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Physicists Close in on 'Superlens'
An anonymous reader writes "In Oregon, physicists have developed a material for creating a real superlens that in theory could attain a one-nanometer visual resolution. The idea is to use exotic materials to create "negative" refraction of light, which literally means steering it in the opposite direction of that found in the natural world."
I'm not sure about the resolution of the previous "negative refractive" lenses, but these things have been around for a few years. Pendry (I think) was one of the first to come up with the split-ring "metamaterial" and show that it can work, but the concept for these things has been around since Veselago came up with them, oh, about 40 years ago. People (including my advisor) have recently been proposing or demonstrating "negative refraction" acoustical materiaals, too. As far as I can make out from the summary, the OSU work is notable because this lens might work with optical frequencies, rather than in the radio and microwave regime, as previous optical metamaterials had to do.
Incidentally, people will find better information by searching for "left-handed" and "metamaterial" rather than "negative index" on the various sites.
Check the NYUD link in case of slashdotting of TFA.
How can you really study atoms at the nanometer scale? Atoms are sub nanometer. The use in obsevation lies in some large molecule on large molecule action. The best use would be in making smaller features with photolithography. It may also be useful in quantum computing applications.
Being a grad student in these kind of things (optics) I just want to clarify that these super-"lenses" do not behave at all like normal lenses. Most importantly, it is impossible to obtain magnification, the image will always be exactly the same size as the object. So it's not really fair to think about them as "lenses".
A very similar thing is dispersion compensation in fiber-optical communications where the dispersion of one fiber is compensated in another with dispersion of opposite sign. This way, a signal can go through the two fibers without being distorted by the chromatic dispersion. Dispersion and diffraction (i.e. free space light propagation)are mathematically virtually the same thing, and the negative-index material is equivalent to having a fiber with dispersion of the opposite sign. So perhaps it's more right to think about the super.lenses as "diffraction-compensators"?
The problem with zone plates are:
- INSANE chromatic abberation (linear z-dispersion with wavelenght)
- Multiple orders of refraction (the spot that has the 1st order in focus also shows the higher orders unfocused, so the effective spot is MUCH larger)
- VERY low efficiency (talk about 1/100ths of the photons to actually get where they are supposed to)
They are nice were there is nothing else available (or possible because of beamline restrictions, like when there is no space for glancing angle mirrors &co), but sadly they arent that good...
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
You can find more information about this research at Podolskiy's web page. It looks like the web site has some good information, including Java applets showing how a superlens should work. Incidently, I am an undergrad physics student at OSU and I talked to Poldolskiy about doing some research for him last summer, but it didn't work out. It's nice to see he got something published on this though - he was explaining it to me last year but I can't remember much of it now.
It's not quite the first time. Zhang's group in Berkeley published a paper in spring last year (Science 308, 534-537) describing experiments on the silver superlens, which works at optical frequencies. There have been other similar experiments since then.
It should also be noted that these negative index materials rely on resonant behaviour, and are consequently highly dispersive.
I remember something about this from Physics World, around five months ago. That article reports experiments in which a resolution of a quarter of the wavelength was achieved. ... decays quickly as a function of distance from the object". A lens with a refractive index of -1 causes an exponential increase in the near-field waves as they pass through the superlens, and so the information can be more easily recovered, giving an image with better resolution than if only the far-field light was used.
As far as I can tell, the idea is that diffraction doesn't work quite how it's taught in classrooms: there is a standard "far-field" portion, which is limited to a resolution equal to the wavelength of the light; but there is also a "near-field" portion, which "contains all of the sub-wavelength spatial details about an object, but
The object, lens and image all have to be located within the near-field, less than one wavelength in size, else the waves decay too much - that limits the practical applications, but it could apparently be useful for the optical storage industry.
You can't peek into the eye of a needle by throwing bowling balls at it, but you can very well thread a long thread through it, even if the volyme of the thread is far larger than the volume of the eye of the needle. You just need a coherent light source exactly perpendicular to the surface. Then your only problem is diffraction, which is already better mentioned by other posts.