Isotropic Ge3Sb2Te6 metasurfaces for mid-infrared wavefront steering

Abstract

Abstract Due to unprecedented electromagnetic properties, germanium antimony telluride (GST) plays a crucial role in the field of electromagnetic wavefront control. With the purpose of mid-infrared wavefront reconfiguration, eight meta-atoms are proposed. Meta-atoms appear in different phase states as state is switched. As crystalline is involved, eight meta-atoms reach full phase coverage with phase gradient of 45°. As is switched to amorphous state, phase difference between adjacent meta-atoms no longer varies uniformly by 45°, thus losing original properties. Based on eight meta-atoms, four metasurfaces are presented to verify characteristics, which are two metalenses and two orbital angular momentum (OAM) generators. As crystalline is switched to amorphous , dynamical manipulation between focusing and defocusing is realized. Besides, OAM mode of vortex beam is reconstructed from or 2 to . Our designs could find potential applications in focusing, switching, and encryption.