The localized surface plasmon resonance (LSPR) of a nanoplasmonic particle is often considered to occur at a single
resonant wavelength. However, the physical measures of plasmon resonance, namely the far-field measures of
scattering, absorption, and extinction, and the near-field measures of surface-average or maximum electric field
intensity, depend differently on the particle polarizability, and hence may be maximized at different wavelengths. We
show using analytic Mie theory that the differences in peak wavelength between the near- and far-fields can reach over
200 nm for nanoparticle sizes commonly used in spectroscopy applications. Using finite element analysis, we also
consider the effect of varying particle shape to spheroidal geometries, and consider polarization dependence. Using the
quasi-static and extended quasi-static approximation, we show that the differences between the near- and far- field
measures of plasmon resonance can be largely explained by radiation damping effects. We suggest that accounting for
these differences is relevant both for optimizing device design, and for improving fundamental understanding of surface-enhanced
mechanisms such as surface-enhanced Raman spectroscopy (SERS).
While technology relies on components defined in a fixed position on a rigid substrate, nature prefers soft substrates, and
allows components to move significantly during morphogenesis. Taking inspiration from biological fabrication, we have
developed a technique, called active polymer nanofabrication, which utilizes thermally active polymers to create
complex nanoplasmonic substrates designed for molecular detection. We demonstrate the ability of active polymer
nanofabrication to create ultra-dense nanoplasmonic prism arrays (plasmonic nanoflowers), and correlate changes in
array morphology with optical properties. We investigate the associated changes in local electromagnetic fields with
finite element analysis. Finally, we demonstrate the ability of active polymers to deform macroscopically while retaining
nanostructure morphology. We expect these properties will make active polymer nanofabrication useful for a wide range
of nanoplasmonic devices.
Sculptured thin films (STFs) are porous thin films manufactured by physical vapor deposition processes, and
possess a morphology that is engineered at the nanoscale. When a circularly polarized plane wave is obliquely
incident on a chiral STF, the Maxwell stress dyadic exhibits a decreasing periodic variation across the thickness
of the film. Normal and tangential surface tractions exist on the two faces of the chiral STF, as well as a net
normal pressure across the film. These stresses are affected by the incidence angle of light, and are maximized
when (i) the incident plane wave and the chiral STF are co-handed, (ii) the wavelength falls within a regime
called the Bragg regime, (iii) the ratio of film thickness to the structural period of the chiral STF reaches a
saturation value, (iv) the deviation from normal incidence is small, (v) the loss factor in the chiral STF is as
low as possible, and (vi) the vapor incidence angle is optimally chosen during film deposition.
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