Directional Acoustic Antennas Based on Valley‐Hall Topological Insulators

Abstract

Realizing directional acoustic signal transmittance and reception robust against surrounding noise and competing signals is crucial in many areas such as communication, navigation, and detection for medical and industrial purposes. The fundamentally wide-angled radiation pattern of most current acoustic sensors and transducers displays a major limitation of the performance when it comes to precise targeting and probing of sound particular of interest in human speaking and hearing. Here, it is shown how topological acoustic valley transport can be designed to enable a unique beamforming mechanism that renders a superdirective needle-like sound radiation and reception pattern. The strategy rests on out-coupling valley-polarized edge states, whose beam is experimentally detected in the far-field with 10° width and a sound-intensity enhancement factor ≈10. Furthermore, anti-interference communication is proposed where sound is received from desired directions, but background noise from other directions is successfully suppressed. This type of topological acoustic antenna offers new ways to control sound with improved performance and functionalities that are highly desirable for versatile applications.

Acoustic resonance coupling for directional wave control: from angle-dependent absorption to asymmetric transmission

“…Moreover, our approach enabling the angle-sensitive absorption can be useful for applications, e.g. acoustic antennas capable of absorbing the sound wave in a specific angle while isolating unwanted acoustic waves (noise) from other angles [38].…”

Topological Phononics: From Fundamental Models to Real Materials

“…The topological states exhibit widely ranged applications including dissipationless phonon waveguides and phonon diode, phononic antennas, acoustic delay lines, and negative refraction materials . The one‐way edge states of QAH‐like states are ideal channels to realize dissipationless phonon wave guides due to the absence of backscattering channels.…”

“…There exist phononic topological boundary states as a result of bulk‐boundary correspondence . The phononic topological boundary states are immune to scattering from defects on boundaries, which enables lots of useful applications including phonon waveguides, robust acoustic antennas, acoustic delay lines, etc.…”

Deep‐Subwavelength Holey Acoustic Second‐Order Topological Insulators

“…For example, most of the reported results focus solely on a single frequency band, whose limitations ought to be overcome in order to provide a broadband response for topologically robust acoustics. Concerning this matter, the findings will thus have the capability to push forward exciting applications for robust acoustic imaging way beyond the diffraction limit.The discovery of topological insulators (TIs) [1,2] and the strikingly robust transmission of reflectionless edge states have boosted intense research in classical systems such as photonics, [3][4][5][6][7][8][9] acoustics, [10][11][12][13][14][15][16][17][18][19][20][21][22] and mechanics. Lastly, in terms of compactness, it is desired to utilize building blocks of the HOTI on a subwavelength scale in order to confine sound in tight areas beyond the diffraction limit.…”

“…The discovery of topological insulators (TIs) [1,2] and the strikingly robust transmission of reflectionless edge states have boosted intense research in classical systems such as photonics, [3][4][5][6][7][8][9] acoustics, [10][11][12][13][14][15][16][17][18][19][20][21][22] and mechanics. [23][24][25][26] Most recently, the concept of higher-order TIs (HOTIs), [27][28][29][30][31][32][33] which is a special class of TIs with unconventional bulk-boundary correspondence, was proposed to support the existence of the lower-dimensional boundary states.…”