Peiheng Zhou

An ordinary laser amplifies light into a bright beam. Run the process in reverse, and you get an anti-laser — a device that sucks in light without a trace. But such a machine is finicky: even a slight disorder can ruin the absorption. Physicists have found a way to make the anti-laser invulnerable.

Light can get stuck inside tiny structures, like sound in a perfectly tuned bell: the energy does not escape, even though there are no walls around. Such states are called 'bound states in the continuum'—light is trapped but not confined in a box. Until now, they were produced in ordinary crystals, where left and right directions are indistinguishable.