Vanadium iodate second-order nonlinear optical crystal material as well as preparation and application thereof

Abstract

The invention relates to a vanadium iodate second-order nonlinear optical crystal material and preparation and application thereof, the chemical formula of the vanadium iodate second-order nonlinear optical crystal material is VO2 (H2O) (IO3), the molecular weight is 275.86, the vanadium iodate second-order nonlinear optical crystal material belongs to an orthorhombic system, the space group of the vanadium iodate second-order nonlinear optical crystal material is Pca21, the cell parameter is # imgabs 0 # alpha = beta = gamma = 90 degrees, Z = 4, and the cell volume is # imgabs 1 #. The frequency doubling intensity of the powder under the irradiation of laser of 1200 nm is about 18.0 times of that of monopotassium phosphate crystal (KDP), the frequency doubling intensity of the powder under the irradiation of laser of 2100 nm is about 1.5 times of that of potassium titanyl phosphate (KTP), and phase matching can be achieved. In addition, the vanadium iodate crystal material also has large birefringence, and the birefringence reaches 0.184 at 546 nm. The research result shows that the crystal has wide application prospects in the fields of laser frequency conversion, photoelectric modulation, laser signal holographic storage and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical crystal materials, and relates to a vanadium iodate second-order nonlinear optical crystal material and its preparation and application. Background Art

[0002] Nonlinear optical crystal materials with second harmonic generation (SHG) properties play a crucial role in modern laser science and technology, which can be attributed to their laser frequency conversion ability that can be applied to expand the output spectral range of laser light sources. As a prerequisite for second-order nonlinear optical (NLO) crystal materials, they must have a crystallographically non-centrosymmetric (NCS) structure, and the presence of asymmetric structural units in the molecular structure may promote the formation of a macroscopic NCS structure. Currently, commercially available nonlinear optical materials include β-barium metaborate (BBO), lithium metaborate (LBO), potassium dihydrogen phosphate (KDP), potassium titanyl phosphate (KTP), etc. In the past two decades, although great efforts and explorations have been made in establishing the correlation between crystal structure and SHG properties, due to the unfavorable dipole-dipole interactions and / or steric effects in inorganic crystal materials that are conducive to the formation of a centrosymmetric (CS) structure rather than an NCS structure, it is still very difficult to custom-synthesize crystals with an NCS structure. Therefore, developing new NCS materials with strong SHG response is a major challenge in the field of inorganic optical functional materials at present. Summary of the Invention

[0003] The purpose of the present invention is to provide a vanadium iodate second-order nonlinear optical crystal material and its preparation and application. This crystal exhibits a huge SHG response. Under 1200 nm laser irradiation, the powder second harmonic generation intensity is about 18.0 times that of the reference second harmonic generation crystal potassium dihydrogen phosphate crystal (KDP). Under 2100 nm laser irradiation, the powder second harmonic generation intensity is about 1.5 times that of the infrared reference second harmonic generation crystal potassium titanyl phosphate (KTP), and it can achieve phase matching, indicating that this crystal is a second-order nonlinear optical crystal material with important potential application value.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] One of the technical solutions of the present invention is to provide a vanadium iodate second-order nonlinear optical crystal material, whose chemical formula is VO 2 (H 2 O)(IO 3 ), and the molecular weight is 275.86.

[0006] Furthermore, this crystal material belongs to the orthorhombic system, its space group is Pca2 1 , the unit cell parameters are a = α = β = γ = 90°, Z = 4, and the unit cell volume is

[0007] Furthermore, the unit cell parameters of the crystal material are α = β = γ = 90°, Z = 4, and the unit cell volume is

[0008] The crystal structure of the vanadium iodine oxide compound of the present invention can be described as follows: In the vanadium iodine oxygen crystal, the six-coordinate V 5+ cation is connected to six oxygen atoms (one terminal oxygen atom, two bridging oxygen atoms, two oxygen atoms from different chelating mode iodate groups, and one oxygen atom from a water molecule) to form a [V(1)O 5 (H 2 O)] 5- octahedron, where the bond length of the vanadium-oxygen bond is Each [V(1)O 5 (H 2 O)] 5- octahedron is connected to an adjacent [V(1)O 5 (H 2 O)] 5- octahedron through the shared O(3) and O(5) atoms to form a zigzag chain [VO 2 (H 2 O)(IO 3 )] ∞ . The I 5+ cation coordinates with three O atoms to form a trigonal pyramid geometry (where the O-I-O angle is 96.26(14)-100.41(11)°, and the I-O bond length is [I(1)O 3 - groups are bonded to both sides of the zigzag chain in a bidentate bridging manner by edge-sharing oxygen atom O(1). Not only is there a weak hydrogen bond between the zigzag chain and the coordinated H 2 O molecule (O6-H6A … O2 and O6-H6A … O1), but there is also a weak hydrogen bond between adjacent zigzag chains (O6-H6B … O1). This connection mode through intermolecular hydrogen bonds results in the formation of a two-dimensional (2D) [VO 2 (H 2 O)(IO 3 )] ∞ layer in the ac plane. Interestingly, the layers are stacked parallel to each other, in an -AAAA- sequence along the c-axis, and through weak I(1) … ​Connected by intermolecular interactions of O(2), a pseudo-three-dimensional (3D) framework structure along the ab plane is generally formed.

[0009] The second technical solution of the present invention provides a preparation method of a vanadium iodate second-order nonlinear optical crystal material, which is characterized in that a vanadium source, an iodine source, a sulfur source and water are first mixed to form an initial mixed raw material. The sulfur source serves as a mineralizer and provides an acidic environment, which is more conducive to the growth of the crystal material. Then, it is placed under sealed hydrothermal conditions for reaction crystallization to obtain the target product.

[0010] Further, the vanadium source is vanadium pentoxide; the iodine source is iodic acid; the sulfur source is sulfuric acid.

[0011] Further, in the initial mixed raw material, the molar ratio of vanadium element, iodine element and sulfur element is 1:(0.5 - 30):(0.5 - 50).

[0012] Further, in the initial mixed raw material, the molar ratio of vanadium element, iodine element and sulfur element is 1:(1 - 20):(1 - 20).

[0013] Further, the temperature of the crystallization hydrothermal reaction is 150 - 230 °C, and the crystallization time is not less than 24 h. Preferably, the temperature of the crystallization hydrothermal reaction is 180 - 230 °C, and the crystallization time is not less than 48 h. At the same time, after crystallization is completed, it is cooled to room temperature at a cooling rate of 0.5 - 15 °C / h. Preferably, the cooling rate is 0.5 - 6 °C / h.

[0014] The third technical solution of the present invention provides an application of a vanadium iodate second-order nonlinear optical crystal material. This crystal material is used for visible and mid-infrared laser frequency doubling output. Preferably, it is used for doubling the output of visible light and infrared laser beams as second harmonic waves.

[0015] Further, this crystal material is used in frequency doublers, optical parametric oscillators, optical parametric amplifiers and photoelectric rectifiers.

[0016] The crystal material of the present invention is applied to a laser frequency converter. This vanadium iodine oxygen crystal material has a huge frequency doubling effect. Under 1200 nm laser irradiation, its powder frequency doubling effect is about 18.0 times that of the reference frequency doubling crystal KDP. Under 2100 nm laser irradiation, the powder frequency doubling intensity is about 1.5 times that of the infrared reference frequency doubling crystal KTP, and it is type I phase matching. In addition, the band gap of this crystal material is 2.81 eV, and the thermal stability temperature is 240 °C. Therefore, this crystal material has broad application prospects in the field of second-order nonlinear optics.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) The present invention provides a new inorganic crystal material, vanadium iodine oxide compound, which has a huge second harmonic generation (SHG) effect. Under 1200 nm laser irradiation, its SHG intensity is about 18.0 times that of KDP crystal, and under 2100 nm laser irradiation, the powder SHG intensity is about 1.5 times that of KTP. Its birefringence value measured under 546 nm laser is 0.184, enabling type-I phase matching. In addition, the optical band gap of this crystal material is 2.81 eV, and the thermal stability temperature reaches 240 °C, showing broad application prospects in the fields of laser frequency conversion, electro-optical modulation, laser signal holographic storage, etc.;

[0019] (2) The present invention provides a preparation method of the vanadium iodine oxygen crystal material. By using the hydrothermal synthesis method with mild reaction conditions, high-purity crystalline samples can be obtained in high yield through hydrothermal crystallization at a temperature of 150 - 230 °C. The method is simple and the conditions are mild, which is conducive to large-scale industrial production;

[0020] (3) The vanadium iodine oxygen crystal material of the present invention can be applied to a laser frequency converter, which can be used to output visible and infrared laser beams with second harmonic frequency. Description of the Drawings

[0021] Figure 1 is the crystal structure schematic diagram of vanadium iodine oxygen;

[0022] Figure 2 is the comparison of X-ray diffraction patterns;

[0023] Figure 3 is the ultraviolet-visible-near-infrared absorption spectrum of sample 1#;

[0024] Figure 4 is the infrared spectrum (2.5 - 25 μm) spectrum of sample 1#;

[0025] Figure 5 is the thermogravimetric analysis pattern of sample 1#;

[0026] Figure 6 is the second harmonic signal diagram of sample 1# and KDP samples with sizes in the range of 200 - 280 μm;

[0027] Figure 7 is the second harmonic phase matching diagram of sample 1# and KDP samples at 1200 nm band;

[0028] Figure 8 is the second harmonic signal diagram of sample 1# and KTP samples with sizes in the range of 200 - 280 μm;

[0029] Figure 9 is the second harmonic phase matching diagram of sample 1# and KTP samples at 2.1 μm band;

[0030] Figure 10 It is the birefringence test chart of sample 1# at the 546 nm wavelength band. Specific implementation manners

[0031] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0032] In the following embodiments, unless otherwise specified for raw material products or process technologies, it means that they are all conventional commercially available products or conventional processing technologies in the art.

[0033] Example 1:

[0034] Hydrothermal synthesis of samples

[0035] A vanadium source, an iodine source, a sulfur source (using 98 wt% sulfuric acid) and water are mixed in a certain proportion to form a starting material, which is sealed in a hydrothermal reaction kettle with a polytetrafluoroethylene liner. The temperature is raised to the crystallization temperature, and after maintaining a constant temperature for a period of time, the temperature of the reaction system is slowly lowered to room temperature at a certain rate, followed by filtration and washing to obtain yellow transparent block-shaped vanadium iodine oxide crystals.

[0036] The relationship between the types and ratios of raw materials, the crystallization temperature, the crystallization time in the initial mixture and the sample numbers is shown in Table 1.

[0037] Table 1 Correspondence between samples and raw materials used and synthesis conditions

[0038]

[0039]

[0040] Example 2:

[0041] Crystal structure analysis

[0042] Single crystal X-ray diffraction and powder X-ray diffraction methods are used to analyze the structures of samples 1# to 6#.

[0043] Among them, the single crystal X-ray diffraction test is carried out on a D8 VENTURE CMOS X-type X-ray single crystal diffractometer of Bruker Corporation in Germany. The crystal size is 0.12×0.07×0.06 mm 3 ; the data collection temperature is 293 K, and the diffraction light source is graphite-monochromatized Mo-Kα rays with a wavelength of The scanning mode is ω; the data is processed by the Multi-Scan method for absorption correction. The structure analysis is completed using the SHELXTL-97 program package; the positions of the heavy atoms are determined by the direct method, and the coordinates of the remaining atoms are obtained by the difference Fourier synthesis method; the coordinates of all atoms and the anisotropic thermal parameters are refined by the full-matrix least-squares method based on F 2 The full matrix least-squares method based on F

[0044] The powder X-ray diffraction test was carried out on a Bruker D8 X-ray powder diffractometer produced by Bruker Company, Germany. The test conditions were a fixed target monochromatic light source Cu-Kα, with a wavelength of The voltage and current were 40 kV / 20 A, and the slits DivSlit / RecSlit / SctSlit were 2.00 deg / 0.3 mm / 2.00 deg respectively. The scanning range was 5–70°, and the scanning step was 0.02°.

[0045] Among them, the single crystal X-ray diffraction test results showed that samples 1# to 6# had the same chemical structural formula and crystal structure. The chemical formula was VO 2 (H 2 O)(IO 3 ), with a molecular weight of 275.86, belonging to the orthorhombic system, and its space group was Pca2 1 , and the unit cell parameters were α = β = γ = 90°, Z = 4, and the unit cell volume was

[0046] Taking sample 1# as a typical representative, its crystal structure data was α = β = γ = 90°, Z = 4, and the unit cell volume was Its crystal structure was as shown in Figure 1 .

[0047] The powder X-ray diffraction test results showed that on the XRD spectra of samples 1# to 6#, the peak positions of each sample were basically the same, and the peak intensities were slightly different.

[0048] Taking sample 1# as a typical representative, as shown in Figure 2 , the obtained spectrum of sample 1# after being ground into powder and tested by X-ray diffraction was consistent with the X-ray diffraction spectrum simulated based on the crystal structure analyzed by its single crystal X-ray diffraction in terms of peak position and peak intensity, indicating that the obtained samples had a high purity.

[0049] Example 3:

[0050] Ultraviolet transmission spectrum test

[0051] The ultraviolet transmission spectrum test of Sample 1# was carried out on an Agilent Cary 5000 ultraviolet-visible-near-infrared spectrophotometer. The results are as Figure 3 shown. The ultraviolet absorption cut-off edge of this compound is 442 nm, and the corresponding optical band gap is 2.81 eV.

[0052] Example 4:

[0053] Infrared spectrum test

[0054] The infrared spectrum test of Sample 1# was carried out on a Nicolet iS10 Fourier transform infrared spectrometer of Thermo Fisher Scientific Inc. The results are as Figure 4 shown. The infrared absorption peaks at 870 cm -1 , 715 cm -1 and 686 cm -1 are attributed to the stretching vibration peaks of I-O bonds. The O-H stretching vibration peak and the in-plane bending vibration peak are located at 3496 cm -1 , 3371 cm -1 and 1597 cm -1 respectively. These infrared characteristic peaks are consistent with the single crystal structure.

[0055] Example 5:

[0056] Thermogravimetric test

[0057] The thermogravimetric test of Sample 1# was carried out on a Netzsch STA 409PC thermogravimetric analyzer of Netzsch Gerätebau GmbH. The results are as Figure 5 shown. It can be seen from Figure 5 that this compound can be stable up to 240 °C and has good thermal stability.

[0058] Example 6:

[0059] Second harmonic generation test experiment and results

[0060] The frequency doubling test experiment of Sample 1 is as follows: The laser with a wavelength of 1200 nm generated by a tunable laser test system (Amplitude, HorizonII) is used as the fundamental frequency light to irradiate the crystal powder to be tested. A photomultiplier tube is used to detect the generated second harmonic, and an oscilloscope is used to display the harmonic intensity. The crystal sample is ground separately with the reference frequency doubling crystals KDP and KTP, and crystals with different particle sizes are separated by a standard sieve. The particle size ranges are less than 26, 26 - 50, 50 - 74, 74 - 105, 105 - 150, 150 - 200, and 200 - 280 μm respectively. Observe the trend of the frequency doubling signal intensity changing with the particle size to judge whether phase matching can be achieved. Under the same test conditions, compare the intensities of the second harmonics generated by the sample with the reference frequency doubling crystals KDP and KTP to obtain the relative magnitude of the frequency doubling effect of the sample.

[0061] The test results show that the vanadium iodine oxide crystal compound has a large frequency doubling effect. Under the irradiation of a 1200 nm wavelength laser, the frequency doubling signal intensity is 18.0 times that of the reference frequency doubling crystal KDP (as Figure 6 ), and type I phase matching can be achieved (as Figure 7 ); under the irradiation of a 2100 nm wavelength laser, the frequency doubling signal intensity is 1.5 times that of the reference infrared frequency doubling crystal KTP (as Figure 8 ), and type I phase matching can also be achieved (as Figure 9 ).

[0062] Example 7:

[0063] Birefringence test experiment and results

[0064] The birefringence of the crystal VO 2 (H 2 O)(IO 3 ) was tested by a polarized light microscope (ZEISSAxio Scope.A1) equipped with a Berek compensator. The light source wavelength was 546 nanometers. The birefringence was calculated according to the following formula:

[0065] ΔR = |Ne - No| × T = Δn × T

[0066] where ΔR represents the optical path difference, Δn represents the birefringence, and T is the crystal thickness. The positive and negative rotations of the compensation produce a relative delay. The boundaries between the first-order, second-order, and third-order interference colors are clear, so the relative error is small. To improve the accuracy of the birefringence, we selected transparent flaky VO 2 (H 2 O)(IO 3 ) crystals for measurement.

[0067] The test results show that the compound vanadium iodine oxide crystal exhibits strong optical anisotropy, reaching 0.184 at 546 nm (as Figure 10 ), which is better than the birefringence efficiency of most commonly used commercial birefringent crystals.

[0068] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A vanadium iodate second-order nonlinear optical crystal material, characterized in that: Its chemical formula is VO2(H2O)(IO3), its molecular weight is 275.86, it belongs to the orthorhombic system, its space group is Pca21, and its unit cell parameters are α=β=γ=90°, Z=4, the unit cell volume is 2. The vanadium iodate second-order nonlinear optical crystal material according to claim 1, characterized in that: The crystal material belongs to the orthorhombic system, its space group is Pca21, and the unit cell parameters are α=β=γ=90°, Z=4, the unit cell volume is 3. The vanadium iodate second-order nonlinear optical crystal material according to claim 1, characterized in that: The unit cell parameters of the crystal material are α=β=γ=90°, Z=4, the unit cell volume is 4. The method for preparing the vanadium iodate second-order nonlinear optical crystal material according to any one of claims 1 to 3, characterized in that: Firstly, a vanadium source, an iodine source, a sulfur source and water are mixed to form an initial mixed raw material, and then the raw material is placed under sealed hydrothermal conditions for reaction and crystallization to obtain the target product.

5. The method for preparing a vanadium iodate second-order nonlinear optical crystal material according to claim 4, characterized in that: The vanadium source is vanadium pentoxide; the iodine source is iodic acid; and the sulfur source is sulfuric acid.

6. The method for preparing a vanadium iodate second-order nonlinear optical crystal material according to claim 4, characterized in that: In the initial mixed raw material, the molar ratio of vanadium element, iodine element and sulfur element is 1: (0.5-30): (0.5-50).

7. The method for preparing a vanadium iodate second-order nonlinear optical crystal material according to claim 4, characterized in that: In the initial mixed raw materials, the molar ratio of vanadium element, iodine element and sulfur element is 1:(1-20):(1-20).

8. The method for preparing a vanadium iodate second-order nonlinear optical crystal material according to claim 4, characterized in that: The crystallization temperature is 150-230°C, and the crystallization time is not less than 24 hours.

9. The use of the vanadium iodate second-order nonlinear optical crystal material according to any one of claims 1 to 3, characterized in that: The crystal material is used for visible-mid-infrared laser frequency doubling output.

10. The use of the vanadium iodate second-order nonlinear optical crystal material according to claim 9, characterized in that: The crystal material is used in frequency doubling generators, optical parametric oscillators, optical parametric amplifiers and photoelectric rectifiers.

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