Study Nonlinear Optical Properties Of Two Molecular Forms Of Rhodamine Bdye Solution

Abstract

In this study two forms of preparedRhodamine B (RhB) dye atconcentration(10^-5) M in a solvent methanol at room temperature, were measured using a UV-Visible spectrophotometerto determine the linear index of refraction and the linear coefficient of absorption. The results show that the index of refraction increased when acids were added, but decreased when bases were added. The nonlinear optical properties of the samples, such as the nonlinear index of refraction and the nonlinearcoefficient of absorbance, were calculated by using two sections of the Z-Scan technique. The first was a closed aperture that was mounted ahead of the detector to determine the nonlinear refractive index. The aperture ahead of the detector was removed (open aperture) to measure the coefficient of nonlinear absorption in the second part. The two cases were carried out with a continuous wave (CW) diode laser with a wavelength of 457 nm and an input power of 112 mW.  The results show that two molecular forms of the RhB dye solution a negative refractive index (-n₂), which led to self-defocusing and two-photon absorption for an open aperture Z-Scan, indicating that the laser dye in this study can be used in nonlinear optics and optical limiter applications.