Department of Electronics & Communication EngineeringTechnical seminar presentation on: Submitted by: RITESH KUMAR NAYAK (Mob:09482137706) (USN:1AT09EC068) Under the guidance of HARSHA K Lecturer, Dept. of E&C A.I.T Content overview: 1. Why Nantenna ? 2. Introduction to Nantenna. 3. Theory or Nantenna. 4. Theory of operation. 5. Analytical model (RLC Model). 6. Manufacturing of Nantenna. 7. Benefits and applications. 8. Limitations of nantennas. 9. Future research and goals. 10. References “The Infinite Power of the Sun” Single day provides enough energy for 27 years {~ 127.518*10^15 W (127 PW) sun energy strikes earth/1hour.} ~30% Reflected ~19% Absorbed Atmosphere ~51% Absorbed by Earth CURRENT TECHNOLOGY : Photovoltaic Technology. Photon DC CURRENT electron–hole pairs LIMITATIONS OF PV TECHNOLOGY : • • • • • • Band gap (heat loss, reduces efficiency) Expensive for large scale (multi junction) manufacturing PV is operational only during daylight hours. Delivers DC power Low efficiency Requires direct incidence(perpendicular to surface) of solar radiation for optimum efficiency. INTRODUCTION TO NANTENNA: A nantenna (nano antenna) is a nanoscopic rectifying antenna. Nantennas are used for converting solar radiation to electricity. Based on antenna theory, a nantenna is a EM collector that can absorb any wavelength of light efficiently provided that the size of the nantenna is optimized for that specific wavelength. Ideally, nantennas would be used to absorb light at wavelengths between 0.4–1.6 μm because these wavelengths have high energy and make up about 85% of the solar radiation spectrum. DIFFERENT TYPES OF NANTENNA: ( Single loop metal Nantenna ) ( Array of loop Nantenna ) ( Bow-tie Nantenna ) ( Array of bow-tie Nantenna ) THEORY OF NANTENNAS: The incident light causes electrons in the nantenna to move back and forth at the same frequency as the incoming light. This is caused by the oscillating electric field of the incoming EM wave. The movement of electrons causes an alternating current in the nantenna circuit. THEORY OF OPERATION • Light propagates as an EM wave at certain frequency. • Captured by a Nanoantenna • Absorption occurs at Nantenna resonance frequency. • Induces a back and forth movement of free electrons in Nantenna. • THz current flows toward Nantenna feed-point. • This provides a convenience point to collect and transport energy to other circuitry for conversion (AC to DC). • Diode is embedded in feed-point to rectify signal. The NECs can be configured as FSS (frequency selective surfaces) to efficiently absorb the entire solar spectrum. Nantenna capture electromagnetic energy from naturally occurring solar radiation and thermal earth radiation. Rather than generating single electron-hole pairs as in the PV, the incoming EM field induces a time-changing current in the Nantenna. To convert this AC into direct current, the AC is rectified using diode. The resulting DC current can then be used to power any external load. ANALYTICAL MODEL – RLC CIRCUIT: ( Square FSS element and its RLC circuit analog ) The metal loops give inductance to the NEC as thermallyexcited radiation induces current. The gaps between the metallic loops and the gap within the loop compose capacitors with a dielectric fill. A resistance is present because the antenna is composed of lossy metallic elements on a dielectric substrate. The resulting RLC circuit has a resonance “tuned” filter behaviour. COMPONENTS OF A NANTENNA: The nantenna consists of three main parts: 1.The ground plane 2.The optical resonance cavity 3.The antenna. Antenna Dielectric resonance cavity layer Ground plane - reflector WHY THIS STRUCTURE ??? : The antenna absorbs the EM wave, the ground plane acts to reflect the light back towards the antenna, and the optical resonance cavity bends and concentrates the light back towards the antenna via the ground plane. The NEC-to-ground plane separation (cavity) acts as a transmission line that enhances resonance. The thickness of the standoff layer is selected to be a ¼ wavelength to insure better efficiency. ( path of incident wave ) MANUFACTURING OF NANTENNA: LITHOGRAPHY & R2R: 1. LITHOGRAPHY (laboratory processing, small scale ) 2. R2R (master pattern, large scale ) LARGE-SCALE MANUFACTURED SAMPLES: SEM image of polymer replicas made from wafer master template Flexible Structures BENEFITS AND APPLICATIONS • Addresses many limitations of PVs. • Utilize untapped infrared parts of spectrum (Solar radiation & Thermal earth radiation) • Can be inexpensively mass produced. •DNA Nanoantenna & Cancer Fighting Lasers. Many Diverse Applications : • Nanoantenna “skins” e.g. self-charging AA battery design,car,laptop. • Economically scales to large infrastructure (homes, businesses) LIMITATIONS OF NANTENNAS: One of the major limitations of nantennas is the frequency at which they operate. The high frequency of light makes the use of typical Schottky diodes impractical i.e. more advanced diodes are necessary to operate efficiently at higher frequencies. Current nantennas are produced using electron beam (ebeam) lithography. This process is slow and relatively expensive because parallel processing is not possible with ebeam lithography. (Can be eliminated by roll-to-roll manufacturing method.) FUTURE RESEARCH AND GOALS: A rectifier must be designed that can properly turn the absorbed light into usable energy. Researchers currently hope to create a rectifier which can convert around 50% of the nantenna's absorption into energy. Nantenna could be designed to work by absorbing the infrared heat available in the room and producing electricity which could be used to further cool the room. Another focus of research will be how to properly upscale the process to mass-production. New materials will need to be chosen and tested that could be used with a roll-to-roll manufacturing process. REFERENCES: [1] A. Csaki, F. Garwe, A. Steinbruck, A. Weise, K. Konig, and W. Fritzsche, "Localization of laser energy conversion by metal nanoparticles basic effects and applications - art. No.61911K," in Biophotonics and New Therapy Frontiers, vol. 6191, SPIE , 2006, pp. K1911-K1911. [2] Alda, J. Rico-García, J. López-Alonso,and G. Boreman, "Optical antennas for nano-photonic applications," Nanotechnology, vol. 16, pp. S230-4, 2005 [3]Ansoft High Frequency Structure Simulator v10 User‟s Guide, Ansoft Corporation, (2005) [4] B. A. Munk, “Frequency Selective Surfaces: Theory and Design”. NewYork: Wiley, 2000, pp. 2–23. [5] B. Monacelli, J. Pryor, B. Munk, D. Kotter, G. Boreman, “Infrared Frequency Selective Surfaces: Square loop versus Square-Slot Element Comparison” AP0508-0657, Aug 2005 [6] Guy J. Consolmagno and Martha W. Schaefer, World„s Apart: A Textbook in Planetary Sciences (1994) Englewood Cliffs, NJ: Prentice Hall. EXTRA THz CURRENT EXTRA ( Flow of THz currents to feed point of antenna. Red represents highest concentrated E field ) The e-field is clearly concentrated at the center feed-point. This provides a convenience point to collect energy and transport it to other circuitry for conversion. Typical electromagnetic radiation patterns of antenna Design Overview • Initial design of Nantennna was based on scaling of radio frequency antenna theory • Analytical model – RLC Circuit derived • Nantenna consists of an antenna layer, a dielectric resonance layer, and a optical reflector/ground plane • Physical geometry tunes antenna and spectral response Antenna & RLC Dielectric resonance layer Ground plane - reflector Nantenna Structure Energy gap (eV) Material Si Ge 0K 1.17 0.74 300K 1.11 0.66 InSb InAs InP GaP GaAs GaSb CdSe CdTe ZnO ZnS 0.23 0.43 1.42 2.32 1.52 0.81 1.84 1.61 3.44 3.91 0.17 0.36 1.27 2.25 1.43 0.68 1.74 1.44 3.2 3.6 Average instantaneous power emitted by the Sun = 3.8 x 1023 kW Solar energy per year = 3.33108 x 1027 kWh/year Volume of Earth‟s electrical consumption (2008) = 143,851 TWh/year Solar power hitting Earth‟s atmosphere = 1,366 W/m2 Percentage of power reaching Earth‟s surface = 18% Solar power hitting Earth‟s surface = 250,000,000 W/km2 Earth‟s surface area = 510,072,000 km2 Total average solar power hitting Earth = 127.518*10^15W Hours per year = 8,766 h/y Total solar energy hitting Earth per year = 1,117,822,788 TWh/year Bio-Inspired Nanoantennas For Light Emission Just as radio antennas amplify the signals of our mobile phones and televisions, the same principle can apply to light. For the first time, researchers from CNRS and Aix Marseille Université have succeeded in producing a nanoantenna from short strands of DNA, two gold nanoparticles and a small fluorescent molecule that captures and emits light. This easy-to-handle optical antenna is described in an article published in Nature Communications on 17 July 2012. This work could in the longer term lead to the development of more efficient lightemitting diodes, more compact solar cells or even be used in quantum cryptography. Schematic representation of a nanoantenna formed of two gold nanoparticles linked by a DNA double strand and supplied by a single quantum emitter Since light is a wave, it should be possible to develop optical antennas capable of amplifying light signals in the same way as our televisions and mobile phones capture radio waves. However, since light oscillates a million times faster than radio waves, extremely small nanometer (nm) sized objects are needed to capture such very rapid light waves. Consequently, the optical equivalent of an elementary antenna (of dipole type) is a quantum emitter surrounded by two particles a thousand times smaller than a human hair. For the first time, researchers from the Langevin and Fresnel1 Institutes have developed such a bio-inspired light nanoantenna, which is simple and easy to handle. They grafted gold particles (36 nm diameter) and a fluorescent organic colorant onto short synthetic DNA strands (10 to 15 nm long). The fluorescent molecule acts as a quantum source, supplying the antenna with photons, while the gold nanoparticles amplify the interaction between the emitter and the light. The scientists produced in parallel several billion copies of these pairs of particles (in solution) by controlling the position of the fluorescent molecule with nanometric precision, thanks to the DNA backbone. These characteristics go well beyond the possibilities offered by conventional lithography techniques currently used in the design of microprocessors. In the longer term, such miniaturization could allow the development of more efficient LEDs, faster detectors and more compact solar cells. These nanosources of light could also be used in quantum cryptography
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