Featured Research

from universities, journals, and other organizations

First Room-temperature Semiconductor Source Of Coherent Terahertz Radiation Demonstrated

Date:
May 20, 2008
Source:
Harvard University
Summary:
Engineers and applied physicists from Harvard University have demonstrated the first room-temperature electrically-pumped semiconductor source of coherent Terahertz radiation, also known as T-rays. The breakthrough in laser technology, based upon commercially available nanotechnology, has the potential to become a standard Terahertz source to support applications ranging from security screening to chemical sensing.

A photograph of a bar with 10 terahertz laser sources developed by the Harvard University engineers. One of the lasers is connected to the contact pad (seen on the left) by two thin gold wires. A 2mm-diameter Silicon hyper-hemispherical lens is attached to the facet of the device to collimate the terahertz output. The emission frequency is 5 THz, corresponding to a wavelength of 60 microns.
Credit: Courtesy of the Capasso Lab, Harvard School of Engineering and Applied Sciences

Engineers and applied physicists from Harvard University have demonstrated the first room-temperature electrically-pumped semiconductor source of coherent Terahertz (THz) radiation, also known as T-rays. The breakthrough in laser technology, based upon commercially available nanotechnology, has the potential to become a standard Terahertz source to support applications ranging from security screening to chemical sensing.

Spearheaded by research associate Mikhail Belkin and Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, both of Harvard's School of Engineering and Applied Sciences (SEAS), the findings will be published in the May 19 issue of Applied Physics Letters. The researchers have also filed for U.S. patents covering the novel device.

Using lasers in the Terahertz spectral range, which covers wavelengths from 30 to 300ε, has long presented a major hurdle to engineers. In particular, making electrically pumped room-temperature and thermoelectrically-cooled Terahertz semiconductor lasers has been a major challenge. These devices require cryogenic cooling, greatly limiting their use in everyday applications.

"By contrast, our device emits T-rays with several hundreds of nanowatts of power at room temperature and microwatts of power at temperatures easily achievable with commercially available thermoelectric coolers," says Belkin. "Further, there is the potential of increasing the terahertz output power to milliwatt levels by optimizing the semiconductor nanostructure of the active region and by improving the extraction efficiency of the terahertz radiation."

To achieve the breakthrough and overcome the temperature limitations of current laser designs, the researchers engineered a room temperature mid-infrared Quantum Cascade Laser (QCL) that emits light at two frequencies simultaneously. The generation of Terahertz radiation occurs via the process of difference-frequency generation inside the laser material at room temperature at a frequency of 5 THz (equal to the difference of the two mid-infrared QCL frequencies).

Mid-infrared QCLs were invented and demonstrated by Capasso and his team at Bell Labs in 1994. The compact millimeter length semiconductor lasers operate routinely at room temperature with high optical powers and are increasingly used in the commercial sector for wide range of applications in chemical sensing and trace gas analysis. The devices, made by stacking ultra-thin atomic layers of semiconductor materials on top of each other, are variable and tunable, allowing an engineer to adjust the energy levels in the structure to create artificial laser medium.

"Terahertz imaging and sensing is a very promising but relatively new technology that requires compact, portable and tunable sources to achieve widespread penetration. Our devices are an important first step in this direction," said Capasso. "We believe our THz source has great development potential because the nanoscale material used was grown by Molecular Beam Epitaxy, a commercial and widely used thin film growth technique which 'spray paints' atoms on a surface one layer at a time."

The ability of Terahertz rays to penetrate efficiently through paper, clothing, cardboard, plastic and many other materials makes them ideal for use in many applications. For example, a device emitting T-rays could be used to image concealed weapons, detect chemical and biological agents through sealed packages, see tumors without causing any harmful side effects, and spot defects within materials such as cracks in the Space Shuttle's foam insulation.

Belkin and Capasso's co-authors are Feng Xie and Alexey Belyanin, Department of Physics at Texas A&M University, College Station; and Milan Fischer, Andreas Wittmann, and Jιrτme Faist, Institute of Quantum Electronics at ETH, Zόrich, Switzerland. The research was supported by the Air Force Office of Scientific Research and the National Science Foundation. The authors also acknowledge the support of two Harvard-based centers, the Nanoscale Science and Engineering Center and the Center for Nanoscale Systems, a member of the National Nanotechnology Infrastructure Network.


Story Source:

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


Cite This Page:

Harvard University. "First Room-temperature Semiconductor Source Of Coherent Terahertz Radiation Demonstrated." ScienceDaily. ScienceDaily, 20 May 2008. <www.sciencedaily.com/releases/2008/05/080519083023.htm>.
Harvard University. (2008, May 20). First Room-temperature Semiconductor Source Of Coherent Terahertz Radiation Demonstrated. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2008/05/080519083023.htm
Harvard University. "First Room-temperature Semiconductor Source Of Coherent Terahertz Radiation Demonstrated." ScienceDaily. www.sciencedaily.com/releases/2008/05/080519083023.htm (accessed October 21, 2014).

Share This



More Matter & Energy News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Thanks, Marty McFly! Hoverboards Could Be Coming In 2015

Thanks, Marty McFly! Hoverboards Could Be Coming In 2015

Newsy (Oct. 21, 2014) — If you've ever watched "Back to the Future Part II" and wanted to get your hands on a hoverboard, well, you might soon be in luck. Video provided by Newsy
Powered by NewsLook.com
Robots to Fly Planes Where Humans Can't

Robots to Fly Planes Where Humans Can't

Reuters - Innovations Video Online (Oct. 21, 2014) — Researchers in South Korea are developing a robotic pilot that could potentially replace humans in the cockpit. Unlike drones and autopilot programs which are configured for specific aircraft, the robots' humanoid design will allow it to fly any type of plane with no additional sensors. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com
Graphene Paint Offers Rust-Free Future

Graphene Paint Offers Rust-Free Future

Reuters - Innovations Video Online (Oct. 21, 2014) — British scientists have developed a prototype graphene paint that can make coatings which are resistant to liquids, gases, and chemicals. The team says the paint could have a variety of uses, from stopping ships rusting to keeping food fresher for longer. Jim Drury reports. Video provided by Reuters
Powered by NewsLook.com
Massive Air Bag Recall Affects More Than 4.5 Million Vehicles

Massive Air Bag Recall Affects More Than 4.5 Million Vehicles

Reuters - US Online Video (Oct. 21, 2014) — Major automakers are recalling millions of vehicles due to potentially defective front passenger air bag inflators that can rupture and spray metal shrapnel. Linda So reports. Video provided by Reuters
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