Angular-Asymmetric Transmitting Metasurface and Splitter for Acoustic Waves: Combining the Coherent Perfect Absorber and a Laser

For simplicity and efficiency, metasurfaces need to be constructed of passive and lossless material. On the contrary, a coherent perfect absorber (CPA), and its time-reversal device the laser, require lossy active materials. Thus ideas from CPA design have seldom been extended to metasurfaces. This study shows that the combination of CPA and laser can also work as an efficient wavefront-manipulating device, if the wave energy absorbed by the CPA can be somehow recovered and then re-emitted by the L]laser. Not only could this approach greatly simplify metasurface design, but it could also bridge research efforts on metasurfaces and non-Hermitian systems.