Guiding of plasmons and phonons in complex three dimensional structures

The demand for pathways to fabricate and methodologies to understand 3D structures with advanced functionalities has increased significantly over the last years. Materials exhibiting three-dimensional structure with characteristic length scales ranging from nanometers to micrometers have extraordinary potential for emerging optical and thermal applications and are of great current interest in providing new functionalities for a host of applications. The thesis is divided into two primary parts. The majority of the thesis is devoted to understanding light-matter interaction in a new class of devices termed Resonant Guided Wave Networks (RGWNs). We describe how the geometrical properties of the network of waveguides are tuned in conjunction with the materials properties to realize a collective optical response, contrary to other dispersive photonic materials where the response is limited to its discrete elements. In particular, we demonstrate a simple and efficient fabrication of MIM based complex 3D structure that offers a novel approach to optical dispersion control based on resonant structures. This is followed by a description of experiments that probe the optical response of the structures. Of particular interest are surface electromagnetic modes known as surface plasmon-polaritons (SPPs). In the second part of this thesis, we report measurements and modeling of thermal conductivity in periodic three-dimensional dielectric nanostructures: silicon inverse opals. Such structures represent a three-dimensional “phononic crystal” but affect heat flow instead of acoustics. The thermal conductivity of inverse opal films are relatively low, ~0.6-1.4 W/mK at 300 K which is due to macroscopic bending of heat flow lines in the structure. The corresponding material thermal conductivity is in the range 5-12 W/mK and has an anomalous ~ dependence at low temperatures, distinct from the typical ~ behavior of bulk polycrystalline silicon. Using phonon scattering theory, we show such dependence arising from coherent phonon reflections in the inter-grain region. This is consistent with an unconfirmed theory proposed in 1955. The low thermal conductivity is significant for applications in photonics where they imply the possibility of significant temperature rise even at relatively low optical absorption and in thermoelectrics, where they suggest the possibility of enhancement in the figure of merit for polysilicon-based devices