Metamaterial Forms Near-Perfect Mirror 64
New submitter JMarshall writes: Researchers have made near-perfect reflectors out of a silicon metamaterial. These reflectors could offer a simpler, less expensive way to make high-performance mirrors for lasers or telescopes. Metamaterials typically use nanoscale patterning to create unusual properties not present in the bulk material. In this new method, researchers used off-the-shelf, nanosized polystyrene beads and allowed them to self-assemble into a monolayer with a hexagonal pattern. Using the monolayer as a photolithographic mask, the researchers etched an array of silicon cylinders, each a few hundred nanometers across, onto a wafer. The cylinders act like tiny resonators for a particular light frequency—analogous to the way a given sound frequency will make a tuning fork hum. The array reflected 99.7 % of incident light at their peak wavelength. These simple metamaterial mirrors might one day replace current high-performance reflectors, which are somewhat costly to make.
Hmmm ... (Score:4, Insightful)
So, it's a nearly perfect mirror for a specific wavelength?
So, more useful for lasers than say, optics?
That's some crazy stuff.
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Exactly. They are only useful for reflecting specific wavelengths. They are *not* a replacement for the mirrors used in telescopes, solar power, etc because they do not reflect a sufficient range of wavelengths.
In terms of lasers, well, maybe - as long as the laser uses only a very tight range of wavelengths.
From the description it doesn't seem like there is a way to extend this to handle broader ranges of wavelengths without losing efficiency. One would have to craft an array of cylinders of varying siz
Re:Hmmm ... (Score:4, Interesting)
In terms of lasers, well, maybe - as long as the laser uses only a very tight range of wavelengths.
Yes, most do just that... In fact, I'm not sure if there is a laser resonator that isn't pretty specific to a single wave length. To make a laser, the idea is to create a way to bounce a single wavelength of light back and forth until the photons are all going the same direction at the same time and exit the resonator. It's a lot like how a klystron resonator works when generating large amounts of microwave energy.
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Yes, most do just that... In fact, I'm not sure if there is a laser resonator that isn't pretty specific to a single wave length.
There are "tunable" lasers, you can change their frequency. Most, however, are fixed to just one.
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Yes, but at any given instant they are emitting only one particular frequency (or perhaps more precisely an extremely narrow range of frequencies).
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I programmed and performed laser shows for five years back in the late 80's-early 90's. We used argon, krypton and argon-krypton lasers. They were all multi-wavelength with the argon-krypton lasers giving 20+ visible wavelengths from deep red to deep blue. These mirrors would be useless for laser shows.
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They are also not needed for laser shows. These mirrors are required when power levels increase to the point where a standard mirror starts suffering under the reflection losses, i.e. one of the reasons why above a certain power threshold you are pretty much limited to using prisms and total internal reflection to direct the light.
Also your multi-wavelength lasers only really produce one primary wavelength at a time. The same system which tunes these could be used to switch out mirrors like filters in front
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Yes, most do just that... In fact, I'm not sure if there is a laser resonator that isn't pretty specific to a single wave length.
Many gas lasers have multiple wavelengths, including common ones like argon. Lasers and amplifiers based on Ti:sapphire also have a huge bandwidth, and when creating things like fs pulses, you produce something that requires that bandwidth. Things like supercontinuum sources are also become much more common with a lot of potential uses. Not to mention all of the two,three,four color systems out there that exist because they use frequency multipliers and have a reason to keep all of the wavelengths instea
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One would have to craft an array of cylinders of varying sizes to capture the varying wavelengths, at which point for any given wavelength there is only 1/Nth of the cylinders that reflects it efficiently.
Such an array would have nanoscale structures which have properties not present in the original metamaterial, a sort of higher-order metamaterial. We call such things ... Jeff.
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Saith Wikipedia
Applications requiring higher reflectivity or greater durability, where wide bandwidth is not essential, use dielectric coatings, which can achieve reflectivities as high as 99.999% over a narrow range of wavelengths.
That sounds like something I'd use for lasers. Beats a crummy 99.7%.
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Actually, they seem to be using a mix of sizes, reflecting across a range of wavelengths.
In any case, near perfect mirrors for specific wavelengths are very useful: dichroic mirrors have been in use for a long time.
Somewhat costly? (Score:1)
No fucking URL shorteners ... (Score:5, Insightful)
This isn't twitter, don't fucking post shit behind URL shorteners.
There's no fucking reason for that.
Re:No fucking URL shorteners ... (Score:4, Funny)
Welcome to Web 5.0, where people save photos as GIFs and logos as JPEGs, use 100KB javascript libraries to do the job of a few lines of CSS3 and use URL shorteners without thinking about their users cholesterol.
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Just curious why you care? Is it the tracking?
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Because a Uniform Resource Identifier is just that, an identifier. It is meant to be human-readable and give me a hint about where it will lead me before I click on it. Don't get me wrong, I'm not offended by an image of a guy distending his sphincter, but right now I'm more curious about perfect mirrors than about this particular black hole.
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Solar Cell efficiency (Score:5, Interesting)
Many solar cells use reflectors to focus sunlight on the cell. This could be another good application of this technology.
Re:Solar Cell efficiency (Score:4, Insightful)
I thought so at first, but it seems unlikely:
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Make them cone shaped...
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Or Tesseract shaped! Movies about free energy or time travel or space travel or aliens always end up with some sort of tesseract involved so it must be important!
In case it wasn't obvious, I made that last part up.
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Which part? The part about not being obvious or the part about making up the last part?
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I don't see how making it into the shape of a motorcycle [motorcycle.com] would improve anything.
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If they are not perfectly transparent, then the absorption is probably multiplicative. You can probably put some layers for the primary frequencies you want to reflect, then have a catch-all regular mirror underneath.
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Mylar is ~98% reflective - seems like a less expensive alternative - and it isn't limited to a particular freq.
Dang it man, STOP thinking like an engineer! Less expensive, more efficient, please...
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Mylar is ~98% reflective - seems like a less expensive alternative - and it isn't limited to a particular freq.
Mylar has a poor lifespan, and when you're done with it, it disintegrates into chaff.
Re:Solar Cell efficiency (Score:4, Funny)
That's a problem that marketing can solve. Tell them it's rapidly biodegradable.
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Seems sloppy (Score:2)
Is 99.7% enough for Hubble mirrors and all that?
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Is 99.7% enough for Hubble mirrors and all that?
50% would be good enough for Hubble mirrors if it were half the price. A telescope cares little about such a small change in light intensity, what makes a good telescope really expensive is avoiding all the distortions. 99.7% is 10 to 100 times better than your standard telescope mirror, but that bit about reflecting based off of wavelengths is what would be the problem.
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Have you read Odyssey One? (Score:1)
Is this actually good? (Score:2)
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They toss out the 99.7% number, but in the realm of precision mirrors something tells me that isn't really all that impressive. Now it may be an improvement for the lower grade mirrors at a cheaper cost. But in that sense its a rather misleading headline and article.
Its quite good. In the visible aluminum, silver, and gold are around 95-98% (in the blue region silver is best at 97%, and then gold is better in the red at 98%, and aluminum is better in the UV at 95%).
To have a good reflector in the UV would be great.
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They toss out the 99.7% number, but in the realm of precision mirrors something tells me that isn't really all that impressive. Now it may be an improvement for the lower grade mirrors at a cheaper cost. But in that sense its a rather misleading headline and article.
Yea, and only at one frequency/wavelength too... I'm guessing there are some uses of mirrors that will benefit from this, but only for laser based applications or sensors where a single frequency/wavelength gets you useful information.
How frequency-specific (Score:3)
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Looks like they have seen 99% reflectivity. Q must be on the order of 100 (give or take a pi and a 2). That is OK, but mirrors above 99.99% are commonly available at a single wavelength and I think they can get down to a few ppm with enough effort (and in clean conditions). I haven't worked with low loss mirrors in decades, so I don't know where the state of the art is now.
how about non-visible spectrum? (Score:2)
I can see these for line-of-sight air-path or even in-space/on-the-moon mirrors for laser or other mono-frequency communication methods.
If you can make a cheap mirror, can you make a cheap narrow-band filter in these frequencies? I might want to have a room that blocks all frequencies "from DC to daylight and beyond" EXCEPT for a particular frequency that I use to communicate with the outside world with.
By the way, you don't need lasers for effective mono-frequency communication. Imagine Boy Scouts hiking
What about distributed Bragg reflectors? (Score:3, Informative)
Sure, metal mirrors such as silver may only give you 95-97% reflection. However, dielectric mirrors are pretty common (aka distributed Bragg reflectors) and a quick check on ThorLabs shows some with efficiencies of at least 99.5%. The paper and summary over hype this result by suggesting that these new mirrors will be much cheaper over large scale. Distributed Bragg reflectors rely on multiple coatings of thin dielectrics, which can be scaled to large areas fairly easily and controlled precisely. The presented work uses microsphere lithography, where you need to get tiny spheres to pack closely on a substrate EXACTLY one layer thick. Having tried this process personally, that's a lot more difficult than these papers usually let on, and the frailness of getting the particles to settle over large areas makes scaling to telescope size unlikely.
Oh, and the authors took the easier route and demonstrated a mirror for telecom wavelengths, ~1500-1600nm. To make a mirror in the visible range requires smaller spheres which suffer from poorer packing due to a larger coefficient of variance in the diameter.
Collimation? (Score:2)
Off the shelf? (Score:2)
In this new method, researchers used off-the-shelf, nanosized polystyrene beads and allowed them to self-assemble into a monolayer with a hexagonal pattern.
Off the shelf? Really? Which shelves are these? Is there a nano-materials aisle at my local Wal-Mart? This sounds like an interesting place to shop. Where is it?