Invisibility cloaks: Will we ever really have them?
By Jason Palmer Science and technology reporter, BBC News
12 November 2012
You've seen the films, you've read the popular science stories. It's time to ask: when will you have your invisibility cloak?
Hold your horses. It's looking like a great many things inspired by cloaking science will come to pass before then.
Behind most cloaking ideas is the use of metamaterials - materials whose properties are purposefully designed, defined not by chemistry but by the materials' size, shape and structure.
They are already starting to crop up in consumer technology, and could find widespread use in applications ranging from computers to concert halls.
It is a simple idea whose scientific foundations are dizzyingly complex.
At its simplest, explains John Pendry of Imperial College London, "you just want to grab hold of the light coming from an object, guide light around the hidden thing, and then return it to the path it was going on originally - and that's easier said than done."
Another alternative is to find out what a given object will do to incident light beams and create a cloak that does the exact opposite - that's the aim of what are known as plasmonic metamaterials.
Luckily, there are many ways to pull off the invisibility trick. The metamaterials approach seems to be the most promising, but a number of what might be called optical tricks have also cropped up.
... much more at link
http://www.bbc.co.uk/news/science-environment-19661503
