Helicity-dependent orbital angular momentum metalens for varifocal and polarization-multiplexing applications

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Optical vortex beams are crucial for advanced optical communication.
• Current metasurfaces lack dynamic and multi-dimensional control for polarization multiplexing and focusing.
• Limitations hinder synergistic applications in optical communication technologies.

Purpose of the Study:

• To design a dual-layer helicity-dependent tunable orbital angular momentum dielectric metalens.
• To achieve dynamic and multi-dimensional control over optical vortex beams.
• To overcome limitations of existing metasurfaces in polarization multiplexing and dynamic focusing.

Main Methods:

• Designed a dual-layer metalens with silicon nanopillars and Sb₂S₃ phase-change material nanopillars.
• Utilized propagation and geometric phases for control.
• Achieved tunable focal length via material phase transition without structural alteration.

Main Results:

• Demonstrated simultaneous generation of ±1 topological charge spots from linearly polarized light.
• Achieved tunable focusing for circularly polarized light with topological charges of -1 (16.4–20.0 µm) and +1 (32.5–43.0 µm).
• Attained focusing efficiencies over 56.7% for circularly polarized light and 39% for linearly polarized light.

Conclusions:

• The developed metalens integrates polarization multiplexing and continuous focusing capabilities.
• It shows potential for applications in integrated optical vortex devices and quantum information processing.
• This work is expected to promote the development of low-cost, large-scale optical vortex chips.