Research on optically sensitive chromophores containing polymeric films (photoreactive organic thin films, POTF) has exploded during the past decade, and it is continuing to be a very active area of science. Several important phenomena have been discovered, especially at the contact of photochemistry (photoisomerization) and nonlinear optics by the photoisomerization of nonlinear optical molecules in polymers. The material published in the book covers photoreactivity in organic films from the most elementary to the most sophisticated backgrounds, and discusses possible technological uses in views of applications for fast electro-optic modulation, optical data storage, and holography. This book is a comprehensive volume that encompasses the known knowledge on ЗЩЕА research and appllications.