Chalcogenide nanofeatures on calcium fluoride bring metalens technology to the mid-IR

Metamaterial optics, usually in the form of a nanostructured metasurface, have the potential to be transformative for precision optics. Existing metasurface optics have been fabricated that operate in the visible and near-IR regions; the mid-IR, due to its different set of optical materials, has been left out.

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Now, scientists at the Massachusetts Institute of Technology (MIT; Cambridge, MA), the University of Electronic Science and Technology of China, and the East China Normal University have rectified this situation by creating diffraction-limited mid-IR metasurface optics using chalcogenide-alloy nanofeatures lithographically fabricated on calcium fluoride (CaF₂) substrates.¹ Such optics could help to simplify and lighten the weight of mid-IR sensing instruments for the detection of biomolecular and chemical signals.

The wideband properties of chalcogenide and CaF₂ enable optical designs to be created anywhere within a wide portion of the mid-IR. The transmissive optical efficiencies of the diffraction-limited fabricated devices ranged up to 75% for linearly polarized light.

"This kind of metasurface can be made using standard microfabrication techniques," says Tian Gu, one of the researchers. "The manufacturing is scalable."

The research was funded by the Defense Advanced Research Projects Agency (DARPA), under the Extreme Optics and Imaging Program, and the National Natural Science Foundation of China.

Source: http://news.mit.edu/2018/improving-mid-infrared-imaging-and-sensing-0426

REFERENCE:

1. Li Zhang et al., Nature Communications (2108); doi: 10.1038/s41467-018-03831-7.