Where’s my cloak is a cry
that we’re getting closer to hearing when someone wants to be invisible and
move silently away unseen. We’re not quite there yet as our eyes work at the
wrong wavelength. I guess we can blame the sun for that.
If its peak output that we
felt down here was in the microwave region, then we might all be speaking like
Cleopatra in Shakespeare’s rendition – “hand me my robe…” and we would
disappear. The possibility is come close now as Landy and Smith from Duke U
have built a microwave cloak for a copper cylinder which is about 3 inches in
diameter and half an inch high (1, 2). It vanishes completely.
The object is considerably
larger that the wavelength of the radiation and the back scattering from it
would make it easily detected – imaged by the right optics. Up until now,
cloaking devices have hidden the object, but scattering still occurs and the
cloaked region isn’t apparently transparent but foggy.
With Landy and Smith’s new
clothes for the cylinder, the radiation is guided by corrugations around the
object, but the key here is that the cloak is lozenge or diamond shape and the
corners are the big thing. The corners are carefully designed so
that all the radiation is funneled past to illuminate objects behind the
cylinder.
With no loss going and with
none of the backscattered radiation lost, there I no difference between having
the cloaked object there or with it and its cloak having scurried off
somewhere.
Currently, it only works when
the lozenge is aligned with the radiation beam so it’s not ready for radar avoidance
by stealth aircraft just yet and until we can get our fabrication techniques
down a few orders of magnitude, our good friend Harry Potter won’t be able to
use it with visible light.
- http://www.bbc.co.uk/news/science-environment-20265623
- http://www.nature.com/nmat/journal/vaop/ncurrent/abs/nmat3476.html
