294 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
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
Photoinduced inverse spin Hall effect in Pt/Ge(001) at room temperature
We performed photoinduced inverse spin Hall effect (ISHE) measurements on a
Pt/Ge(001) junction at room temperature. The spin-oriented electrons,
photogenerated at the direct gap of Ge using circularly polarized light,
provide a net spin current which yields an electromotive field E_ISHE in the Pt
layer. Such a signal is clearly detected at room temperature despite the strong
{\Gamma} to L scattering which electrons undergo in the Ge conduction band. The
ISHE signal dependence on the exciting photon energy is in good agreement with
the electron spin polarization expected for optical orientation at the direct
gap of Ge
Mid-Infrared Plasmonic Platform based on Heavily Doped Epitaxial Ge-on-Si: Retrieving the Optical Constants of Thin Ge Epilayers
The n-type Ge-on-Si epitaxial material platform enables a novel paradigm for
plasmonics in the mid-infrared, prompting the future development of
lab-on-a-chip and subwavelength vibrational spectroscopic sensors. In order to
exploit this material, through proper electrodynamic design, it is mandatory to
retrieve the dielectric constants of the thin Ge epilayers with high precision
due to the difference from bulk Ge crystals. Here we discuss the procedure we
have employed to extract the real and imaginary part of the dielectric
constants from normal incidence reflectance measurements, by combining the
standard multilayer fitting procedure based on the Drude model with
Kramers-Kronig transformations of absolute reflectance data in the
zero-transmission range of the thin film.Comment: Infrared, Millimeter, and Terahertz waves (IRMMW-THz), 2014 39th
International Conference o
A virtual reality classroom to teach and explore crystal solid state structures
We present an educational application of virtual reality that we created to help students gain an in-depth understanding of the internal structure of crystals and related key concepts. Teachers can use it to give lectures to small groups (10-15) of students in a shared virtual environment, both remotely (with teacher and students in different locations) and locally (while sharing the same physical space). Lectures can be recorded, stored in an online repository, and shared with students who can either review a recorded lecture in the same virtual environment or can use the application for self-studying by exploring a large collection of available crystal structures. We validated our application with human subjects receiving positive feedback
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
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