Bulk ZnSe and CdS two-photon absorption measurement with an F-scan nonlinear absorption spectrometer

Using an electrically focus tunable lens (EFTL) in an F-scan setup and a tunable femtosecond-pulse laser (Mai Tai HP), we were able to measure the degenerated two-photon absorption coefficient (in transmission) of CdS and ZnSe in an extended range of wavelengths (690-1040 nm), with a 5 nm resolution. The process of measuring takes less than 30 minutes. We compared our results with theoretical approaches for the dispersion relations of the nonlinear properties of semiconductors and found excellent agreement with the experimental results. We also compare our results with those reported in the literature. We derive the nonlinear refraction using a Kramers-Kronig relation and compare it with the values reported in the literature. The system has no moving parts, is highly compact, and is fully automated.