Optical Limiting Performance of Titanium Dioxide-Filled Polyvinylpyrrolidone Composite Nanofibers

In this work, the optical limiting performance of titanium dioxide (TiO₂) particle-filled polyvinylpyrrolidone (PVP) composite nanofibers produced by electrospinning was investigated. Effectively filled PVP composite nanofibers with TiO₂ were observed in the backscattering scanning electron microscopy (SEM) images. A reduced band gap energy of the composite nanofibers was determined with an increasing amount of TiO₂. Increasing localized defect states were obtained with increasing TiO₂ particles in PVP. Furthermore, open-aperture Z-scan experiments at 532 nm were conducted at different intensities to investigate the composite nanofibers' nonlinear absorption (NA) characteristics. The NA signal was obtained for all composite nanofibers, and their main NA mechanism was 2PA. The 2PA coefficient and the NA coefficient values of the pure PVP nanofibers increased with the increase in TiO₂ filler in the PVP nanofibers. This increment indicated the contribution of absorption originating from localized defects inside the NA. Stronger optical limiting performance with a lower onset optical limiting threshold was observed for higher TiO₂-filled PVP composite nanofibers. TiO₂ composite nanofibers could be an effective optical limiter in the visible wavelength range due to their strong optical limiting ability, low onset optical limiting threshold, and high optical damage threshold.