Subhendu Kahaly

An ordinary camera flash lasts a thousandth of a second. The new setup at the ELI ALPS laboratory in Hungary produces flashes a billion times shorter. Each flash consists of a few hundred oscillations of the light wave, packed into a time interval in which light travels a distance smaller than the thickness of a human hair.

A gas target is like a funnel: the steeper its walls, the stronger the flow. But in this funnel, it is not water that flows, but ultraviolet light, born when a powerful laser pulse passes through a cloud of argon. The efficiency of this conversion is usually minuscule, about 0.001%: out of a thousand laser photons, only one turns into useful ultraviolet.