arXiv subjects

Traianos V. Yioultsis

Publications and source records attributed to Traianos V. Yioultsis.

4 recordsLinked to original sources

arXiv2026

Reconfigurable Graphene-Metasurface Analysis via an Eigenmode-Free Method-of-Lines Formulation

We present an eigenmode-free (EF) method-of-lines (MoL) formulation for the fast synthesis of reconfigurable graphene metasurfaces (MS). As the complexity of MSs increases, analysis by full-wave methods becomes challenging. The MoL is a considerably faster semi-analytical method where the electromagnetic equations are solved analytically along the direction perpendicular to the MS layers and numerically on the MS plane, thereby substantially decreasing the degrees of freedom (DoFs). In existing MoL formulations, the eigendecomposition of the system matrix is calculated numerically, which becomes computationally demanding for MSs with larger cross-sections. To overcome this limitation, we introduce an EF MoL that calculates the S-parameter matrix by analytical closed-form expressions. We demonstrate the potential of the EF MoL by analyzing a reconfigurable graphene MS absorber. The EF MoL shows excellent agreement in the absorbance and is two orders of magnitude faster than the finite element method.

physics.app-ph↗

arXiv2026

Eigenmode analysis of a half-mode uniplanar metamaterial-inspired substrate integrated waveguide

In this work, we systematically analyze the propagation characteristics of a new half-mode uniplanar substrate integrated waveguide (SIW) based on complementary split-ring resonators (CSRR), using a finite element method (FEM) eigenmode solver. The proposed half-mode CSRR SIW has a simpler fabrication than the SIW, since the via are substituted by CSRRs, and is more compact than the existing full uniplanar CSRR SIW, since its transverse size is reduced almost by half. To gain insight into the propagation characteristics of the proposed half-mode CSRR SIW and guide its synthesis process, we solve an eigenvalue problem that determines the complex propagation constant of the supported modes. By calculating the dispersion diagrams of the dominant mode, with all loss mechanisms included, we demonstrate that the half-mode uniplanar CSRR SIW retains the performance of the existing full CSRR SIW.

physics.app-ph↗

arXiv2021

Experimental demonstration of ultrathin broken-symmetry metasurfaces with controllably sharp resonant response

Symmetry-protected resonances can be made to couple with free space by introducing a small degree of geometric asymmetry, leading to controllably-sharp spectral response. Here, we experimentally demonstrate a broken-symmetry metasurface for the technologically important low millimeter wave spectrum. The proposed metasurface is fabricated on an ultrathin polyimide substrate, resulting in a low loss and flexible structure. Measurements inside an anechoic chamber experimentally verify the theoretically predicted sharp spectral features corresponding to quality factors of several hundreds. The demonstrated sharp response is also observed with the complementary structure which responds to the orthogonal linear polarization (Babinet's principle). The designed metasurfaces can be exploited in diverse applications favoured by a controllably-sharp spectral response, e.g., filtering, sensing, switching, nonlinear applications, in either reflection or transmission mode operation. More generally, the demonstrated fabrication process provides a generic platform for low-cost, large-scale engineering of metasurfaces with minimal substrate-induced effects.

physics.app-ph↗

arXiv2021

Asymmetric Si-slot Coupler with Nonreciprocal Response Based on Graphene Saturable Absorption

We present the study of a proof-of-concept integrated device that can be used as a nonlinear broadband isolator. The device is based on the asymmetric loading of a highly-confining silicon-slot photonic coupler with graphene layers, whose ultrafast and low-threshold saturable absorption can be exploited for nonreciprocal transmission between the cross-ports of the coupler. The structure is essentially a non-Hermitian system, whose exceptional points are briefly discussed. The nonlinear device is modeled with a coupled Schrodinger equation system whose validity is checked by full-vector finite element-based beam-propagation method simulations in CW. The numerically computed performance reveals a nonreciprocal intensity range (NRIR) in the vicinity of 100 mW peak power with a bandwidth spanning tens of nanometers, from CW down to ps-long pulses. Finally, the combination of saturable absorption and self-phase modulation (Kerr effect) in graphene is studied, indicating the existence of two NRIR with opposite directionality.

physics.optics↗