The metals are enhanced with liquid crystals

For more than 500 years, humans have mastered the art of refracting light by forming glass into lenses, then bending or combining those lenses to enhance images and make them clearer as close-up as far-off.

But in the last decade or so, a group led by scientist Federico Capasso at Harvard University began to transform the field of optics by using flat metsurfaces of optical optics, using an array of millions of small microscopically thin and transparent quartz players to use the diffraction and shape to give luminous flux in much the same way as a glass lens, but without the aberrations that naturally limit the glass.

The technology was selected in 2019 as among the Top 10 Emerging Technologies by the World Economic Forum (WEF), noting that these increasingly smaller, clear lenses are soon beginning to appear in camera phones, sensors, optical glass lines and medical devices. – imaging devices, such as endoscopes.

“Making the lenses used by mobile phones, computers and other electronic devices smaller has been beyond the capabilities of traditional glass cutting and glass bending techniques,” according to the WEF. “… These sharp, thin, flat lenses could replace existing bulky glass lenses and allow further miniaturization in sensors and medical imaging devices.”

Make metalenses ‘reconfigurable’

Now, vacancy professor Giuseppe Strangi from Case Western Reserve University and Harvard collaborators have taken a step toward making these “metal cuttings” even more useful – by reconfiguring them.

They did this by using nanoscale forces to infiltrate liquid crystals between those microscopic pillars, allowing them to shape and diffract light in completely new ways – ‘the mood of the focusing force,’ Strangi said.

Liquid crystals are particularly useful because they can be thermally, electrically, magnetically or optically manipulated, potentially creating flexible or reconfigured lenses.

“We believe this holds the promise of revolutionizing optics, as we have known it since the 16th century,” said Strangi, whose Nanoplasm Lab at Case Western Reserve investigates “extreme optics” and the “interaction of light and matter at the nanoscale,” “among other things.

Until recently, once a glass lens was formed into a rigid curve, it could only bend light in one way, except when combined with other lenses or physically displaced, Strangi said.

Metalenses changed that because they allow the wavefront to be controlled by controlling phase, amplitude and polarization of light.

Now, by controlling the liquid crystal, the researchers have been able to move this new class of metallenses to new scientific and technological endeavors to generate reconfigurable structured light.

“This is just the first step, but there are many possibilities for using these lenses, and we have already made contact with companies interested in this technology,” said Strangi.

The paper announcing the breakthrough was published in early August by the Proceedings of the National Academy of Sciences.

Strangi collaborated with several other researchers in the United States and Europe, including fellow researchers from Case Western Reserve Andrew Lininger and Jonathan Boyd; Giovanna Palermo of Universita ‘della Calabria in Italy; and Capasso, Alexander Zhu and Joon-Suh Park of the John A. Paulson School of Engineering and Applied Sciences at Harvard University.

Lininger said part of the problem with current metasurfaces applications is that their shape is fixed at the point of production, but “by enabling reconfiguration in the metasurface, these limitations can be overcome.”

Capasso, who pioneered in the field of optical research and in 2014 for the first time published research on metals, credited Strangi for the idea of ​​infiltrating the metals with liquid crystals and said that this innovation takes a step towards even greater things.

“Our ability to infiltrate reproducibly with liquid crystals state-of-the-art metalenses made from more than 150 million glass nanoscale pillars and significantly change their focusing properties is a portent of the fascinating science and technology I expect to come from reconfigurable flat optics in the future, ”Capasso said.