People use electromagnetic energy every day … watching television, listening to
the radio, popping corn with a microwave, taking an X-ray or using a cell phone. This energy travels in the form of waves, which are widely used in electronic and wireless devices. One of the hottest areas of the electromagnetic spectrum being explored today is the terahertz (THz) range. Terahertz waves, lying between microwave and optical frequencies, offer improved performance for a variety of applications in everyday life. For instance, THz waves can carry more information than radio/microwaves for communications devices. They also provide medical and biological images with higher resolution than microwaves, while offering much smaller potential harm of exposure than X-rays.
Researchers at the University of Notre Dame have shown that it is possible to
efficiently manipulate THz electromagnetic waves with atomically thin graphene layers. This achievement, which was recently published in Nature Communications, sets the stage for development of compact, efficient and cost-effective devices and systems operating in the THz band.
“A major bottleneck in the promise of THz technology has been the lack of
efficient materials and devices that manipulate these energy waves,” says Berardi Sensale- Rodriguez, a graduate student in the Department of Electrical Engineering at Notre Dame. “Having a naturally two-dimensional material with strong and tunable response to THz waves, for example, graphene, gives us the opportunity to design THz devices achieving unprecedented performance.”
The terahertz team — graduate students Berardi Sensale-Rodriguez, Rusen Yan, Kristof Tahy and Tian Fang; research assistant professors Michelle M. Kelly [throughCenter for Nanoscience and Technology (NDnano)] and Lei Liu [in conjunction withAdvanced Diagnostics & Therapeutics (AD&T) at Notre Dame]; visiting research assistant professor Wan Sik Hwang [with Midwest Institute of Nanoelectronics Discovery (MIND)]; Associate Professor Debdeep Jena and John Cardinal O’Hara, C.S.C., Associate Professor Huili (Grace) Xing — has demonstrated the first proof of concept prototype of a graphene-based THz modulator, a device enabled solely by intraband transitions in graphene.
 Graphene, an atom-thick semiconductor material, has shown promising electrical, mechanical and thermal properties leading to the recent demonstration of fast transistors, flexible/transparent electronics, optical devices and now terahertz active components. “Graphene has been touted as an ideal platform to discover new, as well as prove/dispute existing, physical phenomena since 2004. That is what two physicists in the United Kingdom, Andre Geim and Konstantin Novoselov, were awarded the Nobel Prize for in 2010,” says Xing. “However, very few real-world applications of graphene have emerged to date. Using graphene to manipulate THz waves is one of such applications.
This Nature Communication paper documented our first experimental effort to realize the predictions in our paper published in Applied Physics Letters last year. Devices with better performance continue rolling out of our laboratories.” Xing also comments, “Though Professor Jena and I formed the vision to use two-dimensional electron gas to manipulate THz waves back in 2006, it was not until Michelle, Lei and Berardi joined us that this piece of work was possible.”
This research was supported by the National Science Foundation and the Office of Naval Research, as well MIND, NDnano and AD&T.
For more information, contact Huili (Grace) Xing at 574-631-9108 begin_of_the_skype_highlighting 574-631-9108 end_of_the_skype_highlighting or hxing@nd.edu. |
Showing posts with label Tian Fang. Show all posts
Showing posts with label Tian Fang. Show all posts
Tuesday, May 1, 2012
Graphene-based Terahertz Devices: the Wave of the Future
Friday, April 20, 2012
Abstract-Broadband graphene terahertz modulators enabled by intraband transitions
Terahertz technology promises myriad applications including imaging, spectroscopy and communications. However, one major bottleneck at present for advancing this field is the lack of efficient devices to manipulate the terahertz electromagnetic waves. Here we demonstrate that exceptionally efficient broadband modulation of terahertz waves at room temperature can be realized using graphene with extremely low intrinsic signal attenuation. We experimentally achieved more than 2.5 times superior modulation than prior broadband intensity modulators, which is also the first demonstrated graphene-based device enabled solely by intraband transitions. The unique advantages of graphene in comparison to conventional semiconductors are the ease of integration and the extraordinary transport properties of holes, which are as good as those of electrons owing to the symmetric conical band structure of graphene. Given recent progress in graphene-based terahertz emitters and detectors, graphene may offer some interesting solutions for terahertz technologies.
Monday, September 12, 2011
Researchers at Notre Dame harness graphene for use in controlling THz
http://www.newswise.com/articles/aip-s-physics-news-highlights-september-12-2011
Researchers from the University of Notre Dame in Indiana have harnessed another one of graphene’s remarkable properties to better control a relatively untamed portion of the electromagnetic spectrum: the terahertz band. Terahertz radiation offers tantalizing new opportunities in communications, medical imaging, and chemical detection. Straddling the transition between the highest energy radio waves and the lowest energy infrared light, terahertz waves are notoriously difficult to produce, detect, and modulate. Modulation, or varying the height of the terahertz waves, is particularly important because a modulated signal can carry information and is more versatile for applications such as chemical and biological sensing. Some of today’s most promising terahertz technologies are based on small semiconductor transistor-like structures that are able to modulate a terahertz signal at room temperature, which is a significant advantage over earlier modulators that could only operate at extremely cold temperatures. Unfortunately, these transistor-like devices rely on a thin layer of metal called a “metal gate” to tune the terahertz signal. This metal gate significantly reduces the signal strength and limits how much the signal can be modulated to a lackluster 30 percent. As reported in the AIP’s journal Applied Physics Letters, by replacing the metal gate with a single layer of graphene, the researchers have predicted that the modulation range can be significantly expanded to be in excess of 90 percent. This modulation is controlled by applying a voltage between the graphene and semiconductor. Unlike the metal gate modulator, the graphene design barely diminished the output power of the terahertz energy. Made up of a one-atom-thick sheet of carbon atoms, graphene boasts a host of amazing properties: it’s remarkably strong, a superb thermal insulator, a conductor of electricity, and now a better means to modulate terahertz radiation.
Article: “Unique prospects for graphene-based terahertz modulators” is accepted for publication in Applied Physics Letters.
Authors: Berardi Sensale-Rodriguez (1), Tian Fang (1), Rusen Yan (1), Michelle M. Kelly (1), Debdeep Jena (1), Lei Liu (1), and Huili (Grace) Xing (1).
(1) Department of Electrical Engineering, University of Notre Dame
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