Metasurfaces for independent manipulation of the wavefronts in the different states of phase change materials

Metasurfaces have attracted increasing attention due to their extraordinary capability in the arbitrary control of electromagnetic waves. However, most metasurfaces lack flexibility and only enable fixed optical performance once fabricated. In this work, we propose ultra-thin metasurfaces with varied functionalities using phase change materials (PCMs) when phase change occurs on whole structured PCMs, which has not been found in previous reports. The wavefronts in the amorphous and crystalline states of the PCMs can be arbitrarily and independently modulated with high efficiency (similar to 60% and similar to 40% in the two states, respectively). This work may be valuable for information encryption and optical communications. (C) 2018 The Japan Society of Applied Physics