Dye doped porous silica as an all solid state device for random lasing

The context of this work is the development of solid state materials with optimized microstructures for investigation of the random laser emission. We focused our attention on dye doped silica whose porosity allows controlling the light transport mean free path. Synthesized materials were silica monoliths prepared through sol-gel processing in the presence of a polymer that induces porosity through a spinodal phase separation. This technique allows the preparation of bulk samples with a controlled pore size varying from several microns to less than 100 nm. These samples were doped through impregnation with a naphthalimide fluorescent dye solution. Homogeneous dispersion of the dye was achieved using a silanated derivative leading to its homogeneous deposition as a thin film at the surface of the pores. This gives strongly fluorescent and diffusive materials. Optical properties of the samples were characterized using the 425.84 nm line of a dye laser. FWHM reduction of the sample emission was observed as a function of the pumping power, showing a typical behavior for a random laser in the weakly localized regime. Due to the versatility of the synthesis, the efficiency of the random lasing effect was investigated as a function of the materials microstructure.