Single Beam Z-Scan Measurements of Nonlinear Refraction and Nonlinear Absorption Coefficients in Silver Nano-Fluid

Abstract

Problem statement: The nonlinear refractive index and nonlinear absorption are two important optical phenomena which are extensively used in optical switching, optical limiting and labeling. Approach: In the present research we had measured nonlinearity of Ag nano-fluid prepared using γ-irradiation method. The measurement was carried out using a single beam z-scan technique. Under a CW laser beam excitation operated at 532 nm with the power output of 40 mW, a closed aperture setup was used for thermal-induced nonlinear refractive index and an open aperture setup was applied for measuring nonlinearity absorption. Results: We measured the nonlinear refraction coefficient and nonlinear absorption coefficients for silver nano-fluid at concentration 6.475×10 −3 M, the values obtained were-6.173×10 −8 cm 2 W −1 and 7.994×10 −3 cm W −1 respectively. Conclusion: The nonlinear refraction coefficient with the negative sign indicates the self-defocusing phenomenon. The experimental data from open aperture measurement showed that a two photon absorption phenomenon. These results showed that the Ag nano-fluid has significant values of nonlinear refractive index and nonlinear absorption, thus it could be good candidate for optical devices.