TAKE a pinch of zinc oxide powder, add a dash of energy and you’ve got one of
the world’s smallest—and cheapest—lasers.
Physicists have built various types of microlasers, but all rely on ordered
structures, such as shaped microdiscs or a series of uniformly spaced layers of
materials, and require expensive nanofabrication equipment. “Our way is much
simpler and cheaper,” says Hui Cao of Northwestern University in Evanston,
Illinois. Over the past two years she has shown that clumps of disordered powder
can scatter light waves coherently to build up laser emission. Now she has
managed to make a…
