BBO crystal is excellent E-O material applied to high power laser system working at wavelength 200nm-2500nm. BBO can be used for Q-switching a CW diode pumped Nd:YAG laser when the crystal is Z-cut, with AR-coating and Au-electrodes for high power output. We can offer BBO crystals with the thickness less than 0.05 mm.

THATSHIGH's BBO is featured by：  

1.Broad phase matchable range from 409.6 nm to 3500 nm;
2.Wide transmission region from 190 nm to 3500 nm;
3.Large effective second-harmonic-generation (SHG) coefficient about 6 times greater than that of KDP crystal;
4.High damage threshold;
5.High optical homogeneity with dn » 10-6/cm;
6.Wide temperature-bandwidth of about 55°C.

THATSHIGH offers BBO of

1.Strict quality control;
2.Crystal length from 0.02mm to 25mm and size up to 15x15x15 mm3;
3.P-coatings, AR-coatings, mounts and re-polishing services;
4.A large quantity of crystals in stock

Basic Properties of BBO Crystal

Crystal Structure	Trigonal, space group R3c
Lattics Parameters	a=b=12.532Å, c=12.717Å
Melting Point	~1095℃
Mohs Hardness	4
Density	3.85 g·cm-3
Thermal Conductivity	1.2 W·m-1·K-1 (┴c) ; 1.6 W·m-1·K-1 (//c)

Optical and Nonlinear Optical Properties of BBO Crystal

Transparency Range	190nm-3500nm
SHG Phase Matchable Range	409.nm6-350 nm (Type I); 525nm-3500nm (Type II)
Therm-optic Coefficients [K-1]	dno/dT=-16.6×10-6; dne/dT=-9.3×10-6
Absorption Coefficients	<0.1%/cm @1064nm; <1%/cm @532nm
Angle Acceptance	0.8 mrad·cm-1      (θ, Type I, 1064 SHG)    1.27 mrad·cm-1    (θ, Type II, 1064 SHG)
Temperature Acceptance	55 ℃·cm-1
Spectral Acceptance	1.1 nm·cm-1
Walk-off Angle	2.7° (Type I, 1064 SHG); 3.2° (Type II, 1064 SHG)
NLO Coefficients	deff (I)=d31sinθ+(d11cosΦ-d22sin3Φ)cosθ deff (II)=(d11sin3Φ+d22cos3Φ)cos2θ
Non-vanished NLO Susceptibilities	d11=5.8×d36 (KDP); d31=0.05×d11; d22<0.05×d11
Sellmeier Equations (λ in μm )	no2=2.7359+0.01878 / (λ2-0.01822) -0.01354 λ2 ne2=2.3753+0.01224 / (λ2-0.01667) -0.01516 λ2
Electro-optic Coefficients	r22=2.7 pm/V
Half-wave Voltage	7 kV (@1064 nm, 3×3×20 mm3)
Resistivity	>1011 Ω·cm
Relative Dielectric Constant	εs11/εo:6.7; εs33/εo:8.1; Tan δ<0.001

THATSHIGH Specifications for BBO Crystal 

Dimension Tolerance	(W±0.1mm) ×(H±0.1mm) ×(L+0.5/-0.1mm) (L≥2.5mm)  (W±0.1mm) ×(H±0.1mm) ×(L+0.1/-0.1mm) (L<2.5mm)
Angle Tolerance	Δθ ≤ 0.25°  Δφ ≤ 0.25°
Clear Aperture	90% of central area
Chamfer	≤ 0.2mm @45°
Chip	≤ 0.1mm
Damage Threshold [GW/cm2 ]	> 1 TEM00, 10ns, 10HZ (uncoated) > 0.5 for 1064nm, TEM00, 10ns, 10HZ (AR-coated) > 0.3 for 532nm, TEM00, 10ns, 10HZ (AR-coated)
Flatness	< λ/8 @ 633nm
Parallelism	< 20"
Perpendicularity	≤ 5'
Surface Quality [S/D]	< 10/5
Wavefront Distortion	< λ/8 @ 633nm
Interior Quality	No visible scattering paths or centers [inspected by 50mW green laser]

　BBO is a negative uniaxial crystal,with ordinary refractive-index(no) larger than extraordinary refractive-index(ne).Both type I and type II phase-matching can be reached by angle-tuning.The phase matching angles of frequency doubling are shown in Fig.2.

                  

Figure 1.Transparency curve of BBO          Figure 2.SHG tuning curves of BBO

Application in Nd:YAG Lasers

BBO is an efficient NLO cyrstal 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 200mW 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 THATSHIGH AR-coated BBO crystal. When pumped by the 600 mW SHG output of a mode-locked Nd:YLF laser, 66 mW output at 266 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. Tight focus of laser beam is not recommended by THATSHIGH's engineers.

Applications in Tunable Lasers

1.Dye lasers
Efficient UV output (205nm-310nm) with a SHG efficiency of over 10% at wavelength of ≥206nm was obtained in type I BBO, and 36% conversion efficiency was achieved for a XeC1-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 in BBO.
THATSHIGH's 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 in BBO, 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, THATSHIGH can provide as thin as 0.01mm 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 -390nm with pulse energy of 105 mJ(31% SHG efficiency) at 378 nm, and output in the region 244nm-259nm 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 in BBO. High conversion efficienies have been also obtained in BBO 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 was generated in BBO 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

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, with the results shown in Fig.3and Fig.4, respectively.
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 532nm with pulse-width 75ps. With a longer BBO 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 THATSHIGH's 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 0.05nm 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 355nm, a narrow-band(<0.3nm), high energy (>200μJ) and wide tunable (400nm to 2000nm) 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.

　　　　　　　

Figure3.Type I OPO turning curves of BBO　　　Figure4. Type Ii OPO tuning curves of BBO

3.Others
　A tunable OPO with signal wavelengths between 422 nm and 477 nm has been generated by angle tuning in a type I BBO crystal 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 -1370nm.
　When pumped by a 1mJ, 80fs Dye laser at 615 nm,the OPA with two BBO crystal yields more than 50μJ (maximum 130μJ),<200fs ultrashort pulse, over 800 nm-2000 nm.

Coatings of BBO

THATSHIGH provides BBO with the following AR-coatings:
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 wqvelengths);
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.

THATSHIGH Warranty on BBO Specifications

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% or 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: ≤0.2mmx45°
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-coatd)
Quality Warranty Period: one year under proper use.
 

Notes:
BBO has a low susceptibility to the moisture. The user is advised to provide dry conditions for both the use and preservation of BBO.
BBO is relatively soft and therefore requires precautions to protect its polished surfaces.
When angle adjusting is necessary, keep in mind that the acceptance angle of BBO is small.
THATSHIGH's engineers can select and design the best BBO crystal, if the main parameters of your laser are provided, 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 BBO crystal,THATSHIGH can provide free holder for you .