Lasing threshold of one- and two-photon-pumped dye-doped silica powder

The random laser features around threshold in a ground powder of a silica gel containing Rhodamine 6G-doped silica nanoparticles under one- and two-photon excitation are analyzed. The lasing threshold following two-photon pumping is fifty times higher than after one-photon excitation. Theoretical calculations by using a light diffusive propagation model are in agreement with the experimental results.