Investigation of third-order nonlinear optical properties of DMIT derivatives by Z-scan technique

Three 1,3-dithiole-2-thioxo-4,5-dithiolato compounds, ethyltriphenylphosphonium bis(2-thioxo- 1.3-dithiole-4,5-dithiolato) aurate(III) (TPEPADT), benzyltriethylamine bis(2-thioxo- 1.3-dithiole-4,5-dithiolato) aurate(III) (BTEAADT) and benzyltriethylamine bis(2-thioxo-1.3-dithiole-4,5-dithiolato) nickel(III) (BTEANDT), were synthesized and the BTEAADT-doped PMMA thin film (BD film) and TPEPADT-doped PMMA thin film (TD film) with mass fraction of 1% were prepared by spin-coating method. The third-order nonlinear optical properties of thin films and three compounds in acetonitrile solutions were investigated by using the laser Z-scan technique with 20 ps pulses at 1064 nm. The Z-scan spectra revealed that TPEPADT and BTEAADT exhibited self-defocusing effect and negligible nonlinear absorption, but BTEANDT exhibited self-focusing effect and stronger saturable absorption. The reason for this difference was analyzed. The magnitudes of third-order nonlinear refractive indices and thirdorder nonlinear susceptibility were 10(-18)m(2)/W, 10(-13) esu for the solution samples and 10(-15)m(2)/W, 10(-9) esu for thin films. All these results suggest that these materials are promising candidates for application in the nonlinear optical area at infrared band.