Aperiodic Photonic-Plasmonic Structures with Broadband Field Enhancement.

摘要

This report documents project work performed by Boston University (BU) under a contract awarded by the Natick Soldier Research, Development and Engineering Center (NSRDEC) to Battelle Memorial Institute. The project was aimed at combining plasmonic field enhancement effects in rigorously designed metal-dielectric arrays of nanoparticles with periodic and aperiodic geometries for the demonstration of field-enhanced isomerization with minimum background absorption. BU developed metal-dielectric nanostructures on transparent substrates (quartz, silicon nitride) which can create plasmonic field enhancement engineered over broad frequency bands, while minimizing linear absorption of anisotropic dyes. Based on coupled dipoles and rigorous null- field theory (T-matrix) calculations, BU discovered and explained the fundamental mechanisms governing broadband plasmonic scattering and near-field enhancement in a number of plasmonic structures. A large number of photonic- plasmonic structures with different geometries (from periodic to quasi-periodic and pseudo-random) have been designed by rigorous electrodynamics theory for maximum enhancement at 532nm. BU then fabricated all the structures using Electron beam Lithography, explored the respective roles of morphology, particle shapes, size, and correlated their theory with experiments by dark field scattering spectroscopy and depolarization ellipsometry. The nonlinear optical properties of Azobenzene Doped Polymers was quantified, and integration of limiting devices with micro-fluidics technology was explored. Finally, a plasmonic scatterometer was designed, built, and tested for the accurate measurement of the angular scattering profiles and radiation diagrams of complex nanoplasmonic structures.