Third-order nonlinear optical properties of Co(dmit) 2 complexes using Z-scan technique

Abstract

ABSTRACT Three novel dmit 2- complexes: [(CH 3 ) 4 N][Co(dmit) 2 ] , [(C 3 H 7 ) 4 N][Co(dmit) 2 ] and [(C 4 H 9 ) 4 N][Co(dmit) 2 ], (abbreviated as MeCo, 2-PrCo and BuCo, respectively and dmit =4,5-dithiolate-1,3-dithiole-2-thione), were synthesized and the third-order optical nonlinearities of their acetone solution of the same concentration we re characterized by Z-scan technique at the wavelength of 1064 nm with laser duration of 40 ps. Their Z-scan curves all revealed a negative nonlinear refraction and a positive absorption at 1064nm.The molecular second hyperpolarizability  of MeCo, PrCo and BuCo are 5.11×10 -31 ,4.99×10 ,5.60×10 -31 (esu), respectively. The linear absorption coefficients . and the nonlinear absorption coefficient  of them are 0.3, 0.25, 0.32 (cm -1 ) and 1.53×10 -12 , 1.38×10 -12 , 1.85×10 -12 (cm/W), respectively. The experiment results suggested that complexes with stronger linear absorption have larger nonlinear absorption and two-photon absorption. This difference is due to near resonant effect of sample with str onger absorption. So the linear absorption of complexes at 1064nm is a significant factor to influence the nonlinear absorption. These samples’ large nonlinear absorption suggests that these materials have potential application in optical limiting. Keywords: Nonlinear optics; Z-scan Technology; dmit organometallic complex 1.