Bringing together the fields of nanotechnology, novel growth techniques and lasers, a group from Arizona State University has achieved for the first time, white lasers. When developed as technology, such lasers could be more effective than LEDs for lighting purposes and also in computer screens and televisions.
In a paper published recently in Nature Nanotechnology, Cun-Zheng Ning and his doctoral students have revealed how they have developed this technology of a white laser.
In their work, Prof. Ning and others have created a novel nanosheet which measures one-fifth of the thickness of a human hair across and one thousandth of the thickness of a human hair in height. This nanosheet has three parallel sections each capable of lasing in any colour in the visible range. Then these are made to lase in three different colours and the combined field looks white to the eye.
The greatest challenge was to grow the nanosheet. The difficulty arose because in order to lase in a particular colour, or wavelength, the semiconductor crystal has to have a definite value of spacing between its atoms, known as the lattice constant, and a value of the energy bandgap. So to grow such a nanosheet with three different values of the lattice constant was a real challenge to the researchers.
White laser light has been produced earlier using four separate coloured lasers combined together, but this technology could not be exploited to provide lighting. For that a more compact single source of all wavelengths of light was required. That is where this discovery comes in.
