Heat generation in plasmonic nanostructures has attracted enormous attention due to the ability of these nanostructures
to generate high temperatures in nanoscale volumes using far-field irradiation, enabling applications ranging from
photothermal therapy to fast (sub-nanosecond) thermal optical switching. Here we investigate the optical and thermal
response of a heterogeneous trimer structure composed of a gold nanoparticle surrounded by two larger silver
nanoparticles analytically and numerically. We observe that this type of multi-scale multi-material plasmonic oligomer
can produce temperature changes over two orders of magnitude higher than possible with isolated gold nanoparticles.
Optical field enhancement in coupled plasmonic nanostructures has attracted significant attention because of field
enhancement factors that significantly exceed those observed in isolated nanostructures. While previous studies
demonstrated the existence of such cascaded field enhancement in coupled nanospheres with identical composition, this
effect has not yet been studied in systems containing multiple materials. Here, we investigate the polarization-dependent
optical response of multi-material trimer nanostructures composed of Au nanoparticles surrounded by two Ag
nanoparticles as a function of nanoparticle size and inter-particle spacing. We observe field enhancement factors that are
ten times larger than observed in isolated Au nanoparticles.
Cascaded optical field enhancement in coupled plasmonic nanostructures has attracted significant attention because of
field enhancement factors that dramatically exceed those observed in isolated nanostructures. While previous studies
demonstrated the existence of cascaded enhancement, little work has been done to identify the requirements for
achieving maximum field enhancement. Here, we investigate cascaded field enhancement in silver nanosphere dimers as
a function of volume ratio and center-to-center separation, and show the requirements for achieving the ultimate
cascading limit in nanoparticle dimers. We observe field enhancements that are a factor 75 larger than observed in
isolated silver nanoparticles.
The optical properties of cascaded plasmon resonant metallic nanocomposites are investigated. Plasmon resonances and
their related field distributions are numerically evaluated in two-dimensional arrays of spherical silver nanoparticles
embedded in a dielectric host. The field distributions in structures with identical particle sizes indicate the presence of a
largely dipolar particle response, with a small multipole resonance contribution at high frequency. However, in arrays
consisting of particles with dissimilar sizes, an additional coupled mode appears in which the dipole moment in adjacent
particles is found to be anti-parallel. For increasing size-dissimilarity a higher electric field enhancement is observed
inside the small metal nanospheres, indicative of a cascaded field enhancement effect. This effect may be used to
enhance the nonlinear optical response of an effective medium composed of particles with engineered size dispersion
and particle placement.
In this article, we propose a simple method to increase the pressure sensitivity of a typical fiber Bragg grating (FBG) while decreasing the temperature sensitivity. This method uses a typical FBG, which is coated with a thick layer of polymer with two symmetric air channels. By this method the pressure sensitivity can be increased (e.g. 1.1×10<sup>-5</sup> /MPa) while the temperature sensitivity is negligible (e.g. -0.174×10<sup>-8</sup>/<sup>o</sup>C) by proper selection of the geometrical parameters and material types of the sensor.