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LN (Lithium niobate, LiNbO3)
LN is one of the most thoroughly characterized nonlinear
optical materials and suitable for a variety of frequency conversion
applications. Crystal growing techniques allows consistent production of
large crystals of high perfection. Lithium niobate crystals with various dopings (MgO, Fe,
ZnO ) also have been developed to improve some properties of the intrinsic
material.
LN is also widely used in
electro-optics and
acoustic-optics.
Basic Properties of LiNbO3
|
Crystal
Structure |
Trigonal, Space
group R3C, Point group 3m |
|
Cell Parameters
|
a=5.148 Å ,
c=13.863 Å |
|
Melting Point
|
1253 deg C
|
|
Curie Temperature
|
1140 deg C
|
|
Mohs Hardness |
5 |
|
Density: |
4.64 g/cm3
|
|
Deliquescence
|
None
|
|
Optical
Homogeneity |
~ 5x10-5/cm |
|
Transparency Range
|
420 nm-5200 nm
|
|
Absorption Coefficient |
~0.1%/cm @ 1064nm
|
|
Refractive
indices at 1064nm |
ne= 2.146, no
= 2.220 @ 1300 nm
ne = 2.156, no = 2.232 @ 1064 nm
ne = 2.203, no
= 2.286 @ 632.8 nm |
|
Thermal Expansion Coefficient
(@ 25oC) |
//a, 2.0x10-6/K |
|
//c, 16.7x10-6/K |
|
Thermal
Conductivity Coefficient: |
38 W/m/K at 250
oC
|
|
Thermal Optical Coefficient |
dno/dT=-0.874x10-6/K
at 1.4µm
dne/dT=39.073x10-6/K
at 1.4µm |
|
The Sellmeier
equations
(λ in µm)
|
no2 = 4.9048+0.11768/(λ2-0.04750)-0.027169λ2
ne2 =
4.5820+0.099169/(λ2-0.04443)-0.021950λ2 |
Nonlinear Optical Properties
|
NLO Coefficients |
d33 = 34.4 pm/V
d31 = d15 = 5.95 pm/V
d22 = 3.07 pm/V |
|
Effective NLO coefficients |
deff =5.7 pm/V for frequency doubling 1300 nm;
deff =5.3 pm/V for OPO pumped at 1064 nm;
deff =17.6 pm/V for quasi-phase-matched
structure. |
|
Electro-Optic Coefficients |
γT33 = 32 pm/V,
γs33 = 31
pm/V,
γT31
= 10 pm/V, γs31 = 8.6 pm/V,
γT22
= 6.8 pm/V, γs22
= 3.4 pm/V, |
|
Half-Wave Voltage, DC |
E//z, k-vector ^z: |
E//x or y, k-vector ||z: |
|
3.03 KV |
4.02 KV |
|
Photorefractive Damage Threshold |
50 MW/cm2 (10 ns, 1064nm) |
|
Surface Damage Threshold |
300 MW/cm2 (10 ns, 1064nm) |
We can also
provide
MgO:LiNbO3 and
Fe:LiNbO3 crystals. The MgO: LiNbO3 has similar effective nonlinear coefficients
to pure LiNbO3,
but the photorefractive damage threshold is much higher. The Sellmeier
equations are:
MgO dopant 5 mol%
no2
= 4.9017+0.112280/(λ2-0.049656)-0.039636λ2
ne2 = 4.5583+0.091806/(λ2-0.048086)-0.032068λ2
MgO dopant 7 mol%
no2
= 4.8762+0.11554/(λ2-0.04674)-0.033119λ2
ne2 = 4.5469+0.094779/(λ2-0.04439)-0.026721λ2
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