Quentin Lévesque

L-shaped metallic antenna for linear polarization conversion in reflection

The design of metasurfaces able to efficiently control the polarization state of an electromagnetic wave is of importance for various applications. We demonstrate both theoretically and experimentally that plasmonic planar L-shaped antennas can induce a 90° -rotation of the linear polarization of light with a nearly total efficiency in the infrared (3-5 µm). The influence of the in-plane geometry of the nanoantenna is investigated, and it is shown that it can be engineered so that the polarization conversion occurs over a 1 µm-wide spectral band ([3.25-4.25] µm) with a mean polarization conversion efficiency of 95%. These results are experimentally confirmed on two samples with distinctive geometries.

Plasmonic planar antenna for spectral and spatial manipulation of the polarization

The ability to control the polarization state of an electromagnetic wave thanks to plasmonic metasurfaces is at the core of many various applications. We demonstrate both theoretically and experimentally that plasmonic planar L-shaped antennas can induce a 90°-rotation of the linear polarization of light with a nearly total efficiency in the mid-wavelength infrared. Then, we generalize these results with V-shaped antennas that can induce any rotation of the linear polarization by engineering the in-plane geometry of the antenna.

Plasmonic planar antenna for wideband and efficient linear polarization conversion

The design of metasurfaces able to efficiently control the polarization state of an electromagnetic wave is of importance for various applications. We demonstrate both theoretically and experimentally that plasmonic planar L-shaped antennas can induce a 90◦-rotation of the linear polarization of light with a nearly total efficiency in the infrared (3-5 µm). The nanoantenna geometry is engineered so that the polarization conversion occurs over a 1 μm-wide spectral band ([3.25-4.25] µm ) with a mean polarization conversion efficiency of 95 %. In order to validate a theoretical model describing the antenna behaviour, we investigate the polarization conversion effect as function of the incident and azimuthal angles.

Huygens lens for angle compensation

Plasmonic lenses are based on complex combinations of nanoscale high aspect ratio slits. We show that their design can be greatly simplified, keeping similar performance while releasing technological constraints. The simplified system, called Huygens lens, consists in a central aperture surrounded by several identical single mode slits in a thin gold layer that does not rely anymore on surface plasmons. The focusing behaviour with respect to the position and number of slits is investigated, and we demonstrate the interest of this design to get compact array of lenses which are able to compensate the angle of incidence of the incoming wave.

Funneling of light in combinations of metal-insulator-metal resonators

We show both theoretically and experimentally that metal-insulator-metal resonators can be combined within the same subwavelength period and still behave independently. This permits to conceive surface with customizable absorption, which can for instance be used in dual band absorber or in omnidirectional wideband absorber. An energetic analysis can also be applied on these more complex antennas geometries, which highlights a sorting effect: at each resonance wavelength, the photons are funneled towards the apertures of the corresponding MIM cavity.

Energetic analysis of the plasmonic lens structure: a first step to simplification

Plasmonic lenses (PLs) are based on complex combination of various width nanoscale and high aspect ratio slits. We investigate a more simplified design keeping similar performances while releasing technological constraints. This simplification is based on an energetic analysis of the contribution of each slit relative to the entire PLs behaviour. We demonstrate that a simplified plasmonic lens (SPL) can be designed which has the same behaviours as PLs.