Exceptionally large third-order optical nonlinearity of the organic charge-transfer complex

The organic charge-transfer (CT) complexes that have a mixed-stack structure, in which organic electron donors and electron acceptors stack alternately plane to plane, such as perylene/tetracyanoethylene, showed larger third-harmonic generation than poly-(2,4-hexadiyn-1,6-diol-bis(p-toluenesulfonate), which is known as one of the best organic third-order nonlinear-optical materials. The component molecules of the complexes did not show much optical nonlinearity. The optical nonlinearity is large near the CT absorption-band wavelength along the CT axis, which means that the supramolecular electronic polarization along the CT axis is a novel and efficient origin of third-order optical nonlinearity.