Reverse saturable absorption and fluorescence in liquid solutions of mesoionic compounds are reported. Intensity-dependent transmittance and anti-Stokes fluorescence were observed when the samples were excited with radiation at 532 nm. The results are attributed to excited-state absorption, and the process is understood based on quantum-chemistry calculations that allow the energy levels that correspond to the relevant transitions to be located. A phenomenological description of the nonlinear beam propagation inside the samples is presented, and the nonlinear absorption coefficient as well as the saturation intensity is determined.
© 2001 Optical Society of America
(160.4890) Materials : Organic materials
(190.4710) Nonlinear optics : Optical nonlinearities in organic materials
(300.2530) Spectroscopy : Fluorescence, laser-induced
(300.6460) Spectroscopy : Spectroscopy, saturation
Nikifor Rakov, Cid B. de Araújo, Gerd B. Rocha, Alfredo M. Simas, Petrônio A. F. Athayde-Filho, and Joseph Miller, "Reverse Saturable Absorption and Anti-Stokes Fluorescence in Mesoionic Compounds Pumped at 532 nm," Appl. Opt. 40, 1389-1395 (2001)