Described herein is the optical phase-change and photothermal phenomena induced by a two-wave mixing configuration in a nonlinear optical material. For experimental analysis of these findings, the third-order nonlinear optical response exhibited by bimetallic Au-Pt nanoparticles embedded in a TiO2 matrix was studied. A vectorial two-wave mixing technique was conducted to explore the automatic generation of polarized self-diffraction by the participation of the optical Kerr effect in the samples. Fractional derivative calculations allowed us to identify the physical mechanism responsible for photothermal influence on the third-order nonlinear optical effects in the nanosystems. A 532 nm wavelength emitted by the second harmonic of a nanosecond Nd:YAG laser system was employed as an optical source in our measurements. Based on the importance of the vectorial nature of light for dictating the amplitude of the beams and splitting properties, within this work is highlighted the attractive energy transfer functions and phase modulation that can be envisioned by photothermally-controlled interactions.