The field of nonlinear optics, which has undergone a very rapid
development since the discovery of lasers in the early sixties,
continues to be an active and rapidly developing - search area. The
interest is mainly due to the potential applications of nonlinear
optics: - rectly in telecommunications for high rate data transmission,
image processing and recognition or indirectly from the possibility of
obtaining large wavelength range tuneable lasers for applications in
industry, medicine, biology, data storage and retrieval, etc. New
phenomena and materials continue to appear regularly, renewing the
field. This has proven to be especially true over the last five years.
New materials such as organics have been developed with very large
second- and third-order nonlinear optical responses. Imp- tant
developments in the areas of photorefractivity, all optical phenomena,
frequency conv- sion and electro-optics have been observed. In parallel,
a number of new phenomena have been reported, some of them challenging
the previously held concepts. For example, solitons based on
second-order nonlinearities have been observed in photorefractive
materials and frequency doubling crystals, destroying the perception
that third order nonlinearities are - quired for their generation and
propagation. New ways of creating and manipulating nonl- ear optical
materials have been developed. An example is the creation of highly
nonlinear (second-order active) polymers by static electric field,
photo-assisted or all-optical poling. Nonlinear optics involves, by
definition, the product of electromagnetic fields. As a con- quence, it
leads to the beam control.