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BBO Crystals

BBO Crystals
BBO Crystals BBO Crystals BBO Crystals

BBO crystal remains the most versatile nonlinear optical crystals thanks to its unique combination of optical properties (e.g.  broad transmission and phase matching ranges, high damage threshold) and availability of large, high quality single crystals. Newlight's BBO crystals have been widely used in second, third, fourth or fifth harmonic generations for high power visible/UV sources, and optical parametric conversions for high power broadly tunable sources.
BBO products on this page are thick crystals (> 3 mm) for applications with picosecond (ps), nanosecond (ns), or long pulse/CW  lasers.
For thin/ultrathin BBO products (thickness: 0.01 mm - 3 mm) developed for frequency conversions of ultrafast femtosecond (fs) lasers, please go to thin/ultrathin BBO crystals.
For BBO products (including paired BBO crystals) developed for spontaneous down conversions (SPDC), please go to SPDC components.

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Part No. Description Application Wavelength Price Availability Add to Cart

Newlight BBO  features,

WB01158_1.GIF (255 bytes) Broad phase-matching range from 410 nm to 2100 nm 
WB01158_1.GIF (255 bytes) Useful optical transmission from 190 nm to 3500 nm 
WB01158_1.GIF (255 bytes) Large effective second-harmonic-generation (SHG) coefficient about 6 times greater than that of KDP crystal
WB01158_1.GIF (255 bytes) High damage threshold of 10 GW/cm2 for 100ps pulse-width at 1064 nm
WB01158_1.GIF (255 bytes) High optical homogeneity with δn ~ 10-6 /cm
WB01158_1.GIF (255 bytes) Wide temperature-bandwidth of about 55 oC
WB01158_1.GIF (255 bytes) Low thermo-optic coefficient

Structural and Physical Properties:

Crystal Structure Trigonal, space group R3c, Point group 3m
Cell Parameters a = b = 12.532 Å, c = 12.717Å, Z = 6
Melting Point 1095°C
Transition Temperature 925°C
Mohs Hardness 4
Density 3.85 g/cm3
Specific Heat 1.91 J/cm3 x K
Hygroscopic Susceptibility Low
Thermal Expansion Coefficients a, 4 x 10-6 /K;  c, 36 x 10-6 /K
Thermal Conductivity ⊥c, 1.2 W/m/K;  //c, 1.6 W/m/K

Linear Optical Properties:

Transparency Range 189-3500 nm
Optical Homogeneity δn ~ 10-6/cm
Absorption Coefficient < 0.1%/cm (at 1064 nm)
Sellmeier Equations
 (λ in µm)

Refractive Indices
               at 1064 nm 
               at 800 nm
               at 532 nm 
               at 400 nm
               at 266 nm  

no = 1.6545, ne = 1.5392
no = 1.6606, ne = 1.5444
no = 1.6742, ne = 1.5547
no = 1.6930, ne = 1.5679
no = 1.7585, ne = 1.6126
Thermo-optic Coefficients dno/dT = -9.3 x 10-6/°C
dne/dT = -16.6 x 10-6/°C

Nonlinear Optical Properties:

Phase-matchable SH Wavelengths: 189 - 1750 nm
NLO Coefficients d11 = 5.8 x d36(KDP)
d31 = 0.05 x d11
d22 < 0.05 x d11
Effective Nonlinearity Expressions dooe= d31 sinθ +(d11 cos3φ - d22 sin3φ) cosθ
deoe= (d11 sin3φ + d22 cos3φ) cos2θ
Electro-optic Coefficients γ11 = 2.7 pm/V, γ22, γ31 < 0.1 γ11
Half-wave Voltage 48 kV (at 1064 nm)
Damage Threshold (Bulk)
       at 1064 nm
       at 532 nm
5 GW/cm2 (10 ns); 10 GW/cm2 (1.3 ns)
1 GW/cm2 (10 ns); 7 GW/cm2 (250 ps)

Application Examples:

BBO is of particular importance in the visible and far UV. A wide variety of phase-matching applications are possible, including the following:

WB01158_1.GIF (255 bytes) Second, third, fourth and fifth harmonic generation of Nd doping lasers
WB01158_1.GIF (255 bytes) Second harmonic generation to generate wavelengths as short as 204.8 nm
WB01158_1.GIF (255 bytes) Shorter wavelengths (193 nm) can be generated by sum frequency mixing  
WB01158_1.GIF (255 bytes) Frequency doubling, tripling and -mixing of Dye lasers
WB01158_1.GIF (255 bytes) Second, third and fourth harmonic generation of Ti:Sapphire lasers
WB01158_1.GIF (255 bytes) Optical parametric amplifier (OPA) and optical parametric oscillators (OPO)
WB01158_1.GIF (255 bytes) Frequency-doubling of Argon ion, Cu-vapor and Ruby lasers
WB01158_1.GIF (255 bytes) Transverse field Pockel cells made from BBO useful when high average powers or
  short wavelengths used


BBO is the only NLO material which can be used to produce the fifth harmonic generation (5HG) of Nd:YAG lasers at 213 nm. Because of a small acceptance angle and large angular walkoff, 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.

 NLO properties for harmonic generations with Type I PM in BBO crystal
Harmonics SHG THG 4HG 5HG
Effective NLO Coefficient( x d36(KDP) ) 5.3 4.9 3.8 3.4
Acceptance Angle (mrad-cm) 1.0  0.5 0.3 0.2
Walk-off Angle (°) 3.2   4.1 4.9 5.5


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 following, respectively.

  Type I OPO Tuning Curves Type II OPO Tuning Curves

Ultrafast Laser (Ti:sapphire)

Frequency doubling and tripling of ultrashort lasers are the applications in which BBO shows superior properties to KDP and ADP crystals. BBO crystals as thin as 0.01 mm (10 µm ) for these purposes are available. A laser pulse as short as 10 fs can be efficiently frequency doubled with a thin BBO crystal in terms of both phase-velocity and group-velocity matching.



Specifications of BBO components:


Wavefront Distortion: Less than λ/8  @ 633 nm
Dimension Tolerance:  (W+/-0.1 mm) x (H+/-0.1 mm) x (L+0.2/-0.1 mm)
Clear Aperture: > 90% central area
Flatness: λ/8 @ 633 nm
Surface Quality:  Scratch/Dig 10/5 per MIL-O-13830A
Parallelism:     better than 20 arc seconds
Perpendicularity:      5 arc minutes
Angle Tolerance:      Δθ < 0.25o, Δφ < 0.25o



1. Protective coating (P-coating): This is a single-layer MgF2 coating protecting a polished surface of BBO crystal from fogging due to ambient moisture. It also partially reduces reflection from the polished surface at a certain wavelength range.

Coating curve: P-coating (typical).

2. Anti-reflective coatings (AR coatings): These are multi-layer dielectric coatings. Single-band, dual-band or broad-band AR coatings on BBO surfaces are available upon request.

Coating curves: AR532/266 nm, AR1064/532 nm, AR800/400 nm, AR710/355 nm (typical). 


For customer convenience the crystals can be mounted in an 1" anodized aluminum (Al) mount.  The mounted crystals may be further mounted in a conventional 1" mirror mount to be angle tuned for phase matching (as shown to the right, mirror mounts and posts are not included ). Water-cooled mounts for high power applications can be offered upon request.   


BBO Crystal Handling:

BBO has a low susceptibility to moisture. The AR coating or the protective coating (P-coating) on the crystal faces can protect the faces from moisture to some extent. It is fine to leave the crystal in the  setup for most optics labs with HR =< 40%.  However, we suggest to store the crystal in a desiccator if it will not be used for over > 2 weeks to prolong the crystal lifetime. Alternatively, a small enclosure (with openings for light) may be built around the crystal with a continuous flow of dry nitrogen of air into the enclosure. The dry nitrogen/air pressure needs only to be slightly above the atmosphere to keep the small volume around the crystal dry and clean.

BBO is relatively soft and therefore requires precautions to protect the surfaces. 

Cleaning the Crystals:

Dust and stains on crystal surfaces can cause scattering/loss of light and can even react with light to damage optical surfaces at a high incident laser power.

You can inspect the crystal surface for dust and stains by holding it near a bright visible-light source. Viewing at different angles helps to see scattering from dust and stains. The crystal surface has to be cleaned if dust and stains are found.

You should perform the following cleaning procedures in a clean, low-dust environment while wearing powder-free gloves or finger cots.

1. Blowing off the crystal surface

A canister of compressed N2/clean air or a blower bulb ( ) should be first used to blow off dust and other loose contaminants. If a dry nitrogen line is available in the lab, an air gun can also be used  to blow away dust particles. Blow off the surface gently. Do not blow off the crystal itself from your hand !

2. Drop and Drag Method

Hold the crystal so that the crystal surface is horizontal and slightly above your fingers. Take a fresh, clean sheet of lens tissue and place it on the crystal.  Make sure the lens tissue can be drawn across the crystal surface. Next place a small drop of pure isopropyl alcohol (IPA) on the lens tissue on top of the crystal surface. The weight of the solvent will cause the lens tissue to come into contact with the crystal surface. Slowly but steadily drag the damp lens tissue across the crystal surface being careful not to lift the lens tissue off of the surface. Continue dragging the lens tissue until it is off of the surface.

The amount of the solvent can be adjusted for various crystal size so the lens tissue is kept damp for the entire drag but there is not any visible trace of solvent on the crystal surface after the drag is finished. Inspect the surface and repeat if necessary, but only use each sheet of lens tissue once.

If the crystal surfaces are still “dirty” after the above cleaning procedures, the surfaces might have been damaged. Please contact us for rework of the crystals.


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