Plasmon-enhanced broadband visible-light optical limiter with low threshold in silver nanowire filled electrospun...

In this study, the optical limiting (OL) performance of polyvinylpyrrolidone composite nanofibers filled with silver nanowires (PVP/AgNWs), fabricated via electrospinning at varying concentrations, was investigated to achieve efficient OL performance with low optical limiting thresholds (OLT) across the visible spectrum. To reveal the effects of AgNWs on nonlinear absorption (NA), AgNW-filled poly(methyl methacrylate) (PMMA/AgNW) composite nanofibers were also studied since NA was not present in PMMA. Open-aperture (OA) Z-scan experiments were performed at different wavelengths and intensities in the visible region under femtosecond (fs) and nanosecond (ns) pulsed laser excitation. Saturable absorption (SA) behavior was observed at excitation wavelengths between 400 and 600 nm, while a transition to NA behavior occurred at 800 nm for PMMA/AgNW composite nanofibers. This result confirmed the contribution of the surface plasmon resonance band (SPR) to NA. On the other hand, PVP/AgNW composite nanofibers exhibited NA behavior across the visible spectrum at 400, 500, 600 and 800 nm; this effect was enhanced by the incorporation of AgNWs at varying concentrations, resulting in a significant reduction in OLT values. Among the PVP/AgNW composite nanofibers, the strongest NA behavior and the lowest OLT value were obtained for PVP nanofibers with the highest AgNW loading at 800 nm. Under these conditions, in PVP nanofibers, the effective nonlinear absorption coefficient (β_eff) value, which is proportional to the square of the light intensity in light-matter interactions, increased by 1.8 times, while the OLT value decreased by 2.9 times. These findings demonstrate that the incorporation of AgNWs effectively enhances the NA properties of PVP nanofibers and significantly improves their optical limiting performance, mainly due to the plasmonic response and high reflectivity of AgNWs in the visible region.