Lasing actions from a liquid crystalline polymer blend

Abstract

We report lasing actions from fluorene-based copolymer blends with liquid crystallinity in waveguide geometry. Fluorene-based light emitting polymers, poly[2,7-bis( p-stiryl)9,9′-di- n-hexylfluorene sebacate] (PBSDHFS) and poly(9,9′-di- n-hexyl fluorenediylvinylene- alt-1,4-phenylenevinylene) (PDHFPPV), and a laser dye, 4(dicyanomethylene)-2-methyl-6-( p-dimethylaminostyryl)-4H-pyran (DCM) were used in this study. We employed Förster type energy transfer from a liquid crystalline donor to a non-crystalline acceptor to tune the color and obtain low threshold for gain narrowing. We obtained a low-threshold energy (∼20 nJ/cm 2 per pulse) for gain narrowing of PBSDHFS/PDHFPPV (98:2, by wt.) blend film. PBSDHFS/PDHFPPV/DCM (98:2:2, by wt.) blend film possesses a threshold energy of ∼14 μJ/cm 2 per pulse, while the PDHFPPV/DCM blend film did not show gain narrowing even at a pump energy as high as 12 mJ/cm 2 per pulse. Förster excitation energy transfer played the most important role in improving the performance of lasing actions and tuning the output colours.