High-efficiency rectangular transverse air-gap metalens for visible light based on a dual-coupled PB phase

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Pancharatnam-Berry (PB) phase modulation is crucial for controlling focal spherical waves.
• Material absorption in waveguide structures causes energy loss, limiting focusing efficiency in visible light.
• General nanopillar models struggle with broad bandwidths and efficiency.

Purpose of the Study:

• To introduce a novel dual-coupled metalens design for efficient phase modulation.
• To overcome energy loss limitations in visible light spectral range.
• To provide new design inspiration for micro-optical devices and phase modulations.

Main Methods:

• Designed a dual-coupled metalens using air slot-etched rectangular TiO2 nanopillars.
• Utilized the air gap as a high-aspect-ratio rectangular waveguide for light confinement.
• Tested optical performance across the visible spectrum (440–670 nm) at various numerical apertures (0.35–0.82).

Main Results:

• The dual-coupled metalens structure meets PB phase control requirements.
• Demonstrated ultra-low optical loss within the visible spectrum.
• Achieved ultra-high focusing efficiency across tested numerical apertures.
• The design shows potential for wide-spectral metalens applications.

Conclusions:

• The proposed dual-coupled metalens design effectively minimizes energy loss.
• This novel structure offers significant improvements in focusing efficiency for visible light.
• The design provides a new pathway for developing advanced micro-optical devices and phase modulations.