His current research interests include the areas of metamaterials, antennas, invisibility cloaking, transformation optics, and graphene. Tunable graphene metasurface reflectarray for cloaking. The panoramic lens is a special kind of lens, which is applied to observe full view. In the absence of any transformation optics, the plasmon mode propagating along the graphene sheet from the far left, would su.
A longterm goal of electronics has been to make devices smaller, faster, lighter and cheaper. We investigate a novel implementation of hyperbolic metama. Transformation optics using graphene ashkan vakil and nader engheta metamaterials and transformation optics play substantial roles in various branches of optical science and engineering by providing schemes to tailor electromagnetic fields into desired spatial patterns. The unique optical properties of graphene result in electrically tunable plasmons that allow for extreme confinement of electromagnetic energy in the technologically significant regime of thz frequencies. Recently, transformation optics to based on graphene have received considerable attentions by offering new possibilities to manipulate the propagation of gps 4, in which one graphene sheet can be regarded as a.
Graphene as a platform for ir metamaterials tunability of graphene conductivity is an exciting feature inhomogeneous conductivity patterns lead to ir oneatomthick transformation optics numerous optical devices can be envisioned. Plasmons in graphene 1,2,3,4 can be tuned by using electrostatic gating or chemical doping 5,6,7, and the ability to confine plasmons in very small regions could have applications in. As we describe in this article, the concept of transformation optics embraces some of the spectacular recent applications of metamaterials. Freespace carpet cloak using transformation optics and graphene. Lee1, choongi choi2, sungyool choi4, xiang zhang3,5 and bumki min1 the extraordinary electronic properties of graphene provided. Graphenebased terahertz antennas for areaconstrained applications.
Freespace carpet cloak designed with transformation optics requires materials exhibiting simultaneously anisotropic properties and plasmalike behaviors, but materials that simultaneously meet these requirements are rarely found in nature. Graphene is in many ways the ultimate thin film, only one. The reflections of such structures are investigated by analytical effective medium theory combined with transfer matrix method emttmm and numerical finite element method fem. This approach is based on the fact that object being invisible is to be concealed behind an arti. Such radiative loss is typically dependent on the radius of curvature of the bump. Department of electrical and electronic engineering, the university of hong kong, pokfulam. Atomically localized plasmon enhancement in monolayer graphene. We compute the optical conductivity of graphene beyond the usual dirac cone approximation, giving results that are valid in the visible region of the conductivity spectrum.
Figure 1 illustrates our approach to fabricate the doublelayer graphene optical modulator. Design of highgain lens antenna by gradientindex metamaterials using transformation optics. Transformation optics and metamaterials purdue engineering. Due to the aforementioned extraordinary properties of graphene, it is suitable for use in many applications, including transformation optics 15, filters 7, absorbers 8,16,17, and optical. In this paper we propose the biomimetic motheye antireflection structures on graphene sheet based on transformation optics. Department of electrical engineering and computer science, university of california, irvine, ca, 92697, usa. Transformation optics is an emerging field of research aiming to conceal an object by bending or distorting electromagnetic waves using spatially varying metamaterials 49, 50. Unidirectional invisibility and pt symmetry withgraphene. This study presents an effective method to model, analyse and design graphene metasurfacebased terahertz thz absorbers using equivalent circuit model approach. Transformation optics has been proved to be a general methodology for taming and controlling electromagnetic waves in any desired manner 1. However, to has not permitted us to confine, manipulate, and control spp waves on.
Here media, possibly made of metamaterials, are designed such that they appear to perform a coordinate transformation from physical space to some virtual electromagnetic space. Transformation optics has been shown to be a powerful tool for studying graphene 9 and as we have shown in a previous paper 8, the grating can strongly couple incident radiation to plasmons. The past few years have witnessed tremendous achievements. Metamaterials and transformation optics have received considerable attention in the recent years, as they have found an immense role in many areas of optical science and engineering by offering schemes to control electromagnetic. Switching terahertz waves with gatecontrolled active. Nov 01, 2015 in the practical fabrication, the hemisphere surface is composed of some graphene ribbons with fixed refractive index. Graphene, plasmons and transformation optics request pdf. Osa flexible transformation plasmonics using graphene. Engheta, transformation optics using graphene, science 3326035, 12911294 2011. Design examples of a beam squeezer, bend, and omnidirectional absorber.
Design of an ultrawideband antenna using flexible graphenebased conductor sheets sajid m. Zhenzhong yu, yijun feng, zhengbin wang, junming zhao, tian jiang. In this paper, we will show how surface conductivity. For this conductivity for the wavenumber for the tm spp given above, we have. The recently discovered graphene has shown unique anisotropic plasmalike behavior benefitting from its natural twodimensional structure and inplane. Xu and xiangdong zhang, optics express 19, 22999 2011. The ability to control the spatial variation of permittivity and permeability by electrical means would yield new perspectives on adaptive electromagnetic cloaking and. This cited by count includes citations to the following articles in scholar. Abstract here we theoretically show, by designing and manipulating spatially inhomogeneous, non. We make use of transformation optics 29 32 to derive the optical spectrum of such gratings within the quasistatic approximation, study their plasmonic response. The terahertz thz gap lying between the microwave and optical parts of the electromagnetic spectrum has attracted immense attention due to its applications between radiofrequency rfmicrowave and photonic systems. From optical graphene to topological insulator collaborator. Transformation optics to offers the capability either to confine the spp propagation on rigid curveduneven surfaces, or to control the flow of spps on planar surfaces. Tunable spatial mode converters and optical diodes for.
A planar electromagnetic black hole based on graphene. The guiding principle is einsteins principle of covariance. Electrically tunable damping of plasmonic resonances with. Metamaterials and transformation optics play substantial roles in various branches of optical science and engineering by providing schemes to tailor. The flexible control of surface plasmon polaritons spps is important and intriguing due to its wide application in novel plasmonic devices. Metamaterial cloaking is the usage of metamaterials in an invisibility cloak. Graphene disks for frequency control of terahertz waves in. It is known that by varying the chemical potential using gate electric andor magnetic fields, the. Transformation optics asks, using maxwells equations, what kind of electromagnetic medium recreates some smooth deformation of space. We describe the general methodology for the design of transformation optical devices for surface plasmons and analyze, for. Graphenebased terahertz antennas for areaconstrained.
Plasmonic cloak using graphene at infrared frequencies. Introduction light absorption in thin films has always been a relevant topic in optics, especially from the application point of view. Analysis of infrared spectra with narrow band absorption. Analysis of infrared spectra with narrow band absorption by a. Steve cummer also assesses how the to algorithm can and has been successfully extended to other disciplines such as acoustics, elastodynamics and heat flow. Here we theoretically show, by designing and manipulating spatially inhomogeneous, nonuniform conductivity patterns across a single flake of graphene, that this singleatomlayered material can serve as a oneatomthick platform for infrared metamaterials and transformation optical devices. Here, we add an extra degree of freedom by using graphene as a. We report a theoretical study showing that by designing and manipulating spatially inhomogeneous, nonuniform conductivity patterns across a flake of graphene, one can have this. When the effective mode index of the graphene n gp is designed and changes following eq. Tuning optical responses of metallic dipole nanoantenna using graphene xingang ren, wei e. The absorption rates of graphenesquarering structures calculated by simulation are 90. Graphenebased tunable hyperbolic metamaterials and. A graphene covered on squarering structure is designed and fabricated to achieve narrow band absorption of three peaks in the infrared band.
Graphene plasmonic lens for manipulating energy flow. Oneatomthick ir metamaterials and transformation optics using graphene. The former one exploits the beauty of transformation optics and stunning e. Pdf transformation optics and metamaterials researchgate. According to, the effective refractive index of graphene has little relationship with its thickness, for saving simulation computer resource, the graphene thickness is set as 1 nm. Transformation optics aims to identify artificial materials and structures with desired electromagnetic properties by means of pertinent coordinate transformations.
Besides conductivity, we show that the loss of graphene can also be controlled. Electrically tunable graphene plasmonic quasicrystal. Oneatomthick ir metamaterials and transformation optics. Metamaterials direct and control the propagation and transmission of specified parts of the light spectrum and demonstrate the potential to render an object seemingly invisible. Broadband and tunable absorbers consisting of graphene metasurface and metalbacked dielectric layer have been designed based on the formulas derived from this approach and verified. This could be useful for designing oneatomthick metamaterial and transformation optics devices based on graphene 7. We report a theoretical study showing that by designing and manipulating spatially inhomogeneous, nonuniform conductivity patterns across a flake of graphene, one can have this material as a. Osa active control of optical chirality with graphene. Ultracompact phase modulators based on graphene plasmons 27 june 2017 phase modulation due to a local wavelength change. Tunable metamaterial with gold and graphene splitring. Downloaded from transformation optics using graphene. The operational characteristics angle of beam steering, focal distance, angular e ciency, losses etc. Yee, numerical solution of initial boundary value problems involving maxwells equations in isotropic. Manipulating surface plasmon waves by transformation optics.
Mar 26, 2012 we have proposed and demonstrated the modulating spp waves by using a singlelayer graphene to realize the concept of black hole, based on the transformation optics. This ingenious application apparently is a big step toward real breakthrough of graphene optics. Oneatomthick optical devices based on graphene abstract metamaterials and transformation optics have received considerable attention in the recent years, as they have found an immense role in many areas of optical science and engineering by offering schemes to control electromagnetic fields. Panoramic lens designed with transformation optics. Design of an ultrawideband antenna using flexible graphenebased conductor sheets. Graphene, plasmons and transformation optics p a huidobro1, m kraft1, r kun2, s a maier1 and j b pendry1 1imperial college london, department of physics, the blackett laboratory, london sw7 2az, uk 2school of precision instrument and optoelectronics engineering, tianjin university, tianjin tianjin 300072, people. Vakil and n, engheta, transformation optics using graphene, science, vol. Ultracompact phase modulators based on graphene plasmons. Here we theoretically study oneatomthick metamaterials, oneatomthick waveguide elements, cavities, mirrors, lenses, fourier optics and finally a few case studies illustrating transformation optics on a single sheet of graphene in midinfrared wavelengths. In the simulations, the radius of the hemisphere a is 100 nm. This is accomplished by manipulating the paths traversed by light through a novel optical material. The absorption rates of graphene squarering structures calculated by simulation are 90. Tunable graphene metasurface reflectarray for cloaking, illusion, and focusing sudipta romen biswas,1 cristian e.
The ones marked may be different from the article in the profile. Tunable graphene metasurface re ectarray for cloaking. Controlling spatial patterns of plasmons constitutes a basis for a variety of applications in the fields of plasmonics, metamaterials, and transformation optics 1,2,3. Graphene can be used as a platform for transformationoptics devices due to its tunability of conductivity. Metamaterials and transformation optics play substantial roles in various branches of optical science and engineering by providing schemes to tailor electromagnetic fields into desired spatial patterns. Pdf document this is an authorcreated, uncopyedited version of an article accepted for publication in journal of optics. Both analytical and numerical methods have shown that the average reflection losses of 1%. Using this priority and taking the advantage of transformation optics, we realize the concept of electromagnetic black hole by using of a singlelayer.
In general, such schemes are meant to appropriately tailor the constitutive parameters of metamaterials in order to control the trajectory of light in two and three dimensions. He has been a visiting scientist during 20062008 and a visiting professor during 202014 with the research laboratory of electronics at massachusetts institute of technology, usa. Jun 10, 2011 metamaterials and transformation optics play substantial roles in various branches of optical science and engineering by providing schemes to tailor electromagnetic fields into desired spatial patterns. Transformation optics using graphene science, 3326035, 12911294. May, 2010 flexible transformation plasmonics using graphene. Pdf underpinned by the advent of metamaterials, transformation optics offers. Beyond optics, martin wegener takes us from using to to improve solar cell efficiency to transformation mechanics, showing how mechanical cloaks can improve the utility of scaffolds. A structure consisting of a graphene sheet sandwiched between two graphene disks is introduced herein to control the reflection, absorption, and. Oneatomthick ir metamaterials and transformation optics using. Therefore, relying on the freedom in varying graphene conducitivty by using the methods mentioned above, by tuning the level of chemical potential locally, we can create desired patterns of effective index for spp surface waves. Govorov, plasmoninduced circular dichroism of a chiral molecule in the vicinity of metal nanocrystals.
This requirement fixes very precisely the required electromagnetic medium. Graphenebased tunable hyperbolic metamaterials and enhanced near. Introduction graphene, a one atom thick layer of carbon atoms arranged in a honeycomb lattice 1, features unique optical 2 and optoelectronic properties 3. Electrically switchable metadevices via graphene science. Metamaterials and transformation optics have received considerable attention in the recent years, as they have found an immense role in many areas of optical science and engineering by offering schemes to control electromagnetic fields. Oneatomthick ir metamaterials and transformation optics using graphene ashkan vakil and nader engheta university of pennsylvania department of electrical and systems engineering philadelphia, pennsylvania 19104, u. It is based on the application of the concept of transformation optics to devise the optical parameters of the dielectric medium placed on top of the metal surface. Varying the graphene chemical potential by using static electric field yields a way to tune the graphene conductivity in the terahertz and infrared frequencies. Singlelayer graphene construction can be used to create oneatomthick optical elements. Pdf optical conductivity of graphene in the visible. Transformation optics using graphene 5 optical properties of graphene.
Tr ansformation optics scheme for tw odimensional materials. Invisibility studies in literature bifurcate as cloaking using transformation optics and transfer matrix methods. In this letter, we theoretically present a panoramic lens pl using transformation optics method. Another area of science that has been under the spotlight for the last few years relates to exploration of graphene, which is formed of carbon atoms densely. Adaptive tetrahedral meshing with a minimum feature resolution of 0. In addition, using two graphene layers for the active medium can further increase the optical absorption and modulation depth, giving advantages including smaller footprint and lower power consumptions. Graphene as a tunable anisotropic or isotropic plasmonic. Apr 19, 2016 we demonstrate a tunable plasmonic metasurface by considering a graphene sheet subject to a periodically patterned doping level.
Hyperlens based on monolayer graphene and boron nitride. We demonstrate a tunable plasmonic metasurface by considering a graphene sheet subject to a periodically patterned doping level. Because the tunability of the chemical potential of the graphene, we can see that it is feasible to realize the graded refractive index by manipulating the conductivity of graphene. Transformation optics using graphene scholarlycommons. Tuning optical responses of metallic dipole nanoantenna using. Engheta, transformation optics using graphene, science 332, 12911294 2011. Pdf susyinspired onedimensional transformation optics.