LiNbO3 crystal has been widely used in optical waveguide and optical communication technology because of its excellent electro-optical properties. It is an ideal substrate material for many integrated optoelectronic devices. Because of the large electro-optic coefficient of LiNbO3, the half-wave voltage is low. The electro-optic effect of LiNbO3 crystal is usually used to modulate the optical signal. Electro-optic modulation is divided into longitudinal and transverse, and LiNbO3 is mainly used in transverse modulation. It has been widely used in medium and low power solid-state lasers.
Physical and optical properties
| Chemical formula | LiNbO3 |
| Crystal structure | trigonal |
| Space group | R3C |
| Density | 4.64 g/cm3 |
| Mohs hardness | 5 |
| Optical homogeneity | ~ 5 x 10-5 / cm |
| Transparency range | 420 – 5200 nm |
| Absorption coefficient | ~ 0.1 % / cm @ 1064 nm |
| Refractive indices at 1064 nm | 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 | |
| Sellmeier equations (λ, μm) | no2 = 4.9048 + 0.11768 / (λ2 – 0.04750) – 0.027169λ2 |
| ne2 = 4.5820 + 0.099169 / (λ2 – 0.04443) – 0.021950λ2 | |
| Thermal expansion coefficient @ 25 °C | //a, 2.0 x 10-6 / K |
| //c, 2.2 x 10-6 / K | |
| Thermal conductivity | ~ 5 W/m/K @ 25 °C |
| Thermal optical coefficient | dno/dT = -0.874 x 10-6 / K at 1.4 µm |
| dne/dT = 39.073 x 10-6 / K at 1.4 µm |
LiNbO3 General specification for Q-Switch
| Refractive retardation | Γ=лLnr22V/λd |
| Electro-optic coefficients | R33=32pm/V |
| R31=10pm/V | |
| R22=6.8 pm/V | |
| Aperture | 4x4mm ~ 9x9mm |
| Length | 15~25mm |
| Tolerance of size | +/-0.1mm |
| Chamfer | <0.5mm x 45° |
| Accuracy of orientation | <5 arc min |
| Parallelism | <10 arc sec |
| Flatness | l/8 at 632.8 nm |
| Wavefront Distortion | <l/4 at 632.8 nm |
| Extinction Ratio | >400:1 @ 633nm, dia 6mm beam |
LiNbO3 specification for Optical waveguide
| Operating wavelength range | 1.525-1.605μm |
| Extinction ratio | ＜20dB |
| Half wave voltage | ＜6V |
| DC bias voltage | ＜8V |
| Input characteristic impedance | 50Ω |
| Light reflection | ≤-50dB |
| Maximum input electric power | 20dBm |
| Maximum input optical power | 10-100mW |
| Storage temperature | -40-85℃ |
| Operating temperature | -40-70℃ |
| Elastic stiffness coefficient cij/(1010N/m2) | c11 | c12 | c13 | c14 | c33 | c44 |
| 20.3 | 5.3 | 7.5 | 0.9 | 24.5 | 6.0 | |
| Elastic compliance coefficient sij/(10-12m2/N) | S11 | S12 | S13 | S14 | S33 | S44 |
| 5.78 | -1.01 | -1.47 | -1.02 | 5.02 | 17.0 | |
| piezoelectric strain constant dij/(10-11C/N) | d11 | d15 | d22 | d31 | d33 | |
| 8 | 7.4 | 2.04 | -0.086 | 1.62 | ||
| dielectric constant | εT11/ε0 | εT11/ε0 | ||||
| 78 | 32 | |||||
| Electromechanical coupling coefficient kij(%) | k15 | k31 | ||||
| 68 | 50 |
| NLO Coefficients | d33 = 34.4 pm/V |
| d31 = d15 = 5.95 pm/V | |
| d22 = 3.07 pm/V | |
| Efficiency NLO Coefficients | deff =5.7 pm/V or ~14.6 x d36 (KDP) for frequency doubling 1300 nm; |
| deff =5.3 pm/V or ~13.6 x d36 (KDP) for OPO pumped at 1064 nm; | |
| deff =17.6 pm/V or ~45 x d36 (KDP) 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 Electrical field||z, light ^z: Electrical field||x or y, light||z: | 3.03 KV |
| 4.02 KV | |
| Damage Threshold | 100 MW/cm2 (10 ns, 1064nm) |
Standard Specifications of laser grade LiNbO3 crystals
| Transmitted wavefront distortion | better than l/4 @ 633nm |
| Dimension tolerance | (W±0.1mm) x (H±0.1mm) x (L±0.2mm) |
| Clear aperture | over 90% central diameter |
| Flatness | l/8 @ 633nm |
| Surface quality | 20 /10 Scratch/Dig |
| Parallelism | better than 20 arc sec |
| Perpendicularity | 5 arc min |
| Angle tolerance | Dq < 0.5o, Df < 0.5o |
| AR-coating | dual wave band AR coating at 1064/532 nm on both surfaces, with R < 0.2% at 1064 nm and R < 0.5% at 0.532 nm per surface |
wide transparency range
High electro-optic efficiency
Stable mechanical and chemical properties
Low absorption loss
low damage threshold
Small volume
Not easy to deliquesce
High temperature stability
Large electro-optic coefficient
Easy to grow into large crystal
Optical Communication
Holography
Medical Applications
Pulse range finder
Laser target indicator
Electro-optic Q-switch