A laser flash lasting 50 femtoseconds is like a shot that lasts one billionth of a second. In that time, light travels only 15 micrometers — less than the thickness of a human hair. But if you send such a flash through an amplifier, it starts to stretch like a rubber band and loses its sharpness.

Physicists from the group of Jascha Sohl-Dickstein (though he is known for other work) found a way around this. They noticed that if you choose the right input pulse duration, a special regime emerges in the fiber—'partial parabolic amplification.' In this regime, the pulse compresses itself rather than stretching, and the output is a flash lasting 50 femtoseconds with a peak power of 30 megawatts. For comparison, a typical light bulb is 60 watts: this is a million times more.

Previously, such pulses could only be obtained with bulky solid-state lasers, but now it's possible in a compact fiber amplifier. The authors are confident that the power can be increased another tenfold, to 200 megawatts, using fibers with a wider core. This would pave the way for ultra-precise cutting of materials and microscopy that doesn't damage living cells.