Broadband passive nonlinear acoustic diode

In dynamical and acoustical systems, breaking reciprocity is achievable by employing external biases, spatial temporal variations of material properties, or nonlinearities. In this present work, we propose, theoretically analyze, and experimentally demonstrate the first passive broad-band mechanical diode, by adding an asymmetric local nonlinear interface to an otherwise linear waveguide. It is shown that for a broad range of input energies and frequencies, three different types of nonreciprocal behavior are obtained, (i) different transmitted energies depending on the direction of wave propagation, (ii) transmission of acoustic waves allowed in one direction but not in the reverse direction, and (iii) arrest of propagating waves at the nonlinear interface only in one (preferred) direction. A unique feature of the proposed acoustic device compared with previous designs is its capability to achieve passive nonreciprocity without altering or distorting the frequency content of the sending signal. The proposed system can pave the way for designing passive acoustic or thermal diodes, and adaptable nonreciprocal wave transmission devices of enhanced robustness that are tunable with, and passively adaptive to energy.