Barium Metaborate，β-BBO - Beta-Barium Borate，Beta barium borate(BBO) crystal

Product Information

Alpha-Barium Borate (barium metaborate) is a nonlinear crystalline solid used in photo optic applications. Barium borate (BBO) is a nonhydroscopic and chemically stable material. Crystallization takes place in two phases, alpha and beta, and the phase transition temperature equals 925±5°C. The higher temperature phase-alpha is centric symmetrical within its crystal structure, whose square nonlinearity tensor components are identically equal to zero. In contrast to the alpha-phase, the Beta-phase of BBO is non-centric symmetrical and the crystals grown in this phase possess nonlinear optical properties. Beta barium borate(BBO) crystal is one of the best non-linear optical crystals with high effective nonlinear optical coefficient, high damage threshold, wide phase matching range and high deep UV transmittance.

BBO crystal has a very wide light transmission range, a very low absorption coefficient, and a weak piezoelectric ringing effect. Compared with other electro-optic modulation crystals, it has higher extinction ratio, larger phase matching angle, higher light damage threshold, broadband temperature matching and excellent optical uniformity. These characteristics are beneficial to improve the stability of laser output power, especially for the frequency triple of Nd:YAG crystal  laser, which has a wide range of applications.

The transmittance band of BBO crystal is 189 – 3500 nm. It can be widely used in neodymium-dropd laser for double frequency (SHG), triple frequency (THG), quadruple frequency (FHG) and even fivefold frequency (5HG to 213 nm), as well as laser parametric oscillation (OPO) and parametric amplification (OPA). BBO crystal cut along the Z axis are also excellent electro-optic modulation crystals. The laser damage threshold of BBO crystal is 13.5GW/cm2@1064 nm 1ns pulse width 10Hz heavy frequency, and the effective double frequency coefficient is about 6 times that of KDP crystal.

BBO nonlinear crystal is a negative uniaxial crystal, which provides phase matching for various second-order interactions almost over its entire transparency range (from 185 nm to 3.3 µm, as deduced from the transmittance measurements using crystal samples of several mm thickness), making it a widely used crystal for nonlinear frequency conversion in the ultraviolet, visible and near-infrared. In that regard, BBO crystal is the most important nonlinear crystal for near infrared optical parametric chirped pulse amplifiers, which currently deliver few optical cycle pulses with high average and ultrahigh peak powers.

BBO was selected as frequency doubling crystal for Its good transmittance in 532nm and 1064nm and second-order nonlinear optical susceptibility. BBO change Yb:YAG laser into 532nm laser. harmonic separator is coated with 1064nm high transmittance films and 532nm high-reflective film strengthening the oscillation.

Synonyms

BBO optical crystals; Barium metaborate; Beta barium borate; Barium boron oxide; Barium diborate; Barium diboron tetraoxide; barium(+2) oxido-oxo-borane; β-BaB2O4; BaB2O4; boric acid barium salt

BBO Specification

Size：customized
       •   Dimension tolerance: (W±0.1mm)x(H±0.1mm)x(L+0.5/-0.1mm)  (L≥2.5mm)
                                               (W±0.1mm)x(H±0.1mm)x(L+0.1/-0.1mm)  (L<2.5mm)
      •   Clear aperture: central 90% of the diameter
      •   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:≤0.2mm x 45°
      •   Chip: ≤0.1mm
      •   Scratch/Dig code: better than 10/ 5 to MIL-PRF-13830B
      •   Parallelism: ≤20 arc seconds
      •   Perpendicularity: ≤5 arc minutes
      •   Angle tolerance: ≤0.25
      •   Damage threshold[GW/cm2]: >1   for 1064nm, TEM00, 10ns, 10HZ (polished only)
                                                            >0.5 for 1064nm, TEM00, 10ns, 10HZ (AR-coated)
                                                            >0.3 for 532nm,  TEM00, 10ns, 10HZ (AR-coated)
   •   Quality Warranty Period: one year under proper use.

Per your request or drawing

We can customized as required
      •   BBO has a low susceptibility to the moisture. Users are advised to provide dry conditions for both application and preservation of BBO.
      •   BBO is relatively soft and therefore requires precautions to protect its polished surfaces.
      •   When angle adjusting is necessary, please keep in mind that the acceptance angle of BBO is small.
      •   ATT engineers can select and design the best crystal, based on the main parameters of your laser, such as energy per pulse, pulse width and repetition rate for a pulsed laser, power for a cw laser, laser beam diameter, mode condition,divergence, wavelength tuning range, etc.
      •   For thin crystals, ATT can provide free holders for you.

Properties（Theoretical）

Optical and Nonlinear Optical Properties

BBO is featured by
      •   Broad phase matchable range from 409.6 nm to 3500 nm;
      •   Wide transmission region from 190 nm to 3500 nm;

  High damage threshold;
      •   High optical homogeneity with δn ≈10-6/cm;

      •   Large effective second-harmonic-generation (SHG) coefficient about 6 times greater than that of KDP  crystal;
          •   Wide temperature-bandwidth of about 55℃.

AR-coatings for BBO
      •   Dual Band AR-coating (DBAR) of BBO for SHG of 1064nm;

             low reflectance (R<0.2% at 1064nm and R<0.5% at 532nm );

             high damage threshold (>300MW/cm2 at both wavelengths);

             long durability.

      •   Broad Band AR-coating (BBAR) of BBO for SHG of tunable lasers.

      •   Broad Band P-coating of BBO for OPO applications.

      •   Other coatings are available upon request.

Applications of BBO

Second, third, fourth and fifth harmonic generation of Nd:YAG and Nd:YLF lasers

Frequency-doubling, -tripling and -mixing of Dye lasers

Second, third and fourth harmonic generation of Ti: Sapphire and Alexandrite lasers

Optical parametric amplifier (OPA) and optical parametric oscillators (OPO)

Frequency-doubling of Argon ion, Cu-vapor and Ruby lasers.

Electro-optic crystals for Pockels cells

266nm laser for material processing

532nm laser formedical field

Application in Nd:YAG Lasers： 
BBO is an efficient NLO crystal for the second, third and fourth harmonic generation of Nd:YAG  lasers, and the best NLO crystal for the fifth harmonic generation at 213nm. Conversion efficiencies of more than 70% for SHG, 60% for THG and 50% for 4HG, and 200 mW output at 213 nm (5HG) have been obtained, respectively.
BBO is also an efficient crystal for the intracavity SHG of high power Nd:YAG lasers. For the intracavity SHG of an acousto-optic Q-switched Nd:YAG laser, more than 15 W average power at 532 nm was generated in a  AR-coated BBO crystal. When it is pumped by the 600 mW SHG output of a mode-locked Nd:YLF laser, 66 mW output at 263 nm was produced from a Brewster-angle-cut BBO in an external enhanced resonant cavity.
Because of a small acceptance angle and large walk-off, good laser beam quality (small divergence, good mode condition, etc.) is the key for BBO to obtain high conversion efficiency. Tightly focusing of laser beam is not recommended

Applications in Tunable Lasers
1. Dye lasers
Efficient UV output (205nm - 310 nm) with a SHG efficiency of over 10% at wavelength of ≥206 nm was obtained in type I BBO, and 36% conversion efficiency was achieved for a XeCl-laser pumped Dye laser with power 150KW which is about 4-6 times higher than that in ADP. The shortest SHG wavelength of 204.97 nm with efficiency of about 1% has been generated.
BBO is widely used in the Dye lasers. With type I sum-frequency of 780 - 950 nm and 248.5 nm (SHG output of 495 nm dye laser) in BBO, the shortest UV outputs ranging from 188.9nm to 197 nm and the pulse energy of  95 mJ at 193 nm and 8 mJ at 189 nm have been obtained, respectively.
2. Ultrafast Pulse Laser

Frequency-doubling and -tripling of ultrashort-pulse lasers are the applications in which BBO shows superior properties to KDP and ADP crystals. Now, ATT can provide as thin as 0.005mm BBO for this purpose. A laser pulse as short as 10 fs can be efficiently frequency-doubled with a thin BBO, in terms of both phase-velocity and group-velocity matching.
3. Ti:Sapphire and Alexandrite lasers
UV output in the region 360nm - 390 nm with pulse energy of 105 mJ (31% SHG efficiency) at 378 nm, and output in the region 244nm - 259 nm with 7.5 mJ (24% mixing efficiency) have been obtained for type I SHG and THG of an Alexandrite laser in BBO crystal.

More than 50% of SHG conversion efficiency in a Ti:Sapphire laser has been obtained. High conversion efficiencies have been also obtained for the THG and FHG of Ti:Sapphire lasers.

4.  Argon Ion and Copper-Vapor lasers
By employing the intracavity frequency-doubling technique in an Argon Ion laser with all lines output power of 2W, maximum 33 mW at 250.4 nm and thirty-six lines of deep UV wavelengths ranging from 228.9 nm to 257.2 nm were generated in a Brewster-angle-cut BBO crystal.
Up to 230 mW average power in the UV at 255.3 nm with maximum 8.9% conversion efficiency was achieved for the SHG of a Copper-Vapor laser at 510.6 nm.

BBO's OPO and OPA Applications

The OPO and OPA of BBO are powerful tools for generating a widely tunable coherent radiation from the UV to IR. The tuning angles of type I and type II BBO OPO and OPA have been calculated.

1. OPO pumped at 532 nm
An OPO output ranging from 680 nm to 2400 nm with the peak power of 1.6MW and up to 30% energy conversion efficiency was obtained in a 7.2 mm long type I BBO. The input pump energy was 40 mJ at 532 nm with pulse-width 75ps. With a longer crystal, higher conversion efficiency is expected.

 2. OPO and OPA pumped at 355 nm

In the case of Nd:YAG pumping, BBO's OPOs can generate more than 100mJ, with wavelength tunable from 400nm to 2000nm. Using BBO crystal, the OPO system covers a tuning range from 400nm to 3100nm which guarantees a maximum of 30% and more than 18% conversion efficiency, over the wavelength range from 430nm to 2000nm.Type II BBO can be used to decrease linewidth near the degenerate points. A linewidth as narrow as 0.05 nm and usable conversion efficiency of 12% were obtained. However, a longer (> 15mm) BBO should normally be used to decrease the oscillation threshold when employing the type II phase-matching scheme.
Pumping with a picosecond Nd:YAG at 355 nm, a narrow-band (< 0.3 nm), high energy (> 200μJ) and wide tunable (400 nm to 2000 nm) pulse has been produced by BBO's OPAs. This OPA can reach as high as more than 50% conversion efficiency, and therefore is superior to common Dye lasers in many respects, including efficiency, tunable range, maintenance, and easiness in design and operation. Furthermore, coherent radiation from 205 nm to 3500 nm can be also generated by BBO's OPO or OPA plus a BBO for SHG.

3. Others

A tunable OPO with signal wavelengths between 422nm and 477nm has been generated by angle tuning in a type ⅠBBO crystal pumped with a XeCl excimer laser at 308 nm. And a BBO's OPO pumped by the fourth harmonic of a Nd:YAG laser (at 266 nm) has been observed to cover the whole range of output wavelengths 330 nm - 1370 nm.

When pumped by a 1mJ, 80 fs Dye laser at 615 nm, the OPA with two BBO crystals yields more than 50μJ (maximum 130 μJ), < 200 fs ultrashort pulse, over 800 nm - 2000 nm.

BBO's E-O Applications 

BBO can also be used for E-O applications. It has wide transmission range from UV to about 3500nm. And it has much higher damage threshold than KD*P or LiNbO3. More than 80W output power and 50KHz repitition rate have been reached by using ATT's E-O BBO crystals and Nd:YVO4 crystals as gain media. At 5KHz, its pulse has width as short as 6.4ns, and energy of 5.7 mJ or peak power of 900 KW. It has advantages over the commercial A-O Q-switched one, including a very short pulse, high beam quality and size compact as well. Although it has a relative small electro-optic coefficient, and its half-wave voltage is high(7KV at 1064nm, 3x3x20mm3), long and thin BBO can reduce the voltage requirements. ATT now can supply  25mm long and 1mm thin high optical quality of BBO crystal with Z-cut, AR-coated and Gold/Chrome plated on the side faces.

Packing of BBO

Standard Packing:

Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 440 gallon liquid totes Special package is available on request.

ATTs’ BBO is carefully handled to minimize damage during storage and transportation and to preserve the quality of our products in their original condition

Chemical Identifiers