Random Lasers From Dye-Doped Chiral Photonic Crystal Films

We have obtained a dye-doped chiral photonic crystal (PC) film with reflection band gap much wider than its original band gap without dye dopants by using multiple-step fabrication processes. Moreover, the dye-doped chiral PC films using our multiple-step fabrication processes exhibit many oscillations within the broadened reflection band gap. The abrupt change of the optical density of state (DOS) around the oscillations provides the possibility of generating laser emission when the dye-doped chiral PC film is pumped by a pulsed laser with wavelength in the absorption region of the laser dye. Based on this property, we demonstrated random lasers which exhibit different multiple-mode laser wavelength at different spatial positions. Different from the random lasers induced by the scattering mechanism, the random lasers from the dye-doped cholesteric polymer film exhibit Gaussian-like beam shape and specific propagation orientation which is normal to the cholesteric planar surface. It is foreseeable that a high efficiency and high power broadband laser can be generated using cholesteric polymer films