Design and demonstration of underwater acoustic carpet cloaks

The carpet cloak, which is designed to hide the objects placed on a reflecting surface, has become a topic of considerable interest. Inspired by those theoretical works, the experimental realization of acoustic carpet cloak in air host has been reported. However, due to the difficulty in obtaining the unit cell in reality, the underwater carpet cloak still remains in simulation thus far. Here, we design and fabricate realizable 2D and 3D underwater acoustic carpet cloaks. By introducing scaling factors, a modest impedance mismatch is brought in to simplify the structure of these carpet cloaks. We investigate their effectiveness through experiments in the anechoic water tank. The experimental results demonstrate that these carpet cloaks can hide the information of the bump on the reflecting plane in a wide frequency range. This may bring great potential engineering applications in the practical underwater devices.