In this study, three azo dyes bearing coumarin thiophene (6a-c) were synthesized, and their photophysical properties were studied via UV-vis spectroscopy in various solvents. Acidochromic properties were also investigated in DMSO/H2O, and all products showed acidochromic properties. The reversibility studies were carried out to investigate the reusability of the prepared compounds. Furthermore, products 6a-c were also investigated for their potential use as hydroxide sensors. The electric field-induced second harmonic generation (EFISH) technique was used to measure the second-order nonlinear optical properties. The thermal properties of the prepared compounds were investigated via thermogravimetric analysis (TGA). The results showed that the samples are thermally stable up to around 200 degrees C. The protonation of the compounds and their nonlinear optical (NLO) properties were investigated in the framework of Density Functional Theory (DFT) calculations.