Figure 4.

GST-based various photonic meta-devices. (a) Schematic demonstration of the metadevice structure; (b) Fresnel-zone-plate pattern, which was written in the GST layer of binary and grayscale metadevice; (c) The cross-sectional strength of optical hotspots that were concentrated by Fresnel-zone-plate; (d–f) Tunable and active zone-plate metadevice; two overlapped Fresnel zone patterns are (d) written, (e) erased, and (f) rewritten; (g–i) Overlapped Fresnel zone patterns figured during three steps of writing, erasing, and restoring corresponding to (d–f); (j,k) R/T spectra of the written dielectric material into the GST layer for (j) horizontally and (k) vertically polarized light; (l) Multilayer split-ring resonator of GST-based meta-switch; (m) The RI and k of GST under both amorphous and crystalline phases measured by an ellipsometer; (n) SEM image of the fabricated metadevice; (o) Reflection, transmission, and absorption curves of the meta-switch with vertically polarizing light to the splits of the ring resonator, before using a buffer layer, GST film, and the protective layer; (p) Optical transmission, reflection, and their modulation contrast related to GST phase shift in both phases of GST layer of the hybrid metadevice. (a–k) are adapted from [29],with permission from © 2017 Nature Publishing Group; and (l–p) are adapted from [3], with permission from © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.