An invisible acoustic sensor based on parity-time symmetry

By R. Fleury, Dimitrios L. Sounas, Andrea Alù. Nature Communications, 2015

712 citations recorded by the source corpus.

Sensing an incoming signal is typically associated with absorbing a portion of its energy, inherently perturbing the measurement and creating reflections and shadows. Here, in contrast, we demonstrate a non-invasive, shadow-free, invisible sensor for airborne sound waves at audible frequencies, which fully absorbs the impinging signal, without at the same time perturbing its own measurement or creating a shadow. This unique sensing device is based on the unusual scattering properties of a parity-time (PT) symmetric metamaterial device formed by a pair of electro-acoustic resonators loaded with suitably tailored non-Foster electrical circuits, constituting the acoustic equivalent of a coherent perfect absorber coupled to a coherent laser. Beyond the specific application to non-invasive sensing, our work broadly demonstrates the unique relevance of PT-symmetric metamaterials for acoustics, loss compensation and extraordinary wave manipulation. Any typical sensing device must absorb energy, thereby altering the measured signal as it propagates on. By exploiting parity-time symmetry via non-Foster circuits, Fleury et al. show that a sensor can be built that absorbs incoming signals without perturbing them or creating a shadow, rendering it invisible.

Subfields: Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials

View Paper: https://www.semanticscholar.org/paper/7dec700cd90ea8c83d8af02799fcae52c40a46c7

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In Atomic and Molecular Physics, and Optics

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Citations in the corpus

Roadmap on metasurfaces (2019, background): “features have been proposed to realize flat lenses that can focus images without aberration, as shown in figure 14(d) [127], as well as efficient sensors that do not leave shadows [128].”
Non-Hermitian systems and topology: A transfer-matrix perspective (2018, background): “Similar realizations of non-Hermitian models are also possible in other experimental setups, such as mechanical [23], acoustic [24, 25], electronic [26], and ultracold atomic [27] systems.”
Generalized parity–time symmetry condition for enhanced sensor telemetry (2018, methodology): “Inspired by optical schemes, other PT -symmetric systems in electronics (sub-radiofrequency, 30 KHz and below [25]-[27] ) , acoustics [28] and optomechanics [29],[30] have also been recently reported.”
Edge States and Topological Invariants of Non-Hermitian Systems. (2018, neutral): “[29] Romain Fleury, Dimitrios Sounas, and Andrea Alù, “An invisible acoustic sensor based on parity-time symmetry,” Nature communications 6, 5905 (2015).”
Symmetry and Topology in Non-Hermitian Physics (2018, background): “[81] R.”
Active times for acoustic metamaterials (2019, background): “to exceptional scattering behavior such as anisotropic transmission resonances (ATR), also called unidirectional cloaking [186], and systems that behave simultaneously as coherent perfect absorbers and lasers [202,203].”
Unidirectional reflectionless light propagation at exceptional points (2017, background): “Based on unidirectional invisibility in acoustics, a noninvasive, shadow-free, fully invisible acoustic sensor with PT symmetry was recently demonstrated [140].”
Invisibility and Cloaking: Origins, Present, and Future Perspectives (2015, methodology): “Such furtive sensors have been implemented experimentally for acoustic waves [197] using properly designed electroacoustic transducers, confirming the theory established in Ref.”
Exceptional topology of non-Hermitian systems (2019, neutral): “, 2019b), and invisible acoustic sensors with PT symmetry (Fleury et al., 2015).”