Paving the way for tunable graphene plasmonic THz amplifiers

Date:
September 8, 2020
Source:
Tohoku University
Summary:
Researchers have successfully demonstrated a room-temperature
coherent amplification of terahertz (THz) radiation in graphene,
electrically driven by a dry cell battery.



FULL STORY ========================================================================== Tohoku University Professor Taiichi Otsuji has led a team of international researchers in successfully demonstrating a room-temperature coherent amplification of terahertz (THz) radiation in graphene, electrically
driven by a dry cell battery.


========================================================================== Roughly 40 years ago, the arrival of plasma wave electronics opened
up a wealth of new opportunities. Scientists were fascinated with the possibility that plasma waves could propagate faster than electrons,
suggesting that so-called "plasmonic" devices could work at THz
frequencies. However, experimental attempts to realize such amplifiers
or emitters remained elusive.

"Our study explored THz light-plasmon coupling, light absorption, and amplification using a graphene-based system because of its excellent room- temperature electrical and optical properties," said Professor Otsuji
who is based at the Ultra-Broadband Signal Processing Laboratory at
Tohoku University's Research Institute of Electrical Communication (RIEC).

The research team, which consisted of members from Japanese, French,
Polish and Russian institutions, designed a series of monolayer-graphene channel transistor structures. These featured an original dual-gathering
gate that worked as a highly efficient antenna to couple the THz
radiations and graphene plasmons.

Using these devices allowed the researchers to demonstrate tunable
resonant plasmon absorption that, with an increase in current, results
in THz radiation amplification. The amplification gain of up to 9% was
observed in the monolayer graphene -- far beyond the well-known landmark
level of 2.3% that is the maximum available when photons directly interact
with electrons without excitation of graphene plasmons.

To interpret the results, the research team used a dissipative plasmonic crystal model, capturing the main trends and basic physics of the
amplification phenomena. Specifically, the model predicts the increase
in the channel dc current that drives the system into an amplification
regime. This indicates that the plasma waves may transfer the dc energy
into the incoming THz electromagnetic waves in a coherent fashion.

"Because all results were obtained at room temperature, our experimental results pave the way toward further THz plasmonic technology with a
new generation of all-electronic, resonant, and voltage-controlled THz amplifiers," added Professor Otsuji.


========================================================================== Story Source: Materials provided by Tohoku_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Stephane Boubanga-Tombet, Wojciech Knap, Deepika Yadav, Akira Satou,
Dmytro B. But, Vyacheslav V. Popov, Ilya V. Gorbenko, Valentin
Kachorovskii, Taiichi Otsuji. Room-Temperature Amplification of
Terahertz Radiation by Grating-Gate Graphene Structures. Physical
Review X, 2020; 10 (3) DOI: 10.1103/PhysRevX.10.031004 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200908113337.htm

--- up 2 weeks, 1 day, 6 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)