Impact of silver nanoparticle two-photon resonance on Kerr effect of organic dye solutions

Abstract

In this work, we studied the spectral dispersion of two-photon absorption (2PA) and the Kerr effect of core-shell silver nanoparticles (NPs) with thiol-termination ligand cladding in a dichloromethane (DCM) solution and their influence on the nonlinear optical response of 2-[4-(N,N-dimethylamino)-benzylidene]-indane-1,3-dione (DMABI) molecules. To study the spectral dispersion of nonlinear optical properties, we used the Z-scan method with a tunable picosecond (ps) laser with a 27.5 ps pulse duration and 1000 Hz pulse repetition rate. Measurements were carried out in a spectral range between 600 nm and 1100 nm. Four types of samples were studied: pure DCM solvent, NPs dispersed in DCM, a DMABI solution in DCM, and a DMABI/NP mixture in DCM. NP size distribution measurements showed two NP groups with average sizes of 4 and 40 nm. NPs exhibited a strong 2PA in a range of 710–900 nm. Nonlinear optical measurements of DMABI showed that the presence of NPs did not influence the 2PA of DMABI. When comparing the nonlinear refractive index values of DMABI in cases with and without NPs, a difference in signals was observed that correlated with the 2PA of NPs. Polarization-resolved Z-scan measurements showed that the reorientation contribution of the Kerr effect changed due to the presence of NPs.