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. BBO is of particular importance in the visible and far UV range.
BBO is hygroscopic. The user is advised to provide dry conditions for both working and storage 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.
BBO is grown with the flux method. It 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 achieved by angle-tuning.
|| Trigonal, space group R3c
|| a=b=12.532Å, c=12.717Å, Z=6
|| About 1095℃
|Thermal Conductivity Coefficients
⊥c: 1.2W/m/K; //c: 1.6W/m/K
|Thermal Expansion Coefficients
|| α11=4 x 10-6/K; α33=36x 10-6/K
|SHG Phase Matching Range
||409.6-3500nm(Type I) 525-3500nm(Type II)
|Thermal Optic Coefficients (/℃)
||<0.1%/cm at 1064nm; <1%/cm at 532nm
||0.8mrad.cm (θ, Type I,1064 SHG)
1.27mrad.cm (θ, Type II,1064 SHG)
||2.7° (Type I 1064 SHG)
3.2° (Type II 1064 SHG)
||deff (I) = d31sinθ + (d11cosΦ - d22sin3Φ) cosθ
deff (II) = (d11sin3Φ + d22cos3Φ) cos2θ
|Non-vanished NLO susceptibilities
||d11 = 5.8 x d36(KDP)
d31 = 0.05 x d11
d22 < 0.05 x 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
||7KV (at 1064nm,3*3*20mm3)
|Relative Dielectric Constant:
||εs11/εo : 6.7
εs33/εo : 8.1
Tan δ < 0.001
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. BBO is the only NLO material which can be used to produce the fifth harmonic generation (5HG) of Nd:YAG lasers at 213 nm.
|Relevant NLO properties for type I BBO crystal
|Fundamental wavelength: 1064nm
|Effective NLO Coefficient (d36(KDP))
|Acceptance Angle (mrad-cm)
|Walk-off Angle (°)
The phase matching angles of frequency doubling are shown in following figure.
Ultrafast Pulse (Ti:sapphire) Laser
Frequency-doubling and -tripling of ultrashort-pulse lasers are the applications in which BBO shows superior properties. As thin as 0.02mm BBO for this purpose is available.. 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.
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 are shown in following figure, respectively.
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 and LiNbO3. It has many advantages, including a very short pulse, good beam quality and compact size. Although it has a relative small electro-optic coefficient, the Half-wave voltage is high (7KV at 1064nm,3*3*20mm3), long and thin BBO can reduce the voltage requirements. CRYSTECH can supply 25mm long high quality BBO crystal with Z-cut, AR-coated and Gold plated on the side faces.
● SHG, THG, 4HG, 5HG of Nd lasers
● SHG, THG, 4HG of Ti:Al2O3 and Alexandrite lasers
● SHG, THG and Frequency-mixing of Dye lasers
● SHG of Argon ion, Cu-vapor and Ruby lasers
● OPA and OPO
● Electro-Optical application (Pockels Cell)
● SHG and SFG
● Wide transmission region
● Broad PM SHG range
● Large effective SHG coefficient
● High damage threshold
● Wide temperature-bandwidth
● High optical homogeneity
||≤ 0.2mm x 45°
||1GW/cm² (1064nm, 10ns, 10Hz)