A one-way street for acoustic waves

If you can hear your neighbors through a shared wall, you better believe they can hear you too. This has nothing to do with your annunciation and everything to do with a fundamental property of how waves — be they acoustic, light or electric — move through materials. Most media are reciprocal, meaning if a wave can travel from point A to point B, it can also travel from point B to point A at identical frequencies and amplitudes.

Now, Lan Yang, Edwin H. & Florence G. Skinner Professor in the Preston M. Green Department of Electrical & Systems Engineering at the McKelvey School of Engineering at Washington University in St. Louis and researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a non-reciprocal device for acoustic waves that could be used in next-generation wireless communication and quantum computing. This may be advantageous for eavesdroppers, but reciprocity causes all kinds of interference and crosstalk in signal processing. As communications technology gets smaller — and waves get confined in smaller and smaller spaces — devices that can break a signal’s symmetry are increasingly more important. However, most of today’s so-called non-reciprocal acoustic devices are too bulky and difficult to integrate onto chips.

The research was published earlier this summer in Nature Electronics.

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