U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications by: John H. Lehman (Fed)

Search Title, Abstract, Conference, Citation, Keyword or Author
Displaying 76 - 100 of 163

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

Optical fiber power meter comparison between NIST and NIM

November 1, 2010
Author(s)
Igor Vayshenker, Jian Li, L. M. Xiong, Z. X. Zhang, 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 National Institute of Metrology (NIM-China). We report optical fiber-based power measurements at nominal wavelengths of

Quartz crystal microbalance for in-situ monitoring of laser cleaning of carbon nanotubes

August 1, 2010
Author(s)
Katie Hurst, Abram Van Der Geest, Mark T. Lusk, Elisabeth Mansfield, John H. Lehman
Photochemical changes of single-walled carbon nanotubes (SWCNTs), graphite and amorphous carbon have been investigated with a quartz crystal microbalance (QCM). The method of in-situ measurements reduces our uncertainty that is attributable to

Method to determine the absorbance of thin films for photovoltaic technology

June 20, 2010
Author(s)
Nathan A. Tomlin, John H. Lehman, Katherine E. Hurst, D. B. Tanner, K. Kamaras, Aron Pekker
We have demonstrated a novel method to determine optical properties of opaque or semi-transparent films for photovoltaic (PV) applications. Such films may be the basis of transparent conductors or photoconductive material. As an example, we measure the

Core-shell composite of SiCN and multiwalled carbon nanotubes from Toluene dispersion

May 21, 2010
Author(s)
John H. Lehman, Katherine E. Hurst, Gurpreet Singh, Elisabeth Mansfield, John D. Perkins, Christopher L. Cromer
Carbon nanotubes are known to have high thermal conductivity, and in bulk form, a topology that could constitute the matrix of an inhomogeneous solid. Among the promised applications of carbon nanotubes is a composite material that is practical for thermal

Excimer laser-based purification of single-walled carbon nanotubes

April 1, 2010
Author(s)
Katie Hurst, Elisabeth Mansfield, Anne Dillon, John H. Lehman
Bulk purified carbon nanotube (CNT) material is essential for the realization of CNT applications including incorporating them into various composite materials. We have developed a laser-based purification technique for bulk single-walled carbon nanotubes

Improving carbon nanotube transparent conductor performance by UV laser irradiation

April 1, 2010
Author(s)
Katie Hurst, Jeffrey Blackburn, Larsen A. Brian, John H. Lehman
We discuss the photochemical treatment of transparent conducting (TC) films made from single-walled carbon nanotubes (SWCNTs).(1) The treatment process is comparable to that described previously, whereby unwanted amorphous carbon is removed from bulk

Multiwalled carbon nanotubes coated with silicon carbonitride (SiCN)

April 1, 2010
Author(s)
Katie Hurst, Christopher L. Cromer, Elisabeth Mansfield, Roop Mahajan, John H. Lehman, Gurpreet Singh
We describe the development of two next-generation optical coatings; amorphous polymer-derived silicon carbonitride (SiCN) particles and a composite consisting of SiCN surrounding a multiwalled carbon nanotube (MWCNT) core. Laser-induced damage testing of

Reflective attenuators for high energy laser measurements

March 14, 2010
Author(s)
John H. Lehman, David J. Livigni, Christopher L. Cromer, Xiaoyu X. Li, Marla L. Dowell
A high-energy laser attenuator in the range of 250 mJ (20 nsec pulse width, 10 Hz repetition rate, 1064 nm, 1574 nm wavelengths) is described. The optical elements that constitute the attenuator are mirrors with relatively low reflectance, oriented at 45°

Uncertainty calculation for spectral-responsivity measurements

September 1, 2009
Author(s)
John H. Lehman, Chih-Ming Wang, Marla L. Dowell, Joshua A. Hadler
This paper discusses a procedure for measuring the absolute spectral responsivity of optical-fiber power meters and computation of the calibration uncertainty. The procedure reconciles measurement results associated with a monochromator-based measurement

International comparisons of optical fiber power measurements

October 1, 2008
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 1302 and 1546 nm made by NIST and six national measurement institutes (NMIs). We also describe transfer standards and the associated uncertainties. The comparisons show a reasonably
Was this page helpful?