38 research outputs found
Propagation of Surface Plasmons in Ordered and Disordered Chains of Metal Nanospheres
We report a numerical investigation of surface plasmon (SP) propagation in
ordered and disordered linear chains of metal nanospheres. In our simulations,
SPs are excited at one end of a chain by a near-field tip. We then find
numerically the SP amplitude as a function of propagation distance. Two types
of SPs are discovered. The first SP, which we call the ordinary or quasistatic,
is mediated by short-range, near-field electromagnetic interaction in the
chain. This excitation is strongly affected by Ohmic losses in the metal and by
disorder in the chain. These two effects result in spatial decay of the
quasistatic SP by means of absorptive and radiative losses, respectively. The
second SP is mediated by longer range, far-field interaction of nanospheres. We
refer to this SP as the extraordinary or non-quasistatic. The non-quasistatic
SP can not be effectively excited by a near-field probe due to the small
integral weight of the associated spectral line. Because of that, at small
propagation distances, this SP is dominated by the quasistatic SP. However, the
non-quasistatic SP is affected by Ohmic and radiative losses to a much smaller
extent than the quasistatic one. Because of that, the non-quasistatic SP
becomes dominant sufficiently far from the exciting tip and can propagate with
little further losses of energy to remarkable distances. The unique physical
properties of the non-quasistatic SP can be utilized in all-optical integrated
photonic systems
Engineering of Low-Loss Metal for Nanoplasmonic and Metamaterials Applications
We have shown that alloying a noble metal (gold) with another metal
(cadmium), which can contribute two electrons per atom to a free electron gas,
can significantly improve the metals optical properties in certain wavelength
ranges and make them worse in the other parts of the spectrum. In particular,
in the gold-cadmium alloy we have demonstrated a significant expansion of the
spectral range of metallic reflectance to shorter wavelengths. The experimental
results and the predictions of the first principles theory demonstrate an
opportunity for the improvement and optimization of low-loss metals for
nanoplasmonic and metamaterials applications.Comment: 14 Pages, 4 figure
A comparative study of semiconductor-based plasmonic metamaterials
Recent metamaterial (MM) research faces several problems when using
metal-based plasmonic components as building blocks for MMs. The use of
conventional metals for MMs is limited by several factors: metals such as gold
and silver have high losses in the visible and near-infrared (NIR) ranges and
very large negative real permittivity values, and in addition, their optical
properties cannot be tuned. These issues that put severe constraints on the
device applications of MMs could be overcome if semiconductors are used as
plasmonic materials instead of metals. Heavily doped, wide bandgap oxide
semiconductors could exhibit both a small negative real permittivity and
relatively small losses in the NIR. Heavily doped oxides of zinc and indium
were already reported to be good, low loss alternatives to metals in the NIR
range. Here, we consider these transparent conducting oxides (TCOs) as
alternative plasmonic materials for many specific applications ranging from
surface-plasmon-polariton waveguides to MMs with hyperbolic dispersion and
epsilon-near-zero (ENZ) materials. We show that TCOs outperform conventional
metals for ENZ and other MM-applications in the NIR.Comment: 16 pages, 7 figure
Stimulated emission of surface plasmon polaritons
We have observed laser-like emission of surface plasmon polaritons (SPPs)
decoupled to the glass prism in an attenuated total reflection setup. SPPs were
excited by optically pumped molecules in a polymeric film deposited on the top
of the silver film. Stimulated emission was characterized by a distinct
threshold in the input-output dependence and narrowing of the emission
spectrum. The observed stimulated emission and corresponding to it compensation
of the metallic absorption loss by gain enables many applications of
metamaterials and nanoplasmonic devices.Comment: 8 pages; 3 figure
Searching for Better Plasmonic Materials
Plasmonics is a research area merging the fields of optics and
nanoelectronics by confining light with relatively large free-space wavelength
to the nanometer scale - thereby enabling a family of novel devices. Current
plasmonic devices at telecommunication and optical frequencies face significant
challenges due to losses encountered in the constituent plasmonic materials.
These large losses seriously limit the practicality of these metals for many
novel applications. This paper provides an overview of alternative plasmonic
materials along with motivation for each material choice and important aspects
of fabrication. A comparative study of various materials including metals,
metal alloys and heavily doped semiconductors is presented. The performance of
each material is evaluated based on quality factors defined for each class of
plasmonic devices. Most importantly, this paper outlines an approach for
realizing optimal plasmonic material properties for specific frequencies and
applications, thereby providing a reference for those searching for better
plasmonic materials.Comment: 27 pages, 6 figures, 2 table
Frequency-domain simulations of a negative-index material with embedded gain
We solve the equations governing light propagation in a negative-index
material with embedded nonlinearly saturable gain material using a
frequency-domain model. We show that available gain materials can lead to
complete loss compensation only if they are located in the regions where the
field enhancement is maximal. We study the increased enhancement of the fields
in the gain composite as well as in the metal inclusions and show analytically
that the effective gain is determined by the average near-field enhancement.Comment: Accepted to Optics Express. Manuscript contains additional comment