Chemistry Reference
In-Depth Information
Figure 6.30. The NLO coe
cients for different molecular orientation configurations.
(Modified from Donald and Windle, 1992.)
Table 6.11. The second NLO coecients of several impor-
tant NLO inorganic materials and the organic crystal MNA
(The Chemical Rubber Company, 1971) (unit: 10
−
12
m
/
V).
χ
(2)
P
χ
(2)
D
Material
Tensor element/ijk
quartz
111
1.37
0.8
KDP(KH
2
PO
4
)
321
21.6
0.94
zinc oxide
333
26.3
14
LiNbO
3
333
410
82
MNA
333
540
500
The third NLO susceptibility may not be zero even though the molec-
ular orientation is completely randomly distributed,
i.e.
, in an isotropic
state. The highly ordered phase usually has a high value for the third NLO
coecient. For example, the highly ordered nematic phase has a third
NLO coecient five times that in the isotropic phase.
The NLO materials used so far are mainly inorganic materials, such as
quartz, KDP, zinc oxide, LiNbO
3
,
etc
. The ions in these inorganic materials
are responsible for the NLO properties. The ions have a great mass so that
the NLO coecients of these NLO materials are small at high frequency.
Table 6.11 lists elements of the NLO tensors of the Pockel effect and of
the second harmonic generation for some widely used NLO materials,
χ
(2)
P
and
χ
(2
D
.
