Coherent and tunable terahertz radiation from graphene surface plasmon polaritons excited by an electron beam

Shenggang Liu^1,2,a), Chao Zhang^1,2,3, Min Hu^1,2, Xiaoxing Chen^1,2, Ping Zhang^1,2, Sen Gong^1,2, Tao Zhao^1,2 and Renbin Zhong^1,2
 HIDE AFFILIATIONS
1 Terahertz Research Centre, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, China
2 Cooperative Innovation Centre of Terahertz Science, Chengdu, Sichuan 610054, China
3 School of Physics and Institute for Superconducting and Electronic Materials, University of Wollongong, New South Wales 2522, Australia
a) liusg@uestc.edu.cn
Appl. Phys. Lett. 104, 201104 (2014); http://dx.doi.org/10.1063/1.4879017
http://scitation.aip.org/content/aip/journal/apl/104/20/10.1063/1.4879017

Although surface plasmon polaritons (SPPs) resonance in graphene can be tuned in the terahertz regime, transforming such SPPs into coherent terahertz radiation has not been achieved. Here, we propose a graphene-based coherent terahertz radiation source with greatly enhanced intensity. The radiation works at room temperature, it is tunable and can cover the whole terahertz regime. The radiation intensity generated with this method is 400 times stronger than that from SPPs at a conventional dielectric or semiconducting surface and is comparable to that from the most advanced photonics source such as a quantum cascade laser. The physical mechanism for this strong radiation is presented. The phase diagrams defining the parameters range for the occurrence of radiation is also shown.