Tunable topological edge state in plasma photonic crystals

In this work, we found a kind of edge state located at the interface between plasma photonic crystals (PPCs) and traditional photonic crystals, which depends on the property of the photonic band gap rather than the surface defect. Simulation and theoretical analysis show that by adjusting plasma density, we can change the topological characteristics of the photonic bandgap of PPCs, making it different from the photonic bandgap of traditional PCs, and thus excite or close the topological edge states. We further discussed the influence of plasma parameters on edge state characteristics, and the results showed that as the plasma density increased, the first photonic band gap (PBG) of the PPCs would be closed and then be reopened, resulting in band inversion and a change in the PBG properties of the PPCs. We can control the generation of edge states through plasma, and adjust the frequency and strength of the edge states. After the appearance of edge states, as the plasma density further increases, the first PBG of the PPCs will shift towards high frequencies and deepen. The frequency of edge states will shift towards higher frequencies, and their strength will also increase. We increased the first PBG depth of the PPCs by increasing the number of arrays, and found that when the number of the PPCs arrays increased, only the intensity of edge states would increase while the frequency remained unchanged. Therefore, flexible adjustment of edge states frequency and intensity can be achieved through the parameters of plasma density and array quantity. Our work demonstrates the properties of non-trivial edge states in plasma photonic crystals, which we believe can provide some guidance for applications based on edge states.