Laser-like emission in opal photonic crystals

In our studies of dye-infiltrated opal photonic crystals, we find a stimula ted emission regime, which is characterized by highly efficient, directiona l laser-like emission and a complex finely structured spectrum. This regime can be interpreted as an onset of multimode, mirrorless laser oscillations that occur in the spectral range outside the photonic crystal stop bands. Such a phenomenon may be due to unusual optical feedback induced by multipl e backscattering inside the excited region of the opals. (C) 1999 Elsevier Science B.V. All rights reserved.