Beta BBO crystals or beta barium borate crystals exhibit significant advantages over other materials in terms of laser power handling abilities, high damage threshold temperature stability, and substantial freedom from piezoelectric ringing. Beta BBO crystals are the most attractive candidates for high repetition rate Q-switching, pulse picking at up to 3 MHz, laser cavity dumping, regenerative amplifier control, and beam chopper. Beta barium borate (BBO) crystal is an excellent electro-optic crystal for high-power applications at the wavelength range from 200nm to 2,500nm.
Hangzhou Shalom EO offers BBO crystals used in the pockels cells with high precision polishing, AR coating, and Cr-Au electrodes at and competitive price. Stocked crystals of standard specifications are ready for selection, and customized special crystals are available upon the customer's request. Besides, we also offer BBO pockels cells.
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Fig.1 Transparency Curve of BBO
Because it relies on the electro-optical effect, switching time - aided by the low capacitance of the Electro-Optical Q Switch is very fast, therefore it has surpassing performance for high repetition rate lasers up to 1MHz. All-solid-state short-cavity Q-switched laser using BBO electro-optic Q-switch can generate high-energy laser with a pulse width of less than 4ns.
Without water cooling, the BBO electro-optical Q switch can be turned off and withstand up to 150W intracavity oscillation optical power (laser output power up to 50W).
BBO crystals has a wide transparency range of 189nm to 3500nm, which allows it to be used in diverse applications from UV to NIR spectrum.
Comparing to LiNbo3, BBO crystals are much less impaired by piezoelectric when voltage is applied. The other important feature of BBO electro-optics is their very low absorption and associated laser-induced thermal birefringence. Due to the low absorption, very little optical heating will occur at operating wavelengths in the visible and near IR.
BBO has a comparatively small electro-optic coefficient, and hence high applying voltage.Shalom EO offers customized BBO crystals with required dimensions as well. Our panel of engineers could offer professional consultancy and help you ascertain the optimized solution for your need.
Cautions:
Specifications:
| Materials | Beta BBO crystals | Size Tolerance | L(±0.1mm)W(±0.1mm)H(+0.5/-0.1mm) |
| Cut Angle | Z-Cut | Clear Aperture | central 90% or the diameter |
| Scattering of Crystals | No visible scattering paths or centers when inspected by a 50mW green Laser | Flatness | less than λ/8 @ 633nm |
| Transmitting Wavefront Distortion | less than λ/8 @ 633nm | Chamfer | ≤0.2mmx45° |
| Chip | ≤0.1mm | Surface Quality | better than 10/5 S/D (MIL-PRF-13830B) |
| Parallelism | ≤20 arc seconds | Perpendicularity | ≤5 arc minutes |
| Angle Tolerance | ≤0.25° | Coating | AR/AR on both end surfaces Cr-Au electrode on two side surfaces |
| Quarter-wave voltage | TBA | Optical Transmission | >98% |
| Typical capacitance | 3pf | Damage Threshold | >500MW/cm^2 @1064nm, 10nS |
| Quality Warranty Period | one year under proper use |
Physical properties of BBO:
| Crystalline structure | Trigonal, space group R3c, Point group 3m | Cell Parameters | a = b = 12.532 Å, c = 12.717Å, Z = 6 |
| Melting point | 1095±5℃ | Phase transition point | 925±5℃ |
| Optical Homogeneity | δn ~ 10-6 /cm | Mohs hardness | 4 |
| Density | 3.85 g/cm3 | Specific heat | 1.91J/cm3 xK |
| Hydroscopicity | Low | Thermal expansion coefficients | a,4 x 10-6/K;c, 36x 10-6/K |
| Thermal Conductivity | ⊥c,1.2W/m/K; //c, 1.6W/m/K | Absorption Coefficient | < 0.1% /cm (at 1064 nm) |
Optical properties of BBO:
| Transparency Range | 189-3500 nm | Refractive Indices at 1064 nm at 800 nm at 532 nm at 400 nm at 266 nm |
no = 1.6545, ne = 1.5392 no = 1.6606, ne = 1.5444 no = 1.6742, ne = 1.5547 no = 1.6930, ne = 1.5679 no = 1.7585, ne = 1.6126 |
| Thermo-optic Coefficients |
dno/dT = -9.3 x 10-6 /°C dne/dT = -16.6 x 10-6 /°C |
Electro-optic Coefficients | γ11 = 2.7 pm/V, γ22, γ31 < 0.1 γ11 |
| Effective Nonlinearity Expressions | dooe= d31 sinθ +(d11 cos3φ - d22 sin3φ) cosθ deoe= (d11 sin3φ + d22 cos3φ) cos2θ |
Half-wave Voltage | 48 kV (at 1064 nm) |
| NLO Coefficients |
d11 = 5.8 x d36(KDP) d31 = 0.05 x d11 d22 < 0.05 x d11 |
Damage Threshold (Bulk) at 1064 nm at 532 nm |
5 GW/cm2 (10 ns); 10 GW/cm2 (1.3 ns) 1 GW/cm2 (10 ns); 7 GW/cm2 (250 ps) |
| Phase-matchable SH Wavelengths: | 189 - 1750 nm |
Features of BBO crystal：
Applications:
Fig.1 Qualitative comparison of acoustic ringing in BBO and LiNbO3
The intensity transmitted through the LiNbO3 Pockels cell varies greatly due to piezoelectric effects, whereas the light transmitted through the
BBO Pockels cell follows the decay of the applied high voltage pulse with no evident acoustic ringing
Application Notes:
Calculation of Quarter-wave Voltage
The voltage required to produce a retardance of π radians is called the halfwave voltage or simply Vπ. For an optical input linearly polarized 45o applying a halfwave voltage rotates the polarization by 90o. When the output wave is passed through a linear the resultant can be rapidly modulated from maximum intensity to minimum intensity by rapidly changing the voltage applied to the crystal from 0 volts to Vπ.
The halfwave voltage of BBO is dependent on the optical wavelength and is given by:
Where λ=optical wavelength
d=electrode spacing
L=optical path length
r22=electro-optic coefficients
no=ordinary indices of refraction
EO Q-Switch 1/4Wave Voltage Vs wavelength (3x3x20mm)
1/4 Wave Voltage @1030nm : Vπ/2 =3388V
