Large Enhancement of Nonlinear Optical Absorption and Refraction in Planar Chalcone Structure with Terminal Substitution

The ultrafast nonlinear optical (NLO) properties of novel planar pi-conjugated chalcone derivatives, (E)-3-(4-nitrophenyl)-1-(3-bromo-4-fluorophenyl) prop-2-en-1-one (1503) and (E)-3-(4-nitrophenyl)-1-(phenothiazin-2-yl) prop-2-en-1-one (1526) are investigated and compared. The effect of intramolecular charge transfer on NLO absorption and refraction is discussed without changing the planar structural properties of the chalcone molecules. Transient absorption experiments are used to observe the evolution of 1526 from local excited (LE) state to the intramolecular charge transfer (ICT) state. In the Z-scan experiments, 1526 exhibits respectively different nonlinear absorption (NLA) mechanisms (reverse saturable absorption and two-photon induced excited state absorption) at 532 nm (4 ns, 22ps, 190 fs) and 700-900 nm, 190 fs. The NLA and nonlinear refraction (NLR) phenomena of 1526 are observed and discussed in the POPP experiments. The experimental results indicate that the chalcone derivative can become the potential materials for laser protection.