard thermal

Portable high-accuracy non-absorbing laser power measurement at kilowatt levels by means of radiation pressure

February 16, 2016
Author(s)
Paul A. Williams, Joshua A. Hadler, Frank C. Maring, Robert Lee, Kyle A. Rogers, Brian J. Simonds, Matthew T. Spidell, Ari D. Feldman, John H. Lehman
We describe a unique optical power meter which measures the radiation pressure to accurately determine a laser’s optical power output. This approach traces its calibration of the optical Watt to the kilogram. Our power meter is designed for high-accuracy

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

Use of radiation pressure for measurement of high-power laser emission

October 15, 2013
Author(s)
Paul A. Williams, Joshua A. Hadler, Robert Lee, Frank Maring, John H. Lehman
We demonstrate a paradigm in absolute laser radiometry where a laser beam's power can be measured from its radiation pressure. Using an off-the-shelf high-accuracy mass scale and a 500 W Yb-doped fiber laser and a 92 kW CO2 laser, we show preliminary

Absolute spectroscopy of N2O near 4.5 um with a comb-calibrated, frequency-swept quantum cascade laser spectrometer

January 14, 2013
Author(s)
Kevin O. Knabe, Paul A. Williams, Fabrizio R. Giorgetta, Michael Radunsky, Chris Armacost, Sam Crivello, Nathan R. Newbury
We present absolute line center frequencies for 24 fundamental nu-3 ro-vibrational P-branch transitions near 4.5 um in N2O with an absolute frequency uncertainty of 800 kHz. The spectra were acquired with a swept laser spectrometer consisting of an

Frequency characterization of a swept and fixed-wavelength external-cavity quantum cascade laser by use of a frequency comb

May 21, 2012
Author(s)
Kevin O. Knabe, Paul A. Williams, Fabrizio R. Giorgetta, Chris Armacost, Michael Radunsky, Nathan R. Newbury
The instantaneous optical frequency of an external-cavity quantum cascade laser (QCL) is characterized by comparison to a near-infrared frequency comb. Fluctuations in the instantaneous optical frequency are analyzed to determine the frequency noise power

Comb-assisted swept laser spectroscopy with a mode-hop free tunable external cavity QCL

May 1, 2012
Author(s)
Kevin O. Knabe, Fabrizio R. Giorgetta, Nathan R. Newbury, Chris Armacost, Michael Radunsky, Sam Crivello, Timothy Day, Paul A. Williams
We demonstrate sub-MHz spectral resolution of N 2O absorption spectra acquired with a swept external-cavity quantum cascade laser (QCL) over 0.87 THz. The QCL frequency is monitored by sum -frequency generation with an optical fiber frequency comb.

Broad bandwidth trace gas and standoff detection with infrared frequency comb sources

March 11, 2012
Author(s)
Nathan R. Newbury, Alexander M. Zolot, Esther Baumann, Fabrizio R. Giorgetta, Florian B. Adler, Ian R. Coddington, Kevin O. Knabe, Lora L. Nugent-Glandorf, Paul A. Williams, Scott A. Diddams, Tyler W. Neely
An optical frequency comb based on the output of a mode-locked femtosecond laser can be used in spectroscopic studies and sensing applications. The broad array of frequency modes simultaneously provides high spectral resolution and broad wavelength