American Institute of Physics, Applied Physics Letters, 24(94), p. 243304
DOI: 10.1063/1.3152782
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A blue-emitting distributed feedback laser based on a star-shaped oligofluorene truxene molecule is presented. The gain, loss, refractive index, and (lack of) anisotropy are measured by amplified spontaneous emission and variable-angle ellipsometry. The waveguide losses are very low for an organic semiconductor gain medium, particularly for a neat film. The results suggest that truxenes are promising for reducing loss, a key parameter in the operation of organic semiconductor lasers. Distributed feedback lasers fabricated from solution by spin-coating show a low lasing threshold of 270 W / cm 2 and broad tunability across 25 nm in the blue part of the spectrum.