Abstract-Preliminary experimental study of graphene-based terahertz radiation excited by an electron beam

Xiaodong Feng, Min Hu, Jun Zhou, Seng Gong, Tao Zhao, Renbin Zhong, Shenggang Liu,

https://ieeexplore.ieee.org/document/8391577

There are several proposed graphene-based coherent terahertz radiation sources excited by an electron beam in the terahertz frequency band. The properties of graphene such as graphene conductivity are of great importance to achieve these graphene-based terahertz radiation sources. In this paper, based on terahertz time-domain spectroscopy, the effects of a 400- eV electron beam on graphene conductivity are presented. The results indicate that exposure to a 400-eV electron beam can cause n-doping in the graphene from the interaction of the electron beam with the graphene film. After a long-time electron beam irradiation, the graphene conductivity decreases, indicating that defects and damages are created in the graphene. The findings are valuable for the further experimental study to realize graphene-based terahertz radiation sources excited by an electron beam.

Abstract-Preliminary experimental study of graphene-based terahertz radiation excited by an electron beam

Xiaodong Feng,   Min Hu,   Jun Zhou,   Seng Gong, Tao Zhao,   Renbin Zhong,  Shenggang Liu, 

https://ieeexplore.ieee.org/document/8391577/

There are several proposed graphene-based coherent terahertz radiation sources excited by an electron beam in the terahertz frequency band. The properties of graphene such as graphene conductivity are of great importance to achieve these graphene-based terahertz radiation sources. In this paper, based on terahertz time-domain spectroscopy, the effects of a 400- eV electron beam on graphene conductivity are presented. The results indicate that exposure to a 400-eV electron beam can cause n-doping in the graphene from the interaction of the electron beam with the graphene film. After a long-time electron beam irradiation, the graphene conductivity decreases, indicating that defects and damages are created in the graphene. The findings are valuable for the further experimental study to realize graphene-based terahertz radiation sources excited by an electron beam.

Abstract-Terahertz radiation in graphene hyperbolic medium excited by an electric dipole

Xiaodong Feng, Sen Gong, Renbin Zhong, Tao Zhao, Min Hu, Chao Zhang, and Shenggang Liu

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-43-5-1187#Abstract

In this Letter, the enhanced and directional radiation in a wide terahertz (THz) frequency range in a graphene hyperbolic medium excited by an electric dipole is presented. The numerical simulations and theoretical analyses indicate that the enhanced radiation comes from the strong surface plasmon couplings in the graphene hyperbolic medium, consisting of alternative graphene and dielectric substrate layers. The simulation results also show that the peak power flow of the enhanced THz radiation in the graphene hyperbolic medium is dramatically enhanced by more than 1 order of magnitude over that in a general medium within a certain distance from the dipole, and the electromagnetic fields are strongly concentrated in a narrow angle. Also, the radiation fields can be manipulated, and the fields’ angular distributions can be tuned by adjusting the dielectric permittivity and thickness of the substrates, and the chemical potential of graphene. Accordingly, it provides a good opportunity for developing miniature, integratable, high-power-density, and tunable radiation sources in the THz band at room temperature.

© 2018 Optical Society of America

Abstract-Calculation and Study of Graphene Conductivity Based on Terahertz Spectroscopy

Xiaodong Feng, Min Hu, Jun Zhou, Shenggang Liu

http://link.springer.com/article/10.1007/s10762-017-0362-5


Based on terahertz time-domain spectroscopy system and two-dimensional scanning control system, terahertz transmission and reflection intensity mapping images on a graphene film are obtained, respectively. Then, graphene conductivity mapping images in the frequency range 0.5 to 2.5 THz are acquired according to the calculation formula. The conductivity of graphene at some typical regions is fitted by Drude-Smith formula to quantitatively compare the transmission and reflection measurements. The results show that terahertz reflection spectroscopy has a higher signal-to-noise ratio with less interference of impurities on the back of substrates. The effect of a red laser excitation on the graphene conductivity by terahertz time-domain transmission spectroscopy is also studied. The results show that the graphene conductivity in the excitation region is enhanced while that in the adjacent area is weakened which indicates carriers transport in graphene under laser excitation. This paper can make great contribution to the study on graphene electrical and optical properties in the terahertz regime and help design graphene terahertz devices.