Overview
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Lithium Niobate (LiNbO3)
Lithium niobate is a ferroelectric material with excellent electro-optic, nonlinear, and piezoelectric properties. It is one of the most thoroughly characterized electro-optic materials, and Inrad’s crystal growing techniques consistently produce large lithium niobate crystals of exceptional quality.
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A robust crystal, lithium niobate is often used for military Q-switching applications.
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One of the most versatile nonlinear crystals, lithium niobate has a wide range of applications, including:
- Optical modulation and Q-switching. Thanks to its large electro-optic coefficients, lithium niobate is well suited to optical modulation and Q-switching of infrared wavelengths. Among its advantages in these applications are:
- Zero residual birefringence
- Transverse electric field to direction of light propagation
- Nonhygroscopic
- Low half-wave
- Second harmonic generation, particularly with low power laser diodes in the 1.3 to 1.55 µm range.
- Optical parametric oscillation. With its high nonlinear coefficients, lithium niobate is an efficient medium for optical parametric oscillation.
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- Phasematching.To generate tunable wavelengths over a broad wavelength range, lithium niobate phasematching processes offer:
- Broad spectral transmission ranging from 0.4 µm to 5.0 µm with an OH- absorption at 2.87 µm
- Large negative birefringence
- Large nonlinear coefficients
- Difference frequency mixing. Lithium niobate generates tunable infrared wavelengths through a difference frequency mixing process.Typical powers for 10 nanosecond pulses and 5-mm beams are:
- 30 mJ/pulse of 0.640 µm minus 40 mJ/pulse of 1.064 µm to produce 2.5 mJ/pulse at 1.54 µm
- 32 mJ/pulse of 0.532 µm minus 32 mJ/pulse of 0.640 µm to produce 0.25 mJ/pulse at 3.42 µm
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Inhouse crystal growth
All lithium niobate crystal growth, orientation, fabrication, polishing, and testing is performed at our Northvale, NJ facility, ensuring complete traceability and satisfaction with every single crystal. We produce optical grade lithium niobate in a variety of configurations. Standard cuts are available as OPO crystals, Q-switch elements, difference frequency mixing crystals and autocorrelation crystals.
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Sizes
LiNbO3 Single Crystals
| Size (mm) |
Corresponding INRAD Cells |
Notes |
10 x 10 x 0.5
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530-081
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autocorrelation
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10 x 10 x 1.0
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530-081
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autocorrelation
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10 x 10 x 5
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530-080LD
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autocorrelation
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10 x 10 x 30
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usually not mounted
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OPO size
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9 x 9 x 25**
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PLC01-DC08
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Q Switch size
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13.3 x 18.5 x 30
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563-1117
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Autotracker size
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**The standard 9 x 9 x 25 mm crystal is z-cut, gold electroded, and ar-coated for 1064 nm.
All other crystals typically are uncoated
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Orientations
LiNbO3 Standard Orientations*
| Designation |
Angle θ |
Operation |
Input |
Output |
| “A” |
68.8° |
DFM |
(564-600 nm) - 1064 nm |
1200-1380 nm
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| “B" |
59.8º |
DFM |
(600-664 nm) - 1064 nm
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1370-1770 nm |
| 46.8º |
SHG |
1310 nm |
655 nm |
| “C” |
50.8º |
DFM |
(664-923 nm) - 1064 nm |
1770-4000 nm |
| SHG |
1550 nm |
775 nm |
| “D” |
47º |
DFM |
1064 - (1450-2000 nm) |
2300-4000 nm |
| “OPO” |
47º |
OPO |
1064 nm
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1450-4000 nm |
| “QS” |
Z |
Q-switch
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— |
— |
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*Orientations refer to the angles between the beam propagation direction and the crystallographic direction of the optic axis. All of the frequency-mixing orientations that are listed here are Type I, meaning that:
- Polarization directions of the two longest wavelengths in the mixing process are in the same direction
- The shortest wavelength in the mixing process has an orthogonal polarization direction
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Design Notes
When working with lithium niobate crystals, keep the following optical design considerations in mind:
- Avoid piezoelectric ringing. Because piezoelectric ringing can be severe, piezoelectrically damped designs can be very useful.
- Coatings raise damage threshold. The damage threshold of the intrinsic material at 1.06 microns with a 10 nsec 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.
- Account for lower efficiencies. Difference frequency mixing using lithium niobate offers lower efficiencies than second harmonic generation with KDP or BBO. One reason for the efficiency losses is that the lithium niobate crystal can tolerate a relatively low peak power of 40 MW/cm2.
