Acoustic amplifying diode using non-reciprocal Willis coupling

TL;DR

This paper introduces an acoustic amplifying diode that combines signal isolation and amplification using non-reciprocal Willis coupling in active metamaterials, enabling unidirectional sound amplification without reflection.

Contribution

It presents the first experimental demonstration of an acoustic amplifying diode utilizing non-reciprocal Willis coupling in active metamaterials, combining amplification and isolation in one device.

Findings

Successful experimental demonstration of the amplifying diode.

Achieved exponential amplification in one direction without reflection.

Discussed implementation with reciprocal and non-reciprocal Willis couplings.

Abstract

We propose a concept called acoustic amplifying diode in combining both signal isolation and amplification in a single device. The signal is exponentially amplified in one direction with no reflection and is completely absorbed in another. In this case, the reflection is eliminated from the device in both directions due to impedance matching, preventing backscattering to the signal source. Here, we experimentally demonstrate the amplifying diode using an active metamaterial with non-reciprocal Willis coupling. We also discuss the situation with the presence of both reciprocal and non-reciprocal Willis couplings for more flexibility in implementation. The concept of acoustic amplifying diode will enable applications in sound isolation, sensing and communication, in which non-reciprocity can play an important role.