Characterization of the fast component of the complex third-order nonlinearity and time response of bulk materials and waveguides

We report a simple method to measure the third-order nonlinear refraction and absorption of bulk materials and waveguides. This method relies on the nonlinear evolution of the spectral intensity and width of femto-second pulses, owing to self-phase modulation, according to a variable chirp introduced before propagation through the nonlinear sample. We describe the experimental details, and we present a comprehensive numerical analysis of the dispersive and the nonlinear effects that can influence the measurement. We also extend the method to characterize the time response of the fast cubic nonlinearity. (C) 2001 Optical Society of America.