Ultraviolet saturable absorption behavior of black phosphorus

Black phosphorus (BP) has attracted much attention due to its distinctive band-gap properties and strong light-matter interaction, which make it a promising nonlinear optical material. In this study, BP nanosheets were exfoliated successfully utilizing the liquid phase exfoliation technique. Using an open-aperture Z-scan method, the broadband nonlinear absorption characteristics of BP nanosheets were studied. Under 355 nm excitation, the BP nanosheets demonstrated pronounced saturation absorption properties, with the maximum normalized transmittance of the wave peaks reaching 149% at an excitation energy of 7<i>μ</i>J. Moreover, the threshold for nonlinear absorption behavior in BP nanosheets at 355 nm was approximately 0.023 GW cm^-2.The results showed that BP nanosheets possess strong saturable absorption properties in ultraviolet (UV) waveband. The saturable absorption characteristics of BP nanosheets make it possible to apply it in UV laser as saturable absorber, which can broaden its application in UV nonlinear optics.