Giant resonance and anomalous quality factor scaling in coupled resonator optical waveguides at the degenerate band edge

TL;DR

This paper introduces a new method to significantly increase the quality factor of coupled resonator optical waveguides near a degenerate band edge, enabling stronger fields and improved device performance.

Contribution

It demonstrates a novel scaling law for Q factor enhancement at the degenerate band edge, even with losses and perturbations, surpassing single resonator performance.

Findings

Q factor can be engineered to exceed single ring resonators.

Scaling law shows giant Q factor enhancement at the DBE.

Enhanced fields enable applications in sensing and nonlinear optics.

Abstract

We propose a novel scheme for enhancing the quality factor of coupled resonators optical waveguides (CROWs) when operating near a degenerate band edge (DBE). A DBE is a four-mode exceptional point of degeneracy (EPD) occurring when four Bloch eigenmodes coalesce providing a resonance condition with a giant enhancement in fields. We report an unprecedented scaling law of quality factor of CROWs when operating at the DBE, even in the presence of losses and structural perturbations. Remarkably, the Q factor of the proposed CROW can be engineered to exceed that of a single ring resonator having a diameter equal to the CROW length, hence having an overall strong area reduction. The findings reported in this letter are critical for enhancing fields amplitudes to giant levels and the Q factor of ring resonators and are very beneficial for various applications including four wave mixing, Q switching, lasers, and highly sensitive sensors.