  The topological behavior of heavy metal alloys opens a vast area for
incredible research and future technology. Here, we extend our previous report
about the superconducting properties of Sn0.4Sb0.6 along with the compositional
variation of Sn and Sb in SnxSb1-x (with (X=0.5 and 0.6)) to study the detailed
optical properties. Structural and morphological details of grown crystal are
carried from the previous study. Further, the samples are excited by a pump of
2.61 eV with a broad probe of 0.77-1.54 eV in the NIR regime for transient
reflectance ultrafast studies (TRUS) measurements. The differential reflectance
profile shows an unprecedented negative magnitude, and the average
power-dependent analysis of this negative trend has been analyzed. This article
not only provides evidence of band filling phenomenon in the samples but also
shows that with the variation of average power, there is a definite increase in
the excited charge carriers, and thereby enhancing the band filling response.
The estimated value of the bandgap between the band filled states and valence
state is also determined from these studies. The nonlinear properties and
bandgap analysis of the studied topological alloys and similar materials help
in the advancement of various nonlinear optical applications.
