Featured Research

from universities, journals, and other organizations

Researchers realize high-power, narrowband terahertz source at room temperature

Date:
September 30, 2011
Source:
Northwestern University
Summary:
Researchers have developed a simpler way to generate single-chip terahertz radiation, a discovery that could soon allow for more rapid security screening, border protection, high sensitivity biological/chemical analysis, agricultural inspection, and astronomical applications.

Researchers at Northwestern University have developed a simpler way to generate single-chip terahertz radiation, a discovery that could soon allow for more rapid security screening, border protection, high sensitivity biological/chemical analysis, agricultural inspection, and astronomical applications.

The work, headed by Manijeh Razeghi, Walter P. Murphy Professor of Electrical Engineering and Computer Science in the McCormick School of Engineering and Applied Science, was recently published in the journal Applied Physics Letters and was presented in August at the SPIE Optics + Photonics conference in San Diego.

Terahertz radiation (wavelength range of 30 -- 300 microns) can be used to see through paper, clothing, cardboard, plastic, and many other materials, without any of the health risks posed by current x-ray based techniques. This property has become extremely valuable for security screening, as it is safe to use on people and can detect metals and ceramics that might be used as weapons.

In addition, a scanning terahertz source can identify many types of biological or chemical compounds due to their characteristic absorption spectra in this wavelength range. Sensitivity to water content can also be utilized to study agricultural quality. Finally, through mixing with a compact coherent terahertz source, very weak terahertz signals from deep space can be detected, which may help scientists understand the formation of the universe.

Coherent terahertz radiation has historically been very difficult to generate, and the search for an easy-to-use, compact source continues today. Current terahertz sources are large, multi-component systems that may require complex vacuum electronics, external pump lasers, and/or cryogenic cooling. A single component solution without any of these limitations is highly desirable to enable next generation terahertz systems.

One possible avenue toward this goal is to create and mix two mid-infrared laser beams within a single semiconductor chip in the presence of a giant nonlinearity. This nonlinearity allows for new terahertz photons to be created within the same chip with an energy equal to the difference of the mid-infrared lasers' energies. As mid-infrared lasers based on quantum cascade laser technology are operable at room temperature, the terahertz emission can also be demonstrated at room temperature.

Razeghi and her group at the Center for Quantum Devices have taken this basic approach a step further by addressing two key issues that have limited the usefulness of initial demonstrations. Razeghi's group currently leads the world in high-power quantum cascade laser technology; by increasing the power and beam quality of the mid-infrared pumps, the terahertz power has been significantly increased by more than a factor of 30 to ~10 microwatts.

Additionally, the researchers have incorporated a novel dual-wavelength diffraction grating within the laser cavity to create single mode (narrow spectrum) mid-infrared sources, which in turn has led to very narrow linewidth terahertz emission near 4 terahertz. Further, due to the novel generation mechanism, the terahertz spectrum is extremely stable with respect to current and/or temperature. This could make it valuable as a local oscillator, which can be used for low light level receivers like those needed for astronomical applications.

Razeghi said her group will continue in hopes of reaching higher power levels.

"Our goal is to reach milliwatt power levels and incorporate tuning within the device," Razeghi said. "Theory says that it is possible, and we have all of the tools necessary to realize this potential."

Razeghi's work in this area is partially supported by the Defense Advanced Research Projects Agency (DARPA), and she would like to acknowledge the interest and support of Dr. Scott Rodgers of DARPA and Dr. Tariq Manzur of the Naval Undersea Warfare Center


Story Source:

The above story is based on materials provided by Northwestern University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Q. Y. Lu, N. Bandyopadhyay, S. Slivken, Y. Bai, M. Razeghi. Room temperature single-mode terahertz sources based on intracavity difference-frequency generation in quantum cascade lasers. Applied Physics Letters, 2011; 99 (13): 131106 DOI: 10.1063/1.3645016

Cite This Page:

Northwestern University. "Researchers realize high-power, narrowband terahertz source at room temperature." ScienceDaily. ScienceDaily, 30 September 2011. <www.sciencedaily.com/releases/2011/09/110930123052.htm>.
Northwestern University. (2011, September 30). Researchers realize high-power, narrowband terahertz source at room temperature. ScienceDaily. Retrieved July 24, 2014 from www.sciencedaily.com/releases/2011/09/110930123052.htm
Northwestern University. "Researchers realize high-power, narrowband terahertz source at room temperature." ScienceDaily. www.sciencedaily.com/releases/2011/09/110930123052.htm (accessed July 24, 2014).

Share This




More Matter & Energy News

Thursday, July 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

TSA Administrator on Politics and Flight Bans

TSA Administrator on Politics and Flight Bans

AP (July 24, 2014) TSA administrator, John Pistole's took part in the Aspen Security Forum 2014, where he answered questions on lifting of the ban on flights into Israel's Tel Aviv airport and whether politics played a role in lifting the ban. (July 24) Video provided by AP
Powered by NewsLook.com
Creative Makeovers for Ugly Cellphone Towers

Creative Makeovers for Ugly Cellphone Towers

AP (July 24, 2014) Mobile phone companies and communities across the country are going to new lengths to disguise those unsightly cellphone towers. From a church bell tower to a flagpole, even a pencil, some towers are trying to make a point. (July 24) Video provided by AP
Powered by NewsLook.com
Algonquin Power Goes Activist on Its Target Gas Natural

Algonquin Power Goes Activist on Its Target Gas Natural

TheStreet (July 23, 2014) When The Deal's Amanda Levin exclusively reported that Gas Natural had been talking to potential suitors, the Ohio company responded with a flat denial, claiming its board had not talked to anyone about a possible sale. Lo and behold, Canadian utility Algonquin Power and Utilities not only had approached the company, but it did it three times. Its last offer was for $13 per share as Gas Natural's was trading at a 60-day moving average of about $12.50 per share. Now Algonquin, which has a 4.9% stake in Gas Natural, has taken its case to shareholders, calling on them to back its proposals or, possibly, a change in the target's board. Video provided by TheStreet
Powered by NewsLook.com
Robot Parking Valet Creates Stress-Free Travel

Robot Parking Valet Creates Stress-Free Travel

AP (July 23, 2014) 'Ray' the robotic parking valet at Dusseldorf Airport in Germany lets travelers to avoid the hassle of finding a parking spot before heading to the check-in desk. (July 23) 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:
from the past week

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