Zhanggui Hu

Bi2(IO4)(IO3)3: A New Potential Infrared Nonlinear Optical Material Containing [IO4]3– Anion

A new potential infrared (IR) nonlinear optical (NLO) material Bi(2)(IO(4))(IO(3))(3) was synthesized by hydrothermal method. Bi(2)(IO(4))(IO(3))(3) crystallizes in the chiral orthorhombic space group P2(1)2(1)2(1) (No. 19) with a = 5.6831(11) Å, b = 12.394(3) Å, and c = 16.849(3) Å. It exhibits a three-dimensional framework through a combination of the IO(3), IO(4), BiO(8), and BiO(9) polyhedra and is the first noncentrosymmetric (NCS) structure containing [IO4](3-) anion. Bi(2)(IO(4))(IO(3))(3) has an IR cutoff wavelength of 12.3 μm and belongs to the type 1 phase-matchable class with a moderately large SHG response of 5 × KDP, which is in good agreement with the theoretical calculations.

Growth and nonlinear optical properties of BaAlBO 3 F 2 crystal

BaAlBO3F2 (BABF), a newly developed nonlinear optical (NLO) crystal, was fully investigated for high-power harmonic generation of UV light. This was performed after successfully growing high-quality single crystals in the LiF–B2O3–NaF flux system. Thermal expansion, specific heat, transmittance spectrum, nonlinear optical coefficients, and laser damage threshold were measured. High-power NLO experiments were also conducted for what we believe to be the first time for BABF crystals. Because BABF is absolutely not hygroscopic, the appealing physical, chemical, optical, and NLO properties make BABF a promising NLO crystal for practical application in high-power UV light generation.

266 nm ultraviolet light generation in Ga-doped BaAlBO 3 F 2 crystals.

BaAlBO3F2 (BABF) crystals are a recently developed and promising nonlinear optical material, notably for the third harmonic generation of ultraviolet (UV) light at 355 nm. However, the fourth harmonic generation of UV light at 266 nm has never been obtained by using a BABF crystal due to its relatively small birefringence. We demonstrate that the birefringence of BABF can be effectively increased by doping it with Ga3+. The fourth harmonic generation of UV light at 266 nm was achieved for the first time in a Ga-doped BABF crystal.

Shape-controlled growth and characterization of a large KDP crystal

A shape-controlled KDP (KH2PO4) crystal up to 305 × 302 × 100 mm3 in size and 21.5 kg in weight has been grown rapidly. The morphology of the as-grown crystal which was close to the finished optical elements of a Pockels cell enhanced the crystal yield to nearly 100%. We used a Z-cut point seed and a specially designed crystal holder to adjust the crystal morphology while ensuring sufficient feeding of solute, avoiding friction between the crystal and the platforms, and finally enhancing the crystal yield. The method of transferring the solution from a separate crystallizer for overheating to the crystallizer for crystal growth was used to introduce the seed into the crystallizer without lowering the solutions stability. In order to evaluate the crystal quality under the influence of growth restriction by the platforms, the rocking curves, optical homogeneity, and laser damage threshold of the as-grown crystal in different positions have been studied.

Study on the weak absorption of potassium titanyl phosphate crystals

Potassium titanyl phosphate (KTP) is mostly used in all-solid- state lasers as a good nonlinear optical crystal. Knowledge of variations in the weak absorption of different types of KTP crystals is important for the application. In this study, the flux-grown KTP crystals with titanium from TiO2, TiCl4, and TiðOC4H9Þ4, respectively, and the hydrothermal- grown KTP crystal were investigated. The weak absorption values of the KTP crystals were measured at 1064 nm and 532 nm by photother- mal common-path interferometer. The weak absorption values of four samples were 100 ppm · cm −1 , 800 ppm · cm −1 , 45 ppm · cm −1 , 1064 ppm · cm −1 at 1064 nm, and 2.6 × 10 4 ppm · cm −1 , 1.6× 10 5 ppm · cm −1 , 1.2 × 10 4 ppm · cm −1 , 2.25 × 10 2 ppm · cm −1 at 532 nm, respectively. The results showed that the weak absorption values of the flux-grown KTP with titanium from TiðOC4H9Þ 4 and the hydrothermal- grown KTP were low values at 1064 nm. In addition, the weak absorption value of the hydrothermal-grown KTP was at least two orders of magnitude lower than that of the flux-grown KTP at 532 nm. From the results, we con- cluded that the KTP grown by titanium from TiðOC4H9Þ4 represented a better quality than the other two flux-grown KTP crystals. The quality of the hydrothermal-grown KTP was obviously better than the flux-grown KTP.

Influence of A-site cations on germanium iodates as mid-IR nonlinear optical materials: A2Ge(IO3)6 (A = Li, K, Rb and Cs) and BaGe(IO3)6·H2O

In this work, a series of germanium iodates with different A-site cations A2Ge(IO3)6 (A = Li, K, Rb and Cs) and BaGe(IO3)6·H2O have been synthesized and further explored as potential mid-IR nonlinear optical (NLO) materials. It is found that the change of the alkali metal ionic radius from Li+ to K+–Cs+ greatly affects the coordination environment that alters the arrangement of polar [IO3]− anionic groups, thus leading to the crystal structural shift from the noncentrosymmetric (NCS) structure of P63 for Li2Ge(IO3)6 to the centrosymmetric (CS) structure of R for A2Ge(IO3)6 (A = K, Rb and Cs). The substitution of two alkali ions by one alkali-earth metal ion of Ba2+ with different ionic radius and valence produces another germanium iodate, BaGe(IO3)6·H2O, which contains a crystal water molecule to participate in coordination and crystallizes in another polar space group R3. Li2Ge(IO3)6 and BaGe(IO3)6·H2O with the NCS structure possess second-order NLO properties, in which Li2Ge(IO3)6 shows a very strong second harmonic generation (SHG) response of about 20 × KDP (KH2PO4) under laser irradiation at 1064 nm and 1.95 × KTP (KTiOPO4) under laser irradiation at 1950 nm with type-I phase-matching characteristics, while BaGe(IO3)6·H2O only exhibits a moderate SHG response of 1.5 × KDP with non-phase-matching characteristics. Especially, Li2Ge(IO3)6 shows a large bandgap of 3.60 eV with a laser damage threshold over 12 times that of AgGaS2 under the same measured conditions, and it also shows a relatively wide mid-IR transparent window up to 10 μm and a good crystal growth habit with a high decomposition temperature over 360 °C, suggesting that it will be a promising mid-IR NLO crystal.

Flux growth and 266 nm generation of a GdAl3(BO3)4 crystal

The study focused on optimization of the growing conditions of GdAl3(BO3)4 (GAB). Using Al2O3–B2O3–Li2O–NaF as a flux, inclusion-free GAB crystals with sizes up to 18 × 18 × 35 mm3 were successfully grown using the top-seeded solution growth technique. The preparation of the starting materials, flux selection and optimization of the growing parameters are discussed in the study. Laser radiation at 266 nm was generated for the first time by a type I phase-matching GAB crystal.

A new cerium iodate infrared nonlinear optical material with a large second-harmonic generation response

A new rare earth ternary iodate, Ce2I6O18, has been synthesized by a high temperature hydrothermal method with homemade alloy reactor equipment. It crystallizes in the monoclinic system space group P21 with a = 8.7252(2) A, b = 7.0474(1) A, c = 13.096(3) A, β = 90.81(0)°, Z = 2, and V = 805.2(3) A3. The material exhibits a three dimensional structure consisting of unlimited extending CeO9 polyhedrons and IO3 triangular pyramidal bilayers connected by I⋯O long bonds. The electronic band structure and optical properties of Ce2I6O18 were studied. It belongs to the type I phase-matchable class with an IR cutoff wavelength of 12.2 μm and second-harmonic generation (SHG) response of about 9 × KH2PO4 (KDP).

Polarization-Dependent Third-Order Optical Nonlinearity of

We investigated the third-order optical nonlinearity of a new nonlinear optical crystal BaAlBO₃F₂ (BABF) using Z-scan technique with a picosecond 532-nm laser. Polarization-dependent nonlinear refractive index γ of the BABF crystal was measured with an a-cut sample and a sample cut along the type I phase-matching angle for third-harmonic-generation of lasers at 1064 nm (THG-cut). Anisotropy was observed with positive γ values in the range of 10^-16 cm²/W, indicating self-focusing Kerr effects. The measurements agreed well with the theoretical prediction. The corresponding third-order nonlinear optical susceptibility χ_eff⁽³⁾ was estimated to be ~ 10^-14 esu.