Metamaterials and Left-handed Materials

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In summary: OK, so I guess the presenter didn't really do anything. He found a focusing point to the waves on the opposite side of the lens, though, somehow.
  • #1
hola
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I was at a high school science symposium, and some kid presented about metamaterials, a structure that shows a negative index of refraction, n. So I think his project was pretty good and all, and he had a good understanding: he had apparently created a new composite structure with neg. n without using split ring resonators.

But in the questions session, I was surprised that some judge totally flamed him. He thought that a metamaterial was impossible to construct, and he questioned the presenter on how a wave could travel in one direction, and carry it's energy in another. I see now that this is a consequence of the reversed Poynting vector in a metamaterial. Anyone care to explain how this is possible?

Another few questions I had:

What are the properties of a material with only one parameter of permittivity or permeability is negative? I know n is equal to the root of permittivity and permeability, so how can you take the root of a negative number?

Also, what is the difficulty in creating a LHM in the optical frequencies?

Thanks for help!
 
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  • #2
Er.. are you sure a "kid" created such a thing? How in the world was he able to do it without using split-ring resonator? What element causes the negative magnetic permeability? How did he test it? At what frequency? Did he have a horn antenna for a pickup? Did he show a transmission curve?

I had a graduate student who had to build such a thing to work in the microwave range. It isn't trivial. Even testing it isn't trivial!

Zz.
 
  • #3
He used two perpendicular cross wire resonators.

He said that as long as these copper wires didn't touch, they would act as an interacting pair. Something about an LC resonator. At a frequency higher that the resonance frequency, permeability is drawn negative by the magnetic field. I think his design worked at 12.5 GHz.

But, how does the Poynting vector make sense?
 
  • #4
Oh, I also should mention, looking at his abstract, that he had source and receiving dipoles to find the strength of the exiting waves.
I think he had a transmission map to find the resonance frequency.

He generated a EM wave field strength map, and found a focus point.
 
  • #5
hola said:
He used two perpendicular cross wire resonators.

That won't produce negative permeability. I know. That's what we constructed. We had wire arrays. But this only produces negative permittivity. That's why we also needed an array of split-ring resonators that were etched on printed-circuit boards.

Zz.
 
  • #6
OK, so I guess the presenter didn't really do anything. He found a focusing point to the waves on the opposite side of the lens, though, somehow.

But how about Poynting vector? And why is it difficult to create a LHM at optical frequencies? Also, what about materials with only one parameter negative?

Zz, may I ask where you've done work with metamaterials? Since it's new, I imagine only a few institutions work with it.
 
  • #7
hola said:
Oh, I also should mention, looking at his abstract, that he had source and receiving dipoles to find the strength of the exiting waves.
I think he had a transmission map to find the resonance frequency.

He generated a EM wave field strength map, and found a focus point.

It is not that simple.

If he was looking only at the transmission, he need to show two different curves first. He has to show, using the wires, that in the frequency range where the permittivity is negative, there's no transmission. Then he has to show, using the split-ring resonators, that in the range where the permeability is negative, there's also no transmission. Now, here's where it gets tricky. He has to hope that, based on his construction, these two ranges overlap!. If they do, then when they are put together as a single structure, somewhere where they overlap, what used to be no transmission now actually show a transmission. This is one evidence for such left-handed property.

Zz.
 

1. What are metamaterials?

Metamaterials are artificially engineered materials that have unique electromagnetic properties not found in nature. They are designed to have specific responses to electromagnetic waves, such as light, sound, and radio waves.

2. What are left-handed materials?

Left-handed materials, also known as negative index materials, are a type of metamaterial that exhibits a negative refractive index. This means that they can bend light in the opposite direction of traditional materials, resulting in unique optical properties.

3. What are the potential applications of metamaterials and left-handed materials?

Metamaterials and left-handed materials have a wide range of potential applications, including advanced optics and imaging, cloaking devices, and improved antenna and sensor technology. They also have potential uses in energy harvesting and storage, as well as in medical devices.

4. How are metamaterials and left-handed materials created?

Metamaterials and left-handed materials are created using advanced fabrication techniques, such as nanofabrication and 3D printing. They are made up of carefully designed structures at the nanoscale, which give them their unique properties.

5. What are the challenges in developing metamaterials and left-handed materials?

One of the main challenges in developing metamaterials and left-handed materials is finding ways to fabricate them on a large scale, as current methods are often expensive and time-consuming. Another challenge is finding ways to tune their properties to meet specific application requirements.

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