74 research outputs found
Control of surface plasmon resonance in out-diffused silver nanoislands for surface-enhanced Raman scattering
Abstract We present the studies of self-assembled silver nanoislands on the surface of silver ion-exchanged glasses. The nanoislands were formed by out-diffusion of reduced silver atoms from the bulk of the glass to its surface. Control of silver ions distribution in the glass by thermal poling after the ion exchange allowed formation of relatively big, up to 250 nm, isolated silver nanoislands while without the poling an ensemble of silver nanoislands with average size from several to tens of nanometers with random size distribution was formed. The nanoislands were characterized using atomic force microscopy and spectral measurements. We used optical absorption spectroscopy for “random” nanoislands and dark field scattering spectroscopy for isolated ones, corresponding spectra showed peaks in the vicinity of 450 nm and 600 nm, respectively. The “random” nanoislands significantly enhanced Raman scattering from Rhodamine 6G, also the modification of Raman signal from deposited on the surface of the samples bacteriorhodopsin in purple membranes was registered
Dark-field spectroscopy of plasmon resonance in metal nanoislands: effect of shape and light polarization
Abstract We present the experimental dark-field scattering studies and the simulation of plasmonic properties of isolated silver nanoislands. The nanoislands were fabricated on a soda- lime glass substrate using silver-sodium ion exchange, subsequent thermal poling and annealing of the processed glass substrate in hydrogen. The morphology of the nanoislands was characterized with atomic force microscopy and scanning electron microscopy; the dimensions were 100-180 nm in base and 80-160 nm in height. We measured and modeled dark-field scattering spectra of the silver hemiellipsoidal nanoparticles differing in size and shape. The SPR position varied from 450 nm to 730 nm depending on the particle shape and dimensions. Both experiments and simulation showed a red shift of the SPR for bigger nanoislands of the same shape. Losing the axial symmetry in nanoislands resulted in the resonance splitting, while their elongation led to an increase in the scattering of p-polarized light
Room-temperature polaron-mediated polariton nonlinearity in MAPbBr3 perovskites
Systems supporting exciton-polaritons represent solid-state optical platforms
with a strong built-in optical nonlinearity provided by exciton-exciton
interactions. In conventional semiconductors with hydrogen-like excitons the
nonlinearity rate demonstrates the inverse scaling with the binding energy.
This makes excitons stable at room temperatures weakly interacting, which
obviously limits the possibilities of practical applications of the
corresponding materials for nonlinear photonics. We demonstrate experimentally
and theoretically, that these limitations can be substantially softened in
hybrid perovskites, such as MAPbBr3 due to the crucial role of the polaron
effects mediating the inter-particle interactions. The resulting
exciton-polaron-polaritons remain both stable and strongly interacting at room
temperature, which is confirmed by large nonlinear blueshifts of lower
polariton branch energy under resonant femtosecond laser pulse excitation. Our
findings open novel perspectives for the management of the exciton-polariton
nonlinearities in ambient conditions
Optical "fingerprints" of dielectric resonators
The complete picture of the optical properties of resonant structures, along
with the frequency, quality factor, and line shape in the scattering spectra,
is determined by the electromagnetic field distribution patterns, which are a
kind of "fingerprint" of each resonant eigenmode. In this paper, we
simultaneously analyze the changes in the spectra and the transformation of the
field pattern during the topological transitions from a thin disk to a ring
with a gradually increasing thickness and further to a split ring. In addition,
we demonstrate characteristic optical fingerprints for well-known interference
effects such as bound states in the continuum and Fano resonances.Comment: 11 pages, 5 figure
Room-temperature exceptional-point-driven polariton lasing from perovskite metasurface
Excitons in lead bromide perovskites exhibit high binding energy and high
oscillator strength, allowing for a strong light-matter coupling regime in the
perovskite-based cavities localizing photons at the nanoscale. This opens up
the way for the realization of exciton-polariton Bose-Einstein condensation and
polariton lasing at room temperature -- the inversion-free low-threshold
stimulated emission. However, polariton lasing in perovskite planar photon
cavities without Bragg mirrors has not yet been observed and proved
experimentally. In this work, we employ perovskite metasurface, fabricated with
nanoimprint lithography, supporting so-called exceptional points to demonstrate
the room-temperature polariton lasing. The exceptional points in
exciton-polariton dispersion of the metasurface appear upon optically pumping
in the nonlinear regime in the spectral vicinity of a symmetry-protected bound
state in the continuum providing high mode confinement with the enhanced local
density of states beneficial for polariton condensation. The observed lasing
emission possesses high directivity with a divergence angle of around 1
over one axis. The employed nanoimprinting approach for solution-processable
large-scale polariton lasers is compatible with various planar photonic
platforms suitable for on-chip integration.Comment: 12 pages, 3 figure
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