Preparation, crystal growth, characterization, thermal and third-order nonlinear optical properties of ethyltriphenylphosphonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate(III) for all-optical switching

A novel organometallic third-order nonlinear optical crystal: ethyltriphenylphosphonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate(III) (ETPPADT) has been prepared, and large optical-quality single crystals have been grown by the solvent evaporation method. Its structural, optical and physicochemical properties are characterized by elemental analyses, UV–Vis–NIR transmission, infrared spectroscopy and thermal analysis. The thin films of ETPPADT doped into poly(methyl methacrylate) (PMMA) with a concentration of 1 wt% have been prepared using spin-coating method. The linear refractive index and the thickness of the thin films were measured by a prism coupler. The third-order nonlinear optical properties of the films have been investigated using Z-scan technique at the wavelength of 1064 nm with laser duration of 20 ps, which reveal that the composited films exhibit large negative nonlinear refractive indices about 4×10−10 esu and no nonlinear absorption. The influence of thickness of the film and the incident laser intensity on the third-order optical nonlinearities have been investigated. Two figures of merit, W and T, have been calculated to be |W|≅120⪢1 and |T|=0⪡1, respectively. All the results show that ETPPADT crystal has potential application on all-optical switching.