Work

Reversal Asymmetry of Reciprocal Metasurface Enables Ultra‐Compact Varifocal Reflective Lens

Year: 2025

Type: article

Abstract: A conventional refractive lens surface can act as a positive (converging) or negative (diverging) lens, but the same surface cannot act as both. For circular polarized light, a geometric phase metasurface lens can behave as both a positive or negative lens upon transmission through its front or rear side, respectively, owing to the chirality of the metasurface. This offers certain freedom in compound lens design, where one combines focusing and defocusing operations. We utilize this property to make an ultra-compact, varifocal reflective lens, where a metasurface is placed in front of a novel long-stroke piezoelectric MEMS-micromirror. A proof-of-concept implementation using a 1550nm NIR metalens is demonstrated, attaining a diopter change on the order of 1052m−1 for a focal length shift of 240μm caused by a 53μm thin-film piezoelectric micromirror displacement. It is therefore well suited for wafer-level silicon fabrication at high volumes and low cost.

Source: Laser & Photonics Review

DOI: 10.1002/lpor.202501196