TST, Vol. 9, No. 3, PP. 82-92
Electromagnetic amplification by means of noble metal surface plasmon polaritons excited by electron beam
Gong Sen 1*, 2, Zhao Tao 1, 2 , Hu Min 1, 2 , Zhong Renbin 1, 2 , Zhang Ping 1, 2 , Yu Chengpeng 1, 2, and Liu Shenggang 1*, 2
1 Terahertz Science and Technology Research Center, University of Electronic Science and Technology of China, Chengdu, Sichuan, China, 610054
2 Cooperative Innovation Centre of Terahertz Science, National 2011 project
*1 Email: gongsen@uestc.edu.cn
(Received September 10, 2016)
Abstract: In this paper, the electromagnetic wave amplification in the frequency regime from visible light to ultra-violet based on noble metal surface plasmon polaritons (SPPs) excited by electron beam is presented. The theoretical analyses and numerical calculations show that SPPs can be amplified by the interaction between the electron beam and the waves, provided the beam velocity is a little bit larger than the phase velocity of SPPs wave. The gain of the amplification reaches up to about 10 dB/cm for the current density 200 A/cm2 or even lower. When the beam velocity is larger than the Cherenkov radiation threshold, the SPPs can be transformed into radiation. The results of numerical calculations also show that promising amplification gain can also be obtained in the structure with parameters larger than nanometers, and this is of great significance for practical manufacture and applications.
Keywords: Amplification, Surface plasmon polaritons, Electron beam
doi: 10.11906/TST.082-092.2016.09.08
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TST, Vol. 9, No. 3, PP. 93-100
Terahertz amplification by electron beam excited graphene surface plasmon polaritons in a planar structure
Zhao Tao 1, 2* , Gong Sen 1, 2, Hu Min 1, 2 , Zhong Renbin 1, 2 , Zhang Ping 1, 2 , Yu Chengpeng 1, 2, and Liu Shenggang 1, 2
1 Terahertz Science and Technology Research Center, University of Electronic Science and Technology of China, Chengdu, Sichuan, China, 610054
2 Cooperative Innovation Centre of Terahertz Science, National 2011 project
* Email: forzhaotao@126.com
(Received September 10, 2016)
Abstract：A novel physical mechanism for development of Terahertz amplifier with plannar structure is presented in this paper. The theoretical analysis study and numerical calculations have been carried out, the significant results show that 12.69 dB per 1 mm length can be obtained. In principle, the mechanism is quite similar to that of space charge theory.
Keywords: Electron beam, Surface plasmon polaritons, Amplifier, Terahertz, Planar structure
doi: 10.11906/TST.093-100.2016.09.09
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TST, Vol. 9, No. 3, PP. 101-108
Terahertz amplification by electron beam excited graphene surface plasmon polaritons in a cylindrical structure
Zhao Tao 1, 2* , Gong Sen 1, 2, Hu Min 1, 2 , Zhong Renbin 1, 2 , Zhang Ping 1, 2 , Yu Chengpeng 1, 2, and Liu Shenggang 1, 2
1 Terahertz Science and Technology Research Center, University of Electronic Science and Technology of China, Chengdu, Sichuan, China, 610054
2 Cooperative Innovation Centre of Terahertz Science, National 2011 project
* Email: forzhaotao@126.com
(Received September 10, 2016)
Abstract: Graphene surface plasmon polaritons (SPPs) exhibit strong mode confinement and long propagation distances, and the characteristics are tunable via changing the chemical potential, etc. In this paper, we propose a novel physical mechanism that the graphene SPPs excited by electron beam can be used to amplify terahertz (THz) waves. Theoretical results show that the energy transfers from electron beam to the SPPs occurs when the velocity of electron beam is moderately faster than the phase velocity of SPPs. This is just the similar results by the space charge wave theory. The physical mechanism may provide great potential for graphene SPPs-based amplifiers.
Keywords: Electron beam, Surface plasmon polaritons, Amplifier, Terahertz, Cylindrical structure
doi: 10.11906/TST.101-108.2016.09.10
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TST, Vol. 9, No. 3, PP. 109-116
Graphene conductivity mapping by terahertz time-domain reflection spectroscopy
Xiaodong Feng, Min Hu *, Jun Zhou, and Shenggang Liu
University of Electronic Science and Technology of China
Terahertz Science and Technology Research Center, Chengdu, China
* Email: hu_m@uestc.edu.cn
(Received September 10, 2016)
Abstract: We present a combination for centimetre scale quantitative graphene conductivity mapping by terahertz time-domain transmission and reflection spectroscopy in the frequency range 0.5 THz to 2.5 THz. The results agree well with each other and show that a higher signal-to-noise ratio is acquired through reflection measurement as a result of less influence of pollutants on the back of the substrate. Therefore, we can use terahertz reflection spectroscopy for graphene conductivity on any non-metallic substrates including substrates that THz wave cannot get through well. The graphene conductivity is well fitted by the Drude-Smith formula, which indicates the remarkable impact of carrier backscattering. Furthermore, we employ THz time-domain reflection spectroscopy for graphene conductivity mapping of a graphene/Si sample and find regional differences of the conductivity which can contribute to graphene surface plasmon polaritons and graphene modulators.
Keywords: Graphene conductivity, Terahertz spectroscopy, Transmission, Reflection, Drude-smith
doi: 10.11906/TST.109-116.2016.09.11
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