The Lycurgus Cup, which is kept in

London museum, is a 4th-

century Roman glass cage cup made of

a dichroic glass, which shows a

different color.

What is the basic

reason behind it?

What is Plasmons?

• When the light incidents on the metal

surface, under ideal conditions, it emits

the waves which have certain density,

known as Plasmons.

• A Plasmon is a collective oscillation of

the conduction electrons.

Plasmons can be described in the classical picture

as an oscillation of free electron density with

respect to the fixed positive ions in a metal. To

visualize a plasma oscillation, imagine a cube of

metal placed in an external electric field pointing to

the right.

Electrons will move to the left side (uncovering positive ions on the right side) until

they cancel the field inside the metal.

If the electric field is removed, the electrons move to the right, repelled by each other

and attracted to the positive ions left bare on the right side.

They oscillate back and forth at the plasma frequency until then energy is lost in some

kind of resistance or damping. Plasmons are a quantization of this kind of oscillation.

Surface Plasmons• Surface Plasmons (SPs) are coherent electron oscillations that exist at the

interface between any two materials, e.g. a metal-dielectric interface, such as a metal sheet in air.

• SPs have lower energy than bulk (or volume) Plasmons which quantise the longitudinal electron oscillations about positive ion cores within the bulk of an electron gas (or plasma).

Surface Plasma Polariton

The charge motion in a surface Plasmon always

creates electromagnetic fields outside (as well as

inside) the metal. The total excitation, including

both the charge motion and associated

electromagnetic field, is surface Plasmon Polariton.

They are a type of surface wave, guided along the

interface in much the same way that light can be

guided by an optical fiber.

Surface Plasmon polaritons (SPPs),

are infrared or visible-

frequency electromagnetic waves, which travel

along a metal-dielectric or metal-air interface.

The term "surface Plasmon Polariton"

explains that the wave involves both charge

motion in the metal ("surface Plasmon") and

electromagnetic waves in the air or dielectric

("Polariton").

• An SPP will propagate along the interface until its energy is lost

either to absorption in the metal or scattering into other directions

(such as into free space).

Plasmonics SPPs are shorter in wavelength than the incident light (photons).

Hence, SPPs can have tighter spatial confinement and higher local

field intensity.

• The short-wavelength of it (around 70

nm) enables the use of Nano scale

structure, in which light can be guided,

split, filtered, and even amplified.

• So, the information transfer in Nano

scale structures by means of surface

Plasmons, is referred to as Plasmonics.

One more advantage this gives is, by

varying Nano particle shape or

geometry, the SP resonance

frequency can be tuned over a broad

spectral range.

• Nano scale structure is used

because, one way to achieve long

propagation lengths is to use very

thin films.

• In addition to that, Nano particles

show strong optical resonances,

because of their large free-electron

density and ordered arrays of Nano

particles can possess even further

enhanced field intensities which

will aid the Plasmon coupling

between two adjacent particles.

Plasmonic Solar cell:• Total solar energy striking to the earth is 1,20,000 TW.

• The price of soar electricity has decreased by a factor of 5 over the last 20 years

• But solar electricity is still currently about 5 times the cost of coal generated

• 50% of the cost of solar modules is the cost of the silicon wafers (300μm thick). This can be reduced with thin film cells (~2 μm thick).

• Improving the efficiency of photovoltaic cells is one of the great challenges for renewable energy science.

• In the lab, the best cells can convert almost half the sunlight hitting them into electricity (44 per cent) although for the figure commercial cells is less than half that.

One way to improve matters is to

minimize the amount of light reflected

from the cell or transmitted through it,

since this energy is clearly lost.

The conventional approach is to use an

anti-reflection coating. But there’s a

problem.

• While these coatings are good

at preventing reflections, they

cannot stop light being

transmitted.

• In some cases, almost half the

light passes straight through.

Light-trapping in Photovoltaic:

Wafer based cells use light trapping based on

geometrical optics (feature sizes ~10 μm).

Thin film cells require wavelength-scale light

trapping.

One way to achieve this is through excitation of

Surface Plasmons.

Types of Plasmons:

Localized PlasmonsDipole (and multipole)oscillations of electrons

Propagating Plasmons(Surface Plasmon Polaritons)

Both types of Plasmons canbe used to enhanceabsorption in solar cells.

Increased Absorption of light in thin films solar cells

Light incident on metal particles roughly on the scale of the wavelength of light can excite Surface Plasmons which can then scatter light and couple it into the waveguide modes.

Extraction of light from light emitting diodes is also enhanced:

Most emitted light is trapped in the semiconductor layer by total internal reflection. Surface Plasmons can couple the light out of the semiconductor waveguide before it is re-absorbed potentiallyincreasing the efficiency of the LED.

How Light-Trapping Surfaces Will Boost Solar Cell Efficiency:

• The basic principle behind “Plasmons” is very simple. Plasmons will work as Nano-antenna.

• Plasmons will absorb sun-light having specific wavelength.

• While focusing on a different approach– Plasmons captures the incoming light and trapping it against the surface.

• This prevents both reflection and transmission and so has the potential to significantly increase the efficiency of thin film solar cells.

• We have to cover a cell with a regular array of silver Nano-antennas that convert ordinary incoming waves into more exotic ones that propagate through the photovoltaic slab itself.

Plasmons Hologram: 3D without

spectacles!!

The Scientists of Ashoka University said

that the viewers can have the 3d effect at

any angle and they are not required to

have any special spectacles for that.

• They developed 3d hologram using surface

Plasmons.

• They used photo resistive material and Nano

Au layers to produce a hologram.

• With the light incident below the glass sheet,

the Plasmons are activated and excited and

with the use of interference, diffraction,

light intensity recording and suitable

illumination and specific colour wavelengths,

they produced hologram.

Cancer Therapy by gold particles

• This Plasmon technology will bring revolution in

medical field, especially in Cancer treatment.

• A scientist of Rice University successfully

removed the cancer tumour with the help of

Plasmonics.

• A silicon particle is placed into 100 nm golden

particle and is injected into blood which

approaches to the tumour cell.

• This Plasmon particle is heated through infrared

radiation and destroys the cancer tumour.

CMOS chip for sharper image

Plasmonics can also be used to make super sensitive

image sensor which will give sharper pictures. CMOS(

Complementary metal oxide semi-conductor) sensor is

used in digital cameras.

The scientists of Glasgow University, Scotland are

researching on that super sensitive sensor which

consists of Nano structure layer on CMOS to enhance

the quality of digital imaging.

Imaging

drug delivery

bio-molecule ultrasensitive sensing

thermal cell apoptosis

MOREOVER……

REFERENCES:1. http://en.wikipedia.org/wiki/Plasmon

2. RAVIPURTI,GUJARAT SAMACHAR NEWS PAPER 15/12/13

3. M. Hoffert et al., Science 298, 981 (2002).

http://www.sc.doe.gov/bes/reports/files/SEU_rpt.pdf

4. http://daedalus.caltech.edu/publication/pubs/PlasmonPV_nmat_2010.pdf

5. phy.ntnu.edu.tw/~changmc/Teach/SS/SS_note/chap14.pdf

6. Subsequent Science and Nature articles 1999-2007

7. blogs.ls.berkeley.edu/fengwang/files/2009/12/2006-local-plasmons.pdf

8. www.ncbi.nlm.nih.gov/pubmed/17563412

9. www.amazon.com/Surface-plasmons...application/dp/3838128370

10.en.wikipedia.org/wiki/Plasmonic_solar_cel

11.https://gcep.stanford.edu/pdfs/.../SE_Lee_PlasmonicSolarCells.pdf

THANK YOU