Two-photon absorption and lasing properties of new fluorene derivatives

Linear photophysical properties, two-photon absorption (2PA), and lasing effects of new fluorene derivatives, 2,7-bis(4-(phenylthio)styryl)-9,9-didecyl- 9H-fluorene (1) and 2,7-bis(4-(phenylsulfonyl)styryl)-9,9-didecyl-9H-fluorene (2), have been investigated. The relatively strong solvatochromic behavior of symmetrical compounds 1 and 2 can be explained by the phenomenon of symmetry breaking in the electronic distribution of the first excited state. The 2PA spectra of 1 and 2 were obtained over a broad spectral range (480-880 nm) by two-photon-induced fluorescence and open aperture Z-scan methods, in which excited state absorption and stimulated emission processes were considered in the fitting procedure. Maximum values of 2PA cross-sections ∼1300-1900 GM were obtained for 1 and 2 in the two-photon-allowed absorption bands at ∼660 nm. Efficient lasing of 1 and 2 was demonstrated in a nondispersive flat resonator with picosecond transverse pumping at 355 nm. Lasing efficiencies were ∼25-30% in this resonator, and independent of solvent.