Broadband holography and switchable multifunction by a tunable highly efficient terahertz metasurface based on...

Area of Science:

• Optics and Photonics
• Metamaterials
• Terahertz Technology

Background:

• Traditional terahertz (THz) metasurfaces, often based on the Pancharatnam-Berry (PB) principle, face limitations in tunability, operating bandwidth, and angular/polarization dependence.
• These constraints hinder the practical application of THz metasurfaces in advanced communication and biomedical fields.

Purpose of the Study:

• To propose and demonstrate a dynamically tunable terahertz metasurface utilizing the phase-change properties of vanadium dioxide (${{\rm VO}_2}$).
• To achieve multifunctional electromagnetic wave modulation, including high-efficiency wavefront shaping and perfect absorption, over a wide frequency range.
• To design and verify a switchable focusing metalens based on this tunable metasurface.

Main Methods:

• Fabrication of a terahertz metasurface incorporating vanadium dioxide (${{\rm VO}_2}$) as a phase-change material.
• Thermal switching of the ${{\rm VO}_2}$ material to modulate the electromagnetic response of the metasurface.
• Characterization of the metasurface's performance in reflection mode (wavefront shaping) and absorption mode across various terahertz frequencies.

Main Results:

• The metasurface demonstrated a cross-polarization reflection coefficient exceeding 0.8 across an ultra-wideband of 0.55-1.41 THz with full ${2}\pi$ phase coverage in reflection mode.
• Holographic imaging capabilities were achieved within the 1.0-1.5 THz frequency range.
• In absorption mode, the structure exhibited over 80% absorption efficiency across the ultra-wide frequency band of 0.95-1.95 THz.
• The designed metalens showed efficient switchable focusing.
• The meta-atoms maintained polarization insensitivity and robustness across different polarizations and incidence angles in both modes.

Conclusions:

• The proposed dynamically tunable terahertz metasurface based on ${{\rm VO}_2}$ offers significant advancements over traditional non-tunable devices.
• The metasurface's ability to switch between high-efficiency wavefront shaping and perfect absorption, along with its wide bandwidth and polarization insensitivity, promotes practical applications.
• This research lays a foundation for developing multifunctional tunable THz devices for communication and biomedical applications.