SOI-Compatible Degenerate Band Edge Photonic Structure: Design Rules and Robustness Analysis

TL;DR

This paper presents a design for a Silicon-on-Insulator-compatible photonic structure exhibiting a degenerate band edge, with analysis of its dispersion, spectral properties, and robustness, advancing applications in photonics.

Contribution

It introduces a novel coupled waveguide structure with practical design guidelines for achieving a degenerate band edge in SOI-compatible photonics.

Findings

The structure achieves a flat dispersion band at the DBE.

Resonance quality factor scales favorably with unit cells.

The design demonstrates robustness against fabrication imperfections.

Abstract

Optical periodic structures exhibiting a degenerate band edge (DBE) are of significant interest for various applications such as switching, sensing, high-power amplification, and lasing. At the edge of the bandgap in such structures, a fourth-order exceptional point degeneracy arises, leading to an extremely flat dispersion band. We propose and study a Silicon-on-Insulator-compatible structure composed of two coupled waveguides with asymmetric gratings. The dispersion relations and the field profiles are obtained using three-dimensional finite-difference time-domain simulations, and we provide a set of practical guidelines for the design and optimization of such structures, in order to obtain a DBE. We analyze the transmission and reflection spectra of finite-size devices, and investigate their spectral properties near the stationary points. The scaling of the resonance quality factor with the number of unit cells is studied, revealing a performance that surpasses that of conventional periodic structures. Finally, we examine the robustness of the DBE with respect to fabrication tolerances and structural imperfections.