Abstract
As a key component of various acoustic systems, acoustic beam splitter (BS) finds important application in many scenarios, yet are conventionally based on the assumption that the acoustic waves propagate as easily when incident from either input or output side. It would therefore be intriguing, from the viewpoints of both science and technology, to break through this limit by realizing acoustic BSs supporting asymmetric transmission. Here we propose the concept of one-way acoustic BS capable of splitting acoustic beam incident from the input port into multiple beams while effectively reducing the backward transmission from any of the output ports. Furthermore, our design enables flexibly adjusting the number and angle of output beams by blocking the unused line defects. The numerical results verify the theoretical predictions and demonstrate the phenomenon of one-way acoustic BS at the predesigned frequency. Our design with functionality and flexibility bridges the gap between acoustic diodes and BSs and may enable novel multi-functional devices with great application prospects in diverse fields such as acoustic integrated circuits and acoustic communication.
Highlights
As a key component of various acoustic systems, acoustic beam splitter (BS) finds important application in many scenarios, yet are conventionally based on the assumption that the acoustic waves propagate as when incident from either input or output side
The existing designs of acoustic BSs are proposed based on the basic assumption that the transmission of acoustic wave is symmetric along the two opposite directions, suggesting that the incident acoustic energy is allowed to pass through the whole system and be split into multiple beams regardless of the port the wave enters
The schematic of our proposed one-way acoustic BS is illustrated in Fig. 1(a), which is formed by introducing defects with broken symmetry into a phononic crystals (PnCs) which consists of the asymmetric cavity defect and the line defect
Summary
As a key component of various acoustic systems, acoustic beam splitter (BS) finds important application in many scenarios, yet are conventionally based on the assumption that the acoustic waves propagate as when incident from either input or output side It would be intriguing, from the viewpoints of both science and technology, to break through this limit by realizing acoustic BSs supporting asymmetric transmission. In this Letter, we propose the concept of one-way acoustic BS capable of breaking through the above fundamental limit This is enabled by a different mechanism that uses the combination of a line defects acting as waveguides in a PnC and a cavity defect with specially-designed asymmetric geometry to break the space-reversal symmetry and thereby support asymmetric cavity mode that couples to the waveguide modes with coupling strength quite different along opposite directions. Pressure distribution for the transmitted wave in the combined system in the positive incidence and negative incidence cases
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