Bilayer machine can management many types of polarized gentle

Virtually a decade in the past, Harvard engineers unveiled the world’s first visible-spectrum metasurfaces—ultra-thin, flat gadgets patterned with nanoscale buildings that might exactly management the conduct of sunshine. A robust various to conventional, cumbersome optical parts, metasurfaces right now allow compact, light-weight, multifunctional functions starting from imaging techniques and augmented actuality to spectroscopy and communications.

Now, researchers within the Harvard John A. Paulson Faculty of Engineering and Utilized Sciences (SEAS) are doubling down, actually, on metasurface expertise by making a bilayer metasurface, fabricated from not one, however two stacked layers of titanium dioxide nanostructures. Underneath a microscope, the brand new machine appears to be like like a dense array of stepped skyscrapers.

The analysis is revealed in Nature Communications.

“This can be a feat of nanotechnology on the highest stage,” mentioned senior writer Federico Capasso, the Robert L. Wallace Professor of Utilized Physics and Vinton Hayes Senior Analysis Fellow in Electrical Engineering at SEAS. “It opens up a brand new method to construction gentle, by which we will engineer all its elements resembling wavelength, part and polarization in an unprecedented method… It signifies a brand new avenue for metasurfaces that—thus far—have simply been scratching the floor.”

For hundreds of years, optical techniques have relied on cumbersome, curved lenses fabricated from glass or plastic to bend and focus gentle. The SEAS-led metasurface revolution of the final decade has produced flat, ultra-thin buildings patterned with hundreds of thousands of tiny parts that may manipulate gentle with nanometer precision. A putting instance of this expertise is the metalens. In contrast to standard lenses, metalenses may be fabricated with current semiconductor manufacturing, making attainable compact, built-in optical techniques in gadgets like smartphones, cameras, and augmented actuality shows.

After Capasso’s group reported their first working metalens that may bend seen gentle, they labored with Harvard’s Workplace of Expertise Growth to license the expertise and begin an organization, Metalenz. They’ve since demonstrated a bunch of potential functions, together with an endoscope, an synthetic eye, and a telescope lens.

However the single-layer nanostructure design Capasso’s group invented has been—in some methods—limiting. For instance, earlier metasurfaces put particular necessities on the manipulation of sunshine’s polarization—that’s, the orientation of the sunshine waves—with the intention to management the sunshine’s conduct.

“Many individuals had investigated the theoretical chance of a bilayer metasurface, however the true bottleneck was the fabrication,” mentioned Alfonso Palmieri, graduate scholar and co-lead writer of the examine. With this breakthrough, Palmieri defined, one may think about new sorts of multifunctional optical gadgets—for instance, a system that initiatives one picture from one aspect and a totally completely different picture from the opposite.

Utilizing the amenities of the Heart for Nanoscale Programs at Harvard, the group that included former postdoctoral researchers Ahmed Dorrah and Joon-Suh Park got here up with a fabrication course of for freestanding, sturdy buildings of two metasurfaces that maintain strongly collectively however don’t have an effect on one another chemically. Whereas such multi-level patterning has been widespread within the silicon semiconductor world, it had not been as properly explored in optics and metaoptics.

To display the facility of their machine, the group devised an experiment by which they used their bilayer metalens to behave on polarized gentle in the identical manner {that a} sophisticated system of waveplates and mirrors does.

In future experiments, the group may develop into much more layers to exert management over different elements of sunshine, resembling excessive broadband operation with excessive effectivity throughout the complete seen and near-infrared spectrum, opening the door to much more refined light-based functionalities.