Acoustic Multiband Double Negativity from Coupled Single-Negative Resonators

Superresolved imaging is strongly desired for acoustic nondestructive testing, but normally is available only in a single frequency band. This study presents an elegant design for a multiband double-negative ($i.e.$ both bulk modulus and effective mass density are negative) unit cell, using the coupling of single-negative resonators, where double negativity in multiple bands is due to overlap of dipolar and monopolar modes within the unit cell. The number of double-negative bands depends on the number of optimally coupled resonator pairs in the unit cell, and thus is easily manipulated. This approach is appealing for subwavelength imaging devices that span many frequencies.