We propose using a strongly anisotropic dielectric as a substrate for a thin metallic film along the boundary of which surface plasmon excitations may propagate. We show that the propagation range of surface plasmons is increased if the substrate is a birefringent dielectric crystal with a properly oriented optical axis. The increase of the propagation range depends on the degree of anisotropy, and, consequently, it turns out to be small for substrates of natural optical crystals, where anisotropy is weak. However, in specially designed photonic crystals, the anisotropy may be very strong, thus leading to appreciable increase of the propagation range. A photonic-crystal substrate, being a medium with nonlinear dispersion, also affects the dispersion law of the surface plasmon. All these effects may be used in order to increase the efficiency of modern plasmonic and optoelectronic devices.

Nanoporous Cu4O3 – C composite thin films with spherical and bicontinuous elongated pore structure have been grown on stainless steel substrates by metalorganic chemical vapour deposition technique using a single source tetranuclear metalorganic complex as precursor. The guiding and confinement of light in these quasi-periodic structures has been investigated by glancing incidence (75°) infrared spectroscopy at room temperature. The transmittance spectra of these films between wave number 10000 – 400 cm−1 reveal light confinement modes in photonic band gap between 6127-8839 cm−1 and propagation modes between 5094-400 cm−1.

The optical properties of some nanoscale composites may deviate from that expected from a simple law of mixture of their individual components. In these cases the resulting structure can be considered to be a type of “metamaterial”. Here we explore some of the possibilities for nanoscale composite structures comprised of gold and VO2 – the latter being a functional material that undergoes a reversible insulator to metallic phase transition at 68°C. Two microstructures are examined: aggregates of gold nanoparticles surrounded by VO2 as the continuous phase, and its geometric inverse, mesoporous gold sponge with discontinuous VO2 inclusions. A composite, right-angled parallelepiped measuring 40×100×100 nm is taken as representative of the mixture, and calculations of the optical properties performed using the discrete dipole approximation code of Draine and Flatau. The VO2 matrix strongly attenuates the dipole-dipole plasmon resonance of the gold structure, and thermochromic switching of the remaining plasmon resonance occurs

A series of frequency-selective surface (FSS) arrays based on nested split-ring triangle resonators have been fabricated using screen printing. A silver-filled polymer thick film (PTF) paste was selected as the active medium for the FSS arrays as it has good compatibility with the various substrates employed and is in itself naturally flexible. Substrates included FR4 boards and polyimide (PI), polyethylene terephthalate (PET) and silicone sheeting. Compared to arrays fabricated from Cu-clad FR4 board, the screen-printed arrays are resonance shifted owing to the magnitude of the dielectric constant and thickness of the various substrates. In addition, the quality factors of the screen-printed arrays are reduced compared to those fabricated from the more conductive Cu resonators. Despite these limitations, screen-printed arrays have considerable potential as components for low-cost flexible and conformal microwave devices.

By reduction of SiO2 opal in atmosphere of nitrogen (80%)-helium (15%)-hydrogen (5%) gas mixture at various temperatures we tuned the dielectric contrast ratio and band gap of photonic crystal (PC) up to 10 %. The SEM images dose not show any detectible change in lattice parameters, whereas the elemental analysis shows remarkable decrease of oxygen content. The shift of reflectance spectra toward the long wavelength and increase of transmission in infrared region confirm the redaction of silica and partial transformation to the silicon.

Novel two and three-dimensional doubly negative metamaterials (DNM), viz. metamaterial with simultaneously negative permittivity, permeability, and index of refraction, are introduced. The metamaterials comprise deeply subwavelength periodic unit cells, can be tuned to operate in the near infra-red and visible spectra, and can be manufactured using standard nanofabrication methods with compatible materials. The DNMs' unit cell comprises an optically thin metal film sandwiched between two thin metal strips or patches residing at a small distance from the film. The cavity formed between the strips or patches supports resonances with magnetic and electric response that can be tuned to exist in overlapping frequency bands thus leading to the DNM operation.

Scaling the performance of metamaterials to obtain negative refractive index at optical frequencies has been of great interest. One of the great barriers to the scaling is that real currents cannot be driven at very high frequencies and one is more dependent on displacement currents to generate negative magnetic permeability. Moreover to keep the dimensions of the metamaterials physically accessible, the structural lengthscales of the metamaterials begin approach the wavelength of the radiation in free space and homogenisation is often questionable. Here we will show that metamaterials such as Split ring resonators in these high frequency limits exhibit complex behaviour. Magnetic activity and Negative refractive index behaviour can, indeed, be obtained at optical frequencies but will need to be interpreted very carefully. The plasmonic nature of the metallic system and excitation needs to be considered in detail.

We have investigated the thermo-optical properties of gold NPs embedded in an ice matrix [1]. Resonant laser light of relatively weak intensity is able to melt ice with embedded Au NPs, whereas even a very intense laser beam does not melt ice alone. This comes from strong absorption in Au NPs in the regime of plasmon resonance. By recording time-resolved Raman signals, we observe the melting process and determine the threshold melting power , where is the background temperature. We also observe relatively large scattering in the threshold laser intensity that leads to melting of the ice because of the mesoscopic nature of the sample. We can understand this observation using the TEM images of NPs, showing that geometry of NP complexes varies greatly. In our recent theoretical paper we showed that the local temperature inside and around a NP complex depends strongly on its geometry, and this leads to large scattering for the measured as a function of the reduced temperature, for different complexes [2].

We recently discovered that NPs immobilized on glass surfaces can be characterized by single particle spectroscopy. Single and small NP clusters can be discriminated using the integrated intensity of the plasmon emission band. A cluster of four gold NPs has ∼ 4 times the intensity of a single gold NP. When the NPs are aggregated into a cluster then broadening of the intensity profile plot is not observed Gold NPs that are not clustered together but are found within the excitation volume will lead to a broadening of a cross sectional slice. We will use these principles to determine the amount of heat generation from single and clustered gold NPs.

[1] H. H. Richardson, Z. N. Hickman, A. O. Govorov, A. C. Thomas, W. Zhang, M. E. Kordesch, Nano Lett. (2006); DOI: 10.1021/nl060105l.

[2] A. O. Govorov, H. H. Richardson, W. Zhang, and T. Skeini, Nanoscale Res. Lett. 1, 100101 (2005).