Intermolecular charge transfer in donor–acceptor substituted triarylmethane dye for NLO and optical limiting applications

Abstract

The present work reports the intermolecular charge transfer (ICT) between donor and acceptor substituted ethyl violet (EV) (Color Index: 42600) dye for nonlinear optical (NLO) and optical limiting (OL) applications. The functional groups of EV dye have been analyzed by FT-IR spectra and suggest that the ICT process occurs within the dye molecules. Third-order NLO characteristics of EV dye in aqueous solution were investigated by a 5 mW power continuous wave laser operating at 635 nm wavelength. The nonlinear index of refraction (n₂), nonlinear coefficient of absorption (β) and third-order NLO susceptibility [χ⁽³⁾] of EV dye were found to be in the order of 10⁻⁷ cm² W⁻¹, 10⁻³ cm W⁻¹ and 10⁻⁶ esu, respectively. The ground and excited-state absorption cross-sections of the experimental dye were calculated for ensuring the existence of reverse saturable absorption. The OL behavior of aqueous solutions of EV dye was studied, and the limiting threshold was substantially reliant on dye concentration. The obtained results revealed that the EV dye is a possible NLO material for future photonics and optoelectronics applications.