For the first few decades after the invention of the laser in 1960, the record for the shortest laser pulse fell by a factor of two every three years or so. Each development provided new insights into the microworld of atoms, molecules and solids. In 1986, however, this trend essentially stopped when the pulse length reached 6 femtoseconds (6 X 10-15 seconds). For visible light this corresponds to just three oscillations of the electromagnetic field in the laser.
Since the mid-1980s there have been many advances in laser science, but the minimum pulse duration has decreased only slightly. To significantly break the current record - a 4.5 femtosecond pulse from a laser with a wavelength of 800 nanometres - a completely different approach is needed. Physicists at the Foundation for Research and Technology-Hellas (FORTH) on Crete have recently demonstrated one such approach (N Papadogiannis et al. 1999 Phys. Rev. Lett. 83 4289).
In the February issue of Physics World magazine, Paul Corkum from the Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa explains how to make attosecond laser pulses.