Slashdot Mirror
Metamaterial Forms Near-Perfect Mirror
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.
So, it's a nearly perfect mirror for a specific wavelength?
So, more useful for lasers than say, optics?
That's some crazy stuff.
Lost at C:>. Found at C.
I wonder what "somewhat costly" is in this context. I would think working with nanosized polystyrene beads and etched silicon cylinders would be somewhat costly too, but that's just me...
This isn't twitter, don't fucking post shit behind URL shorteners.
There's no fucking reason for that.
Many solar cells use reflectors to focus sunlight on the cell. This could be another good application of this technology.
Is 99.7% enough for Hubble mirrors and all that?
A decent sci-fi read by Evan Currie, the book has a concept similar to this for the purpose of camouflage and defense against lasers. I wonder how longer it'll be until researchers can tune the wavelength dynamically as an active laser defense, camouflage or as protection against stellar radiation. Don't get me wrong, mirrors are, you know, cool and all...
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.
I wonder what the Q is and whether these might be used as highly frequency selective mirrors to split out different wavelengths of light, for example for wavelength division multiplexing in some way that is an improvement over current approaches ?
Nullius in verba
Where exactly does one buy off the shelf nanosized polystyrene beads?
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 up a mountain with 10 flashlights each with a different color filter on it. They can use "flash light Morse Code" to have 10 simultaneous conversations with another similarly-equipped group of Boy Scouts hiking up another trail (within line-of-sight of course) without interfering with each other as long as the Boy Scouts at the receiving end can tell the colors apart, either with the naked eye or, if they are color-blind, with the aid of an instrument such as a filter that blocks all light not of the desired color. Now extend this to using very-narrow-band-pass filters, tight-beam optics to create low-spread light beam (not as good as a laser, but it would work over reasonably short distances), and sophisticated sensing equipment to account for the signal loss, and you can probably have hundreds if not thousands of different light frequencies, with the transmitters all bundled together in a single location and the receivers all bundled together in a single location.
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
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.
I can't help but wonder whether this kind of mirror could be used to produce a highly collimated laser beam. The more regular the surface of the mirror, the more parallel the rays of light emitted. I wonder if this technology could be effectively used to make a weapon that requires less power (the light being more highly focused on the target.) Perhaps the Star Wars concept of the Reagan years has returned?
...don't work that way.
The high efficiencies are gained through capturing a large portion of the available spectrum. these mirrors only reflect a specific frequency range.
Just focussing 15 times the sun on a cell would probably damaga/melt it permanently anyway.
When solar cells get too hot they hardly produce any enery at all so keeping them at moderate temperatures is important.
And hardly any commercial system uses mirrors for concentration because cooling them is way to complicated for small systems.
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?
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