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

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

doi:10.1002/adom.202000745

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

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

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

31 Citations (Scopus)

Abstract

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 language	English
Article number	2000745
Journal	Advanced Optical Materials
Volume	8
Issue number	20
DOIs	https://doi.org/10.1002/adom.202000745
Publication status	Published - 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

Keywords

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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10.1002/adom.202000745

Cite this

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title = "An Over-Coupled Phase-Change Metasurface for Efficient Reflection Phase Modulation",

abstract = "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.",

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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: {\textcopyright} 2020 Wiley-VCH GmbH",

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AU - Brongersma, Mark L.

N1 - 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

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N2 - 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.

AB - 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.

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

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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