Where’s My Cloak? – He’s Looking Right Through Me

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.

  1. http://www.bbc.co.uk/news/science-environment-20265623
  2. http://www.nature.com/nmat/journal/vaop/ncurrent/abs/nmat3476.html

Leave a Reply