Numerical Simulation of Non-Reciprocal Acoustic Waveguide Based on Indirect Interband Transitions

We recently proposed a non-reciprocal acoustic device based on an indirect interband transition by applying space-time density modulation in a two-dimensional acoustic waveguide formed by a water core sandwiched by metal claddings [1]. By performing a series of the Finite Difference Time Domain (FDTD)simulations, we demonstrated the nonreciprocity of wave propagation and obtained optimum parameter sets of the modulation length and the wavevector shift. To further optimize the present model toward practical applications, we extend the model to the waveguide with the core filled with a solid medium and search for its optimum matching conditions for the mode transition. Since our approach is based on a linear dynamic system, high efficiency can be achieved with wide-band tunability. Practical device implementation for wideband tunable operation can be proposed via the tolerance analyses for the phase matching condition.