Single light wave flashes out from fibre laser

The Konstanz researchers started with pulses from a single fibre laser and split them between two sets of fibres that contained atoms of the rare earth metal erbium to amplify the light waves. Each fibre then had a second stage that altered the light’s wavelength, one stretching it by about 40 per cent, the other shrinking it by a similar amount. The two fibres then converged again, causing the two light beams to interfere with one another in a way that cancelled out most of the waves to leave just a single wave cycle lasting just 4.3 femtoseconds.