A Step Toward an Invisibility Cloak

Technology Review has a writeup on the latest advance in the lab towards an invisibility cloak made of metamaterials, described this week in Science. We've been following this technology since the beginning. The breakthrough is software that lets researchers design materials that are both low-loss and wideband. "The cloak that the researchers built works with wavelengths of light ranging from about 1 to 18 gigahertz — a swath as broad as the visible spectrum. No one has yet made a cloaking device that works in the visible spectrum, and those metamaterials that have been fabricated tend to work only with narrow bands of light. But a cloak that made an object invisible to light of only one color would not be of much use. Similarly, a cloaking device can't afford to be lossy: if it lets just a little bit of light reflect off the object it's supposed to cloak, it's no longer effective. The cloak that Smith built is very low loss, successfully rerouting almost all the light that hits it."

Comments

Bad summary

[chebucto]

The cloak that the researchers built works with wavelengths of light ranging from about 1 to 18 gigahertz--a swath as broad as the visible spectrum.

That doesn't sound right... first, the Hertz is a measure of frequency, not wavelength. And the range quoted - 1GHz to 18GHz - seems much wider than frequency range of the visible spectrum, anyway.

... After a little wikipeeing, I find: 'A typical human eye will respond to wavelengths in air from about 380 to 750 nm.[1] The corresponding wavelengths in water and other media are reduced by a factor equal to the refractive index. In terms of frequency, this corresponds to a band in the vicinity of 400-790 terahertz' (http://en.wikipedia.org/wiki/Visible_spectrum)

.. which seems to imply that the invisibility cloak won't work in the visible spectrum, anyway. Can someone who knows what they're talking about shed some light on the issue?

Re:Extraordinary claims require extraordinary proo

[Talgrath]

If it really works the way they say it does, then they can't really show it to you since you wouldn't be able to see it.