Twist Bilayer Photonic slab's Angle-DependentGuided Resonance Analysis based on Multiple Scattering

TL;DR

This paper introduces a modified RCWA method to analyze twisted bilayer photonic slabs, enabling eigenmode calculation and revealing angle-dependent resonance splitting, with potential applications in photonic device engineering.

Contribution

It presents a novel modified RCWA approach for eigenmode analysis and a simplified five-layer slab model for transmission, advancing the understanding of twisted bilayer photonic structures.

Findings

Eigenmodes can be calculated with the modified RCWA.

Moiré pattern causes resonance splitting.

Identifies two transmission phases explained by coupled-mode theory.

Abstract

We present an analysis of the transmission spectra of the twisted bilayer photonic slabs using a modified rigorous coupled wave (RCWA) analysis, where the evanescent bases are replaced by bases with non-zero flux density. By utilizing the modified RCWA we demonstrate the calculation of eigenmodes, which has not been realized before. To counter for the transmission property, we propose a five-layer uniform slab approximation, with an accuracy around 0.04a/c, which is more straightforward and accessible for optical engineers compared to work by Lou et al. [Phys. Rev. Lett. 126, 136101]. The moir\'e pattern perturbation induces a split of resonance, which show great potential for engineering the band structure. Moreover, We observe two distinct transmission phases: the angle-dependent phase and Fabry-P\'erot phase, which is explained by a coupled-mode theory (CMT) with expanded channels brought by the modified eigenmodes. Our work provides a theoretical framework for the design and optimization of twisted bilayer photonic devices.