Cumulative Dissertation on models in nonlinear condensed-matter optics. In chapter 2, the coupled-wave theory first introduced by Kogelnik is reviewed and extended with emphasis on out-of-phase mixed holographic gratings. This class of gratings becomes increasingly important due to novel methods of hologram recording and new classes of materials and metamaterials like holographic polymer dispersed liquid crystals. Additionally, advances in laser technology suggest a stronger spectro- scopic view on holography. The model presented in this thesis accounts for both of these demands and provides a closed analytical solution. Chapter 3 contributes to the field of space-charge waves (SCW), which provides powerful tools for material analysis, especially in semiconductor technology. Although the underlying theory is generally understood, recent improvements of the ex- perimental techniques required extensions of the model and the interpretation of new effects. In this thesis, the existing formalism is adapted to a new method of excitation, which not only simplifies the experimental setup, allowing for easier adoption into industrial environments, but also provides insight into the direction of carrier motion. Furthermore, the model is extended to describe the influence of an external magnetic field, adding the possibility to examine the Hall mobility of carriers. Eventually, chapter 4 studies the dynamics of light induced absorption in pho- tochromic [Ru(bpy)2 (OSO)]+ . Compared to other photofunctional compounds, this molecule is nontoxic and exhibits exceptional photochromic reactions. These properties make it a promising candidate for important industrial and technological applications, ranging from data storage to non-electronic computation. For a profound analysis, the models used for the description of photofunctional molecules have been completely revised to account for the pronounced absortion changes in the material. Furthermore, a setup with orthogonal pump and probe beams is modeled and exper- imentally tested. This novel geometry is introduced to resemble common industrial setups.