Nonlinear optical re-orientation and photoacoustic properties of indium tin oxide nanoparticles

Abstract

Abstract The nonlinear optical Kerr effect of indium tin oxide (ITO) nanoparticles (NPs) was investigated using continuous wave laser beams. ITO NPs were synthesized using the sol-gel method and were prepared as a colloid and a thin film. The structural and optical properties of the synthesized particles were characterized by X-ray diffraction analysis, transmission electron microscopy and UV–visible spectroscopy. The energy band gap was found to be 3.45 eV. The nonlinear optical properties of these NPs were measured by two sources: one He–Ne laser beam and a diode laser beam at wavelengths of 632.8 nm and 450 nm, respectively. For the He–Ne laser beam, the obtained nonlinear refractive index was found to be n 2 = + 1.7 × 10 − 7 c m 2 W , which its plus sign indicates that the main nonlinear refractive phenomenon involved was the optical re-orientation effect due to the electric dipole moment of the particles. The high nonlinear absorption of the particles at both wavelengths leads to the creation of intensity-dependent photoacoustic (PA) signals that are mainly in the audible range of sound frequencies. The sonic waves were within a frequency interval of 2–19 KHz. The ITO particles were present as NPs, which simultaneously show optical re-orientation and PA responses under continue wave (CW) laser irradiations. This research thus finds that ITO NPs are a good candidate for electro-optical sensors and applications.