Defect assisted optical limiting performance of hexagonal boron nitride nanosheets in aqueous suspension and PMMA nanocomposite films

Abstract

Defect-assisted nonlinear absorption (NLA) and optical limiting (OL) performance of hexagonal boron nitride nanosheets (h-BNNS) in aqueous suspension and in polymethyl methacrylate matrix (PMMA) as nanocomposite films were studied using open-aperture Z-scan method. To evaluate the transmission in open-aperture Z -scan data, a theoretical model accounting one photon absorption (OPA), two photon absorption (TPA), free carrier absorption (FCA) and saturation of each process was considered. Defect-assisted NLA coefficients and saturation intensity thresholds were extracted from the fitting of the experimental results for 532 and 1064 nm pulse wavelengths. Strong defect-assisted NLA response of h-BNNS was observed while NLA at 532 nm was considerably stronger. This is attributed to the excitation of a greater number of defect states over a wider energy range. Our findings showed that h-BNNS/PMMA nanocomposite films feature highly required properties in OL applications and can function in OL applications in a wide spectral range (∼200–1064 nm). • Nonlinear absorption (NLA) mechanisms of hexagonal boron nitride nanosheets (h-BNNS). • A theoretical model accounting for one photon absorption, two photon absorption and free carrier absorption. • Defect states residing within the bandgap addressed as the main source of NLA of h-BNNS. • Optical limiting performance of h-BNNS via defect assisted NLA.