INESC MN and Harvard report in Nano Letters that advanced silica meta-optics can match high-index platforms using new nanofabrication methods

A collaboration between INESC MN and the Harvard John A. Paulson School of Engineering and Applied Sciences has shown that ordinary glass can rival, and in some cases outperform, high-index semiconductors for flat optics. The work, published in Nano Letters as “Silica Meta-Optics: When High Performance Does Not Need a High Index”, demonstrates that carefully engineered silica (SiO₂) metasurfaces can achieve high efficiency, broad bandwidth and strong fabrication tolerance, offering a scalable, CMOS-compatible platform for advanced meta-optic components.

The Lisbon team at INESC MN, led by Técnico Prof. Marco Piccardo, contributed the high-aspect-ratio etching technology that enables ultratall silica nanopillars with vertical sidewalls—key to unlocking these advantages in practice and highlighted the promise for structured light. “The advantages of silica meta-optics we highlight in this work were partly overlooked until now because of major obstacles in nanofabrication,” said Marco Piccardo. “As we are able now to etch very tall nanopillars with vertical sidewalls, we can make full use of this low-index platform, with all its benefits for exciting applications.”

Link to publication: https://pubs.acs.org/doi/10.1021/acs.nanolett.5c04960