beijing optics

Researchers combine metalens with an artificial muscle

Drawing inspiration from the intricate workings of the human eye, our team at the Harvard John A. Paulson School of Engineering and Applied Sciences has pioneered an innovative adaptive metalens. This cutting-edge creation is essentially a flat, electronically controlled artificial eye that adeptly manages to correct three primary causes of blurred images: focus, astigmatism, and image shift. Published in the esteemed journal Science Advances, our research marks a significant milestone in optical technology. We’ve ingeniously combined the latest advancements in artificial muscle technology with the precision of metalens technology. The result? A tunable metalens that mirrors the dynamic focus capabilities of the human eye, but with an added twist – it can dynamically correct for aberrations like astigmatism and image shift, which are beyond the natural abilities of the human eye. Our breakthrough holds immense promise for a myriad of applications, from enhancing the capabilities of cell phone cameras to revolutionizing eyeglasses, and even transforming the realms of virtual and augmented reality hardware. It paves the way for future optical microscopes that could operate entirely electronically, capable of correcting multiple aberrations simultaneously.

Photo of the metalens (made of silicon) mounted on a transparent, stretchy polymer film, without any electrodes. The colorful iridescence is produced by the large number of nanostructures within the metalens. (Image courtesy of the Capasso Lab/Harvard SEAS)
Photo of the metalens (made of silicon) mounted on a transparent, stretchy polymer film, without any electrodes. The colorful iridescence is produced by the large number of nanostructures within the metalens. (Image courtesy of the Capasso Lab/Harvard SEAS)

Our vision extends to harmonizing the semiconductor manufacturing and lens-making industries, leveraging the same processes used in computer chip production to craft metasurface-based optical components. To emulate the human eye’s ciliary muscle, which adjusts the lens’s shape to alter its focal length, we collaborated with David Clarke, a renowned figure in the field of dielectric elastomer actuators, also known as artificial muscles. We selected a thin, transparent dielectric elastomer with minimal light scattering to couple with the lens, surmounting the challenge of marrying its properties with those of semiconductors to create a novel, multifunctional device.

By applying voltage to the elastomer, we can precisely control its stretch, thereby adjusting the position of nanopillars on the lens’s surface. This allows the metalens to be finely tuned, not only to focus but also to manage astigmatism-induced aberrations and perform image shifts. Remarkably, the combined thickness of the lens and muscle is a mere 30 microns.

Our adaptive metalens stands as a testament to the potential of correcting the inherent astigmatism and other aberrations present in all optical systems with multiple components, from everyday cameras to sophisticated microscopes and telescopes. By offering a flat adaptive optical element, we can correct these aberrations and consolidate various optical capabilities onto a single plane of control.

As we look to the future, our goal is to enhance the lens’s functionality further and reduce the voltage needed for its operation. This research, a collaborative effort with Shuyan Zhang and Samuel Shian, has been supported by the Air Force Office of Scientific Research and the National Science Foundation, with some work conducted at the Center for Nanoscale Systems, also backed by the NSF.

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