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.

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The two-photon absorption (TPA) coefficient β and the nonlinear index of refraction n2 for bulk cuprous oxide (Cu2O) direct gap semiconductor single crystal have been measured by using a balance-detection Z-scan single beam technique, with an excellent signal to noise ratio. Both coefficients were measured at 790 nm using a 65 fs laser pulse at a repetition rate of 90.9 MHz, generated by a Ti:Sapphire laser oscillator. The experimental values for β were explained by using a model that includes allowed-allowed, forbidden-allowed, and forbidden-forbidden transitions. It was found that the forbidden-forbidden transition is the dominant mechanism, which is consistent with the band structure of Cu2O. The low value for β found in bulk, as compared with respect to thin film, is explained in terms of the structural change in thin films that result in opposite parities of the conduction and valence band. The n2 is also theoretically calculated by using the TPA dispersion curve and the Kramers-Kronig relations for nonlinear optics.

In this paper, we propose a technique named reflection F-scan or RF-scan, that can be used to measure the nonlinear-refractive index 2 of thin-film semiconductors. In this technique, a p-polarized Gaussian beam is focused using an electrically focus-tunable lens onto a sample, which is positioned at a fixed distance from the lens and makes an angle with respect to the optical axis. Due to EFTL has the capability to vary its focal distance over a specific range when an electric current is applied to it. The electrically focus-tunable lens varies its focal distance as a function of an applied electric current over a specific range thus, when light is focused on the surface of the sample the beam intensity is high enough to generate nonlinear optical effects such as changes in the refractive index of the material. This changes are then register as variations in reflectance, measured by an intensity detector. Results for three-dimensional CH3NH3PbBr3 hybrid perovskite thin films are presented.

The non--linear optical properties of CdS and ZnSe using a new setup which we have named "f--scan". It uses an electrically--focus--tunable--lens instead of a mechanical translation stage. In this talk I will outline the theory, and experimental implementation.