Obstructive micro diffracting structures as an alternative to plasmonics nano slits for making efficient microlenses.

Miniature optical components at the wavelength scale remain today a theoretically opened challenging problem of great technological interest. Appart from refractive micro-optics, plasmonics have been proposed to realize micro lenses with properly designed planar metallic nano-patterns. We show in this paper that efficient light focusing at the diffraction limit with higher transmission can be obtained with micro-structures much easier to fabricate than nano ones, such as a simple micro-slit studied here as an example.

Metallic nanowires can lead to wavelength-scale microlenses and microlens arrays.

We theoretically and experimentally demonstrate that the diffraction of microstructures based on silver nanowires leads to very efficient microfocusing effects. Pairs of parallel nanowires act as ultrasmall cylindrical microlenses with diffraction-limited resolution in the Fresnel region. This is a new diffraction scheme to make micron-sized optical lenses with higher transmittance than plasmonic microlens based on nano-aperture arrays.

Gold hollow spheres obtained using an innovative emulsion process: towards multifunctional Au nanoshells.

The tremendous development of materials with fine tuning of their composition, shape, size and chemical functionalities at the nanometer scale has opened a wide range of applications, particularly in medicine. Metallic nanoparticles are extremely interesting for such developments. The fundamental study of surface plasmon resonance (SPR) versus the shape/size of a particle is an important challenge.