The realization of phase discontinuities across metasurfaces has led to a new class of reflection and refraction. Here we present theory and experiment on the discontinuous propagation of wavepackets across subwavelength-thickness meta-atoms. Using acoustic waves, we observe the process of wavepackets traversing a meta-atom with abrupt displacements, which appear as path discontinuities on a space-time diagram. We construct a tunable meta-atom from two coupled resonators at ∼500 Hz, map the spatiotemporal trajectories of individual sonic pulses, and reveal discontinuities at the meta-atom where the pulses exit at a time ∼50ms ahead or behind their arrivals. Applications include thin acoustic metasurface lenses.
Bibliographical noteFunding Information:
This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology (NRF-2013K2A2A4003469 and NRF-2013R1A5A1A95042044). We also acknowledge Grants-in-aid for Scientific Research from the Japan Society for the Promotion of Education, Science, Sports and Culture.