MEMS-actuated metasurface Alvarez lens

Zheyi Han; Shane Colburn; Arka Majumdar; Karl F Böhringer

doi:10.1038/s41378-020-00190-6

MEMS-actuated metasurface Alvarez lens

Microsyst Nanoeng. 2020 Oct 5:6:79. doi: 10.1038/s41378-020-00190-6. eCollection 2020.

Authors

Zheyi Han^{1

2}, Shane Colburn¹, Arka Majumdar^{1

3}, Karl F Böhringer^{1

2

4}

Affiliations

¹ Department of Electrical and Computer Engineering, University of Washington, Seattle, Washington 98195 USA.
² Institute for Nano-Engineered Systems, University of Washington, Seattle, Washington 98195 USA.
³ Department of Physics, University of Washington, Seattle, Washington 98195 USA.
⁴ Department of Bioengineering, University of Washington, Seattle, Washington 98195 USA.

Abstract

Miniature lenses with a tunable focus are essential components for many modern applications involving compact optical systems. While several tunable lenses have been reported with various tuning mechanisms, they often face challenges with respect to power consumption, tuning speed, fabrication cost, or production scalability. In this work, we have adapted the mechanism of an Alvarez lens - a varifocal composite lens in which lateral shifts of two optical elements with cubic phase surfaces give rise to a change in the optical power - to construct a miniature, microelectromechanical system (MEMS)-actuated metasurface Alvarez lens. Implementation based on an electrostatic MEMS generates fast and controllable actuation with low power consumption. The utilization of metasurfaces - ultrathin and subwavelength-patterned diffractive optics - as optical elements greatly reduces the device volume compared to systems using conventional freeform lenses. The entire MEMS Alvarez metalens is fully compatible with modern semiconductor fabrication technologies, granting it the potential to be mass-produced at a low unit cost. In the reported prototype operating at 1550 nm wavelength, a total uniaxial displacement of 6.3 µm was achieved in the Alvarez metalens with a direct-current (DC) voltage application up to 20 V, which modulated the focal position within a total tuning range of 68 µm, producing more than an order of magnitude change in the focal length and a 1460-diopter change in the optical power. The MEMS Alvarez metalens has a robust design that can potentially generate a much larger tuning range without substantially increasing the device volume or energy consumption, making it desirable for a wide range of imaging and display applications.

Keywords: Electrical and electronic engineering; Electronic devices; Nanophotonics and plasmonics.