The nonlinear crystal is the crystal that reveals the nonlinear optical result greater than two times for the laser electric field. Nonlinear optical crystal is a type of functional material, in which the frequency-doubling (or “frequency conversion”) crystal can be made use of to convert the laser wavelength, so regarding prolonging the tunable range of the laser, which has important application value in the field of laser innovation.
There are thousands of various types of nonlinear crystals, Common lithium niobate (LiNbO3–LN), lithium tantalate (LiTaO3–LT), potassium dihydrogen phosphate (KH2PO4–KDP), potassium dideuterium phosphate (KD2PO4–DKDP), lithium iodate (LiIO3–LI), potassium titanium phosphate (KTiOPO4–KTP), barium metaborate (BaB2O4–BBO), lithium trisborate (LiB3O5–LBO), potassium niobate (KNbO3–KN), cesium borate (CSB3O5–CBO), cesium lithium borate (LiCSB6O10–CLBO), potassium beryllium fluorborate (KBe2BO3F2–KBBF), silver thiogas (AgGaS2–AGS), silver selenium gallium (AgGaSe2–AGSe, arsenic-cadmium germanium (CDGEAS–CGA), cadmium selenide CdSe, Gallium selenide GaSe, phospho-germanium zinc (ZnGEP2–ZGP) are extensively used in laser regularity increasing, sum frequency, distinction frequency, optical parametric boosting, electro-optic inflection, electro-optic deflection, and so on.
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For nonlinear optical crystals, in addition to having huge efficient nonlinear coefficients, the following buildings are also required:
- In general, the crystal needs to have high transparency for the wavelength involved;
- The internal absorption should be reduced, and the anti-damage limit must be high;
- Stable physical and chemical residential properties, modest hardness, no deliquescence;
- Secure crystal quality, large size, affordable price, simple covering.
Some instances of typical nonlinear optical crystals
BBO nonlinear crystal
BBO crystal is identified as one of the most exceptional second-order nonlinear optical crystals worldwide. One of its amazing features is its wide frequency inflection array. A lot more importantly, by utilizing its regularity down-conversion procedure, BBO crystal can be made right into a constantly tunable totally treated tuned laser with the wavelength from noticeable to near-infrared.
Barium borate (BBO) has big birefringence and reduced dispersion, high damage threshold, vast stage matching array, good temperature level stability, large nonlinear optical effect, and the frequency increasing coefficient is 6 times that of KDP crystal. It has a really large range of pervious to light, reduced absorption coefficient, the weaker the piezoelectric ringing effect, relative to various other crystal electro-optic inflection, has greater extinction ratio, the larger phase in a supporting function, high optical damage limit, the temperature of the broadband matching, and exceptional optical homogeneity and also to boost the laser result power security, Particularly for the triple frequency Nd: YAG laser has a vast array of applications.
LBO nonlinear crystal
Lithium trisborate, likewise known as LBO, is an outstanding high-power UV frequency-doubling crystal with a vast passage band, high damage threshold as well a huge approval Angle. Lithium trisborate (LiB3O5, referred to as LBO) crystal is frequently used in middle and high power 1064nm double and also three-way frequency lasers. It has an extremely high light damage resistance threshold, great light uniformity, broad obtaining Angle, good mechanical residential or commercial properties, solid thermal shock resistance, microdelixation, and also a big nonlinear coefficient.
It is just one of the nonlinear crystals with excellent extensive buildings. The biggest benefit of LBO is that it can use temperature level adjusting to accomplish non-critical stage matching (NCPM). When the frequency doubling procedure pleases the non-critical phase matching relationship, the separation Angle in between the essential regularity as well as the second harmonic of the frequency doubling is 0. At this time, the effective length of the LBO crystal can theoretically get to infinity, which can compensate for its tiny nonlinear coefficient. Due to its large damage limit, this means that high-power fundamental wave pumping can be accomplished.
Compared with LiNbO3 crystal, MgO: LiNbO3 crystal has its special advantages in the application of NCPM regularity increasing, blending as well as an optical parametric oscillation in ND-doped lasers.
The anti-damage limit of drugged MgO: LiNbO3 crystal is more than two times greater than that of pure LiNbO3 crystal.