GRIN metamaterial generalized Luneburg lens for ultra-long acoustic jet

In this work, a 3D-printed mesoscale acoustic generalized Luneburg lens based on cylindrical metamaterial is proposed. Compared to isotropic lenses, we numerically and experimentally demonstrate a series of advantages of lens including the super long work distance (over 17λ, 20 kHz in air), without obvious sidelobe, and better acoustic impedance matching. The ray tracing method is revealed to interpret the ultra-long acoustic jets mechanism. The adjustment of the lattice unit composition allows for the manipulation of air and underwater acoustic waves. The present work inspires a straightforward strategy for ultra-long acoustic jets, with promising applications in imaging and treatment in biological tissues.