Multi-channel filters with high performance based on the creation of a geometrical defect in 1D phononic star waveguides structure

Abstract

In this paper, we investigate the existence of one or two defect modes in the phononic band structure and the transmission coefficient in a one-dimensional phononic star waveguides (SWGs) structure. This structure exhibits large band gaps and pass bands, which due to the periodicity of the system and the resonance states of the grafted lateral branches (resonators). The defect modes result from the presence of a defective segment in the star waveguides structure and may occur in these gaps. We show there is dual frequency acoustic filtering based on two defect modes in a wide gap by creating a defect at the segment level in a one-dimensional star waveguides structure when pumped by an acoustic wave under a normal incidence. The defect modes are sensitive to the defect length d01, the number N of cells, and the position J of the defect. The color map of the transmission rate (TR) is discussed as a function of the defect segment length d01 and the resonator length d2. The transmission spectrum and the band structure are theoretically presented using the Green functions approach based on the formalism of the interface response theory for acoustic waves propagating in star waveguides structure. This structure has potential applications as an acoustic guide, multi-channel filters and demultiplexers.