Laser Action from Two-Dimensional Distributed Feedback in Photonic Crystals

We report the characteristics of two-dimensional distributed feedback lasers with organic thin-film gain media. The gain medium consists of a 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PDB) host doped with Coumarin 490 and DCM and is deposited on lithographically patterned Si/SiO sub 2 structures. Bragg reflections caused by the grating diminishes the group velocity of photons along some directions of crystallographic symmetry to zero, and the resulting feedback gives rise to laser oscillations. Dispersion relations for photons were calculated analytically and are used to interpret the laser emission spectra.