Journal of Nonlinear Optical Physics & Materials Vol. 20, No. 2 (2011) 183–191 c  World Scientific Publishing Company DOI: 10.1142/S0218863511006005 NON-LINEAR REFRACTIVE INDEX MEASUREMENT OF (2E)-3-[4-(DIMETHYLAMINO)PHENYL]-1-(2,5- DIMETHYLTHIOPHEN-3-YL)PROP-2-EN-1-ONE AND (2E)-3-(3,4-DIMETHOXYPHENYL)-1-(2,5-DIMETHYLTHIOPHEN- 3-YL)PROP-2-EN-1-ONE FRYAD Z. HENARI ∗,§ and ABDULLAH M. ASIRI †,‡ ∗ Department of Basic Medical Sciences, Royal College of Surgeons in Ireland, Medical University of Bahrain, P.O. Box 15503, Al Adliyah, Kingdom of Bahrain † Chemistry Department, King Abdul-Aziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia ‡ The Center of Excellence for Advanced Materials Research, King Abdul-Aziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia § fzhenari@rcsi-mub.com Received 17 June 2011 We report results from investigations of the nonlinear refractive index and nonlin- ear absorption coefficient of (2E)-3-[4-(Dimethylamino)phenyl]-1-(2,5-dimethylthiophen- 3-yl)prop-2-en-1-one and (2E)-3-(3,4-Dimethoxyphenyl)-1-(2,5-dimethylthiophen-3-yl) prop-2-en-1-one using Z-scan technique with a continuous wave (cw) laser at wavelengths 488 nm and 514 nm. The nonlinear refractive index and nonlinear absorption coefficient of both samples were evaluated. The origin of the nonlinear effects was discussed. Opti- cal limiting based on light induced nonlinear refractive index variation is demonstrated. The limiting thresholds were estimated for both samples. The results suggested that these materials offer promise as candidates for optical limiting and optical devices in the low power regime. Keywords : Z scan; nonlinear refractive index; nonlinear absorption; optical limiting; dye. 1. Introduction In recent decades, there has been considerable interest in searching for materials exhibiting nonlinear optical effects. These effects are of great technological impor- tance for use in applications in optical limiting and optical switching devices. 1,2 An example of interest that has attracted attention is the light induced refractive index changes and light induced absorption changes. The light induced refractive index changes are commonly described by the rela- tionship n = n + n 2 I , where n is the linear refractive index, I is the intensity of the 183