Random lasing in dye-doped polymer random media with a bubble structure

We experimentally investigate random laser (RL) emission from dye-doped polymer random media with inhomogeneously distributed scatterers. A random structure, which we call a bubble structure (BS), is realized by using nonscattering spacer particles randomly distributed in a gain medium. The experimental results show that the bubble-structured RL that incorporates an appropriate amount of spacer particles exhibits a higher spectral peak and a larger slope efficiency than conventional RLs. The highest peak intensity is observed when the size variation of spacer particles is maximized. Furthermore, an analysis of laser modes reveals that an increase in the spectral peak intensity can be partly attributed to the mode selection properties of the BS