Double with Metasurface: Double layer devices can control many forms of polarization

Almost a decade ago, Harvard engineers introduced Lulatai’s thin flat device, the world’s first visible spectral metasurface, patterned with nanoscale structures that allow precise control of light behavior. Today, a powerful alternative to traditional bulky optical components, Metasurfaces enables compact, lightweight, multifunctional applications ranging from imaging systems and augmented reality to spectroscopy and communications.

Currently, researchers at Harvard’s John A. Paulson School of Engineering and Applied Sciences (Sea) are doubling metasurface technology by literally creating double layer metawas that are not made up of two stacked titanium dioxide nanostructures. Under the microscope, the new device appears to be a dense array of stepped skyscrapers.

This study is published in Nature Communications.

“This is a feat of nanotechnology at the highest level,” said Federico Capaso, professor of applied physics in marine electrical engineering and senior researcher Vinton Hayes. “It opens up a new way of building light, where you can design all aspects of wavelength, phase, polarization, and more in an unprecedented way.

For centuries, optical systems rely on bulky curved lenses made of glass or plastic, bent and focused on light. The marine-led metasurface revolution of the past decade has produced flat, ultra-thin structures patterned with millions of small elements capable of manipulating light with nanometer accuracy. An impressive example of this technology is Metalens. Unlike traditional lenses, methane can be manufactured in existing semiconductor manufacturing, enabling compact, integrated optical systems in devices such as smartphones, cameras and augmented reality displays.

After reporting on Metalens, the first work that could bending visible light, the Capasso team worked with the Harvard University Technology Development Office to license the technology and launched the company Metalenz. They have since demonstrated many potential applications, including endoscopes, artificial eye, and telescope lenses.

However, the team invented by the team at Single Layer Nanostructure Design Capasso has been monitored in several ways. For example, previous metasurfaces have listed specific requirements to control the behavior of light in manipulation of light polarization, i.e., the directionality of light waves.

“Many people were investigating the theoretical possibilities of double layer metasurfaces, but the real bottleneck was manufacturing,” says Alfonso Palmieri, a graduate student and co-star in the study. With this breakthrough, Palmieri explained that he could imagine a new kind of multifunctional optical device, for example, a system that projects an image on one image and a completely different image from the other.

Using the facility at Harvard University’s Nanoscale Systems Center, the team, including former doctoral researchers Ahmeddora and Junshpark, came up with a manufacturing process for the self-supporting, robust construction of two metasurfaces. Such multilevel patterns were common in the silicon semiconductor world, but were not explored much in optics and metaoptics.

To demonstrate the power of the device, the team devised an experiment that uses double layer metalene to act on polarization, similar to complex systems of waveforms and mirrors.

In future experiments, the team will expand to more layers to control other aspects of light, such as extreme broadband operations with high efficiency across the visible and near-infrared spectrum, opening the door to even more refined light-based features.