A precise optical technique for measuring electronic transport properties in semiconductors is disclosed. The sensitivity of the technique to electronic transport properties follows from a simple analytic expression for the Z dependence of a photo-modulated reflectance signal in terms of the (complex) carrier diffusion length. The sensitivity of the technique to electronic transport properties also enables a trained neural network to predict electronic transport properties directly from Z-scan photo-modulated reflectance data. Synthetic data and/or physical constraints may be derived from the analytical expression and incorporated into a machine learning algorithm. Moreover, electronic transport properties as determined or predicted may be used to enable machine learning based control of semiconductor process tools and/or manufacturing processes, including via advanced reinforcement learning algorithms.