Investigation On The Optical Nonlinear Of The Broadband Excited States Based On Dimethylamino-carbaldehyde Derivatives

The development of optical electronic devices such as optical limiting,optical bistable and optical switches are greatly promoted by the study of nonlinear optical materials.The researchers were interested in the organic materials with D-?-A structure due to its large optical nonlinear and easy to modify.Two dimethylamino-carbaldehyde derivatives with different ?-bridge lengths were prepared.Due to the difference ?-bridge lengths,the two compounds exhibit different charge transfer capacity and the change modulates the population of locally excite states.The transient optical properties and photophysical mechanism were investigated by transient absorption spectroscopy and z-scan measurements.Transient absorption spectroscopy was investigated to study the broadband transient absorption spectra response of the two compounds with different population of locally excite states.After photoexcitation,the two compounds exhibited the opposite the transient absorption spectra.Compounds with low population of locally excite states exhibited a wide excited state absorption from 450 nm to 1000 nm.Meanwhile excited states lifetime changed dramatically,it tuned from 2 ns into 100 ps.The two-photon absorption of materials were studied by femtosecond Z-scan technology.Both of the two compounds exhibited reverse saturation absorption and positive refraction.Compounds with low population of locally excite states exhibited larger nonlinear optical properties,a figure of merit value which is more than 2 at the wavelength of 1000 nm is obtained.The results show that modulating the population of the locally excite states of this type of materials can be considered as a promising candidate for obtaining optical switching and solar cell materials.