05-09-2014, 10:08 AM
PLASMONICS
[attachment=67649]
ABSTRACT
Optical fibers now span the globe, guiding light signals that convey voluminous streams of
voice communications and vast amounts of data.Hence the drive towards highly integrated
optical devices and circuits for use in high-speed communication technologies and in future
all-optical photonic chips has generated considerable interest in the unique properties of
surface plasmon polaritons (SPP). SPP are electromagnetic waves that are confined to the
interface between materials with dielectric constants of opposite sign. This confinement of
the SPP field to the interface opens the possibility of overcoming the diffraction limit
encountered in classical optics and of realizing planar nanoscale, highly integrated optical
devices.
In our presentation we will discuss a new approach for generating intense nano-scale SPP
spots. The constructive interference of SPPs launched by nanometric holes allows focusing
SPP into an intense sub-wavelength spot of 380 nm width. Near-field scanning optical
microscopy is used to image the local SPP fields. The resulting SPP intensity patterns are
accurately described in calculations based on dipolar SPP sources at each hole as well as on
Finite-Difference Time-Domain simulations. The combination of a focusing array and
nano-wave guide may serve a basic element in planar nano-photonic circuits. Possible
applications to surface-enhanced optical sensing of molecular species will
INTRODUCTION
Plasma is a medium with equal concentration of positive and negative charges, of which
at least one charge type is mobile. With the increasing quest for transporting large
amounts of data at a fast speed along with miniaturization both electronics and photonics
are facing limitations.In physics, the plasmon is the quasiparticle resulting from the
quantization of plasma oscillations just as photons and phonons are quantizations of light
and sound waves, respectively. Thus, plasmons are collective oscillations of the free
electron gas density, often at optical frequencies. They can also couple with a photon to
create a third quasiparticle called a plasma polariton Scientists are now more inclined
from Photonics to Plasmonics. It opens the new era in optical communication.
WHY A NEW TECHNOLOGY?
Optical fibers now span the globe, guiding light signals that convey voluminous streams
of voice communications and vast amounts of data. This gargantuan capacity has led
some researchers to prophesy that photonic devices--which channel and manipulate
visible light and other electromagnetic waves--could someday replace electronic circuits
in microprocessors and other computer chips. Unfortunately, the size and performance of
photonic devices are constrained by the diffraction limit; because of interference between
closely spaced light waves, the width of an optical fiber carrying them must be at least
half the light's wavelength inside the material. For chip-based optical signals, which will
most likely employ near-infrared wavelengths of about 1,500 nanometers (billionths of a
meter), the minimum width is much larger than the smallest electronic devices currently
in use; some transistors in silicon integrated circuits, for instance, have features smaller
than 100 nanometers.
Recently, however, scientists have been working on a new technique for transmitting
optical signals through minuscule nanoscale structures. In the 1980s researchers
experimentally confirmed that directing light waves at the interface between a metal and
a dielectric (a nonconductive material such as air or glass) can, under the right
circumstances, induce a resonant interaction between the waves and the mobile electrons
at the surface of the metal. (In a conductive metal, the electrons are not strongly attached
to individual atoms or molecules.) In other words, the oscillations of electrons at the
surface match those of the electromagnetic field outside the metal. The result is the
generation of surface plasmons--density waves of electrons that propagate along the
interface like the ripples that spread across the surface of a pond after you throw a stone
into the water.
PLASMONIC LED :
Plasmonic materials may also revolutionize the lighting industry by making LEDs bright
enough to compete with incandescent bulbs. Beginning in the 1980s, researchers
recognized that the plasmonic enhancement of the electric field at the metal-dielectric
boundary could increase the emission rate of luminescent dyes placed near the metal's
surface. More recently, it has become evident that this type of field enhancement can also
dramatically raise the emission rates of Quantum dots and quantum wells--tiny
semiconductor structures that absorb and emit light--thus increasing the efficiency and
brightness of solid-state LEDs. It is demonstrated that coating the surface of a gallium
nitride LED with dense arrays of plasmonic nanoparticles (made of silver, gold or
aluminum) could increase the intensity of the emitted light 14-fold.
Furthermore, plasmonic nanoparticles may enable researchers to develop LEDs made of
silicon. Such devices, which would be much cheaper than conventional LEDs composed
of gallium nitride or gallium arsenide, are currently held back by their low rates of light
emission. It is found that coupling silver or gold plasmonic nanostructures to silicon
quantum-dot arrays could boost their light emission by about 10 times. Moreover, it is
possible to tune the frequency of the enhanced emissions by adjusting the dimensions of
the nanoparticle. Careful tuning of the plasmonic resonance frequency and precise control
of the separation between the metallic particles and the semiconductor materials may
enable us to increase radiative rates more than 100-fold, allowing silicon LEDs to shine
just as brightly as traditional devices.
CONCLUSION:
The ideas of Plasmonics illustrate the rich array of optical properties that inspire
researchers in this field. By studying the elaborate interplay between electromagnetic
waves and free electrons, investigators have identified new possibilities for transmitting
data in our integrated circuits, illuminating our homes and fighting cancer. Further
exploration of these intriguing plasmonic phenomena may yield even more exciting
discoveries and inventions interactions between electromagnetic waves and matter. That
includes laser-plasma and laser-solid interactions, nano-photonics, and plasmonics. The
future challenge may be (a) developing high-gradient accelerators of charged particles
(table-top colliders!), and (b) designing novel nanostructures that will contribute to
nanoscale optical imaging and spectroscopy of chemicals and biomolecules
[attachment=67649]
ABSTRACT
Optical fibers now span the globe, guiding light signals that convey voluminous streams of
voice communications and vast amounts of data.Hence the drive towards highly integrated
optical devices and circuits for use in high-speed communication technologies and in future
all-optical photonic chips has generated considerable interest in the unique properties of
surface plasmon polaritons (SPP). SPP are electromagnetic waves that are confined to the
interface between materials with dielectric constants of opposite sign. This confinement of
the SPP field to the interface opens the possibility of overcoming the diffraction limit
encountered in classical optics and of realizing planar nanoscale, highly integrated optical
devices.
In our presentation we will discuss a new approach for generating intense nano-scale SPP
spots. The constructive interference of SPPs launched by nanometric holes allows focusing
SPP into an intense sub-wavelength spot of 380 nm width. Near-field scanning optical
microscopy is used to image the local SPP fields. The resulting SPP intensity patterns are
accurately described in calculations based on dipolar SPP sources at each hole as well as on
Finite-Difference Time-Domain simulations. The combination of a focusing array and
nano-wave guide may serve a basic element in planar nano-photonic circuits. Possible
applications to surface-enhanced optical sensing of molecular species will
INTRODUCTION
Plasma is a medium with equal concentration of positive and negative charges, of which
at least one charge type is mobile. With the increasing quest for transporting large
amounts of data at a fast speed along with miniaturization both electronics and photonics
are facing limitations.In physics, the plasmon is the quasiparticle resulting from the
quantization of plasma oscillations just as photons and phonons are quantizations of light
and sound waves, respectively. Thus, plasmons are collective oscillations of the free
electron gas density, often at optical frequencies. They can also couple with a photon to
create a third quasiparticle called a plasma polariton Scientists are now more inclined
from Photonics to Plasmonics. It opens the new era in optical communication.
WHY A NEW TECHNOLOGY?
Optical fibers now span the globe, guiding light signals that convey voluminous streams
of voice communications and vast amounts of data. This gargantuan capacity has led
some researchers to prophesy that photonic devices--which channel and manipulate
visible light and other electromagnetic waves--could someday replace electronic circuits
in microprocessors and other computer chips. Unfortunately, the size and performance of
photonic devices are constrained by the diffraction limit; because of interference between
closely spaced light waves, the width of an optical fiber carrying them must be at least
half the light's wavelength inside the material. For chip-based optical signals, which will
most likely employ near-infrared wavelengths of about 1,500 nanometers (billionths of a
meter), the minimum width is much larger than the smallest electronic devices currently
in use; some transistors in silicon integrated circuits, for instance, have features smaller
than 100 nanometers.
Recently, however, scientists have been working on a new technique for transmitting
optical signals through minuscule nanoscale structures. In the 1980s researchers
experimentally confirmed that directing light waves at the interface between a metal and
a dielectric (a nonconductive material such as air or glass) can, under the right
circumstances, induce a resonant interaction between the waves and the mobile electrons
at the surface of the metal. (In a conductive metal, the electrons are not strongly attached
to individual atoms or molecules.) In other words, the oscillations of electrons at the
surface match those of the electromagnetic field outside the metal. The result is the
generation of surface plasmons--density waves of electrons that propagate along the
interface like the ripples that spread across the surface of a pond after you throw a stone
into the water.
PLASMONIC LED :
Plasmonic materials may also revolutionize the lighting industry by making LEDs bright
enough to compete with incandescent bulbs. Beginning in the 1980s, researchers
recognized that the plasmonic enhancement of the electric field at the metal-dielectric
boundary could increase the emission rate of luminescent dyes placed near the metal's
surface. More recently, it has become evident that this type of field enhancement can also
dramatically raise the emission rates of Quantum dots and quantum wells--tiny
semiconductor structures that absorb and emit light--thus increasing the efficiency and
brightness of solid-state LEDs. It is demonstrated that coating the surface of a gallium
nitride LED with dense arrays of plasmonic nanoparticles (made of silver, gold or
aluminum) could increase the intensity of the emitted light 14-fold.
Furthermore, plasmonic nanoparticles may enable researchers to develop LEDs made of
silicon. Such devices, which would be much cheaper than conventional LEDs composed
of gallium nitride or gallium arsenide, are currently held back by their low rates of light
emission. It is found that coupling silver or gold plasmonic nanostructures to silicon
quantum-dot arrays could boost their light emission by about 10 times. Moreover, it is
possible to tune the frequency of the enhanced emissions by adjusting the dimensions of
the nanoparticle. Careful tuning of the plasmonic resonance frequency and precise control
of the separation between the metallic particles and the semiconductor materials may
enable us to increase radiative rates more than 100-fold, allowing silicon LEDs to shine
just as brightly as traditional devices.
CONCLUSION:
The ideas of Plasmonics illustrate the rich array of optical properties that inspire
researchers in this field. By studying the elaborate interplay between electromagnetic
waves and free electrons, investigators have identified new possibilities for transmitting
data in our integrated circuits, illuminating our homes and fighting cancer. Further
exploration of these intriguing plasmonic phenomena may yield even more exciting
discoveries and inventions interactions between electromagnetic waves and matter. That
includes laser-plasma and laser-solid interactions, nano-photonics, and plasmonics. The
future challenge may be (a) developing high-gradient accelerators of charged particles
(table-top colliders!), and (b) designing novel nanostructures that will contribute to
nanoscale optical imaging and spectroscopy of chemicals and biomolecules