Page 20 - Photoreactive Organic Thin Films

i» PREFACE

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 non-
linear 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 POTF research and applications.
POTF have been investigated intensively in the past few years due to
requirements in the areas of optoelectronics and photonics; and linear and
nonlinear optical (NLO) effects induced by photo-orientation of photo-
isomerizabie NLO chromophores in polymers have attracted much attention.
Light can manipulate the chromophores' orientation by photoisomerization
via polarized transitions such that centrosymmetry and isotropy are
alleviated, and anisotropy and quadratic and cubic optical nonlinearities are
induced. Optical poling techniques, e.g. induced molecular polar orientation,
which result in second order NLO effects have been reported, and the
coupling between photochemistry and organic nonlinear optics has emerged
as a new discipline in the past decade. Surface relief gratings created by

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