A graphene antenna is a high-frequency antenna based on graphene, a one atom thick two dimensional carbon crystal, designed to enhance radio communications. [1] [2] [3] [4] The unique structure of graphene would enable these enhancements. Ultimately, the choice of graphene for the basis of this nano antenna was due to the behavior of electrons.
It would be unfeasible to simply reduce traditional metallic antennas to nano sizes, because they would require tremendously high frequencies to operate. [5] [6] [7] Consequently, it would require a lot of power to operate them. Furthermore, electrons in these traditional metals are not very mobile at nano sizes and the necessary electromagnetic waves would not form. However, these limitations would not be an issue with graphene's unique capabilities. A flake of graphene has the potential to hold a series of metal electrodes. Consequently, it would be possible to develop an antenna from this material. [8] [9]
Graphene has a unique structure, wherein, electrons are able to move with minimal resistance. This enables electricity to move at a much faster speed than in metal, which is used for current antennas. Furthermore, as the electrons oscillate, they create an electromagnetic wave atop the graphene layer, referred to as the surface plasmon polariton wave. This would enable the antenna to operate at the lower end of the terahertz frequency, which would be more efficient than the current copper based antennas. Ultimately, researchers envision that graphene will be able to break through the limitations of current antennas. [8] [9]
It has been estimated that speeds of up to terabits per second can be achieved using such a device. [10] Traditional antennas would require very high frequencies to operate at nano scales, making it an unfeasible option. However, the unique slower movement of electrons in graphene would enable it to operate at lower frequencies making it a feasible option for a nano sized antenna. [9] [11] [12]
Researchers from the Department of Energy’s Oak Ridge National Laboratory (ORNL) have discovered a unique way to create an atomic antenna. Two sheets of graphene can be connected by a silicon wire that is approximately 0.1 nanometer in diameter. This is approximately 100 times smaller than current metal based wires, which can only be reduced to 50 nanometers. This silicon wire however, is a plasmotic device, which would enable the formation of surface plasmon polariton waves required to operate this nano antenna. [12]
Samsung has funded $120,000 for research into the graphene antenna to a team of researchers from the Georgia Institute of Technology and the Polytechnic University of Catalonia. Their research has shown that graphene is a feasible material to make nano antennas with. They have simulated how the electrons would behave, and have confirmed that surface plasmon polariton waves should form. This wave is essential for the graphene antenna to operate at the low end of the terahertz range, making it more efficient than traditional antenna designs. Researchers are currently working on implementing their research, and finding a way to propagate the electromagnetic waves necessary to operate the antenna. Their findings were published in the IEEE Journal on Selected Areas in Communications. [11] [13]
A collaboration between the University of Manchester and an industrial partner developed a new way to manufacture graphene antennas for radio-frequency identification. [14] The antennas are paper-based, flexible and environmentally friendly. Their findings were published in Applied Physics Letters [15] and are being commercialised by Graphene Security. [16]
In physics, a plasmon is a quantum of plasma oscillation. Just as light consists of photons, the plasma oscillation consists of plasmons. The plasmon can be considered as a quasiparticle since it arises from the quantization of plasma oscillations, just like phonons are quantizations of mechanical vibrations. Thus, plasmons are collective oscillations of the free electron gas density. For example, at optical frequencies, plasmons can couple with a photon to create another quasiparticle called a plasmon polariton.
Terahertz radiation – also known as submillimeter radiation, terahertz waves, tremendously high frequency (THF), T-rays, T-waves, T-light, T-lux or THz – consists of electromagnetic waves within the International Telecommunication Union-designated band of frequencies from 0.3 to 3 terahertz (THz), although the upper boundary is somewhat arbitrary and is considered by some sources as 30 THz. One terahertz is 1012 Hz or 1,000 GHz. Wavelengths of radiation in the terahertz band correspondingly range from 1 mm to 0.1 mm = 100 μm. Because terahertz radiation begins at a wavelength of around 1 millimeter and proceeds into shorter wavelengths, it is sometimes known as the submillimeter band, and its radiation as submillimeter waves, especially in astronomy. This band of electromagnetic radiation lies within the transition region between microwave and far infrared, and can be regarded as either.
Surface plasmon resonance (SPR) is a phenomenon that occurs where electrons in a thin metal sheet become excited by light that is directed to the sheet with a particular angle of incidence, and then travel parallel to the sheet. Assuming a constant light source wavelength and that the metal sheet is thin, the angle of incidence that triggers SPR is related to the refractive index of the material and even a small change in the refractive index will cause SPR to not be observed. This makes SPR a possible technique for detecting particular substances (analytes) and SPR biosensors have been developed to detect various important biomarkers.
Phaedon Avouris is a Greek chemical physicist and materials scientist. He is an IBM Fellow and was formerly the group leader for Nanometer Scale Science and Technology at the Thomas J. Watson Research Center in Yorktown Heights, New York. His group did early work on carbon nanotubes, including making the first nanotube transistors.
Nanophotonics or nano-optics is the study of the behavior of light on the nanometer scale, and of the interaction of nanometer-scale objects with light. It is a branch of optics, optical engineering, electrical engineering, and nanotechnology. It often involves dielectric structures such as nanoantennas, or metallic components, which can transport and focus light via surface plasmon polaritons.
Extraordinary optical transmission (EOT) is the phenomenon of greatly enhanced transmission of light through a subwavelength aperture in an otherwise opaque metallic film which has been patterned with a regularly repeating periodic structure. Generally when light of a certain wavelength falls on a subwavelength aperture, it is diffracted isotropically in all directions evenly, with minimal far-field transmission. This is the understanding from classical aperture theory as described by Bethe. In EOT however, the regularly repeating structure enables much higher transmission efficiency to occur, up to several orders of magnitude greater than that predicted by classical aperture theory. It was first described in 1998.
Surface plasmons (SPs) are coherent delocalized electron oscillations that exist at the interface between any two materials where the real part of the dielectric function changes sign across the interface. SPs have lower energy than bulk plasmons which quantise the longitudinal electron oscillations about positive ion cores within the bulk of an electron gas.
Plasmonic nanolithography is a nanolithographic process that utilizes surface plasmon excitations such as surface plasmon polaritons (SPPs) to fabricate nanoscale structures. SPPs, which are surface waves that propagate in between planar dielectric-metal layers in the optical regime, can bypass the diffraction limit on the optical resolution that acts as a bottleneck for conventional photolithography.
An optical rectenna is a rectenna that works with visible or infrared light. A rectenna is a circuit containing an antenna and a diode, which turns electromagnetic waves into direct current electricity. While rectennas have long been used for radio waves or microwaves, an optical rectenna would operate the same way but with infrared or visible light, turning it into electricity.
A plasmonic-enhanced solar cell, commonly referred to simply as plasmonic solar cell, is a type of solar cell that converts light into electricity with the assistance of plasmons, but where the photovoltaic effect occurs in another material.
A metamaterial absorber is a type of metamaterial intended to efficiently absorb electromagnetic radiation such as light. Furthermore, metamaterials are an advance in materials science. Hence, those metamaterials that are designed to be absorbers offer benefits over conventional absorbers such as further miniaturization, wider adaptability, and increased effectiveness. Intended applications for the metamaterial absorber include emitters, photodetectors, sensors, spatial light modulators, infrared camouflage, wireless communication, and use in solar photovoltaics and thermophotovoltaics.
Surface plasmon polaritons (SPPs) are electromagnetic waves that travel along a metal–dielectric or metal–air interface, practically in the infrared or visible-frequency. The term "surface plasmon polariton" explains that the wave involves both charge motion in the metal and electromagnetic waves in the air or dielectric ("polariton").
A plasmonic metamaterial is a metamaterial that uses surface plasmons to achieve optical properties not seen in nature. Plasmons are produced from the interaction of light with metal-dielectric materials. Under specific conditions, the incident light couples with the surface plasmons to create self-sustaining, propagating electromagnetic waves known as surface plasmon polaritons (SPPs). Once launched, the SPPs ripple along the metal-dielectric interface. Compared with the incident light, the SPPs can be much shorter in wavelength.
Plasmonic nanoparticles are particles whose electron density can couple with electromagnetic radiation of wavelengths that are far larger than the particle due to the nature of the dielectric-metal interface between the medium and the particles: unlike in a pure metal where there is a maximum limit on what size wavelength can be effectively coupled based on the material size.
Potential graphene applications include lightweight, thin, and flexible electric/photonics circuits, solar cells, and various medical, chemical and industrial processes enhanced or enabled by the use of new graphene materials, and favoured by massive cost decreases in graphene production.
Plasmonics or nanoplasmonics refers to the generation, detection, and manipulation of signals at optical frequencies along metal-dielectric interfaces in the nanometer scale. Inspired by photonics, plasmonics follows the trend of miniaturizing optical devices, and finds applications in sensing, microscopy, optical communications, and bio-photonics.
An electromagnetic metasurface refers to a kind of artificial sheet material with sub-wavelength features. Metasurfaces can be either structured or unstructured with subwavelength-scaled patterns.
Graphene is a 2D nanosheet with atomic thin thickness in terms of 0.34 nm. Due to the ultrathin thickness, graphene showed many properties that are quite different from their bulk graphite counterparts. The most prominent advantages are known to be their high electron mobility and high mechanical strengths. Thus, it exhibits potential for applications in optics and electronics especially for the development of wearable devices as flexible substrates. More importantly, the optical absorption rate of graphene is 2.3% in the visible and near-infrared region. This broadband absorption characteristic also attracted great attention of the research community to exploit the graphene-based photodetectors/modulators.
Spoof surface plasmons, also known as spoof surface plasmon polaritons and designer surface plasmons, are surface electromagnetic waves in microwave and terahertz regimes that propagate along planar interfaces with sign-changing permittivities. Spoof surface plasmons are a type of surface plasmon polariton, which ordinarily propagate along metal and dielectric interfaces in infrared and visible frequencies. Since surface plasmon polaritons cannot exist naturally in microwave and terahertz frequencies due to dispersion properties of metals, spoof surface plasmons necessitate the use of artificially-engineered metamaterials.
Jaime Gómez Rivas is a Spanish physicist and an academic. He is a professor at Eindhoven University of Technology.