Determination of nonlinear refractive index in a Ta₂O ₅ rib waveguide using self-phase modulation

Self-phase modulation has been observed for ultrashort pulses of wavelength 800nm propagating through a 1 cm-long Ta₂O₅ rib waveguide. The associated nonlinear refractive index n₂ was estimated to be 7.23×10^-19 m²/W, which is higher than silica glass by more than one order of magnitude. Femtosecond time of flight measurements based on a Kerr shutter configuration show that the group velocity dispersion is small at a wavelength of 800 nm, confirming that dispersion may be neglected in the estimation of n² so that a simplified theory can be used with good accuracy.