Combined photothermal lens and photothermal mirror Z-scan of semiconductors

We perform thermal lens and thermal mirror Z-scan experiments to study the photothermal properties of semiconductors. We fix the sample’s position, facilitating the alignment procedure and the experiment’s interpretation. By scanning the lens, which focuses the pump beam, we obtain the Z-scan signature. A diode laser at 1064 nm provides the probe beam for the thermal lens experiment, while a Helium–Neon laser generates it for the photothermal mirror one. Using a telescope, we collimated the probe beam having a nearly constant radius of few millimeters. In this configuration, the z-scan response is single peaked. We fit both experimental results using a model based on the Fresnel diffraction approximation. The fitting determines the photothermal phase shift, the photothermal quantum yield, the temperature change of the optical path, and the thermal diffusivity. We study two semiconductors: Gallium Arsenide and Silicon obtaining good agreement with previously reported data.