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.This work was supported by the Spanish Government MEC (FIS2011-27968 and TEC 2012-37983-C03-01), Basque Country Government (IT-659-13 and IT-664-13), and by the University of the Basque Country (UPV/EHU) through program UFI 11/16. S. G.-R acknowledges the financial support from Research Association MPC for a postdoctoral appointment. TPeer Reviewe