arXiv subjects

Fabrice Pardo

Publications and source records attributed to Fabrice Pardo.

4 recordsLinked to original sources

arXiv2022

Lorentz-invariant topological structures of the electromagnetic field in a Fabry-Perot resonant slit-grating

It is commonly assumed that the most correct description of the electromagnetic world is the abstract one, and that topological constructs such as lines of force are not covariant. In the present paper, we show that for a $y$-invariant system with a $p$-polarized electromagnetic field, it is possible to construct absolute (i.e. Lorentz invariant) lines, which we call electric spaghettis (ESs). The electromagnetic field is fully described by the ES topology that transcend the limit between space and time, plus a new invariant, the characteristic parameter $η$. In a Fabry-Perot resonant slit-grating, three ES patterns can be distinguished, corresponding to three regions: null straight lines in plane wave regions, rounded rhombuses in the interference region inside the grating, and Bernoulli's logarithmic spiral patterns - the first ever described fractals - in the funneling region.

physics.optics↗

arXiv2019

Designing Metagratings Via Local Periodic Approximation: From Microwaves to Infrared

Recently, metamaterials-inspired diffraction gratings (or metagratings) have demonstrated unprecedented efficiency in wavefront manipulation by means of relatively simple structures. Conventional one-dimensional (1D) gratings have a profile modulation in one direction and a translation symmetry in the other. In 1D metagratings, the translation invariant direction is engineered at a subwavelength scale, which allows one to accurately control polarization line currents and, consequently, the scattering pattern. In bright contrast to metasurfaces, metagratings cannot be described by means of surface impedances (or local reflection and transmission coefficients). In this paper, we present a simulation-based design approach to construct metagratings in the "unit cell by unit cell" manner. It represents an analog of the local periodic approximation that has been used to design space-modulated metasurfaces and allows one to overcome the limitations of straightforward numerical optimization and semianalytical procedures that have been used to date to design metagratings. Electric and magnetic metagrating structures responding to, respectively, transverse electric and transverse magnetic incident plane waves are presented to validate the proposed design approach.

physics.app-ph↗

arXiv2014

Giant field enhancement by funneling effect into sub-wavelength slit-box resonators

Inspired by the acoustic Helmholtz resonator, we propose a slit-box electromagnetic nanoantenna able to concentrate the energy of an incident beam into surfaces a thousand times smaller than with a classical lens. This design gives birth to giant field intensity enhancement in hot volume, throughout the slit. It reaches $10^4$ in the visible up to $10^8$ in the THz range even with focused beams thanks to an omnidirectional reception. These properties could target applications requiring extreme light concentration, such as SEIRA, non-linear optics and biophotonics.

physics.optics↗

arXiv2011

Light funneling mechanism explained by magneto-electric interference

We investigate the mechanisms involved in the funneling of the optical energy into sub-wavelength grooves etched on a metallic surface. The key phenomenon is unveiled thanks to the decomposition of the electromagnetic field into its propagative and evanescent parts. We unambiguously show that the funneling is not due to plasmonic waves flowing toward the grooves, but rather to the magneto-electric interference of the incident wave with the evanescent field, this field being mainly due to the resonant wave escaping from the groove.

cond-mat.other↗