Experimental exploration of the second order nonlinear optical properties of hexagonal boron nitride nanosheets utilizing femtosecond laser pulses

In recent years, hexagonal boron nitride nanosheets (h-BNNs) have gained attention due to their outstanding optical properties. However, researchers have yet to extensively investigate the nonlinear optical (NLO) properties of such new materials. In the present study, NLO properties of h-BNNs were investigated for the first time, to the best of our knowledge, utilizing the Z-scan approach irradiating with 100 fs laser pulses using different excitation wavelengths that vary from 740 to 820 nm at a constant excitation average power of 1 W. The investigated 2D nanomaterial (h-BNNs) was created using mechanical exfoliation, an effective and straightforward approach of producing h-BNNs. The morphology and crystal structure of the samples have been investigated using different techniques, including UV-Vis spectroscopy, transmission electron microscopy, and Raman spectroscopy. The measurements of nonlinearity show that, by increasing the excitation wavelength, the nonlinear absorption coefficient decreases in a linear trend. The as-prepared h-BNNs performed fascinating optical limiting with a reverse saturable behavior. This innovative optical nanomaterial makes them promising sensitive optical components in laser protection applications.