Observation of a Topological Edge State in the X‐ray Band

Abstract

The possibility of obtaining edge states of light that are robust against disorder by mimicking the topological properties of a solid-state system has brought a profound impact on optical sciences. In the short-wavelength region, X-ray science and technology is undergoing tremendous development. It requires high-precision optics with exquisite control of light properties and robustness against structural perturbations. Therefore, it is very attractive to extend the concept of optical topological manipulation to the X-ray regime. Herein, the topological edge state is theoretically proposed and experimentally demonstrated at the interface of two kinds of photonic crystals having different bandgap topological characteristics in the X-ray regime. Remarkably, this topologically protected edge state is immune to the thickness disorder as long as the zero-average-effective-mass condition is satisfied. This work extends the topological photonics to the X-ray regime and paves the way for the development of novel X-ray optics such as high-resolution X-ray filters/monochromators, or X-ray quantum optics, to realize the phenomena such as Rabi splitting that are robust against disorders.

Hyperbolic metamaterials: From dispersion manipulation to applications

“…EMT is a quasi-static approximation. This theory may be invalid when the optical nonlocal effect exists in the system [161]. For example, this approximation may be destroyed when surface plasmons (SPPs) are excited or when the unit-cell size is not in the sub-wavelength scale.…”

Robust and Broadband Optical Coupling by Topological Waveguide Arrays

“…Topological photonics has arrested a great deal of interest with intriguing optical phenomena associated with the topological edge states (TESs) . Nontrivial TESs have been well revealed in two‐dimensional (2D) photonic topological insulators, which demonstrated very good robustness to structural defects or scatterers with one‐way propagations .…”

“…There are also 1D topological systems that have edge states that exist at the termination of a 1D lattice. For example, zero modes in the Su–Schriffer–Heeger (SSH) model have gained significant attention and have been explored in many different systems . All the progress in fundamental researches of topological photonics has recently prompted great efforts to design robust optical devices that are insensitive to structural perturbations and fabrication disorders.…”

Rotation controlled topological edge states in a trimer chain composed of meta-atoms

“…The edge states of a finite SSH chain will be distributed at both ends of the chain. Moreover, edge states with topological protection are immune to the fabrication error of the chain, which have been used to realize many applications, such as the topological lasers [27][28][29], filter [4], sensors [30,31], and wireless power transfer (WPT) [32][33][34]. Normally, the construction of SSH chain in optical systems needs to change the separation of adjacent resonators or waveguides.…”