Tunable omnidirectional band gap properties of 1D plasma annular periodic multilayer structure based on an improved Fibonacci topological structure

In this paper, the characteristics of the omnidirectional band gap (OBG) for one-dimensional plasma cylindrical photonic crystals based on an improved Fibonacci topological structure are researched. The influences of the azimuthal mode number (m), incident angle (θ), plasma thickness (d_p), and plasma frequency (ω_p) on the OBG are discussed. These conclusions are drawn that m has a strong ability to regulate the OBG. As m increased, the OBG will be broadened. The θ has a similar ability in adjusting the photonic band gap (PBG), a larger θ will get a wider PBG. When θ = 85°, the TM wave achieves the PBG in the range of 0–3 (2πc/d). So the ultra-wide PBG can be got by the large θ. Contrary to m, d_p has an inverse relationship with the bandwidth of the OBG. As d_p increases, the bandwidth of the OBG will be decreased. Fortunately, the frequency range of the OBG can be controlled by d_p. But ω_p cannot regulate the bandwidth of the OBG. Increasing m and reducing d_p appropriately can obtain a lower frequency and wider OBG. This feature is very beneficial to designing devices such as waveguides, filters, and antenna substrates. In addition, an interesting phenomenon can be found when m = 2, an extra high reflection zone can be inspired in the TM wave. It provides a theoretical support for designing the narrowband filters without introducing any physical defect layers in the structure.