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Plasmonic planar antenna for wideband and efficient linear polarization conversion

We demonstrate both theoretically and experimentally that plasmonic planar L-shaped antenna can nearly totally convert the linear polarization of light with a high efficiency in the infrared (3–5 μm). The nanoantenna geometry is engineered so that the polarization conversion occurred on a 1 μm-wide band ([3.25–4.25] μm) with a mean polarization conversion ratio of 95%. We show that this effect is due to two localized resonances in the L-shaped antenna, which wavelengths are tunable with the in-plane geometry of the nanoantenna. Eventually, the angular independence of the polarization conversion effect is evidenced.

APL_Convertisseur_Fig1.png APL_Convertisseur_Fig2.png APL_Convertisseur_Fig3.png
a) Scheme of the array of L-shaped MIM antenna. (b) 45° tilted SEM image of a fabricated L-shaped MIM antenna Reflectivity spectra of an x-polarized plane wave impinging on at an incidence of 13° measured (solid lines) and computed (dashed lines). Maps of the normalized electric field intensity |Ex|2/|Eo|2 and |Ey|2/|Eo|2 at (b) λ1=3.4 μm and (c) λ2=4.2 μm. Reflectivity diagram for (a) R// and (b) R as a function of the angle of incidence. (c) Polar plot of experimental values (red crosses) and computed values (solid line) of the mean PCR on the band [3.25–4.25] μm

Contact: Jean-Luc Pelouard (jean-luc.pelouard@lpn.cnrs.fr)
Further reading: Q. Lévesque et al. Appl. Phys. Lett. 104 111105 (2014)