Ultrafast spectroscopy, superluminescence and theoretical modeling of a two-photon absorbing fluorene derivative.

A comprehensive study of photophysical and photochemical properties of an unsymmetrical fluorene derivative is presented, including linear absorption, fluorescence excitation anisotropy, photochemical stability, steady-state fluorescence, and fluorescence lifetimes in organic solvents of different polarities. Nonlinear optical properties were investigated using Z-scan measurements of degenerate two-photon absorption and femtosecond pump-probe spectroscopy. The strongly fluorescent compound exhibited good photostability, positioning it for use in a number of applications. A dramatic increase in fluorescence intensity along with spectral narrowing was observed under femtosecond pumping, demonstrating amplified spontaneous emission. An extensive set of experimental data is rationalized based on essential state models.