BBO crystal is an inorganic compound with the chemical formula BaB2O4. It can exist as a hydrate, a dried kind, a white powder, or a colorless crystal. There are 2 various sorts of high temperature phase (α-BBO) and low temperature level phase (β-BBO), and also the stage transition temperature is 925 ℃.
1.α-BBO
β-BBO crystal development has been studied for more than two decades, and also has become a very widely utilized nonlinear optical material, while α-BBO has actually been much less examined. α-BBO is a perfect UV birefringent crystal with facility balance and non-linear impact, but it has an excellent birefringence index, specifically in the ultraviolet band with a high transmission ratio (95%), passage range of 189nm ~ 35000nm, stable physical as well as chemical residential properties, excellent mechanical properties.
Application
α-BBO crystals have excellent optical properties such as huge refractive index and also vast transmittance range, and are extensively used in optical deflection innovation, high power laser and also ultrafast laser applications. It is primarily used to make ultraviolet polarization prisms such as Grantler prism, Wollaston prism, high power optical isolator and team velocity mismatch compensator of ultrafast laser.
2.β-BBO
BBO is a typical nonlinear optical crystal. Nonlinear optical crystal is a type of crystalline product which uses the nonlinear action of light wave polarization when it travels through the medium to react on the light wave, resulting in harmonic generation (nonlinear effect) at the amount frequency, difference regularity and so forth. BBO crystal is identified as one of the excellent 2nd order nonlinear optical crystals in the world.
(1)Nonlinear property
Nonlinear optical crystals are those that show more than quadratic nonlinear optical impacts to laser intense electrical area. It is a kind of useful material, in which regularity increasing (or “regularity conversion”) crystal can be utilized to transform laser wavelength, so regarding prolong the tunable range of laser, which has vital application worth in laser technology field.
Application
1) Utilized in 1064nm Nd: YAG laser with dual, three-way, quadruple and also quad regularity.
2) Made use of for dye laser and also titanium treasure laser of double regularity, triple regularity, amount regularity, distinction regularity, etc.
3) Optical Parametric Amplifier (OPA) and Optical Parametric Oscillator (OPO).
Optical parametric amplification and oscillation refers to the nonlinear optical results created by multiwave blending.
(2)Electro-optical properties
Along with the excellent nonlinear impact, an additional popular optical building of BBO is the electro-optical impact.
Electro-optic effect is a general term for the adjustments of optical homes of items under the action of applied electric field. Usually this applied electric field adjustments extremely slowly with time contrasted to the frequency of light. These different electro-optical results come under 2 categories:
Changes in light absorption.
Electroabsorption effect: Variation of light absorption constant as a whole feeling.
Franz-caldisi effect: Modification in light absorption of specific huge semiconductors under an applied electrical field.
Quantum arrest Stark effect: Variant of light absorption in certain semiconductor quantum Wells under a used electric area.
Electric color impact: The absorption of a certain wavelength by a used electric area, resulting in a modification in the shade of an object.
Changes in refractive index and also dielectric constant.
Pockers effect (likewise referred to as direct electro-optic impact): The adjustment of refractive index of the crystal brought on by an applied electric field is symmetrical to the strength of the electrical field. Just those crystals without inversion balance can produce the Pockers impact.
Kerr effect (likewise known as second-order nonlinear electro-optical impact): The adjustment of refractive index of the crystal brought on by a used electrical field is proportional to the square of the electric area strength. Any crystal can produce the Kerr effect, but the strength of the impact is a lot less than that of the Pockers impact.
Application.
BBO Electro-optic Q Switch (Pockels cell).
Compared to conventional KD * P electro-optic regulated crystal, BBO( Barium metabate β-BaB2O4) crystal has extremely low absorption coefficient. There are likewise weak piezoelectric buzzing impact, broader spectrum transmission array (210-2000nm) and various other advantages.
Compared to RTP electro-optic modulated crystal, BBO crystal has higher termination proportion, anti-damage limit as well as temperature versatility, which is conducive to enhancing the stability of laser outcome power. Therefore, the electro-optical Q button made of BBO crystal is typically made use of in the electro-optical Q-switched solid-state laser with high repeating frequency (1MHz) and high power (up to 1000W), tooth cavity inversion air-conditioned Q laser as well as all-solid picosecond and femtosecond regeneration amplification laser system.
BBO electro-optical Q button can be switched off and stand up to approximately 150W of oscillating optical power in the tooth cavity (laser outcome power up to 50W) without water air conditioning. The disadvantages of BBO crystal are tiny electro-optic coefficient and also fairly high half-wave voltage, so the half-wave voltage and quarter-wave voltage can be lowered by increasing the size of crystal and also making use of two BBO crystals in collection.
Precautions
Due to the reduced deliquability of BBO, the surface area of sleek BBO crystals is quickly obscured by wet air. So after the brightening process, a thin movie layer is applied to the surface. The protective finish (P layer) or anti-reflective finishing (AR layer) safeguards the crystal surface area from wetness to some extent. However, even small impurities (dust particles, strain, finger prints, etc) can affect the efficiency of BBO crystals, i.e. transmission or representation. In addition, BBO crystals are conveniently damaged if contaminants enter direct contact with laser radiation.
