Graphitic carbon nitride nanosheets as scatterers for random laser action

We demonstrate random laser (RL) emission from rhodamine 610 using graphitic carbon nitride (g-C₃N₄) nanosheets synthesized using a thermal polymerization method as scatterers in a liquid suspension to provide feedback for the RL emission. To characterize RL action and its threshold value, we observed replica symmetry breaking that leads to a transition from a photonic paramagnet to a photonic spin glass for four concentrations of g-C₃N₄. Additionally, we applied a fast Fourier transform to the RL spectra to gain insights into the photon optical path lengths, which aids in evaluating the feedback mechanism. The photonic disorder introduced by the g-C₃N₄ nanosheets creates multiple scattering paths of different natures. An important aspect revealed by our experimental results is the existence of coherent feedback in the system. At the same time, localized optical modes are generated within each nanosheet due to intrinsic structural defects and surface states, providing a coherent feedback mechanism.