Mechanically tunable focusing metamirror in the visible

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Advanced reconfigurable optical systems require compact, flat lenses with tunable focal lengths.
• Metasurfaces, or two-dimensional nanostructures, offer a method to control light wavefronts.
• Actuated metasurfaces can enable dynamic focal length adjustment.

Purpose of the Study:

• To design and realize the first reflection-type tunable metalens (metamirror) operating in the visible regime.
• To demonstrate dynamic focal length tunability in a flat optics element.
• To explore the potential applications of tunable metalenses.

Main Methods:

• Design of a metasurface with a hyperboloidal phase profile.
• Fabrication of the metalens on an actuated substrate.
• Characterization of focal length tunability and focusing performance at 670 nm.

Main Results:

• The tunable metalens achieved continuous focal length adjustment up to 45%.
• Adjustment was achieved through 0% to 20% lateral stretching of the substrate.
• Diffraction-limited focusing and high focusing efficiency were maintained during tuning.

Conclusions:

• The developed tunable metalens is a significant advancement in flat optics.
• This technology has potential applications in wearable mixed reality, biomedical instruments, and integrated optics.
• The metamirror design offers a compact and efficient solution for reconfigurable optical systems.