High-Q impurity photon states bounded by a photonic-band-pseudogap in an optically-thick photonic-crystal slab

TL;DR

This paper demonstrates that high-Q impurity photon states can be achieved in a 2D photonic-crystal slab without a full photonic band gap, by controlling in-plane modes through boundary feedback.

Contribution

It introduces a novel mechanism to attain high-Q impurity states in photonic crystals without requiring a complete band gap, using boundary feedback to suppress mode coupling.

Findings

Achieved Q factors over 10^5 in a 2D photonic-crystal slab.

Controlled in-plane mode density via boundary feedback.

Reduced coupling between impurity states and Bloch modes by over 40 times.

Abstract

We show that, taking a two-dimensional photonic-crystal slab system as an example, surprisingly high quality factors (Q) over 10^5 are achievable, even in the absence of a rigorous photonic-band-gap. We find that the density of in-plane Bloch modes can be controlled by creating additional photon feedback from a finite-size photonic-crystal boundary that serves as a low-Q resonator. This mechanism enables significant reduction in the coupling strength between the bound state and the extended Bloch modes by more than a factor of 40.