NANTENNA

Why nantenna ???“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 CURREN

Telectron–

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.

• 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.

THEORY OF OPERATION

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.

( Square FSS element and its RLC circuit analog )

ANALYTICAL MODEL – RLC CIRCUIT:

The metal loops give inductance to the NEC as thermally-excited 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 plane2.The optical resonance cavity3.The antenna.

Ground plane - reflector

Dielectric resonance cavity layer

Antenna

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 )

WHY THIS STRUCTURE ??? :

MANUFACTURING OF NANTENNA:

SEM cross-section of patterned oxide layer of (prior to DRIE step)

SEM top view of Si wafer after anisotropic oxide etch

LITHOGRAPHY & R2R:

1. LITHOGRAPHY (laboratory processing, small scale )

2. R2R (master pattern, large scale )

Roll to Roll Manufacturing Equipment

Manufacturing Cost:~ $0.50-1.00/ft2

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 (e-beam) lithography. This process is slow and relatively expensive because parallel processing is not possible with e-beam 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)

THANK YOU