Photoreactive thin films have been investigated extensively due to the advances in photonics, and the coupling between photochemistry and nonlinear optics has developed into a new discipline since the 1990s. Light can manipulate the orientation of optically sensitive chromophores containing polymeric thin films, and this phenomena has important applications to the field of opto-electronics and photonics especially in such areas as liquid crystals and optical storage of information.;Scientists from different communities have been working in this area representing such fields as chemistry, chemical engineering, polymer science and optics. The purpose of this books is to provide a comprehensive reference covering the basic fundamentals of the interdisciplinary research as well as the applications in photonics.