What They Say
Up to now, most metalens architectures have been based on building raised pillars to create nanosurfaces that can influence light to create metalenses. Now Optics.org reports that a group at Harvard SEAS has published a paper (Nano Letters) on a new approach that uses holes in the surface rather than pillars. These are less susceptible to damage than pillars.
The Harvard team designed metalenses with ultradeep via-holes in 5-micron thick free-standing silicon membranes, with the aspect ratio of the holes approaching 30:1. It is the first time that holes with such an aspect ratio have been used in metaoptics, according to the project team, and the metalenses were fabricated using conventional CMOS-compatible semiconductor processes and standard materials.
Trials showed that a flat 2-millimeter-diameter metalens patterned with holes in a series of 2000 thin rings each 0.5-microns wide could successfully focus incident infrared light into a diffraction-limited spot, thanks to the changes in optical path length of light through the holey meta-atoms.
Future work could see the holes filled in with nonlinear optical materials, for multi-wavelength generation and manipulation of light, or with liquid crystals to achieve active modulation of light’s properties, according to the group.
What We Think
Although there is ‘no Moores Law for optics’, the work in metalenses and nanotechnology that is supporting semiconductor production is opening up new routes to develop optical components. (BR)
