Acoustic Power Divider Based on Compressibility-Near-Zero Propagation

Abstract

Materials with properties that can be described by a near-zero index of refraction have received significant attention in the fields of electromagnetics, optics, and acoustics, due to their extraordinary capabilities in wave manipulation. It was recently demonstrated theoretically and experimentally that acoustic waves could manifest near-zero-index propagation based on the effective compressibility of a waveguide channel approaching zero. In turn, this allows tunneling of acoustic waves with nearly infinite wavelength (or equivalently, uniform phase) when the channel cross section is much larger than the feeding lines. Here, we show that these concepts can be leveraged to realize an acoustic power divider and multiplexer offering tunneling of sound to an arbitrary number of output ports, with phase shifts equal to 0\ifmmode^\circ\else\textdegree\fi{} or 180\ifmmode^\circ\else\textdegree\fi{} and robust response to variations in the port position. We present analytical and numerical models describing the properties of this device and study limitations and trade-offs that occur in the presence of losses as the device size is scaled.