Mohamed Elsawaf | Searcharxiv

arXiv2026

A Low-Dispersion Depressed Core Waveguide for Dielectric Waveguide Interconnects

Dielectric waveguide (DWG) interconnects frequently utilize multimode waveguides due to their low dispersion in the fundamental mode. However, these links are more vulnerable to cross-modal coupling that significantly impacts their overall performance. This study presents a technique aimed at minimizing the coupling of energy into higher-order modes within weakly coupled rectangular dielectric waveguides that are excited by a linear taper. The approach involves wrapping the waveguide with a material of a higher dielectric constant than both the core and the cladding of the waveguide. The added material significantly improves the modal confinement factor of the fundamental mode to the core, leading to a much smaller coupling to the parasitic higher-order cladding modes. The new waveguide with the additional material cladding is analyzed, and semi-analytical approximate expressions are derived to predict the mode profiles and cutoffs. Design equations are given to choose the thickness of the wrapping material. The waveguide is fabricated and compared against a similar cross-section waveguide without the additional wrapping material. Unlike the unwrapped waveguide, the group delay (GD) results of the proposed (wrapped) waveguide closely match the EM-simulated GD of the fundamental mode, confirming the significant isolation of higher-order modes. The measured GD of the proposed DWG is 50 ps/m, while the expected fundamental mode GD from EM simulations is 35 ps/m. On the contrary, the unwrapped DWG shows a measured GD of 200 ps/m with significant oscillations, while the expected fundamental mode GD from EM simulations is 25 ps/m, demonstrating that wrapping the waveguide significantly improves the GD by reducing the higher-order mode propagation.

physics.app-ph↗

arXiv2026

Near Real-time Full-wave Inverse Design of Electromagnetic Devices

Inverse design enables automating the discovery and optimization of devices achieving performance significantly exceeding that of traditional human-engineered designs. However, existing methodologies to inverse-design electromagnetic devices require computationally expensive and time-consuming full-wave electromagnetic simulation at each iteration or generation of large datasets for training neural-network surrogate models. This work introduces the Precomputed Numerical Green Function method, an approach for ultrafast electromagnetic inverse design. The static components of the design are incorporated into a numerical Green function obtained from a single fully-parallelized precomputation step, reducing the cost of evaluating candidate designs during optimization to only being proportional to the size of the region under modification. A low-rank matrix update technique is introduced that further decreases the cost of the method to milliseconds per iteration without any approximations or compromises in accuracy. This method is shown to have linear time complexity, reducing the total runtime for an inverse design by several orders of magnitude compared to using conventional electromagnetics solvers. The design examples considered demonstrate speedups of up to 16,000x, shortening the design process from multiple days to weeks down to minutes. The approach enables practical and ultrafast design of complex structures that are prohibitively time-consuming for prior inverse design methods.

physics.comp-ph↗