Modal contrast engineering in ultraviolet and visible metalenses enabled by material-selective hybridization

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Metasurfaces offer ultrathin optics but face challenges in extending high efficiency from UV to visible light due to material and design constraints.
• Existing metasurface designs often require geometric modifications for different spectral windows, limiting versatility.

Purpose of the Study:

• To present a novel material-selective hybrid metalens platform enabling high-efficiency operation across distinct spectral windows without geometric changes.
• To overcome limitations in extending metasurface efficiency to the visible spectrum.

Main Methods:

• Fabrication of a hybrid metalens with a stable SiO2 skeleton conformally coated with nanometer-thick oxide layers.
• Utilizing low-temperature atomic layer annealing (80°C) to crystallize TiO2 for visible light and preserve amorphous ZrO2 for UV transparency.
• Achieving modal birefringence through ultrathin coatings for polarization conversion.

Main Results:

• High-efficiency metalenses demonstrated in distinct spectral windows: 69% average efficiency in UV (250-400 nm) and 75% in visible (400-700 nm).
• Diffraction-limited focusing achieved across the entire UV-visible bandwidth.
• Demonstrated applications include a compact UV camera for dermatology and forensics, and a lightweight full-color virtual-reality eyepiece.

Conclusions:

• Hybrid metasurfaces with tunable oxide coatings provide a scalable and manufacturing-compatible solution for ultrathin optics.
• This platform overcomes previous limitations, offering a viable alternative to bulky refractive optics for diverse applications.