Quantum dots are made of semiconductor material grown as nanometre-sized crystals, around a millionth of a millimetre in diameter. The laser colour they produce can be selectively tuned by varying their size. To build a laser using quantum dots, you need to place them within a structure known as an optical cavity. This structure acts to amplify the light that is produced by the quantum dots to produce the laser.
The researchers suspend these nanocrystal quantum dots in liquid to create ‘inks’ which they then printed onto a glass-like material with nanoscale grooves in it.
When light is shone onto the material, it is bounced around inside the grooves and builds up in intensity, exciting the electrons in the quantum dots to a higher energy level and causing them to give off their own light. The colour of the light depends on the size of the nanoparticle.
“If we printed our lasers on a sheet of paper then every single point on that paper would be its own individual laser. It’s a flat panel laser,” says Dr Jacek Jasieniak, a nanotechnologist with CSIRO, who has been chosen as one of this year’s Fresh Science winners.