Thermal Lensing Effect in Laser Nanofluids Based on Poly (aniline-co-ortho phenylenediamine)@ $$\text{TiO}_{2}$$ TiO 2 Interaction

A poly (aniline-co-ortho phenylenediamine)@ $$\text{TiO}_{2}$$ (PACOPDA@ $$\text{TiO}_{2}$$ ) nanocomposite was constructed by in situ copolymerization and its nanofluid was prepared via a two-step process. The prepared materials were characterized employing Fourier-transform infrared (FTIR) spectroscopy, energy dispersive X-ray (EDX), X-ray diffraction (XRD), field emission scanning electron microsopy (FESEM), and thermogravimetric analysis (TGA). The thermo-optical response of the PACOPDA@ $$\text{TiO}_{2}$$ nanofluid with different input pump power of a laser was investigated. The optical properties of the prepared materials were examined by ultraviolet-visible (UV-Vis) spectroscopy. Spatial self-phase modulation and Z-scan were utilized to study the PACOPDA@ $$\text{TiO}_{2}$$ nanofluid nonlinearity. An enhancement in the thermo-optical property with an increase in the input pump power and concentration of the PACOPDA@ $$\text{TiO}_{2}$$ was observed. The results showed that the PACOPDA@ $$\text{TiO}_{2}$$ nanocomposite offers new potential in nonlinear optical applications. Furthermore, a one-order increase in the nonlinear refractive index of the PACOPDA@ $$\text{TiO}_{2}$$ nanofluid vis-a-vis the PACOPDA was observed. The thermo-optical behavior of the PACOPDA@ $$\text{TiO}_{2}$$ shifts from self-defocussing to self-focusing with increasing intensity and concentration.