5,152 research outputs found
Attosecond nanoplasmonic streaking of localized fields near metal nanospheres
Collective electron dynamics in plasmonic nanosystems can unfold on
timescales in the attosec- ond regime and the direct measurements of plasmonic
near-field oscillations is highly desirable. We report on numerical studies on
the application of attosecond nanoplasmonic streaking spectroscopy to the
measurement of collective electron dynamics in isolated Au nanospheres. The
plasmonic field oscillations are induced by a few-cycle NIR driving field and
are mapped by the energy of photoemitted electrons using a synchronized,
time-delayed attosecond XUV pulse. By a detailed analysis of the amplitudes and
phase shifts, we identify the different regimes of nanoplasmonic streaking and
study the dependence on particle size, XUV photoelectron energy and emission
position. The simulations indicate that the near-fields around the
nanoparticles can be spatio-temporally reconstructed and may give detailed
insight into the build-up and decay of collective electron motion.Comment: Revised versio
Stimulated Raman Adiabatic Passage (STIRAP) as a Route to Achieving Optical Control in Plasmonics
Optical properties of ensembles of three-level quantum emitters coupled to
plasmonic systems are investigated employing a self-consistent model. It is
shown that stimulated Raman adiabatic passage (STIRAP) technique can be
successfully adopted to control optical properties of hybrid materials with
collective effects present and playing an important role in light-matter
interactions. We consider a core-shell nanowire comprised of a silver core and
a shell of coupled quantum emitters and utilize STIRAP scheme to control
scattering efficiency of such a system in a frequency and spatial dependent
manner. After the STIRAP induced population transfer to the final state takes
place, the core-shell nanowire exhibits two sets of Rabi splittings with Fano
lineshapes indicating strong interactions between two different atomic
transitions driven by plasmon near-fields.Comment: 11 pages, 6 figures, accepted, Physical Review
A 300-800MHz Tunable Filter and Linearized LNA applied in a Low-Noise Harmonic-Rejection RF-Sampling Receiver
A multiband flexible RF-sampling receiver aimed at software-defined radio is presented. The wideband RF sampling function is enabled by a recently proposed discrete-time mixing downconverter. This work exploits a voltage-sensing LNA preceded by a tunable LC pre-filter with one external coil to demonstrate an RF-sampling receiver with low noise figure (NF) and high harmonic rejection (HR). The second-order LC filter provides voltage pre-gain and attenuates the source noise aliasing, and it also improves the HR ratio of the sampling downconverter. The LNA consists of a simple amplifier topology built from inverters and resistors to improve the third-order nonlinearity via an enhanced voltage mirror technique. The RF-sampling receiver employs 8 times oversampling covering 300 to 800 MHz in two RF sub-bands. The chip is realized in 65 nm CMOS and the measured gain across the band is between 22 and 28 dB, while achieving a NF between 0.8 to 4.3 dB. The IIP2 varies between +38 and +49 dBm and the IIP3 between -14 dBm and -9 dBm, and the third and fifth order HR ratios are more than 60 dB. The LNA and downconverter consumes 6 mW, and the clock generator takes 12 mW at 800 MHz RF.\ud
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Efficient Volumetric Method of Moments for Modeling Plasmonic Thin-Film Solar Cells with Periodic Structures
Metallic nanoparticles (NPs) support localized surface plasmon resonances
(LSPRs), which enable to concentrate sunlight at the active layer of solar
cells. However, full-wave modeling of the plasmonic solar cells faces great
challenges in terms of huge computational workload and bad matrix condition. It
is tremendously difficult to accurately and efficiently simulate near-field
multiple scattering effects from plasmonic NPs embedded into solar cells. In
this work, a preconditioned volume integral equation (VIE) is proposed to model
plasmonic organic solar cells (OSCs). The diagonal block preconditioner is
applied to different material domains of the device structure. As a result,
better convergence and higher computing efficiency are achieved. Moreover, the
calculation is further accelerated by two-dimensional periodic Green's
functions. Using the proposed method, the dependences of optical absorption on
the wavelengths and incident angles are investigated. Angular responses of the
plasmonic OSCs show the super-Lambertian absorption on the plasmon resonance
but near-Lambertian absorption off the plasmon resonance. The volumetric method
of moments and explored physical understanding are of great help to investigate
the optical responses of OSCs.Comment: 11 pages, 6 figure
Role of Bell Singlet State in the Suppression of Disentanglement
The stability of entanglement of two atoms in a cavity is analyzed in this
work. By studying the general Werner states we clarify the role of Bell-singlet
state in the problem of suppression of disentanglement due to spontaneous
emission. It is also shown explicitly that the final amount of entanglement
depends on the initial ingredients of the Bell-singlet state.Comment: 5 pages, 2 figures, accepted by Phys. Rev.
On the Experimental Estimation of Surface Enhanced Raman Scattering (SERS) Cross Sections by Vibrational Pumping
We present an in-depth analysis of the experimental estimation of cross
sections in Surface Enhanced Raman Scattering (SERS) by vibrational pumping.
The paper highlights the advantages and disadvantages of the technique,
pinpoints the main aspects and limitations, and provides the underlying
physical concepts to interpret the experimental results. Examples for several
commonly used SERS probes are given, and a discussion on future possible
developments is also presented.Comment: To be submitted to J. Phys. Chem.
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