Random Lasing in Self-Assembled Dye-Doped Latex Nanoparticles: Packing Density Effects

Efficient random lasing (RL) from self-assembled dye-doped latex nanoparticles (d = 50-380 nm) presenting size polydispersity is reported. This new system exhibits a very good chemical compatibility between dye (Rhodamine 6G) and polymer as well as a high refractive index contrast between nanoparticle and surroundings (air), in such a way that its emission properties surpass the ones previously reported in similar systems. Furthermore, this system allows analyzing in detail the effects of the nanoparticle size polydispersity and the packing density on the RL emission properties. It is shown that size polydispersity gives rise to non-uniformities in the filling fraction along the sample that lead to fluctuations on the scattering length across the sample and thus to a variation on the emission properties. Finally, it is observed that the increase of the filling fraction, enabled by the use of binary mixtures of nanoparticles with different sizes, results in remarkable improvements in the RL emission properties.