The remarkable enhancement of two-photon absorption in pyrene based chalcone derivatives

Two new isomeric pyrene based chalcone derivatives (E)-3-(3,4-dimethoxy-5-(methoxy-methyl)phenyl)-1-(pyren-1-yl)prop-2-en-1-one (1) and (E)-1-(3,4-dimethoxy-5-(methoxy-methyl)phenyl)-3-(pyren-1-yl)prop-2-en-1-one (2) were designed and synthesized for ultrafast broadband nonlinear optics. Z-scan and transient transmission measurements were performed to investigate the differences of regioisomer on nonlinear optics. Both derivatives display reverse saturable absorption as a result of two-photon absorption (TPA). It was found that both π-electron delocalization and intramolecular charge transfer contribute to the TPA and thus influence the nonlinear properties. What's more, remarkable enhancement of TPA cross-section (2400 GM) is observed in 2 as a result of intermediate state resonance enhancement (ISRE). All the studies suggest that these derivatives possess the potential for optical data storage and optical limiting. Moreover, our study further proved the superiority of ISRE on enhancing the TPA of nonlinear materials.