LAUSR

Non-reciprocity has recently attracted considerable attention as it enables new possibilities in wave manipulation and control. Here, we propose and analyze theoretically and numerically a waveguide system consisting of two membranes whose surface tensions are time-modulated with a phase difference between them. Strong non-reciprocity and low insertion loss can result for waves transmitted through the structure. An analytic approach is developed to calculate the harmonics generation in the system. Based on this approach, the optimal design of a two-membrane system for non-reciprocal wave behavior is then discussed. By suitably choosing the modulation parameters, the isolation factor for waves incident from opposite sides can reach as high as 19.8 dB and an insertion loss of only 2.8 dB, with an overall dimension being less than 1/3 wavelength. These theoretical results are verified by time-dependent finite element simulations. Our work provides a feasible way to design acoustic non-reciprocal devices.