3D-printed multilayer structures for high-numerical aperture achromatic metalenses

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Traditional flat optics (metalenses) using high-refractive index materials often suffer from narrow bandwidth and limited numerical aperture (NA).
• Existing achromatic metalenses face a trade-off between NA and operational bandwidth, hindering practical applications.
• Achieving broadband, high-NA, and polarization-insensitive metalenses remains a significant challenge in optical engineering.

Purpose of the Study:

• To propose and demonstrate a novel approach for designing high-NA, broadband, and polarization-insensitive multilayer achromatic metalenses (MAMs).
• To overcome the inherent limitations of existing metalens designs, particularly the NA-bandwidth trade-off.
• To utilize inverse design strategies combined with advanced fabrication techniques for creating next-generation meta-devices.

Main Methods:

• Employed topology optimization coupled with full-wave electromagnetic simulations for inverse design of MAMs.
• Fabricated the designed MAMs using two-photon polymerization lithography in low-refractive index materials.
• Characterized the optical performance of the fabricated metalenses, including NA, bandwidth, and efficiency.

Main Results:

• Successfully designed and fabricated 20 μm diameter MAMs operating across the visible spectrum (400-800 nm).
• Achieved high numerical apertures of 0.5 and 0.7 with efficiencies up to 42%.
• Demonstrated broadband imaging capabilities using both white light and RGB narrowband illumination.

Conclusions:

• The proposed inverse design approach enables the creation of high-performance, broadband, and polarization-insensitive achromatic metalenses.
• 3D-printed multilayer structures offer a promising platform for realizing multifunctional meta-devices.
• This work paves the way for advanced flat optics with applications in imaging and optical systems.