Frequency selective wave beaming in nonreciprocal acoustic phased arrays
Abstract

Acoustic phased arrays are capable of steering and focusing a beam of sound via selective coordination of the spatial distribution of phase angles between multiple sound emitters. Constrained by the principle of reciprocity, conventional phased arrays exhibit identical transmission and reception patterns which limit the scope of their operation. This work presents a controllable space–time acoustic phased array which breaks time-reversal symmetry, and enables phononic transition in both momentum and energy spaces. By leveraging a dynamic phase modulation, the proposed linear phased array is no longer bound by the acoustic reciprocity, and supports asymmetric transmission and reception patterns that can be tuned independently at multiple channels. A foundational framework is developed to characterize and interpret the emergent nonreciprocal phenomena and is later validated against benchmark numerical experiments. The new phased array selectively alters the directional and frequency content of the incident signal and imparts a frequency conversion between different wave fields, which is further analyzed as a function of the imposed modulation. The space–time acoustic phased array enables unprecedented control over sound waves in a variety of applications ranging from ultrasonic imaging to non-destructive testing and underwater SONAR telecommunication.

Authors:
; ; ; ;
Award ID(s):
Publication Date:
NSF-PAR ID:
10360740
Journal Name:
Scientific Reports
Volume:
10
Issue:
1
ISSN:
2045-2322
Publisher:
Nature Publishing Group
5. Active imaging and structured illumination originated in “bulk” optical systems: free-space beams controlled with lenses, spatial light modulators, gratings, and mirrors to structure the optical diffraction and direct the beams onto the target. Recently, optical phased arrays have been developed with the goal of replacing traditional bulk active imaging systems with integrated optical systems. In this paper, we demonstrate the first array of optical phased arrays forming a composite aperture. This composite aperture is used to implement a Fourier-based structured-illumination imaging system, where moving fringe patterns are projected on a target and a single integrating detector is used to reconstruct the spatial structure of the target from the time variation of the back-scattered light. We experimentally demonstrate proof-of-concept Fourier-basis imaging in 1D using a six-element array of optical phased arrays, which interfere pairwise to sample up to 11 different spatial Fourier components, and reconstruct a 1D delta-function target. This concept addresses a key complexity constraint in scaling up integrated photonic apertures by requiring only$N$elements in a sparse array to produce an image with$N2$resolvable spots.