CHIH-CHIEN CHU2026-10-162026-10-162014-12-01Pure ID: 15439358Pure UUID: 9e1baec5-35fe-4b5a-bdba-9c9433910eb710.1002/asia.201402896https://www.scopus.com/pages/publications/84915751139https://scholars.csmu.edu.tw/handle/123456789/27288Azo-containing materials have been proven to possess second-order nonlinear optical (NLO) properties, but their third-order NLO properties, which involves twophoton absorption (2PA), has rarely been reported. In this study, we demonstrate a significant 2PA behavior of the novel azo chromophore incorporated with bilateral diphenylaminofluorenes (DPAFs) as a π framework. The electrondonating DPAF moieties cause a redshifted π-π∗ absorption band centered at 470 nm, thus allowing efficient blue-lightinduced trans-to-cis photoisomerization with a rate constant of 2.04×10-1 min-1 at the photostationary state (PSS). The open-aperture Z-scan technique that adopted a femtosecond (fs) pulse laser as excitation source shows an appreciably higher 2PA cross-section for the fluorene-derived azo chromophore than that for common azobenzene dyes at near-infrared wavelength (λex=800 nm). Furthermore, the fs 2PA response is quite uniform regardless of the molecular geometry. On the basis of the computational modeling, the intramolecular charge-transfer (ICT) process from peripheral diphenylamines to the central azo group through a fluorene p bridge is crucial to this remarkable 2PA behavior.7enjournal article