Hongcang Guo

Optical resonances of bowtie slot antennas and their geometry and material dependence

In order to provide a guide for the design and optimization of bowtie slot antennas in the visible and near infrared spectral regime, their optical properties have been investigated with emphasis on geometry and materials. Although primarily theoretical, experimental investigations for reduced thickness cases are also included. As characterized by their field patterns, two types of resonances are discussed: plasmonic and Fabry-Pérot-like resonances. These resonance types show a linear dependence on aperture perimeter and film thickness, respectively, while showing a complementary behavior with near independence of the other respective parameter. Metal properties, as in the Drude model, are also considered. Various metals with respectively different skin depths are studied, showing a nearly linear dependence of the resonance wavelength on skin depth.

Resonance hybridization in double split-ring resonator metamaterials

We introduce a plasmon hybridization picture to understand the optical properties of double split-ring resonator metamaterials. The analysis is based on the calculated reflectance spectra from a finite-integration time-domain algorithm. Field distributions of the double split-ring resonators at the resonant frequencies confirm the results from the plasmon hybridization analysis. We demonstrate that the plasmon hybridization is a simple and powerful tool for understanding and designing metamaterials in the near infrared and visible regime.

Large-area two-dimensional photonic crystals of metallic nanocylinders based on colloidal gold nanoparticles

We report on the fabrication of two-dimensional periodic arrays of gold nanocylinders with an aspect ratio larger than 2 using solution-processible gold nanoparticles. We utilize the large surface energy of the melted gold in an annealing process at 260°C to confine the gold nanoparticles into the nanoholes consisting the mask, on which the colloidal gold nanoparticles are spin coated, producing a two-dimensional square lattice of gold nanocylinders. The height of the nanocylinders is larger than 200nm above an indium-tin-oxide waveguide layer and their diameter is about 100nm. Optical extinction spectrum measurements show excellent particle plasmon resonances of the nanocylinders.

Two distinct types of resonances in optical bowtie slot nanoantennas

We study the resonance properties of optical bowtie slot antennas in experiment and numerical simulations. The dependence of the plasmonic and Fabry-Perot-like resonances on the antenna geometry and metal properties is investigated.

Magnetic and electronic resonances for different metamaterial resonator geometries

The influence of the split-ring resonator geometry in a metamaterial on the electromagnetic resonances is analyzed experimentally and theoretically. In our discussion, we focus on both the permeability and the permittivity resonances.