Intensity-dependent SA-RSA switching in nickel-chromium transition metal oxide nanoparticles

Abstract

Semiconductor systems are suitable materials for nonlinear-optical applications because of their large optical nonlinearities and rapid response. In this work, NiCr_xFe_2-xO₄ nanoparticles for x = 0.5, 1, 1.5, 2 are synthesized by the co-precipitation method, and its structural, vibrational, and nonlinear optical properties are characterized. All the prepared samples belong to a cubic spinel structure except the sample x = 2, with a rhombohedral structure, with crystallite sizes ranging from 30 to 40 nm and a bandgap ranging from 3.3 eV to 4eV. The aqueous samples show a saturable absorption on irradiating a 532 nm pulsed laser at low intensities and reverse saturable absorption with saturation effects at higher intensities.