Graphene can be used to produce femtosecond pulses of any colour laser light because it can absorb a broad range of wavelengths, researchers have found.
Graphene’s ability to absorb a broad range of wavelengths is because of the structure of its electrons’ energy levels. In non-metal materials, such as silicon, electrons can exist in a low-energy state, attached to atoms, or they can move around when at a higher-energy state. Between these two states is the band gap.
An electron can cross the band gap if the material absorbs light with that particular energy — which means a particular wavelength. In the semiconductor materials used to make transistors in computer chips, electrons jumping over the band gap switch the current from 'off' to 'on'.
First reported in the journal Nature, UK researchers from Imperial College London and the University of Cambridge were involved in the work. Their teams’ results were reported at the Conference on Lasers and Electro-Optics in San Jose, California.