Researchers have created microscopic beads that produce long-lasting laser beams, even when the beads are immersed in liquid.
The development of micrometre-scale lasers that emit a continuous beam has proved challenging. To design a continuous mini-laser, James Schuck at Lawrence Berkeley National Laboratory in Berkeley, California, and his colleagues coated polymer beads with ceramic nanoparticles. When the researchers illuminated the beads’ interiors with low-energy light, each five-micrometre sphere reflected the light along its internal surface to create a laser beam, while the nanoparticles boosted the light to higher energies.
The beam excited neighbouring atoms in the nanocoating, setting off an energy cascade. This allowed the lasers to fire continuously for more than five hours.
The lasers functioned even when the beads were immersed in blood serum, showing that such lasers could be used as biological sensors, the authors write.