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Chapter I Brief Introduction...
Figure: 1.9 Plot of conversion efficiency Vs ΔK. Figure: 1.10 Critical phase
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matching.
The phase-matching can be obtained by angle tilting; temperature
tuning or other methods. The angle tilting is mostly used to obtain the phase-
matching as shown in figure (1.10). If the angle between optical axis and
beam propagation (θ) is not equal to 90 0 or 0 0 , it is called the Critical Phase
Matching (CPM). Whereas, the Non-Critical Phase-Matching (NCPM)
obtained values of 90 0 and 0 0 .Two types of phase-matchings are classified in
consideration of polarization of lasers. If the polarizations of two input beams
(for sum of frequency) are parallel to each other, it is called as the type I
phase-matching. If the polarizations are perpendicular to each other, then it is
called type II phase-matching. Type I and Type II phase matching conditions
are shown in figures (1.11) and figure (1.12), respectively.
Figure: 1.11 Type I phase matching. Figure: 1.12 Type II phase
Conversion Efficiency
matching.
The most important aim is to obtain a high conversion efficiency of a
selected NLO crystal. The conversion efficiency has the relationship with