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OPTICAL NANOANTENNA1CONTENTSINTRODUCTIONDIFFERENCE BETWEEN RF AND NANOANTENNAHISTORY OF NANOANTENNATHEORY OF OPERATIONSTRUCTUREPRODUCTIONADVANTAGES OF USING NANOANTENNAAPPLICATIONSLIMITATIONSCONCLUSIONREFERENCES2INTRODUCTIONAn antenna is a part of a system designed totransmmit or receive electromagnetic waves. This device is able to convert the radiation energy ofthe propagating wave into localized energy andvice versa.Optical nanoantennas are important devices forconverting propagating radiation into confined orenhanced fields at nanoscale.3DIFFERENCE BETWEEN RF AND OPTICAL NANOANTENNARF antennas have feature size of the order of several centimeters whereas optical antennas with that of order of a few hundred nanometers.4

RF AntennaOptical nanoantenna4In RF antenna conduction phenomena dominates.However, in optical nanoantenna conductivity is lower and polarisation and displacement plays important role.

Unlike RF antennas, optical antennas need specific design for each application5HISTORY OF NANOANTENNA1973 : Robert Bailey and James C. Fletcher, received a patent for an electromagnetic wave converter similar to modern nanoantenna.

1984 : Alvin M. Marks received a patent for a device stating the use of sub-micron antennas for the direct conversion of light power to electrical power.

61996 : Guang H. Lin reported resonant light absorption by a fabricated nanostructure and rectification of light with frequencies in the visible range. 2002 : ITN Energy Systems Inc. published a report on their work on optical antennas coupled with high frequency diodes7THEORY OF OPERATIONProduction of standing-wave electrical current in the finite antenna array structure by incident electromagnetic radiation . Absorption of the incoming EM radiation energy at the designed resonant frequency of the antenna. Generation of cyclic plasma movement of free electrons from the metal antenna. Free flow of electrons along the antenna generating alternating current at the same frequency as the resonance. Current flows towards the antenna feedpoint. In a balanced antenna, the feedpoint is located at the point of lowest impedance.

8Flow of THz currents to feedpoint of antenna9

FIGURE SHOWING STRUCTURE OF ANTENNA10 Ground plane - reflector Dielectric resonance layer AntennaANTENNA STRUCTUREThree main parts :AntennaGround planeOptical resonance cavity Antenna-absorbs the electromagnetic wave, the ground plane acts to, and the optical resonance cavity

Ground plane-reflects the light back towards the antenna

Optical resonance cavity- bends and concentrates the light back towards the antenna via the ground plane.



Figure showing lithography processROLL-TO-ROLL MANUFACTURINGBased on a master patternIt mechanically stamps the precision pattern onto an inexpensive flexible substrate Creates the metallic loop elements Idaho National Laboratories fabricated a master template (10 billion antenna elements on 8-inch round silicon wafer)


Electron microscope image of master templateADVANTAGES OF USING NANOANTENNAHigh theoretical efficiency(greater than 85%)

Nanoantenna arrays can be designed to absorb any frequency of light

By varying the size of the nanoantenna, the resonant frequency of the nanoantenna can be engineered to absorb a specific wavelength of light14APPLICATIONSRealization of compact optical sensors

Designing of integrated optical switches and memories at the nanoscale

Designing of nanolasers

In solar cells and photomixers

15LIMITATIONSProduction : -Slow and expensive electron beam lithography -Parallel processing is not possible with e-beam lithographyOperational frequency : -High frequency light in ideal range of wavelength makes the use of Schottky diodes impractical - MIM diodes need more advances to operate efficiently at higher frequencies16CONCLUSIONIn spite of some of its limitations, opticalnanoantenna has come up with many advantages and applications and with a promising future scope also. Future work will focus on designing the nanoantenna structure for operation in other wavelengths.17REFERENCESAndrea Al and Nader Engheta, Theory, Modeling and Features of Optical Nanoantennas, Antennas and propagation,vol. 61,pp. 1508-1517,2013

P. Muhlschlegel,H. J.Eisler, O. J. F. Martin, B. Hecht, andD.W. Pohl,Resonant optical antennas, Science, vol. 308, pp. 16071609, 2005.

P. Bharadwaj, B. Deutsch, and L. Novotny, Optical antennas, Adv.Opt. Photon., vol. 1, pp. 438483, 2009.