High-Efficiency Achromatic Metalens Topologically Optimized in the Visible.

Area of Science:

• Optics and Photonics
• Nanotechnology
• Computational Design

Background:

• Metalenses are ultrathin optical elements using nano-post arrays for wavefront modulation.
• Existing achromatic metalenses for circular polarization suffer from low focal efficiency due to inefficient nano-posts.
• Low polarization conversion efficiency limits the practical application of metalenses.

Purpose of the Study:

• To improve the focal efficiency of achromatic metalenses.
• To explore topology optimization for designing nano-posts with enhanced properties.
• To overcome limitations in existing achromatic metalens designs.

Main Methods:

• Utilizing topology optimization to simultaneously design phase dispersion and polarization conversion efficiency of nano-posts.
• Simulating the performance of a 40 μm diameter achromatic metalens.
• Comparing simulated focal efficiency with previous metalens designs.

Main Results:

• Topology optimization enabled simultaneous optimization of phase dispersion and polarization conversion efficiency.
• The designed achromatic metalens achieved an average focal efficiency of 53% across a spectrum of 531 nm to 780 nm.
• This efficiency is significantly higher than previously reported achromatic metalenses (20-36%).

Conclusions:

• Topology optimization is an effective method for improving broadband achromatic metalens focal efficiency.
• The developed design strategy addresses key limitations in nano-post based metalenses.
• This advancement paves the way for more practical and high-performance compact optical systems.