1：Experimental Design and Method Selection:

The study utilized the Z-scan technique to investigate the nonlinear optical properties of few-layer VSe2 nanoflakes prepared by liquid phase exfoliation.

2：Sample Selection and Data Sources:

Few-layer VSe2 nanoflakes were prepared from VSe2 powder mixed with sodium deoxycholate in deionized water and ultrasonicated.

3：List of Experimental Equipment and Materials:

Equipment included a Raman spectrometer (Horiba, Raman Evolution hr800), a femtosecond pulse generator, and a Z-scan setup. Materials included VSe2 powder, sodium deoxycholate, and polyvinyl acetate (PVA).

4：Experimental Procedures and Operational Workflow:

The VSe2 solution was centrifuged, mixed with PVA, and dried to form films. Nonlinear optical properties were measured using the Z-scan technique.

5：Data Analysis Methods:

The nonlinear saturable absorption property and positive nonlinear refractive index of VSe2 were analyzed from Z-scan test results.