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Search Publications by: John H. Lehman (Fed)

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Displaying 101 - 125 of 163

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

Inverted spectra of single-wall carbon nanotube films

July 10, 2008
Author(s)
John H. Lehman, Katie Hurst, Lara Roberson, K. Nield, J. D. Hamlin
We present absolute measurements of reflectance and absorbance for a purified single wall carbon nanotube (SWCNT) film. The absorbance spectrum of a SWCNT-laminated pyroelectric detector for wavelengths 0.6 - 2 υm is inverted when compared to absorbance

Bilateral optical power meter comparison between NIST and CENAM

July 1, 2008
Author(s)
Igor Vayshenker, J. Bermudez, J. Molina, Z. Ruiz, 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 Centro Nacional De Metrologia (CENAM-Mexico). Open beam (free field) and optical-fiber-based measurements at

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

High-performance carbon nanotube coatings for high-power laser radiometry

January 3, 2008
Author(s)
Krishna Ramadurai, Christopher L. Cromer, Laurence A. Lewis, Katie Hurst, Anne Dillon, Roop Mahajan, John H. Lehman
Radiometry for the next generation of high-efficiency, high-power industrial lasers requires thermal management at optical power levels exceeding 10 kW. Laser damage and thermal transport present fundamental challenges for laser radiometry in support of

Foam-based optical absorber for high-power laser radiometry

December 1, 2007
Author(s)
Krishna Ramadurai, Christopher L. Cromer, Xiaoyu X. Li, Roop Mahajan, John H. Lehman
We report damage threshold measurement results for novel absorbers comprised of either liquid-cooled silicon carbide or vitreous carbon foams. The measurements demonstrate damage thresholds up to 1.6×10^+4 W/cm 2 at an incident circular spot size of 2 mm

Photoconductive lifetimes of carbon nanotubes films

November 29, 2007
Author(s)
Katie Hurst, Richard K. Ahrenkiel, Steve W. Johnston, Anne Dillon, Lara Roberson, John H. Lehman
The photoconductive recombination lifetimes of carbon nanotube (CNT) thin films as a function of wavelength are measured by resonant-coupled photoconductive decay (RCPCD) method (1). The carrier recombination lifetime is a fundamental property of carbon

NIST optical fiber power measurements: intramural and international comparisons

October 1, 2007
Author(s)
Igor Vayshenker, John H. Lehman, David J. Livigni, Joshua A. Hadler
We discuss the results of intramural comparisons of NIST laser and optical fiber power meter (OFPM) measurements, and the results of OFPM comparisons between NIST and three National Measurement Institutes (NMIs). We also describe transfer standards

NIST Measurement Services: cw Laser Power and Energy Calibrations at NIST

July 1, 2007
Author(s)
Joshua A. Hadler, Christopher L. Cromer, John H. Lehman
This document describes a calibration service for absolute laser power and energy measurements of laser power meters and detectors used with continuous wave lasers at laser wavelengths between 325 and 1550 nm. In addition to a summary of the calibration

Multiwall carbon nanotube absorber on a thin-film pyroelectric detector

April 1, 2007
Author(s)
John H. Lehman, Katie Hurst, Anne Dillon, A. M. Radojevic, R M. Osgood
Multiwall carbon nanotubes (MWNTs) were applied in a bulk layer to a pyroelectric film to increase the detector sensitivity nearly fourfold without a substantial penalty to the low-frequency response (4 to 100 Hz). In addition, the spectral sensitivity

Trilateral optical powermeter comparison between NIST, NMIJ/AIST, and METAS

February 10, 2007
Author(s)
Igor Vayshenker, John H. Lehman, David J. Livigni, Xiaoyu X. Li, Kuniaki Amemiya, Daiji Fukuda, Seiji Mukai, Shinji Kimura, Michiyuki Endo, Jacques Morel, Armin Gambon
We describe the results of a comparison of reference standards between three National Metrology Institutes: the National Institute of Standards and Technology (NIST, USA), the National Metrology Institute of Japan/National Institute of Advanced Industrial

Cleaning of carbon nanotubes near the p-plasmon resonance

November 7, 2006
Author(s)
Katie Hurst, Darryl A. Keenan, John H. Lehman, Anne Dillon
The cleaning of bulk carbon single-walled nanotubes (SWNTs) by use of a 248 nm excimer laser is verified with imaging, and quantitative evaluation of morphology and composition. A 5% change in responsivity of a pyroelectric detector coated with SWNTs is

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

Carbon Based Coatings for Thermal Detectors: Laser Damage and Thermal Efficiency

September 25, 2006
Author(s)
Krishna Ramadurai, Laura H. Lewis, Christopher L. Cromer, Roop Mahajan, Katie Hurst, John H. Lehman
The laser damage threshold and absorption efficiency of a variety of carbon based thermal coatings for laser power and energy measurements have been investigated. Carbon based paint, carbon fibers as well as single wall carbon nanotubes (SWCNTs) and

Damage of thermal detector platforms based on metal-carbon nanotube composites

September 25, 2006
Author(s)
Laurence Lewis, Christopher L. Cromer, Krishna Ramadurai, Roop Mahajan, John H. Lehman
Today's standards for laser power and energy measurements are inadequate for tomorrow's high efficiency diode and fiber lasers. To meet this need, a new generation of thermal detector platforms based on carbon nanotubes (CNTs) and metal is being developed

Excimer Laser Treatment of Carbon Nanotubes

May 1, 2006
Author(s)
Katie Hurst, Darryl A. Keenan, Anne Dillon, Thomas Gennett, Paul Rice, John H. Lehman
Raman spectroscopy and spectral responsivity measurements are performed to investigate the alteration of sample purity and morphology, caused by varying pulse parameters for laser treatment of bulk carbon nanotubes using a 248 nm excimer-laser.
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