“…Near z = o, the thin lens had little effect on a focus beam and the aperture transmittance returned to its low intensity value. For z > 0, the negative lensing caused the beam divergence to increase, resulting in a decreased aperture transmittance.When the intensity of the signal was dependent on the cubic power of the incident laser beam, the third-order susceptibilities of the sample could be determined by using CS 2 as a reference under identical conditions [30][31][32][33]. The nonlinear refractive index of CS 2 (n 2;CS 2 ) was considered as (3.1 ± 0.2) Â 10 À18 m 2 /W.…”