Multifunctional metalens generation using bilayer all-dielectric metasurfaces

Area of Science:

• Photonics and optical engineering
• Metamaterials and nanophotonics

Background:

• Optical metasurfaces offer precise control over light's phase, amplitude, and polarization.
• Phase-change materials provide dynamic tunability for optical devices.

Purpose of the Study:

• To propose and demonstrate a multifunctional metalens with dual working modes.
• To achieve dynamic reconfigurability and high focusing efficiency using bilayer geometric phase elements.

Main Methods:

• Utilized bilayer geometric phase elements composed of antimony selenide (Sb2Se3) and amorphous silicon (a-Si).
• Exploited the tunable crystalline states of Sb2Se3 to control optical properties in transmission and reflection modes.
• Operated the metalens at the telecommunication C-band.

Main Results:

• Achieved a bifocal metalens in transmission mode with an arbitrary intensity ratio and up to 78% focusing efficiency.
• Demonstrated reflection mode operation with Sb2Se3 acting as a half-wave plate, achieving up to 30% focusing efficiency.
• Showcased dynamic reconfigurability through state changes in the phase-change material.

Conclusions:

• The proposed multifunctional metalens exhibits high focusing efficiency and dual working modes.
• Potential applications include polarization state detection, optical imaging, and optical data storage.
• The bilayer design is scalable to multilayer structures for enhanced light manipulation capabilities.