Extremely Low Threshold in a Pyrene-Doped Distributed Feedback Cholesteric Liquid Crystal Laser

The authors have studied low threshold lasing in dye-doped cholesteric liquid crystals (CLCs). We designed and synthesized a dye, 1,3,6,8-tetrakis(6'-hexyloxy-2-naphthyl)pyrene, which has high quantum yield Phi = 0.85. Since the transition dipole moment is perpendicular to the local director of a host CLC, laser oscillation occurs at the higher energy edge of the stop band of CLC contrary to that in conventional dyes aligning parallel to the director. We evaluated lasing characteristics and found that the pyrene-doped CLC gives laser threshold of 43 nJ/pulse, which is about one order of magnitude lower than that of conventional laser dyes. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/APEX.2.102501