MEMS-tunable dielectric metasurface lens

Ehsan Arbabi,Mohammadsadegh Faraji-Dana,Andrei Faraon,Seyedeh Mahsa Kamali,Amir Arbabi,Yu Horie

doi:10.1038/s41467-018-03155-6

Ehsan Arbabi, Mohammadsadegh Faraji-Dana + Show 4 more

Open Access

https://doi.org/10.1038/s41467-018-03155-6

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Abstract

Varifocal lenses, conventionally implemented by changing the axial distance between multiple optical elements, have a wide range of applications in imaging and optical beam scanning. The use of conventional bulky refractive elements makes these varifocal lenses large, slow, and limits their tunability. Metasurfaces, a new category of lithographically defined diffractive devices, enable thin and lightweight optical elements with precisely engineered phase profiles. Here we demonstrate tunable metasurface doublets, based on microelectromechanical systems (MEMS), with more than 60 diopters (about 4%) change in the optical power upon a 1-μm movement of one metasurface, and a scanning frequency that can potentially reach a few kHz. They can also be integrated with a third metasurface to make compact microscopes (~1 mm thick) with a large corrected field of view (~500 μm or 40 degrees) and fast axial scanning for 3D imaging. This paves the way towards MEMS-integrated metasurfaces as a platform for tunable and reconfigurable optics.

Highlights

Varifocal lenses, conventionally implemented by changing the axial distance between multiple optical elements, have a wide range of applications in imaging and optical beam scanning
The system consists of a stationary metasurface on a glass substrate, and a moving metasurface on a SiNx membrane
The membrane can be electrostatically actuated to change the distance between the two metasurfaces

Summary

Introduction

Conventionally implemented by changing the axial distance between multiple optical elements, have a wide range of applications in imaging and optical beam scanning. We have developed a fabrication process for making such metasurface doublets, and experimentally show metasurface lenses with over 60 μm tuning of the effective focal length (EFL) from 565 to 629 μm, corresponding to a ~180-diopter change in the optical power Arrays of these devices can be fabricated on the same chip to allow for multiple lenses with different focal distances scanning different depths with frequencies potentially reaching several kHz. In addition, we show that such devices can be combined with the recently demonstrated monolithic metasurface optical systems design[50] to develop compact focus-scanning objectives with corrected monochromatic aberrations over a large field of view. The concepts and techniques used in such devices can be combined with the metasurface doublet demonstrated here to achieve enhanced functionalities (e.g., enable lateral scanning of focus)

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