50 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 67, NO. 1, JANUARY 2019

Spoof Surface Plasmonic Graphene for Controllingthe Transports and Emissions of

Electromagnetic WavesPengfei Qin , Er-Ping Li , Fellow, IEEE, Yihao Yang, Hanzhi Ma, Student Member, IEEE, Bin Zheng, Fei Gao,

Zuojia Wang, Lian Shen, Ran Hao , Lay Kee Ang , and Hongsheng Chen

Abstract— Inspired by the recent development of graphene,we propose and experimentally demonstrate a novel metasur-face, namely, spoof surface plasmonic graphene, for controllingthe transports and emissions of electromagnetic waves. Similarto graphene, at the corners of the Brillouin zone for ourdesigned metasurface, two bands of spoof surface plasmonpolaritons (SSPPs) linearly touch together, forming Dirac-likecones. In the experiments, we directly observed the Dirac conesin the momentum space by using near-field scanning. When thefrequency is changed from the lower cone to the Dirac pointand to the upper cone, the corresponding SSPPs’ transport onthe metasurface shows negative group velocities, pseudodiffusioncharacteristics, and positive group velocities, respectively. Theemission of the SSPPs to the air shows a transition of thewavefront from a concave to flat and finally to convex. Themetasurface proposed here may find many potential applica-tions in directional antennas, waveguide, diffusion-like transport,

Manuscript received June 27, 2018; revised September 2, 2018; acceptedSeptember 17, 2018. Date of publication October 25, 2018; date of cur-rent version January 4, 2019. This work was supported in part by theNational Natural Science Foundation of China under Grant 61571395,Grant 61625502, Grant 61574127, Grant 61601408, Grant 61775193, Grant11704332, and Grant 61801426, in part by the Fundamental ResearchFunds for the Central Universities under Grant 2017XZZX009-02 andGrant 2017XZZX008-06, in part by ZJNSF under Grant LY17F010008,in part by the Top-Notch Young Talents Program of China, and in partby the Innovation Joint Research Center for Cyber-Physical-Society System.(Corresponding author: Yihao Yang.)

P. Qin, E.-P. Li, and H. Ma are with the Key Laboratory of AdvancedMicro/Nano Electronic Devices and Smart Systems and Applications, Collegeof Information Science and Electronic Engineering, Zhejiang University,Hangzhou 310027, China, and also with the Zhejiang University–University ofIllinois at Urbana–Champaign Institute, Zhejiang University, Haining 314400,China (e-mail: qinpf@zju.edu.cn; liep@zju.edu.cn; mahanzhi@zju.edu.cn).

Y. Yang, B. Zheng, F. Gao, L. Shen, and H. Chen are with the KeyLaboratory of Advanced Micro/Nano Electronic Devices and SmartSystems and Applications, College of Information Science and ElectronicEngineering, Zhejiang University, Hangzhou 310027, China, and alsowith the State Key Laboratory of Modern Optical Instrumentation,Electromagnetics Academy, Zhejiang University, Hangzhou 310027, China(e-mail: yangyihaooo@zju.edu.cn; zhengbin@zju.edu.cn; gaofeizju@ju.edu.cn; lianshen@zju.edu.cn; hansomchen@zju.edu.cn).

Z. Wang is with the School of Information Science and Engineering,Shandong University, Jinan 250100, China (e-mail: z.wang@sdu.edu.cn).

R. Hao is with the Key Laboratory of Advanced Micro/Nano ElectronicDevices and Smart Systems and Applications, College of Information Scienceand Electronic Engineering, Zhejiang University, Hangzhou 310027, China(e-mail: rhao@zju.edu.cn).

L. K. Ang is with Engineering Product Development, Singapore Uni-versity of Technology and Design, Singapore 487372 (e-mail: ricky_ang@sutd.edu.sg).

Color versions of one or more of the figures in this paper are availableonline at http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TMTT.2018.2874253

focusing and imaging devices, and integrated spoof plasmoniccircuits.

Index Terms— Artificial graphene, metasurface, spoof surfaceplasmon polaritons (SSPPs).

I. INTRODUCTION

METASURFACES have recently emerged as a newresearch frontier because of their subwavelength thick-

nesses and unprecedented abilities to manipulate light [1].By regulating the local light–matter interactions of meta-atomsand arranging spatial distributions, researchers have demon-strated flexible and efficient control over the amplitudes [2],phases [3], polarizations [4], and angular momentums [5]of propagating light. These interesting properties of planarmetasurfaces indicate that these materials have potential appli-cations in compact optical devices, such as lenses [6], quarter-wave plates [4], holograms [7], and microwave invisibilitycloaks [8]–[10]. The metasurfaces are able to mold the flow ofpropagating light and manipulate the surface plasmon polari-tons (SPPs) [11]–[20]. Metasurfaces, with SPPs manipulationcapability, will be greatly beneficial toward quantum emit-ters [11], [12], sensing [13], and integrated optical metacir-cuits [11], among others.

Spoof SPPs (SSPP), a type of near-field wave proposedby Pendry et al. [21], which can propagate in structuredperfect electric conductors to mimic the optical propertiesof natural SPPs. With strong light confinement and largefield enhancement, SSPPs provide solutions to realize theminiaturization of microwave integrated circuits [22]–[25].Unlike SPPs, SSPPs are produced from interactions betweenelectromagnetic waves and the impedance induced by thedesigned metal surfaces [26]–[32]. Recent studies on SSPPshave revealed their promising potential applications, such asflexible antennas [24], [25], waveguides [33], sensors [34], andintegrated circuits [35].

It is well-known that graphene is a 2-D honeycomb latticecomposed of a single layer of carbon atoms, which hasfound numerous applications [36], [37]. One of the mostimportant features of graphene is its Dirac cones at thecorners of the Brillouin zone, which are formed by the linearcrossing of the conduction and valence bands, where thecorresponding touching points are usually named as Dirac

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QIN et al.: SPOOF SURFACE PLASMONIC GRAPHENE FOR CONTROLLING TRANSPORTS AND EMISSIONS 51

Fig. 1. Schematics of the spoof surface plasmonic graphene. Top viewof the proposed metasurface and the corresponding hexagonal unit cell. Themetasurface is with a sandwich structure: bottom ground plane, dielectricsubstrate, and top metallic patterns. Here, the brown and gray regions representthe copper and dielectric materials, respectively. The thicknesses of the copperand the substrate are t1 = 0.035 mm and t = 1 mm, respectively. The sidelength of the hexagon is l = 5 mm, the lattice constant is 8.66 mm, the widthof the groove is w = 0.5 mm, and the distance between the groove and theboundary is d = 0.25 mm. The present metasurface has two types of edges,which are armchair and zigzag edges, respectively.

Fig. 2. (a) Calculated band structure of the proposed spoof surface plasmonicgraphene. (b) FBZ of the unit cell. Black dash lines: light lines in the air.

points. Such a feature provides remarkable electronic prop-erties like Klein tunneling [38], negative refraction [39], andZitterbewegung (ZB) [40]–[42].

In this paper, a graphene-like metasurface is proposed andexperimentally demonstrated which can manipulate transportsand emissions of SSPPs at microwave frequencies. Therefore,it is named as a spoof surface plasmonic graphene. By scan-ning the near-field distributions and applying a spatial Fouriertransformation, we directly observe the Dirac cones at the

Fig. 3. (a) Ez field distribution of two degenerate modes at 9.8 GHz on thexy plane 1 mm above the metasurface. (b) Ez field distribution of the twodegenerate modes at 9.8 GHz on the yz plane.

corners of the first Brillouin zone (FBZ) in the momentumspace of the present spoof surface plasmonic graphene. Ourfindings show that the SSPPs traveling on the metasurface fea-tures a pseudodiffusion characteristic at the Dirac frequency.The shape of the wavefront of the emission is also experimen-tally demonstrated, which is from concave to flat and finallyto convex as the frequency increases. Such a spoof surfaceplasmonic graphene is expected to provide good tunabilityand flexibility for potential application in microwave antennaand devices by controlling the transports and emissions of theSSPPs.

II. SPOOF SURFACE PLASMONIC GRAPHENE AND

SIMULATION RESULTS

A. Structure of the Proposed Spoof Surface PlasmonicGraphene

The proposed spoof surface plasmonic graphene is a hexag-onal lattice with a metal–dielectric–metal sandwich structure:bottom ground plane, dielectric substrate, and top metallicpatterns (Fig. 1). The brown regions are the metal (copper witha conductivity of 5.7×107 S/m) with thickness t1 = 0.035 mm;the side length of the hexagon is l = 5 mm; the width ofthe splits is w = 0.5 mm; the distance between the splitsand the boundary of the unit cell is d = 0.25 mm; and thelattice constant is a = 8.66 mm. The gray regions are ofthe 1-mm-thick dielectric substrate with relative permittivity2.55 + 0.001i at the frequency below 10 GHz. The bottommetal layer works as a ground plane. The whole structurepossesses a C6v symmetry, which is the key to achieve stableDirac cones at the corner of the Brillouin zone in its reciprocalspace [43]. Therefore, in the design, we start from the basicsymmetry and then optimize the geometry to get the proposedstructure.

52 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 67, NO. 1, JANUARY 2019

Fig. 4. Simulated Ez field distributions and the corresponding isofrequency contour in the momentum space at different frequencies. Simulated Ez fielddistributions on the xy plane 1 mm above the metasurface at (a) 7.6, (b) 8.4, (c) 9.8, (d) 10.6, and (e) 11.4 GHz, respectively. Numerical isofrequency contourat (f) 7.6, (g) 8.4, (h) 9.8, (i) 10.6, and (j) 11.4 GHz, respectively.

B. Dispersion Analyses of the Spoof Surface PlasmonicGraphene

The band structure of our proposed spoof surface plasmonicgraphene, as shown in Fig. 2(a), is numerically obtained byemploying the eigenmodes solver of the commercial softwareComputer Simulation Technology (CST) Microwave Studio.The dashed lines represent the light cone in the air. Onecan see that the first and second bands linearly touch eachother at corners (K and K �) of the FBZ at the frequency of9.8 GHz, forming Dirac-like cones. The previous theoreticalstudies have revealed such a conical dispersion by solving thewell-known Dirac Hamiltonian in natural graphene [44] andartificial graphene systems [42]. The FBZ of the unit cell of theproposed metasurface is depicted in Fig. 2(b), which possesses� − K mirror symmetry due to the C6v symmetry of the unitcell.

The Ez field distributions of the unit cell on the xy planeat 9.8 GHz are depicted in Fig. 3(a), showing two degeneratemodes existing at the Dirac frequency which can verify Diracpoint and Dirac cone in momentum space of the proposedstructure. Fig. 3(b) shows the Ez field distributions of thetwo modes on the yz plane, indicating that the electric field isstrongly confined near the metasurface in the z-direction. It isworth noting that the Dirac points in our metasurface are veryrobust and it can survive in changing the geometry parametersof the unit cell without breaking its symmetry. This is becausethe whole system processes a C6v symmetry, resulting in theC3v symmetry of the K (K �) point which can protect the Diracpoints [43].

C. Simulated Near-Field Distributions on the Metasurfaceand the Corresponding Momentum Space

To visualize the electric field distributions over the meta-surface, we perform full-wave simulations in the time-domainsolver of the CST simulator. In the simulations, an electricdipole connected two metal layers is placed at the left side

Fig. 5. Experimental setup. An electric dipole antenna is located at theleft side of the metasurface to excite the SSPPs, and another electric dipoleantenna is fixed at the arm of the 3-D movement platform to detect thez-polarized electric field. The insets enlarge the source antenna and thedetector electric dipole antenna, respectively.

of the metasurface. Fig. 4(a)–(e) shows the simulated Ez

field distributed on the xy plane 1 mm above the structure at7.6, 8.4, 9.8, 10.6, and 11.4 GHz, respectively. Interestingly,one can observe that the electric field clearly “diffuses”out almost immediately from a point to a plane wave at9.8 GHz, the Dirac frequency [Fig. 4(c)], while the SSPPsexhibits ballistic transport slightly below or above this fre-quency [Fig. 4(b) and (d)]. Such a unique transport featureis attributed to the pseudodiffusion effect of energy fluxes atthe Dirac points [45]. Because the direction of the energy fluxis determined by the group velocity, vg = ∂ω/∂k, and thedispersion at the Dirac points is nondifferentiable, which willlead to the omnidirectional energy flux, therefore, a diffusion-like transport. The pseudodiffusion transport is different fromthe ballistic one. For the ballistic transport, the transmissionalmost stays the same, when the distance increases; however,for the pseudodiffusion transport, the transmission is inverselyproportional to the distance [46]. Besides, the pseudodiffusiontransport also gives rise to a temporal beating for transmittedpulses that is independent to the distance, which is an analog ofthe so-called ZB effect of the relativistic electron [41]. To visu-alize the Dirac cones, we map the Ez field distributions ontothe momentum space at different frequencies with a spatial

QIN et al.: SPOOF SURFACE PLASMONIC GRAPHENE FOR CONTROLLING TRANSPORTS AND EMISSIONS 53

Fig. 6. Measured Ez field distribution and the corresponding isofrequency contours in the momentum space at different frequencies. Measured Ez fielddistributions on the xy plane 1 mm above the metasurface at (a) 7.57, (b) 8.47, (c) 9.76, (d) 10.57, and (e) 11.47 GHz, respectively. At the Dirac frequency,the pseudodiffusion behavior of the SSPPs can be directly observed. Measured isofrequency contours of the dispersions in the momentum space at (f) 7.57,(g) 8.47, (h) 9.76, (i) 10.57, and (j) 11.47 GHz, respectively. At the Dirac frequency, one can directly observe six Dirac points at the corner of the FBZ. Thecircle at the center is the dispersion of free-space electromagnetic wave.

Fourier transformation [47], [48], as shown in Fig. 4(f)–(j).One can see that the band structure is similar to that of naturalgraphene [37]. Especially, at 9.8 GHz, there are several pointsat the corners of the FBZ, namely, Dirac points, and the bandstructure is almost symmetrical slightly below and above thisfrequency.

III. EXPERIMENTAL VERIFICATION

A. Experimental Setup

The experimental structure is made up such that thehexagon-shaped resonator metal structures are deposited ona substrate: a 1-mm teflon woven glass fabric copper-cladlaminate with a permittivity of 2.55 and a loss tangentof 0.001 below 10 GHz.

In the experiment, an electric dipole antenna between thetwo metal layers in the experimental setup is located at the leftside of the metasurface to excite the SSPPs with transverseelectric polarizations (i.e., out-of-plane electric field and in-plane magnetic field) similar to the source setting in thesimulations. Another electric dipole antenna is fixed at the armof the 3-D movement platform to detect the z-polarized electricfield on a horizontal plane 1 mm above the sample shownin Fig. 5. The insets enlarge the area of two electric dipoleantennas that are connected to the vector network analyzerto probe both the amplitude and phase of the Ez field pointby point. The measured region is 300 by 300 mm, and theresolution is 2 mm.

B. Experimental Results and Discussion

The measured Ez field distributions are shownin Figs. 6(a)–(e) at the frequencies of 7.57, 8.47, 9.76,10.57, and 11.47 GHz, respectively. At all frequencies,the measured field distributions are well correlated withthe simulated counterparts in all frequencies. Interestingly,

Fig. 7. Measured isofrequency of the dispersion around K valley near theDirac frequency. A Dirac cone is observed at the Brillouin zone corner from8.43 to 10.87 GHz, with its Dirac point at 9.76 GHz.

we directly observe that the electromagnetic wave emittedfrom the point source diffuses immediately and cover almostall of the metasurface at the Dirac frequency [Fig. 6(c)].We then apply a spatial Fourier transformation to obtain theisofrequency contour of the dispersion in the momentumspace at each frequency, which is shown in Fig. 6(f)–(j).One can observe that the isofrequency contour at 9.76 GHzexactly shows several Dirac points at the corners of the FBZ,and the isofrequency contour at the other frequencies aresimilar to the simulation results.

The enlarged Dirac cone is shown in Fig. 7, where aring gradually shrinks to the point of 9.76 GHz and thenreopens as the frequency increases. This measured Dirac cone

54 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 67, NO. 1, JANUARY 2019

Fig. 8. Measured Ez field distributions outside the metasurface at (a) 10.7,(b) 9.76, and (c) 8.6 GHz, respectively. An expanding pattern is observed at10.7 GHz while a focusing pattern is observed at 8.6 GHz. sAt the Diracfrequency, the plane wave is observed.

matches the calculated dispersion shown in Fig. 2(a). It isfascinating that the group velocity of the SSPPs varies fromnegative to positive when increasing the frequency aroundthe Dirac frequency. When putting a point source on themetasurface, it excites the SSPPs that will emit to the airvia the armchair edge of the metasurface [49]. The transitionsof the wavefront outside the metasurface at 10.7, 9.76, and8.6 GHz are measured as shown in Fig. 8(a)–(c), respectively.At the Dirac frequency, the wavefront of the electromagneticwave emitted from the point source becomes a plane waveshown in Fig. 8(b). This is because the topology of theisofrequency contour becomes a point at K point. Thus, thereare only several discretized wavevectors for the SSPPs. Whenthe SSPPs reach the armchair boundary, due to the boundarymatching condition, only the SSPPs with a wavevector verticalto the boundary can pass through the armchair boundary,leading to the flat wavefront. Note that no matter how largeis the metasurface, and the emitted wave from the arm-chair boundaries is always in the same phase and amplitude.Therefore, such a phenomenon can be used to design highlydirective antennas and diffusion-like transport, focusing andimaging devices with an ultrathin planar structure. When thefrequency is below the Dirac frequency, the group velocityof the SSPPs becomes negative. As the group velocity of theelectromagnetic wave in air is positive, at the interface betweenthe metasurface and the air, negative refraction takes place,leading to the concave wavefront, as shown in Fig. 8(c).

Such a phenomenon can be beneficial for imaging andfocusing systems. Above the Dirac frequency, the normalrefraction occurs due to positive group velocities in the

metasurface and air [Fig. 8(a)]. If involving some activecomponents, one can change the emissions from concave toflat and to convex at a fixed frequency, achieving a switchableemission device.

IV. CONCLUSION

A novel metasurface to control the transports and emissionsof electromagnetic waves is presented in this paper by com-bining artificial graphene and SSPPs at microwave frequencyrange. The proposed spoof surface plasmonic graphene pos-sesses conical dispersions at the corner of the FBZ. As thefrequency is varied from the lower cone to the Dirac pointand to the upper cone, the propagation of the SSPPs on themetasurface shows different effects: negative group velocities,pseudodiffusion characteristics, and positive group velocities,respectively. The wavefront of the emissions of the SSPPs tothe air, varies from a concave to a flat and finally to a convexshape, has potential applications in highly directional antennas,imaging and focusing devices. Our proposed graphene-likemetasurface will also work as the bricks of the integratedmicrowave circuits.

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Pengfei Qin received the B.Eng. degree fromthe College of Information Science and ElectronicEngineering, Zhejiang University, Hangzhou, China,in 2014, where he is currently pursuing the Ph.D.degree in electronics science and technology.

In 2018, he joined the Singapore University ofTechnology and Design, Singapore, as a VisitingStudent. His current research interests include meta-materials, metasurfaces, and spoof surface plasmons.

Er-Ping Li (S’91–M’92–SM’01–F’08) received thePh.D. degree in electrical engineering from SheffieldHallam University, Sheffield, U.K., in 1992.

In 2000, he joined the Research Institute ofHigh Performance Computing, A∗STAR, Singapore,as a Principal Scientist and the Director. Since1989, he has been a Research Fellow, a Prin-cipal Research Engineer, an Associate Professor,and the Technical Director with the SingaporeResearch Institute and University. He is currentlya Changjiang-Qianren Distinguished Professor with

the Department of Information Science and Electronic Engineering, ZhejiangUniversity, Hangzhou, China, and also the Dean of the Joint Institute ofZhejiang University–University of Illinois at Urbana–Champaign, ZhejiangUniversity. His current research interests include electrical modeling anddesign of micro-/nano-scale integrated circuits, 3-D electronic package inte-gration, and nanoplasmonic technology.

Dr. Li is the founding member of the IEEE MTT-RF NanotechnologyCommittee and a Fellow of the MIT Electromagnetics Academy, USA. Hewas a recipient of the 2015 IEEE Richard Stoddard Award on EMC, theIEEE EMC Technical Achievement Award, the Singapore IES PrestigiousEngineering Achievement Award, and the Changjiang Chair ProfessorshipAward from the Ministry of Education, China, and a number of Best PaperAwards. He was elected the IEEE EMC Distinguished Lecturer in 2007.He served as an Associate Editor for IEEE MICROWAVE AND WIRELESS

COMPONENTS LETTERS from 2006 to 2008 and as the Guest Editor for the2006 and 2010 IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATI-BILITY Special Issues and the 2010 IEEE TRANSACTIONS ON MICROWAVE

THEORY AND TECHNIQUES Asia–Pacific Microwave Conference SpecialIssue. He is currently an Associate Editor of the IEEE TRANSACTIONSON ELECTROMAGNETIC COMPATIBILITY and the IEEE TRANSACTIONS ON

COMPONENTS, PACKAGING, AND MANUFACTURING TECHNOLOGY. He hasbeen a General Chair and Technical Chair for many international conferences.He was the President of the 2006 International Zurich Symposium on EMC,the founding General Chair of the Asia–Pacific EMC Symposium, GeneralChair of 2008, 2010, 2012, and 2016 APEMC, and the 2010 IEEE Symposiumon Electrical Design for Advanced Packaging Systems. He has been invitedto give numerous invited talks and plenary speeches at various internationalconferences and forums.

Yihao Yang received the B.Eng. degree in electron-ics and communication engineering from the Schoolof Electronics and Information, South China Uni-versity of Technology, Guangzhou, China, in 2012,and the Ph.D. degree in electronics science and tech-nology from the Department of Information Scienceand Electronic Engineering, Zhejiang University,Hangzhou, China, in 2017.

He is currently a Research Fellow with the Cen-ter for Disruptive Photonic Technologies, NanyangTechnological University, Singapore. His current

research interests include topological photonics, metamaterials, metasurfaces,and invisibility cloaks.

56 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 67, NO. 1, JANUARY 2019

Hanzhi Ma (S’17) received the B.S. degree in engi-neering from Zhejiang University, Hangzhou, China,in 2017. She is currently pursuing the Ph.D. degreeat the Department of IS and Electronic Engineer-ing, Zhejiang University–University of Illinois atUrbana–Champaign Institute, Zhejiang University.

Her current research interests include machinelearning technique for electromagnetic interfer-ence/MEC analysis.

Bin Zheng received the B.S. degree from NingboUniversity, Ningbo, China, in 2010, and the Ph.D.degree from Zhejiang University, Hangzhou, China,in 2015.

Since 2015, he has been a Post-DoctoralResearcher with Zhejiang University, where he hasbeen a Lecturer with the College of InformationScience and Electronic Engineering since 2017.His current research interests include transformationoptics, metamaterials, metasurfaces, and invisibilitycloaks.

Fei Gao received the B.Sc. degree in applied physicsfrom Sichuan University, Chengdu, China, in 2007,the M.Sc. degree in condensed matter physics fromNanjing University, Nanjing, China, in 2010, andthe Ph.D. degree in physics and applied physicsfrom Nanyang Technological University, Singapore,in 2016.

From 2010 to 2012, he was a Research Assistantwith the Shenzhen Institute of Advanced Technol-ogy, Chinese Academy of Science. From 2016 to2018, he was a Research Fellow with Nanyang

Technological University. In 2018, he joined the Department of ElectricalEngineering, Zhejiang University, Hangzhou, China, where he holds a tenure-track position. His current research interests include topological electromag-netics, metamaterials, photonic crystals, acoustic crystals, and photon–phononinteractions.

Dr. Gao was selected in the Young 1000 Talents Plan in 2018.

Zuojia Wang received the B.E. degree in elec-tronic and information science and Ph.D. degree inelectronics science and technology from ZhejiangUniversity, Hangzhou, China, in 2009 and in 2016,respectively.

From 2014 to 2016, he was a Visiting ResearchScholar with the Department of Mechanical andIndustrial Engineering, Northeastern University,Boston, MA, USA. He is currently an AssociateProfessor with the School of Information Scienceand Engineering, Shandong University, Jinan, China.

His current research interests include metamaterials, chiral optics, antennas,plasmonics, and nanophotonics.

Lian Shen received the B.S. degree from NingboUniversity, Ningbo, China, in 2008, the M.A. degreefrom Halmstad University, Halmstad, Sweden,in 2011, and the Ph.D. degree from Zhejiang Uni-versity, Hangzhou, China, in 2017.

He was a Visiting Scholar with the BirckNanotechnology Center, Purdue University, WestLafayette, IN, USA. He is currently a Post-DoctoralResearcher with the College of Information Scienceand Electronic Engineering, Zhejiang University.

Ran Hao received the Ph.D. degree from UniversitéParis-Sud XI, Orsay, France, in 2010, and the Ph.D.degree from the Wuhan National Laboratory forOptoelectronics, Wuhan, China, in 2011.

He is currently a Ph.D. Supervisor with ZhejiangUniversity, Hangzhou, China. At present, he ismainly engaged in the basic research of opticaldevices based on 2-D materials and silicon-basedmicro/nano-optoelectronic systems.

Dr. Hao was a recipient of the French NationalScholarship during his doctoral studies.

Lay Kee Ang received the B.S. degree fromNational Tsing Hua University, Hsinchu, Taiwan,in 1994, and the M.S. and Ph.D. degrees in nuclearengineering and plasma physics from the Universityof Michigan, Ann Arbor, MI, USA, in 1996 and1999, respectively.

He is currently the Head of Science and Math,the Interim Head of Pillar of EPD, and an Ng TengFong Chair Professor with the Singapore Universityof Technology and Design, Singapore. His currentresearch interests include the development of theo-

retical scaling laws and models that are able to capture the essential physics inany interesting problems with a strong focus on the physics and applicationsof charge particles (electrons), and photons (laser and electromagnetic wave)with 2-D materials and plasma.

Hongsheng Chen received the B.S. and Ph.D.degrees in electrical engineering from ZhejiangUniversity, Hangzhou, China, in 2000 and 2005,respectively.

In 2005, he joined Zhejiang University, as anAssistant Professor where he was an Associate Pro-fessor in 2007 and a Full Professor in 2011. From2006 to 2008, he was a Visiting Scientist with theResearch Laboratory of Electronics, MassachusettsInstitute of Technology, Cambridge, MA, USA,where he was a Visiting Professor from 2013 to

2014. His current research interests include the areas of metamaterials,invisibility cloaking, transformation optics, and theoretical and numericalmethods of electromagnetics.

Dr. Chen was a recipient of the National Excellent Doctoral DissertationAward in China in 2008, the Zhejiang Provincial Outstanding Youth Foun-dation in 2008, the National Youth Top-Notch Talent Support Program inChina in 2012, the New Century Excellent Talents in University of Chinain 2012, the National Science Foundation for Excellent Young Scholars ofChina in 2013, the Distinguished Chang Jiang Scholar Professorship from theChinese Ministry of Education in 2014, and the National Science Foundationfor Distinguished Young Scholars of China in 2016. He serves as a RegularReviewer for many international journals on electromagnetics, physics, optics,and electrical engineering. He serves as the Topical Editor for the Journalof Optics and is on the Editorial Board of Nature’s Scientific Reports andProgress in Electromagnetics Research.