  We present a detailed investigation on thickness-dependent third-order
(\c{hi}^(3)) nonlinear optical properties of RF-sputtered WSe2 thin-films using
ultrashort pulses centered at different excitation wavelengths. The single-beam
Z-scan based investigation in the visible spectrum reveals the prominent role
of Pauli-blocking towards inducing saturable absorption or optical limiting in
WSe2 thin-films of various thicknesses. The study also explores the dispersion
in third-order nonlinear susceptibility (\c{hi}^(3)) in WSe2 thin films.
Interestingly, WSe2 thin-films of any thickness exhibit a self-focusing effect
depicting a positive nonlinear refractive index (n2 > 0). The
frequency-dependent nonlinear absorption (\b{eta}) bear distinct correlations
with the bandgap of the films which is also investigated through
density-functional-theory (DFT) based simulations. The alteration in
bandstructure is primarily due to the Se-deficiency induced defect bands in
WSe2 thin-films which has discernible impact on the optical limiting
characteristics.
