Acoustic leaky-wave antennas from zero-index metamaterials

We present an acoustic leaky-wave antenna based on zero-refractive-index metamaterials, offering significantly enhanced radiation efficiency and directivity compared to conventional designs. The zero-refractive-index metamaterial incorporates periodically distributed space-coiling structures, leveraging Dirac-like dispersion and accidental degeneracy to achieve vanishing effective density and compressibility simultaneously. The proposed acoustic Dirac leaky-wave antenna (ADLWA) achieves more than double the radiation efficiency of conventional antennas utilizing arrays with shunt ducts and membranes. It also exhibits superior directional control, enabling precise beam scanning through frequency tuning. Additionally, the ADLWA functions as a passive sonar system capable of detecting the direction of arrival of moving sound sources. This work expands the possibilities for acoustic wave control, with potential applications in acoustic sensing and communication technology.