This paper describes how the experimental dependences of the energy parameters and the random lasing (RL) spectrum in the diffusion regime depend on the pump intensity, the concentration and refractive index of the scattering particles, the thickness of the sample, and the reflection at its boundaries. An algorithm is proposed for calculating these RL characteristics in the diffusion regime of light propagation by the Monte Carlo method, and calculated dependences of these RL characteristics on the parameters of the medium are obtained that agree with the experiment. It is shown that, because of reflection from the sample boundaries, there is an optimum thickness of the sample for which the RL energy is maximal, and its spectrum is narrowest. The dynamics of the number of excited dye molecules and the photons that they emit in a sample are calculated, along with the RL spectrum as a function of time. The existence of three stages in the formation of RL is established: accumulation of excited molecules, formation of multimode radiation, and relaxation with persistent lasing in high-Q modes. It is shown that the dominant role in the formation of RL radiation is played by the highest-Q modes.
© 2012 OSAPDF Article