Electrically Driven Varifocal Silicon Metalens

TL;DR

This paper introduces an electrically controlled varifocal silicon metalens that can dynamically adjust focus in the visible spectrum, enabling compact, reconfigurable optical systems with fast response times.

Contribution

It presents a novel electrically tunable metalens using a thermo-optical polymer and embedded resistor, achieving continuous focal length adjustment with low voltage and fast response.

Findings

Focal length can be tuned continuously with less than 12V.

Focal length variation exceeds the Rayleigh length.

System response time is approximately 100 ms.

Abstract

Optical metasurfaces have shown to be a powerful approach to planar optical elements, enabling an unprecedented control over light phase and amplitude. At that stage, where wide variety of static functionalities have been accomplished, most efforts are being directed towards achieving reconfigurable optical elements. Here, we present our approach to an electrically controlled varifocal metalens operating in the visible frequency range. It relies on dynamically controlling the refractive index environment of a silicon metalens by means of an electric resistor embedded into a thermo-optical polymer. We demonstrate precise and continuous tuneability of the focal length and achieve focal length variation larger than the Rayleigh length for voltage as small as 12 volts. The system time-response is of the order of 100 ms, with the potential to be reduced with further integration. Finally, the imaging capability of our varifocal metalens is successfully validated in an optical microscopy setting. Compared to conventional bulky reconfigurable lenses, the presented technology is a lightweight and compact solution, offering new opportunities for miniaturized smart imaging devices.