Geoscience Reference
In-Depth Information
(
′′
)
K
%
GaAsO
4
≈
25% ?
40
GaPO
4
Coupling coefficient,
k
20
AT cut angle
30
AlAsO
4
tuPO
4
AlPO
4
Ω
SiO
2
10
10
β
quartz
θ
(
°
)
GaAsO
4
≈
O
°
≈
Y
Cut ?
130
135
140
145
150
155
Figure 5.35 Extrapolation of possible piezoelectric properties to other quartz-like materials
[117]
.
Source: Courtesy of the Academic Press, Orlando, FL.
Table 5.12 Extrapolation of AT-Cut Characteristic from Well-Known Quartz and
Quartz-Like Materials
Material
SiO
2
AlPO
4
FePO
4
AlAsO
4
GaPO
4
GeO
2
GaAsO
4
AT-cut angle (
)
2
35.25
2
33.02
2
20
2
15
2
15
0
0
Coupling coefficient k (%)
8.5
11.0
15
18
18
25
25
c/a
2.20
2.22 2.23
2.23
2.26
2.27
2.28
best compromise for industrial development because of its high AT-cut coupling
coefficient and large temperature range stability with a few drastic packing distor-
tions. If the size of the GaPO
4
crystals grown by the hydrothermal technique is
increased at least by one-fourth the value of the quartz, then GaPO
4
would be the
best piezoelectric material of the twentieth century and probably of the early
twenty-first century as well.
5.5 Potassium Titanyl Phosphate
Potassium titanyl phosphate, KTiOPO
4
(KTP), is one of the best nonlinear optical
materials increasingly being used commercially for the second harmonic generation
(SHG) and parametric oscillation since its discovery and introduction in 1976
[134]
. It all began when there was a search for a suitable crystal to convert effi-
ciently the near-IR light at 1.06
m, which is useful in laser surgery. However,
from the surgeon's point of view, there is a difficulty as the near-IR is not visible
μ
