On the design of unit-cells for acoustic metasurfaces

Acoustic metasurfaces have gained popularity for their capability to tailor the phase front of transmitted and reflected waves. While most of researches conducted in this topic are spinning around different applications and peculiar physics of these surfaces, the study of constituent elements for metasurfaces is still missing. Here, we introduce a new labyrinthine type unit-cell for phase engineering of the transmitted wave front. Despite the complexity of the shape, the structure is very easy to design. Moreover, it is based on well defined mathematical formula which facilitates the design and optimization procedure. While the proposed unit-cell has the physical length of less than lambda/3, it can cover the full 2pi phase range thanks to space coiling.