Plasmonic properties and applications of metallic nanostructures

[摘要] Plasmonic properties and the related novel applications are studied on varioustypes of metallic nano-structures in one, two, or three dimensions. For 1D nanostructure,the motion of free electrons in a metal-film with nanoscale thickness is confined inits normal dimension and free in the other two. Describing the free-electron motion atmetal-dielectric surfaces, surface plasmon polariton (SPP) is an elementary excitationof such motions and is well known. When further perforated with periodic array ofholes, periodicity will introduce degeneracy, incur energy-level splitting, and facilitatethe coupling between free-space photon and SPP. We applied this concept to achievea plasmonic perfect absorber. The experimentally observed reflection dip splittingis qualitatively explained by a perturbation theory based on the above concept. Ifconfined in 2D, the nanostructures become nanowires that intrigue a broad range ofresearch interests. We performed various studies on the resonance and propagationof metal nanowires with different materials, cross-sectional shapes and form factors,in passive or active medium, in support of corresponding experimental works. Finite-Difference Time-Domain (FDTD) simulations show that simulated results agrees wellwith experiments and makes fundamental mode analysis possible. Confined in 3D,the electron motions in a single metal nanoparticle (NP) leads to localized surfaceplasmon resonance (LSPR) that enables another novel and important application:plasmon-heating. By exciting the LSPR of a gold particle embedded in liquid, theexcited plasmon will decay into heat in the particle and will heat up the surroundingliquid eventually. With sufficient exciting optical intensity, the heat transfer from NPto liquid will undergo an explosive process and make a vapor envelop: nanobubble.We characterized the size, pressure and temperature of the nanobubble by a simplemodel relying on Mie calculations and continuous medium assumption. A noveleffective medium method is also developed to replace the role of Mie calculations.The characterized temperature is in excellent agreement with that by Raman scattering.If fabricated in an ordered cluster, NPs exhibit double-resonance features andthe double Fano-resonant structure is demonstrated to most enhance the four-wavemixing efficiency.

[发布机构] Rice University

[效力级别] harvesting