Double-layer metalens with a reduced meta-atom aspect ratio.

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Dielectric metalenses typically require high meta-atom aspect ratios, complicating fabrication.
• Achieving full 0-2π phase modulation often exacerbates this issue.

Purpose of the Study:

• To develop a novel metalens design that reduces the meta-atom aspect ratio.
• To enable easier fabrication of metalenses while maintaining high performance.

Main Methods:

• Designed a double-layer metalens composed of circular nanopillars.
• Constructed nanopillars using polycrystalline silicon and titanium dioxide (TiO2) layers.
• Fabricated and experimentally validated the metalens performance.

Main Results:

• Demonstrated a significantly lower required aspect ratio compared to single-material metalenses.
• Achieved a focusing spot close to the diffraction limit.
• Experimental focusing efficiency exceeded 22%.

Conclusions:

• The double-layer metalens design effectively lowers aspect ratios, simplifying fabrication.
• The metalens exhibits achromatic properties and polarization independence.
• This approach offers a promising path for advanced metalens development.