Ultrafast third-order nonlinear optical properties of a novel 4-methoxy-4’-nitro chalcone by z-scan and degenerate four-wave mixing techniques

Abstract

We have investigated the ultrafast third-order nonlinear optical (NLO) properties of a novel chalcone derivative, 3-(4- methoxyphenyl)-1-(4-nitrophenyl)prop-2-en-1-one (abbreviated as MNC) by Z-scan and degenerate four-wave mixing (DFWM) techniques using femtosecond Ti:Sapphire laser system (~70fs, 1 kHz, 800 nm). The molecular structure of the synthesized chalcone by Claisen-Schmidt condensation reaction was confirmed by FT-IR and 1H NMR spectroscopic techniques. The thermal stability was studied by thermogravimetric/ differential thermal analysis (TG/DTA) technique and melting point was found to be 177 °C. The linear absorption spectra suggest that the MNC chalcone is optically transparent in the Vis-NIR region. The open aperture Z-scan demonstrated two-photon absorption, evident from the reverse saturable absorption type mechanism, while the closed aperture Z-scan demonstrated a positive nonlinear refraction due to self-focusing effect. Further, the chalcone exhibited optical limiting (OL) and optical switching properties. The onset optical limiting threshold fluence was measured at 9.15 mJ/cm2 and the figures of merit for all-optical-switching were satisfied. From DFWM data we measured the magnitude of NLO coefficients, nonlinear response time and dephasing time. The third-order NLO susceptibility and molecular hyperpolarizability were calculated to be 1.39×10-14 esu and 6.89×10-34 esu, respectively, using Z-scan and 6.53×10-14 esu and 32.7×10-34 esu, respectively, using DFWM techniques. From both these techniques the magnitude of NLO coefficients were found to be in good agreement. The time-resolved DFWM studies revealed that the nonlinear response time of MNC was very short (~112 fs). These results indicate that the MNC chalcone is a potential material for optical limiting and all-optical-switching applications.