Mirrorless lasing from nematic liquid crystals in the plane waveguide geometry without refractive index or gain modulation

Lasing from dye doped liquid crystals was observed in the nematic and isotropic phases in the plane waveguide geometry without mirrors and special modulation of the gain or refraction index by a holographic or other technique. The light was generated in a liquid crystal layer confined by two glasses with semitransparent electrodes, which formed an optical waveguide. A strong light amplification occurred along the length of a narrow stripe produced by the pump beam with the necessary feedback provided by the walls of the waveguide in the direction perpendicular to the stripe. The conditions for lasing were fulfilled for the lowest group velocity waveguide modes bouncing at the angles very close to the total reflection angle at the waveguide-glass interface. These modes leaked into the glasses were guided therein at very grazing angles and left the cell from its edges.