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LBO's high damage threshold,wide acceptance angle, good thermal stability and wide transmission range make it ideal for frequency doubling of high power lasers. The shortest phase matchable wavelength fo direct SHG is 554 nm. It promises to become the preferred crystal for frequency doubling or tripling of high power Nd:YAG and Nd:YLF lasers. It is also frequently used for SHG of Ti:Sapphire, Alexandrite, Cr:LiSAF lasers and diode pumped Nd doped lasers. Other well known applications using LBO include OPO and OPA pumped by Eximer lasers and the harmonics of Nd:YAG lasers.
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Broad transparency range from 160nm to 2600nm (SHG range from 0.55µm to 2.6µm). |
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High optical homogeneity (Dn»10-6/cm) and inclusion free. |
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Relatively large effective SHG coefficient - about 3x that of KDP. |
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Wide acceptance angle and small walk-off. |
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No walk-off and maximum effective coefficient using non-critical phase-matching. |
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High damage threshold - 18.9GW/cm2 for a 1.3ns laser at 1.054µm. |
Physical properties |
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| Crystal structure/point group | orthorhombic/mm2 |
| Lattice parameters | a=0.8447nm, b=0.7379nm, c=0.5140nm, Z=2 |
| Melting point | 834ºC (decomposition) |
| Density | 2.47 g.cm-3 |
| Mohs hardness | ~6 |
| Absorption coefficient | <0.1%/cm @ 1.64 µm |
| Thermal expansion coefficient | ax= 10.8´10-5/K ay= -8.8´10-5/K az= 3.4´10-5/K |
Optical properties |
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| Transmission range | 160 - 3200 nm | ||||||||||||
| Nonlinear optical coefficient | 3 x 10-9 e.s.u.(effective SHG coefficient ~3 x KDP) | ||||||||||||
| Acceptance angle | 25 mrad (95 mrad at q=90o) | ||||||||||||
| Damage threshold | 25 GW cm-2 (1064 nm, 0.1 ns) | ||||||||||||
| Dimensions | As large as 20 x 20 x 20 mm and thickness <0.1 mm are available | ||||||||||||
| Refractive indices |
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| Sellmeier equations:(in µm) | nx2= 2.45316 + 0.01150/(l2-0.01058)- 0.01123l2 ny2= 2.53969 + 0.01249/(l2-0.01339)- 0.02029l2 nz2= 2.58515 + 0.01412/(l2-0.00467)- 0.01850l2 |
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LBO is a negative biaxial crystal with the principle axes x, y and z (nz>ny>nx) parallel to the crystallographic axes a, c and b respectively.
Finished Quality Indications |
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| End faces flatness (transmitting | <l/8 @633nm |
| wavefront distortion also) | |
| Scratch/Dig | 10/5 to MIL-0-13830A |
| Clear aperture | >90% of central area. No visible scattering |
| paths or centres are seen using a 30mW | |
| He-Ne laser. | |
| Dimension tolerance | W±0.1mm x H±0.1mm x L+0.2/-0.1mm |
| Parallelism | better than 20 arc seconds |
| Perpendicularity | arc minutes |
| Angular tolerance | Dq< ±0.5o, Df< ±0.5o |
| Damage threshold | 15 GW/cm2 for a single mode 1.3ns |
| 1 Hz laser at 1.064µm | |
| 1 GW/cm2 for a cw, mode-locked laser at | |
| 1.064µm | |
The crystals are guaranteed to the above specification.
The LBO may be provided with AR-coatings or cut with Brewster's angle faces for intra-cavity use. Mounts are also available.
Users are advised to store and use LBO in dry conditions as LBO is slightly hygroscopic. Care must be taken to protect the polished surface of LBO from scratching and dust. If necessary cleaning can be achieved with soft silk dampened with pure organic solvents such as 50:50 alcohol and ether.