Chi-3\u27s: Their characterization and understanding

The third-order nonlinear optical susceptibility χ(3), where the values for this quantity are quoted that vary in magnitude depending on the material and source used, in particular the source pulsewidth, is discussed. The causal relations between the refractive and absorptive components are also discussed and show experiments where the dispersion of the nonlinear refraction can be directly calculated from the nonlinear absorption spectrum. A method for directly obtaining nonlinear spectra as well as determining the response time of the nonlinearity uses a fixed frequency pump and a white-light-continuum probe