Abstract
As a rapidly expanding family of two-dimensional (2D) materials, MXenes
have recently gained considerable attention due to their appealing
properties. Here, by developing a solution-based coating method that
enables transfer-free and layer-by-layer film coating, we investigate
the layer-dependent nonlinear optical absorption of Ti3C2Tx films ‒ an
important member of the MXene family. By using the Z-scan technique, we
characterize the nonlinear absorption of the prepared MXene films
consisting of different numbers of monolayers. The results show that
there is a strong and layer-dependent nonlinear absorption behavior,
transitioning from revisable saturable absorption (RSA) to saturable
absorption (SA) as the layer number increases from 5 to 30. Notably, the
nonlinear absorption coefficient β varies significantly within
this range, changing from ~7.13 × 102 cm/GW to
~-2.69 × 102 cm/GW. We also characterize the
power-dependent nonlinear absorption of the MXene films at various
incident laser intensities, and a decreasing trend in β is
observed for increasing laser intensity. These results reveal the
intriguing layer-dependent nonlinear optical properties of 2D MXene
films, highlighting their versatility and potential for implementing
high-performance nonlinear photonic devices.