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June 5, 2017

Pre-Kymeta Series Part 1: Metamaterials Discovered

Every great discovery starts with curious people asking questions and looking for answers. Kymeta’s technology is based upon scientific discoveries….

Every great discovery starts with curious people asking questions and looking for answers. Kymeta’s technology is based upon scientific discoveries. Surprisingly, the physics concepts Kymeta’s metamaterials-based, holographic, beamforming antenna technology relate to work with origins that date back to 1967 and a Russian physicist named Victor Veselago. Veselago’s theories laid dormant for forty years, until Duke physics professor, David R. Smith PhD—then at the University of California, San Diego—rediscovered them in the context of his work on metamaterials.

Veselago conjectured the possibility of a negative refractive index in 1967. Negative index material causes light to refract or bend differently than in common materials such as a glass lens. The unique properties of materials such as negative index are at the core of Kymeta’s metamaterials-based antenna technology.

Sometimes the most significant discoveries come to light in the most surprising and convoluted ways. First, Dr. Smith’s original research article was rejected by the prestigious journal Physical Review Letters as being unimportant. Because of the rejection, Dr. Smith performed a literature search and found the seemingly forgotten 1967 research paper on negative index materials written by Veselago.

The hypothesis Dr. Smith originally set out to prove had to do with proving that an array of metal rings could have magnetic properties. Inherently magnetic materials are characterized by a parameter called the magnetic permeability. Electrical conductors typically have little to no magnetic response; however, when fashioned into little loops called split-ring resonators, the composite structure can have an artificial magnetic response and a medium of such resonators can have a magnetic permeability. In 1999, theoretical physicist, Sir John Pendry, predicted that not only would the split rings have a permeability, but also that there would be a frequency band over which the permeability would be negative. Proving the split rings would have a region where the magnetic response was reversed would provide evidence that the split ring medium had the properties that Sir John predicted. While the concept of artificial magnetism was not entirely new, the concept generated much greater interest because of the potential of creating artificial magnetism across the entire electromagnetic spectrum, even at frequencies where magnetic response is entirely absent (such as at visible wavelengths).

The experiment the team performed involved making the material, and sending microwaves into it. If the material reflected the microwaves strongly, it was opaque. Dr. Smith decided to combine the split rings with an array of wires. Dr. Smith knew the wires had a negative permittivity—also a prediction that had been made by Sir John. A material with both negative permeability and permittivity becomes transparent, and this is what Dr. Smith aimed to show.

The experiment was successful, and ultimately led Smith to realize he had not only demonstrated a material with negative permeability, but also Veselago’s negative index material. The experiment proved that artificial materials (metamaterials) like little split rings and wires could be used to create materials not found in nature.

After the experiment, the entire world got excited about negative index materials and metamaterials. However, Dr. Smith wanted a stronger set of numerical tools to prove the case, as well as to provide a means for designing future metamaterials quickly.

In 2000, Dr. Smith’s first research paper on the topic was finally published by Physical Review Letters. The publication led to the launch of the field of metamaterials, and sparked the soon to be scientific revolution that would have implications around the world. Today, metamaterial technology is being developed for a wide range of products, from satellite communications, to camera lenses and wireless chargers. Plus, it can be used to create invisibility cloaks; which we will discuss in Part 2.

Nathan Kundtz and David Smith during KyTrek 1 negative index and metamaterials

Nathan Kundtz and David Smith during KyTrek 1