The stuff of beams: Building with light

日期:2019-03-02 05:10:02 作者:苏玻 阅读:

By Justin Mullins COLIN BAIN hands me goggles as protection against the blinding power of his infrared laser, then pulls back the heavy blackout curtains that hide his experiment. This is where Bain makes matter. In front of us is a solid metal worktop covered with lenses, prisms and mirrors. Bain’s laser sits at one end, poised to fire along this optical obstacle course, which ends at a microscope that we are peering through. In the field of view is a slide containing a sample of water spiked with the building blocks of Bain’s matter. Through the microscope, they look like fleas in motion, flitting from one location to another. In reality, they are polystyrene beads a few hundred nanometres across being buffeted by water molecules. With a flick of a switch, the laser bathes the beads in an invisible web of infrared light and immediately the beads start collecting in the centre of the slide. First one or two, then perhaps a dozen fall into line. The beads are still jostling, but something much stronger is holding them in place. Other beads cluster around, seemingly reluctant to join the group. But one by one, they take the plunge, somehow forced into the growing array. Eventually the beads form a chessboard array bound together like a crystal. The curious thing about this crystal is that it is not held together by the same forces that bind ordinary crystals. Instead, says Bain, who is a chemist at Durham University, UK, light itself is doing the work,