43,531 research outputs found
Collective resonances in plasmonic crystals: Size matters
Periodic arrays of metallic nanoparticles may sustain Surface Lattice
Resonances (SLRs), which are collective resonances associated with the
diffractive coupling of Localized Surface Plasmon Resonances (LSPRs). By
investigating a series of arrays with varying number of particles, we traced
the evolution of SLRs to its origins. Polarization resolved extinction spectra
of arrays formed by a few nanoparticles were measured, and found to be in very
good agreement with calculations based on a coupled dipole model. Finite size
effects on the optical properties of the arrays are observed, and our results
provide insight into the characteristic length scales for collective plasmonic
effects: for arrays smaller than 5 x 5 particles, the Q-factors of SLRs are
lower than those of LSPRs; for arrays larger than 20 x 20 particles, the
Q-factors of SLRs saturate at a much larger value than those of LSPRs; in
between, the Q-factors of SLRs are an increasing function of the number of
particles in the array.Comment: 4 figure
Direct and Heterodyne Detection of Microwaves in a Metallic Single Wall Carbon Nanotube
This letter reports measurements of microwave (up to 4.5 GHz) detection in
metallic single-walled carbon nanotubes. The measured voltage responsivity was
found to be 114 V/W at 77K. We also demonstrated heterodyne detection at 1 GHz.
The detection mechanism can be explained based on standard microwave detector
theory and the nonlinearity of the DC IV-curve. We discuss the possible causes
of this nonlinearity. While the frequency response is limited by circuit
parasitics in this measurement, we discuss evidence that indicates that the
effect is much faster and that applications of carbon nanotubes as terahertz
detectors are feasible
Exceptional precision of a nonlinear optical sensor at a square-root singularity
Exceptional points (EPs) -- spectral singularities of non-Hermitian linear
systems -- have recently attracted great interest for sensing. While initial
proposals and experiments focused on enhanced sensitivities neglecting noise,
subsequent studies revealed issues with EP sensors in noisy environments. Here
we propose a single-mode Kerr-nonlinear resonator for exceptional sensing in
noisy environments. Based on the resonator's dynamic hysteresis, we define a
signal that displays a square-root singularity akin to an EP. In contrast to EP
sensors, our sensor has a signal-to-noise ratio that increases with the
measurement speed, and a precision enhanced at the square-root singularity.
Remarkably, averaging the signal can quickly enhance and then degrade the
precision. These unconventional features open up new opportunities for fast and
precise sensing beyond the constraints of linear systems. While we focus on
optical sensing, our approach can be extended to other hysteretic systems.Comment: 8 pages, including 1 page of supplemental materia
Thermalization and Cooling of Plasmon-Exciton Polaritons: Towards Quantum Condensation
We present indications of thermalization and cooling of quasi-particles, a
precursor for quantum condensation, in a plasmonic nanoparticle array. We
investigate a periodic array of metallic nanorods covered by a polymer layer
doped with an organic dye at room temperature. Surface lattice resonances of
the array---hybridized plasmonic/photonic modes---couple strongly to excitons
in the dye, and bosonic quasi-particles which we call
plasmon-exciton-polaritons (PEPs) are formed. By increasing the PEP density
through optical pumping, we observe thermalization and cooling of the strongly
coupled PEP band in the light emission dispersion diagram. For increased
pumping, we observe saturation of the strong coupling and emission in a new
weakly coupled band, which again shows signatures of thermalization and
cooling.Comment: 8 pages, 5 figures including supplemental material. The newest
version includes new measurements and corrections to the interpretation of
the result
New high-pressure phase and equation of state of Ce2Zr2O8
In this paper we report a new high-pressure rhombohedral phase of Ce2Zr2O8
observed from high-pressure angle-dispersive x-ray diffraction and Raman
spectroscopy studies up to nearly 12 GPa. The ambient-pressure cubic phase of
Ce2Zr2O8 transforms to a rhombohedral structure beyond 5 GPa with a feeble
distortion in the lattice. Pressure evolution of unit-cell volume showed a
change in compressibility above 5 GPa. The unit-cell parameters of the
high-pressure rhombohedral phase at 12.1 GPa are ah = 14.6791(3) {\AA}, ch =
17.9421(5) {\AA}, V = 3348.1(1) {\AA}3. The structure relation between the
parent cubic (P2_13) and rhombohedral (P3_2) phases were obtained by
group-subgroup relations. All the Raman modes of the cubic phase showed linear
evolution with pressure with the hardest one at 197 cm-1. Some Raman modes of
the high-pressure phase have a non-linear evolution with pressure and softening
of one low-frequency mode with pressure is found. The compressibility, equation
of state, and pressure coefficients of Raman modes of Ce2Zr2O8 are also
reported.Comment: 33 pages, 8 figures, 6 table
- …