University of California, Riverside

Department of Electrical and Computer Engineering



Berardi Sensale Rodriguez: Closing the Terahertz Gap with Tunable 2DEG Systems


Berardi Sensale Rodriguez: Closing the Terahertz Gap with Tunable 2DEG Systems
 
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Berardi Sensale Rodriguez: Closing the Terahertz Gap with Tunable 2DEG Systems

February 22, 2013 - 11:00 am
Winston Chung Hall, 205/206

Promising applications in many diverse areas of human endeavor, including medicine, biology, communications, security, astronomy, and so on, terahertz (THz) technology has recently turned into a very active area of scientific research… but it wasn’t this way all the time. The THz frequency band, usually defined in the 0.1-30 THz range, was for decades one of the least explored regions of the elec-tromagnetic spectrum, mainly due to the lack of materials and devices responding to these frequencies in a controllable manner. Even today, there exists a need for devices efficiently manipulating THz waves. In this talk I will discuss tunable two dimensional electron gas (2DEG) systems and how their unique physical properties can be harnessed to develop novel high-performance active THz devices and systems.

I will start by introducing a new class of highly efficient THz reconfigurable devices based on graphene. By employing graphene, an intrinsically 2D semiconductor as the active material, device design with unprecedented degrees of freedom, low-cost, and ease of fabri-cation is possible, thus leading to a substantial improvement with respect to the existing art in terms of controllability of THz waves. Alt-hough in the infrared/visible range the optical absorption of graphene is only a few percent and scarcely controllable, its optical conduc-tivity dramatically increases in the THz range leading to the possibility of electrical control of THz absorption [1-2]. Moreover, by combin-ing active graphene layers with other passive structures augmenting the intensity of the electric field in the graphene, the control over THz waves can be greatly enhanced [3-5]. These devices can be employed as the building blocks for novel THz systems; for instance single detector THz cameras can be developed employing arrays of graphene electro-absorption modulators as electrically reconfigura-ble patterns [6].

Later on, I will also discuss other fascinating properties of tunable 2DEG systems such as electron transport via plasma waves, which can be exploited in the THz range. Based on this phenomenon, novel device concepts for THz detectors and amplifiers can be devel-oped. These devices, named RTD-gated plasma wave HEMTs promise efficient operation at frequencies well above 1 THz [7-8], which has been shown to be very difficult to obtain in conventional high-speed transistors.

Finally, future research directions will be discussed, including: THz beam steering, electron-plasma-wave high-speed active devices and plasmonic integrated circuits, ultrafast THz beam switching and sideband generation, and so on.

 

[1] B. Sensale-Rodriguez et al. Applied Physics Letters, v. 11, 113104, 2011.

[2] B. Sensale-Rodriguez et al. Nature Communications, v.3, 780, 2012.

[3] B. Sensale-Rodriguez et al. Nano Letters, v.12, 4518, 2012.

[4] B. Sensale-Rodriguez et al. Applied Physics Letters, v. 101, 261115, 2012.

[5] R. Yan and B. Sensale-Rodriguez et al., Optics Express, v. 20, 28664, 2012.

[6] B. Sensale-Rodriguez et al., “Terahertz imaging employing graphene modulator arrays”, Optics Express, v. 21, 2324, 2013. .

[7] B. Sensale-Rodriguez et al., ECS Transactions, v. 49, 93, 2012.

[8] B. Sensale-Rodriguez et al., “Power Amplification at THz via Plasma Wave Excitation in RTD-gated HEMTs”, IEEE Trans. Terahertz Sci. Technol., in press, 2013.

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Biography: Berardi Sensale-Rodríguez received his Engineer's degree from Universidad de la República – Uruguay in 2008. He did his doctoral work in the University of Notre Dame under the advice of Prof. Huili Grace Xing. His early research interests were focused on nu-merical modeling of RF/microwave components and analog circuit design oriented towards low power (sub-threshold) portable and implanta-ble electronics. His doctoral work at Notre Dame was focused on the proposal and development of novel THz devices and systems. More recent interests also include optoelectronic devices. He has authored/coauthored over 30 research articles in these and related areas. He is a member of the IEEE, SPIE, APS, and an associate member of the Uruguayan National Researchers System (SNI). He is the recipient of the Best Student Paper Award from IRMMW-THz 2012.

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