3D-Printed Gradient-Index Phononic Crystal Lens for Underwater Acoustic Wave Focusing
Ahmed Allam, Karim G. Sabra, Alper Ertürk
Abstract
A 3D-printed gradient-index phononic crystal structure based on air inclusions in a polymer is introduced to manipulate underwater acoustic waves. The proposed approach enables a simple configuration without heavy inclusions or geometrically complex unit cells to create the required refractive-index profile and focus incident plane waves propagating in a known direction. Based on the band-structure analysis, a gradient-index lens is designed, fabricated, and tested, yielding an excellent agreement between the experimental results and finite-element simulations of underwater acoustic wave focusing. The proposed concept and the resulting lens design can find applications spanning from power enhancement in acoustic energy transfer and harvesting to signal enhancement in sensing and imaging.