Ultrafast Optical Kerr Effect in Amorphous As₂Se₃ Film Induced by Ultrashort Laser Pulses

Nonresonant third-order nonlinear optical properties of amorphous As₂Se₃ film were investigated experimentally by the method of the femtosecond optical heterodyne detection of optical Kerr effect at 805 nm with the 80 fs ultrafast pulses. The results showed that the values of real and imaginary components of third-order susceptibility of amorphous As₂Se₃ film were 5.6 x 10^-12 esu and -2.0 x 10^-13 esu, respectively. Amorphous As₂Se₃ film demonstrated a very fast response time within 200 fs. The ultrafast response and large third-order nonlinearity are attributed to the ultrafast distortion of the electron cloud of As₂Se₃ film.