Plasmonics: Merging Photonics and
Electronics at Nanoscale Dimensions
Ekmel Ozbay
*
Electronic circuits provide us with the ability to control the transport and storage of electrons.
However, the performance of electronic circuits is now becoming rather limited when digital
information needs to be sent from one point to another. Photonics offers an effective solution
to this problem by implementing optical communication systems based on optical fibers and
photonic circuits. Unfortunately, the micrometer-scale bulky components of photonics have
limited the integration of these components into electronic chips, which are now measured in
nanometers. Surface plasmon–based circuits, which merge electronics and photonics at the
nanoscale, may offer a solution to this size-compatibility problem. Here we review the current
status and future prospects of plasmonics in various applications including plasmonic chips,
light generation, and nanolithography.
T
oday_s state-of-the-art microprocessors
use ultrafast transistors with dimen-
sions on the order of 50 nm. Although
it is now routine to produce fast transistors,
there is a major problem in carrying digital in-
formation to the other end of a microprocessor
that may be a few centimeters away. Whereas
copper wire interconnects carry digital infor-
mation, interconnect scaling has been insuffi-
cient to provide the necessary connections
required by an exponentially growing transis-
tor count. Unlike transistors, for which per-
formance improves with scaling, the delay of
interconnects increases and becomes a substan-
tial limitation to the speed of digital circuits
(1). This limitation has become more evident
over the past 1 to 2 years, as the annual in-
crease rate of the clock speed of microproces-
sors slowed greatly.
Optical interconnects such as fiber optic
cables can carry digital data with a capacity
91000 times that of electronic interconnects.
Unfortunately, fiber optic cables are È1000
times larger compared with electronic com-
ponents, and the two technologies are diffi-
cult to combine on the same circuit. External
optical interconnects that can connect differ-
ent parts of the electronic chips via air or fiber
cables have also been proposed. However, the
resulting bulky configuration has limited the
implementation of this idea. The ideal solution
would be to have a circuit with nanoscale fea-
tures that can carry optical signals and electric
currents. One such proposal is surface plasmons,
which are electromagnetic waves that propagate
along the surface of a conductor. The interac-
tion of light with matter in nanostructured
metallic structures has led to a new branch of
photonics called plasmonics. Plasmonic circuits
offer the potential to carry optical signals and
electric currents through the same thin metal
circuitry, thereby creating the ability to com-
bine the superior technical advantages of pho-
tonics and electronics on the same chip.
Plasmonic Chips: Light on a Wire
What limits the integration of optical and elec-
tronic circuits most is their respective sizes.
Electronic circuits can be fabricated at di-
mensions below 100 nm. On the other hand,
the wavelength of light used in photonics cir-
cuits is on the order of 1000 nm. When the
dimensions of an optical component become
close to the wavelength of light, the propaga-
tion of light is obstructed by optical diffrac-
tion (2), which therefore limits the minimum
size of optical structures including lenses, fi-
bers, and optical integrated circuits. Although
the introduction of photonic crystals brings a
partial solution to these problems, the pho-
tonic crystal itself has to be several wave-
lengths long, because the typical period is on
the order of half of a wavelength (3).
Surface plasmon–based photonics, or ‘‘plas-
monics,’’ may offer a solution to this dilemma,
because plasmonics has both the capacity of
photonics and the miniaturization of electronics.
Surface plasmons (SPs) provide the opportunity
to confine light to very small dimensions. SPs
are light waves that occur at a metal/dielectric
interface, where a group of electrons is collect-
ively moving back and forth (4). These waves
are trapped near the surface as they interact
with the plasma of electrons near the surface
of the metal. The resonant interaction between
electron-charged oscillations near the surface
of the metal and the electromagnetic field of
the light creates the SP and results in rather
unique properties. SPs are bound to the metallic
surface with exponentia lly decaying fields in
both neighboring media. The decay length of
SPs into the metal is determined by the skin
depth, which can be on the order of 10 nm—two
orders of magnitude smaller than the wavelength
of the light in air. This feature of SPs provides
the possibility of localization and the guiding of
light in subwavelength metallic structures, and it
canbeusedtoconstructminiaturized optoelec-
tronic circuits with subwavelength components
(5). Such plasmonic optoelectronic circuits, or
plasmonic chips, will consist of various compo-
nents such as waveguides, switches, modulators,
and couplers, which can be used to carry the
optical signals to different parts of the circuit.
Plasmonic waveguides are used to guide the
plasmonic signals in these circuits and can be
configured by using various geometries (6).
Thin metal films of finite width embedded in
a dielectric can be used as plasmonic wave-
guides. This geometry offers the best propa-
gation results for a surface plasmon–based
waveguide, because the measured propaga-
tion length for operation with light at a wave-
length of 1550 nm is reported to be as long as
13.6 mm. However, the localization for both
directions is on the order of a few micrometers
in this plasmonic waveguide geometry (7). To
achieve subwavelength localization, one can
reduce the width of the wire an d subsequently
use the SPs to guide the light underneath this
nanowire. In nanowires, the confinement of
the electrons in two dimensions leads to well-
defined dipole surface plasmon resonances, if
the lateral dimensions of the wire are much
smaller than the wavelength of the exiting
light. By using this method, a 200-nm-wide
and 50-nm-high gold nanowire was fabricated.
This plasmonic waveguide was then locally
excited at a light wavelength of 800 nm (8).
By direct imaging of the optical near field
with subwavelength-resolution photon scanning
tunneling microscopy, light transport was ob-
served along the nanowire over a distance of a
few micrometers. Although this is a clear dem-
onstration of subwavelength guiding, the losses
associated with the resistive heating within the
metal limit the maximum propagation length of
light within these structures. In order to avoid
the ohmic losses, one can envision using an
array of nanoparticle resonators. The resonant
structure of the nanoparticles can be used to
guide the light, whereas the reduced metallic
volume means a substantial reduction in ohmic
losses. Stefan Maier and co-workers (9)used
such a structure (Fig. 1A), in which nanoscale
gold dots were patterned on a silicon-on-
insulator wafer to define the plasmon propaga-
tion path. Figure 1B shows scanning electron
micrographs (SEMs) of the fabricated plas-
monics waveguides designed for operation at a
wavelength of 1500 nm. The waveguide struc-
ture is not uniform across its width where the
size of the metal dots is reduced from 80 nm
80 nm at the center to 50 nm 50 nm at the
edges. This has the effect of confining the
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Nanotechnology Research Center, Bilkent University,
Bilkent, Ankara 06800 Turkey.
*To whom correspondence should be addressed. E-mail:
ozbay@bilkent.edu.tr
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energy more intently to the middle of the guide
(Fig. 1A). This structure has been shown to
have a decay length longer than 50 mm, where-
as theoretical simulations predict a decay length
in the order of 500 mm. Figure 1A shows that
although the localization along the x direction is
subwavelength, the localization extends a few
periods along the y direction, which corresponds
to localization on the order of a wavelength.
Therefore, the subwavelength localization of
SPs is limited only to the x direction.
To achieve localization in both directions,
a new type of highly localized plasmon has
been analyzed and experimentally demon-
strated in metals with V-shaped grooves (10).
The major features of plasmons in V grooves
include a combination of strong localization,
single-mode operation, the possibility of nearly
100% transmiss ion through sharp bends, and a
high tolerance to structural imperfections. For
the localization and guiding to occur, the wedge
angle (q) of the V groove should be smaller
than a critical angle. For V grooves made from
silver with a vacuum wavelength of 0.6328 mm,
this critical wedge angle is found to be 102-.
The measured lateral localization of a structure
with a 40- wedge angle is È300 nm, which is
superior to the nanoparticle-based plasmonic
waveguides . However, the reported experimen-
tal and theoretical decay lengths for the same
V groove–shaped plasmonic waveguide are
1.5 mm and 2.25 mm, respectively, which are
obviously too short for any application of these
plasmonic structures. The propagation distance
performance of the V groove–shaped SP wave-
guides has been recently extended to 250 mm
(11). By using focused ion-beam milling tech-
niques, 460-mm-long V groove–shaped plas-
monic waveguides were fabricated on gold
layers that were deposited on a substrate of
fused silica. Scanning near-field optical micro-
scope measurements of these structures were
made at optical communication wavelengths
(1425 to 1620 nm). For a structure with a
0.6-mm-wide and 1.0-mm-deep groove wedge
(corresponding to a È17- wedge angle), the
SP propagation lengths were measured to be
within 90 to 250 mm. The mode was well
confined along the lateral direction, and the
measured mode width was 1.1 mm.
Thus there is a basic trade-off in all plas-
mon waveguide geometries between mode
size and propagation loss. One can have a low
propagation loss at the expense of a large mode
size, or a high propagation loss with highly
confined light. A hybrid approach, where both
plasmonic and dielectric waveguides are used,
has been suggested as a solution to this trade-
off (12). These waveguides are designed for
1500-nm operation and exhibit losses on the
orderof–1.2dB/mm, and they can guide light
around 0.5-mm bends. Light can also be ef-
ficiently coupled between more convention-
al silicon waveguides, where these plasmon
waveguides with compact couplers
and surface plasmon optical devices
can be constructed by using planar
circuit fabrication techniques. Introduc-
ing gain to the plasmonic waveguides
can also bring a solution to the limited
propagation distances. This situation is
theoretically investigated by consider-
ing the propagation of SPs on metallic
waveguides adjacent to a gain medium
(13). The analytic analysis and numeric
simulation results show that the gain
medium assists the SP propagation by
compensating for the metal losses,
making it possible to propagate SPs with
little or no loss on metal boundaries and
guides. The calculated gain requirements suggest
that lossless, gain-assisted surface plasmon prop-
agation can be achieved in practice for infrared
wavelengths.
Recently, a new kind of SP geometry has
been suggested to solve theoretically the issue
of confinement versus propagation length (14).
The new mechanism for confining much more
field in the low-index region rather than in the
adjacent high-index region is based on the rel-
ative dispersive characteristics of different sur-
face plasmon modes that are present in these
structures. The structures have a subwavelength
modal size and very slow group velocity over
an unusually large frequency bandwidth. Sim-
ulations show that the structures exhibit ab-
sorption losses limited only by the intrinsic loss
of the metal. Currently, there is no experimen-
tal data that supports thes e simulations. How-
ever, the new suggested SP structure is quite
promising and deserves attention from the ex-
perimental research groups that are working on
plasmonic waveguides.
Plasmonic chips will have optical input and
output ports, and these ports will be optically
connected to conventional diffraction-limited
photonic devices by plasmonic couplers (8).
The couplers should have high conversion effi-
ciency, along with a transmission length that is
longer than the optical wavelen gth to avoid the
direct coupling of the propagating far-field light
to the nanophotonic devices inside the plasmonic
chip. A promising candidate for this feature
can be fabricated by combining hemispher-
ical metallic nanoparticles that work as a plas-
monic condenser and a nanodot-based plasmonic
waveguide (15). When the focused plasmons
move into the co upler, the transmission length
through the coupler is 4.0 mm. Nanodots can
also be used for focusing SPs into a spot of
high near-field intensity having a subwave-
length width (16). Figure 2A shows the SEM
image of such a sample containi ng 19 200-nm
through-holes arranged on a quarter circle with
a5-mm radius. The SPs originating from these
nanodots are coupled to a metal nanostrip wave-
guide. A near-field scanning optical microsco-
py (NSOM) image of this structure was taken
at 532-nm incident wavelength with horizontal
polarization. The near-field image (Fig. 2B)
shows that the focused SPs propagate along
the subwavelength metal guide, where they par-
tially penetrate into the 100-nm-wide bifurca-
tion at the end of the guide, thus overcoming
the diffraction limit of conventional optics.
The measured propagation distance is limited
to 2 mm, and the propagation distances are
expected to be much longer with improved
fabrication processes and by using pr operly
designed metal-dielectric hybrid structures.
The combination of focusing arrays and nano-
waveguides may serve as a basic element in
planar plasmonic circuits.
Active control of plasmons is needed to
achieve plasmonic modulators and switches.
Fig. 2. (A) SEM image of a nanodot focusing array coupled to a 250-nm-wide Ag strip guide. (B)
NSOM image of the SP intensity showing subwavelength focusing. [Adapted from (15)]
Fig. 1. (A) FDTD simulations show the electric field
produced within the plasmon waveguide structure. (B)A
plasmon waveguide consists of nanoscale gold dots on a
silicon-on-insulator surface. [Adapted from (9)]
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Plasmonic signals in a metal-on-dielectric wave-
guide containing a gallium section a few mi-
crons long can be effectively controlled by
switching the structural phase of gallium (17).
The switching can be achieved by either chang-
ing the waveguide temperature or by external
optical excitation. The signal modulation depth
can exceed 80%, and switching times are
expected to be in the picosecond time scale.
The realization of an active plasmonic device
by combining thin polymer films containing
molecular chromophores with thin silver film has
also been reported (18). The molecular plas-
monic device consists of two polymer layers,
one containing donor chromophore molecules
and the other containing acceptor fluorophore
molecules. Coupled SPs are shown to provide
an effective transfer of excitation energy from
donor molecules to acceptor molecules on op-
posite sides of metal film up to 120 nanometers
thick. The donors absorb incident light and
transfer this excitation energybydipole-dipole
interactions to the acceptors. The acceptors then
emit their characteristic fluorescence. These re-
sults are preliminary demonstrations for active
control of plasmonic propagation, and future
research should focus on the investigation of
electro-optic, all-optical, and piezoelectric mod-
ulation of subwavelength plasmon waveguide
transmission.
Extensive research efforts are being put
forth in order to achieve an all-plasmonic chip.
In the near term, plasmonic interconnects may
be used to address the cap acity problem in
digital circuits including microprocessors. Con-
ventional electronic interconnects may be used
to transfer the digital data among the local
arrays of electronic transistors. But, when a lot
of data need to travel from one section of a
chip to another remote section of the chip,
electronic information could be converted to
plasmonic information, sent along a plasmonic
wire, and converted back to electronic informa-
tion at the destination. Unfortun ately, the cur-
rent performance of plasmonic waveguides is
insufficient for this kind of application, and
there is an urgent need for more work in this
area. If plasmonic c omponents can be suc-
cessfully implemented as digital highways into
electronic circuits, this will be one of the ‘ ‘killer
applications’’ of plasmonics.
Plasmonic Light Sources
The emerging field of plasmonics is not only
limited to the propagation of light in structures
with subwavelen gth dimensions . Plasmonics can
also help to generate and manipulate electro-
magnetic radiation in various wavelengths from
optics to microwaves. Since their introduction
by Nakamura in 1995 (19), InGaN-based semi-
conductor light emitting diodes (LEDs) have
become promising candidates for a variety of
solid-state lightning applications (20). How-
ever, semiconductor-based LEDs are also no-
torious for their low light-emission efficiencies.
Plasmonics can be used to solve this efficiency
problem (21). When InGaN/GaN quantum wells
(QWs) are coated by nanometer silver or alu-
minum films, the resulting SPs increase the den-
sity of states and the spontaneous emission rate
in the semiconductor. This leads to the enhance-
ment of light emission by SP-QW coupling,
which results in large enhancements of internal
quantum efficiencies. Time-resolved photolu-
minescence spectroscopy measurements were
used to achieve a 32-fold increase in the spon-
taneous emission rate of an InGaN/GaN QW at
440 nm (22). This enhancement of the emission
rates and intensities results from the efficient
energy transfer from electron-hole pair recom-
bination in the QW to electron vibrations of
SPs at the metal-coated surface of the semi-
conductor heterostructure. This QW-SP cou-
pling is expected to lead to a new class of super
bright and high-speed LEDs that offer realistic
alternatives to conventional fluorescent tubes.
Similar promising results were obtained
for organic LEDs (OLEDs), which are now
becoming popular as digital displays. In an
OLED, up to 40% of the power that can be
coupled into air is lost due to quenching by
SP modes. A periodic microstructure can be
used to recover the power that is normally
lost to SPs. Using this approach, strong photo-
luminescence has been reported fro m a top-
emitting organic light-emitting structure, where
emission takes place through a thin silver film
(23). The results indicate that the addition of a
nanopatterned diel ectric overlayer to the cath-
ode of top-emitting OLEDs should increase
light emission from these structures by two or-
ders of magnitude over a similar planar struc-
ture. The dielectric layer acts to couple the
surface plasmon-polariton modes on the two
metal surfaces, whereas its corrugated morphol-
ogy allows the modes to scatter to light. An
OLED using a p-conjugated polymer emissive
layer sandwiched between two semitransparent
electrodes was also reported (24). One of the
electrodes was an optically thin gold film anode,
whereas the cathode was in the form of an
optically thick aluminum (Al) film with pat-
terned periodic subwavelength two-dimensional
(2D) hole array that showed anomalous trans-
mission in the spectral range of the polymer
photoluminescence band. At similar current
densities, a sevenfold electroluminescence ef-
ficiency enhancement was obtained with the
patterned Al device compared with a control
device based on imperforated Al electrode,
demonstrating that the method of patterning
the electrodes into 2D hole arrays is efficient
for this structure. Plasmonics can also be used
to enhance the performance of lasers (25). A
metal nano-aperture was fabricated on top of
a GaAs vertical cavity surface emitting laser
(VCSEL) for subwavelength optical near-field
probing. The optical near-field intensity and
the signal voltage of nano-aperture VCSELs
exhibit record high values because of the lo-
calized surface plasmons in metal nanostruc-
tures. The enhancement factors of the optical
near-field and voltage signal are 1.8 and 2,
respectively. Reducing the nano-aperture re-
duces the optical resolution of the VCSEL probe
from 240 nm to 130 nm. These results show that
plasmon enhancement will be helpful for real-
izing high-resolution optical near-field VCSEL
probes.
SPs also play a key role in the transmis-
sion properties of single apertures and the en-
hanced transmission through subwavelength
hole arrays (26, 27). There has been intense
controversy on the physical origin of the en-
hanced transmission in these structures (28).
Recent theoretical and experimental analyses
suggest that the enhanced transmission can be
explained by diffraction assisted by the enhanced
fields associated with SPs (29, 30). Although
SPs are mostly studied at optical frequencies,
they can also be observed at the microwave,
millimeter-wave, and THz frequencies (31).
By texturing the metallic surface with a subwave-
length pattern, we can create SPs that are re-
sponsible for enhanced transmission observed at
microwave and millimeter wave frequencies for
1D and 2D gratings with subwavelength aper-
tures (32, 33). A subwavelength circular aper-
ture with concentric periodic grooves can be
used to obtain enhanced microwave transmis-
sion near the surface plasmon resonance fre-
quency (34). These results show that enhanced
transmission from a subwavelength circular
annular aperture with a grating is assisted by
the guided mode of the coaxial waveguide and
coupling to the surface plasmons. A 145-fold
enhancement factor is obtained with a subwave-
length circular annular aperture surrounded
by concentric periodic grooves. The same
structure also exhibits beaming properties that
are similar to the beaming effects observed from
a subwavelength aperture at optical wavelengths
(35). Figure 3 shows the electromagnetic waves
from a subwavelength circular annular aperture
surrounded by concentric periodic grooves. The
rad i a te d electromagnetic waves have a very
strong angular confinement around the sur-
face mode resonance frequency, in which the
angular divergence of the beam is T3-. En-
hanced transmission at THz wavelengths is
also reported for a freestanding metal foil per-
forated with periodic arrays of subwavelength
apertures (36). The peak transmission at the
lowest frequency resonance is È0.6 for each
aperture array, which is a factor of È 5 larger
than the fractional area occupied by the aper-
tures. Doped semiconductors exhibit a behavior
at THz frequenc ies similar to that of metals at
optical frequencies, thus they constitute an op-
timal material for THz plasmonics (37). Enhanced
transmission of THz radiation is observed by
using arrays of subwavelength apertures struc-
tured in n-type silicon. This enhancement can
be exp lained by the resonant tunneling of
SPs that can be excited at THz wavelengths
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in doped semiconductors. The transmission in-
creases markedly as the aperture size is aug-
mented and as the array thickness is reduced.
Plasmonic Nanolithography
The minimum feature size used within state-
of-the-art electronic circuits is on the order of
50 nm, and new lithography techniques need
to be developed to fabricate these integrated
circuits with nanometer-scale dimensions. Op-
tical projection lithography at shorter optical
wavelengths can be used to reach the desired
feature sizes. However, the change of the illu-
mination wavelength to shorter wavelengths
means new light sources, photoresists, and op-
tics that are becomingly increasingly more com-
plex as the wavelength becomes smaller. SPs
result in a strongly enhanced nanoscale spa-
tial distribution of an electrical field near the
metal surface. When the resonance frequency
falls within the sensitivity range of a photo-
resist, the resulting enhanced optical field that
is close to the metal surface can locally cause
increased exposure of a thin layer of resist
directly below the mask. Because the tech-
nique is not diffraction limited, it can produce
subwavelength structures using broad beam
illumination of standard photoresist with vis-
ible light. Using this technique, sub–100-nm
lines have been patterned photolithographically
at a wavelength of 436 nm (38). Theoretical
simulations of plasmonic nanolithography pre-
dict even better performance (39). Finite dif-
ference time domain (FDTD) simulations of
isolated silver particles on a thin resist lay-
er show that broad beam illumination with
p-polarized light at a wavelength of 439 nm can
produce features as small as 30 nm, or l/14,
where l is the wavelength. Depending on the
exposure time, lateral spot sizes ranging from
30 to 80 nm with exposure depths ranging from
12 to 45 nm can be achieved.
The performance of plasmonic nanolithog-
raphy can be boosted by using the ‘ ‘sup erlens’’
concept introduced by Pendry (40). A superlens
can be used to enhance evanescent waves via
the excitation of surface plasmons. The gain
obtained from plasmonic excitation inside the
superlens compensates for the loss of the eva-
nescent waves outside of the superlens. The
reconstructed evanescent waves can then be
used to restore an image below the diffraction
limit on the other side of the lens. This unusual
lens can be constructed by using a thin slab of
material with negative permittivity or perme-
ability, or both. By using si lver as a natural
optical superlens, sub–diffraction-limited imag-
ing with 60 nanometer half-pitch resolution, or
one-sixth of the illumination wavelength, was
demonstrated (41). By proper design of the work-
ing wavelength and the thickness of silver, which
allows access to a broad spectrum of subwave-
length features, arbitrary nanostructures can also
be imaged with good fidelity. Figure 4 com-
pares the performance of this superlens-based
plasmonic nanolithography to conventional nano-
lithography. A 365-nm exposure wavelength
was used for both nanolithography experiments.
The word ‘ ‘NANO’’ was printed as a mask by a
focused ion beam (FIB) system (Fig. 4A). Figure
4B was obtained with the superlens, and the
resulting image on the resist is almost perfect.
Figure 4C shows the diffraction limited image
obtained from the conventional lithography.
Figure 4D numerically compares both methods.
Although the resolution achieved by convention-
al methods is limited to È320 nm, the plasmonic
nanolithography method was able to generate an
image with Èfour times better resolution. Super-
resolution imaging using the same method was
also reported for a 50-nm-thick planar silver
superlens at wavelengths around 365 nm (42).
Gratings with periods down to 145 nm can be
resolved, which agrees well with the FDTD simu-
lations. These are the preliminary demonstrations
of superlens-based plasmonic nanolithography,
and additional research for further improvements
in subwavelength resolution, aerial coverage, and
uniformity is needed. After these improvements,
plasmonic nanolithography may be a viable al-
ternative to other nanolithography systems.
Future Directions and Challenges
The field of plasmonics offers several research
opportunities. These include plasmonic chips
that function as ultra–low-loss optical inter-
connects, plasmonic circuits and components
that can guide light within ultracompact op-
tically functional devices, nanolithography at
deep subwavelength scale, superlenses that en-
able optical imaging with unprecedented resolu-
tion, and new light sources with unprecedented
performance. To fulfill the promise offered by
plasmonics, more research needs to be done in
these areas. Some of the challenges that face
Fig. 3. Calculated (A) and measured (B) electric field distribution from a subwavelength circular
annular aperture with a grating at the resonance frequency. The measured electric field intensity is
confined to a narrow spatial region and propagates without diffracting into a wide angular region,
which is in good agreement with the simulations.
Fig. 4. The images of an arbitrary object obtained by different methods. (A) FIB image of the
object. (B) The image obtained on photoresist with a silver superlens. (C) The image obtained on
photoresist with conventional lithography. (D) Comparison of both methods. [Adapted from (40)]
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plasmonics research in the coming years are as
follows: (i) demonstrate optical frequency sub-
wavelength metallic wired circuits with a prop-
agation loss that is comparable to conventional
optical waveguides; (ii) develop highly efficient
plasmonic organic and inorganic LEDs with
tunable radiation properties; (iii) achieve active
control of plasmonic signals by implementing
electro-optic, all-optical, and piezoelectric modu-
lation and gain mechanisms to plasmonic struc-
tures; (iv) demonstrate 2D plasmonic optical
components, including lenses and grating cou-
plers, that can couple single mode fiber di-
rectly to plasmonic circuits; and (v) develop
deep subwavelength plasmonic nanolithography
over large surfaces.
Conclusion
The research on plasmonics has made major
advances in the past few years. Besides creating
new photonics devices, which are considerably
smaller than the propagating light’s wavelength,
plasmonics is expected to be the key nanotech-
nology that will combine electronic and photo-
nic components on the same chip.
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43. This work was supported by the projects EU–DALHM,
EU–NOE–METAMORPHOSE, EU–NOE–PHOREMOST, and
TUBITAK-104E090. E.O. also acknowledges partial
support from the Turkish Academy of Sciences.
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