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Chapter I Brief Introduction...
medium is of the order of 10 7
to 10 10
V/cm. Therefore, normal light source is
unable to affect the atomic fields of the medium and thereby the optical
properties of the medium. On the other hand, lasers generate electric field
strength of the order of 10 5
to 10 9
V/cm, which is able to commensurate to that
of the atomic electric fields of the medium. This affects the optical properties
of the medium and thus generates new electromagnetic fields altered in
phase, frequency and amplitude.
The first demonstration of Nonlinear Optical (NLO) frequency
conversion took place as early as in 1961 by Franken et al [8]. They used
quartz crystal to double the frequency of 694 nm light of Ruby laser. Inasmuch
as the interaction was not phase matched, the ultraviolet output power was so
small that the editors of the journal mistook for a blemish the spot on
spectrograph plate that demonstrated the new effect. However, in the end
1962, the classical paper appeared in which Armstrong et al, [9] have given
the theoretical underpinning for both microscopic origin of the nonlinear
susceptibilities and the propagation effects governing macroscopic Nonlinear
interactions between electro-magnetic waves. Later on, Nicolas Bloembergen
won Nobel Prize in 1981 for his contribution in laser spectroscopy. Also, the
selected papers of Bloembergen were published under the title,” Encounter in
the Nonlinear Optics” [10]. Then the quest began for identifying various
nonlinear optical materials and which had gathered momentum in past more
than one decade.
The present author feels pride to write this brief introduction to the
nonlinear optics on 50 th year of its discovery.
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