Silicon coatings for anti-dispersive optics

[doublevodka]

https://phys.org/news/2021-11-simple-silicon-coating-long-standing-optical.html

Interesting article and has the potential to make some improvements in telescope optics if the coating process can be replicated on a large scale.

[Cozzy]

Interesting read, thanks for the link.

the last paragraph makes it sound like any 'Joe Bloggs' could do it which will be unlikely, but I look forward to seeing how/if this coating is implemented in scope manufacturing. it can only be a positive.

[robin_astro]

The reference given at the foot of the article appears to an unrelated paper. Here is the original paper 

https://www.nature.com/articles/s41467-021-26920-6

 

[wimvb]

On 12/11/2021 at 10:21, Cozzy said:

the last paragraph makes it sound like any 'Joe Bloggs' could do it which will be unlikely, but I look forward to seeing how/if this coating is implemented in scope manufacturing. it can only be a positive.

If you have a few million to spare. Quantum dots like these are hard to make. You need a state of the art semiconductor fabrication facility to make them on a large scale on a flat surface. The curved surface of a lense makes it even harder. The article talks about laser light which is very narrow band, similar to a narrow Ha filter. So how will it work with white light? (I haven't read the original article yet. Maybe some of these questions are answered there.)

[GalaxyGael]

Interesting, and Fred Capasso always comes up with ideas like these. Periodically arranged nano-objects are best made this way, but time consuming and expensive. They can be made more cheaply using pattern formation between tow different polymer, and those structures are then coated which avoid the lithography or electron-beam writing stages. We do this in our lab sometimes to make patterns such as these but also more complex periodic structures that take too long on e-beam systems (and too expensive to be honest).

However, the processes involved are available in most silicon fabrication facilities, where the scaling of the application would likely be done. Canon Optron, Seiko Epson in Japan as two examples, are largely material (silicon, optics and other) fabrication facilities, but not for computer chips.

Either way its a clever proof of concept, slowing down red light group velocity (like a photonic crystal) but it seems to be employed on the flat surface of optical elements in this demonstration. Because this structure is periodic, they will have to deal with Fabry-Perot resonances in broadband white light, and a local drop is transmission from a photonic band gap. It can be suppressed or hidden with Mie resonance interaction for really short laser pulses at a specific frequency, and they seem to have done that, but haven't read the paper in full.

If it were employed in telescope optics, it would likely need a modification of the shape or lenses and their arrangements. While the fluorite or low ED and their mating lenses deal with color, it is by control dispersion among other effects, so it would be infesting to see a model of lenses using the capability from this paper would look like to obtain the ideal color corrected flat field.

[GalaxyGael]

On 12/11/2021 at 09:21, Cozzy said:

the last paragraph makes it sound like any 'Joe Bloggs' could do it which will be unlikely, but I look forward to seeing how/if this coating is implemented in scope manufacturing. it can only be a positive.

Unfortunately a very common problem in press releases of scientific papers, especially those from magazines and online websites who job it is to promote science and discoveries. The hyperbole, not in this case but far too often, could leave you nauseated especially if you know the details of the work in a paper/patent/report. 

This stuff wont be a spray on coating for any of us to use  Would like to hear opinions of CaF2 growers, LZOS and others. The mechanical/scuff stability of this coating was not addressed and we also make structures like this routinely for different reasons. They are not very robust if on an outer surface and the long range periodicity or patterning of the silicon pillars needs to be maintained.