68 research outputs found
Polarization state of the optical near-field
The polarization state of the optical electromagnetic field lying several
nanometers above complex dielectric structures reveals the intricate
light-matter interaction that occurs in this near-field zone. This information
can only be extracted from an analysis of the polarization state of the
detected light in the near-field. These polarization states can be calculated
by different numerical methods well-suited to near--field optics. In this
paper, we apply two different techniques (Localized Green Function Method and
Differential Theory of Gratings) to separate each polarisation component
associated with both electric and magnetic optical near-fields produced by
nanometer sized objects. The analysis is carried out in two stages: in the
first stage, we use a simple dipolar model to achieve insight into the physical
origin of the near-field polarization state. In the second stage, we calculate
accurate numerical field maps, simulating experimental near-field light
detection, to supplement the data produced by analytical models. We conclude
this study by demonstrating the role played by the near-field polarization in
the formation of the local density of states.Comment: 9 pages, 11 figures, accepted for publication in Phys. Rev.
Fano resonances in plasmonic core-shell particles and the Purcell effect
Despite a long history, light scattering by particles with size comparable
with the light wavelength still unveils surprising optical phenomena, and many
of them are related to the Fano effect. Originally described in the context of
atomic physics, the Fano resonance in light scattering arises from the
interference between a narrow subradiant mode and a spectrally broad radiation
line. Here, we present an overview of Fano resonances in coated spherical
scatterers within the framework of the Lorenz-Mie theory. We briefly introduce
the concept of conventional and unconventional Fano resonances in light
scattering. These resonances are associated with the interference between
electromagnetic modes excited in the particle with different or the same
multipole moment, respectively. In addition, we investigate the modification of
the spontaneous-emission rate of an optical emitter at the presence of a
plasmonic nanoshell. This modification of decay rate due to electromagnetic
environment is referred to as the Purcell effect. We analytically show that the
Purcell factor related to a dipole emitter oriented orthogonal or tangential to
the spherical surface can exhibit Fano or Lorentzian line shapes in the near
field, respectively.Comment: 28 pages, 10 figures; invited book chapter to appear in "Fano
Resonances in Optics and Microwaves: Physics and Application", Springer
Series in Optical Sciences (2018), edited by E. O. Kamenetskii, A. Sadreev,
and A. Miroshnichenk
Polarization-dependent fluorescence from an anisotropic gold/polymer hybrid nano-emitter
Based on nanoscale photopolymerization triggered by the dipolar surface plasmon mode, we developed a light-emitting gold nanoparticle/Eosin Y-doped polymer hybrid nanostructure. Due to the anisotropic spatial distribution of the dipolar surface plasmon mode during photopolymerization, this nano-emitter is anisotropic in both geometry and emission. The trapped dye molecules in the hybrid nanostructure display fluorescence intensity that is dependent upon the polarization of the incident excitation light. This nano-emitter further allows the photo-selection of fluorescence configuration (i.e., molecule concentration and refractive index of active medium) by controlling the incident polarization. (C) 2014 AIP Publishing LLC
Improvement of infrared single-photon detectors absorptance by integrated plasmonic structures
Plasmonic structures open novel avenues in photodetector development. Optimized illumination configurations are reported to improve p-polarized light absorptance in superconducting-nanowire single-photon detectors (SNSPDs) comprising short- and long-periodic niobium-nitride (NbN) stripe-patterns. In OC-SNSPDs consisting of ~quarter-wavelength dielectric layer closed by a gold reflector the highest absorptance is attainable at perpendicular incidence onto NbN patterns in P-orientation due to E-field concentration at the bottom of nano-cavities. In NCAI-SNSPDs integrated with nano-cavity-arrays consisting of vertical and horizontal gold segments off-axis illumination in S-orientation results in polar-angle-independent perfect absorptance via collective resonances in short-periodic design, while in long-periodic NCAI-SNSPDs grating-coupled surface waves promote EM-field transportation to the NbN stripes and result in local absorptance maxima. In NCDAI-SNSPDs integrated with nano-cavity-deflector-array consisting of longer vertical gold segments large absorptance maxima appear in 3p-periodic designs due to E-field enhancement via grating-coupled surface waves synchronized with the NbN stripes in S-orientation, which enable to compensate fill-factor-related retrogression.United States. Dept. of Energy (Frontier Research Centers
Measuring the orientation of a single CdSe/CdS nanocrystal at the end of a near-field tip for the realization of a versatile active SNOM probe
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