Broadband Z-scan characterization using a high-spectral-irradiance, high-quality supercontinuum

We generate a high-spectral-irradiance, high-quality continuum by weakly focusing femtosecond pulses in Kr gas. We use this continuum as a source for rapid Z-scan measurements of the degenerate nonlinear absorption spectrum and the associated dispersion of the nonlinear refraction in optical materials throughout the visible. We measure the degenerate two-photon absorption spectra and the dispersion of the nonlinear refractive index, n₂, of two well-characterized semiconductors (ZnSe and ZnS) as reference samples for our method, along with dilute solutions of organic materials. The latter materials demonstrate application of the technique to samples with lower nonlinearities.