scholarly journals Reconfigurable Topological Phases in Two-Dimensional Dielectric Photonic Crystals

Crystals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 221 ◽  
Author(s):  
Hongbo Huang ◽  
Shaoyong Huo ◽  
Jiujiu Chen
Keyword(s):  
Photonic Crystals ◽  
Lattice Structure ◽  
Topological Defects ◽  
Topological Phases ◽  
Two Dimensional ◽  
Edge States ◽  
Microwave Frequencies ◽  
Potential Applications ◽  
Microwave Photon ◽  
Elliptical Cylinders

The extensive research on photonic topological insulators has opened up an intriguing way to control electromagnetic (EM) waves. In this work, we numerically demonstrate reconfigurable microwave photon analogues of topological insulator (TIs) in a triangular lattice of elliptical cylinders, according to the theory of topological defects. Multiple topological transitions between the trivial and nontrivial photonic phases can be realized by inhomogeneously changing the ellipse orientation, without altering the lattice structure. Topological protection of the edge states and reconfigurable topological one-way propagation at microwave frequencies, are further verified. Our approach provides a new route towards freely steering light propagations in dielectric photonic crystals (PCs), which has potential applications in the areas of topological signal processing and sensing.

Two-dimensional Topological Photonic Crystals with Helical Edge States below the Light Line

2021 ◽  
Author(s):  
Chengkun Zhang ◽  
Hironobu Yoshimi ◽  
Yasutomo Ota ◽  
Satoshi Iwamoto
Keyword(s):  
Photonic Crystals ◽  
Two Dimensional ◽  
Edge States ◽  
Light Line

Fragile topology based helical edge states in two-dimensional moon-shaped photonic crystals

2020 ◽  
Vol 102 (24) ◽  
Author(s):  
Zhongfu Li ◽  
Hsun-Chi Chan ◽  
Yuanjiang Xiang
Keyword(s):  
Photonic Crystals ◽  
Two Dimensional ◽  
Edge States

Dual modulation of topological edge states from two-dimensional photonic crystals with lattice shrink

2021 ◽  
pp. 2150236
Author(s):  
Xiao-Xue Li ◽  
Yun-Tuan Fang ◽  
Li-Xia Yang
Keyword(s):  
Photonic Crystals ◽  
Edge State ◽  
Wide Bandgap ◽  
Two Dimensional ◽  
Edge States ◽  
Source Position ◽  
State Structure ◽  
Intense Field ◽  
Flat Edge ◽  
Field Localization

The current topological edge states lack dynamical modulation and the intense field localization effect. To solve these problems, we construct a topological edge state structure based on two-dimensional photonic crystals with lattice shrink. Through the optimization of structure parameters, a nearly flat edge state dispersion curve occurs in a wide bandgap. The topological edge states with intense field localization take on some unique properties such that the transport directions can be controlled by both the source spin and the source position. The transport modes can be dynamically switched between the two opposite unidirectional channels just through moving the source position.

Fabrication of Two-Dimensional Photonic Crystals on N-Type Silicon Substrate Using Holographic and Wet Etching Techniques

2007 ◽  
Author(s):  
Han Lin ◽  
Shou Liu ◽  
Xiangsu Zhang
Keyword(s):  
Porous Silicon ◽  
Photonic Crystals ◽  
Silicon Substrate ◽  
Lattice Structure ◽  
Hexagonal Lattice ◽  
Cost Effective ◽  
Wet Etching ◽  
Etching Time ◽  
Two Dimensional ◽  
Photoresist Mask

Technique of fabricating two-dimensional (2D) photonic crystals (PCs) in silicon wafers using the combination of holographic lithography and wet etching is described in the paper. The fabricated silicon material is suitable to be used as porous silicon for Ge/Si quantum dots growth or other applications. Single exposure holographic method was adopted to fabricate the photoresist mask with the pattern of 2D hexagonal lattice structure. HF:HNO3:CH3COOH = 4:4:3 solution was used to etch circular pores with bowl-shaped bottom into silicon substrate at room temperature with 30 s etching time. Periodic structure in silicon with 1 μm lattice constant and 200 nm pore depth was obtained in the experiment. The fabrication process is fast and cost-effective thus having the potential for industrial mass production of porous silicon.

scholarly journals Antiferromagnetic topological crystalline insulator and mixed Weyl semimetal in two-dimensional NpAs monolayer

2021 ◽  
Author(s):  
Xiaorong Zou ◽  
Ning Mao ◽  
Bingyang Li ◽  
Wenli Sun ◽  
Baibiao Huang ◽  
...  
Keyword(s):  
Anomalous Hall Effect ◽  
Topological Classification ◽  
Two Dimensional ◽  
Edge States ◽  
Magnetization Direction ◽  
Weyl Semimetal ◽  
Potential Applications ◽  
Topological States ◽  
Quantum Phenomena ◽  
Topological Crystalline Insulator

Abstract Magnetic topological states have attracted significant attentions due to their intriguing quantum phenomena and potential applications in topological spintronic devices. Here, we propose a two-dimensional material NpAs monolayer as a candidate for multiple topological states accompanied with the changes of magnetic structures. Under the antiferromagnetic configuration, the long-awaited topological crystalline insulator (TCI) emerges with a nonzero mirror Chern number $\mathcal{C_M} = 1$ and a giant band gap of 630 meV, and remarkably a pair of gapless edge states can be tailored by rotating the magnetization directions while the TCI phase survives. Moreover, we establish the existence of quantum anomalous Hall effect and nontrivial nodal points under the ferromagnetic configuration, thereby giving rise to the mixed Weyl semimetal after adding the magnetization direction to topological classification. Our findings not only provide an ideal candidate for uncovering exotic topological characters with magnetism but also put forward potential applications in topological spintronics.

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