Fabrication, Characterization of Basic Blue 7 Dye-Doped PVA Films and Their Third-Order Nonlinear Optical Properties.

In this work, we report on the fabrication, characterization and the third-order nonlinear optical (NLO) properties of basic blue 7 (BB 7) dye‒doped polyvinyl alcohol (PVA) polymer thin films. The absorption spectra of BB 7 dye‒PVA films were measured by UV‒visible absorption studies. The functional groups of BB 7‒PVA films have been identified by FT‒IR spectroscopic analysis. The surface morphology was examined by AFM and SEM analysis which shows that the BB 7 dye‒doped PVA films have a homogenous and smooth surface. The nonlinear absorption and refraction of BB 7‒PVA films were respectively explored by open aperture and closed aperture Z‒scan technique using a 5 mW semiconductor diode laser of 635 nm wavelengths. The BB 7‒PVA films exhibit the reverse saturable absorption (RSA) and self-defocusing effect and the measured third‒order nonlinear susceptibility χ values of these films were found to be of the order of 10 esu. The present experimental results show that BB 7‒PVA films may have potential applications in future photonic and NLO devices.