Angular Memory of Photonic Metasurfaces

Nonlinear materials can exhibit bistability, namely support different possible outputs for the same input, depending on the excitation history. This property can find direct application to photonic memory devices, the vast majority of which operate by changing the amplitude of the incoming signals. In this work, we study impedance metasurfaces producing hysteresis responses with respect to impinging beam angle by keeping a fixed intensity profile; accordingly, the considered setups remember the history of illumination incidence. The reported findings may open new unexplored avenues toward the design of photonic systems supporting a wide range of fixed-power memory functionalities from switching and sensing to information storage and data writing.