Lithium Niobate - LiNbO3 Crystal Material
LiNbO3 crystal combines low cost, good mechanical and physical properties as well as high optical homogeneity. Therefore, LiNbO3 wedges have been widely used in fiber isolators and circulators.
LiNbO3 (Lithium niobate, LN) crystal is a negative uniaxial crystal and one of the most thoroughly characterized optical materials. With its wide transparency range in the visible and mid-infradred and the excellent chemical and mechanical stability, LN crystal can be used as a bifrengent material for applications in infrared.
With its large electro-optic coefficients, wide optical transparency window, and availability of high optical quality crystals, LN (lithium niobate) crystal is often the material of choice for optical modulation and Q-switch at near-infrared and infrared wavelengths. For electro-optic modulators (EOM) the crystal can be z-cut with zero residual birefringence along the direction of light propagation or x-cut with non-zero residual birefringence and the maximized effective electro-optic coefficient. For Q-switch the crystal is typically z-cut with zero residual birefringence and an electric field is applied transverse to the direction of light propagation. The piezoelectric ringing in LN is a disadvantage at high repetition frequency, but can be overcome to some extent with proper piezoelectrically damped designs.
Both pure LN and MgO doped LN (MgO:LN) crystals with gold coatings on side faces for electrodes are available
b.Crystro's GGG wafer is grown by Czochralski method.Max diameter reach 4inch,it's now the biggest size in this filed,we can custom size and specs ,rougness<0.5nm.Magneto-optical single crystals like GGG,SGGG,TGG,TSAG are our main products.
c.Anhui Crystro participate in the kinds exhibitions every year: Laser World of Photonics Munich, Shanghai, Photonics West in San Francisco, CIOE in Shenzhen, etc.
Crystro provides:
- LiNbO3 wedges used for fiber optical isolators and circulators.
- Reliable delivery
- Strict quality control
- Technical support
- Very competitive prices
Basic Properties of LiNbO3
| Crystal Sturucture | Trigonal, Space group R3c, Point group 3m |
| Melting Point | 1253℃ |
| Mohs Hardness | 5 |
| Density | 4.64g/cm3 |
| Deliquescence | None |
| Optical Homogeneity | ~5x10-5/cm |
| Transparency Range | 420-5200nm |
| Absorption Coefficient | ~0.1%/cm @1064nm |
| Refractive Indices at 1064nm | ne=2.146, no=2.220@1300nm ne=2.156, no=2.232@1064nm ne=2.203, no=2.286@632.8nm |
| Thermal Expansion Coefficients (at 25℃ ) | //a,2.0x10-6/K //a,2.2x10-6/K |
| Thermal Conductivity Coefficients | 38 W/m/K at 25℃ |
| Thermal Optical Coefficients | dno/dT=-0.874 x 10-6/K at 1.4μm dne/dT=39.073 x 10-6/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)-0.02195λ2 |
Specifications of LiNbO3 wedges
| Aperture | 1.0 x1.0 mm2 to 4 x 4 mm2 |
| Dimension Tolerance | ±0.05mm |
| Wedge Angle Tolerance | ±0.1° |
| Optical Axis Orientation | ±0.5° |
| Flatness | λ/4 @632.8nm |
| Surface Quality | 20-10 |
| AR-Coating | R＜0.2% @1550nm±40nm |
| Standard Size | 1.25mmx1.25mmx0.5mm with 13º or 15º wedge, phi=22.5º |
Note: Other sizes and coatings are available upon request.
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, |
| Photorefractive Damage Threshold | 50 MW/cm2 (10 ns, 1064 nm) |
| Surface Damage Threshold | 300 MW/cm2 (10 ns, 1064 nm)
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Specifications of LN EO components:
| Wavefront Distortion: | Less than λ/8 @ 633 nm |
| Dimension Tolerance: | (W+/-0.1 mm) x (H+/-0.1 mm) x (L+0.5/-0.1 mm) |
| Clear Aperture: | > 90% central area |
| Flatness: | λ/8 @ 633 nm |
| Surface Quality: | Scratch/Dig 10/5 per MIL-O-13830A |
| Parallelism: | better than 20 arc seconds |
| Perpendicularity: | 5 arc minutes |
| Angle Tolerance: | Δθ < 0.5o, Δφ < 0.5o |
LiNbO3 is also widely used as electro-optic modulators and O-switches for Nd: YAG, Nd: YLF and Ti:Sapphire lasers as well as modulators for fiber optics. The following table list the specifications of a typical LiNbO3 crystal used as Q-switch with transverse E-O modulation. The light propagates in z-axis. The electro-optic coefficients of LiNbO3 are: r33= 32 pm/V, r31= 10 pm/V, r22= 6.8 pm/V at at low frequency and r33= 31 pm/V, r31= 8.6 pm/V, r22= 3.4 pm/V at high electric frequency. The halfwave voltage: Vπ=λd/no3γc1, γc=(ne/no)3γ33-γ13.
LiNbO3 Q-switch Specifications
| Size | 9 X 9 X25 mm3 or 4 X 4 X 15 mm3 |
| Other size is available upon request |
| Tolerance of Size | Z-axis: ± 0.2mm |
| X-axis and Y-axis: ± 0.1mm |
| Chanfer | less than 0.5 mm at |
| Accuracy of Orientation | Z-axis: ＜ ±5′,X-axis and Y-axis: ＜ ±10′ |
| Parallelism | ＜20′′ |
| Finish | 10/5 scratch/dig |
| Flatness | λ/8 at 633nm |
| AR-Coating | R＜0.2% @1064nm |
| Electrodes | Gold/Chrome plated on X-faces |
| Wavefront Distortion | ＜λ/4 @633nm |
| Extinction Ratio | ＞400:1 @633nm, φ 6mm beam |
LiNbO3 is also a good acousto-optic crystal and used for surface acoustic wave (SAW) wafer and A-O modulators. Crystro provides acoustic (SAW) grade LiNbO3 crystals in wafers, as-cut boules, finished components and custom fabricated elements.
Typical SAW Properties
| Cut Type | SAW Velocity Vs (m/s) | Electromechanical Coupling Factor K2s(%) | Temperature Coefficient of Velocity TCV (10-6/℃) | Temperature Coefficient of Delay TCD (10-6/℃) |
| 127.86 ° Y-X | 3970 | 5.5 | -60 | 78 |
| Y-X | 3485 | 4.3 | -85 | 95 |
Typical Specifications
| Specifications | Boule | Wafer |
| Diameter | Φ3'' | Φ4'' | Φ3'' | Φ4'' |
| Length or Thickness (mm) | ≤100 | ≤50 | 0.35-0.5 |
| Orientation | 127.86°Y,64°Y,135°Y,X,Y,Z, and other cut |
| Ref.Flat Orientation | X,Y |
| Ref.Flat Length | 22±2mm | 32±2mm | 22±2mm | 32±2mm |
| Front Side polishing | / | Mirror polished 5-15 Å |
| Back Side Lapping | / | 0.3-1.0μm |
| Flatness (μm) | / | ≤15 |
| Bow (μm) | / | ≤25 |
Crystro can offer other size and specification of wafers upon request.
| Crystal Structure | Trigonal, Space group R3C, Point group 3m |
| Cell Parameters | a=5.148 Å , c=13.863 Å |
| Melting Point | 1253oC |
| Curie Temperature | 1140oC |
| Mohs Hardness | 5 |
| Density: | 4.64 g/cm3 |
| Deliquescence | None |
| Optical Homogeneity | ~ 5x10-5 /cm |
| Transparency Range | 420 -- 5200 nm |
| Absorption Coefficient | ~0.1%/cm @ 1064 nm |
Refractive indices at 1064nm
(Pure LN) | 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 1.4 µm
dne/dT=39.073x10-6/K at 1.4 µm |
The Sellmeier equations (Pure LN))
(λ in µm) | no2 = 4.9048+0.11768/(λ2-0.04750)-0.027169λ2
ne2 = 4.5820+0.099169/(λ2-0.04443)-0.021950λ2
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MgO doped LiNbO3 (MgO:LN) has similar linear optical properties to pure LiNbO3, but the photorefractive damage threshold is much higher.
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LN LiNbO3 Single Crystal Images
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