Nonlinear optical properties of an organic film formed of dye aggregates with absorption in the telecommunication wavelength range

An organic film formed of newly synthesized dye aggregates with an absorption peak in telecommunication wavelength range exhibited large third-order nonlinear optical susceptibility ${\chi }^{\text{(3)}}$ and fast recovery of bleached absorption. A derivative with a di(benzofuranonyl)methanolate structure forms stable aggregates in a spin-coated film and shows an absorption maximum at 1.24 μm. An imaginary part ${\chi }_I^{\text{(3)}}$ of the film assumes a maximum at 1.30 μm, which is ${\text{−0.83×10}}^{\text{−7}}\hspace{0.17em}\mathrm{esu}.$ The time evolution of differential transmission spectra indicates that the time constant of the recovery of bleached absorption is 80–240 fs for a fast component and 2.2–6.5 ps for a slow one. This organic film has considerable advantages for future planar optical devices.