Optical spectroscopy with organic semiconductor lasers

We report on the fabrication of large-scale surface gratings by laser interference lithography and reactive ion etching on which we evaporated a thin film of the organic semiconductor tris(8-hydroxyquinoline) aluminum doped with the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyril)-4H-pyrane. We created a thickness gradient by using a rotating shadow mask evaporation technique. This allowed us to continuously tune the emission wavelength from 606 nm to 661 nm on a single substrate. After encapsulation, we demonstrated the usefulness of such low-cost and tunable organic semiconductor lasers by conducting simple fluorescence excitation and transmission spectroscopy measurements using a minimal amount of additional optical components.