arXiv subjects

Emanuele Corsaro

Publications and source records attributed to Emanuele Corsaro.

4 recordsLinked to original sources

arXiv2026

Bode-Fano Limits to Broadband Absorption by Small Particles

Nanostructures can be designed to absorb light efficiently at resonance despite their subwavelength footprint, but causality and passivity fundamentally limit the bandwidth over which strong absorption can be maintained. Here we derive fundamental absorption-bandwidth limits for passive, causal, linear, and temporally dispersive subwavelength objects by rigorously casting electromagnetic scattering as an equivalent impedance-matching problem. This mapping yields ultimate Bode-Fano-type constraints for optical absorption and provides rational synthesis guidelines for the material dispersion of passive nanoparticles that can approach the bounds. Our results clarify the ultimate limits for broadband light harvesting and dissipation, with implications for solar-energy conversion, photothermal hyperthermia, thermal management, and related nanophotonic technologies.

physics.optics↗

arXiv2026

Exceptional Points in the Scattering Resonances of a Sphere Dimer

We investigate exceptional points of degeneracy (EPDs) in electromagnetic scattering of a sphere dimer from the electroquasistatic limit to the fully retarded regime. In the quasistatic limit, we prove that $\parity\trev$-symmetric configurations, realized by spheres with complex-conjugate susceptibilities, host EPDs. Beyond this limit, retardation breaks $\mathscr{PT}$-symmetry; nevertheless, by jointly tuning the material dispersion of the two spheres, we derive analytic synthesis conditions for realizing EPDs at \textit{real frequencies}. Near an EPD, we show that single-parameter perturbations yield the characteristic square-root splitting of the eigenfrequencies, and we quantify its impact on scattering, extinction, and absorption, clarifying sensing implications.

physics.optics↗

arXiv2026

QR-Recursive Compression of Volume Integral Equations for Electromagnetic Scattering by Large Metasurfaces

In this paper, a novel QR decomposition-based compression scheme is combined with a volume integral equations method for the fast and efficient numerical computation of the scattering of electromagnetic fields from large scale metasurfaces, via an iterative approach. The underlying problem is of a multiscale nature. Indeed, these metasurfaces are made of a large collection of interacting sub-wavelength scatterers, thus making the numerical computation of the solution very challenging. More specifically, the paper proposes a tailored version of a QR decomposition-based compression for a volume integral equation, together with a proper preconditioner that exploits the geometrical structure of the array, in order to achieve a fast and accurate iterative solver, in view of realistic applications. Numerical examples prove the effectiveness of the method in efficiently modeling metasurfaces made by thousands of particles.

math.NA↗

arXiv2024

Multilevel Fast Multipole Algorithm for Electromagnetic Scattering by Large Metasurfaces using Static Mode Representation

Metasurfaces, consisting of large arrays of interacting subwavelength scatterers, pose significant challenges for general-purpose computational methods due to their large electric dimensions and multiscale nature. This paper introduces an efficient boundary element method specifically tailored for metasurfaces, leveraging the Poggio-Miller-Chang-Harrington-Wu-Tsai (PMCHWT) formulation. Our method combines the Multilevel Fast Multipole Algorithm (MLFMA) with a representation of the unknown equivalent surface current density by means of static modes, a set of entire domain basis functions dependent only on object shape but independent of the material and frequency. The compression of the number of unknowns enabled by the Static Mode Representation (SMR), combined with the $\mathcal{O}(N \log N)$ complexity of MLFMA matrix-vector products, significantly reduces CPU time and memory requirements compared to classical MLFMA with RWG basis functions. We demonstrate the accuracy, time, and memory requirements of this method through several test cases including the full-wave simulation of a $100 λ\times 100 λ$ canonical metalens. The MLFMA-SMR method offers substantial benefits for the analysis and optimization of metasurfaces and metalenses.

physics.comp-ph↗