Ultrafast optical nonlinearity in the quasi-one-dimensional Mott insulator Sr₂CuO₃

The photoinduced absorption in the quasi-one-dimensional Mott insulator Sr₂CuO₃ in the infrared spectral region was studied. Theoretical calculations based on a two-band Hubbard model explain the experimental observations. Results indicated that the strong two-photon absorption is due to a very large dipole coupling. The potential of Sr₂CuO₃ for all-optical switching was demonstrated by the room temperature picosecond recovery of the optical transparency. The differential transmission was measured as a function of delay time. The relatively long-lived component of the transmission change is associated with the real excitation of the charge-transfer (CT) exciton.