Active laser medium for near-infrared spectral range based on electron-unsymmetrical polymethine dye and silver nanoparticles

An effect of silver nanoparticles (Ag NPs) on spectral luminescent and lasing properties of an electron-unsymmetrical polymethine dye in ethanol solution has been studied. Fluorescence of the dye is characterized by a large Stokes shift of 3007 cm −1 and a quantum yield Φ f of 0.08. An increase in the absorption cross section and in the fluorescence quantum yield of the dye molecules is observed in the presence of Ag NPs. The dye fluorescence lifetime of 1.11 ns remains unchanged after the addition of Ag NPs to the solution. Stimulated emission with spectrally pronounced two-mode oscillations has been obtained for the dye in the region of its fluorescence band maximum. A stimulated emission threshold is achieved on the average at 3.35 MW/cm 2 . The presence of Ag NPs leads to the enhanced intensity and 28% lowered threshold of dye stimulated emission. The data obtained can be used to develop new near-infrared lasing media.