Robust topological one-way edge states in radius-fluctuated photonic Chern topological insulators

Abstract

Recent developments in topological photonics have shown that the introduction of disorders can yield the innovative and striking transport phenomena. Here, we theoretically investigate topological one-way edge states in radius-fluctuated photonic Chern topological insulators (PCTIs), which are composed of two-dimensional gyromagnetic photonic crystals with cylinder site fixed but with cylinder radius fluctuated. We use a fluctuation index to characterize the degree of radius fluctuation, employ two empirical parameters to inspect the evolution of topological one-way edge states, and verify the stability of topological one-way edge states by calculating massive samples with various random numbers. We find that as the radius-fluctuation strength increases, there arises a competition between topological one-way edge state, Anderson localization state and trivial bulk state. We reveal that the Anderson localization state appears far more easily in the radius-fluctuation PCTI with even a weak strength compared with the position-perturbed PCTI with a strong randomness. We also demonstrate that the topological one-way edge states are protected against a strong fluctuation much larger than the fabrication errors in practical experiments. Our results show that the PCTIs consisting of gyromagnetic photonic crystals have a high-tolerance for the material and sample fabrication errors, and this would provide a deeper understanding of fundamental topology physics.

A Topological Multichannel Add-Drop Filter Based on Gyromagnetic Photonic Crystals

“…The results showed that the gap Chern number of Al 2 O 3 PC was 0, and thus the bandgap was trivial. Conversely, the gap Chern number in the second bandgap (between the second and third bands) of YIG PC was +1(or −1) when the EMF was −H 0 (or +H 0 ), which revealed that this bandgap was topologically nontrivial [54,55]. On the other hand, because the bandgap of Al 2 O 3 PC overlapped the second bandgap of YIG PC, the number of topological one-way edge states in the waveguide composed of these two PCs was equal to the difference of gap Chern numbers, and the propagation direction of topological one-way edge states was determined by the sign of gap Chern numbers.…”

Topological photonic states in gyromagnetic photonic crystals: Physics, properties, and applications

“…Moreover, as plotted in Figs. 2(e) and 2(f), Yang et al [77] and Chen et al [75] respectively demonstrated that chiral one-way edge states can exist in position-disordered and radius-fluctuated GPCs. The calculation results showed that photonic topological bandgaps are far more sensitive to disorders with a radius fluctuation than with a position randomness.…”

Topological Resistance-Free One-Way Transport in a Square-Hexagon Lattice Gyromagnetic Photonic Crystal

“…Additionally, it should be noted that the perturbation of the external magnetic field strength had almost no influence on the transport behavior of the one-way edge states (see more detailed calculations in the Supplemental Information ). Moreover, Chen et al also demonstrated that the realization of the one-way edge states in a GPC system has a very strong tolerance to the nonuniform magnetization [ 40 ].…”