BBO crystal


Barium borate is an inorganic substance with the chemical formula BaB2O4. It can exist as a hydrate, a dried form, a white powder, or an anaemic crystal. There are two different types of the high-temperature stage (α-BBO) and low-temperature level phase (β-BBO).

1, α-BBO crystal

β-BBO crystal growth has been examined for greater than two decades and has come to be a very extensively made use of the nonlinear optical product, while α-BBO has actually been less researched. α-BBO is an optimal UV birefringent crystal with facility proportion and non-linear impact, yet it has a good birefringence index, particularly in the ultraviolet band with a high transmission proportion (95%), passage range of 189nm ~ 35000nm, stable physical as well as chemical properties, superb mechanical properties.


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

2, β-BBO crystal

BBO crystal is a common nonlinear optical crystal. A nonlinear optical crystal is a sort of crystalline product which utilizes the nonlinear response of light wave polarization when it passes through the medium to react with the light wave, resulting in harmonic generation (nonlinear impact) at the amount frequency, distinction frequency and so forth. BBO crystal is identified as one of the excellent 2nd-order nonlinear optical crystals worldwide.

(1) Nonlinear property

Nonlinear optical crystals are those that show more than quadratic nonlinear optical impacts to laser-intense electrical fields. Nonlinear optical crystal is a sort of functional product, in which frequency increasing (or “regularity conversion”) crystal can be made use of to transform laser wavelength, so as to expand the tunable range of laser, which has vital application value in laser innovation area.


1) Made Use Of 1064nm Nd: YAG laser with dual, three-way, quadruple and also quad regularity.

2) Utilized for dye laser as well as titanium treasure laser of dual regularity, three-way regularity, amount regularity, difference frequency, and so on

3) Optical Parametric Amplifier (OPA) as well as Optical Parametric Oscillator (OPO).

Regularity doubling

The laser regularity doubling strategy greatly expands the laser band and also is the primary technique to transform the laser to the brief wavelength instructions. Laser frequency doubling is commonly utilized in laser innovation. In order to obtain the laser with a much shorter wavelength, it can double the regularity of numerous stages. Today, it has gotten to the practical level, as well as there are industrial devices as well as gadgets, which have an extremely wide variety of applications.

Definition: An impact that makes use of a nonlinear product to achieve a laser regularity twice the frequency of the input light

Regularity increasing is a typical technique made use of to generate brief wavelength light:

1. By doubling the frequency of a 1064nm laser output using a neodymium-doped or ytterbium-doped laser to produce 532nm thumbs-up.

2. Lots of blue laser systems make use of 0.9 um laser (such as Nd: YVO4 generated by 914nm) regularity doubling.

3. By additional increasing the frequency (or by the summing result), lasers can be created in the ultraviolet region at even much shorter wavelengths (see ultraviolet lasers). The major obstacles are the transparency, toughness and solid diffusion of nonlinear crystalline materials in this area (often causing difficult stage matching or extremely narrow stage matching transmission capacity).

(2) Electro-optical properties.

In addition to the exceptional nonlinear result, an additional prominent optical residential property of BBO is the electro-optical impact.

The electro-optic result is a general term for the adjustments of the optical properties of things under the activity of the applied electrical area. Normally this applied electric area adjustments very slowly with time compared to the frequency of light. These various electro-optical impacts fall under two categories:

Modifications in light absorption.

Electroabsorption impact: A variant of light absorption constant generally sense.

Franz-caldisi effect: Modification in light absorption of certain large semiconductors under an applied electrical field.

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

Electric colour effect: The absorption of a certain wavelength by an applied electric area, causing a change in the colour of an object.

Adjustments in refractive index as well as dielectric continuous.

Pockers effect (additionally called linear electro-optic result): The modification of the refractive index of the crystal caused by a used electric area is symmetrical to the strength of the electric field. Just those crystals without inversion proportion can create the Pockers effect.

Kerr effect (additionally known as second-order nonlinear electro-optical effect): The adjustment of the refractive index of the crystal caused by an applied electric field is symmetrical to the square of the electrical area strength. Any kind of crystal can create the Kerr effect, yet the toughness of the result is much lower than that of the Pockers result.


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

Compared with standard KD * P electro-optic modulated crystal, BBO( Barium metaborate β-BaB2O4) crystal has an extremely low absorption coefficient. There are likewise weak piezoelectric buzzing effects, larger range transmission arrays (210-2000nm) as well as other benefits. Compared to RTP electro-optic regulated crystal, BBO crystal has a greater termination ratio, anti-damage threshold and also temperature level adaptability, which contributes to improving the stability of laser output power.

Consequently, the electro-optical Q switch made from BBO crystal is commonly made use of in the electro-optical Q-switched solid-state laser with high rep regularity (1MHz) as well as high power (approximately 1000W), tooth cavity inversion cool Q laser and all-solid picosecond and also femtosecond regeneration boosting laser system. BBO electro-optical Q switch can be switched off and also stand up to as much as 150W of oscillating optical power in the cavity (laser result power as much as 50W) without water air conditioning. The drawbacks of BBO crystals are small electro-optic coefficient and fairly high half-wave voltage, so the half-wave voltage, as well as quarter-wave voltage, can be reduced by increasing the size of the crystal and making use of two BBO crystals in series.

Preventative measures

As a result of the low reliability of BBO, the surface of sleek BBO crystals is easily obscured by moist air. So after the polishing procedure, a thin movie layer is related to the surface area. The safety finishing (P finish) or anti-reflective finishing (AR finishing) shields the crystal surface area from dampness somewhat. Nevertheless, also tiny contaminants (dirt fragments, pressure, fingerprints, etc) can affect the performance of BBO crystals, i.e. transmission or representation. On top of that, BBO crystals are easily harmed if pollutants enter into direct contact with laser radiation.

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