A study on the third-order nonlinear optical properties of pure KMnO4 using the CW Z-scan technique

Abstract

Potassium permanganate (KMnO₄) is a remarkably versatile compound with a wide range of applications spanning from household to industrial settings. As a neutral salt, it possesses potent oxidizing properties that make it indispensable in various fields. The third-order nonlinear optical properties of pure KMnO₄ solution with different normality of 0.05 N, 0.0166 N, 0.0125 N, and 0.009 N have been studied using the Z-scan technique with a continuous wave diode pumped solid state (DPSS) 532 nm laser source of 100 mW. By evaluating the closed aperture and the open aperture response, the nonlinear refractive index (n₂) and the nonlinear absorption coefficient (β) were determined for different normality of KMnO₄ solution. Also, using the values of n₂ and β, the third-order nonlinear susceptibility (χ³) was discovered. The normality versus nonlinear refractive index has been assessed by plotting a curve. The closed aperture response reveals the negative sign of the nonlinear refractive index, which indicates the self-defocusing behavior, and the open aperture response demonstrates the reverse saturable absorption (RSA) mechanism. The thermal nature of the KMnO₄ was found by the order of magnitude of the nonlinear refractive index (n₂) and also by investigating the peak-valley separation values. The studies led to further investigation in the field of optical switching.