Plasmonic enhancement of random lasing from dye-doped polymer film by bristled Ag/TiO₂ composite nanowires

We report on the enhanced random lasing from the organic gain medium in a planar waveguide, with the assistance of bristled Ag/TiO₂ composite nanowires. Tris(8- hydroxyquinolinato)aluminum (Alq₃) and 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7- tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) are used as donor-acceptor lasing dyes. Comparing to the gain medium with silver nanowires, and the lower lasing threshold is achieved utilizing bristled Ag/TiO₂ nanowires, the threshold is reduced by 3.7 times than that of the neat gain medium. It is attributed to the broader localized surface plasmon resonance spectrum of Ag/TiO₂ nanowires which could sufficiently overlap with both absorption and emission spectra of donor-acceptor lasing dyes, the stronger localized electric field enhancement effect and scattering effect. In addition, the unique plasmonic waveguide effect could also contribute to the enhanced lasing and lead to the lower lasing threshold. This method is expected to be a potential metal-modified technology for improving the lasing performance.