Three p-tert-butylthia calix[4]arene derivatives containing p-toluenesulfonyl groups at the lower rim and characterized by their high electron density and aromatic content were synthesized. These were analyzed using FT-IR, NMR, elemental analysis, and optical absorption spectra. Thin films of the compounds were created via thermal evaporation and assessed through UV–Visible spectroscopy, with dielectric and dispersion properties compared to existing literature. The results reveal that the band energy gaps for compounds 2–4 are 3.70, 3.23, and 2.90 eV, respectively. The increased conjugation and high absorption coefficients observed make these materials promising for optoelectronic applications. The films exhibited extraordinarily high nonlinear optical properties, with refractive index and third-order nonlinear susceptibility approximately 400 times greater than those of chalcogenide and oxide materials, highlighting their suitability for nonlinear optical systems. Furthermore, our findings are consistent with density functional theory (DFT) calculations using the Becke, 3-parameter, Lee-Yang-Parr (B3LYP) approach at the 6-311G(d,p) level, validating the theoretical predictions with experimental data.