A continuously tunable low-threshold organic semiconductor distributed feedback laser fabricated by rotating shadow mask evaporation

We report on an organic semiconductor distributed feedback laser with a continuously tunable wavelength from 621 to 657 nm on a single sample with thresholds as low as 38 mu J/cm(2). Using laser interference lithography and reactive ion etching, we textured a glass substrate with a one-dimensional second-order Bragg surface grating. Optical confinement and gain is provided by a wedge-shaped layer of the organic semiconductor tris(8-hydroxyquinoline) aluminum doped with the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyril)-4H-pyrane, which is fabricated by a rotating shadow mask evaporation. This allows for a simple, broadband continuous tuning of the laser emission wavelength.