A continuously tunable organic DFB laser

In this work, a Bragg grating with continuously tuned period Λ, from 380 to 420 nm, was fabricated. The exposure was done by electron-beam lithography and the pattern of the gratings was transferred by a dry etching technique into the SiOx layer of a thermal oxidised silicon wafer. Tris (8-hydroxy quinoline) aluminum (Alq3) doped with the laser dye 4-(dicyanomethylene)-2-methyl-6(julolidin-4-yl-vinyl)-4H-pyran (DCM2) was used as the organic active layer. Continuous wavelength selection was simply realized by addressing the different grating-period areas. A second-order DFB laser with varying wavelength (608.9-646.5 nm) was achieved with the radiation direction perpendicular to the sample surface. The laser threshold and output characteristics were investigated for different laser wavelengths. The FWHM of the laser was between 0.19 and 0.48 nm. A minimum threshold for laser activity occurred for the lasing wavelength between 628 and 633 nm, giving the spectral position of the gain maximum.