Solvent Effect on the Third-Order Nonlinearity and Optical Limiting Ability for a Stilbazolium-like Dye

摘要

Stilbazolium-like dyes, which contain different heterocyclic groups as electron donors and an N-methylphyridinium iodide group as an electron acceptor, are very interesting optical limiting materials. These materials exhibit low linear absorption, but potentially very strong nonlinear absorption at high intensities. In this paper, the results from investigations of the third-order susceptibilities and nonlinear refractive indices of a stilbazolium-like dye, trans-4-(2-(pyrryl)vinyl)-1-methylpyridinium iodide (PVPI), in different solvented. The molecular second-order hyperpolarizability of PVPI increases from 1.6x10~-31 esu in methanol to 3.4x10~-29 esu in chloroform, a factor of 212. The third-order nonlinearity of this compound is dominated by nonlinear absorption, which leads to strong optical limitingof nanosecond laser pulses. The strength of the optical limiting is dramatically influenced by the solvent used, with limiting decreasing in the order chloroform>dichloromethane, 1,2-dichloroethane>methanol, acetonitrile. While both nonlinear absorption and nonlinear scattering contribute to the optical limiting; nonlinear absorption is the dominant mechanism.