Large third-order optical nonlinearity of the organic metal α-[bis(ethylenedithio) tetrathiofulvalene] triiodide

The organic metal α-[bis(ethylenedithio) tetrathiofulvalene]2I3 shows a large third-order optical nonlinearity around 650 nm, as observed by forward degenerate four-wave mixing. Nonlinear susceptibilities of ‖χ(3)‖ ∼5×10−8 esu are observed along the direction of maximum conductivity. The frequency dispersion of the nonlinearity points to a plasma effect due to the conduction electrons.