Featured Research

from universities, journals, and other organizations

Arrays of long nanotubes may help measure terahertz laser power

Date:
July 25, 2011
Source:
National Institute of Standards and Technology (NIST)
Summary:
Terahertz radiation can penetrate numerous materials -- plastic, clothing, paper and some biological tissues -- making it an attractive candidate for applications such as concealed weapons detection, package inspection and imaging skin tumors. There is now no standard method for measuring the absolute output power of terahertz lasers, but researchers have found that dense arrays of extra-long carbon nanotubes are promising coatings for prototype terahertz laser power detectors.

"Cupcakes" of vertically aligned carbon nanotube arrays (VANTAs) grown on silicon, which appears blue in the photo. A chunk of VANTA can be sliced from the silicon with a razor blade and, using the blade as a spatula, easily moved to the top of a laser power detector. The very dark nanotube coating absorbs terahertz laser light.
Credit: Lehman/NIST

Terahertz radiation can penetrate numerous materials -- plastic, clothing, paper and some biological tissues -- making it an attractive candidate for applications such as concealed weapons detection, package inspection and imaging skin tumors. However, to date there is no standard method for measuring the absolute output power of terahertz lasers, one source of this type of radiation. Now, researchers at the National Institute of Standards and Technology (NIST) have found that dense arrays of extra-long carbon nanotubes absorb nearly all light of long wavelengths, and thus are promising coatings for prototype detectors intended to measure terahertz laser power.

The research is part of NIST's effort to develop the first reference standards for calibrating lasers that operate in the terahertz range, from the far infrared at wavelengths of 100 micrometers to the edge of the microwave band at 1 millimeter.

"There is no measurement traceability for absolute power for terahertz laser sources," NIST project leader John Lehman says. "We have customers asking for the calibrations. This coating looks viable for terahertz laser power detectors."

The coating, called a VANTA (vertically aligned carbon nanotube array), has several desirable properties. Most obviously, it is easy to handle. The nanotubes are tens of micrometers to over a millimeter long, so a dense layer is visible without a microscope. A chunk of VANTA can be cut, lifted, and carried like a piece of cake, making it easy to transfer from a silicon surface where the tubes are grown to a laser power detector.

Most importantly, the coating is very dark. The NIST team evaluated three VANTA samples with average lengths of 40 and 150 micrometers and 1.5 millimeters (mm) and found that longer tubes reflect less light. The 1.5 mm version reflects almost no light -- just 1 percent at a wavelength of 394 micrometers. This result, the first-ever evaluation of a VANTA's reflectance at that terahertz wavelength, indicates that virtually all arriving laser light is absorbed, which would enable highly accurate measurements of laser power.

The 1.5 mm VANTA absorbs more light than comparable coatings such as gold black, but more work is needed to calculate uncertainties and determine effects of factors such as light angle. The project extends NIST's long history in laser power measurements and Lehman's recent advances in ultradark nanotube coatings.

VANTAs also have desirable thermal properties. NIST researchers found that the material absorbs and releases heat quickly compared to other black coatings, which will make the detectors more responsive and quicker to produce signals. Otherwise, a coating thick enough to absorb long wavelengths of light would not efficiently transmit heat to the detector.

In developing the capability for terahertz laser radiometry, NIST is building a terahertz laser designed for routine measurements and a detector called a thermopile to measure the laser's power. This simple detector design produces a voltage when heat is applied to a junction of two dissimilar metals. NIST researchers used the VANTA to coat a prototype thermopile. Further research is planned to design detectors that might be used as reference standards.


Story Source:

The above story is based on materials provided by National Institute of Standards and Technology (NIST). Note: Materials may be edited for content and length.


Journal Reference:

  1. John H. Lehman, Bob Lee, Erich N. Grossman. Far infrared thermal detectors for laser radiometry using a carbon nanotube array. Applied Optics, 2011; 50 (21): 4099 DOI: 10.1364/AO.50.004099

Cite This Page:

National Institute of Standards and Technology (NIST). "Arrays of long nanotubes may help measure terahertz laser power." ScienceDaily. ScienceDaily, 25 July 2011. <www.sciencedaily.com/releases/2011/07/110719171551.htm>.
National Institute of Standards and Technology (NIST). (2011, July 25). Arrays of long nanotubes may help measure terahertz laser power. ScienceDaily. Retrieved October 23, 2014 from www.sciencedaily.com/releases/2011/07/110719171551.htm
National Institute of Standards and Technology (NIST). "Arrays of long nanotubes may help measure terahertz laser power." ScienceDaily. www.sciencedaily.com/releases/2011/07/110719171551.htm (accessed October 23, 2014).

Share This



More Matter & Energy News

Thursday, October 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

3D Printed Instruments Make Sweet Music in Sweden

3D Printed Instruments Make Sweet Music in Sweden

Reuters - Innovations Video Online (Oct. 23, 2014) — Students from Lund University's Malmo Academy of Music are believed to be the world's first band to all use 3D printed instruments. The guitar, bass guitar, keyboard and drums were built by Olaf Diegel, professor of product development, who says 3D printing allows musicians to design an instrument to their exact specifications. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Chameleon Camouflage to Give Tanks Cloaking Capabilities

Chameleon Camouflage to Give Tanks Cloaking Capabilities

Reuters - Innovations Video Online (Oct. 22, 2014) — Inspired by the way a chameleon changes its colour to disguise itself; scientists in Poland want to replace traditional camouflage paint with thousands of electrochromic plates that will continuously change colour to blend with its surroundings. The first PL-01 concept tank prototype will be tested within a few years, with scientists predicting that a similar technology could even be woven into the fabric of a soldiers' clothing making them virtually invisible to the naked eye. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Jet Sales Lift Boeing Profit 18 Pct.

Jet Sales Lift Boeing Profit 18 Pct.

Reuters - Business Video Online (Oct. 22, 2014) — Strong jet demand has pushed Boeing to raise its profit forecast for the third time, but analysts were disappointed by its small cash flow. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Internet of Things Aims to Smarten Your Life

Internet of Things Aims to Smarten Your Life

AP (Oct. 22, 2014) — As more and more Bluetooth-enabled devices are reaching consumers, developers are busy connecting them together as part of the Internet of Things. (Oct. 22) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins