A LASER small enough to fit on a pinhead could be used to analyse chemicals
in a lab-on-a-chip. The 鈥渘anolaser鈥� emits ultraviolet light so could also be
used for optical computing and data storage devices.
To make the laser, Peidong Yang at the University of California, Berkeley,
and colleagues at the Lawrence Berkeley National Laboratory grew zinc oxide
crystals on a sapphire sheet, creating a forest of zinc oxide nanowires. Each
wire is about 10 micrometres tall and 100 nanometres in diameter. Pumping light
into the device causes excitons鈥攑airs of electrons and holes鈥攖o
bounce back and forth along each wire (Science, vol 292, p 1897). When the
excitons collide, they produce a stream of ultraviolet photons. 鈥淚f you want to
analyse chemicals on a chip, you need a miniature UV source,鈥� says Wang.