https://www.nature.com/articles/s41565-017-0034-6

“Meta” is an overused prefix that is often used as a standalone word. It is hard to know what it means in many contexts. In metalens, it is used to mean a lens (for focusing light) that isn’t really a lens in the generally understood sense.

Here, they are figuring out how to make surfaces that are flat (not curved) macroscopically, but with nanofins that are tuned to affect light rays the same through all the visible wavelengths. The point is to make a thinner, lighter, less complicated lens for optics. They are aiming at cheaper, too, but I bet it is overly expensive in the current state of research. Cheaper in the long run seems likely to me.

The article, which is $5 to have for a few hours for reading, or $20 to keep (I did neither), indicates the lens works from full red through blue. (Purples, apparently, will not be properly focused.) It also indicates its efficiency is 20% so far. Not adequate. I bet they figure it out though. It almost sounds too good to be true, but the engineering looks like the hard part, and that is just a matter of time, just a matter of trial and error. It might make cell-phone cameras as good as the best SLRs.

The supplemental information file is available free here: https://static-content.springer.com/esm/art%3A10.1038%2Fs41565-017-0034-6/MediaObjects/41565_2017_34_MOESM1_ESM.pdf

The supplemental file is useful, and I figure everyone with some understanding of optical wave mechanics should get an intuitive feel for what is going on just from the first figure, a simple schematic showing how the surface is saw-toothed (nanoscale) to accommodate the fact that prisms spread white light into the rainbow colors as the light passes through. (The prism tips interact with the waves, too, keeping the light together, not spreading into a rainbow.)

The supplemental videos aren’t useful, and only the last two (essentially the same) are cool to watch. (The videos show the thing works. Good to know, but worthless for intuition and understanding.)

BTW, “An optical system with the ability to produce images with angular resolution as good as the instrument’s theoretical limit is said to be diffraction limited.” That is, the discussed metalens is theoretically as good as possible in focusing potential.

After thought: Journals, especially Nature, are much too proud of their status. This research was paid for by public money (USAF & NSF tax-funded research). The journals argue that the fees for articles (or subscriptions) pay for their services, primarily peer review and editing. Well, maybe a bit, but it is overpriced and overrated. Journals provide piss poor quality of service in the majority of instances.

A few additional references, information found by searching for the contract number (indicating it is giving out several millions of dollars, which I deduce considering all the references):

https://projects.iq.harvard.edu/muri_metasurfaces/overview

https://projects.iq.harvard.edu/muri_metasurfaces/publications

https://projects.iq.harvard.edu/muri_metasurfaces/people/federico-capasso

This chunk has given out $3M so far:

https://www.nsf.gov/awardsearch/showAward?AWD_ID=1541959