Realizing Near-Optical Magnetism 39
Bill Kendrick writes "Researchers have created terahertz magnets from non-magnetic materials. "Researchers were able to create magnetic activity at nearly optical frequencies using common non-magnetic materials such as copper." UCLA also has a press release."
Eric Lenscherr (Score:4, Funny)
Re:Eric Lenscherr (Score:2)
Re:Eric Lenscherr (Score:2)
hmm (Score:5, Funny)
How those fools laughed when I created my non-magnetic tinfoil hat!
uhhhh.. (Score:4, Funny)
The split ring resonators that make up the periodic array were fabricated using a unique self-aligned microfabrication technique called photo-proliferate-process.
"
I think I speak for everyone here when I say.... oh.
Re:uhhhh.. (Score:2, Funny)
Magnetism has a frequency? (Score:3, Insightful)
Re:Magnetism has a frequency? (Score:5, Informative)
Well you know how on an MRI the picture looks sort of fuzzy? Well now they can get it almost as sharp as if they were looking through an optical microscope. So that means they could resolve inside of the cells of your brain
Re:Magnetism has a frequency? (Score:1)
Re:Magnetism has a frequency? (Score:2)
Re:Magnetism has a frequency? (Score:5, Informative)
As you increase the frequency of the magnetic field, all magnetic materials stop behaving like magnetic materials. This article is about pushing that envelope higher.
Re:Magnetism has a frequency? (Score:5, Informative)
Usually electromagnets are of lower frequency than radio because the core (e.g. iron or ferrite, they are used to greatly boost the power of the magnet) takes some time to change polarity. In this case they've managed to get it switching trillions of times a second which probably has some applications in research.
Someone with better experience than I can explain the difference between traditional magnetic fields and radio waves, but as I understand it, radio waves are sort of like a magnetic field creating another magnetic field of opposite polarity which creates another, etc... electric fields are involved too. Radio waves in general reach much further than near-field magnetics.
Todays lecture is on electromagnetic radiation.... (Score:2, Informative)
Xrays, Ultra-violet, Visible Light, Infared, Microwave, Radar, UH
Re:Magnetism has a frequency? (Score:2)
You get an electromagnetic field surrounding magnets. This field is typically at very low frequencies. It does fun things like causing electric currents in wires passed through the field. Also, current passing through wires causes electromagnetic fields. If you reverse that, you can detect currents passing through wires in the field (because it changes the field). If you put some physical object in the magnetic field, the field causes current to flow in anything that is
Why we care (Score:5, Informative)
Over the years the useful frequencies for radio waves have gotten shorter and shorter. Shorter frequencies have a lot of benefits and drawbacks. The biggest benefit is almost unlimited bandwidth. Drawbacks include range and lack of technology. Even with the drawbacks, we see higher and higher frequencies used in everyday devices.
Both light and radio are electromagnetic waves (EM). There's a gap between light and radio. It's between infrared and microwaves. These are the terahertz frequencies. You can do neat things with terahertz. It's a little like light, a little like radio.
The problem is the technology. It's still hard to do anything at those frequencies. This article is about closing that gap. Closing it from the low frequency (radio) side where magnetism plays a larger roll.
I have a real beef to pick with this article (Score:5, Insightful)
Materials that exhibit a magnetic response at terahertz (THz) and optical frequencies are rarely found in nature..
Response to what? I don't know if he's shining electromagnetic radiation at those frequencies on the material and somehow gets a magnetic field out of it, or what. (Maybe he's just shaking it that fast?) Or how about this:
The split ring resonators that make up the periodic array were fabricated using a unique self-aligned microfabrication technique called photo-proliferate-process.
What the hell does it tell me to know what the name of the process is? He could just as well have called it "masturbating bear algorithm" and the amount of information that provides to me would have been the same. It would be much more fruitful to, say, include a short description of how they accomplish that.
I thought the ucla website would be more informative, but they just have the exact same article.
Eurekalert... More information (Score:5, Informative)
"In normal materials the constituent atoms and molecules determine electrical and magnetic properties; they are much smaller than the wavelength of light so only the average response of the atoms matters. In the new materials an intermediate or meta-structure is engineered on a scale somewhere between atomic dimensions and the wavelength of radiation. The properties of metamaterials are not limited by the periodic table and scientists can now engineer a huge range of electromagnetic responses that can be tailored to anything allowed by the laws of electromagnetism..."
The first design for a magnetic metamaterial was the 'Split Ring' structure. "A simple, plain ring of metal gives a magnetic response, but in the wrong direction....By cutting the ring the flow of current is interrupted by capacitance across the gap which, together with the inductance of the ring, makes a tuned circuit whose resonant frequency is determined by the inductance and capacitance. It is well known that a resonant structure responds with opposite signs on either side of the resonant frequency. Hence by tuning through the resonance the desired negative magnetic response is obtained: positive or negative."
The split ring structure "looks like a small letter 'C' inside a larger letter 'C', with the smaller C turned to face the opposite direction...many Split Rings brought together in organized 2D or 3D grids form a magnetic metamaterial." The material can be tuned for specific frequencies by changing the size and layout of the split rings. Here [ucsd.edu] are [ucsd.edu] metamaterials tuned to microwave frequencies, and the Terahertz materials used "a special 'photo-proliferated process' that deposited the 3 micrometer-wide (0.003 mm) copper rings on a quartz base."
Pretty cool stuff..."So far we have only seen negative refraction at microwave or GHz frequencies but some of the most exciting applications in sensing, communication, and data storage would be at higher frequencies... But the really valuable applications have yet to be dreamt of. Think back to when the first lasers were made, the reaction was that they were just incredible, but what the hell would we do with them?"
Re:I have a real beef to pick with this article (Score:2)
magnetic susceptibility (Score:4, Informative)
Re:magnetic susceptibility (Score:2)
Is this like saying something to the effect of "the material cannot change polarity fast enough" or "the faster you want the material to change polarity, the harder it is"?
I'm just spouting-off, because I can't pretend to comprehend this article quite yet. The way I'm seeing it, though, is that, normally you have a bunch of atoms in a material all resonating at some (low)
Amazing how RTFA still doesn't help (Score:3, Interesting)
So what do you do with these, anyway? Make a fiber-optic transformer? What will the impact be on incident light? Will it have any interesting optical effects to the naked eye?
Re:Amazing how RTFA still doesn't help (Score:3, Informative)
Wouldn't help for MRI either (Score:5, Informative)
- MRI machines operate at a frequency of MHz, which have wavelengths on the order of 10 meters and up.
- Medical MRI scanners have resolutions on the order of millimeters.
- Ergo, the resolution of an MRI scanner is not limited by the wavelength of the RF frequencies involved.
The way an MRI works is by the use of "gradient coils" which shift the distribution of the magnetic field through the volume being scanned. The precession frequency of nuclei is a function of the field strength, so the scanner can "listen" to signals from many areas at once by listening for different frequencies; the steeper the field gradients, the sharper are the differences in frequency with location. After scanning through the volume you wind up with a whole lot of data which relates signal returns to different centers of field strength, and using matrix algebra you can extract the actual prevalence of various atomic species at given points in the volume. (Incidentally, the gradient coils in an MRI are driven at audio frequencies; the amplifiers often have hundreds or thousands of watts behind them, and there is more than a little mechanical coupling to the outside. I have heard about nutty people playing "In A Gadda Da Vida" over an MRI; the frequency response sucked, but the bass could be heard a long way through the building.)This is not unlike a CAT (Computerized Axial Tomography) scan, except that the MRI is inherently a 3-D operation to some degree while CAT is 2-D and builds up images in slices.
Applications (Score:5, Informative)
Terahertz frequencies are extremely useful for such things as imaging. You might remember, for example, this [slashdot.org] Slashdot post regarding advances in using terahertz frequencies to improve sreening devices in airports.
The downside to terahertz frequencies is that they are difficult to generate. The reserchers involved here seem to have simplified this somewhat by creating a material or "metamaterial" that will readily emit tunable frequencies in the terahertz range. This hopefully will make it all the more easier to build such imaging devices.
So, while we can't yet make all the molecules in the hostess' dress jump one foot to the left yet, we will be able to more easily make a device that will be able to see through her dress.
Re:Applications (Score:2, Interesting)
Re:Applications (Score:3, Funny)
Come on, man. You responded to a post about seeing through dresses by asking about chemical research. I think I speak for all of Slashdot when I say, "I am so dissapointed in you." You're geek credentials are this close to being revoked, mister!
At least have the decency to start a new thread next time.
On a similar topic (Score:1, Interesting)
Probably a stupid question but.... (Score:1, Interesting)
And build an invisibility cloak... (Score:1)
Re:Probably a stupid question but.... (Score:2, Informative)