AAWSAP DIRD, Invisibility Cloaking Theory and Experiments, March 2010

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Cloaking
Cloaking4• 5 is a universal strategy for invisibility that works for objects of arbitrary
compositions and shapes within a given size. In cloaking, the hidden object is enclosed
by the cloaking device, a transparent shell that guides light around the object as if the
light would propagate through empty space. In this way, both the interior of the
cloaking device is hidden and the act of hiding is concealed.
Figure 6. Cloaking Shell6
How does one find the right design for such a cloaking device? As the Invisible Man
symbolizes transparency as a strategy for invisibility, inspiration for cloaking may come
from the Invisible Woman, a cartoon figure from the Fantastic Four. The Invisible
Woman is said to create a mysterious force field around her that bends space. Light
follows the curved space such that it smoothly flows around the Invisible Woman, like
water in a stream flowing around an obstacle. The key idea here is the concept of
curved space used for invisibility. The idea that turns the Invisible Woman with her
fabled force field from a fictitious character into something close to reality is the insight
that no force field is needed, that light-refracting materials like glass or water appear as
curved spaces by themselves.
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