Meta Materials

It has long been known that very small bits of matter, less than a few tens of thousands of atoms, can exhibit properties quite different than bulk material. Only recently have we had the ability to create structures from materials that are substantially smaller than optical light wavelengths. We call these new materials nano-materials because they involve structures that are measured in nano-meters. Optical wavelengths encompass wavelengths from about 800nm for deep red, to 450nm for violet. Nano-materials have structures that may be considerably smaller than this.

Early applications of nano-materials mostly involved random assemblages of small structures, a good example being nano-particle based lithium ion batteries that can withstand much higher charge and discharge rates because of the high active surface areas made possible using nano-particle construction or new ultra-capacitors, capacitors with energy storage capacity rivaling batteries.

A newer class of material which makes use of the ordered arrangement of nanometer scale structures is now making the production of materials with very exotic properties. These materials are referred to as meta-materials because they possess properties that no natural material could possess.

So far the most interesting properties of meta-materials are their optical properties. Because it is possible to create structures that are much smaller than visible light, materials can be made that appear homogeneous to the incident radiation but have objects that appear to the incident radiation as artificial atoms with very unusual properties.

Materials made up of a series of harmonically coupled resonators can exhibit a negative index of refraction, they can cause light to bend the “wrong way”. With these materials it is possible to make a flat lens. What is more, it is possible to create a lens that exhibits super-resolution, the ability to resolve features that are smaller than the wavelength of the illuminating light.

Another feature of lenses created from these materials is that they do not have an axis like a conventional curved lens and as a result they can have an unlimited depth of field. This also has significant implications for photo lithography because presently when you expose a silicon wafer, near the center the image is sharp but it becomes increasingly blurry near the edges and so for example a wafer of CPU’s, those nearest the center will be the highest quality, and defects and quality decrease as you get to the edge. With these new lenses it will be possible for all of the wafer to be exposed with correct focus.

I believe we’re just seeing the tip of the iceberg and more exciting developments can be expected.

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