BBO (beta-BaB2O4) is an excellent non-linear crystal for frequency-doubling (SHG) of Visible and Near IR laser light, OPO/OPG/OPA pumped by ultrafast pulses of wavelengths in the Near IR to UV, and sum-frequency mixing (SFM) into the Visible to the deep UV. BBO is one of the few practical crystal for use below 500 nm in SHG and SFM.

BBO crystal has broad tunability, high damage threshold, and high efficiency. BBO’s small acceptance angle requires a very good beam quality and its large walkoff results in output beams that are very elliptical or slit-like. Type I is usually much more efficient than type II operation. BBO can not be used for NCPM (temperature tuned) application.

BBO is very good for tunable laser sources, such as ultrafast Ti:Sapphire or dye lasers. And it is also widely used for SHG, 3HG, 4HG, and autocorrelation of femtosecond and picosecond Ti:Sapphire lasers; SHG, 3HG, 4HG, 5HG of YAG lasers at 1064 nm and 1320 nm to yield output of 212-660nm; SHG of tunable dye or solid-state laser sources from 410-750 nm to yield output of 205-375 nm, SFM of dye laser and YAG harmonics to yield output of 189-400 nm; DFM (difference-frequency mixing) from the Visible to the IR range up to over 3000 nm; OPO pumped with SHG or 3HG of YAG or Ti:Sapphire with an output range of 400-3000 ; Intracavity SHG of Argon ion lasers (488, 514 nm) or Copper vapor lasers (510 nm, 578 nm).


Crystal Structure Trigonal, space group R3c
Cell Parameters a = b = 12.532Ã, c = 12.717Ã…, Z = 6
Melting point 1095+ 5°C
Transition temperature 925+ 5°C
Optical homogeneity d n ~ 10-6/cm
Mohs hardness 4
Density 3.85 g/cm3
Absorption Coefficient < 0.1%/cm (at 1064nm)
Specific heat 490 J/kg/°C
Hygroscopic susceptibility low
Thermal expansion coefficients a, 4 x 10-6/K; c, 36 x 10-6/K
Thermal conductivity Perpendicular to c, 1.2 W/m/°C
Parallel to c, 1.6 W/m/°C

Linear Optical Properties

Transparency range 189-3500 nm
Refractive indices: ne = 1.5425, no = 1.6551 @ 1064 nm
ne = 1.5555, no = 1.6749 @ 532 nm
ne = 1.6146, no = 1.7571 @ 266 nm
Therm-optic coefficients dno/dT = -9.3 x 10-6/°C
dne/dT = -16.6 x 10-6/°C

Sellmeier Equations (l in mm)

no2 (l) = 2.7359 – 0.01354l2+ 0.01878/(l2-0.01822)
ne2(l) = 2.3753 – 0.01516l2+ 0.01224/(l2-0.01667)

Nonlinear Optical Properties

Phase-matchable output wavelength 189 – 1750 nm
NLO coefficients d11 = 5.8 x d36 (KDP)
d31= 0.05 x d11
d22 < 0.05 x d11
Electro-optic coefficients y11 = 2.7 pm/V
Half-wave voltage 48 KV (at 1064 nm)
Damage threshold 5 GW/cm2 (10 ns) @1064nm
10 GW/cm2 (1.3 ns) @ 1064 nm
1 GW/cm2 (10 ns) @532 nm
7 GW/cm2 (250 ps) @ 532 nm


Material β-BBO Crystal  


Thickness 0.01mm-20mm
Surface Quality 10-5
Optical Axis Orientation 3 arc min
Parallelism <10 ace sec
Flatness λ/10@633nm
Clear Aperture >95%
Coating P-coating or AR coating
Mount Upon Customer’s Specification


BBO Typical Specifications

Thin crystals: (5-10) x (5-10) x (0.01 – 1) mm3
Regular sizes: 4 x 4 mm2 to 20 x 20 mm2 in diameter, 3 – 20 mm in length
Different cuts, sizes and AR coatings are available upon request.
BBO is hygroscopic. In application, protective coating or AR coating or crystal housing is usually recommended.