BBO crystal

Barium borate is an inorganic compound with the chemical formula Bachelor’s degree( BO2) 2. It can exist as a hydrate, a dried kind, a white powder, or an anemic crystal. There are 2 different kinds of high temperature phase (α-BBO) and reduced temperature level phase (β-BBO), and the stage transition temperature level is 925 ℃.

1. α-BBO

β-BBO crystal growth has been researched for more than 20 years, as well as has ended up being a very extensively made use of nonlinear optical material, while α-BBO has been much less researched. α-BBO is an ideal UV birefringent crystal with facility symmetry as well as non-linear impact, yet it has a good birefringence index, specifically in the ultraviolet band with a high transmission proportion (95%), passage range of 189nm ~ 35000nm, stable physical and also chemical residential properties, excellent mechanical properties.


α-BBO crystals have exceptional optical properties such as big refractive index as well as large transmittance array, and also are commonly utilized in optical deflection technology, high power laser and ultrafast laser applications. It is mostly utilized to make ultraviolet polarization prisms such as Grantler prism, Wollaston prism, high power optical isolator and group speed mismatch compensator of ultrafast laser.

2. β-BBO

BBO nonlinear crystal is a typical nonlinear optical crystal. Nonlinear optical crystal is a type of crystalline product which utilizes the nonlinear response of light wave polarization when it travels through the tool to respond on the light wave, resulting in harmonic generation (nonlinear result) at the amount regularity, distinction regularity and more. BBO crystal is identified as one of the outstanding 2nd order nonlinear optical crystals in the world.

Nonlinear property

Nonlinear optical crystals are those that reveal more than quadratic nonlinear optical results to laser extreme electric area. Nonlinear optical crystal is a kind of practical material, in which regularity increasing (or “frequency conversion”) crystal can be made use of to transform laser wavelength, so regarding extend the tunable series of laser, which has vital application value in laser innovation field.


1) Utilized in 1064nm Nd: YAG laser with double, triple, quadruple as well as quad regularity.
Frequency increasing

The laser regularity increasing technique substantially expands the laser band and is the main technique to change the laser to the brief wavelength direction. Laser regularity increasing is commonly utilized in laser modern technology. In order to obtain the laser with shorter wavelength, it can increase the frequency of numerous stages. Presently, it has actually gotten to the useful degree, as well as there are business devices and also devices, which have a really wide range of applications.

Interpretation: An impact that uses a nonlinear material to attain a laser frequency twice the frequency of the input light

Frequency increasing is a common method used to produce brief wavelength light:

  • By doubling the frequency of a 1064nm laser outcome making use of neodymium doped or ytterbium-doped laser to create 532nm thumbs-up.
  • Numerous blue laser systems use 0.9 um laser (such as Nd: YVO4 produced by 914nm) regularity increasing.
  • By more increasing the frequency (or by the summing effect), lasers can be created in the ultraviolet area at even much shorter wavelengths (see ultraviolet lasers). The main obstacles are the transparency, toughness and solid dispersion of nonlinear crystalline materials in this region (often causing tough phase matching or really slim phase matching bandwidth).
2) Used for dye laser and also titanium gem laser of dual frequency, three-way frequency, amount regularity, distinction frequency, etc
3) Optical Parametric Amplifier (OPA) and also Optical Parametric Oscillator (OPO).

optical parametric amplification and also oscillation refers to the nonlinear optical results created by multiwave blending. OPA as well as oscillation are both second-order nonlinear optical mixing procedures. Optical parametric amplification and also oscillation of three-wave blending have actually been examined most as well as have actually been widely used in the generation of tunable lasers.

Electro-optical properties

In addition to the excellent nonlinear impact, an additional prominent optical property of BBO is the electro-optical effect.

Electro-optic result is a general term for the modifications of optical residential properties of things under the activity of used electric area. Normally this applied electric area adjustments extremely slowly with time contrasted to the frequency of light. These different electro-optical impacts fall into two classifications:

Changes in light absorption

Electroabsorption effect: Variant of light absorption constant as a whole sense.

Franz-caldisi result: Modification in light absorption of specific big semiconductors under an applied electrical field.

Quantum confinement Stark impact: Variation of light absorption in certain semiconductor quantum Wells under a used electric field.

Electric shade effect: The absorption of a particular wavelength by an applied electric field, causing a change in the color of a things.

Modifications in refractive index and dielectric constant.

Pockers effect (likewise referred to as direct electro-optic result): The change of refractive index of the crystal brought on by an applied electrical area is proportional to the intensity of the electric field. Only those crystals without inversion symmetry can produce the Pockers impact.

Kerr effect (also referred to as second-order nonlinear electro-optical result): The adjustment of refractive index of the crystal caused by a used electric field is proportional to the square of the electrical area strength. Any crystal can create the Kerr result, yet the strength of the result is much less than that of the Pockers impact.


BBO Electro-optic Q Switch ( BBO Pockels cell).

Compared to conventional KD * P electro-optic modulated crystal, BBO( Barium metabate β-BaB2O4) crystal has extremely low absorption coefficient. There are also weak piezoelectric ringing effect, larger spectrum transmission variety (210-2000nm) and various other advantages. Compared to RTP electro-optic regulated crystal, BBO crystal has higher extinction proportion, anti-damage threshold and also temperature level flexibility, which contributes to improving the security of laser output power. Consequently, the electro-optical Q switch made from BBO crystal is often utilized in the electro-optical Q-switched solid-state laser with high repetition regularity (1MHz) as well as high power (approximately 1000W), tooth cavity inversion air-conditioned Q laser and also all-solid picosecond as well as femtosecond regrowth amplification laser system. BBO electro-optical Q switch can be switched off as well as stand up to approximately 150W of oscillating optical power in the dental caries (laser output power approximately 50W) without water cooling. The disadvantages of BBO crystal are tiny electro-optic coefficient as well as reasonably high half-wave voltage, so the half-wave voltage as well as quarter-wave voltage can be reduced by raising the length of crystal and also making use of 2 BBO crystals in series.


As a result of the low deliquability of BBO, the surface of refined BBO crystals is quickly blurred by wet air. So after the brightening procedure, a slim film covering is related to the surface area. The protective finish (P coating) or anti-reflective covering (AR finishing) secures the crystal surface from dampness to some extent. Nevertheless, even small contaminants (dirt fragments, stress, finger prints, and so on) can affect the performance of BBO crystals, i.e. transmission or representation. Additionally, BBO crystals are conveniently harmed if contaminants enter into straight contact with laser radiation.

Read more: Laser gain medium

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