Optical Grade Lithium Niobate, Lithium Tantalate
The next generation of optical materials include single crystals of Lithium Niobate and Lithium Tantalate . The main target of development has been the production of larger diameter wafers (6 inch) to meet optical device manufacturers' requirements.
This has been achieved by :
- Reducing the impurity level using highly selected raw material
- Control of single crystal composition by Curie temperature measurement
- Manipulation of growth in a temperature controlled environment
This has resulted in successful production of 6 inch diameter wafers.
Variation of Refractive Index with Temperature
355nm | 406nm | 532nm | 633nm | 1064nm | ||
---|---|---|---|---|---|---|
Lithium Niobate | 25°C | 2.40179 |
2.32631 |
2.23622 |
2.20351 |
2.15714 |
50°C | 2.40343 |
2.32807 |
2.23765 |
2.20458 |
2.15757 |
|
75°C | 2.40722 |
2.33080 |
2.23940 |
2.20607 |
2.15884 |
|
Magnesium Doped Lithium Niobate | 25°C | 2.38482 |
2.31248 |
2.22530 |
2.19323 |
2.14757 |
50°C | 2.38778 |
2.31441 |
2.22644 |
2.19424 |
2.14861 |
|
75°C | 2.39152 |
2.31718 |
2.22819 |
2.19567 |
2.14966 |
|
Lithium Tantalate | 25°C | 2.34263 |
2.28411 |
2.21086 |
2.18288 |
2.14174 |
50°C | 2.34574 |
2.28625 |
2.21208 |
2.18386 |
2.14250 |
|
75°C | 2.34971 |
2.28877 |
2.21335 |
2.18485 |
2.14333 |
|
SolGel | 25°C | 2.27829 |
2.27014 |
2.19138 |
2.15536 |
2.09486 |
50°C | 2.27985 |
2.27211 |
2.19278 |
2.15641 |
2.09524 |
|
75°C | 2.28344 |
2.27452 |
2.19450 |
2.157869 |
2.09647 |
Sellmeier Coefficients
Evaluation and Quality Control for Optical Wafers
1 Evaluation Using Curie Temperature - Related to the composition of LiNbO3 / LiTaO3
Quality Control level of Curie temperature
|
Curie temperature measurement point |
2 Evaluation Using Refractive Index- Related to the composition of LiNbO3 / LiTaO3
There is significant correlation between refractive index and composition. For quality control purposes, these figures are a measurement to achieve high quality as standard.
Quality Control level of refractive index
|
Refractive index measurement point |
3 X-Ray Topography
This is a very simple way to control the crystal quality to determine whether whether Optical or Saw grade. To improve the quality of optical grade, we aim to achieve sub-grain boundary free wafer.
Magnesium Doped Lithium Niobate for PPLN - (Periodically Poled Lithium Niobate)
It is well known that applying a short wavelength (blue or green) laser to lithium niobate causes "optical damage" through the photo-refrective effect, and also refractive index fluctuations. To control these phenomena, high optical damage threshold materials have been developed, using magnesium as a dopant. The characteristics of Magnesium doped lithium niobate are resistance to optical damage, low absorption loss and no refractive index fluctuation within the crystal.
In general, the main requirement for MgO:LN for optical applications is a stable and homogeneous refractive index;( Erbium doping is also available). At shorter wavelengths, for example with blue lasers, the photorefractive effect must also be considered – here we can see local changes in the refractive index in areas under laser illumination which lead to optical damage.
Development and manufacture of MgO:LN has taken place since 1985. Over this time the focus has been on optimising growth conditions and improving raw material purity (to avoid impurities such as Fe) with the result that sub-grainboundary free material is now readily available with excellent transmission characeristics.
With high optical damage resistance and homogeneity, MgO:LN wafers (upto 4 inches in diameter) are now being used in new applications in the optical network, blue laser and other markets.
Properties of Optical Grade Lithium Niobate, Tantalate, Magnesium doped Lithium Niobate
Optical grade lithium niobate | Optical grade lithium tantalate | Magnesium Doped lithium niobate | ||
---|---|---|---|---|
Composition | 48.5mol% Li |
48.5mol% Li |
48.5% Li, 5mol%MgO |
|
Curie point ° C | 1133 ±2 |
603±2 |
1209±3 |
|
Impurities level ppm |
Fe<1.0, Cu< 0.1 Mn<0.05, Ni<0.1 Cr<0.1,Mo<0.1
|
Fe<1.0, Cu< 0.5 Mn<0.2, Ni<0.1 Cr<0.5,Mo<0.1 |
Fe<1.0, Cu< 0.5 Mn<0.05, Ni<0.1 Cr<0.1,Mo<0.1 |
|
Crystal density (kg/m3) | 4647.022 |
7462.2 |
4642.814 |
|
Lattice constants c(Å) | 13.8658 |
13.8704 |
||
Refractive index at 633nm | ne | 2.2030 |
2.1821 |
2.1936 |
no | 2.2880 |
2.1787 |
2.2831 |
|
Birefingence no- ne | 0.0850 |
-0.0034 |
0.0895 |
|
Transparent wavelength (nm) | 310-5500 |
270-5500 |
300-5500 |
|
Optical damage thresholds at 488nm At-ion laser (kW/cm2) | ~10 |
~10 |
>1700 |
Electro-Optic Coefficients, Nonlinear Optical Coefficients
E-O Coefficients r(10-12) mV-1 at 632.8nm |
Optical grade lithium niobate |
Optical grade lithium tantalate |
|
rT22 |
6.8 |
||
rT33 |
32.2 |
30.5 |
|
rT51 |
32 |
||
rS13 |
11 |
7 |
|
rS22 |
3.4 |
1 |
|
rS33 |
36.7 |
30.3 |
|
rS51 |
18.2 |
20 |
|
Nonlinear Optical Coefficients at 1.06μm (d31=d15) |
d22/d36KDP |
6.5 |
4.4 |
d31/d36KDP |
-12.3 |
-2.7 |
|
d33/d36KDP |
-86 |
-41 |
Transmission Spectra
Photoabsorption : LiNbO3 MgO Doped |
Photoabsorption : LiTaO3 Optical Grade |
Equipment |
Hitachi U-3500 Spectrometer |
|
Sample Thickness | 0.5 mm |
0.5 mm |
Scan Speed | 15 nm/min |
60 nm/min |
Scan Area | 280~500 nm |
250~500 nm |
Sampling | 0.1 nm |
0.1 nm |
Properties LiNbO3 (MgO doped)
MgO | Curie Temperature | Crystal Density | Lattice Constants | Refractive Index | |
---|---|---|---|---|---|
(mol %) |
Tc (° C) |
ρ (kg/m3) |
c(Å) |
ne1 |
no1 |
0 |
1130.7 |
4647.022 |
13.8658 |
2.2031 |
2.2879 |
3 |
1197.7 |
4644.132 |
13.8679 |
2.1953 |
2.2848 |
5 |
1210.2 |
4642.814 |
13.8704 |
2.1936 |
2.2831 |
7 |
1204.1 |
4636.706 |
13.8762 |
2.1921 |
2.2743 |
(1) Prism coupler method - 24°C at 632.8nm, no : TE mode ne : TM mode
Properties Optical grade LiTaO3
Curie Temperature | Crystal Density | Refractive Index | |
---|---|---|---|
Tc (° C) |
ρ (kg/m3) |
ne1 |
no1 |
602.5 |
7462.2 |
2.1821 |
2.1787 |
(1) Prism coupler method - 24°C at 632.8nm, no : TE mode ne : TM mode
General Specification
Material | Cut Angle | Size | Surface Finish | |
Front | Back | |||
LiNbO3 | Z-Cut Y-Cut X-Cut |
3" φ x 0.5 mm T | mirror | FO#1200 |
mirror | mirror | |||
3" φ x 1.0 mm T | mirror | FO#1200 | ||
mirror | mirror | |||
Z-Cut Y-Cut X-Cut |
4" φ x 0.5 mm T | mirror | FO#1200 | |
mirror | mirror | |||
4" φ x 1.0 mm T | mirror | FO#1200 | ||
mirror | mirror | |||
Z-Cut | 5" φ x 1.0 mm T | mirror | mirror | |
MgO:LiNbO3 (MgO 5 mol% ) |
Z-Cut | 3" φ x 0.5 mm T | mirror | mirror |
X-Cut | 3" φ x 1.0 mm T | |||
LiTaO3 | Z-Cut | 2" φ x 0.5 mm T | mirror | mirror |
Note : Fe content is less that 1ppm, all wafers
Other specifications can be provided upon request: Please state
- Cut angle accuracy
- Wafer thickness
- Orientation Flat length
- Wafer Flatness