BBO crystal is an inorganic substance with the chemical formula BaB2O4. It can exist as a hydrate, a dehydrated type, a white powder, or an anemic crystal. There are two various types of high-temperature phase (α-BBO) and reduced temperature level phase (β-BBO), and also the phase transition temperature level is 925 ℃.
1, α-BBO
β-BBO crystal growth has been examined for more than two decades and has become an extremely extensively made use of the nonlinear optical product, while α-BBO has actually been less examined. α-BBO is an ideal UV birefringent crystal with facility proportion as well as non-linear effect, yet it has a good birefringence index, specifically in the ultraviolet band with a high transmission ratio (95%), passage variety of 189nm ~ 35000nm, stable physical and also chemical residential properties, superb mechanical properties.
Application
α-BBO crystals have superb optical residential or commercial properties such as huge refractive index as well as large transmittance array and are extensively used in optical deflection innovation, high power laser, and also ultrafast laser applications. It is primarily utilized to make ultraviolet polarization prisms such as the Grantler prism, Wollaston prism, high-power optical isolator, and group speed mismatch compensator of the ultrafast laser.
2, β-BBO
BBO crystal is a usual nonlinear optical crystal. Nonlinear optical crystal is a sort of crystalline material which makes use of the nonlinear reaction of light wave polarization when it goes through the tool to react on the light wave, resulting in harmonic generation (nonlinear impact) at the sum regularity, difference regularity, and so forth. BBO crystal is recognized as one of the exceptional 2nd-order nonlinear optical crystals worldwide.
(1) Nonlinear property
Nonlinear optical crystals are those that show more than quadratic nonlinear optical results to laser extreme electric area. Nonlinear optical crystal is a type of useful product, in which regularity increasing (or “frequency conversion”) crystal can be made use of to transform laser wavelength, so as to extend the tunable range of laser, which has essential application worth in laser modern technology field.
Application
1) Used in 1064nm Nd: YAG laser with dual, three-way, quadruple, and quad frequency.
2) Utilized for color laser as well as titanium treasure laser of double regularity, triple regularity, amount frequency, difference frequency, and so on.
3) Optical Parametric Amplifier (OPA) and Optical Parametric Oscillator (OPO).
Regularity doubling
The laser regularity increasing technique considerably broadens the laser band and is the major technique to change the laser to the brief wavelength direction. Laser frequency increasing is commonly utilized in laser modern technology. In order to get the laser with a much shorter wavelength, it can increase the regularity of multiple phases. At present, it has reached the practical degree, and there are business tools and tools, which have a really wide variety of applications.
Interpretation: An impact that uses a nonlinear material to accomplish a laser frequency twice the regularity of the input light
Regularity doubling is a common method utilized to create brief wavelength light:
1. By increasing the frequency of a 1064nm laser outcome using the neodymium-doped or ytterbium-doped laser to create 532nm thumbs-up.
2. Lots of blue laser systems utilize 0.9 um laser (such as Nd: YVO4 created by 914nm) frequency increasing.
3. By further doubling the frequency (or by the summing impact), lasers can be generated in the ultraviolet area at also shorter wavelengths (see ultraviolet lasers). The major difficulties are the transparency, toughness, and also solid dispersion of nonlinear crystalline materials in this area (often causing difficult phase matching or extremely slim phase matching data transfer).
(2) Electro-optical properties
Along with the exceptional nonlinear result, one more famous optical property of BBO is the electro-optical effect.
The electro-optic impact is a basic term for the changes in optical residential or commercial properties of things under the action of the applied electric field. Typically this applied electrical area adjustments really slowly with time compared to the frequency of light. These different electro-optical impacts come under two groups:
Adjustments in light absorption.
Electroabsorption result: Variant of light absorption constant as a whole feeling.
Franz-caldisi effect: Modification in light absorption of particular big semiconductors under a used electric area.
Quantum confinement Stark effect: Variation of light absorption in certain semiconductor quantum Wells under an applied electrical area.
Electric shade result: The absorption of a particular wavelength by a used electrical area, causing an adjustment in the shade of an item.
Adjustments in refractive index and dielectric constant.
Pockers effect (additionally called direct electro-optic impact): The adjustment of the refractive index of the crystal brought on by a used electrical area is proportional to the strength of the electrical area. Just those crystals without inversion symmetry can produce the Pockers effect.
Kerr effect (likewise referred to as second-order nonlinear electro-optical effect): The modification of the refractive index of the crystal brought on by an applied electric field is symmetrical to the square of the electrical area intensity. Any type of crystal can generate the Kerr effect, however, the strength of the effect is a lot lower than that of the Pockers impact.
Application
BBO Electro-optic Q Switch (Pockels cell).
Compared with conventional KD * P electro-optic regulated crystal, BBO( Barium metabate β-BaB2O4) crystal has a very low absorption coefficient. There are likewise weak piezoelectric ringing effects, bigger spectrum transmission variety (210-2000nm), and other benefits. Compared to RTP electro-optic regulated crystal, BBO crystal has a greater termination ratio, anti-damage limit, and also temperature level flexibility, which is conducive to improving the security of laser result power.
For that reason, the electro-optical Q button made from BBO crystal is often made use of in the electro-optical Q-switched solid-state laser with high rep regularity (1MHz) as well as high power (up to 1000W), tooth cavity inversion air-conditioned Q laser as well as all-solid picosecond and femtosecond regrowth boosting laser system. BBO electro-optical Q switch can be switched off and stand up to approximately 150W of oscillating optical power in the cavity (laser result power approximately 50W) without water cooling. The drawbacks of BBO crystals are little electro-optic coefficient and also reasonably high half-wave voltage, so the half-wave voltage and also quarter-wave voltage can be minimized by enhancing the length of the crystal as well as using two BBO crystals in the collection.
Precautions
As a result of the reduced reliability of BBO, the surface area of sleek BBO crystals is easily obscured by moist air. So after the brightening procedure, a thin movie layer is related to the surface area. The safety finish (P covering) or anti-reflective finishing (AR finish) protects the crystal surface from dampness somewhat. Nevertheless, also little impurities (dust particles, strain, fingerprints, and so on) can affect the performance of BBO crystals, i.e. transmission or reflection. In addition, BBO crystals are conveniently damaged if impurities enter into straight contact with laser radiation.
