Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Analysis and Design of a Reconfigurable Metasurface based on Chalcogenide Phase-Change Material for Operation in the Near and Mid Infrared

Alexandros Pitilakis, Alexandros Katsios, Alexandros-Apostolos A. Boulogeorgos

TL;DR

This work designs a GST225-based reflective metasurface unit cell for near- to mid-infrared optical wireless applications, leveraging a square patch on a GST-containing dielectric multilayer to tune resonance via phase-change. A combined transmission-line and equivalent-circuit model predicts reflection spectra; GST dispersion is captured by a DTLM for the extreme amorphous/crystalline states and interpolated via Lorentz-Lorenz for intermediate phases, with a Kramers-Kronig reconstruction of the real part. The design achieves $>180^\circ$ phase tunability with $|R|$ better than $-6$ dB at $\lambda_0 = 1550$ nm and is validated against full-wave simulations, indicating potential for continuously reconfigurable holographic metasurfaces in the IR, while highlighting oblique-incidence limitations and thermal considerations. The findings pave the way for thermally reconfigurable, wavefront-shaping metasurfaces in optical wireless links, with future work on electro-thermal actuation, speed, and multiphysics modeling.

Abstract

We analyze, design and assess the performance of a reflective reconfigurable metasurface (MS) architecture for optical wireless communications. The device is based on the Ge-Sb-Te (GST225) phase-change material (PCM) alloy, thermally toggled between highly distinct amorphous and crystalline phase-states. We employ simple conductive MS patterns to tune its resonance frequency, while allowing the unit cell response to be analytically predicted using transmission line theory and equivalent circuits. The GST material dispersion is computed in its two extreme phase-states using a Drude/Tauc-Lorentz model (DTLM), whose parameters are fitted to state-of-the-art experimental data; the dispersion in intermediate partially crystallized phase-states is computed using the Lorentz-Lorenz formula. Our results, corroborated by full-wave simulations, demonstrate the potential of PCM materials for the implementation of continuously reconfigurable holographic metasurfaces operating in the infrared bands.

Analysis and Design of a Reconfigurable Metasurface based on Chalcogenide Phase-Change Material for Operation in the Near and Mid Infrared

TL;DR

This work designs a GST225-based reflective metasurface unit cell for near- to mid-infrared optical wireless applications, leveraging a square patch on a GST-containing dielectric multilayer to tune resonance via phase-change. A combined transmission-line and equivalent-circuit model predicts reflection spectra; GST dispersion is captured by a DTLM for the extreme amorphous/crystalline states and interpolated via Lorentz-Lorenz for intermediate phases, with a Kramers-Kronig reconstruction of the real part. The design achieves phase tunability with better than dB at nm and is validated against full-wave simulations, indicating potential for continuously reconfigurable holographic metasurfaces in the IR, while highlighting oblique-incidence limitations and thermal considerations. The findings pave the way for thermally reconfigurable, wavefront-shaping metasurfaces in optical wireless links, with future work on electro-thermal actuation, speed, and multiphysics modeling.

Abstract

We analyze, design and assess the performance of a reflective reconfigurable metasurface (MS) architecture for optical wireless communications. The device is based on the Ge-Sb-Te (GST225) phase-change material (PCM) alloy, thermally toggled between highly distinct amorphous and crystalline phase-states. We employ simple conductive MS patterns to tune its resonance frequency, while allowing the unit cell response to be analytically predicted using transmission line theory and equivalent circuits. The GST material dispersion is computed in its two extreme phase-states using a Drude/Tauc-Lorentz model (DTLM), whose parameters are fitted to state-of-the-art experimental data; the dispersion in intermediate partially crystallized phase-states is computed using the Lorentz-Lorenz formula. Our results, corroborated by full-wave simulations, demonstrate the potential of PCM materials for the implementation of continuously reconfigurable holographic metasurfaces operating in the infrared bands.

Paper Structure

This paper contains 6 sections, 2 figures.

Table of Contents

  1. Introduction
  2. Methodology
  3. Evaluating Reflection Spectra using Transmission Line and Equivalent Circuit Models
  4. Computing the Phase-Change Material Frequency Dispersion
  5. Results
  6. Conclusion and Outlook

Figures (2)

  • Figure 1: (a) Unit cell architecture. DTLM/LLF-computed refractive index spectra, (b) real and (c) imaginary part.
  • Figure 2: TLM/ECM-computed reflection spectra, including GST material dispersion, under (a) normal, (b) oblique TE $45^\circ$, and (c) oblique TM $45^\circ$ incidence, for a range of crystallization ratios. The shaded region marks a 200 nm span centered around the operating wavelength $\lambda_0=1550$ nm (193.4 THz).