Understanding the physics in multiple-state open systems is critical many fields of physics. A study an ensemble connected lossy cavities shows how eigenstates can coalesce to produce new higher-order singularities.

The physics of a photonic structure is commonly described in terms its apparent geometric dimensionality.On the other hand, with concept synthetic dimension, it fact possible to explore space dimensionality that higher as compared geometrical structures.In this review, we discuss basic concepts dimension photonics, and highlighting various approaches towards demonstrating such for fundamental potential applications.

Abstract Recently, we witnessed a tremendous effort to conquer the realm of acoustics as possible playground test with topologically protected sound wave propagation. In this article, review latest efforts explore waves topological states quantum matter in two- and three-dimensional systems where discuss how spin valley degrees freedom appear highly novel ingredients tailor flow form one-way edge modes defect-immune acoustic waves. Both from theoretical stand point based on contemporary...

Making heat stand still Dissipative oscillating systems (waves) can be described mathematically in terms of non-Hermitian physics. When parity-time symmetric have dissipative components, the interplay between gain and loss lead to unusual exotic behavior. Li et al. show theoretically demonstrate experimentally that such behavior need not limited wave systems. Looking at diffusion heat, they devised an experimental setup comprising two thermally coupled disks rotating opposite directions. The...

Surface impedance of a photonic material governs how an impinging light wave behaves at its surface, whereas bulk ``band structure'' determines what modes can propagate in it. Is there surface-to-bulk correspondence? A new study one-dimensional crystals indeed uncovers rigorous fundamental relationship between the two.

We introduce an implementation of a Laplace differentiator based on photonic crystal slab that operates at transmission mode. show the can be implemented provided guided resonances near $\Gamma$ point exhibit isotropic band structure. Such device may facilitate nanophotonics-based optical analog computing for image processing.

Abstract Weyl points, as monopoles of Berry curvature in momentum space, have captured much attention recently various branches physics. Realizing topological materials that exhibit such nodal points is challenging and indeed, been found experimentally transition metal arsenide phosphide gyroid photonic crystal whose structure complex. If realizing even the simplest type single nodes with a charge 1 difficult, then making real carrying higher charges may seem more challenging. Here we...

A quadrupole topological insulator, being one higher-order insulator with nontrivial quantization, has been intensely investigated very recently. However, the tight-binding model proposed for such emergent insulators demands both positive and negative hopping coefficients, which imposes an obstacle in practical realizations. Here we introduce a feasible approach to design sign of acoustics, construct first acoustic that stringently emulates model. The inherent hierarchy topology...

Abstract Weyl points, as a signature of 3D topological states, have been extensively studied in condensed matter systems. Recently, the physics points has also explored electromagnetic structures such photonic crystals and metamaterials. These typically complex three-dimensional geometries, which limits potential for exploring point on-chip integrated Here we show that emerges system two-dimensional arrays resonators undergoing dynamic modulation refractive index. In addition, phase can be...

Bound states in the continuum (BICs) confine resonances embedded a continuous spectrum by eliminating radiation loss. Merging multiple BICs provides promising approach to further reduce scattering losses caused fabrication imperfections. However, date, BIC merging has been limited only $\mathrm{\ensuremath{\Gamma}}$ point, which constrains potential application scenarios such as beam steering and directional vector beams. Here, we propose new scheme construct at almost an arbitrary point...

Bound states in the continuum (BICs) can confine light with a theoretically infinite Q factor. However, practical on-chip resonators, scattering loss caused by inevitable fabrication imperfection leads to finite factors due coupling of BICs nearby radiative states. Merging multiple improve robustness against improving over broad wavevector range. To date, studies merging have been limited fundamental topological charges ±1. Here we show unique advantages higher-order (those charges)...

Abstract External encapsulation technique as a straightforward craft process has been adopted to prevent the infiltration of moisture and oxygen, thereby improving environmental stabilities lead halide perovskite solar cells (PSCs). However, irreversible light‐induced degradation originating from various vacancies ion diffusion or migration inside device cannot be efficiently solved by external encapsulation. Herein, an internal strategy introducing NbCl 5 at buried tin oxide/perovskite...

The era of Big Data requires nanophotonic chips to have large information processing capacity. Multiple frequency on-chip devices are highly desirable for density integration, but such more susceptible structural imperfection because their nano-scale. Topological photonics provides a robust platform next-generation chips. Here we give an experimental report topological rainbow realized by employing translational deformation freedom as synthetic dimension. can separate, slow, and trap...

We report the existence of Weyl points in a class noncentral symmetric metamaterials, which has time reversal symmetry, but does not have inversion symmetry due to chiral coupling between electric and magnetic fields. This metamaterial exhibits either type-I or type-II depending on its nonlocal response. also provide physical realization such consisting an array metal wires shape elliptical helices points.

Metamaterials with an effective zero refractive index associated their electromagnetic response are sought for a number of applications in communications and nonlinear optics. A promising way that this can be achieved all-dielectric photonic crystals is through the design Dirac cone at Bloch wave vector band structure. In optical frequency range, natural to implement use crystal slab. existing implementation, however, zero-index modes also radiate strongly into environment due intrinsic...

We provide a systematic study of non-Hermitian topologically charged systems. Starting from Hermitian Hamiltonian supporting Weyl points with arbitrary topological charge, adding perturbation transforms the to one-dimensional exceptional contours. analytical prove that charge is preserved on In contrast systems, addition gain and loss allows for new class phase transition: when two oppositely contours touch, can dissipate without opening gap. These effects be demonstrated in realistic...

The concept of synthetic dimensions, which has enabled the study higher-dimensional physics on lower-dimensional physical structures, generated significant recent interest in many branches science ranging from ultracold-atomic to photonics, since such a provides versatile platform for realizing effective gauge potentials and novel topological physics. Previous experiments demonstrating this have augmented real-space dimensionality by one additional dimension. Here we endow single ring...

We study the topological edge plasmon modes between two "diatomic" chains of identical plasmonic nanoparticles.Zak phase for longitudinal in each chain is calculated analytically by solutions macroscopic Maxwell's equations particles quasi-static dipole approximation.This approximation provides a direct analogy with Su-Schrieffer-Heeger model such that eigenvalue mapped to frequency dependent inverse-polarizability nanoparticles.The state found be same as single-particle resonance frequency,...