One Material, Many Nanolaser Colors
Since they were first made, lasers have been growing in use and capability. They have also been growing smaller, from large gas-based devices that fill an optical table down to semiconductor diodes inside of optical drives and laser pointers. Making different colored lasers and making them smaller is very difficult though because only certain materials will produce a certain light. Now researchers at Brown University have discovered a material that can be grown to produce any visible color.
The material is used to create quantum dots, designer nanocrystals, of different sizes. The size of the dots determines what color light they produce, with 4.2 nm creating red light, 3.2 nm corresponding to green light, and 2.5 nm produces blue light. Varying the production time of the nanocrystals controls the size the dots grow to.
The solution the quantum dots are made in is similar in viscosity to nail polish, and the researchers spread it onto a piece of glass. The solution evaporates to leave the dots in a highly ordered pattern on the glass, which is then sandwiched between two mirrors. This creates a Vertical-Cavity Surface-Emitting Laser (VCSEL) that uses as much as 1000 times less power than similar lasers.
The researchers believe this can be used to make advanced displays with relatively little cost. This is because it is the same process to make the different color pixels. Also a multitude of shapes can be made into displays with this technology, because the quantum dots just need to be painted onto the surface and then the mirrors placed around them.