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Search Publications by: John H. Lehman (Fed)

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Displaying 51 - 75 of 153

Atomic Clock with 1x10 -18 Room-Temperature Blackbody Stark Uncertainty

December 31, 2014
Author(s)
Kyle P. Beloy, Nathan M. Hinkley, Nate B. Phillips, Jeffrey A. Sherman, Marco Schioppo, John H. Lehman, Ari D. Feldman, Leonard M. Hanssen, Christopher W. Oates, Andrew D. Ludlow
The Stark shift due to blackbody radiation (BBR) is a key factor limiting the performance of many atomic frequency standards, with the BBR environment inside the clock apparatus being difficult to characterize at a high level of precision. Here we

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

A CW calibrated laser pulse energy meter for the range 1 pJ to 100mJ

May 13, 2014
Author(s)
Malcolm G. White, Rodney W. Leonhardt, David J. Livigni, John H. Lehman
We describe the use of a silicon photodiode trap detector and digital storage oscilloscope as an absolute laser pulse energy meter, capable of repetition rates of 85 Hz and 5% uncertainty (k = 2). The maximum repetition rate is limited by the decay time of

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

Optical-Fiber Power Meter Comparison between NIST and KRISS

December 21, 2012
Author(s)
Seungkwan Kim, Keesuk Hong, Dong-Hoon Lee, David J. Livigni, Xiaoyu X. Li, John H. Lehman
We describe the results of a comparison of reference standards between the National Institute of Standards and Technology (NIST-USA) and Korea Research Institute of Standards and Science (KRISS- R.O. Korea). We report optical fiber-based power measurements

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

Towards a fiber-coupled picowatt cryogenic radiometer

June 11, 2012
Author(s)
Nathan A. Tomlin, John H. Lehman, Sae Woo Nam
A picowatt cryogenic radiometer (PCR) has been fabricated at the microscale level for electrical substitution optical fiber power measurements. The absorber, electrical heater, and thermometer are all on a micromachined membrane less than 1mm on a side

Optical fiber-coupled cryogenic radiometer with carbon nanotube absorber

April 1, 2012
Author(s)
David J. Livigni, Nathan A. Tomlin, Christopher L. Cromer, John H. Lehman
A cryogenic radiometer was constructed for direct-substitution optical fiber power measurements. The cavity is intended to operate at the 3 K temperature stage of a dilution refrigerator or 4.2 K stage of a liquid cryostat. The optical fiber is removable

Optical fibre-coupled cryogenic radiometer with carbon nanotube absorber

March 2, 2012
Author(s)
David J. Livigni, Nathan A. Tomlin, Christopher L. Cromer, John H. Lehman
A cryogenic radiometer was constructed for direct-substitution optical-fibre power measurements. The cavity is intended to operate at the 3 K temperature stage of a dilution refrigerator or 4.2 K stage of a liquid cryostat. The optical fibre is removable

Carbon nanotube arrays for absolute IR and THz radiometry

October 2, 2011
Author(s)
John H. Lehman, Kerry N. Betz, Erich N. Grossman
We have assembled and evaluated a novel electrically calibrated thermopile having an array of 1.5 mm long multiwalled carbon nanotubes as the radiation absorber. We find very low reflectance at the 390 υm laser wavelength and excellent agreement between

Fully lithographic fiber-coupled cryogenic radiometer for picowatt powers

September 19, 2011
Author(s)
Nathan A. Tomlin, John H. Lehman, Sae Woo Nam
A new type of absolute cryogenic radiometer has been fabricated at the microscale level for direct substitution optical fiber power measurements. It consists of three parts: an absorber, electrical heater, and thermometer all on a single micro-machined

International comparisons of optical fiber power measurements

September 19, 2011
Author(s)
Igor Vayshenker, David J. Livigni, Xiaoyu X. Li, John H. Lehman
We discuss the results of optical fiber power meter (OFPM) measurements at 1310 and 1550 nm made by NIST and seven national measurement institutes (NMIs). We also describe transfer standards and the associated uncertainties. The comparisons show a

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

Evaluating the characteristics of multiwall carbon nanotubes

July 1, 2011
Author(s)
John H. Lehman, M. Terrones, Elisabeth Mansfield, Katie Hurst, Vincent Muenier
During the past 20 years, multiwall carbon nanotubes (MWCNTs) have become an important industrial material. Hundreds of tons are produced each year. This review is a survey of the scientific literature, motivated by industrial requirements and guidelines