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. 

Shanghai North Optics 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 

• They are the best choice for high repetition rate Q-switching:

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.

•  High damage threshold and power handling capability:

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).

•  Wide Transmission range from UV to NIR:

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. 

•  Low Absortion and piezoelectric ringing:

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.

• Relatively high half wave voltage:

BBO has a comparatively small electro-optic coefficient, and hence high applying voltage.North Optics 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:

• BBO crystals are hydroscopic and therefore it is recommended to preserve and use them in dry environment.
• Precautions need to be taken to protect its polished surfaces since BBO is comparatively vulnerable.
• The acceptance angle of BBO is small, so be careful when it comes to adjusting angles.
• Shanghai North Optics engineers can offer you the best suitable and high quality crystal according to the characteristics of your lasers. The parameters we take into concern include pulse width , energy per pulse, repetition rate for a pulsed laser, power for a cw laser, divergence, laser beam diameter, wavelength tuning range, mode condition, etc.

Specifications:

Physical properties of BBO:

Optical properties of BBO:

Features of BBO crystal：

• Ultra-thin crystals can be used for ultra-fast (<10 fs) applications
• Wide phase matching range of various second-order nonlinear interactions in almost the entire transparent range
• The highest nonlinearity among all UV nonlinear crystals
• High laser induced damage threshold (LIDT)
• Wide transmittance range from 188 nm to 5.2μm (appropriate transparency @3μm-5.2μm, tens of μm thick crystal)
• Extremely low capacitance (1< pF) will permit high repetition rate switching with rise times on the order of 100 ps or less
• High damage threshold capable of withstanding high peak power intensities of samller beam size and therefore suitable for compact design ( However, small crystal aperture leads to diffraction losses and hence might increase the insertion losses.)
• Not prone to piezo-electric ringing
• Low absorption and associated laser-induced thermal birefringence
• High extinction ratio

Applications:

1. High repetition rate DPSS Q-switches
2. High repetition rate regenerative amplifier control
3. Cavity dumping and Beam chopper
4. Low dispersion suitable for short pulse regenerative amplifiers

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