2,616 research outputs found
Origin of the anapole condition as revealed by a simple expansion beyond the toroidal multipole
Toroidal multipoles are a topic of increasing interest in the nanophotonics
and metamaterials communities. In this paper, we separate out the toroidal
multipole components of multipole expansions in polar coordinates (two- and
three-dimensional) by expanding the Bessel or spherical Bessel functions. We
discuss the formation of the lowest order of magnetic anapoles from the
interaction between the magnetic toroidal dipole and the magnetic dipole. Our
method also reveals that there are higher order current configurations other
than the electric toroidal multipole that have the same radiation
characteristics as the pure electric dipole. Furthermore, we find that the
anapole condition requires that there is a perfect cancellation of all higher
order current configurations
Exciton-polariton emission from organic semiconductor optical waveguides
We photo-excite slab polymer waveguides doped with J-aggregating dye
molecules and measure the leaky emission from strongly coupled waveguide
exciton polariton modes at room temperature. We show that the momentum of the
waveguide exciton polaritons can be controlled by modifying the thickness of
the excitonic waveguide. Non-resonantly pumped excitons in the slab excitonic
waveguide decay into transverse electric and transverse magnetic strongly
coupled exciton waveguide modes with radial symmetry. These leak to cones of
light with radial and azimuthal polarizations
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Multispectral imaging with vertical silicon nanowires
Multispectral imaging is a powerful tool that extends the capabilities of the human eye. However, multispectral imaging systems generally are expensive and bulky, and multiple exposures are needed. Here, we report the demonstration of a compact multispectral imaging system that uses vertical silicon nanowires to realize a filter array. Multiple filter functions covering visible to near-infrared (NIR) wavelengths are simultaneously defined in a single lithography step using a single material (silicon). Nanowires are then etched and embedded into polydimethylsiloxane (PDMS), thereby realizing a device with eight filter functions. By attaching it to a monochrome silicon image sensor, we successfully realize an all-silicon multispectral imaging system. We demonstrate visible and NIR imaging. We show that the latter is highly sensitive to vegetation and furthermore enables imaging through objects opaque to the eye
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