Abstract-High-precision digital terahertz phase manipulation within a multichannel field perturbation coding chip

 

Hongxin Zeng, Huajie Liang, Yaxin Zhang, Lan Wang, Shixiong Liang, Sen Gong, Zheng Li, Ziqiang Yang, Xilin Zhang, Feng Lan, Zhihong Feng, Yubin Gong, Ziqiang Yang, Daniel M. Mittleman

 

Fig. 1: MFPCC architecture and its high-precision terahertz phase manipulation function.

Fig. 2: Perturbation and phase shift of a single 2DEG-PMU with 0 and 1 states.

https://www.nature.com/articles/s41566-021-00851-6

Direct phase modulation is one of the most urgent and difficult issues in the terahertz research area. Here, we propose a new method employing a two-dimensional electron gas (2DEG) perturbation microstructure unit coupled to a transmission line to realize high-precision digital terahertz phase manipulation. We induce local perturbation resonances to manipulate the phase of guided terahertz waves. By controlling the electronic transport characteristics of the 2DEG using an external voltage, the strength of the perturbation can be manipulated, which affects the phase of the guided waves. This external control permits electronic manipulation of the phase of terahertz waves with high precision, as high as 2−5° in the frequency range 0.26–0.27 THz, with an average phase error of only 0.36°, corresponding to a timing error of only 4 fs. Critically, the average insertion loss is as low as 6.14 dB at 0.265 THz, with a low amplitude fluctuation of 0.5 dB, so the device offers near-ideal phase-only modulation.

Abstract-High-precision digital terahertz phase manipulation within a multichannel field perturbation coding 2DEG meta-chip

Hongxin Zeng, Huajie Liang, Yaxin Zhang, Ziqiang Yang, Feng Lan, Shixiong Liang, Zheng Li, Lan Wang, Xilin Zhang, Sen Gong, Yubin Gong, Ziqiang Yang, 

https://www.researchsquare.com/article/rs-92448/v1

Terahertz phase manipulation has always been based on direct coupling of the resonance of quasi-optical terahertz waves with metamaterials, which is accompanied by unnecessary amplitude modulation, thus limiting the accuracy of phase manipulation and its application in monolithic integrated systems. Here, we propose a coding meta-chip composed of transmission lines and two-dimensional electron gas (2DEG) meta-atoms, wherein local perturbation resonances are induced to manipulate the phase of terahertz waves. By controlling the electronic transport characteristics of the 2DEG with external voltages, the intensity of the perturbation can be manipulated, which affects the transmission phase of the waves. More importantly, the perturbation resonances induced by different meta-atoms can be coupled so that through digital coding of the perturbation state of 2DEG meta-atoms, the terahertz wave transmission phase can be manipulated with high precision. As a result, phase manipulation with different precisions from 2° to 5° is observed from 0.26 to 0.27 THz, where the average phase error is only 0.36°, and the maximum root mean square of the transmittance is 0.36 dB. This high-precision phase manipulation via field coding has great application potential in the fields of beamforming, wireless communication, and high-resolution imaging.

Abstract-The Enhanced Third Harmonic Superradiation of Smith Purcell Terahertz radiation source

 Sen Gong, Tao Zhao, Shenggang Liu, Zhenhua Wu, Pengfei Hu, Min Hu, Yueheng Cao, Xiaoqiuyan 

Zhang

https://ieeexplore.ieee.org/document/8510515

Here we propose a new method to enhance the third harmonic of superradiant Smith-Purcell. In this paper, the specific designed grating structure enhances the power of the third harmonic by suppressing the second harmonic. Therefore, the higher frequency radiation signal (25 mW, 326 GHz) is generated by the lower energetic electron beam (9 keV)passing through the grating with larger size (0.4 mm), compared with normal superradiation by using PIC simulation. Accordingly, this mechanism is expected to achieve more efficient compact and tunable terahertz radiation sources with higher frequency.

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-Observation of graphene surface plasmon polaritons excited by free electron beam

Min Hu,  Sen Gong, Tao Zhao,  Renbin Zhong,  Chengpeng Yu,   Shenggang Liu

http://ieeexplore.ieee.org/document/8066948/

In previous work, we propose to develop a novel kind of terahertz radiation source which utilizing free electron beam to excited graphene surface plasmon polaritons (GSPPs) combining vacuum electronics and new 2D material graphene. The previous theoretical analysis show that this coherent radiation source can be tuned covering almost whole THz frequency range and work at room temperature. In this paper, we demonstrate the conductivity mapping of GSPPs with free electron beam excitation using TDS system. The characteristics of GSPPs can be derived from the calculated conductivity results and be compared with the theoretical Drude model, which would guide the next step of the experiment to realize the new kind of THz source.

Abstract-Optical bistability induced by nonlinear surface plasmon polaritons in graphene in terahertz regime

Matthew Sanderson¹, Yee Sin Ang¹, Sen Gong^2,3, Tao Zhao^2,3, Min Hu^2,3, Renbin Zhong^2,3, Xiaoxing Chen^2,3, Ping Zhang^2,3, Chao Zhang^1,3,a) and Shenggang Liu^2,3
http://scitation.aip.org/content/aip/journal/apl/107/20/10.1063/1.4936232?TRACK=RSS
a) czhang@uow.edu.au
Appl. Phys. Lett. 107, 203113 (2015); http://dx.doi.org/10.1063/1.4936232

We demonstrate optical bistability in a prism-air-graphene-dielectric structure. Under a moderate electric field in the terahertz frequency regime, the third order nonlinear optical conductivity is comparable to the linear conductivity. The nonlinear conductivity enhances the energy of surface plasmonpolaritons. Both the energy and frequency of the surface plasmonpolaritons depend on the strength of the nonlinear current in the graphene layer. When considering excitation in the Kretschmann configuration, the reflectance as a function of frequency exhibits bistability. The origin of the bistability is the field dependence of the plasmon mode. We have determined the parameter regime for the occurrence of bistability in this structure.

Abstract-Coherent and Tunable Terahertz Radiation from Graphene Surface Plasmon Polarititions Excited by Cyclotron Electron Beam

Tao Zhao

, Sen Gong

, Min Hu

, Renbin Zhong

, Diwei Liu

, Xiaoxing Chen

, Ping Zhang

, Xinran Wang

,Chao Zhang

, Peiheng Wu

 & Shenggang Liu

http://www.nature.com/articles/srep16059

Terahertz (THz) radiation can revolutionize modern science and technology. To this date, it remains big challenges to develop intense, coherent and tunable THz radiation sources that can cover the whole THz frequency region either by means of only electronics (both vacuum electronics and semiconductor electronics) or of only photonics (lasers, for example, quantum cascade laser). Here we present a mechanism which can overcome these difficulties in THz radiation generation. Due to the natural periodicity of 2π of both the circular cylindrical graphene structure and cyclotron electron beam (CEB), the surface plasmon polaritions (SPPs) dispersion can cross the light line of dielectric, making transformation of SPPs into radiation immediately possible. The dual natural periodicity also brings significant excellences to the excitation and the transformation. The fundamental and hybrid SPPs modes can be excited and transformed into radiation. The excited SPPs propagate along the cyclotron trajectory together with the beam and gain energy from the beam continuously. The radiation density is enhanced over 300 times, up to 105 W/cm2. The radiation frequency can be widely tuned by adjusting the beam energy or chemical potential. This mechanism opens a way for developing desired THz radiation sources to cover the whole THz frequency regime.

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.

Abstract-Free electron terahertz wave radiation source with two-section periodical waveguide structures

http://jap.aip.org/resource/1/japiau/v111/i6/p063107_s1?isAuthorized=no

Weihao Liu, Sen Gong, Yaxin Zhang, Jun Zhou, Ping Zhang, and Shenggang Liu

Terahertz Science and Technology Research Center, University of Electronic Science and Technology of China, Chengdu 610054, China 

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(Received 20 December 2011; accepted 24 February 2012; published online 26 March 2012)

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We analyze a free electron terahertz wave radiation source with two-section periodical waveguide structure (PWS), where the first section (section-I) is used to pre-modulate the electron beam and the second section (section-II) is for terahertz wave generation. By means of theoretical analysis and numerical simulations, we demonstrate that the starting current density of the beam-wave interaction in section-II can be significantly reduced provided that the operation frequency is the harmonic of electron beam’s pre-modulation frequency. This kind of source can generate relatively high power terahertz wave radiation but only need moderate beam current density. And it may have great potential application in developing the compact and high power terahertz wave radiation source.

© 2012 American Institute of Physics