Random lasing in low molecular weight organic thin films

We demonstrate that coherent random lasing can occur in solid-state dispersions of laser dyes 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran and 4-dicyanomethylene-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran within a tris(8-hydroxy-quinolinato)aluminum matrix without the need for infiltrated scatterers. Random lasing thresholds as low as 90 μJ/cm² are observed in 250 nm-thick films with 2-2.5% dye concentration. We find that the lasing threshold exhibits a power law decay with sample area, providing a simple test for the occurrence of random lasing. We discuss the implications of this result in the context of previous reports of lasing in these materials where feedback was provided by conventional optical resonators.