Laser-induced white-light emission from graphene ceramics-opening a band gap in graphene

Recent theoretical and experimental studies have indicated the existence of a new stable phase of carbon with mixed sp(2) and sp(3) hybridized bonds-diaphite. Such a two-layered structure with sp(2)/sp(3) bonds may be observed after the photostimulation of highly oriented pyrolytic graphene with femtosecond laser pulses. This hidden multistability of graphene may be used to create a semiconducting phase immersed in the semimetallic continuum, resulting in bandgap opening. We demonstrate that bandgap opening and light emission from graphene is possible using continuous-wave laser beams with wavelengths from the visible (405 nm) to the near-infrared range (975 nm). We demonstrate that without the application of cooling, the effective temperature of the emitting sample remains lower than 900 K, which is far below the value predicted by the theory of black-body radiation. Moreover, light emission from a graphene sample may be observed at temperatures as low as 10 K.