Stealthy-Hyperuniform Wave Dynamics in Two-Dimensional Photonic Crystals

TL;DR

This paper investigates wave propagation in two-dimensional photonic crystals with stealthy-hyperuniform disorder, revealing how such structures can suppress scattering and exhibit unique optical properties due to their spectral characteristics.

Contribution

The study provides experimental evidence of scattering behavior in stealthy-hyperuniform photonic structures and links it to their spectral properties and non-Hermitian effects.

Findings

Sharp transition in linewidths at the stealthy regime boundary

Multiple scattering leads to reduced transparency in stealthy structures

Residual scattering caused by non-Hermitian effects from radiative loss

Abstract

Hyperuniform structures are spatial patterns whose fluctuations disappear on long length scales, making them effectively homogeneous when observed from afar. Mathematically, this means that their spectral density, $\tilde{\rho}({\bf k})$, approaches zero for low wavenumber, $|\textbf{k}|$. Crystalline lattices are hyperuniform, as are certain quasicrystals, maximally random jammed packing of spheres, and electrons in the fractional quantum Hall state. Stealthy-hyperuniformity is an even stronger constraint on the spectral density: it requires that $\tilde{\rho}({\bf k})$ is strictly zero in a finite range of wavevectors around $\mathbf{k}=\mathbf{0}$, called the stealthy regime, or exclusion region. Since the degree of scattering by disorder is, to leading order, proportional to $\tilde{\rho}({\bf k})$, waves propagating through such structures may do so without scattering for sufficiently long wavelengths and short distances. Here, we measure scattering by disorder in photonic crystal slabs with stealthy-hyperuniform disorder by measuring the linewidths of the photonic bands. We observe the transition between the stealthy and non-stealthy regimes, marked by a sharp increase in linewidth. We also observe the effects of multiple scattering in the stealthy regime, which implies diminishing transparency. Moreover, we show that residual single scattering in the stealthy regime arises from an intrinsically non-Hermitian effect: propagating light has a complex effective mass due to radiative loss out of the slab.