Terahertz-field-driven sub-picosecond optical switching enabled by large third-order optical nonlinearity in a one-dimensional Mott insulator

Sub-picosecond modulation of the optical reflectivity (R) using terahertz electric-field (E-THz) pulses was achieved in a typical one-dimensional Mott insulator, the bromine-bridged nickel compound, [Ni(chxn)(2)Br]Br-2 (chxn: cyclohexanediamine). The reflectivity change (Delta R/R) at around the Mott-gap transition peak (similar to 1.3 eV) was similar to 1% for E-THz similar to 45 kV/cm, and proportional to the square of E-THz. The relaxation time of Delta R/R was under 0.1 ps, enabling optical switching with a high repetition rate in the near-infrared region. The electric-field and probe-energy dependences of Delta R/R demonstrate that the modulation is due to large third-order optical nonlinearity of one-dimensional Mott insulators. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794413]