Dual-Band Metasurfaces Using Multiple Gap-Surface Plasmon Resonances.

Area of Science:

• Plasmonics and Nanophotonics
• Flat Optics and Metasurface Technology
• Optical Engineering and Design

Background:

• Metasurfaces offer versatile optical functionalities but achieving multi-spectral operation and diverse functions simultaneously remains challenging.
• Existing metasurface designs often lack flexibility for integrating multiple functionalities across different spectral ranges.
• Gap-surface plasmon (GSP) resonances provide a promising avenue for novel metasurface designs.

Purpose of the Study:

• To propose and demonstrate dual-band multifunctional metasurfaces utilizing multiple GSP resonances.
• To design GSP meta-atoms capable of resonating at two distinct wavelengths for simultaneous operation.
• To achieve polarization-independent beam steering and polarization-splitting at both visible and telecom wavelengths.

Main Methods:

• Designing GSP meta-atoms with tailored nanobrick dimensions to support first-order (1450 nm) and third-order (633 nm) resonances.
• Fabricating phase-gradient GSP metasurfaces based on the designed meta-atoms.
• Characterizing the optical performance, including diffraction efficiency and functionality, at the targeted wavelengths.

Main Results:

• Successfully designed and fabricated GSP metasurfaces exhibiting dual-band operation.
• Achieved simultaneous polarization-independent beam steering and polarization-splitting at telecom (1350-1550 nm) and visible (575-675 nm) wavelengths.
• Demonstrated high diffraction efficiencies: >65% at 1450 nm (1350-1550 nm range) and >20% at 633 nm (575-675 nm range).

Conclusions:

• The study presents a flexible and robust approach for creating efficient dual-band GSP metasurfaces.
• The demonstrated metasurfaces integrate multiple functionalities, paving the way for advanced flat optics.
• This method is readily adaptable for complex integrated designs, enabling diverse applications in optical systems.