Constructing an achromatic polarization-dependent bifocal metalens with height-gradient metastructures

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Metalenses offer compact wavefront tailoring using metastructures.
• Chromatic aberration and multifunctionality are key challenges in metalens design.

Purpose of the Study:

• To develop an achromatic bifocal metalens (ABM) overcoming limitations of conventional metalenses.
• To achieve dual-focus functionality and eliminate chromatic aberration using a novel design.

Main Methods:

• Fabrication of a metalens using three-dimensional standing nano blocks (SNBs).
• Introduction of a height gradient to SNBs to control optical properties.
• Utilizing orthogonal linear polarization switching for distinct focal lengths.

Main Results:

• Demonstration of achromatic focusing across the 760-1550 nm wavelength range.
• Achieved two distinct focal lengths by switching incident beam polarization.
• The ABM exhibited high performance in eliminating chromatic aberration.

Conclusions:

• The developed ABM offers a promising solution for achromatic and multi-functional metalenses.
• Potential applications include polarization sensing, advanced displays, and shared-aperture optics.
• This work advances the development of compact, high-performance optical elements.