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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.
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Basic Properties of LiNbO3
Crystal Structure: |
Trigonal, Space group R3C, Point group 3m |
Cell Parameters: |
a=5.148Å , c=13.863Å |
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 |
420nm-5200nm |
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 Coef. (@ 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 1.4um
dne/dT=39.073x10-6/K at 1.4um |
The Sellmeier equations
( l in mm) |
no2 = 4.9048+0.11768/(l2-0.04750)-0.027169l2
ne2 = 4.5820+0.099169/(l2-0.04443)-0.021950l2 |
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 |
gT33 = 32 pm/V, gs33 = 31 pm/V,
gT31 =10 pm/V, gs31 =8.6 pm/V,
gT22 = 6.8 pm/V, gs22 = 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 |
Damage Threshold |
100 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 damage threshold is much higher. The Sellmeier equations (for MgO dopant 7 mol%) are:
no2 = 4.8762+ 0.11554/(l2-0.04674)-0.033119l2
no2 = 4.5469+ 0.094779/(l2-0.04439)-0.026721l2
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LiNbO3 Crystals for E-O Devices
Applications that utilize the large electro-optic coefficients of lithium niobate are optical modulation and Q-switching of infrared wavelengths. Because the crystal is non-hygroscopic and has a low half-wave voltage, it is often the material of choice for Q-switches in many applications. The crystal can be operated in a Q-switch configuration with zero residual birefringence and with an electric field that is transverse to the direction of light propagation. Because piezoelectric ringing can be severe, piezoelectrically damped designs can be very useful. The damage threshold of the intrinsic material at 1.06 um with a 10 ns pulse is approximately 3 J/cm2. With appropriate AR coatings, a surface damage threshold of 300-500 MW/cm2 can be achieved for the same conditions.
When the light propagates in z-axis and the electric field is applied along x-axis, the refractive retardation can be expressed as G = 2pLn3r22V/ld. The electro-optic coefficients of LiNbO3 are: g33 = 32 pm/V, g31 = 10 pm/V, g22 = 6.8 pm/V at low frequency and g33 = 31 pm/V, g31 = 8.6 pm/V, g22 = 3.4 pm/V at high electric frequency.
Standard Products
Part No. |
Dimension |
Cut |
End faces |
Side |
Vp |
EOL00 |
9x9x25mm |
Z-cut |
AR@1064nm |
Au on X face |
2.7kV |
Specifications of Finished Products
| Transmitting wavefront distortion: |
less than l/8 @ 633nm |
| Flatness: |
l/8 @ 633nm |
| Scratch/Dig code: |
10/ 5 to MIL-O-13830A |
| Parallelism: |
better than 20 arc seconds |
| Perpendicularity: |
5 arc minutes |
| Angle tolerance: |
△θ < 0.25°, △φ < 0.25° |
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LiNbO3 ( LN, Lithium Niobate ) for A-O Devices
Crystal symmetry: 3m
Density: 4.628 g/cm3
Optical spectral range: 0.4 - 5 um
Elastic constants cij (1011 dyn/cm2 or 1010 Pa):
| 0.03 |
0.079 |
0.104 |
-0.071 |
0 |
0 |
| 0.079 |
0.03 |
0.104 |
0.071 |
0 |
0 |
| 0.172 |
0.172 |
0.078 |
0 |
0 |
0 |
| -0.152 |
0.152 |
0 |
0.22 |
0 |
0 |
| 0 |
0 |
0 |
0 |
0.22 |
-0.152 |
| 0 |
0 |
0 |
0 |
-0.071 |
-0.025 |
Photoelastic constants pij:
| 0.03 |
0.079 |
0.104 |
-0.071 |
0 |
0 |
| 0.079 |
0.03 |
0.104 |
0.071 |
0 |
0 |
| 0.172 |
0.172 |
0.078 |
0 |
0 |
0 |
| -0.152 |
0.152 |
0 |
0.22 |
0 |
0 |
| 0 |
0 |
0 |
0 |
0.22 |
-0.152 |
| 0 |
0 |
0 |
0 |
-0.071 |
-0.025 |
Sound velocity:
| Direction |
Polarization |
v (105 cm/s) |
| [100] |
[100], L |
6.549 |
| [010] |
[010], L |
6.838 |
| [010] |
S |
4.4667 |
| [001] |
[001], L |
7.331 |
| [001] |
[100], S |
3.5885 |
| [010] |
[100], S |
3.838 |
| [001] |
[001], L |
7.271 |
| [100] |
[001], S |
4.801 |
| [100] |
[010], S |
4.0593 |
| [010] |
[010], QL |
6.882 |
| [010] |
[100], S |
3.962 |
| [010] |
[001], QS |
4.494 |
| [001] |
[001] L |
7.333 |
| [001] |
[001] L |
7.22 |
| [010] |
[010] L |
6.58 |
| [100] |
[100] L |
6.57 |
| [001] |
[010] S |
3.57 |
| [001] |
[100] S |
3.57 |
| [001] |
[001] L |
7.331 |
Standard LiNbO3 SAW Wafer
| Diameter: f40.0mm, f50.8mm, f76.2mm , f101.6mm |
| Thickness: 0.2~1.0mm |
| Orientation: X, Y, Z, 127.86° Y, 64° Y, 135° Y |
| Front polish: 0.016 ~0.001μm |
| Back lapping: 0.3 ~10μm |
| Flatness: <15mm |
| Bow: <20mm for f40~ 65 mm, <40mm for f65 ~101.6mm |
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