Influence of the orientation of liquid crystalline poly(9,9-dioctylfluorene) on its lasing properties in a planar microcavity

We present a study of optically pumped laser emission from a microcavity containing an oriented layer of the liquid crystalline conjugated polymer poly(9,9-dioctylfluorene). The birefringence of the oriented polymer results in the definition of two cavity modes with electric vectors polarized perpendicular and parallel to the alignment direction. At high excitation density, the emission intensity from the cavity mode polarized parallel to the orientation direction increases rapidly compared to the orthogonal polarized mode and its linewidth narrows from 8 to 2 nm. We identify the parallel-polarized emission as laser action with a threshold excitation density of 7.8x10(19) cm(-3). (C) 2002 American Institute of Physics.