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."

They've been around

[gardyloo]

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.

Re:Aww.

[SUB7IME]

Check the NYUD link [nyud.net] in case of slashdotting of TFA.

Re:These would be nice!

[DinZy]

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.

Not lenses - diffraction compensators!

[johst]

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"?

Re:What about zone plates?

[imsabbel]

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...

Re:These would be nice!

[Anonymous Coward]

WTF are you talking about?
First of all electron microscopes are relatively cheap and then you don't get resolutions down to atom-size with electron microscopes. No even close.

http://en.wikipedia.org/wiki/Scanning_electron_mic roscope [wikipedia.org]

More information about their work

[philbert2.71828]

You can find more information about this research at Podolskiy's web page [oregonstate.edu]. 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.

Re:Is that really possible?

[toQDuj]

Well, in a technique unrelated to these special lenses, there is SNOM, or Scanning (Probe) Near-Optical Microscopy, in which an AFM-tip is used through which UV light can be measured (using a fiber). Put a UV source underneath your sample, and use the AFM tip to record an optical image.
The trick is, that the AFM tip is very close to the surface, much closer than the UV wavelength. Thereby the lightwaves to not have the pathlength to interfere and cancel out, and you can get optical microscopy images with a resolution of about 1/10th the wavelength of the used source.

B.

Re:Negative Refraction

[bw_bur]

It's not quite the first time. Zhang's group in Berkeley published a paper in spring last year (Science 308, 534-537 [sciencemag.org]) describing experiments on the silver superlens, which works at optical frequencies. There have been other similar experiments since then.

Re:Its even stranger...

[bw_bur]

This is an element of truth in this. The group velocity and the phase velocity are in opposite directions. The group velocity (which determines the flow of energy, and the direction and speed of information transfer -- and photons) would point away from the boundary, while the phase velocity points towards the boundary.

It should also be noted that these negative index materials rely on resonant behaviour, and are consequently highly dispersive.

Re:Not lenses - diffraction compensators!

[bw_bur]

Yes, you can still build a magnifying lens out of a negative index material. However, a thin flat sheet of this material is already a "superlens"; it doesn't magnify, but produces (in theory at least) a perfect image, with no loss in resolution. Even the near-field (evanescent, exponentially-decaying) components are restored and focused.

Of course, in reality, the resolution is limited by absorption and the length-scale of the artificial structures.

Light doesn't go faster than c in these materials... see some of my other posts on this...

Re:E=MC^2, yo.

[the ed menace]

The effect is largey attributed to Pendry. It was very contentious in the physics community until last year, when it was generally accepted that the eminescent wave was the process by which the light travelled (otherwise you have supraluminal propagation.)

The ramifications of this technology are very large, not just for the optical realm, but for other frequencies also.

Re:These would be nice!

[dillee1]

Not necessarily. All normal material slow down light, and the difference in C at medium interface cause light to bend. The new material that cause light to bend the other way probably means C is higher than C(vacuum). Currently only exotic material like BEC [wikipedia.org] has these properties. These exotic materials are not easy to made/maintain, so are microscope using them.
BTW TFA has no information about what material/technology does this use. Anyone got links?

Re:Is that really possible?

[Excors]

I remember something about this from Physics World [physicsweb.org], around five months ago. That article reports experiments in which a resolution of a quarter of the wavelength was achieved.
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 ... 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.
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.

Re:mandatory Star Trek quote

[cnettel]

A photon is huge only in the sense that its location is unpredictable along the axis of movement (when the wave-length is well defined, as the wave length is directly related to momentum and Heisenberg applies to each dimension). It is not huge in the sense "can't get into an atom", as you can excite or ionize inner electrons with "just" UV or gamma, which are still far above the distance between atoms in a molecule (which is in the same order of magnitude as 0.1 Nm; 1 Ångström).

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.

Re:These would be nice!

[lgw]

Actually, there's a (theoretical) way for light to move faster than 'c' (and not just the phase velocity). Light can (theoretically) move faster than the speed of light in a vacuum, though not by much, between closely-spaced conducting plates. The Casimir Effect [wikipedia.org] effectively reduces the impedance of vacuum below that of "naturally occuring" vacuum. Of course, if true, this would change anything about relativity, it would just mean we've calibrated 'c' imprecisely.

Re:They've been around

[WaterBreath]

Check out the description, and particularly the JPEG images, linked from this site: http://physics.ucsd.edu/lhmedia/whatis.html [ucsd.edu]

The blue lines represent the path taken by light. The red lines represent the surface of the material.

The MPEGs might be worthwhile as well. I couldn't take the time to view them because of my dog-slow web access here at work.

And to clarify on the importance of these developments... No, left-handed materials are not really "new" in either theory or in practical use. What is new is materials that are left-handed for light in the visible spectrum. Recall that index of refraction is dependent on wavelength (or frequency, take your pick). To get left-handed material, you need two rare scenarios to occur at once: one electrical and one magnetic, and it has been more difficult to create this situation with some wavelengths (such as visible light) than with others (such as microwaves).

I believe they have taken to being called "metamaterials" because we need to "build" custom crystal structures tailored for our needs, and they don't tend to grow in "normal" ways.

negative index of refraction: a stick picture

[prurientknave]

normal refraction

light ray
__\__|
___\_|
----------- refractive material boundary
_____|\
_____|_\
      normal
obviously i can't tilt slashes any more =) so this is an example of a refractive index of 1

negative index of refraction

light ray
_\__|
__\_|
----------- refractive material boundary
__/_|
_/__|
      normal

refractive index of -1

This is weird so the hullabaloo

Re:These would be nice!

[Blue Mushroom]

Actually, according to Richard Feynman, light does have the ability to go faster than the speed of light. I'm not sure about the specifics, but for at least some events, there is a an established probability that light will travel between two points in less time than it would take to travel at c. However, at macro scale distances, small variations in the speed of light all cancel out. I read this in Feynman's book QED [amazon.com], which stands for quantum electrodynamics. I highly recommend QED to any non-physicist/non-math-major who wants to gain a better intuitive understanding of the bizarre world of quantum mechanics.