Nonlinear optical studies of organic compounds using z-scan technique at 532 nm

Abstract

This research reports on the third order nonlinear optical (NLO) attributes for both nonlinear refractive indices, ??2 and nonlinear absorption coefficient, ?? of various type of organic compounds, namely ??-Mangostin (??-MG), Malachite green (MG), Light Green SF Yellowish (LGSF), Coumarin 500 (C500) and Ponceau BS (PBS). The purpose of this study are comprised by optimizations of Z-scan measurements in order to determine the nonlinear refraction (NLR) and nonlinear absorption (NLA) behaviours of each compound mentioned and also to detect the optical limiting (OL) threshold for further applications. A single-beam Z-scan technique was utilized for the nonlinearity measurement. This indicated the NLA phenomena paralleled with the laser excitations wavelength, (??=532 ????) The existence of vital vibrational ??-bonds for intermolecular charge transfer (ICT) of the compounds were confirmed via Fourier Transform Infrared (FTIR) Spectroscopy. The vibrational ??-bonds are responsible for the appearance of remarkable responds towards nonlinearity under intense laser power. To calculate the values of nonlinearity, Thermal Lens Model (TLM) fitting curve was used due to the significant contribution of heat in continuous-wave (CW) laser setup. For instance, MG, LGSF and PBS chromophores possess both NLR and NLA from closed and open aperture signals, respectively. It was recorded that the magnitude of third order optical susceptibility, |??3| of the chromophores were in the order of 10-6 (MG), 10-6 (LGSF) and 10-5 (PBS). On the other hand, ??-MG and C500 revealed closed-aperture signals only with the value of |??3| in the order of 10-11and 10-8 respectively. The power range used in the experiment varies between each sample starting from 0.10 W (min.) to 2 W (max.) depending to the positive respond shown in specific samples. As a whole, all samples exhibited NLO properties under intense laser power. The open aperture signals appeared in MG, LGSF and PBS chromophore as a reverse saturable absorption (RSA). Thus, MG, LGSF and PBS chromophores OL threshold is found at 0.567, 1.154 and 1.124 W, respectively and it can be further developed as optical limiter for optical safety purposes.