Graphene optical lens 200 nm thick breaks the diffraction limit | Hacker News Reader

Graphene optical lens 200 nm thick breaks the diffraction limit

swinburne.edu.au

182 pointssrikar54 comments

Link to the paper: http://www.nature.com/ncomms/2015/150922/ncomms9433/pdf/ncom...

This is an excellent result. It could also provide an interest boost to solar in terms of $/watt by focusing more light into a small area. Fun times.

Does that 'wear-out' the panel quicker? I assume that more light focused can mean more heat. I'm told people try something similar with mirrors now but it tends to not work out well for the panel itself.

Mirros are only used for thermal solar applications where one heats up oil or melts salts to produce steam to power a normal power turbine.

https://en.wikipedia.org/wiki/Solar_thermal_energy

For photovoltaics you do not want to focus the light for many reasons the cell has a cap per surface area that it can produce, you don't want voltage spikes across the subcells (if it exceeds the overall limits of the cell it will damage it), it wears out the cell, and the cell efficiency drops as the temperature increases.

Mirrors and lenses can be used with photovoltaics as well: https://en.wikipedia.org/wiki/Concentrator_photovoltaics

I know pretty much nothing about it besides the fact that it exists, though.

The power coming from the sun is approximately constant. The power hitting any given spot on the planet is far from constant due to weather, day/night cycles and seasonal shifts. For a given solar installation, there might be a time where the ambient intensity (power per unit area) of the light has the cells biased just-so, converting energy at a near ideal efficiency. Of course then the conditions change and this isn't the case any more. When you run into that scenario, i.e. the sun has moved a bit, it becomes very useful to have some kind of mirror or lens to increase the intensity by collecting more of the light and concentrating it to a smaller area, thus bringing you closer to your ideal operating point.

You're correct that at some point you get undesirable transients, or you just melt your cell. I do that by accident more often than I'd like, by shining infrared lasers at a photo diodes while forgetting that I've left a microscope objective in front. Expensive mistakes.

Now re: the article, if you ask me the really interesting thing here isn't being able to focus light to really small areas per se, but that they've broken the diffraction limit. This means you can form an image of an object that is smaller than a half-wavelength of light. For e.g. red light, that means you can take a picture, an optical picture, of something like, say, a mosfet on a chip. Or a virus. That's quite something.

I'll note however that I could foresee (read: speculate) a scenario where having such a tiny focus, like the solar cell scenario, could invoke a quantum mechanical effect in some special material whereby the light coupling becomes much greater, thus increasing efficiency or something. But that's just science fiction as far as I know.

PS: Sorry if this is patronizing. I know nothing about my audience ;-)

> It could also provide an interest boost to solar in terms of $/watt by focusing more light into a small area. Fun times.

I can't find a single use of this for solar based on the specifications of the lens in the paper. Also photovoltaic really doesn't need focusing it doesn't give you anything because eventually the amount of power you get per surface area is the same so it doesn't matter if you cover a 50 sq/m area with a lens and focus it on a 5 sq/m cell or have a 50 sq/m cell to begin with, also considering that photovoltaic cell efficiency drops with temperature you really don't want to focus any light on them as it will tank your power production.

Thermal solar does need focusing but mirrors will actually work better than this for that application as well because you need to reflect the light to a central location anyhow an a collection mirror does both at the same time.

See https://en.wikipedia.org/wiki/Concentrator_photovoltaics

It seems like every month brings a new "miracle" application for graphene. Are these breakthroughs as surprising for the experts as they are for the layperson? If not, what fundamental properties would allow one to extrapolate its applications?

A molecular scale Fresnel lens! Now we can create retro style nano-projectors, even if the transparency will be thicker than the lens.

Is it really a Fresnel lens? I was thinking it was more of a diffraction grating. The paper describes it as

> The 3D focusing is a result of the interferences of wavelets originated in the lens plane from different zones19, as illustrated in Fig. 1d.

Which suggests it's more about interference than about Snell's law.

That was my guess, too.

Things with rings are generally called Fresnel lenses, even if its not about interference, see:

https://en.wikipedia.org/wiki/Zone_plate

Fresnel zone plate, yes. Fresnel lens, no; they are not lenses.

This does look like a microscopic zone plate. This is not a new idea though, it's how we focus X-rays as most materials don't refract X-rays very well; I guess they just managed to make a really small one. I wonder in what sense it "breaks the diffraction limit".

It does not "break" the diffraction limit. The title is inaccurate. The actual paper doesn't say they've broken the diffraction limit. They only achieve a subwavelength focal point.

I'll make an attempt to mansplain this...

The actual diffraction limit depends on wavelength (lamda) and the numerical aperture (NA) of the lens. Diffraction limit is ~ lamda/(2*NA).

In traditional objective lenses used in confocal scanning microscopes, the diffraction limit has been ~0.5 microns. If you increase NA, it also means decreasing working distance-- to the point where the focal point meets the surface of the lens.

They've managed to increase NA with their zone plate, but since their "lens" thickness is "200 nm", they still have a useable working distance.

Would this also allow visible light microscopes to zoom in further than they currently can?

What is the operating temperature of such lenses? Is this one of those magic devices that only exists near absolute zero?

I assume these can be built into sheets to focus light onto masks. No doubt intel might be interested.

"Just over two years ago, PhD student at Swinburne’s Centre for Micro-Photonics, Xiaorui Zheng, tried fashioning a lens using graphene oxide — a variation of the super-strong, atom-thick carbon material, graphene. The team, led by Associate Professor Baohua Jia, developed a three-dimensional printer that could quickly and cheaply produce the lens using a sprayable graphene oxide solution. Lasers were used to precisely pattern the surface, creating three concentric rings of reduced graphene oxide, which enabled its extraordinary focus"

No I think it's purely geometrical.

imaging if the lens being used for the light field display, could be another solution for a mixed reality display device that the Magic Leap is developing.

Even more "traditional" VR/AR devices would benefit from techniques to make thinner lenses. Advances in optical engineering will have as big a part to play in that sort of thing as processing power and faster chips.

I find the "billionth of a metre thick" phrasing painful, but I guess it's better than if they'd written that it was "a trillionth of a kilometre thick"

They can't be flaunting around big words like nanometer, it might discourage a layperson from reading the article.

Decent point, but most people familiar with metric would work with smaller units than metres and for those unfamiliar with metric, describing it as a billionth of a yard would still sound like a pretty peculiar.

I think describing it as a minute fraction of an inch or centimetre would still be pretty accessible without having to get people to visualize a nanometre.

Or, as we're talking of lenses, fraction of a milimeter.

I only watch the US cable news. How many football fields thick is the lens? 1.823×10^-9 NFL football fields.

Lay people dont understand exponents. Just say its small.../s

three points was enough to laugh for at least an hour. Good enough :-) No?

Right, I thought the usual layperson speak was to compare it to the thickness of human hair or a spider web.

BTW, it's not even 1 billionth of a metre thick. It's 200 nm. That's 0.2 microns. That's 2 * 10^-7. It's 0.2 of a millionth.

They should have just said 0.2 microns instead. It carries just as much actual meaning for the layperson, and it's a lot easier to parse if you are scientifically literate.

I thought convention in SI units was to drop down a level when at less than 1 of a unit..?

A pretty common approach (at least in Canada) is to use prefixes at intervals of 1000 - mm, m, km and then larger unit to one decimal for large values - 700m as 0.7km, 0.9l instead on 900ml, and so-on.

you'll rarely see cl, dg, or hm used here.

Um, 1 billionth of a meter is 1 nm. Saying it's 200 nm (like the paper says) is very different from saying it's 1 billionth of a meter (like the linked article incorrectly says).

Though it's almost unheard of now, a british billion = 1000 * a british million. In that context it does hold, being 2 british billionths of a metre thick.

That said, here we all bascially use the American 'billion' because it makes a more logical approach and allows for dealing with larger numbers more easily.

I thought it used to be: a british billion is a million million i.e. 1,000,000,000,000.

Thus a british billion is 1000 * an american billion.

Nowadays we use the american billion of 1,000,000,000.

Pretty sure we all agree that a million is a thousand thousand.

Wow I screwed up big time. I meant to say it was a million million and I have no idea why I said otehrwise. I'm going to blame tiredness. Thanks for the correction.

OK, we've replaced that with "200 nm". Let's stay on topic now.

> It’s early days, but the new technology has the potential to reduce the size and weight of mobile phones in which cameras are currently dependent on thick and heavy lenses.

Maybe by comparison to this, but hardly anyone cares about the size or weight of their phone camera lens.

Counter example: the protruding camera bump on iPhone 6/6S.

I like to think that's more due to the total thickness of the camera unit, not so much the lens. That, or the required distance between the lens and sensor. Either way, it's a bad design decision, one they're embarrassed of themselves (it's edited out on sideways images of the device on apple's website)

My apartment mate (currently a PhD student in Chemistry) noted that the research is cool, but article this is based on in Nature Communications is pay to publish, so err on the side of skepticism.

A quick Google search found this:

http://www.the-scientist.com/?articles.view/articleNo/41072/...

"At present, researchers can choose an open-access option when submitting a manuscript to the journal, selecting one of three publishing licenses: Creative Commons Attribution 3.0 Unported (CC BY), the more restrictive Creative Commons Attribution-NonCommercial-No Derivs 3.0 Unported (CC BY-NC-ND), or Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA). Authors pay a fee of $5,200 to publish a study under a CC BY license, and $4,800 for each of the other two... Update (September 23): After this article was published, Nature Publishing Group's Amy Bourke responded to The Scientist, noting the flat article processing charge (APC) to publish in Nature Communications: $5,200"

Edit: other users seem to note that the journal is very reputable. I do not know myself, was reporting my apartment mate's reaction since he is much more knowledgeable in the area. It is clear from conversation I mis-understood his response. Apologies.

Most reputable journals charge processing fees when publishing.

And just about all of them have higher fees if you want it published under a creative commons (open) license. Note in GP's quote: the researcher can choose CC for a fee. This option has come available in nearly all peer review journals recently due to recent US grant requirements to open published results. They still have to go through a rigorous peer review. Frankly, GP's mate doesn't know what he's talking about.

It's clear at this point I must have mis-understood his response. He's at a top tier school (CMU) so my guess is he knows what he's talking about. Apologies.

Ah. There is a movement towards no cost journals, but that's not about reputation, it's a very different fight. I'll try to dig up a link.

Here's a good place to start: https://en.m.wikipedia.org/wiki/The_Cost_of_Knowledge

Thanks!!

Uhm, Nature Communications is a subjournal of Nature Publishing Group. There is literally no more reputable publishing group. None. Nature, their flagship journal, is the highest impact factor journal in the world.

I upvoted you, but I want to add text in agreement since such upvotes can't be seen as an endorsement. gavman's warning about the reputation of the venue is unwarranted.

I talked to my apartment mate about it. He said that when he showed the article to his advisor, she had the reaction of "they're pay to publish". I can't speak to the reputability of the journal, just providing his response.

EDIT: sounds like a misunderstanding more than anything.

Here's [0] a link to the rankings of nature journals. Nature Communications is 3rd in general science, and Nature is 1st.

Tim Gowers and the freedom of knowledge group are pushing hard on journal fees.

[0]http://www.nature.com/npg_/company_info/impact_factors.html

Old post :

I can speak to the reputability of your friend's program. The statement is jaw dropping. It is so wrong as to make it hard for me to believe he goes to an accredited university.

As I said in a comment below, he's at a top tier program (CMU), so it's likely I didn't understand his adverse reaction. You mention below his/his advisor's adverse reaction may be about "a movement to move to no cost journals", not about reputation. When I see him tonight I'll ask.

Many top researchers have a grudge against the shortcomings of Nature, especially given its reputation.

They published papers with fairly weak research for overhype many times already.

One example is the infamous Barabasi-Albert paper on the preferential attachment. It contains many false claims, bad math and extraordinary assertions that would be excusable in some vulgarization for TV, much less for a research paper. They could at least have upped the paper before publication.

There are many much worse examples, that you can find on retractionwatch.com among other places.

Nature is not that reputable, I'd put it above science, below JACS. The most reputable journals are cell, and organic syntheses.

If you want to know why org. Syn. is so reputable, check out their description: https://en.m.wikipedia.org/wiki/Organic_Syntheses

That's ridiculous. It's the world's most cited scientific journal. Your opinion doesn't make it disreputable.

You are confusing reputability with a metric of popularity.

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