In the nonlinear optical crystal, BBO crystal is a kind of crystal with obvious comprehensive advantages and good performance. It has a very wide light transmission range, a large matching angle, a high resistance to light damage threshold, and a broadband temperature matching. Excellent optical uniformity, especially for the triple frequency of Nd:YAG lasers.

Potassium Dihydrogen Phosphate (KDP) and Potassium Deuterium Phosphate (KD*P) are among the most widely-used commercial NLO materials. They are commonly used for doubling, tripling and quadrupling of Nd:YAG laser at the room temperature. In addition, they are also excellent electro-optic crystals with high electro-optic coefficients, widely used as electro- optical modulators, Q-switches, and Pockels Cells, etc.

Selenium Germanium Gallium Barium (BGGSe)
BaGa2GeSe6 (BGGSe crystal for short) belongs to R3 space group of tripartite system, which has high laser damage threshold, wide transmission range (0.5~18μm), moderate birefringence, large nonlinear coefficient, stable chemical properties, high crystal symmetry and easy processing. Nd:YAG laser can be used for pumping, and it has important application potential in frequency conversion of infrared lasers such as frequency doubling of CO and CO2 lasers and generation of mid-far infrared lasers by optical parametric oscillation. Because of its low dispersion and high damage threshold, BGGSe crystal has advantages in ultra-wide mixing and ultra-short pulse output.

Barium Gallium Selenide (BGSe)
BaGa4Se7 (BGSe for short) has large band gap (2.64eV), wide light transmission range (0.47~18μm), large nonlinear effect (d11=24.3 pm/V, d13=20.4 pm/V) and moderate birefringence （Δn=0.06@2μm）. BGSe crystal has good growth performance, and it is easy to obtain large-size and high-quality single crystals, which is suitable for high power output. BGSe crystal can be pumped by 1~3μm laser, and the highest tunable laser can reach 18 μm.

Silver Gallium Selenide (AGSe)
AgGaSe2 silver selenide crystal, referred to as AGSe crystal for short, is one of the most effective crystal materials for frequency doubling of mid-infrared laser, and it also has excellent performance of three-wave nonlinear interaction (OPO). The useful light transmission range of AGSe crystal is 0.9-16μm, and it has wide phase matching ability. With the mature laser pumping, the OPO of AGSe crystal shows wide infrared tunable performance. Pumping AgGaSe2 crystal with Ho:YLF 2.05μm to obtain 2.5-12μm OPO tuned light source; Non-critical phase matching OPO pumped by 1.4-1.55 μm tuning light source outputs 1.9-5.5 μm tuning light source; Frequency doubling of pulsed CO2 laser.

Silver Gallium Sulfide (AGS)
AgGaS2(AGS) crystal is one of the most effective nonlinear laser crystals used in the infrared working band at present. Because of its large nonlinear coefficient, high infrared transmittance, low optical absorption and scattering, and low wavefront distortion performance, its application in the infrared field has been popularized more and more. At present, this kind of crystal is the best choice for the frequency doubling material of CO2 laser with 10.6μm output.

CrZnS and CrZnSe laser crystals typically do not exhibit excited-state absorption or upconversion. They possess an extremely broad absorption band, a large emission cross-section, excellent fluorescence quantum efficiency at room temperature, an ultra-wide emission bandwidth, as well as good chemical and mechanical properties. These characteristics make CrZnS & CrZnSe laser crystals excellent sources for efficient and powerful tunable mid-infrared lasers. Since the mid-infrared region corresponds to the atmospheric window, CrZnS & CrZnSe laser crystals hold significant potential for applications in optical communication, pollution gas detection, industrial combustion product testing, and other fields.

Lithium Thioindate (LiInS2 or LIS) is an AIBIIIC2VI ternary semiconductor crystallizing with mm2 symmetry.
LiInS2 has a large nonlinear optical (NLO) coefficient, the non-linear characteristics of the crystals are close to AgGaS2 and AgGaSe2, but their crystal structures are different. LiInS2 crustal has a high laser damage threshold, and a wide transparent wavelength range, the useful transparency range of LiInS2 is 0.5–8 μm, which makes it an excellent mid-infrared NLO crystal. LiInS2 is pyroelectric as well, its electro-optical parameters are the base for using it as an effective electro-optical material. Three‐frequency collinear phase matching is possible in LiInS2, LiInS2 has large birefringence and low absorption in the THz frequency region is judged to be a potentially more useful optical nonlinear material than the analogous compound LiGaO2.

Due to its high damage threshold and high conversion efficiency, the HgGa₂S₄ (HGS) nonlinear crystal is particularly suitable for frequency doubling in the 1-10 μm range, as well as for OPO/OPA applications. For a 4 mm long HgGa₂S₄ element, the frequency doubling efficiency for CO₂ laser radiation is approximately 10% (pulse duration of 30 ns, radiation power density of 60 MW/cm²). Although growing large HGS crystals is quite challenging, their high conversion efficiency and broad radiation wavelength tuning range make them a promising competitor to AgGaS₂, AgGaSe₂, ZnGeP₂, and GaSe crystals.

​Potassium Titanyl Arsenate (KTIOAsO4), or KTA, is a nonlinear optical crystal for Optical Parametric Oscillation (OPO) application.
It has good nonlinear optical and electro-optical properties, e.g. significantly reduced absorption in band range of 2.0-5.0 um, broad angular and temperature bandwidth, low dielectric constants.

​Potassium titanyl phosphate is widely used in commercial and military lasers, including laboratory and medical systems, range detectors, lidars, optical communications and industrial laser systems.
KTP is most commonly used for frequency-doubled Nd:YAG and other Nd-doped lasers, especially in low to medium power lasers. So far, the use of KTP for intracavity and extra cavity frequency doubling of Nd-doped lasers has gradually replaced visible-light dye lasers and tunable sapphire lasers. In many industrial studies, this type of laser is widely used as a green light source.

​Bismuth Triborate (BiB3O6 or BIBO) is a newly developed nonlinear optical crystal. It possesses large effective nonlinear coefficient, high damage threshold and inertness with respect to moisture. Its nonlinear coefficient is 3.5-4 times higher than that of LBO, 1.5-2 times higher than that of BBO. It is a promising doubling crystal to produce blue laser. The top-seeded solution growth (TSSG) technique is used at CRYSTRONG for the growth of BIBO single crystals.