The nonlinear crystal is the crystal that reveals the nonlinear optical result more than twice for the laser electric area. Nonlinear optical crystal is a type of useful material in which the frequency-doubling (or “frequency conversion”) crystal can be utilized to convert the laser wavelength, so regarding prolonging the tunable series of the laser, which has important application worth in the field of laser innovation.
There are numerous various kinds of nonlinear crystals,
- Common lithium niobate (LiNbO3–LN),
- lithium tantalate (LiTaO3–LT),
- potassium dihydrogen phosphate (KH2PO4–KDP),
- potassium deuterium phosphate (KD2PO4— DKDP),
- lithium iodate (LiIO3–LI),
- potassium titanium phosphate (KTiOPO4–KTP),
- barium metaborate (BaB2O4— BBO),
- Lithium Triborate (LiB3O5— LBO),
- potassium niobate (KNbO3–KN),
- cesium borate (CSB3O5–CBO),
- cesium lithium borate (LiCSB6O10–CLBO),
- potassium beryllium fluoroborate (KBe2BO3F2–KBBF),
- Silver Thiogallate (AgGaS2— AGS),
- silver selenium gallium (AgGaSe2— AGSe,
- arsenic-cadmium germanium (CDGEAS-CGA),
- cadmium selenide CdSe,
- Gallium selenide GaSe,
- phospho-germanium zinc (ZnGEP2-ZGP)
They are extensively utilized in laser frequency doubling, amount frequency, distinction frequency, optical parametric amplification, electro-optic modulation, electro-optic deflection, etc.
Nonlinear crystal characteristic
For nonlinear optical crystals, along with having huge efficient nonlinear coefficients, complying with residential properties is also required:
- Generally, the crystal must have high transparency for the wavelength included;
- The internal absorption ought to be low. The anti-damage threshold ought to be high;
- Steady physical and also chemical properties, moderate firmness, no deliquescence;
- Certain crystal quality, plus size, sensible rate, easy layer.
- Below are some examples of usual nonlinear optical crystals.
BBO Nonlinear crystal
BBO crystal is recognized as the most excellent second-order nonlinear optical crystal on the planet. Among its exceptional characteristics is its wide regularity inflection variety. Much more significantly, BBO crystal can be made into a continuously tunable cured tuned laser with a wavelength from noticeable to near-infrared by utilizing its regularity down-conversion procedure.
Barium borate (BBO) has huge birefringence, reduced diffusion, high damage limit, large phase matching variety, excellent temperature security, huge nonlinear optical result, and the frequency increasing coefficient is six times that of KDP crystal.
It has an extremely wide range of pervious to light, low absorption coefficient, the weaker the piezoelectric ringing impact, about various other crystal electro-optic modulation, has higher termination proportion, the larger stage in a supporting role, high optical damage threshold, the temperature level of the broadband matching, as well as outstanding optical homogeneity and to boost the laser result power security, Specifically for the three-way frequency Nd: YAG laser has a wide range of applications.
LBO Nonlinear crystal
Lithium Triborate, called LBO, is an outstanding high-power UV frequency-doubling crystal with a vast transmittance band, high damage limit, and a big acceptance Angle. Lithium Triborate (LiB3O5, referred to as LBO) crystal is often used in middle and high power 1064nm dual and three-way regularity lasers. It has a high light damage resistance limit, excellent light uniformity, broad obtaining Angle, great mechanical residential properties, solid thermal shock resistance, microduplication, and a big nonlinear coefficient.
It is just one of the nonlinear crystals with superb comprehensive residential or commercial properties. The most significant benefit of LBO is that it can use temperature level tuning to achieve non-critical stage matching (NCPM).
When the regularity doubling procedure satisfies the non-critical phase matching connection, the separation Angle between the fundamental frequency and the 2nd harmonic of the regularity doubling is 0. Currently, the efficient length of the LBO crystal can theoretically reach infinity, which can make up for its little nonlinear coefficient. Due to its large damage limit, high-power essential wave pumping can be attained.
MgO: LiNbO3 Nonlinear crystal
Compared to LiNbO3 crystal, MgO: LiNbO3 crystal has distinct advantages in applying NCPM frequency increasing, blending, and optical parametric oscillation in ND-doped lasers.
The anti-damage threshold of doped MgO: LiNbO3 crystal is more than two times higher than that of pure LiNbO3 crystal.