Science > Physics > The New Black: A nanoscale coating reflects almost no light
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Science > Physics |
| User: |
"Sam Wormley" |
| Date: |
03 Mar 2007 08:30:15 PM |
| Object: |
The New Black: A nanoscale coating reflects almost no light |
The New Black: A nanoscale coating reflects almost no light
http://www.sciencenews.org/articles/20070303/fob3.asp
The velvet background on a painting of Elvis looks black because it
reflects so little light. But getting a surface to reflect no light
at all is surprisingly difficult. Now, researchers have created a
virtually reflectionfree surface by coating it with filaments only a
few billionths of a meter thick.
Improved antireflective surfaces might have many uses. For example,
they could eliminate light-wasting reflections in fiber-optic
telecommunications, or the surfaces could brighten low-power
light-emitting diode (LED) lamps.
Applied to a clear surface, the coating would make a lens absorb more
light, increasing its transparency. On an opaque surface, the
filaments would make a silicon solar cell, for example, almost
perfectly absorbing.
See: http://www.sciencenews.org/articles/20070303/fob3.asp
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| User: "Ian Parker" |
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| Title: Re: The New Black: A nanoscale coating reflects almost no light |
04 Mar 2007 03:43:13 AM |
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On 4 Mar, 02:30, Sam Wormley <sworml...@mchsi.com> wrote:
Applied to a clear surface, the coating would make a lens absorb more
light, increasing its transparency. On an opaque surface, the
filaments would make a silicon solar cell, for example, almost
perfectly absorbing.
See:http://www.sciencenews.org/articles/20070303/fob3.asp
The mechanism is in fact interfence. You can eliminate reflections but
at one wavelength. This has been done for yonks. This point I think
(made very badly in the article) is that a series of layers of atonic
thichness could have imporved properties and sharper transmission
bands than ordinary interference filters.
- Ian Parker
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| User: "Cant Please Morons" |
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| Title: Re: The New Black: A nanoscale coating reflects almost no light |
05 Mar 2007 12:10:50 AM |
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Ian Parker wrote:
On 4 Mar, 02:30, Sam Wormley <sworml...@mchsi.com> wrote:
Applied to a clear surface, the coating would make a lens absorb more
light, increasing its transparency. On an opaque surface, the
filaments would make a silicon solar cell, for example, almost
perfectly absorbing.
See:http://www.sciencenews.org/articles/20070303/fob3.asp
The mechanism is in fact interfence.
in Toronto? another export bites the floor.
You can eliminate reflections but
at one wavelength. This has been done for yonks. This point I think
(made very badly in the article) is that a series of layers of atonic
thichness could have imporved properties and sharper transmission
bands than ordinary interference filters.
- Ian Parker
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| User: "Chris L Peterson" |
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| Title: Re: The New Black: A nanoscale coating reflects almost no light |
04 Mar 2007 09:52:21 AM |
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On 4 Mar 2007 01:43:13 -0800, "Ian Parker" <ianparker2@gmail.com> wrote:
The mechanism is in fact interfence. You can eliminate reflections but
at one wavelength.
The mechanism is _not_ interference. This is a type of Rayleigh coating,
that works by having an index intermediate between air and the optic.
They are improving on this my adding more layers, with progressive
indexes from air to the optic. The more layers they add, the closer the
coating comes to having a perfect graded index. The AR performance of
this type of coating will be largely independent of wavelength, with a
tiny residual caused only by the fact that the coating material is not
going to have the same index across the entire source band- no material
has zero dispersion. If they could grade the dispersion as well, varying
from air to the optic, the surface would have zero reflectivity at all
wavelengths.
There's nothing in the article to suggest they are relying on
interference (although they see a small effect from it). The coating is
made up of 5 layers adding to one (short) wavelength, and the index
varies monotonically, rather than alternating in value as a multilayer
interference coating does.
This has been done for yonks.
Gradient index coatings have been known about for a long time, but they
have never been practical. This paper isn't reporting on a new concept,
but a new method of producing these coatings (which may or may not turn
out to be practical).
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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| User: "Helpful person" |
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| Title: Re: The New Black: A nanoscale coating reflects almost no light |
05 Mar 2007 06:47:08 AM |
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On Mar 3, 9:30 pm, Sam Wormley <sworml...@mchsi.com> wrote:
The New Black: A nanoscale coating reflects almost no light
http://www.sciencenews.org/articles/20070303/fob3.asp
The velvet background on a painting of Elvis looks black because it
reflects so little light. But getting a surface to reflect no light
at all is surprisingly difficult. Now, researchers have created a
virtually reflectionfree surface by coating it with filaments only a
few billionths of a meter thick.
Improved antireflective surfaces might have many uses. For example,
they could eliminate light-wasting reflections in fiber-optic
telecommunications, or the surfaces could brighten low-power
light-emitting diode (LED) lamps.
Applied to a clear surface, the coating would make a lens absorb more
light, increasing its transparency. On an opaque surface, the
filaments would make a silicon solar cell, for example, almost
perfectly absorbing.
See:http://www.sciencenews.org/articles/20070303/fob3.asp
I believe that the first anti reflection coatings were made
chemically. The glass surface was chemically treated in a manner to
remove most material at the surface and less as the chemical
penetrated the bulk material. This results in a varying refractive
index. Such a profile (if perfect) would have zero reflectivity at
all wavelengths. This is one way to make low radar reflecting
surfaces work. The biggest downside is that the surface is very
delicate.
Please visit my web site at www.richardfisher.com
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