An Over-Coupled Phase-Change Metasurface for Efficient Reflection Phase Modulation

Junghyun Park, Soo Jin Kim, Patrick Landreman, Mark L. Brongersma

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


An over-coupled, thermally tunable metasurface reflect-array that employs the phase change material Ge2Sb2Te5 (GST) is presented. The metasurface is constructed from gap plasmon cavities in which GST is incorporated as the active switching medium. Upon annealing at 200 °C for 10 min, the GST layer undergoes a transition from the amorphous state to the crystalline state, and this leads to a unity-order increase of the refractive index. This is accompanied by a spectral shift of 1.6 µm in the resonance wavelength of the plasmonic cavities, larger than their resonance linewidth of 1.2 µm. It is shown that the low material absorption of the GST layer enables operation of the metasurface in the desirable over-coupled regime. The numerical analysis indicates that this facilitates large changes in the reflection phase (up to 270°) and amplitude. The work opens the possibility of creating efficient reconfigurable metasurfaces for various applications, including holographic displays and image sensors.

Original languageEnglish
Article number2000745
JournalAdvanced Optical Materials
Issue number20
Publication statusPublished - 2020 Oct 1

Bibliographical note

Funding Information:
J.P. and S.J.K. contributed equally to this work. The authors deeply appreciate close reading and insightful discussion from Dr. Sun‐Je Kim. The research was funded by Samsung Advanced Institute of Technology (SAIT) and an individual investigator grant from the AFOSR (FA9550‐17‐1‐0331).

Publisher Copyright:
© 2020 Wiley-VCH GmbH


  • beam steering
  • metasurfaces
  • phase change materials
  • wavefront shaping

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics


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