A string sounds perfectly pure until a draft touches it. That's roughly how a superradiant laser works: a beam of atoms, pre-charged with energy, flies through a room made of two mirrors — an optical resonator (a trap where light bounces back and forth). The atoms collectively release their stored light, producing a beam with an extremely stable frequency — good enough for atomic clocks. But the authors of a new study found that this idyll doesn't last forever.

If the lifetime of light in the resonator is made much shorter than the lifetime of the excited atoms, the laser tips into chaos. The beam's intensity stops being steady and starts to dance — flaring up and dying down like a candle flame in the wind. The researchers derived a clear condition for this instability: it arises when photons leave the resonator faster than the atoms manage to 'settle down.' In this regime, the laser resembles a pot of boiling water: heating from below (atoms), cooling from above (light losses)—and the Bénard convection cells, familiar from turbulence physics, appear here too.

But there's good news too: if there are many atoms, the laser enters a regime of regular self-pulsing — rhythmic flashes, like a heartbeat. For practitioners, this offers a double benefit: you can either avoid the dangerous zone and maintain perfect stability for optical clocks, or deliberately drive the laser into chaos and turn it into a laboratory for studying turbulence. Here, unlike in a fluid, every photon is accounted for, and you can see what slips away in a turbulent flow of water. And the string we started with keeps sounding — only now its music can be both gentle and wild, depending on how hard the draft blows.