Intuitive model to include the effect of free‐carrier absorption in calculating the two‐photon absorption coefficient

We report a simple model to include the effect of free‐carrier absorption (FCA) in calculating the two‐photon absorption (TPA) coefficient, β, and demonstrate its use in evaluating β from nonlinear transmission experiments. When only linear absorption and TPA are considered and the experimental analysis is carried out in the usual way, β is calculated to be 2.0 and 2.7×10−10 m W−1 for TM and TE polarizations, respectively. Including the effect of FCA in the waveguide, the model predicts β to be 1.5 and 2.0×10−10 m W−1 for TM and TE polarizations, respectively.