The nonlinear transmission and the excited-state absorption spectra of three fluorene derivatives exhibiting large two-photon absorptivity were measured by the third harmonic of a picosecond Nd:YAG laser. We analyzed their capability for exhibiting stimulated emission in polar solvents and found that asymmetrical fluorene compounds with a diphenylamino substituent exhibited large Stokes shifts (~8000 cm<sup>−1</sup>), high quantum yields (~0.9 – 1.0), and no optical gain over their entire fluorescence spectral region. In contrast, a symmetrical fluorene derivative with vinylphenylbenzothiazole substituents in positions 2 and 7 underwent lasing under one-photon excitation by use of picosecond pulsed irradiation.
© 2004 Optical Society of America
(140.3380) Lasers and laser optics : Laser materials
(140.4480) Lasers and laser optics : Optical amplifiers
(160.3380) Materials : Laser materials
(160.4890) Materials : Organic materials
(190.4710) Nonlinear optics : Optical nonlinearities in organic materials
Kevin D. Belfield, Mykhailo V. Bondar, Florencio E. Hernandez, Alma R. Morales, Olga V. Przhonska, and Katherine J. Schafer, "Nonlinear Transmission and Excited-State Absorption in Fluorene Derivatives," Appl. Opt. 43, 6339-6343 (2004)