“…Normally, the resonant effects are the strongest and thus may dominate the behavior and the values of χ (3) . On the other hand, in a lossless medium and/or far away from any resonant frequencies (absorption lines) of a material, the dispersion of χ (3) is insignificant and the response is instantaneous; thus χ (3) can be considered dispersion-less. This was shown using the classical anharmonic oscillator model 14 , whereby, basically, the electro-optic Kerr effect (DC Kerr effect) is a quasi-static limit of the optical one (AC Kerr effect).…”