Fabrication and nonlinear optical properties of an ultrathin film with acceptor-donor periodically overlapping structure

A novel ultrathin multilayer film based on noncovalently linked D-A systems using TTAF as acceptor and DHP as donor has been fabricated by means of layer-by-layer electrostatic self-assembly technique on a quartz substrate. Driven by the electrostatic force, TTAF and DHP were alternately adsorbed on the substrate to form D-A periodically overlapping structure. UV-vis spectra showed a continuous and uniform deposition process of TTAF and DHP. The film structure was characterized by small-angle X-ray diffraction measurement and AFM images. The third-order nonlinear optical properties of the film were investigated by the Z-scan technique with laser duration of 8 ns at the wavelength of 532 nm. Experimental results indicate the TTAF/DHP film exhibits saturated absorptive and self-defocusing nonlinearities. The nonlinear absorption coefficient and refractive index of the film are −6.99 × 10−6 m/W and −2.96 × 10−12 m2/W, respectively.