“the molecule in the beam doesn’t know what hit it. it just
disappears in a flash of light.” — Henry CHApm An
in Scotland who was not involved in light looks exactly like it bounced off a
either study. His 2006 paper in Science flat mirror. The metal wedge vanishes.
helped to launch invisibility research. “It’s not a Harry Potter cloak,” says
Because metamaterials require intri- Shuang Zhang, a physicist at the Uni-
cate sculpting by lasers or other tools, versity of Birmingham in England and
scientists can make them only so big; one of the coauthors on the Nature
Harry Potter would need to be more than Communications paper.
paper-thin to hide under early carpet For one thing, the cloak works only
cloaks. The calcite shields, on the other using one particular form of polarized
hand, can disappear objects 1 to 2 milli- A piece of pink paper vanishes under a light. And it cloaks only when Zhang
meterstall. Metamaterialdesigns“liber- new invisibility cloak, made from calcite, aims the light source dead-on at the
ated the imagination,” Leonhardt says. that can hide macroscopic objects. crystals, not at an oblique angle. But,
“Now, it’s time to come back to reality.” he says, improving the method to allow
But with such tricky optical sleight cloak, they have changed directions four other angles isn’t too big of a leap. Zhang
of hand, reality may seem like a misno- times but look like they changed direc- imagines similar technology one day
mer. With the right type of light, calcite tion only once, says George Barbastathis concealing submarines on the seafloor.
prisms can bend laser beams in different of MIT, coauthor of the Physical Review Leonhardt says the future of optical
directions based on the crystal’s orienta- Letters paper. His team used the cloak legerdemain lies not in hiding things,
tion. Light enters the cloak — a triangle to hide a small metal wedge. “Putting but in revealing them. He uses the same
or trapezoid made of two prisms glued calcite on top of the wedge, the light geometric tools to design better micro-together — and bounces off the bent mir- goes back into the same direction that it scopes. “ We use similar ideas not to
ror at the bottom into the second prism, would have with a flat mirror,” he says. make things disappear but to make them
then out. By the time the beams leave the But it’s not just the same direction — the visible,” he says. s
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