Abstract-Graphene Surface-polariton in-Plane Cherenkov Radiation

Jin Tao,  Lin Wu, Guoxing Zheng

https://www.blogger.com/blogger.g?blogID=124073320791841682#editor/target=post;postID=7421418378889081700

The Cherenkov plasmonic radiation in/parallel graphene plane is demonstrated theoretically. It is shown that the graphene Cherenkov radiation can be excited by a moving electron at a relative lower speed, which greatly reduced the difficulty for the Cherenkov radiation realization due to the low phase velocity and high field confinement of graphene plasmons. The excited graphene plasmons wavelength and the Cherenkov radiation angle can be dynamically changed by varying the Femi energy levels, which provides a versatile, tunable mechanism for plasmonic Cherenkov effect in active integrated photonic applications.

Abstract-Ultra-Broadband Linear Polarization Conversion via Diode-Like Asymmetric Transmission with Composite Metamaterial for Terahertz Waves

Yongzhi Cheng, Rongzhou Gong, Lin Wu,

http://link.springer.com/article/10.1007/s11468-016-0365-4
In this paper, a tri-layer metamaterial composed of a split-disk structure array sandwiched with two layers of twisted sub-wavelength metal grating is proposed and investigated numerically in terahertz region. The numerical results exhibit that linear polarization conversion via diode-like asymmetric transmission for terahertz waves within ultra-broadband frequency range is achieved due to Fabry-Perot-like resonance. In our design, the conversion polarization transmission coefficient for normal incidence is greater than 90 % in the range of 0.23–1.17 THz, equivalent to 134.3 % relative bandwidth. The physical mechanism of the broadband linear polarization conversion effect is further illustrated by simulated electrical field distributions.

Abstract-Charge transfer plasmon resonances across silver-molecule-silver junctions: Estimating the Terahertz conductance of molecules at near-infrared frequencies

Lin Wu,   Shu Fen Tan ,   Michel Bosman,   Joel K.W. Yang,  Christian A. Nijhuis and   Ping Bai  

RSC Adv., 2016, Accepted Manuscript

DOI: 10.1039/C6RA16826D
Received 30 Jun 2016, Accepted 18 Jul 2016
http://pubs.rsc.org/en/content/articlelanding/2016/ra/c6ra16826d#!divAbstract

Quantum plasmon resonances have been recently observed across molecular tunnel junctions made of two plasmonic resonators bridged by a self-assembled monolayer (SAM). The energy of this quantum plasmon mode, i.e., the tunneling charge transfer plasmon (tCTP), depends on the properties of the molecules bridging the gaps. The present work extends these studies theoretically using a generalized space-charge corrected electromagnetic model to a wider range of SAM structures (with various molecular lengths and conductances) sandwiched between silver nanocubes, which could support different types of CTP resonances in addition to tCTP. The space-charge corrected electromagnetic model treats the charge injection and charge transport separately, and assumes a Drude expression (with damping frequency on the order of driving frequency) to model the space-charge limited transport problem. Our theoretical modelling of these organic-inorganic hybrid structures establishes a one-to-one relationship between the conductivity of the SAM and the resonant energy of the CTP modes. Considering that the SAM consists of a finite number of molecules bridging the two nanocubes in a parallel arrangement, we introduce a method to estimate the molecular conductance at the CTP resonant frequency. Experimental results from two types of SAMs were examined as a proof-of-concept: the THz conductance is estimated to be 0.2G0 per EDT (1,2-ethanedithiolate) molecule at 140 THz and 0.4G0 for a BDT (1,4-benzeneditiolate) molecule at 245 THz. This approach paves the way of using plasmonic oscillations for measuring the THz conductance of single molecules at near-infrared frequencies.

Abstract-Quantum Plasmon Resonances Controlled by Molecular Tunnel Junctions

1. Shu Fen Tan1, 
2. Lin Wu2, 
3. Joel K.W. Yang3,4, 
4. Ping Bai*,2, 
5. Michel Bosman*,3, 
6. Christian A. Nijhuis*,1,3,5,6
7. 1. http://www.sciencemag.org/content/343/6178/1496.abstract

-Author Affiliations

1. ¹Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
2. ²Institute of High Performance Computing, A*STAR (Agency for Science, Technology and Research), 1 Fusionopolis Way, 16-16 Connexis North, Singapore 138632, Singapore.
3. ³Institute of Materials Research and Engineering, A*STAR, 3 Research Link, Singapore 117602, Singapore.
4. ⁴Singapore University of Technology and Design, 20 Dover Drive, Singapore 138682, Singapore.
5. ⁵Graphene Research Center, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore.
6. ⁶Solar Energy Research Institute of Singapore (SERIS), National University of Singapore, Singapore 117574, Singapore.

1. ↵*Corresponding author. E-mail: baiping@ihpc.a-star.edu.sg (P.B.), michel.bosman@gmail.com (M.B.),christian.nijhuis@nus.edu.sg (C.A.N.)

Quantum tunneling between two plasmonic resonators links nonlinear quantum optics with terahertz nanoelectronics. We describe the direct observation of and control over quantum plasmon resonances at length scales in the range 0.4 to 1.3 nanometers across molecular tunnel junctions made of two plasmonic resonators bridged by self-assembled monolayers (SAMs). The tunnel barrier width and height are controlled by the properties of the molecules. Using electron energy-loss spectroscopy, we directly observe a plasmon mode, the tunneling charge transfer plasmon, whose frequency (ranging from 140 to 245 terahertz) is dependent on the molecules bridging the gaps.