Two new multi-branched model fluorophores based on tri-substituted olefinic skeletons had been synthesized and their degenerate two-photon absorption properties were characterized by ultra-short laser pulses in the femtosecond regime. The experimental results show that the studied chromophore structures exhibit relatively strong and wide-dispersed two-photon activities in the near infra-red (NIR) regime. It is demonstrated that molecular structures with expanded pi-frameworks derived from multi-substituted olefin moieties would possess large molecular nonlinear absorptivities within the studied spectral region. Two-photon absorption based optical power limiting behaviors in the femtosecond time domain of these model compounds were also explored and the results indicate that such a structural motif could be a useful molecular design approach towards strong two-photon absorbing material systems for quick-responsive and broadband optical-suppressing related applications, especially when against ultra-short laser pulses.
