The invisibility cloak may not be so far off. The secret lies not in the composition of the surface material used to render an object undetectable but in the material's structural design properties. A new class of material has been developed with surface features designed to respond to EM wavelengths such that the waves pass into and through the material, following its contours as they pass around an object then exit in the same orientation and direction as they entered.
Thus far, metamaterials, as these unusual structures are called, have been designed to respond to microwaves and acoustic waves. 'Respond' actually refers to the material's unique property of providing a negative refractive index, whereby the EM waves that pass through it are refracted in the direction opposite that of the normal refractive behaviour of transparent materials such as glass and water. In a sense, the material acts as a three-dimensional waveguide wherein the behaviour of the EM waves passing through it is determined by the dimensions of its internal structures. A 'cloaking device' has been demonstrated which effectively prevented a copper cylinder from being detected by microwave imaging. It follows that cloaking of stealth planes from radar is the next likely application. Currently the technology does not exist to fabricate similar devices to respond to the higher frequencies of the visible wavelengths in the optical spectrum but their eventual development is probably not far off. In fact, researchers at the U.S. Department of Energy's Ames Laboratory have developed a candidate material with a negative refractive index for visible light. Wavelengths at the red end of the visible spectrum, about 780 nm, can be attenuated by the material. Many challenges still need to be met before this metamaterial can be considered practical. However, since this milestone represents the most significant improvement over the six years since the discovery of the first metamaterial, those challenges will most certainly be overcome within the short term.
Acoustic metamaterials promise serious improvements in the resolution of ultrasound images because they can be designed to function as acoustic lenses which can focus sonic waves. Furthermore, there is no shortage of application in the field of sound damping and the fabrication of baffles to reduce noise pollution from heavy machinery and loud engines. In short, acoustic metamaterials will allow engineers to control sound waves.
There are no natural materials with a negative index of refraction. They must be engineered to have this property. An excellent explanation of the wave properties of metamaterials is provided by this slideshow by Faustus Scientific Corporation, where the images of two types of metamaterials below can be found. The company manufactures Multi-Purpose Electromagnetic Field Simulation Tools (MEFiSTo™) which model the dynamics of electromagnetic fields in user-defined environments.
One important implication offered by metamaterials is that they offer the possibility of providing optical resolution below the diffraction limit. What this means is that ultimately we will be able to image objects optically that are smaller than the smallest wavelength of visible light. Images resolved by conventional optics do not include "evanescent" waves, additional detail carrying EM waves which comprise the energy losses that occur as the light passes through a conventional lens. Physicists have long known about this phenomenon. It was thought that a lens made out of a material with a negative index of refraction could in theory refocus these waves to provide detail not otherwise available. Enter the 'Superlens'. The actual development of a lens with a negative index of refraction was first proposed by the British physicist John Pendry in 2000, 30 years after Russian physicist Victor Veselago first conceived of the idea. The actual demonstration of such a metamaterial was achieved by a team headed by principal investigator Xiang Zhang, UC Berkeley associate professor of mechanical engineering, in 2005.
Consider the ultra high resolution imagery displayed by high-end flat panel LCD TV's showing a Blue-Ray DVD program and then you can readily understand the basic idea that by human hands technology can indeed enhance and supplement reality far beyond nature's intentions.
Tuesday, January 22, 2008
Amazing properties of metamaterials
Monday, January 21, 2008
And they said it couldn't be done!
As my claim in my old About Me sidebar profile declares, I think that I have the fundamental nature of reality pretty well figured out, and I still stand by that claim. Most of my own practical and logically inspired insight and theorising concerning the nature of creation and physical phenomenon in general are empirically supported by the efforts of others, classical heroes among them, many of whom might no doubt still have a few lingering questions regarding their own interpretation of the results of their experimentation.
One of those theories concerns the nature and the behaviour of light, on which topic I have written about on occasion here and there.
In a nutshell, I maintain that photons as particles do not really exist, nor do such particles shoot across space at the speed of light; that the principle idea put forth by theoretical physicists that photons have no mass is merely a convenient accommodation to explain away their velocity, since relativity theory states that any object travelling at 100% of the speed of light has infinite mass. I describe the propagation of light as the result of atomic and molecular interaction based on like-polar reaction in the medium setting up resonant oscillations conforming to the properties of the surface atoms/molecules that make up the objects that we see, and that all the characteristics of those surface atoms/molecules are modulated on the electron orbitals of all of the atoms/molecules in the medium through which those waves are propagated. As Philip Bucksbaum of Michigan University has proved, the electron is capable of storing an infinite amount of information. This agrees with the explanation of how light waves propagate. The retinas of our eyes decode the information that falls between the extremes of the visible frequencies of those oscillations, but the origins of the original waves that produce those frequencies lie in particles much smaller than the smallest wavelength of visible light. Even conventional optical microscopes cannot resolve most viruses, which are comprised of a million or more atoms. So in effect, we are not even decoding the fundamental frequencies of those oscillations, but rather distant subharmonics of their fundamentals, which idea incidentally also supports Einstein's famous equation E=mc², which states that there is a tremendous amount of energy contained within the atom.
In a previous post I described the technology whereby the effective wavelength of visible light was reduced to about 8% of its normal wavelength while the frequency actually remained the same, in my discussion of a field of research called plasmonics.
Using an altogether different technology, scientists have now managed to illuminate very small objects like viruses by using a special lens to focus a 500 nanometer beam of visible light down by a factor of ten to a beam about 50 nanometers in diameter. The principle is called superlensing, and involves constructing a transparent plate on which opaque circles are arranged concentrically in a specific pattern. A beam of light passing through it dies very quickly, halving every 5.5 nanometers away from the plate for a 50 nanometer beam, but that is moot considering that the applications of the phenomenon fall in the nano scale realm, well within the capabilities of current nano-fabrication technologies.
All these new developments only serve to bolster the gradual paradagm shift. No longer do research physicists mean particles when they talk about photons. We now refer to "photon wavelengths" when talking about electromagnetic radiation.
The most lucrative potential application of superlensing technology is in the development of even larger storage capacities for DVD's and compact discs than now exist, which are currently limited by the size of the laser dot used to encode the individual bits.
I foresee a future of strange supercomputers incorporating all the cutting edge technologies of quantum computing, plasmonics, and superlensing whose computing speeds exceed even those of real-time quantum and biological behaviours. Only then will we be able to seriously consider investigating the art of the coincidental juxtapositioning of spatial co-ordinates within the fixed framework of space/time - ie. the teleportation of life-sized objects in this macrocosm.
Beam me up, Scotty!
