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Search Publications by: John H. Lehman (Fed)

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Displaying 126 - 150 of 163

Hot-wire chemical vapor synthesis for a variety of nano-materials with novel aplications

April 20, 2006
Author(s)
Anne Dillon, A. H. Mahan, Rohit Deshpande, J. L. Alleman, Jeffrey Blackburn, P. A. Parillia, M. J. Heben, Chaiwat Engtrakul, K.E.H. Gilbert, Kevin M. Jones, Bobby To, S Lee, John H. Lehman
Hot-wire chemical vapor deposition (HWCVD) has been demonstrated as a simple economically scalable technique for the synthesis of a variety of nano-materials in an environmentally friendly manner. For example we have employed HWCVD for the continuous

Toward rapid and inexpensive identification of bulk carbon nanotubes

April 6, 2006
Author(s)
Katie Hurst, Anne Dillon, Jeffrey Blackburn, John H. Lehman
The volume fraction of metallic and semiconducting carbon single-wall nanotubes (SWNTs)hasbeen estimated for purified laser vaporization SWNTs, from an effective medium approximation and the measured spectral responsivity of a LiTaO 3 pyroelectric detector

Improved Thermal Detector Coatings for Laser Radiometry at NIST

February 27, 2006
Author(s)
John H. Lehman
Nearly all of the radiometric standards for laser power and energy measurements at NIST and elsewhere in the world are based on thermal detectors. These detectors usually rely on a thermal absorber coating to enhance the detector responsivity. Ideally the

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

Characterization of Carbon Nanotube Purity Using a Quartz Sensor Platform

November 28, 2005
Author(s)
Stephanie A. Hooker, Ryan Schilt, Natalia Varaksa, John H. Lehman, Paul Rice
Carbon nanotubes are revolutionary materials, with properties that are vastly different than any other bulk form of carbon. Their unique combination of electrical, mechanical, and thermal properties makes them attractive for applications in advanced

Carbon nanotube coated thermal detectors

November 14, 2005
Author(s)
John H. Lehman
Nearly all of the radiometric standards for laser power and energy measurements at NIST and elsewhere in the world are based on thermal detectors. These detectors usually rely on a thermal absorber coating to enhance the detector responsivity. Ideally the

Dielectric function of carbon nanotube coated thermal detectors

November 14, 2005
Author(s)
John H. Lehman
The absolute responsivity of a thermal detector depends on its absorption efficiency as a function of wavelength. We present experiments and document the results for carbon nanotube (CNT) based coatings for thermal detectors. The results indicate that the

Ultraviolet Laser Damage of Carbon Nanotube Coatings on Thermal Detector Platforms

November 14, 2005
Author(s)
Darryl A. Keenan, Natalia Varaksa, Anne Dillon, Chaiwat Engtrakul, Stephen E. Russek, John H. Lehman
We have initiated a program to demonstrate the next generation of optical detector coatings using carbon nanotubes (CNTs). These coatings have been used on a variety of detector platforms for laser power and energy measurement standards. These coatings

Application of carbon nanotube coatings for laser measurements

October 17, 2005
Author(s)
John H. Lehman, Paul Rice, Natalia Varaksa, Chaiwat Engtrakul, Anne Dillon
We have demonstrated coatings based on carbon nanotubes (CNTs) on a variety of detector platforms for laser power and energy measurement standards. These coatings must be resistant to damage and aging while maintaining desirable optical and thermal

Carbon Nanotube-Based Coatings for Laser Power and Energy Measurements

October 1, 2005
Author(s)
John H. Lehman, Natalia Varaksa, Evangelos Theocharous, Anne Dillon
We describe carbon nanotube (CNT) based coatings for thermal detectors for laser power and energy measurements. The value of thermal properties of CNTs obtained from the literature indicates that such coatings have desirable properties such as low thermal

Thin-film coatings: Carbon nanotube coatings promise better thermal detectors

July 1, 2005
Author(s)
John H. Lehman, Anne Dillon
With high thermal conductivity and resistance to damage, carbon nanotube coatings are a promising new technology for thermal detectors. NIST and NREL scientists are exploring this viable alternative with the aim of developing better radiometric standards

Single-wall Carbon Nanotube Coating on a Pyroelectric Detector

February 1, 2005
Author(s)
John H. Lehman, Chaiwat Engtrakul, Thomas Gennett, Anne Dillon
Carbon single-wall nanotubes (SWNTs) are studied as the thermal-absorption coating on a large area pyroelectric detector. The SWNTs were produced by a laser vaporization method and dispersed onto the detector surface by use of a simple airbrush technique

Carbon multi-walled nanotubes grown by HWCVD on a pyroelectric detector

January 21, 2005
Author(s)
John H. Lehman, Rohit Deshpande, Paul Rice, Bobby To, Anne Dillon
Carbon multi-wall nanotubes (MWNTs) were grown on a lithium niobate (LiNbO3) pyroelectric detector with a nickel film as the catalyst by hot-wire chemical vapor deposition (HWCVD). Two detectors are documented, each with slightly different deposition

Intramural comparison of NIST laser and optical fiber power calibrations

March 1, 2004
Author(s)
John H. Lehman, Igor Vayshenker, David J. Livigni, Joshua A. Hadler
The responsivity of two optical detectors was determined by the method of direct substitution in four different NIST measurement facilities. The measurements were intended to demonstrate the determination of absolute responsivity as provided by NIST

Optical-Fiber Power Meter Comparison between NIST and PTB

October 1, 2003
Author(s)
Igor Vayshenker, Holger Haars, Xiaoyu X. Li, John H. Lehman, David J. Livigni
We describe the results of a comparison of reference standards between the National Institute of Standards and Technology (NIST-USA) and Physikalisch-Technische Bundesanstalt (PTB-Germany) at nominal wavelengths of 1300 and 1550 nm using an optical-fiber

Gold-Black Coatings for Freestanding Pyroelectric Detectors

May 23, 2003
Author(s)
John H. Lehman, Evangelos Theocharous, George P. Eppeldauer, Chris Pannell
We describe the process of depositing gold-black on thin, freestanding pyroelectric detector substrates and compare this with previous work documented in the literature. We have evaluated gold-black coatings on thin, freestanding pyroelectric detector

Domain-engineered ferroelectric-pyroelectric detectors for laser metrology

May 1, 2002
Author(s)
John H. Lehman, Harald Gnewuch, Chris Pannell
Ferroelectric pyroelectric detectors are presently used for high accuracy laser metrology. We investigate ways to exploit domain-engineered ferroelectric material such as lithium tantalate to make improved detectors, while understanding changes in the

Domain-Engineered Thin-Film LiNbO 3 Pyroelectric-Bicell Optical Detector

August 1, 2001
Author(s)
John H. Lehman, A. M. Radojevic, R M. Osgood
We have fabricated a bicell detector consisting of a single freestanding 10 um thick film of single-crystal lithium niobate (LiNbO3), having two adjacent domains of opposite spontaneous polarization, and hence two adjacent pyroelectric detector regions of
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