High-Q localized states in finite arrays of subwavelength resonators

TL;DR

This paper presents a new physical mechanism to create high-Q localized states in finite arrays of subwavelength resonators, leading to significant enhancements in the Purcell factor and suppressed radiative losses.

Contribution

The paper introduces a novel interference-based mechanism for achieving giant Q-factors in finite resonator arrays, with specific design principles and demonstrated enhancements.

Findings

Q-factor scales as N^α with α ≈ 6.88

Up to 3400 Purcell factor enhancement

Suppression of multipole radiation up to N-th order

Abstract

We introduce a novel physical mechanism for achieving giant quality factors ($Q$-factors) in finite-length periodic arrays of subwavelength optical resonators. The underlying physics is based on interference between the band-edge mode and another standing mode in the array, and the formation of spatially localized states with dramatically suppressed radiative losses. We demonstrate this concept for an array of $N$ dipoles with simultaneous cancellation of multipoles up to $N$-th order and the $Q$ factor growing as $Q \propto N^{\alpha}$, where $\alpha \gtrsim 6.88$. Based on this finding, we propose a realistic array of Mie-resonant nanoparticles ($N \lesssim 29$) with a dramatic enhancement of the Purcell factor (up to $\sim $3400) achieved by tuning of the array parameters.