Discontinuities in photonic waveguides: rigorous Maxwell-based 3D modeling with the finite element method

Abstract

In this paper, we present a general framework to study rigorously discontinuities in open waveguides using a full vector description given by Maxwell's equations and using the finite element method. The discontinuities are not necessarily a small perturbation of the initial waveguide and can be very general, such as plasmonic inclusions of arbitrary shape. The leaky modes of the invariant structure are computed first ; then serve as incident fields on the full structure with obstacles using a scattered field approach ; the resulting scattered field is finally projected on the modes of the invariant structure making use of their bi-orthogonality. A complete energy balance is performed. Finally, the modes open waveguides periodically structured along the propagation direction are computed we compare the relevant complex propagation constants to the transmission obtained for a finite number of identical cells. The relevance and complementarity of the two approaches are highlighted on a numerical example encountered in infrared sensing. Finally, open source models allowing to retrieve most of the results of this paper are provided.

Complete design of an efficient and fully integrated graphene-based compact plasmon coupler for the infrared

“…In order to model the full device accurately and rigorously, the method we have recently developped to study discontinuities in waveguides within a full vector description given by Maxwell's equations is used [8]. It doesn't rely on any hypothesis regarding the sizes, the shapes or the permittivities of the discontinuities, without any approximation as long as only linear materials are considered.…”

Surface Functionalization with Polymer Membrane or SEIRA Interface to Improve the Sensitivity of Chalcogenide-Based Infrared Sensors Dedicated to the Detection of Organic Molecules

“…To realize the SEIRA chalcogenide sensors, a theoretical study was performed to design single-mode structures in the MIR and to optimize the evanescent part of the waveguide modes. , Indeed, the 3D model described the section of the waveguide before the region containing the transducers (i.e., metallic particles arranged on the surface of the waveguide for mid-infrared detection), the transducer region itself, and the downstream part of the selenide waveguide. To fabricate depicted SEIRA integrated sensor, the gold nanoplots deposited by LIL on the surface of the planar chalcogenide guides were locally etched with argon plasma.…”

Supplementary document for Complete design of a fully integrated graphene-based compact plasmon coupler for the mid-infrared - 5464852.pdf

“…To implement the finite element method (FEM) formalism we developped we used the open source softwares gmsh and getdp [2,3]. Complementary details about the FEM can be found in our references [4][5][6].…”