Curved Gratings as Plasmonic Lenses for Linearly Polarised Light

The ability of curved gratings as sectors of concentric circular gratings to couple linearly polarized light into focused surface plasmons is investigated by theory, simulation and experiment. Curved gratings, as sectors of concentric circular gratings with four different sector angles, are etched into a 30-nm thick gold layer on a glass coverslip and used to couple linearly-polarised free space light at nm into surface plasmons. The experimental and simulation results show that increasing the sector angle of the curved gratings decreases the lateral spotsize of the excited surface plasmons, resulting in focussing of surface plasmons which is analogous to the behaviour of classical optical lenses. We also show that two faced curved gratings, with their groove radius mismatched by half of the plasmon wavelength (asymmetric configuration), can couple linearly-polarised light into a single focal spot of concentrated surface plasmons with smaller depth of focus and higher intensity in comparison to single-sided curved gratings. The major advantage of these structures is the coupling of linearly-polarised light into focused surface plasmons with access to and control of the plasmon focal spot, which facilitates potential applications in sensing, detection and nonlinear plasmonics.Comment: 15 pages and 12 figure

A delphinid petrosal bone from a gravesite on Ahu Tahai, Easter Island: taxonomic attribution, external and internal morphology.

International audienceIn this contribution, we describe the external and internal morphology of a delphinid petrosal bone collected from Ahu Tahai, a burial site located on the Southwestern coast of Easter Island, at Hangaroa. We discuss the taxonomic attribution of this archaeological item and describe its internal structures based on µCT data, including the bony labyrinth and the nerve and vein patterns. Identification of the nerves exists lead us to relocate the identification of the foramen singulare in delphinid petrosals