Power-dependent nonlinear optical behaviours of ponceau BS chromophore at 532 nm via Z-scan technique

Abstract

This paper reports on the power-dependent nonlinear optical (NLO) attributes for both nonlinear refractive index, n2 and nonlinear absorption coefficient, β of Ponceau BS (PBS) chromophore, a synthetic organic compound that falls under azo family. Single-beam Z-scan technique was utilized for the nonlinear measurement. Dominant absorption peak is observed in the visible region due to the high conjugation of diazene functional group absorption. The existence of vital vibrational bonds e.g. the azo bond (1576 cm−1) was confirmed via Fourier Transform Infrared Spectroscopy (FTIR). The intermolecular charge transfer (ICT) of delocalized electrons is responsible for the quick nonlinear response of the sample under intense laser excitation. Response from the closed and open aperture Z-scan technique indicates that PBS chromophore exhibits self-defocusing effects with negative sign of n2 and reverse saturable absorption (RSA) in the order of 10−9 and 10−4 respectively. The real and imaginary components of third order susceptibility, χ3 are relatively high in the order of 10−8 and 10-5 respectively under different laser powers (0.12, 0.14, 0.16, 0.18 & 0.20 W). In short, PBS chromophore shows promising features and can be considered as a potential candidate for various NLO applications under low-power laser operation.