Surface plasmon illumination scheme for contact lithography beyond the diffraction limit

A novel local illumination scheme for optical lithography is proposed. It is based on the excitation of a surface plasmon on a metal film incorporated into a polymer light coupling mask for contact lithography. The electromagnetic field associated with the surface plasmon generates illumination volumes in the photoresist which are not limited by the diffraction (or Rayleigh) limit. Computer simulations indicate that the replication of 20 nm features using 630 nm illumination wavelength can be achieved with this technique. (C) 2003 Elsevier Science B.V. All rights reserved

A Green's tensor approach to the modeling of nanostructure replication and characterization

[1] We use the Green's tensor technique to study the optical processes taking place in configurations typically used for the replication and characterization of nanostructures. For the replication process we investigate light-coupling masks for optical contact lithography and for the characterization process the mode scattered by a defect or a short grating in a planar waveguide. Both configurations consist of structures embedded in a stratified background composed of a stack of material layers with different permittivities. We perform calculations for two-dimensional and three-dimensional structures and compare their optical behavior. Our results show that the additional material interfaces in three-dimensional systems can lead to significantly different field distributions and must be taken into account for a complete understanding of the electromagnetic properties of the systems

Electromagnetic resonances in individual and coupled split-ring resonators

We study experimentally and numerically the electromagnetic resonances in split ring resonators (SRRs), around 1 GHz. For an individual SRR, we show that both electric and magnetic fields can induce resonances, the magnetic one being the strongest. The utilization of such resonant structures as efficient microwave filter is also demonstrated. The coupling between two or more SRRs can be quite complex and strongly depends on their geometrical arrangement. For small separation distances, very strong coupling, leading to sharp resonances with high quality factors are observed. In that case a magnetic field circulation which connects neighboring elements is established. The practical implications of these results for the fabrication of a left-handed metamaterial are discussed. (C) 2002 American Institute of Physics

Efficient isotropic magnetic resonators

We study experimentally and numerically a novel three-dimensional magnetic resonator structure with high isotropy. It is formed by crossed split-ring resonators and has a response independent of the illumination direction in a specific plane. The utilization of such elements to build a finite left-handed medium is discussed. (C) 2002 American Institute of Physics

Strong Improvement of Long-Term Chemical and Thermal Stability of Plasmonic Silver Nanoantennas and Films

Silver (Ag) nanostructures and thin films are advantageous plasmonic materials as they have significantly lower losses than gold (Au). Unfortunately, Ag nanostructures suffer from poor chemical and thermal stability, which limit their applications. Here, the mechanisms leading to the deterioration of Ag nanostructures are clarified. It is first shown that oxygen alone cannot oxidize Ag nanostructures. Then, experiments using X-ray photoelectron spectroscopy reveal that the amount of sulfur in ambient air is too low for efficient tarnishing of the Ag surface. Finally, water is found to be the most critical factor for the degradation of Ag nanostructures and thin films. At high relative humidity, adsorbed water forms a thin film enabling the migration of Agions at the Ag/air interface, which deteriorates the Ag nanostructures. A dehydration treatment is developed which alters the morphology of the deposited silver, leading to an improved chemical and thermal stability of the Ag nanostructures and films, which then remain stable for more than 14 weeks under ambient laboratory conditions. In addition, dehydration also improves significantly the root-mean-square roughness for Ag thin films deposited on a glass substrate

Microwire arrays with plasmonic response at microwave frequencies

We study experimentally the response of three-dimensional arrays of microscopic wires. Very good agreement is found with previous theoretical work indicating that such a system can be considered as an effective plasmonic medium with a specific plasma frequency. The sample size threshold where this effective behavior appears is shown to be relatively small. (C) 2002 American Institute of Physics

Fluorescence resonant energy transfer in the optical near field

We develop a versatile theoretical framework for the study of fluorescence resonant energy transfer (FRET, or Forster transfer) in complex environments, under arbitrary illumination, including optical near fields. By combining the field-susceptibility formalism with the optical Bloch equations method, we derive general equations for the computation of the energy transfer between pairs of donor-acceptor molecules excited by optical near fields and placed in a complex geometry. This approach allows accounting for both the variations of the molecular population rates and the influence of the environment. Several examples illustrate the ability of the technique to analyze recent FRET experiments performed in the optical near field

Resonant optical antennas

We have fabricated nanometer-scate gold dipole antennas designed to be resonant at optical frequencies. On resonance, strong field enhancement in the antenna feed gap leads to white-light supercontinuum generation. The antenna length at resonance is considerably shorter than one-half the wavelength of the incident light. This is in contradiction to classical antenna theory but in qualitative accordance with computer simulations that take into account the finite metallic conductivity at optical frequencies. Because optical. antennas link propagating radiation and confined/enhanced optical fields, they should find applications in optical characterization, manipulation of nanostructures, and optical information processing

Atomic diffraction from nanostructured optical potentials

We develop a versatile theoretical approach to the study of cold-atom diffractive scattering from light-field gratings by combining calculations of the optical near-field, generated by evanescent waves close to the surface of periodic nanostructured arrays, together with advanced atom wavepacket propagation on this optical potential.Comment: 8 figures, 10 pages, submitted to Phys. Rev.