Lithium Niobate
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Download Lithium Niobate Datasheet (PDF, 122 KB) |
Lithium niobate (LiNbO3) is a ferroelectric crystal that belongs to the trigonal crystal system.
Lithium niobate is transparent between 0.25 and 5.3 μm (fig. 1). It can be used in visible, near IR and middle IR region.
Fig. 1. Transmittance spectrum of lithium niobate.
As any ferroelectric, lithium niobate demonstrates piezoelectric effect, nonlinear optic effects, photoelastic effect and Pockels effect (linear electro-optic effect). What makes lithium niobate stand out is that the coefficients characterizing these effects are several times greater than those of similar ferroelectrics, facilitating its usage for various applications.
Due to its high electro-optical coefficients, lithium niobate is used for optical amplitude and phase modulators, Pockels cells, laser Q-switching modulators.
Non-linear optical properties of lithium niobate allow its application for optical parametric oscillators and parametric amplifiers for a wide wavelength range.
Lithium niobate is the best choice for second harmonic generator in Nd:YAG laser operating at 1.064 μm, as well as semiconductor lasers operating at 1.3 and 1.55 μm.
It should be noted that non-doped lithium niobate exhibits high photorefraction. Therefore in high-power laser applications, magnesium oxide-doped crystals (MgO:LiNbO3) are used. They have a higher Laser Damage Threshold. At the same time, the doping has no effect on the optical properties of the crystal.
Physical properties of lithium niobate crystals are summarized in Table 1 below.
Table 1. Key physical properties of optical grade non-doped lithium niobate crystals.
| Crystal structure | Rhombohedral, space group R3c, point group 3m |
| Primitive cell dimensions, Å | a=5.148, c=13.868 |
| Refractive indices |
no=2.220, ne=2.146 @1300 nm |
| Optical homogenity, cm-1 | ~5×10-5 |
| Density, g/cm3 | 4.64 |
| Curie temperature, °С | 1157 |
| Melting point, °С | 1253 |
| Mohs hardness | 5 |
| Thermal expansion coefficients (@ 25°С), K-1 | ||c=4х10-6, ⊥ c=15.7х10-6 |
| Thermal conductivity, Вт/(м × K) | ||c=4.61, ⊥ c=4.19 |
| Specific heat capacity, J/(kg × K) | 648 |
| Elastic constants, GPa (@298 K) | СE11=204, CE33=246, CE44=60, CE13=75, CE14=9 |
| Piezoelectric constants, C/N | D22=20.8×10-12, D33=6.5×10-12 |
| Dielectric constants (@300 K) |
εT11/ε0=85.2, εT33/ε0=30, |
| Nonlinear optic coefficients, m/V | d33=37.8х10-12, d31=5.1 х10-12, d22=2.46 х10-12 |
| Sellmeier equation coefficients (λ in μm) |
no2=4.9048+0.11768/(λ2-0.04750)-0.027169λ2 |
| Damage Threshold, MW/cm2 (10 ns, 1064 nm) | 100 |
| Water solubility | Insoluble |
The properties of LiNbO3 optical parts produced by our company are listed below:
- Maximum diameter (length) of the parts – up to 100 mm;
- Crystal orientation – on request;
- Orientation tolerance – ±10';
- Surface quality – 20/10 scr/dig;
- Surface parallelism – 20 arcseconds;
- Perpendicularity – 5 arcminutes.
Please pay attention that this article is only for your information. We do not supply lithium niobate in boules, ingots as well as semi-finished products. Our standard products are finished (polished, coated) parts.
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