942 research outputs found
Tuning the emission wavelength of Si nanocrystals in SiO2 by oxidation
Si nanocrystals (diameter 2â5 nm) were formed by 35 keV Si + implantation at a fluence of 6 Ă 1016 Si/cm2 into a 100 nm thick thermally grown SiO2 film on Si (100), followed by thermal annealing at 1100 °C for 10 min. The nanocrystals show a broad photoluminescence spectrum, peaking at 880 nm, attributed to the recombination of quantum confined excitons. Rutherford backscattering spectrometry and transmission electron microscopy show that annealing these samples in flowing O2 at 1000 °C for times up to 30 min results in oxidation of the Si nanocrystals, first close to the SiO2 film surface and later at greater depths. Upon oxidation for 30 min the photoluminescence peak wavelength blueshifts by more than 200 nm. This blueshift is attributed to a quantum size effect in which a reduction of the average nanocrystal size leads to emission at shorter wavelengths. The room temperature luminescence lifetime measured at 700 nm increases from 12 ”s for the unoxidized film to 43 ”s for the film that was oxidized for 29 min
Emitter-Metasurface Interface for Manipulating Emission Characteristics of Quantum Defects
We demonstrate a chip-scale quantum emitter-metamaterial device that emits highly directional photons. Our device opens the door for quantum imaging of yveak sources by adding photon(s) to manipulate the photon statistics for improved signal-to-noise ratio
Emitter-Metasurface Interface for Manipulating Emission Characteristics of Quantum Defects
We demonstrate a chip-scale quantum emitter-metamaterial device that emits highly directional photons. Our device opens the door for quantum imaging of yveak sources by adding photon(s) to manipulate the photon statistics for improved signal-to-noise ratio
Boundary and Coulomb Effects on Boson Systems in High-Energy Heavy-Ion Collisions
The boundary of a boson system plays an important role in determining the
momentum distribution of the bosons. For a boson system with a cylindrical
boundary, the momentum distribution is enhanced at high transverse momenta but
suppressed at low transverse momenta, relative to a Bose-Einstein distribution.
The boundary effects on systems of massless gluons and massive pions are
studied. For gluons in a quark-gluon plasma, the presence of the boundary may
modify the signals for the quark-gluon plasma. For pions in a pion system in
heavy-ion collisions, Coulomb final-state interactions with the nuclear
participants in the vicinity of the central rapidity region further modify the
momentum distribution at low transverse momenta. By including both the boundary
effect and the Coulomb final-state interactions we are able to account for the
behavior of the transverse momentum spectrum observed in many
heavy-ion experiments, notably at low transverse momenta.Comment: 15 pages Postscript uuencoded tar-comprssed file, 9 Postscript
figures uuencoded tar-compressed fil
Autonomous Bursting in a Homoclinic System
A continuous train of irregularly spaced spikes, peculiar of homoclinic
chaos, transforms into clusters of regularly spaced spikes, with quiescent
periods in between (bursting regime), by feeding back a low frequency portion
of the dynamical output. Such autonomous bursting results to be extremely
robust against noise; we provide experimental evidence of it in a CO2 laser
with feedback. The phenomen here presented display qualitative analogies with
bursting phenomena in neurons.Comment: Submitted to Phys. Rev. Lett., 14 pages, 5 figure
Graphene plasmonics: A platform for strong light-matter interaction
Graphene plasmons provide a suitable alternative to noble-metal plasmons
because they exhibit much larger confinement and relatively long propagation
distances, with the advantage of being highly tunable via electrostatic gating.
We report strong light- matter interaction assisted by graphene plasmons, and
in particular, we predict unprecedented high decay rates of quantum emitters in
the proximity of a carbon sheet, large vacuum Rabi splitting and Purcell
factors, and extinction cross sections exceeding the geometrical area in
graphene ribbons and nanometer-sized disks. Our results provide the basis for
the emerging and potentially far-reaching field of graphene plasmonics,
offering an ideal platform for cavity quantum electrodynamics and supporting
the possibility of single-molecule, single-plasmon devices.Comment: 39 pages, 15 figure
Origin of Shifts in the Surface Plasmon Resonance Frequencies for Au and Ag Nanoparticles
Origin of shifts in the surface plasmon resonance (SPR) frequency for noble
metal (Au, Ag) nanoclusters are discussed in this book chapter. Spill out of
electron from the Fermi surface is considered as the origin of red shift. On
the other hand, both screening of electrons of the noble metal in porous media
and quantum effect of screen surface electron are considered for the observed
blue shift in the SPR peak position.Comment: 37 pages, 14 Figures in the submitted book chapter of The Annual
Reviews in Plasmonics, edited by Professor Chris D. Geddes. Springer Scinec
A single-photon transistor using nano-scale surface plasmons
It is well known that light quanta (photons) can interact with each other in
nonlinear media, much like massive particles do, but in practice these
interactions are usually very weak. Here we describe a novel approach to
realize strong nonlinear interactions at the single-photon level. Our method
makes use of recently demonstrated efficient coupling between individual
optical emitters and tightly confined, propagating surface plasmon excitations
on conducting nanowires. We show that this system can act as a nonlinear
two-photon switch for incident photons propagating along the nanowire, which
can be coherently controlled using quantum optical techniques. As a novel
application, we discuss how the interaction can be tailored to create a
single-photon transistor, where the presence or absence of a single incident
photon in a ``gate'' field is sufficient to completely control the propagation
of subsequent ``signal'' photons.Comment: 20 pages, 4 figure
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