Amplified spontaneous emission and efficient tunable laser emission from a substituted thiophene-based oligomer

Abstract

We investigated gain and lasing in spin-coated films of a soluble substituted oligothiophene. With increasing excitation power, the photoluminescence spectra show a clear line narrowing due to amplified spontaneous emission. We measure a low threshold (20 μJ cm⁻²) for line narrowing and a large gain cross section ${\text{(6×10}}^{\text{−16}}\hspace{0.17em}{\mathrm{cm}}^2\mathrm{),}$ indicating that this molecule is a promising active material for organic solid-state lasers. As a demonstrator, we realize a transverse electromagnetic $({\mathrm{TEM}}_{00})$ single-mode laser with tunable emission from the yellow to the red (a range of 37 nm), with a pump threshold as low as 18 μJ cm⁻² and efficiency of 1.9%. These results are among the best so far reported for organic lasers.