Systematic Design and Experimental Demonstration of Transmission‐Type Multiplexed Acoustic Metaholograms

• Published in: Advanced functional materials 2021-07, Vol.31 (27), p.n/a
• Main Authors: Zhu, Yifan, Gerard, Nikhil JRK, Xia, Xiaoxing, Stevenson, Grant C., Cao, Liyun, Fan, Shiwang, Spadaccini, Christopher M., Jing, Yun, Assouar, Badreddine
• Format: Article
• Language: English
• Subjects: acoustic hologram; acoustic holograms; acoustic metamaterials; acoustic metasurfaces; Acoustics; amplitude and phase modulations; Holograms; MATERIALS SCIENCE; Metamaterials; Multiplexing; transmitted waves; Ultrasonic imaging; Unit cell
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202101947

Acoustic holograms have promising applications in sound‐field reconstruction, particle manipulation, ultrasonic haptics, and therapy. This study reports on the theoretical, numerical, and experimental investigation of multiplexed acoustic holograms at both audio and ultrasonic frequencies via a rationally designed transmission‐type acoustic metamaterial. The proposed metahologram is composed of two Fabry–Pérot resonant channels per unit cell, which enables the simultaneous modulation of the transmitted amplitude and phase at two desired frequencies. In contrast to conventional acoustic metamaterial‐based holograms, the design strategy proposed here provides a new degree of freedom (frequency) that can actively tailor holograms that are otherwise completely passive and significantly enhances the information encoded in acoustic metamaterials. To demonstrate the multiplexed acoustic metamaterial, the projection of two different high‐quality metaholograms is first shown at 14 and 17 kHz, with the patterns of the letters N and S. Then, two‐channel ultrasound focusing and annular beams generation for the incident ultrasonic frequencies of 35 and 42.5 kHz are demonstrated. These multiplexed acoustic metaholograms offer a technical advance to tackle the rising challenges in the fields of acoustic metamaterials, architectural acoustics, and medical ultrasound. Frequency‐multiplexed acoustic holograms by transmission‐type acoustic metamaterials are demonstrated. The multiplexing is based on multiple Fabry–Pérot resonant channels with simultaneous amplitude and phase modulation. The pattern of the letters N and S is experimentally observed at 14 and 17 kHz. Two‐channel ultrasound focusing and annular beams generation are experimentally demonstrated at 35 and 42.5 kHz.