Tunability of third-order nonlinear response in nematic liquid crystal E7 via SnO2 nanoparticle doping: a structured temperature-concentration analysis

This study investigates the temperature- and concentration-dependent linear and third-order nonlinear optical properties of SnO2-doped nematic liquid crystal E7. Refractive index measurements confirm that nanoparticle incorporation modifies both ordinary and extraordinary indices while preserving positive birefringence throughout the nematic phase. Kerr-effect analysis shows a pronounced enhancement of nonlinear response at 0.1 wt% SnO2, where the Kerr constant increases from 2.73 × 10–10 m V-2 (pure E7) to 6.94 × 10–10 m V-2, corresponding to an enhancement of approximately 154%. The third-order nonlinear optical susceptibility reaches its maximum value of 7.62 × 10–18 m2 V-2 at the same concentration near the nematic-isotropic transition temperature. At higher nanoparticle loadings, both the Kerr constant and χ(3) decrease, which may be attributed to nanoparticle aggregation and partial disruption of molecular ordering. Inverse Kerr analysis indicates a shift in pre-transition temperature from 332.2 to 332.7 K (ΔT⁓0.5 K), suggesting subtle modifications in the critical behavior near the phase transition. Therefore, these results demonstrate the potential of SnO2-E7 nanocomposites in nonlinear optical applications.