THIS work presents new insights into optical loss dynamics in semiconductor bulk and metastructures. To this end, a widely applicable modeling scheme for the calculation of photoinduced charge carrier and heat dynamics in arbitrarily shaped semiconductor structures is developed. Analytical solutions of the underlying equations are found for special, though practically widely applied geometries, enabling an efficient calculation of charge carrier concentration and temperature fields. Such a solution is used for the investigation of self-heating in optical microring resonators for temperature sensing, pointing out the importance of two-photon absorption effects even at moderate excitation powers[1]. Furthermore, the rigorous modeling scheme is utilized to identify key signal contributions in photothermal deflection spectroscopy (PDS) [2], a widely applied tool for spatially resolved absorption measurements [3,4,5]. It turns out that nonlinear absorption and angular deflection effects occur in a variety of experimental configurations [6]. These secondary effects must be handled carefully for a quantitative determination of absorption parameters. In particular, absorption coefficients close to interfaces turn out to get overestimated when angular effects are not separated [7]. A general guideline for the reliable determination of optical loss parameters is presented, accounting for all signal influences. That guideline is supported by PDS measurements in crystalline silicon. Finally, a new approach for the spatially resolved separation of various absorption mechanisms is introduced, combining intensity dependent PDS with dynamical optical loss modeling [8]. That approach is applied on silicon, gallium arsenide and cadmium telluride (CdTe), reproducing previously measured twophoton absorption coefficients and determining the strength of the Franz-Keldysh effect in polycrystalline CdTe for the first time.