345 research outputs found
Local field enhancement: comparing self-similar and dimer nanoantennas
We study the local field enhancement properties of self-similar nanolenses
and compare the obtained results with the performance of standard dimer
nanoantennas. We report that, despite the additional structural complexity,
self-similar nanolenses are unable to provide significant improvements over the
field enhancement performance of standard plasmonic dimers
Direct detection of single molecules by optical absorption
The advent of single molecule optics has had a profound impact in fields
ranging from biophysics to material science, photophysics, and quantum optics.
However, all existing room-temperature single molecule methods have been based
on fluorescence detection of highly efficient emitters. Here we demonstrate
that standard, modulation-free measurements known from conventional absorption
spectrometers can indeed detect single molecules. We report on quantitative
measurements of the absorption cross section of single molecules under ambient
condition even in their dark state, for example during photoblinking or strong
quenching. Our work extends single-molecule microscopy and spectroscopy to a
huge class of materials that absorb light but do not fluoresce efficiently.Comment: 15 pages, 4 figure
Extinction imaging of a single quantum emitter in its bright and dark states
Room temperature detection of single quantum emitters has had a broad impact
in fields ranging from biophysics to material science, photophysics, or even
quantum optics. These experiments have exclusively relied on the efficient
detection of fluorescence. An attractive alternative would be to employ direct
absorption, or more correctly expressed "extinction" measurements. Indeed,
small nanoparticles have been successfully detected using this scheme in
reflection and transmission. Coherent extinction detection of single emitters
has also been reported at cryogenic temperatures, but their room temperature
implementation has remained a great laboratory challenge owing to the expected
weak signal-to-noise ratio. Here we report the first extinction study of a
single quantum emitter at ambient condition. We obtain a direct measure for the
extinction cross section of a single semiconductor nanocrystal both during and
in the absence of fluorescence, for example in the photobleached state or
during blinking off-times. Our measurements pave the way for the detection and
absorption spectroscopy of single molecules or clusters of atoms even in the
quenched state
Chiral Surface Waves for Enhanced Circular Dichroism
We present a novel chiral sensing platform that combines a one-dimensional
photonic crystal design with a birefringent surface defect. The platform
sustains simultaneous transverse electric and transverse magnetic surface
modes, which are exploited to generate chiral surface waves. The present design
provides homogeneous and superchiral fields of both handednesses over
arbitrarily large areas in a wide spectral range, resulting in the enhancement
of the circular dichroism signal by two orders of magnitude, thus paving the
road toward the successful combination of surface-enhanced spectroscopies and
electromagnetic superchirality.Comment: Added references. Corrected typos. Included new design for broadband
chiral surface wave
Single-Photon Imaging and Efficient Coupling to Single Plasmons
We demonstrate strong coupling of single photons emitted by individual
molecules at cryogenic and ambient conditions to individual nanoparticles. We
provide images obtained both in transmission and reflection, where an
efficiency greater than 55% was achieved in converting incident narrow-band
photons to plasmon-polaritons (plasmons) of a silver nanoparticle. Our work
paves the way to spectroscopy and microscopy of nano-objects with sub-shot
noise beams of light and to triggered generation of single plasmons and
electrons in a well-controlled manner
Computation of Electrostatic Field near Three-Dimensional Corners and Edges
Theoretically, the electric field becomes infinite at corners of two and
three dimensions and edges of three dimensions. Conventional finite-element and
boundary element methods do not yield satisfactory results at close proximity
to these singular locations. In this paper, we describe the application of a
fast and accurate BEM solver (which usesexact analytic expressions to compute
the effect of source distributions on flatsurfaces) to compute the electric
field near three-dimensional corners and edges. Results have been obtained for
distances as close as 1 near the corner/edge and good agreement has been
observed between the present results and existing analytical solutions.Comment: Presented in International Conference on Computational and
Experimental Engineering and Sciences held at IIT Madras, Chennai, India,
during 1-6 December, 200
Evidence for cascaded third harmonic generation in non-centrosymmetric gold nanoantennas
The optimization of nonlinear optical processes at the nanoscale is a crucial
step for the development of nanoscale photon sources for quantum-optical
networks. The development of innovative plasmonic nanoantenna designs and
hybrid nanostructures to enhance optical nonlinearities in very small volumes
represents one of the most promising routes. In such systems, the upconversion
of photons can be achieved with high efficiencies via third-order processes,
such as third harmonic generation (THG), thanks to the resonantly-enhanced
volume currents. Conversely, second-order processes, such as second harmonic
generation (SHG), are often inhibited by the symmetry of metal lattices and of
common nanoantenna geometries. SHG and THG processes in plasmonic
nanostructures are generally treated independently, since they both represent a
small perturbation in the light-matter interaction mechanisms. In this work, we
demonstrate that this paradigm does not hold in general, by providing evidence
of a cascaded process in THG, which is fueled by SHG and sizably contributes to
the overall yield. We address this mechanism by unveiling an anomalous
fingerprint in the polarization state of the nonlinear emission from
non-centrosymmetric gold nanoantennas and point out that such cascaded
processes may also appear for structures that exhibit only moderate SHG yields
- signifying its general relevance in plasmon-enhanced nonlinear optics. The
presence of this peculiar mechanism in THG from plasmonic nanoantennas at
telecommunication wavelengths allows gaining further insight on the physics of
plasmon-enhanced nonlinear optical processes. This could be crucial in the
realization of nanoscale elements for photon conversion and manipulation
operating at room-temperature.Comment: 25 pages, 4 figure
Frontiers in photonics spotlight
Highlighting remarkable research output is an important mission of journals and scientists engaged in dissemination. With this spotlight-review we would like to provide visibility to some of the best recent research outputs and stress the pivotal role of their authors in the Photonics field
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