This paper describes a facile method of preparing cubic Au nanoframes with open structures via the galvanic replacement reaction between Ag nanocubes and AuCl_(2)^(-).A mechanistic study of the reaction revealed that the formation of Au nanoframes relies on the diffusion of both Au and Ag atoms.The effect of the edge length and ridge thickness of the nanoframes on the localized surface plasmon resonance peak was explored by a combination of discrete dipole approximation calculations and single nanoparticle spectroscopy.With their hollow and open structures,the Au nanoframes represent a novel class of substrates for applications including surface plasmonics and surface-enhanced Raman scattering.
This paper gives a brief introduction to our recent works on photonic crystal(Ph C) cavities and related integrated optical structures and devices. Theoretical background and numerical methods for simulation of Ph C cavities are first presented. Based on the theoretical basis, two relevant quantities, the cavity mode volume and the quality factor are discussed. Then the methods of fabrication and characterization of silicon Ph C slab cavities are introduced. Several types of Ph C cavities are presented, such as the usual L3 missing-hole cavity, the new concept waveguide-like parallel-hetero cavity, and the low-index nanobeam cavity. The advantages and disadvantages of each type of cavity are discussed. This will help the readers to decide which type of Ph C cavities to use in particular applications. Furthermore, several integrated optical devices based on Ph C cavities, such as optical filters, channel-drop filters, optical switches, and optical logic gates are described in both the working principle and operation characteristics. These devices designed and realized in our group demonstrate the wide range of applications of Ph C cavities and offer possible solutions to some integrated optical problems.
We fabricate a series of periodic arrays of subwavelength square and rectangular air holes on gold films, and measure the transmission spectra of these metallic nanostructures. By changing some geometrical and physical parameters, such as array period, air hole size and shape, and the incident light polarization, we verify that both global surface plasmon resonance and localized waveguide mode resonance are influential on enhancing the transmission of light through nanostructured metal films. These two resonances induce different behaviours of transmission peak shift. The transmission through the rectangular air-hole structures exhibits an obvious polarization effect dependent on the morphology. Numerical simulations are also made by a plane-wave transfer-matrix method and in good consistency with the experimental results.
