Active Metasurfaces via Locally Phase-Changed Materials
Yu Han Chen1*, Cheng Hung Chu2, Ming Lun Tseng1, Hsiang-Chu Wang1, Ting-Yu Chen1, Jie Chen1, Wei-Yi Tsai1, Din Ping Tsai2
1Department of Physics, National Taiwan University, Taipei, Taiwan
2Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
* presenting author:Yu Han Chen,
Many researchers have dedicated efforts to phase-change materials to excavate their diverse chemical and physical characteristics over the past few decades. Because of thermal stability and rapid transition of phase-change material Ge2Sb2Te5 (GST) between amorphous and crystalline states, it has been utilized as the recording medium in optical and electronic rewritable data storage.

Metamaterials and metasurfaces, the artificial sub-wavelength structures exhibit the abilities to actively control the optical responses and therefore play potential candidates for a number of feasible applications such as perfect absorber , planar lenses , plasmonic antenna , Fano resonance and so on. Recently, the development have been focused on integration of phase-change material into such artifical photonic structures. However, in most of researches, the use of phase-change material is limited as a switchable dielectric environment (a switch between crystalline and amorphous states).

In this paper, we present the tunable optical resonance of phase-change material Ge2Sb2Te5 in the near-infrared regime.It provides us a clear insight into the dipole resonance of this dielectric system. Further, we propose the concept of reconfigurable metasurfaces, which have different combination of unit cells with various geometries and phase states.We also present the novel reconfigurable metasurfaces for tuning the optical resonance and light steering. These proposed phase-change metasurfaces show the great potential in polarization control, optical communication and optical data storage.

Keywords: metasurface, phase change material, gradient metasurface